WO2025219462A1

WO2025219462A1 - Inductive heating device comprising a flat induction coil

Info

Publication number: WO2025219462A1
Application number: PCT/EP2025/060522
Authority: WO
Inventors: Larry Sacha Baudet; Oleg Mironov; Johannes Petrus Maria Pijnenburg; Enrico Stura
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2024-04-16
Filing date: 2025-04-16
Publication date: 2025-10-23
Anticipated expiration: 2026-10-16

Abstract

There is provided an inductive heating device (100) for aerosol-generation. The inductive heating device (100) comprises a heater assembly defining a cavity (68) having an internal surface for receiving at least a portion of an aerosol-forming insert (300) comprising an aerosol-forming substrate and a susceptor. The heater assembly comprising an induction coil (16) having a magnetic axis and arranged to surround at least a portion of the cavity (68); wherein a wire material (6) forming the induction coil (16) has a cross-section comprising a main portion, the main portion having a longitudinal extension in a direction of the magnetic axis and a lateral extension perpendicular to the magnetic axis, which longitudinal extension is longer than the lateral extension of the main portion, wherein the wire material (6) comprises an electrically conductive coating (8).

Description

INDUCTIVE HEATING DEVICE COMPRISING A FLAT INDUCTION COIL

The present disclosure relates to an inductive heating device and system for aerosol generation, a heater assembly for aerosol-generation, an inductor assembly for aerosolgeneration, and associated methods of manufacture of the inductor assembly, the heater assembly, and the aerosol-generating device and system.

It is known to evolve an aerosol from an aerosol-forming substrate of an aerosolgenerating article by the application of heat to the substrate, without burning or combustion of the substrate. The aerosol-generating article may be cylindrical, like a cigarette, and the aerosol-forming substrate may comprise tobacco material. It is known to use an aerosolgenerating device to apply heat to such an aerosol-generating article to heat the aerosolforming substrate of the article. In some examples, the aerosol-generating article is received within a cavity of the aerosol-generating device. It is known to use a heat source that is external to the aerosol-generating article, or use a heat source located within the interior of the aerosol-forming substrate.

However, the componentry which surrounds the cavity of the aerosol-generating device in order to heat the aerosol-generating article may be complex.

Furthermore, the componentry which surrounds the cavity of the aerosol-generating device may be subject to high temperatures from within the cavity. In order to reduce the chance of failure of the componentry, the componentry may comprise heat-resistant materials. However, heat-resistant materials can be expensive, and so are undesirable.

It is therefore desired to provide an aerosol-generating device or componentry for an aerosolgenerating device which simplifies manufacturing and reduces manufacturing time, whilst reducing the cost of manufacture of the aerosol-generating device.

Additionally, in electrically heatable devices, an ongoing restraint is the limited energy available by a battery provided in the device. The trend to a miniaturization of these devices put additional strain on these power supplies. For optimization of the use of energy inductive heating has been proposed. Inductive heating, facilitates better energy transfer into a to-be- heated part of the device and better energy conversion into heat may be achieved. However, miniaturized electric smoking devices still have to be recharged often, which may be inconvenient for a user. Therefore, there is a need for improved inductive heating devices for aerosol-generation. Especially, there is a need for such devices with respect to energy efficiency.

According to the present disclosure, there is provided an inductive heating device for an aerosol-generation. The device may comprise a device housing comprising a heater assembly. The heater assembly may defining a cavity having an internal surface for receiving at least a portion of an aerosol-forming insert. The aerosol-forming insert may comprise an aerosol-forming substrate and a susceptor. The device may further comprise an induction coil. The induction coil may have a magnetic axis and be arranged within the device housing such as to surround at least a portion of the cavity. A wire material forming the induction coil may have a cross-section comprising a main portion. The main portion may have a longitudinal extension in a direction of the magnetic axis and a lateral extension perpendicular to the magnetic axis. The longitudinal extension may be longer than the lateral extension of the main portion. The wire material may comprise an electrically conductive coating.

According to a first aspect, there is provided an inductive heating device for an aerosolgeneration. The device comprises a device housing comprising a heater assembly. The heater assembly defines a cavity having an internal surface for receiving at least a portion of an aerosol-forming insert comprising an aerosol-forming substrate and a susceptor. The device further comprises an induction coil. The induction coil has a magnetic axis and be arranged within the device housing such as to surround at least a portion of the cavity. A wire material forming the induction coil has a cross-section comprising a main portion. The main portion has a longitudinal extension in a direction of the magnetic axis and a lateral extension perpendicular to the magnetic axis. The longitudinal extension is longer than the lateral extension of the main portion. The wire material comprises an electrically conductive coating.

Simply spoken, the form of the wire material has an elongate or flattened cross-section, entirely or at least in the main portion, compared to a conventional helical induction coil formed by a wire of circular cross-section. Thus, the wire material in the main portion extends along the magnetic axis of the coil and to a smaller extent into the radial direction. By this measure, energy loss in the induction coil may be lessened. Especially, capacitance loss may be lessened. Capacitance of two electrically charged objects is directly proportional to the surface area of two neighbouring surfaces - here the sides of neighbouring windings or turns that are facing each other in the induction coil. Thus, capacitance loss is lessened by reducing the extension of a winding in the perpendicular direction.

The induction coil being arranged in the device housing, surrounding the cavity is favorable, since the induction coil may be arranged such as to not be in contact with the cavity or any material inserted into the cavity. The induction coil may completely be embedded in the housing, for example moulded into a housing material. The induction coil is protected from external influences and may be fixedly mounted in the housing. In addition, a cavity may be completely empty, when no insert is accommodated in the cavity. This may not only allow and facilitate the cleaning of the cavity but of the entire device without the risk of damaging parts of the device. Also no elements are present in the cavity that might get damaged upon insertion and removal of an insert into and from the cavity, or that might need to be cleaned. The electrically conductive coating has a conductivity of at least 2 S/m at 20 degrees Celsius, and preferably greater than 1 x10⁶ S/m at 20 degrees Celsius. In some examples, the electrically conductive coating may have a higher electrical conductivity than the wire material. At high operating frequencies, the skin effect reduces the effective cross-section of the induction coil, and so increases its effective resistance. By providing an induction coil having a more electrically conductive coating around the wire material, the effective resistance of the induction coil is reduced, thereby reducing resistive losses in the inductive heating device.

In some examples, the electrically conductive coating may have a higher resistance to corrosion or oxidation than the wire material. In addition to protecting the wire material of the induction coil in use from the effect of corrosion or oxidation, such coatings may simplify the process for manufacturing the induction coil. Specifically, mitigating against oxidation of the induction coil maintains the efficacy of the induction coil soldering process. Where oxidation of the induction coil is prevented, the induction coil can be soldered using a tin paste.

In some examples, the electrically conductive coating may have a maximum thickness within the range of 0.5-100pm, preferably 0.5-50pm, more preferably 0.5-30pm, more preferably 0.5-10pm, more preferably, 0.5-5pm. In some examples, the electrically conductive coating may have a maximum thickness of around 1 pm. For aerosol-generating devices configured to provide both external heating (restive or inductive) in addition to internal inductive heating, there is limited space for the heating assembly to fit within existing device housings in order to manufacture the device using existing manufacturing processes. Therefore, it is important that any electrically conductive coating applied to the wire material of the induction coil does not add significantly to the thickness of the induction coil.

In examples in which the electrically conductive coating has a higher conductivity than the wire material, it may be advantageous for the thickness of the electrically conductive to match or exceed the maximum skin depth in the induction coil at the operating frequency of the inductive heating device. This will ensure that the highest current density occurs within the electrically conductive coating, which will reduce resistive losses in the induction coil.

In some examples, the main portion may comprise two opposing longitudinal ends and two opposing lateral ends. In an example, the thickness of the electrically conductive coating around regions of the main portion wherein the longitudinal ends meet the lateral ends may be greater than the thickness of the electrically conductive coating at other regions of the main portion. In other examples, the thickness of the electrically conductive coating is greater along the longitudinal ends than on the lateral ends of the main portion. For induction coils having non-circular cross-sections, the skin depth around the induction coil varies leading to different current densities for the same depth around a cross-section of the induction coil. It may therefore be advantageous to provide a varying thickness electrically conductive coating around the cross-section of the wire material based on the geometry of the wire material, such that a thicker electrically conductive coating is provided around regions in which a higher current density is anticipated. In some examples, there is no electrically conductive coating on the lateral ends of the main portion. This may minimize the thickness of the induction coil while reducing resistive losses in the induction coil where the current density is greatest.

In some examples, the electrically conductive coating comprises at least one of silver or gold. Such materials may have greater electrical conductivity and/or resistance to corrosion/ oxidation than typical induction coil wire materials (such as copper).

In some examples, the main portion forms the entire cross-section of the wire material. In these examples, the induction coil is helically formed by a wire material having an elongate cross section, thus forms a helical flat coil (flat with respect to the form of the wire material) . Such induction coils are easy to manufacture. Next to reduced energy loss, they have the additional advantage to minimize an outer diameter of the induction coil. This allows to minimize the device. The space gained by providing a flat coil may also be used for the provision of magnetic shielding without having to change the size of the device or even to additionally minimizing the device. In some examples, the main portion may have the form of a rectangle.

In some examples, the cross-section of the wire material further comprises a secondary portion, the secondary portion having a longitudinal extension in the direction perpendicular to the magnetic axis and a lateral extension in the direction of the magnetic axis, which longitudinal extension is longer than a lateral extension of the secondary portion. The lateral extension of the secondary portion is always smaller than the longitudinal extension of the main portion and the longitudinal extension of the secondary portion is always larger than the lateral extension of the main portion. By this, a cross section of a wire material may be kept large by still reducing energy loss in the induction coil. Capacitance is also inverse proportional to the distance of neighbouring surfaces. Thus, a capacitance may be made smaller by increasing the distance between neighbouring surfaces. Preferably, an induction coil is manufactured from a wire material homogeneous in size such that the windings of the induction coil are substantially identical. If the wire material is provided with a secondary portion with enlarged extension in the radial direction, these secondary portions of the individual windings are distanced from each other. They are distanced from each other not only by the distance between neighbouring windings as in conventional induction coils but also by the length of the longitudinal extension of the main portion. The provision of a secondary portion may also provide additional space between the induction coil and an outer wall of the device housing or also between individual windings. In this space gained by miniaturizing the coil dimensions, for example a shielding material may be arranged. In some examples, the cross section of a wire material having a main portion and a secondary portion is L-shaped. In another example, the cross section of a wire material may be a T-shape. Therein, the T is arranged in an inversed manner and the head of the T forms the main portion and is arranged parallel to the longitudinal axis of the cavity.

In another example, the cross section is a triangle, wherein a basis of the triangle is arranged parallel to the magnetic axis of the induction coil and parallel to the longitudinal axis of the cavity. The form of induction coils according to the invention may generally be defined by having a cross section having a maximum longitudinal extension forming one side of the cross-section. Therein, the wire material is arranged such that the maximum longitudinal extension of the cross section of the wire material extends parallel to the magnetic axis of the induction coil. Therein, the wire material also surrounds the cavity such that the maximum longitudinal extension of the cross section of the wire material is arranged most proximate to the cavity. Any further longitudinal extension of the cross section is equal to, for example in flat coils, or smaller, for example in triangularly shaped induction coils, than the maximum longitudinal extension.

Preferably, the induction coil is arranged close to the cavity in order to be close to a susceptor inserted into the cavity to be heated by the electromagnetic field generated by the induction coil. Thus, if the cross-section of the wire material of the induction coil comprises a secondary portion, wherein a longitudinal extension of the secondary portion exceeds the lateral extension of the main portion of the cross-section, the secondary portion preferably extends into an outward radial direction of the induction coil. By this, it may be guaranteed that the main portion is the portion of the cross-section closest to the cavity.

In some examples, the induction coil comprises three to five windings. In these examples, preferably the cross-section of the wire material, or the main portion thereof, respectively, forms a flat rectangle. By this, an induction coil of sufficient length may be manufactured in a very efficient manner.

In some examples, the device further comprises a magnetic shield provided between an outer wall of the device housing and the induction coil. A magnetic shield provided outside of the induction coil may minimize the electro-magnetic field reaching an exterior of the device. Preferably, a magnetic shield surrounds the induction coil. Such a shield may be achieved by the choice of the material of the device housing itself. A magnetic shield may for example also be provided in the form of a sheet material or an inner coating of the outer wall of the device housing. A shield may for example also be a double or multiple layer of shield material, for example mu-metal, to improve the shielding effect. Preferably, the material of a shield is of high magnetic permeability and may be of ferromagnetic material. A magnetic shield material may also be arranged between individual windings of the induction coil. Preferably, the shield material is then provided - if present - between secondary portions of the cross-section of the wire material. By this, space between the secondary portions may be used for magnetic shielding. Preferably, shield material provided between windings is of particulate nature. In some examples, the magnetic shield may also have the function of a magnetic concentrator, thus attracting and directing the magnetic field. Such a field concentrator may be provided in combination with, in addition to or separate from a magnetic shielding as described above.

In some examples, a circumferential portion of the inner surface of the cavity and the induction coil are cylindrical shape. In such an arrangement, the magnetic field distribution is basically homogeneous inside the cavity. Thus, a regular or symmetric heating of the aerosolforming insert accommodated in the cavity may be achieved, depending on the arrangement of the susceptor. In addition, cleaning of a cylindrical cavity is facilitated since no or only few edges are present where dirt or remainders may get stuck.

In some examples, the heater assembly of the induction heating device may comprise a jacket defining a cavity for receiving at least a portion of an aerosol-generating article. In such examples, the inductor assembly may comprise a sleeve at least partially surrounding the jacket. The induction coil may be coupled to the sleeve.

Advantageously, such a heater assembly allows for modularity during the manufacturing and design process, as different specifications of jackets may be received in different specifications of sleeve in order to adapt to a preferred aerosol-generating article. Therefore, aerosol-generating devices comprising such a heater assembly may be more straightforward to adapt and achieve better aerosol characteristics from a different specification aerosolgenerating article. Furthermore, this assembly allows for the jacket to be made from a different material to that of the sleeve. The heater assembly may comprise components for connecting the heater assembly to an induction heating device. The shape of such connecting componentry may be complex and moulded into shape to facilitate connecting and securing the heater assembly to an induction heating device. In contrast, the jacket defines the cavity for receiving at least a portion of an aerosol-generating article (or insert), and can be relatively thin with a smooth interior surface to transfer heat to an aerosolgenerating article. As the jacket defines the cavity for receiving at least a portion of an aerosol-generating article, the jacket is exposed to higher temperatures during than the sleeve. Therefore the sleeve need not be made from more expensive heat-resistant materials, resulting in a more cost-efficient heater assembly, and resulting in more costefficient aerosol-generating devices comprising such a heater assembly.

The aerosol-generating article may comprise an aerosol-forming substrate. Preferably, the aerosol-forming substrate is a solid aerosol-forming substrate. However, the aerosolforming substrate may comprise both solid and liquid components. The jacket may comprise a jacket body and a jacket heating element. Advantageously, the jacket heating element may be configured to externally heat the aerosol-forming substrate of the aerosol-generating article. In particular, the jacket heating element may be configured to heat a periphery of the cavity. When an aerosol-generating article is received within the cavity, the jacket heating element may be configured to heat an external portion of the aerosol-forming substrate. Advantageously, if the induction coil is configured to heat an internal portion of the aerosol-forming substrate, this arrangement may ensure that the aerosol-forming substrate is substantially uniformly heated.

The jacket heating element may be arranged on an outer surface of the jacket body. The jacket heating element may at least partially surround the cavity. The jacket heating element may surround the cavity.

The jacket heating element may be a helical coil. The jacket heating element may be arranged in a serpentine shape. The jacket heating element may be folded or curved to at least partially surround the cavity.

The jacket heating element may be a resistive heating element. Advantageously, a resistive heating element may be easily powered by a direct current from a power supply in an aerosol-generating device. The jacket heating element may comprise a resistive heating track arranged on a flexible substrate. The flexible substrate may comprise polyimide. By providing the resistive heating track on a flexible substrate, manufacture of the heater assembly may be simplified, as the resistive heating element may only require wrapping around the jacket.

When an alternating current is supplied to the induction coil, for example when the heater assembly of the present disclosure is a component part of an aerosol-generating device, an alternating magnetic field is generated in the cavity by the induction coil. Depending on the configuration of the resistive heating element, this alternating magnetic field may induce an alternating current in the resistive heating element. An alternating current induced in the resistive heating element may be particularly disadvantageous as the control circuitry would require filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element. Additionally, in some embodiments the control circuitry may be further configured to provide a resistive heating feedback signal from the resistive heating element to the microcontroller in order to follow a pre-determined resistive heating profile. The reduction in the induced alternating current in the resistive heating element may reduce the noise in the resistive heating feedback signal, allowing for the microcontroller to more precisely follow the pre-determined resistive heating profile.

To overcome this, the resistive heating element may be configured such that a total current induced in the resistive heating element by an alternating magnetic field within the cavity is substantially zero. In particular, the resistive heating element may be configured such that a total current induced in the resistive heating element an alternating magnetic field parallel to a longitudinal axis of the cavity and within the cavity is substantially zero.

The resistive heating element may comprise at least one primary portion and at least one secondary portion. The resistive heating element may comprise exactly one primary portion and exactly one secondary portion. Each of the at least one primary portions may be integrally formed with each of the at least one secondary portions. The resistive heating element may comprise two filaments arranged in a serpentine shape such that the two filaments are arranged substantially parallel to each other. The resistive heating element may comprise a plurality of alternating primary portions and secondary portions. The resistive heating element may comprise four or six alternating primary portions and secondary portions. The resistive heating element may comprise three primary portions and three secondary portions. The resistive heating element may comprise two primary portions and two secondary portions. The resistive heating element may extend between a first end and a second end. The at least one primary portion may arranged such that the at least one primary portion extends from the first end to the second end in a clockwise direction about the cavity when viewed from the first end of the cavity, and the at least one secondary portion may extend from the first end to the second end in an anti-clockwise direction about the cavity when viewed from the first end of the cavity. A cumulative length of the at least one primary portions may be substantially equal to a cumulative length of the at least one secondary portions.

Advantageously, in the above arrangement, the resistive heating element is arranged such that any alternating current induced in resistive heating element in a direction towards the negative terminal of control circuitry in an aerosol-generating device comprising a heater assembly according to the present disclosure, is equal to the current induced in resistive heating element in a direction towards the positive terminal of the control circuitry. As a result, a total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero. This minimising of total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry means that filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element are not required. This may therefore significantly reduce the complexity of the control circuitry required in an aerosol-generating device comprising a heater assembly according to the present disclosure.

The resistive heating element may comprise two substantially parallel tracks extending from the first end of the resistive heating element to the second end of the resistive heating element. Advantageously, such an arrangement may ensure that the total current induced in the resistive heating element by an alternating magnetic field within the cavity is substantially zero.

The resistive heating element may comprise a plurality of U-shaped portions. The plurality of U-shaped portions may be aligned with a longitudinal axis of the jacket. The U- shaped portions may be shaped such that the resistive heating element comprises a track portion which extends perpendicular to the longitudinal axis of the jacket positioned between two track portions which extend parallel to the longitudinal axis of the jacket. The U-shaped portions may ensure that the total current induced in the resistive heating element by an alternating magnetic field within the cavity is substantially zero, as above, whilst providing an alternative resistive heating element track pattern with sufficient area coverage to externally heat the aerosol-forming substrate in a uniform manner. The U-shaped portions may also advantageously provide a resistive heating element track pattern with a length long enough to provide a suitable resistance between the first end and the second end of the resistive heating element, whilst keeping the resistive heating element track within a defined surface area.

A resistance between the first end and the second end of the resistive heating element may be between 100 milliohms and 2000 milliohms, preferably between 200 milliohms and 1500 milliohms, preferably still between 500 milliohms and 1000 milliohms, and even more preferably between 700 milliohms and 900 milliohms. Such values have been found to provide particularly suitable resistive heating of the resistive heating element.

The resistive heating element may comprise a metal. The resistive heating element may comprise at least one of stainless steel, copper, gold, nickel, platinum, palladium, and silver. The resistive heating element may comprise graphene or a semiconductor. The resistive heating element may comprise a silver-palladium alloy. Advantageously, a silver-palladium alloy provides a suitable resistivity to achieve a desired resistance between the first end and the second end of the resistive heating element. A silver-palladium alloy may also comprise a particularly low magnitude of a temperature coefficient of resistance. The temperature coefficient of resistance may be defined by the rate of change of resistance with respect to a change of temperature. Advantageously, the resistance between the first end and the second end of a resistive heating element comprising a silver-palladium alloy will not vary significantly enough during operation to affect the operation of the resistive heating element. Preferably, a the resistive heating element comprises a material with a low magnitude of a temperature coefficient of resistance. A low magnitude of a temperature coefficient of resistance may be defined by the magnitude of the temperature coefficient of resistance being less than 0.004 K^-1 at 298 K. Advantageously, the resistance between the first end and the second end of a resistive heating element will not vary significantly enough during operation to affect the operation of the resistive heating element. Preferably, the resistive heating element comprises a material with a characterised or a characterisable temperature coefficient of resistance. Advantageously, the control circuitry of a device comprising such a heater assembly may therefore be easily configured to compensate for the change in the resistance between the first end and the second end of a resistive heating element during operation of the resistive heating element.

The cavity may be substantially cylindrical. The cavity may comprise a substantially circular cross section.

The jacket body may comprise an electrically insulating material. Advantageously, the electrically insulating material may prevent current from the resistive heating element flowing through the jacket. Furthermore, the electrically insulating material ensures that no eddy currents are induced in the jacket body by the induction coil during use of the heater assembly in an aerosol-generating device.

The jacket body may comprise a proximal portion, a central portion, and a distal portion. The central portion may be positioned between the proximal portion and the distal portion. The proximal portion, central portion, and distal portion may all be separable from one another. Advantageously, separable portions of the jacket body may allow for further enhanced modularity of the heater assembly.

The jacket heating element may be arranged on an outer surface of the central portion. Advantageously, the central portion comprising the jacket heating element may therefore be manufactured separately to the proximal and distal portions of the jacket body, before the three are assembled together.

The proximal portion may be snap-fit to the central portion. The central portion may be snap-fit to the distal portion. The proximal portion may be press-fit to the central portion. The central portion may be press-fit to the distal portion. Advantageously snap-fitting and pressfitting provide secure connections between portions of the jacket body without the need for further securing components or tools.

The proximal portion and the distal portion may comprise a polymer. The proximal portion and the distal portion may comprise polyether ether ketone (PEEK). Advantageously, PEEK is resistant to the temperatures experienced by the proximal portion and the distal portion during use of the heater assembly in an aerosol-generating device.

The central portion may comprise a ceramic. The ceramic may be alumina or zirconia. Advantageously, alumina and zirconia have low coefficients of thermal expansion, so will not expand significantly when heated during use. The central portion may be a thermally conductive central portion. The thermal conductivity of the thermally conductive central portion may be at least 20 Wnr¹K’¹, preferably at least 30 Wnr¹K’¹, and preferably still approximately 40 Wnr¹K’¹. Advantageously, a thermally conductive ceramic allows for a preferable rate of heat transfer from a resistive heating element located on an outer surface of the central portion to an internal surface of the central portion which partially defines the cavity, whilst being electrically insulating.

The jacket may comprise a jacket insulating layer at least partially surrounding the jacket body. Advantageously, the jacket insulating layer increase the thermal insulation around the jacket, reducing the heat transferred from the jacket heating element out to the sleeve. This may reduce the temperature of any surrounding housing of an aerosol-generating device during use of the heater assembly in such an aerosol-generating device, thereby increasing comfort for a user’s hands.

The jacket insulating layer may comprise Kapton™. The jacket insulating layer may surround the resistive heating element. The jacket insulating layer may surround the central portion. The jacket insulating layer may surround at least a portion of the proximal portion and at least a portion of the distal portion. The jacket insulating layer may not surround all of the proximal portion and all of the distal portion. Advantageously, the jacket insulating layer may therefore only be located around the central portion and portions of the proximal and distal portions, which experience the highest temperatures during use of the heater assembly in such an aerosol-generating device. Therefore, the quantity of jacket insulating layer in the heater assembly may be reduced.

The jacket insulating layer may be fixed to the proximal portion and the distal portion. The jacket insulating layer may be glued to the proximal portion and the distal portion. The jacket insulating layer may not contact the jacket heating element. Advantageously, by fixing the jacket insulating layer to the proximal portion and the distal portion, and not the jacket heating element or the central portion, infiltration of adhesive material, such a glue, into the jacket cavity may be reduced.

The jacket may comprise an insulating zone between the jacket insulating layer and the jacket heating element. The insulating zone may be an air gap. Advantageously, an air gap provides an effective and inexpensive arrangement for reducing the heat transferred from the jacket heating element out to the sleeve.

The insulating zone may comprise polyimide. The insulating zone may comprise aerogel. Advantageously, an insulating zone comprising polyimide or aerogel may provide a more effective arrangement for reducing the heat transferred from the jacket heating element out to the sleeve compared to the insulating zone being an air gap, as heat transfer via convection is reduced when compared to the insulating zone being an air gap.

The jacket may comprise an inner surface. The inner surface may define the cavity. The jacket may comprise at least one groove defined on the inner surface of the jacket. The at least one groove may extend parallel to a longitudinal axis of the jacket. The at least one groove may comprise a plurality of grooves. The cavity may comprise a proximal opening configured to receive the aerosol-generating article therethrough. The cavity may comprise a closed distal end. Advantageously, such an arrangement comprising at least one groove defined on the inner surface of the jacket provides during use an airflow pathway from the proximal opening, through the at least one groove to the distal end of the cavity, through the aerosol-generating article which is received in the cavity, and into the mouth of a user. This arrangement ensures that no other airflow inlets are necessary in heater assembly or the housing of an aerosol-generating device in which the heater assembly is arranged.

The jacket may comprise a jacket air inlet towards the distal end of the cavity. The jacket may comprise a jacket air inlet at the distal end of the cavity. The distal portion of the jacket may comprise the jacket air inlet. Advantageously, in such an arrangement there is no need for at least one groove defined on the inner surface of the jacket in order to provide an airflow pathway. The inner surface of the jacket may therefore be a smooth cylinder, which maximises heat transferred from the jacket to the aerosol-generating article.

The jacket may be snap-fit to the sleeve. The jacket may be press-fit to the sleeve. Advantageously snap-fitting and press-fitting provide secure connections between the jacket and the sleeve without the need for further securing components or tools.

The heater assembly may be configured to be received in a housing of an aerosolgenerating device. Advantageously, the heater assembly may therefore be manufactured separately to the housing of the aerosol-generating device, allowing for enhanced modularity of an aerosol-generating device comprising both.

The sleeve may comprise an electrically insulating material. The sleeve may comprise a plastics material. The sleeve may comprise a different material to the jacket. The sleeve may not comprise PEEK. The sleeve may comprise a Liquid crystal polymer (LCP). Advantageously, as the sleeve is a separate component to the jacket, the sleeve may be manufactured from a different material to the jacket. Because the sleeve is subject to lower temperatures than the jacket during use, the sleeve need not be made from heat-resistant materials such as PEEK. The sleeve instead may be manufactured from less heat-resistant materials, thereby reducing the cost of manufacture of the sleeve, and therefore reducing the overall cost of the heater assembly.

The induction coil may comprise an induction coil. The induction coil may be a helical coil. The induction coil may be arranged on a surface of the sleeve. The induction coil may be arranged on an outer surface of the sleeve. The induction coil may be wound about a winding axis parallel to a longitudinal axis of the sleeve. Advantageously, winding the induction coil about the sleeve may reducing manufacturing time.

The induction coil may comprise a first filament. The first filament may be a flat filament. The first filament may comprise a first cross sectional area defined in a first plane. The first cross sectional area may be perpendicular to the direction of extension of the first filament between the first end and the second end of the induction coil. The first cross sectional area may be perpendicular to the direction of flow of an alternating current within the induction coil during use. The first cross sectional area may be substantially rectangular in shape. The first cross sectional area may have a first width and a first thickness. The first width may be greater than the first thickness. Advantageously, such an induction coil comprising a flat filament has been found to be suitable to provide a varying magnetic field for inductive heating of a susceptor element, whilst reducing resistive losses in the induction coil.

The induction coil may at least partially surround the cavity. The induction coil may surround the cavity. The induction coil may comprise a first and a second electrical connector. The first and second electrical connectors may be embedded within the sleeve. Advantageously, such an arrangement may allow for easier and faster manufacturing of the inductor assembly. In some known inductor assemblies, in order to connect both ends of an induction coil or coil to a power supply, it is necessary to provide two electrical contacts which are adjacent to one-another. For example, a distal end of the induction coil or coil must therefore traverse the longitudinal length of the inductor assembly to provide a first electrical contact which is adjacent to the proximal end of the induction coil or coil which provides a second electrical contact. This often requires bending of the induction coil and securing the induction coil in place, for example by gluing, which requires time. Additionally this arrangement also often requires an insulator to be provided between the portion of the induction coil which traverses the longitudinal length of the inductor assembly, and the rest of the induction coil. This is to prevent short-circuiting between the portion of the induction coil which traverses the longitudinal length of the inductor assembly, and the rest of the induction coil. This previous arrangement is therefore not desirable from a manufacturing or cost perspective.

However, the present arrangement allows for first and second electrical connectors to be embedded within the sleeve, so electrically insulated from the induction coil. The remaining portion of the induction coil may therefore be wrapped around the outer surface of the sleeve in a single manufacturing step, without the need to bend the induction coil, or provide any additional insulating materials.

The sleeve may be moulded around the first and second electrical connectors. The sleeve may be injection moulded. The sleeve may be injection moulded around the first and second electrical connectors. Advantageously, moulding provides a single manufacturing method to embed and secure the first and second electrical connectors within the sleeve, without the need for two separate sections of sleeve clamping the first and second electrical connectors in place.

The first electrical connector may be in electrical contact with a first end of the induction coil. The second electrical connector may be in electrical contact with a second end of the induction coil. In particular, the first and second electrical connectors may be in electrical contact with the first and second ends of the induction coil respectively through apertures in the sleeve. The first and second electrical connectors may therefore be configured to provide an alternating current in the induction coil when an alternating voltage is applied between the first and second electrical connectors.

The first and second electrical connectors may extend parallel to the longitudinal axis of the sleeve. The first and second electrical connectors may each comprise flat filaments. The first and second electrical connectors may each comprise a width perpendicular to the longitudinal axis of the sleeve and a thickness perpendicular to the longitudinal axis of the sleeve, wherein the width is greater than the thickness. The first and second electrical connectors may each comprise a substantially rectangular cross-sectional area in a plane perpendicular to the longitudinal axis of the sleeve. Advantageously, flat filaments for the first and second electrical connectors reduce resistive losses in the first and second electrical connectors, whilst allowing the thickness of the sleeve in a radial direction to remain thin.

The first electrical connector may comprise a first end in electrical contact with the first end of the induction coil, and a second end exposed for connection to a power supply. The second electrical connector may comprise a first end in electrical contact with the second end of the induction coil, and a second end exposed for connection to a power supply. Advantageously, the inductor assembly may therefore be manufactured separately to the remaining components of an aerosol-generating device, and then be assembled into an aerosol-generating device, including the step of electrically connecting the second ends of the first and second electrical connectors to a power supply.

The second ends of the first and second electrical connectors may be both arranged at a first end of the sleeve. The first end of the sleeve may be a distal end of the sleeve. Advantageously, this arrangement may minimise the total length of electrical wire needed to electrically connect the first and second electrical connectors to a power supply.

The sleeve may comprise a sleeve air inlet and a sleeve air outlet, and a sleeve airflow pathway between the sleeve air inlet and the sleeve air outlet. The sleeve air outlet may cooperate with the jacket air inlet. The heater assembly may define an assembly airflow pathway from the sleeve air inlet, via the sleeve airflow pathway, the sleeve air outlet, the jacket air inlet, and the cavity, to the proximal opening of the cavity. As above, in such an arrangement there is no need for at least one groove defined on the inner surface of the jacket in order to provide an airflow pathway. The inner surface of the jacket may therefore be a smooth cylinder, which maximises contact with the aerosol-generating article, and so maximises heat transferred from the jacket to the aerosol-generating article.

The electrical resistance between the first end and the second end of the induction coil may be less than 250 milliohms. The electrical resistance between the first end and the second end of the induction coil may be less than 150 milliohms. The electrical resistance between the first end and the second end of the induction coil may be approximately 100 milliohms. The resistance of the resistive heating element may be greater than the resistance of the induction coil. The resistance of the resistive heating element may be at least 2 times greater than the resistance of the induction coil. Advantageously, the relatively low resistance of the induction coil results in less power dissipated as heat in the induction coil compared to the equivalent power dissipated as heat in the jacket heating element.

The sleeve may comprise a sleeve insulating layer at least partially surrounding the sleeve. The sleeve insulating layer may comprise Kapton™. The sleeve insulating layer may at least partially surround the induction coil. Advantageously, the sleeve insulating layer may reduce the rate of heat transfer from the sleeve to other components of an aerosol-generating device when the heater assembly is received within an aerosol-generating device. This would make the aerosol-generating device more comfortable for a user to hold.

The induction coil may comprise metal. The induction coil may comprise copper.

The induction coil may consist of copper. Advantageously, copper has a low resistivity, so the induction coil has a relatively low resistance. The induction coil may comprise a different material to the resistive heating element. The induction coil may consist of a different material to the resistive heating element.

According to the present disclosure there is also provided an aerosol-generating device. The aerosol-generating device may comprise a heater assembly according to the present disclosure. For example, the aerosol-generating device may comprise a heater assembly according to the first aspect. The heater assembly may comprise a jacket defining a cavity for receiving at least a portion of an aerosol-generating article. The heater assembly may comprise an inductor assembly comprising a sleeve at least partially surrounding the jacket. The inductor assembly may comprise an induction coil coupled to the sleeve. The aerosolgenerating device may comprise at least one power supply for providing electrical power to the induction coil. The aerosol-generating device may comprise control circuitry configured to control the supply of power from the at least one power supply to the induction coil. The control circuitry may be configured to provide an alternating current to the induction coil, such that the induction coil generates an alternating magnetic field within the cavity.

In some examples, the induction heating device may further comprise at least one power supply for providing a current to the induction coil. The induction heating device may further comprise control circuitry configured to control the supply of power from the at least one power supply to the induction coil. The control circuitry may be configured to provide an alternating current to the induction coil, such that the induction coil generates an alternating magnetic field within the cavity. The inductive heating device may further comprise a housing. The heater assembly may be received within the housing. The at least one power supply and the control circuitry may be located within the housing. The housing may provide a surface for the user to hold during use.

The induction coil may be configured to inductively heat one or more susceptors within the cavity when the induction coil is supplied with the alternating current. The aerosolgenerating article may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. Advantageously, in such embodiment the aerosol-generating device does not need to include a susceptor as a component of the aerosol-generating device. The inductive heating may be caused by the generation of eddy currents in the susceptor. The inductive heating may be caused by magnetic hysteresis losses.

The inductive heating device may further comprise one or more susceptors. The one or more susceptors are configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the cavity. The one or more susceptors may be in the form of at least one blade. The one or more susceptors may be in the form of at least one pin. Advantageously, the form of an aerosol-generating article to be received in the cavity may be simplified, as in such embodiment the aerosol-generating article does not need to include a susceptor as a component of the aerosol-generating article.

The at least one power supply may comprise a first DC power source. The first DC power source may be a battery. The control circuitry may comprise a DC/AC converter connected to the first DC power source. The DC/AC converter may include a Class-E power amplifier including a first transistor switch and an LC load network. The alternating current may be a high frequency alternating current. The high frequency alternating current may have a frequency of between about 1 megahertz and about 30 megahertz. The high frequency alternating current may have a frequency of between about 1 megahertz and about 10 megahertz. The high frequency alternating current may have a frequency of between about 5 megahertz and about 8 megahertz. Advantageous, such frequencies may be particularly well suited to heating a susceptor in order to evolve aerosol from an aerosol-forming substrate.

The jacket may comprise a resistive heating element. The control circuitry may be further configured to control the supply of power from the at least one power supply to the resistive heating element. The control circuitry may be further configured to provide a direct current to the resistive heating element. The control circuitry may be configured to provide the direct current to the resistive heating element such that the resistive heating element is heated to at least 80°C. Advantageously, a resistive heating element may be easily powered by a direct current from a power supply in an aerosol-generating device. The resistive heating element may be configured to externally heat the aerosol-forming substrate of the aerosol-generating article. In particular, the resistive heating element may be configured to heat a periphery of the cavity. When an aerosol-generating article is received within the cavity, the resistive heating element may be configured to heat an external portion of the aerosol-forming substrate. Advantageously, if the induction coil is configured to heat a central portion of the aerosol-forming substrate, this arrangement may ensure that no portion of the aerosol-forming substrate is overheated.

The resistive heating element may comprise at least one primary portion and at least one secondary portion. The at least one primary portion may be arranged such that the direct current flows in the at least one primary portion in a clockwise direction about the cavity when viewed from the first end of the cavity, and the at least one secondary portion may be arranged such that the direct current flows in the at least one secondary portion in an anticlockwise direction about the cavity when viewed from the first end of the cavity. A cumulative length of the at least one primary portion may be substantially equal to a cumulative length of the at least one secondary portion. As stated above with respect to the first aspect, such an arrangement may minimise the total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry by the induction coil. This may therefore significantly reduce the complexity of the control circuitry required in the aerosol-generating device.

According to the present disclosure there is also provided an aerosol-generating system. The aerosol-generating system may comprise an inductive heating device according to the present disclosure. For example, the inductive heating device may comprise a heater assembly according to the present disclosure. For example, the inductive heating device may comprise an inductor assembly according to the first aspect. The inductor assembly may comprise a jacket defining a cavity for receiving at least a portion of an aerosol-generating article. The inductor assembly may comprise a sleeve at least partially surrounding the jacket. The inductor assembly may comprise an induction coil coupled to the sleeve. The inductive heating device may comprise at least one power supply for providing electrical power to the induction coil. The inductive heating device may comprise control circuitry configured to control the supply of power from the at least one power supply to the induction coil. The control circuitry may be configured to provide an alternating current to the induction coil, such that the induction coil generates an alternating magnetic field within the cavity. The aerosol-generating system may further comprise an aerosol-generating article comprising an aerosol-generating substrate. The aerosol-generating article may be received in the cavity of the inductive heating device.

According to a second aspect there is provided an aerosol-generating system comprising: an inductive heating device according to the present disclosure; and an aerosol- generating article comprising an aerosol-generating substrate, wherein the aerosolgenerating article is received in the cavity of the inductive heating device.

An aerosol-generating system according to the second aspect realises the same advantages as the inductive heating device according to the first aspect, as outlined above. That is, such an aerosol-generating system allows for modularity during the manufacturing and design process, as well as a more cost-efficient aerosol-generating system.

The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosolforming substrate may comprise tobacco material. The aerosol-generating article may comprise one or more susceptors. The one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. Advantageously, in such embodiment the aerosol-generating device does not need to include a susceptor as a component of the aerosol-generating device.

An article airflow pathway may be defined from the proximal end of the jacket, through the cavity airflow pathway to the distal end of the jacket, and from a distal end of the aerosolgenerating article, through the aerosol-generating article to a proximal end of the aerosolgenerating article.

A cavity airflow pathway may be defined between the aerosol-generating article and the jacket. The cavity airflow pathway may extend from a proximal end of the jacket to a distal end of the jacket. The cavity airflow pathway may be defined between the aerosol-generating article and the at least one groove. A system airflow pathway may therefore be defined by the cavity airflow pathway followed by the article airflow pathway. As above with regards to the first aspect, arrangement ensures that no other airflow inlets are necessary in heater assembly or the housing of the inductive heating device.

The jacket may comprise a jacket air inlet towards the distal end of the cavity. The jacket may comprise a jacket air inlet at the distal end of the cavity. The distal portion of the jacket may comprise the jacket air inlet. The sleeve may comprise a sleeve air inlet and a sleeve air outlet, and a sleeve airflow pathway between the sleeve air inlet and the sleeve air outlet.

The sleeve air outlet may cooperate with the jacket air inlet. The heater assembly may define an assembly airflow pathway from the sleeve air inlet, via the sleeve airflow pathway, the sleeve air outlet, the jacket air inlet, and the cavity, to the proximal opening of the cavity. The sleeve air inlet may communicate with the exterior of the aerosol-generating device.

The jacket air inlet may communicate with the exterior of the aerosol-generating device. For example, the jacket air inlet may communicate with the exterior of the aerosol-generating device via a housing air inlet in the housing of the inductive heating device. The heater assembly may define an assembly airflow pathway from housing air inlet, via the jacket air inlet and the cavity, to the proximal opening of the cavity. A system airflow pathway may therefore be defined by the assembly airflow pathway followed by the article airflow pathway. Advantageously, in such an arrangement there is no need for at least one groove defined on the inner surface of the jacket in order to provide an airflow pathway. The inner surface of the jacket may therefore be a smooth cylinder, which maximises heat transferred from the jacket to the aerosol-generating article.

According to the present disclosure there is also provided an inductor assembly for an aerosol-generating device. The inductor assembly may comprise a sleeve configured for internally receiving a jacket for carrying an aerosol-generating article. The inductor assembly may comprise an induction coil coupled to the sleeve.

According to a third aspect there is also provided an inductor assembly for an inductive heating device. The inductor assembly comprises a sleeve configured for internally receiving a jacket for carrying an aerosol-generating article. The inductor assembly further comprises an induction coil coupled to the sleeve. A wire material of the induction coil comprises an elongate cross-section. The wire material further comprises an electrically conductive coating.

Advantageously, the inductor assembly may therefore be manufactured separately to the housing of an inductive heating device, and separately to any further components of an inductor assembly for an inductive heating device, allowing for enhanced modularity of an inductive heating device comprising either.

The induction coil may comprise the same features as any of the induction coils described in relation to the first aspect.

The inductor assembly may further comprise a first electrical connector in electrical contact with a first end of the induction coil. The inductor assembly may further comprise a second electrical connector in electrical contact with a second end of the induction coil. The first and second electrical connectors may be coupled to the sleeve. The first and second electrical connectors may be embedded within the sleeve. As recited above with respect to the first aspect, such an arrangement may advantageously allow for easier and faster manufacturing of the inductor assembly. In particular, the induction coil may therefore be wrapped around the outer surface of the sleeve in a single manufacturing step, without the need to bend the induction coil, or provide any additional insulating materials.

The sleeve may be moulded around the first and second electrical connectors. The sleeve may be injection moulded around the first and second electrical connectors. Advantageously, moulding provides a single manufacturing method to embed and secure the first and second electrical connectors within the sleeve, without the need for two separate sections of sleeve clamping the first and second electrical connectors in place.

The first and second electrical connectors may extend parallel to the longitudinal axis of the sleeve. The first electrical connector may comprise a first end in electrical contact with the first end of the induction coil, and a second end exposed for connection to a power supply. The second electrical connector may comprise a first end in electrical contact with the second end of the induction coil, and a second end exposed for connection to a power supply. Advantageously, the inductor assembly may therefore be manufactured separately to the remaining components of an aerosol-generating device, and then be assembled into an aerosol-generating device, including the step of electrically connecting the second ends of the first and second electrical connectors to a power supply.

The first and second electrical connectors may each comprise flat filaments. The first and second electrical connectors may each comprise a width perpendicular to the longitudinal axis of the sleeve and a thickness perpendicular to the longitudinal axis of the sleeve, wherein the width is greater than the thickness. The first and second electrical connectors may each comprise a substantially rectangular cross-sectional area in a plane perpendicular to the longitudinal axis of the sleeve. Advantageously, flat filaments for the first and second electrical connectors reduce resistive losses in the first and second electrical connectors, whilst allowing the thickness of the sleeve in a radial direction to remain thin.

The induction coil may be arranged on an outer surface of the sleeve.

The sleeve may comprise an electrically insulating material. The electrically insulating material may have an electrical resistivity at least 10 times that of the induction coil, and preferably at least 100 times that of the induction coil. The sleeve may comprise a plastics material. The sleeve may not comprise PEEK. The sleeve may comprise a Liquid crystal polymer (LCP). Advantageously, as the sleeve is a separate component to the jacket, the sleeve may be manufactured from a different material to the jacket. Because the sleeve is subject to lower temperatures than the jacket during use, the sleeve need not be made from heat-resistant materials such as PEEK. The sleeve may instead be manufactured from less heat-resistant materials, thereby reducing the cost of manufacture of the sleeve.

The sleeve may be configured to be received in a housing of an aerosol-generating device. The sleeve may be substantially cylindrical. The sleeve may comprise a substantially circular cross section.

According to the present disclosure there is also provided a kit of parts comprising an inductor assembly. The inductor assembly may comprise a sleeve configured for internally receiving a jacket for carrying an aerosol-generating article. The inductor assembly may comprise an induction coil coupled to the sleeve. The inductor assembly may be the inductor assembly according to the present disclosure. The kit of parts may further comprise a jacket. The jacket may define a cavity for receiving at least a portion of an aerosol-generating article. The jacket may be the jacket according to the present disclosure. The jacket may be configured to be received in the sleeve.

The kit of parts may further comprise a housing of an inductive heating device configured to receive the sleeve therein. The housing of an inductive heating device may be the housing of an inductive heating device according to the present disclosure.

According to a fourth aspect there is provided a kit of parts comprising: an inductor assembly comprising a sleeve configured for internally receiving a jacket for carrying an aerosol-generating article, the inductor assembly comprising an induction coil coupled to the sleeve, wherein a wire material of the induction coil comprises an elongate cross-section, wherein the wire material comprises an electrically conductive coating; a jacket defining a cavity for receiving at least a portion of an aerosol-generating article, the jacket being configured to be received in the sleeve; and a housing of an aerosol-generating device configured to receive the sleeve therein.

According to the present disclosure there is also provided a method of manufacturing an inductor assembly for an inductive heating device. The inductor assembly may be an inductor assembly according to the present disclosure. The method may comprise providing a sleeve. The method may comprise coupling an induction coil to the sleeve.

According to a fifth aspect there is provided a method of manufacturing an inductor assembly for an aerosol-generating device, the method comprising: providing an induction coil comprising a wire material having an elongate cross-section; applying an electrically conductive coating to the wire material; providing a sleeve, and coupling the induction coil to the sleeve.

Advantageously, the inductor assembly may therefore be manufactured separately to the housing of an inductive heating device, and separately to any further components of a heater assembly for an inductive heating device, allowing for enhanced modularity of an inductive heating aerosol-generating device comprising either.

The method may further comprise coupling a first electrical connector and a second electrical connector to the sleeve. The first electrical connector and second electrical connector may allow for the induction coil to be electrically connected to a power supply in an aerosol-generating device.

Providing a sleeve may comprise moulding a sleeve around a first electrical connector and a second electrical connector. Providing a sleeve may comprise injection moulding a sleeve around a first electrical connector and a second electrical connector. Advantageously, moulding provides a single manufacturing method to embed and secure the first and second electrical connectors within the sleeve, without the need for two separate sections of sleeve clamping the first and second electrical connectors in place.

Providing a sleeve may comprise moulding a sleeve around a first electrical connector and a second electrical connector such that the first electrical connector comprises a second end exposed for connection to a power supply and the second electrical connector comprises a second end exposed for connection to a power supply. Advantageously, the inductor assembly may therefore be manufactured separately to the remaining components of an inductive heating device, and then be assembled into an aerosol-generating device, including the step of electrically connecting the second ends of the first and second electrical connectors to a power supply.

Coupling an induction coil to the sleeve may comprise arranging the induction coil on a surface of the sleeve such that the first electrical connector is in electrical contact with a first end of the induction coil and the second electrical connector in electrical contact with a second end of the induction coil. Coupling an induction coil to the sleeve may comprise arranging the induction coil on a surface of the sleeve such that a first end of the first electrical connector is in electrical contact with a first end of the induction coil and a first end of the second electrical connector in electrical contact with a second end of the induction coil. The first and second electrical connectors may therefore be configured to provide an alternating current in the induction coil when an alternating voltage is applied between the first and second electrical connectors.

The method may further comprise soldering the first electrical connector to the first end of the induction coil and soldering the second electrical connector to the second end of the induction coil. This may ensure reliable electrical connection between the electrical connectors and the induction coil.

Arranging an induction coil on a surface of the sleeve may comprise winding the induction coil on the surface of the sleeve. The surface of the sleeve may be an outer surface of the sleeve. Advantageously, winding the induction coil about the sleeve may reducing manufacturing time.

The method may further comprise at least partially surrounding the sleeve with a sleeve insulating layer. The method may further comprise wrapping the sleeve with the sleeve insulating layer. Advantageously, the jacket insulating layer increase the thermal insulation around the jacket, reducing the heat transferred from the jacket heating element out to the sleeve. This may reduce the temperature of any surrounding housing of an inductive heating device during use of the heater assembly in such an inductive heating device, thereby increasing comfort for a user’s hands.

According to the present disclosure there is also provided a method of manufacturing an inductive heating device. In particular, the inductive heating device may be an inductive heating device according to the present disclosure. The method may comprise manufacturing an inductor assembly according to the present disclosure. In particular, the inductor assembly may be an inductor assembly according to the present disclosure. The method may comprise receiving a jacket within the inductor assembly such that the inductor assembly at least partially surrounds the jacket.

According to a sixth aspect there is provided a method of manufacturing a inductor assembly for an inductive heating device, the method comprising: manufacturing an inductor assembly according to the present disclosure, receiving a jacket within the inductor assembly such that the inductor assembly at least partially surrounds the jacket.

The jacket may comprise a proximal portion, a central portion, and a distal portion. The method may further comprise connecting the proximal portion to the central portion, and connecting the central portion to the distal portion. Advantageously, separable portions of the jacket body may allow for further enhanced modularity of the inductor assembly.

Connecting the proximal portion to the central portion may comprise press-fitting the proximal portion to the central portion. Connecting the proximal portion to the central portion may comprise snap-fitting the proximal portion to the central portion. Connecting the central portion to the distal portion may comprise press-fitting the central portion to the distal portion. Connecting the central portion to the distal portion may comprise snap-fitting the central portion to the distal portion. Advantageously snap-fitting and press-fitting provide secure connections between portions of the jacket body without the need for further securing components or tools.

The method may further comprise arranging a jacket heating element on an outer surface of the jacket. The jacket heating element may be a resistive heating element. Arranging a jacket heating element on an outer surface of the jacket may comprise arranging a jacket heating element on an outer surface of the central portion. Advantageously, the central portion comprising the jacket heating element may therefore be manufactured separately to the proximal and distal portions of the jacket body, before the three are assembled together.

The method may further comprise at least partially surrounding the jacket with an insulating layer. The method may further comprise wrapping the jacket with an insulating layer. Advantageously, the jacket insulating layer increase the thermal insulation around the jacket, reducing the heat transferred from the jacket heating element out to the sleeve. This may reduce the temperature of any surrounding housing of an inductive heating device during use of the heater assembly in such an inductive heating device, thereby increasing comfort for a user’s hands.

According to the present disclosure there is also provided a method of manufacturing an inductive heating device. The inductive heating device may be an inductive heating device according to the present disclosure. The method may comprise manufacturing an inductor assembly according to the present disclosure. In particular, the inductor assembly may be an inductor assembly according to the present disclosure. The method may comprise receiving a jacket within the inductor assembly such that the inductor assembly at least partially surrounds the jacket. The method may comprise receiving the inductor assembly within a housing of the inductive heating device such that the housing at least partially surrounds the inductor assembly.

According to an seventh aspect there is provided a method of manufacturing an inductive heating device, the method comprising: manufacturing a inductor assembly according to the present disclosure, and receiving the heater assembly within a housing of the inductive heating device such that the housing at least partially surrounds the inductor assembly.

Advantageously, such a method of manufacturing an inductive heating device allows for modularity during the manufacturing process, as well as a more cost-efficient inductive heating device.

As used herein, the term “inductive heating device” or “aerosol-generating device” is used to describe a device that interacts with an aerosol-forming substrate to generate an aerosol. Preferably, the aerosol-generating device is a smoking device that interacts with an aerosol-forming substrate to generate an aerosol that is directly inhalable into a user’s lungs thorough the user's mouth.

As used herein, the term “aerosol-forming substrate” refers to a substrate consisting of or comprising an aerosol-forming material that is capable of releasing volatile compounds upon heating to generate an aerosol.

Preferably, the aerosol-forming substrate comprises nicotine. More preferably, the aerosol-forming substrate comprises tobacco. Alternatively or in addition, the aerosolforming substrate may comprise a non-tobacco containing aerosol-forming material.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosolforming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, strands, strips, or sheets containing one or more of: herb leaf, tobacco leaf, tobacco ribs, expanded tobacco and homogenised tobacco.

Optionally, the solid aerosol-forming substrate may contain tobacco or non-tobacco volatile flavour compounds, which are released upon heating of the solid aerosol-forming substrate. The solid aerosol-forming substrate may also contain one or more capsules that, for example, include additional tobacco volatile flavour compounds or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol-forming substrate.

Optionally, the solid aerosol-forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may take the form of powder, granules, pellets, shreds, strands, strips, or sheets. The solid aerosol-forming substrate may be deposited on the surface of the carrier in the form of, for example, a sheet, foam, gel, or slurry. The solid aerosol-forming substrate may be deposited on the entire surface of the carrier, or alternatively, may be deposited in a pattern in order to provide a non-uniform flavour delivery during use.

In a preferred embodiment, the aerosol-forming substrate comprises homogenised tobacco material. As used herein, the term “homogenised tobacco material” refers to a material formed by agglomerating particulate tobacco.

Preferably, the aerosol-forming substrate comprises a gathered sheet of homogenised tobacco material. As used herein, the term “sheet” refers to a laminar element having a width and length substantially greater than the thickness thereof. As used herein, the term “gathered” is used to describe a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosolgenerating article. Preferably, the aerosol-forming substrate comprises an aerosol former. As used herein, the term “aerosol former” is used to describe any suitable known compound or mixture of compounds that, in use, facilitates formation of an aerosol and that is substantially resistant to thermal degradation at the operating temperature of the aerosolgenerating article.

Suitable aerosol-formers are known in the art and include, but are not limited to: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and, most preferred, glycerine.

The aerosol-forming substrate may comprise a single aerosol former. Alternatively, the aerosol-forming substrate may comprise a combination of two or more aerosol formers.

As used herein, the term “susceptor” refers to an element comprising a material that is capable of converting the energy of a magnetic field into heat. When a susceptor is located in an alternating magnetic field, the susceptor is heated. Heating of the susceptor may be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. As used herein when referring to an aerosol-generating device, an aerosolgenerating article, a jacket, a sleeve, a heater assembly or an inductor assembly, the term “longitudinal” may refer to the longest direction of any such component of an aerosolgenerating system. The term “longitudinal” may refer to the direction of extension of the component from a proximal end of the component to a distal end of the component.

As used herein, the term “winding axis” may refer to a straight axis or line about which a component is wound. For example, the term “winding axis” may refer to a straight axis or line about which a component is helically wound. All points of the wound component may be substantially equidistant from the winding axis.

As used herein, the term “sleeve” may refer to a component with a substantially hollow and substantially cylindrical shape. The component may comprise a lumen within the sleeve.

As used herein when referring to an aerosol-generating device, the terms “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the aerosol-generating device in relation to the direction in which air flows through the aerosol-generating device during use thereof. Aerosol-generating devices according to the invention may comprise a proximal end through which, in use, an aerosol exits the device. The proximal end of the aerosol-generating device may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating device may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating device may be described as being upstream or downstream of one another based on their relative positions with respect to the airflow path of the aerosol-generating device. As used herein when referring to an aerosol-generating article, the terms “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the aerosolgenerating article in relation to the direction in which air flows through the aerosol-generating article during use thereof. Aerosol-generating articles according to the invention may comprise a proximal end through which, in use, an aerosol exits the article. The proximal end of the aerosol-generating article may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating article may be described as being upstream or downstream of one another based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The front of a component, or portion of a component, of the aerosol-generating article is the portion at the end closest to the upstream end of the aerosol-generating article. The rear of a component, or portion of a component, of the aerosol-generating article is the portion at the end closest to the downstream end of the aerosol-generating article.

The invention is defined in the claims. However, below there is provided a non- exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example Ex1 . An inductive heating device for an aerosol-generation, the device comprising: a device housing comprising a heater assembly defining a cavity having an internal surface for receiving at least a portion of an aerosol-forming insert comprising an aerosolforming substrate and a susceptor; and an induction coil having a magnetic axis and arranged within the device housing such as to surround at least a portion of the cavity; wherein a wire material forming the induction coil has a cross-section comprising a main portion, the main portion having a longitudinal extension in a direction of the magnetic axis and a lateral extension perpendicular to the magnetic axis, wherein the longitudinal extension is longer than the lateral extension of the main portion, wherein the wire material comprises an electrically conductive coating.

Example Ex2. An inductive heating device according to Example Ex1 , wherein the electrically conductive coating has a higher electrical conductivity than the wire material.

Example Ex3. An inductive heating device according to any preceding Example Ex, wherein the electrically conductive coating has a higher resistance to oxidation than the wire material.

Example Ex4. An inductive heating device according to any preceding Example Ex, wherein the electrically conductive coating has a maximum thickness within the range of 0.5- 100pm.

Example Ex5. An inductive heating device according to Example Ex4, wherein the electrically conductive coating has a maximum thickness of less than 30pm.

Example Ex6. An inductive heating device according to any preceding Example Ex, wherein the main portion comprises two opposing longitudinal ends and two opposing lateral ends, wherein the thickness of the electrically conductive coating around regions of the main portion wherein the longitudinal ends meet the lateral ends is greater than the thickness of the electrically conductive coating at other regions of the main portion.

Example Ex7. An inductive heating device according to any of Example Ex1 to Ex5, wherein the main portion comprises two opposing longitudinal ends and two opposing lateral ends, wherein the thickness of the electrically conductive coating is greater on the longitudinal ends than on the lateral ends of the main portion. Example Ex8. An inductive heating device according to Example Ex7, wherein there is no electrically conductive coating on the lateral ends of the main portion.

Example Ex9. An inductive heating device according to any preceding Example Ex, wherein the electrically conductive coating comprises at least one of silver or gold.

Example Ex10. An inductive heating device according to any preceding Example Ex, wherein the device further comprises a power source connected to the induction coil and configured to provide a high frequency current to the induction coil.

Example Ex11 . An inductive heating device according to any preceding Example Ex, wherein the main portion forms the entire cross-section of the wire material.

Example Ex12. An inductive heating device according to any of Example Ex1 to Ex10, wherein the cross-section of the wire material further comprises a secondary portion, the secondary portion having a longitudinal extension in the direction perpendicular to the magnetic axis and a lateral extension in the direction of the magnetic axis, which longitudinal extension is longer than a lateral extension of the secondary portion.

Example Ex13. An inductive heating device according to any preceding Example Ex, further comprising a magnetic shield provided between an outer wall of the device housing and the induction coil.

Example Ex14. An inductive heating device according to any preceding Example Ex, wherein a circumferential portion of the inner surface of the cavity and the induction coil are cylindrical shape.

Example Ex15. An inductive heating device according to any preceding Example Ex, wherein the heater assembly comprising: a jacket lining at least a portion of the inner surface of the cavity for heating an aerosol-generating article received within the cavity, and a sleeve at least partially surrounding the jacket, wherein the induction coil is coupled to the sleeve.

Example Ex16. An inductive heating device according to Example Ex15, wherein the jacket comprises a jacket body and a jacket heating element, and wherein the jacket heating element is arranged on an outer surface of the jacket body.

Example Ex17. An inductive heating device according to any of Example Ex15 to Ex16, wherein the jacket heating element is a resistive heating element.

Example Ex18. An inductive heating device according to any of Example Ex15 to Ex17, wherein the jacket body comprises a proximal portion, a central portion, and a distal portion, wherein the central portion is positioned between the proximal portion and the distal portion, and wherein the jacket heating element is arranged on an outer surface of the central portion. Example Ex19. An inductive heating device according to any of Example Ex15 to Ex18, wherein the jacket comprises a jacket insulating layer at least partially surrounding the jacket body, and wherein the jacket comprises an insulating zone between the jacket insulating layer and the jacket heating element.

Example Ex20. An inductive heating device according to any of Example Ex15 to Ex19, wherein the induction coil is arranged on an outer surface of the sleeve, wherein the inductive heating device further comprises: a first and a second electrical connector, wherein the first electrical connector is in electrical contact with a first end of the induction coil, and wherein the second electrical connector is in electrical contact with a second end of the induction coil, wherein the first and second electrical connectors are embedded within the sleeve.

Example Ex21. An aerosol-generating system comprising: an inductive heating device according to any preceding claim; and an aerosol-generating article comprising an aerosol-generating substrate, wherein the aerosol-generating article is received in the cavity of the inductive heating device.

Example Ex22. An inductor assembly for an aerosol-generating device, the inductor assembly comprising: a sleeve configured for internally receiving a jacket for carrying an aerosol-generating article, and an induction coil coupled to the sleeve, wherein a wire material of the induction coil comprises an elongate cross-section, wherein the wire material comprises an electrically conductive coating.

Example Ex23. A method of manufacturing an inductor assembly for an aerosolgenerating device, the method comprising: providing an induction coil comprising a wire material having an elongate crosssection; applying an electrically conductive coating to the wire material; providing a sleeve, and coupling the induction coil to the sleeve.

Example Ex24. A method of manufacturing an inductive heating device, the method comprising: manufacturing an inductor assembly according to Example Ex23, receiving a jacket within the inductor assembly such that the inductor assembly at least partially surrounds the jacket. Example Ex25. A method of manufacturing an inductive heating device, the method comprising: manufacturing a inductor assembly according to Example Ex23, and receiving the inductor assembly within a housing of the inductive heating device such that the housing at least partially surrounds the inductor assembly.

The invention is further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a side cross-sectional view of an inductor assembly according to the present disclosure;

Figure 2 shows an axial cross-sectional view of the inductor assembly of Figure 1 along line 1 -1 ;

Figure 3 shows a side cross-sectional view of an inductive heating device comprising the inductor assembly of Figure 1 according to the present disclosure;

Figure 4 shows an axial cross-sectional view of the inductive heating device of Figure 3 along line 2-2;

Figure 5 shows an exploded perspective view of the inductive heating device of Figures 3 and 4;

Figure 6 shows a further exploded perspective view of the inductive heating device of Figures 3 and 4;

Figures 7A and 7B show a resistive heating element for use in a heater assembly according to the present disclosure;

Figures 8A and 8B show an alternative resistive heating element for use in a heater assembly according to the present disclosure;

Figures 8C and 8D show a further arrangement of a serpentine resistive heating element for use in a heater assembly according to the present disclosure;

Figure 9 shows an assembly step to form part of a jacket according to the present disclosure;

Figure 10 shows a cross-sectional and detailed view of the assembly of part of the jacket according to the present disclosure;

Figure 11 shows a cross-sectional view of a further assembly step to form part of the jacket according to the present disclosure;

Figures 12a-d show cross-sectional views of induction coils according to the present disclosure;

Figure 13 shows a side cross-sectional view of an inductive heating device according to the present disclosure;

Figure 14 shows a side cross-sectional view of an inductive heating system according to the present disclosure; Figure 15 shows a side cross-sectional view of an alternative inductive heating system according to the present disclosure; and

Figure 16 shows a schematic flow diagram illustrating a method of manufacturing an inductor assembly, a heater assembly and an inductive heating device according to the present disclosure.

Figure 1 shows a side cross-sectional view of an inductor assembly 10 according to the present disclosure. In particular, the inductor assembly 10 is an inductor assembly according to the fourth aspect of the present invention. The inductor assembly 10 comprises a cylindrical and hollow sleeve 12 formed from a liquid crystal polymer (LCP). The sleeve 12 defines a sleeve cavity 13. The sleeve 12 and sleeve cavity 13 extend between a proximal end 14 and a distal end 15, defining a longitudinal axis 19 down the centre of the sleeve cavity 13. The sleeve 12 is injection moulded around a first electrical connector 20 and a second electrical connector 21. The first electrical connector 20 and the second electrical connector 21 are therefore embedded within the sleeve 12, and extend parallel to the longitudinal axis 19. The first electrical connector 20 and the second electrical connector 21 comprise exposed ends 24, 25 at the distal end of the sleeve. The exposed ends 24, 25 are configured to be electrically connected to a power supply.

An induction coil 16 is helically would around an outer surface of the sleeve 12. The induction coil 16 is formed from copper. The induction coil 16 comprises a plurality of windings 18. The induction coil 16 is a continuous and flat filament, as each winding 18 of the filament of the induction coil 16 has a thickness perpendicular to the longitudinal axis 19 which is less than a width parallel to the longitudinal axis 19. In other words, the cross-section of each winding 18 is rectangular in shape. The winding axis of the induction coil 16 is the longitudinal axis 19.

A first end of the induction coil 16 is connected to the first electrical connector 20 by an electrical connection 22, for example by soldering the first end of the induction coil 16 to the first electrical connector 20. A second end of the induction coil 16, opposite to the first end, is connected to the second electrical connector 21 by an electrical connection 23, for example by soldering the second end of the induction coil 16 to the second electrical connector 21. The electrical connections 22, 23 are facilitated by holes in the outer surface of the sleeve 12 adjacent to the first and second ends of the induction coil 16.

The induction coil 16 is formed of copper, and the electrical resistance between the first end and the second end of the induction coil is approximately 100 milliohms.

A sleeve insulating layer 30 is wrapped around the sleeve 12 and the induction coil 16 to surround the sleeve 12 and the induction coil 16. The sleeve insulating layer 30 comprises at least one layer, and is formed from a polyimide film, such as Kapton™. Figure 2 shows an axial cross-sectional view of the inductor assembly of Figure 1 along line 1 -1 . The hollow cylindrical shape of the sleeve 12 and the sleeve insulating layer 30 is therefore illustrated. As is illustrated in Figure 2, the first electrical connector 20 comprises a flat filament, as the filament of the first electrical connector 20 has a thickness perpendicular to the longitudinal axis 19 which is less than a width perpendicular to the longitudinal axis 19. The second electrical connector 21 also comprises a flat filament, as the filament of the first electrical connector 21 has a thickness perpendicular to the longitudinal axis 19 which is less than a width perpendicular to the longitudinal axis 19, though this is not illustrated in Figure 2.

Figure 3 shows a side cross-sectional view of a inductive heating device 50 according to the present disclosure. In particular, the inductive heating device 50 is a inductive heating device according to the first aspect of the present invention. The inductive heating device 50 comprises the inductor assembly 10 illustrated in Figures 1 and 2. The inductive heating device 50 further comprises a jacket 60 received within the sleeve cavity 13. The jacket 60 comprises a jacket body formed from a proximal portion 62, a central portion 63 and a distal portion 61 . The proximal portion 62 defines a hollow cylinder which is open at both ends, and is formed from polyether ether ketone (PEEK). The central portion 63 also defines a hollow cylinder which is open at both ends, and is formed from a thermally conductive and electrically insulating ceramic such as alumina or zirconia. The distal portion 61 defines a hollow cylinder which is open only at a proximal end and is closed at a distal end, and is formed from polyether ether ketone (PEEK).

The proximal portion 62 abuts the proximal end 14 of the sleeve cavity 13, and extends towards the distal end 15 of the sleeve cavity 13. The proximal portion 62 is press- fit to the central portion 63. The central portion 63 is press-fit to the distal portion 61 . The distal portion 61 abuts the distal end 15 of the sleeve cavity 13, and extends towards the proximal end 14 of the sleeve cavity 13. Whilst press-fitting of the distal portion 61 , central portion 63 and proximal portion 62 to one-another is described, other forms of attaching such as snap-fitting or tolerance fitting may also be used.

Together as the jacket body, the distal portion 61 , central portion 63 and proximal portion 62 define a central and substantially cylindrical cavity 68 for receiving at least part of an aerosol-generating article. The proximal portion 62 therefore defines a proximal opening for receiving an aerosol-generating article therethrough.

The jacket 60 also defines a plurality of protrusions 69 extending into the cavity 68 from the distal end of the distal portion 61 of the jacket 60. As will be further described below, the plurality of protrusions 69 function to maintain a gap between an end of an aerosolgenerating article and the distal end of the jacket 60 when the aerosol-generating article is fully inserted into the cavity 68. In the embodiment shown in Figures 3 and 4, the jacket 60 defines three protrusions 69 spaced equidistantly about the longitudinal axis 19. The skilled person will appreciate that the jacket 60 may define more or fewer protrusions 69 and the arrangement of the protrusions 69 at the distal end of the jacket 60 may be varied. The plurality of protrusions 69 may be integrally formed with the distal portion 61 .

The jacket 60 further comprises a plurality of grooves or airflow channels 67 extending in a longitudinal direction along the inner surface of the jacket 60. The plurality of grooves 67 are formed on the inner surfaces of the proximal portion 62, the central portion 63, and the distal portion 61 , and are aligned to form continuous grooves 67 extending in a longitudinal direction from the proximal end of the jacket 60 to the distal end of the jacket 60. In order to ensure once connected the inner surfaces of the proximal portion 62, the central portion 63, and the distal portion 61 are aligned to form continuous grooves 67, the proximal portion 62, the central portion 63, and the distal portion 61 may only be connected in a singular relative rotational orientation to one another about the longitudinal axis 19. The longitudinal direction is parallel to the longitudinal axis 19. Each groove 67 extends in a straight line. The plurality of grooves 67 allow for air to flow from the proximal end of the jacket 60 to the distal end of the jacket 60 when the aerosol-generating article is inserted into the cavity 68.

The jacket 60 further comprises a resistive heating element 66. The resistive heating element 66 is arranged on an outer surface of the central portion 63. The resistive heating element 66 is formed from a silver-palladium alloy resistive heating track on a flexible polyimide substrate, as illustrated and described further below with respect to Figures 5A, 5B, 6A and 6B. The resistive heating element 66 is therefore wrapped around the outer surface of the central portion 63 to at least partially surround the cavity 68.

The jacket 60 further comprises an insulating layer 64. The insulating layer 64 surrounds the central portion 63 and the resistive heating element 66, but does not contact the central portion 63 or the resistive heating element 66. Instead, the insulating layer 64 is fixed to the distal portion 61 and the proximal portion 62 to form an insulating zone 65 between the insulating layer 64 and the resistive heating element 66. The insulating layer 64 therefore surrounds only a portion of the distal portion 61 and the proximal portion 62. The insulating zone 65 in this embodiment is filled with an aerogel, though it can be understood that the insulating zone 65 may be filled with any other insulating material such as a polyimide, or filled only with air. The insulating layer 64 comprises at least one layer, and is formed from a polyimide film, such as Kapton™. During manufacturing, the insulating layer 64 is wrapped around the jacket 60, and is glued to the distal portion 61 and the proximal portion 62. The jacket 60 is inserted into the sleeve cavity 13, and is press-fit or snap-fit to the sleeve 10 to form the heater assembly 50. Once assembled, the induction coil 16 surrounds the cavity 68.

Figure 4 shows an axial cross-sectional view of the inductive heating device 50 of Figure 3 along line 2-2. The axial cross-sectional view illustrates the grooves 67 formed on the inner surface of the jacket 60, and the three protrusions 69 extending into the cavity 68 from the distal end of the distal portion 61 of the jacket 60.

Figures 5 and 6 show exploded perspective views of the inductive heating device 50 of Figures 3 and 4. In Figure 5, the sleeve 12 is shown to be injection moulded around the first and second electrical connectors. The second ends 24, 25 of the first and second electrical connectors 20,21 are exposed at the distal end of the sleeve 12. Figure 5 also illustrates the induction coil 16 would on the outer surface of the sleeve 12. The first end of the induction coil 16 is connected to the first end of the first electrical connector 20 through a first hole 28 in the outer surface of the sleeve 12. The second end of the induction coil 16 is connected to the first end of the second electrical connector 21 through a second hole 29 in the outer surface of the sleeve 12. In this embodiment shown, the first end of the induction coil 16 is soldered to the first end of the first electrical connector 20 and the second end of the induction coil 16 is soldered to the first end of the second electrical connector 21 .

The jacket 60 is illustrated in more detail in Figure 6. The proximal portion 62, the central portion 63 and the distal portion 61 of the jacket 60 are shown connected together. The resistive heating element 66 is not illustrated on the central portion 63, but will be illustrated and described in more detail below. The inductor assembly 10 is also illustrated comprising a sleeve insulating layer 30 formed from a polyimide film, such as Kapton™. The sleeve insulating layer 30 is wrapped around the sleeve 12 and the induction coil 16 illustrated in Figure 5.

Figures 7A and 7B show a resistive heating element 66 for use in an inductive heating device 50 according to the present disclosure. In Figure 7A, the resistive heating element 66 is illustrated wrapped around the outer surface of the central portion 63. The resistive heating element 66 comprises a resistive heating track 72 on a flexible polyimide substrate 71 .

The resistive heating track 72 comprises a two parallel filaments, and the resistive heating element 66 is shown in Figure 7B in a flat configuration. The serpentine shape of the resistive heating track 72 is printed onto a polyimide substrate 71 prior to assembly.

This flat resistive heating element 66 is then wrapped around the jacket 60 (not shown) as described above, to form the arrangement as seen in Figures 3 and 4.

The resistive heating track 72 extends from a positive terminal 73 to a negative terminal 74. The positive terminal 73 and the negative terminal 74 are labelled as such as they are configured to be connected to a positive terminal and a negative terminal respectively of control circuitry in an aerosol-generating device when the heater assembly 50 is received in the aerosol-generating device. The total resistance of the resistive heating track 72 between the positive terminal 73 and the negative terminal 74 is approximately 800 milliohms.

The resistive heating track 72 comprises a plurality of parallel and alternating primary and secondary portions 75, 76. The cumulative length of the primary portions 75 is substantially equal to the cumulative length of the secondary portions 76. The primary portions 75 and the secondary portions 76 are integrally formed. Each of the primary portions 75 winds from the positive terminal 73 towards the negative terminal 74 in a clockwise fashion about the cavity 68 when viewed from the proximal end of the jacket 60. Each of the secondary portions 76 winds from the positive terminal 73 towards the negative terminal 74 in an anti-clockwise fashion about the cavity 68 when viewed from the proximal end of the jacket 60. In other words, when a voltage is applied between the positive and negative terminals 73, 74, a current in each of the primary portions 75 flows either clockwise or anticlockwise about the cavity 68 when viewed from the proximal end of the jacket 60. The current in the secondary portions 76 flows in the opposite direction about the cavity 68 when viewed from the proximal end of the jacket 60 compared to the current in the primary portions 76.

Considering an alternating current at a point in time in the induction coil 16 flowing in a clockwise direction when viewed from the proximal end of the heater assembly 50. This alternating current in the induction coil 16 induces a magnetic field in the cavity 68, which in turn induces an alternating current in the resistive heating track 72. The alternating current induced in the resistive heating track 72 is however in the opposite direction to the conventional current at the point in time in the induction coil 16. The alternating current induced in the resistive heating track 72 is therefore flowing in an anti-clockwise direction when viewed from the proximal end of the heater assembly 50 at the point in time. However, the primary portions 75 and the secondary portions 76 of the resistive heating track 72 must be considered separately. The induced current in each of the primary portions 75 flowing in the anti-clockwise direction when viewed from the proximal end of the heater assembly 50 is flowing in a direction from the negative terminal 74 towards the positive terminal 73. Conversely, the induced current in each of the secondary portions 76 flowing in the anticlockwise direction when viewed from the proximal end of the heater assembly 50 is flowing in a direction from the positive terminal 73 towards the negative terminal 74. Because the cumulative length of the primary portions 75 is substantially equal to the cumulative length of the secondary portions 76, there is substantially net zero current induced in the resistive heating track 72, as the sum of the induced currents in the primary portions 75 and the secondary portions 76 cancel each other out. As is illustrated in Figures 7A and 7B, the resistive heating track 72 comprises a plurality of U-shaped portions 77. The U-shaped portions are aligned with the longitudinal axis 19, in that the U-shaped portions are shaped such that the resistive heating track 72 comprises a track portion which extends perpendicular to the longitudinal axis 19 positioned between two track portions which extend parallel to the longitudinal axis 19.

Figures 8A and 8B show a further arrangement of a resistive heating element 66 for use in an inductive heating device 50 according to the present disclosure. The arrangement is similar to that described with respect to Figures 7A and 7B, so will be described with respect to its differences only.

The resistive heating track 72 comprises a single filament arranged in a serpentine shape. The resistive heating track 72 does not comprise any U-shaped portions. The serpentine shape of the resistive heating track 72 is printed onto a polyimide substrate 71 prior to assembly. As shown in Figure 8B, the resistive heating track 72 comprises six alternating primary and secondary portions 75, 76.

Figures 8C and 8D show a further arrangement of a resistive heating element 66 for use in an inductive heating device 50 according to the present disclosure. The arrangement is also similar to that described with respect to Figures 7A and 7B, so will be described with respect to its differences only.

The resistive heating element 72 comprises a single filament arranged in a serpentine shape, shown in Figure 8D in a flat configuration. The resistive heating track 72 does not comprise any U-shaped portions.

As shown in Figures 8C and 8D, the resistive heating element 72 comprises four consecutive track portions arranged along the longitudinal axis of the cavity. The resistive heating element 72 comprises four alternating primary and secondary portions 75, 76.

By including only four consecutive track portions, the distance between two adjacent track portions is increased in comparison to a resistive heating element covering the same surface area and comprising six consecutive track portions, such as that illustrated in Figures 8A and 8B. Consequently, track portions with a greater width may be provided in comparison to the resistive heating element illustrated in Figures 8A and 8B without increasing the likelihood that an unintentional short circuit is created between two adjacent track portions due to inaccuracy when printing or arranging the resistive heating element 72 on the substrate 71 . Wider track portions may be preferable in order to obtain a desired resistance value of the heating element 72, which ultimately determines the heat dissipation in the track.

Figure 9 shows an assembly step to form part of a jacket according to the present disclosure. In particular, Figure 9 shows an assembly step to connect the central portion 63 of the jacket 60 to the distal portion 61 of the jacket 60. The resistive heater 66 is illustrated on the outer surface of the central portion 63. Figure 9 also indicates the direction of force 81 applied to the central portion 63 to connect the central portion 63 to the distal portion 61 .

Figure 10 shows a cross-sectional and detailed view of the assembly of the central portion 63 to the distal portion 61. When the force 81 is applied to the central portion 63, a distal lip 85 at the distal end of the central portion 63 is pressed into a correspondingly shaped recess 86 in the distal portion 61 . The recess 86 and the distal lip 85 are shaped and sized such that the tolerance between the recess 86 and the distal lip 85 ensures a press-fit or tolerance fit between the central portion 63 and the distal portion 61 . The resistive heater 66 is located on the outer surface of the central portion 63 and spaced from the distal lip 85, such that once the central portion 63 and the distal portion 61 are connected, the resistive heater 66 does not contact the distal portion 61 .

Figure 1 1 shows a further assembly step to form part of a jacket according to the present disclosure. In particular, Figure 1 1 shows an assembly step to connect the central portion 63 of the jacket 60 to the proximal portion 62 of the jacket 60. The assembly step is similar to that illustrated in Figures 9 and 10. When a force 83 is applied to the central portion 63, a proximal lip 88 at the proximal end of the central portion 63 is pressed into a correspondingly shaped recess 89 in the proximal portion 62. The recess 89 and the proximal lip 88 are shaped and sized such that the tolerance between the recess 89 and the proximal lip 88 ensures a press-fit or tolerance fit between the central portion 63 and the proximal portion 62. The resistive heater 66 is located on the outer surface of the central portion 63 and spaced from the proximal lip 88, such that once the central portion 63 and the proximal portion 62 are connected, the resistive heater 66 does not contact the proximal portion 62.

Figures 9 to 1 1 illustrate press or tolerance fitting between the central portion 63 and the distal portion 61 , and the central portion 63 and the proximal portion 62. However, it is understood by the skilled person that other forms of connection may be implemented to connect the central portion 63 and the distal portion 61 , and the central portion 63 and the proximal portion 62. Foe example, snap-fitting.

Figures 9 to 11 do not illustrate continuous grooves on the inner surface of the jacket from the distal end to the proximal end of the jacket. However, it is understood by the skilled person that such continuous grooves on the inner surface of the jacket may be implemented, as is illustrated in Figures 1 to 4.

Figure 12a-d shows cross-sectional views of induction coils 16 according to the present disclosure. In the embodiment of Figure 12a, the induction coil 16 comprises a wire material 6 having a rectangular cross-section. The induction coil 16 comprises an electrically conductive coating which is evenly applied around the wire material 6. In an embodiment, wire material 6 is made of copper, whereas the electrically conductive coating 8 is made of silver. Figure 12b, shows an embodiment similar to that in Figure 12a, however the thickness of the electrically conductive coating is greater on the longitudinal ends than the lateral ends of the wire material cross-section. As mentioned in relation to the first aspect, this is advantageous since the current density at the operational frequency of the induction coil 16 will be higher around the longitudinal ends of the induction coil. Figure 12c shows an embodiment in which no electrically conductive coating is applied to the lateral ends of the wire material cross-section. Figure 12d shows an embodiment in which the cross-section of the wire material 6 has an ellipse shape. In this embodiment, a thicker electrically conductive coating 8 is applied around the longitudinal ends of the ellipse where the current density will be greatest. It will be appreciated that any of the induction coil embodiments disclosed in Figures 12a-d may be implemented into any of the inductor assemblies or inductive heating devices of the disclosure.

Figure 13 shows a side cross-sectional view of an inductive heating device 100 according to the present disclosure. In particular, the inductive heating device 100 is also an inductive heating device according to the first aspect of the present invention.

The inductive heating device 100 comprises a housing 101 , within which the inductive heating device 50 as illustrated in Figures 3 and 4 is received such that the housing 101 at least partially surrounds the inductive heating device 50. The proximal end of the cavity 68 is open to the outside of the inductive heating device 100, in order to receive an aerosolgenerating article.

The inductive heating device 100 also comprises control circuitry 102 and a power supply 103. The power supply 103 is electrically connected to the induction coil 16 and to the resistive heating element 66 via the control circuitry 102. The electrical connection between the resistive heating element 66 and the control circuitry 102 is not illustrated for clarity purposes.

The power supply 103 comprises a DC power supply, and preferably a battery, such as a lithium-ion battery. As an alternative, the power supply 103 may be another form of charge storage device, such as a capacitor. The power supply 103 may require recharging. For example, the power supply 103 may have sufficient capacity to allow for the continuous generation of aerosol from an aerosol-generating article for a period of around six minutes or for a period that is a multiple of six minutes.

The control circuitry 102 is configured to provide a direct electric current from the power supply 103 to the resistive heating element 66 to generate heat in the resistive heating element 66 by Joule, or resistive, heating. The control circuitry 102 is configured to provide a direct electric current from the power supply 103 to the resistive heating element 66 to heat the resistive heating element 66 to at least 80°C. The resistive heating element 66 is therefore configured to externally heat the cavity 68, as heat is provided to the cavity 68 from a location outside the cavity 68. The control circuitry 102 is also configured to provide an alternating electric current from the power supply 103 to the induction coil 16 to generate an alternating magnetic field within the cavity 68. As the power supply 103 comprises a DC power supply, the control circuitry comprises a DC/ AC converter in order to provide an alternating electric current from the DC power supply to the induction coil 16. The DC/ AC converter preferably comprises a Class-E power amplifier. The DC/AC converter is configured to supply the induction coil 16 with a high frequency alternating current. As used herein, the term "high frequency alternating current" means an alternating current having a frequency of between about 500 kilohertz and about 30 megahertz. The high frequency alternating current may have a frequency of between about 1 megahertz and about 30 megahertz, such as between about 1 megahertz and about 10 megahertz, or such as between about 5 megahertz and about 8 megahertz.

The control circuitry 102 comprises a microcontroller, preferably a programmable microcontroller. The microcontroller is programmed to regulate the supply of power from the power supply 103 to the induction coil 16 via the DC/AC converter, and to the resistive heating element 66, in order to control the temperature of the resistive heating element 66 and the temperature of a susceptor element heated by the induction coil 16.

In particular, the microcontroller is configured to regulate the supply of power from the power supply 103 to the induction coil 16 via the DC/AC converter in order to follow a pre-determined inductive heating profile by using pulse-width modulation. The control circuitry 102 is further configured to provide an inductive heating feedback signal from the induction coil 16 to the microcontroller in order to follow the pre-determined inductive heating profile. The microcontroller is also configured to regulate the supply of power from the power supply 103 to the resistive heating element 66 in order to follow a pre-determined resistive heating profile by using pulse-width modulation. The control circuitry 102 is further configured to provide a resistive heating feedback signal from the resistive heating element 66 to the microcontroller in order to follow the pre-determined resistive heating profile. The reduction in the induced alternating current in the resistive heating element 66 reduced the noise in the resistive heating feedback signal, allowing for the microcontroller to more precisely follow the pre-determined resistive heating profile.

Figure 14 shows a side cross-sectional view of an aerosol-generating system 200 according to the present disclosure. In particular, the aerosol-generating system 200 is an aerosol-generating system according to the second aspect of the present invention.

The aerosol-generating system 200 comprises the inductive heating device 100 illustrated and described with respect to Figure 13. The aerosol-generating system 200 further comprises an aerosol-generating article 300 received in the cavity 68. The aerosol-generating article 300 comprises an aerosol-forming substrate 304 in the form of a tobacco plug, a first hollow acetate tube 306, a second hollow acetate tube 308, a mouthpiece 310, and an outer wrapper 312. The aerosol-generating article 300 also comprises a susceptor element 314 arranged within the aerosol-forming substrate 304. During use, a portion of the aerosol-generating article 300 is inserted into the cavity 68 so that the aerosol-forming substrate 304 and the susceptor element 314 are positioned inside the cavity 68 and are surrounded by the induction coil 16 and the resistive heating element 66. The control circuitry 102 provides an alternating electric current from the power supply 103 to the induction coil 16 to generate an alternating magnetic field that inductively heats the susceptor element 314, which heats a central zone of the aerosol-forming substrate 304 to generate an aerosol. The level of inductive coupling between the induction coil 16 and the susceptor element 314, and consequently, the heating of the susceptor 314, is dependent on the frequency of the alternating current supplied to the induction coil 16. The control circuitry 102 also provides a direct electric current from the power supply 103 to the resistive heating element 66 to generate heat in the resistive heating element 66 by Joule, or resistive, heating. The heat from the resistive heating element 66 travels through the central portion 63 to a peripheral zone of the aerosol-forming substrate 304, which heats the peripheral zone of the aerosol-forming substrate 304 to generate an aerosol.

Airflow through the aerosol-generating system 200 during use is illustrated by the dashed line 316 in Figure 14. When a user draws on the mouthpiece 310 of the aerosolgenerating article 300, a negative pressure is generated in the cavity 68. The negative pressure draws air into the cavity 68 via the open end of the cavity. The air entering the cavity 68 then flows through the plurality of grooves 67 defined in the inner wall of the jacket 60. When the airflow reaches the distal end of the cavity 68, the air enters the aerosolgenerating article 300 through the aerosol-forming substrate 304. Airflow into the aerosolgenerating article 300 is facilitated by the gap maintained between the distal end of the aerosol-generating article 300 and the distal end of the cavity 68 by the plurality of protrusions 69. As the airflow passes through the aerosol-forming substrate 304, aerosol generated by heating of the aerosol-forming substrate 304 is entrained in the airflow. The aerosol then flows along the length of the aerosol-generating article 300 and through the mouthpiece 310 to the user.

Figure 15 shows a side cross-sectional view of an alternative aerosol-generating system 200 according to the present disclosure. In particular, the aerosol-generating system 200 is also an aerosol-generating system according to the second aspect of the present invention. The alternative aerosol-generating system 200 is similar to the aerosol-generating system 200 shown in Figure 14, so will be described with respect to its differences only. Airflow through the aerosol-generating system 200 during use is again illustrated by the dashed line 316 in Figure 15. When a user draws on the mouthpiece 310 of the aerosolgenerating article 300, rather than the air flowing through a plurality of grooves 67 defined in the inner wall of the jacket 60, the air instead flows through a heater assembly airflow pathway. The heater assembly airflow pathway comprises a sleeve airflow pathway 317 extending between a sleeve air inlet and a sleeve air outlet. The sleeve airflow pathway 317, sleeve air inlet and sleeve air outlet are all defined in the sleeve 12 of the heater assembly 50. The heater assembly airflow pathway further comprises a jacket airflow pathway 318 extending between a jacket air inlet and a jacket air outlet. The jacket airflow pathway 318, jacket air inlet and jacket air outlet are all defined in the distal portion 61 of the jacket 60 of the heater assembly 50. The sleeve air inlet is defined in an outer surface of the housing 101. The sleeve air outlet is directly adjacent to and in fluid communication with the jacket air inlet. The jacket air inlet is defined in the inner surface of the distal portion 61 of the jacket 60, and is in fluid communication with the cavity 68. Therefore, when a user draws on the mouthpiece 310 of the aerosol-generating article 300, the air flows into the sleeve air inlet, through the sleeve airflow pathway 317, followed by the jacket airflow pathway 318, and into the distal end of the cavity 68. The airflow through the aerosol-generating article 300 is then identical to that described with respect to Figure 14.

The jacket 60 therefore does not comprise any grooves 67 defined in the inner wall of the jacket 60. Rather, the inner surface of the jacket 60 is a smooth cylinder. The aerosolgenerating article 300 therefore is received tightly within the cavity 68 and contacts the inner surface of the jacket 60 continuously around the circumference of the aerosol-generating article 300. This improves thermal transfer of heat from the resistive heating element via the central portion 63 to the aerosol-forming substrate 304.

Although in Figures 14 and 15, the susceptor element 314 is illustrated as a component part of the aerosol-generating article 300, it can be understood that instead, or additionally, the inductive heating device 100 may comprise one or more susceptor elements configured to be heated by the induction coil 16. Such one or more susceptor elements may be provided in the cavity 68 in the form of blades or needles or pins. For example, the one or more susceptor elements may be provided at the distal end of the jacket 60 extending parallel to the longitudinal axis 19 towards the proximal end of the jacket 60. Such one or more susceptor elements may be configured to penetrate the aerosol-forming substrate 304 when the aerosol-generating article 300 is received within the cavity 68.

Figure 16 shows a schematic flow diagram illustrating a method of manufacturing an inductor assembly 10, a inductive heating device 50 and an inductive heating device 100 according to the present disclosure. The illustrated method comprises in a first step 1001 injection moulding the sleeve 12 around the first electrical connector 20 and the second electrical connector 21. The injection moulding results in the second ends 24, 25 of the first electrical connector and the second electrical connector exposed at the distal end 15 of the sleeve 12. The injection moulding also results in the first electrical connector 20 and the second electrical connector 21 being exposed to the outer surface of the sleeve 12 through holes 28, 29 in the outer surface of the sleeve 12.

In a second step 1002, an electrically conductive coating 8 is applied to a wire material 6 having an elongate cross-section in order to form an induction coil 16. The induction coil 16 is wound around the outer surface of the sleeve 12 and secured to the first electrical connector 20 and the second electrical connector 21 . The first end of the induction coil 16 is soldered to the first end of the first electrical connector 20 through the first hole 28 in the outer surface of the sleeve 12. The second end of the induction coil 16 is soldered to the first end of the second electrical connector 21 through the second hole 29 in the outer surface of the sleeve 12.

In a third step 1003, the sleeve 12 and induction coil 16 are wrapped in at least one layer of polyimide film, such as Kapton™, and is secured in place with adhesive between the polyimide film and the proximal portion 62, and between the polyimide film and the distal portion 61. This third step 1003 forms the inductor assembly 10 according to the present disclosure.

In a fourth step, 1004, the proximal portion 62 is press-fit or snap-fit to the central portion 63, and the central portion 63 is press-fit or snap-fit to the distal portion 61 to form part to the jacket 10. The fourth step 1004 may take place prior to, during, or after any of the first three steps 1001 , 1002, 1003. This therefore allows the jacket 60 to be manufactured separately to the inductor assembly 10.

In a fifth step 1005, the resistive heating element 66 is arranged on the outer surface of the central portion 63, and is co-fired to secure the resistive heating element 66 to the outer surface of the central portion 63.

In a sixth step 1006, at least one layer of polyimide film 64, such as Kapton™, is wrapped around the central portion 63 to surround the central portion 63 and to partially surround the proximal portion 62 and the distal portion 61 . The at least one layer of polyimide film 64 is secured to the proximal portion 62 and the distal portion 61 by two circumferential strips of glue. The radial dimensions of the proximal portion 62 and the distal portion 61 relative to the central portion 63 ensure that the at least one layer of polyimide film 64 does not contact the resistive heating element 66 on the central portion 63, and an insulating zone 65 is formed between the at least one layer of polyimide film 64 and the resistive heating element 66. This step forms the jacket 60 according to the present disclosure. In this manufacturing embodiment, the insulating zone 65 is an air gap. The skilled person would however understand that the insulating zone 65 may be filled with a thermal insulator such as polyimide or aerogel prior wrapping the at least one layer of polyimide film 64 around the central portion 63.

In a seventh step 1007, the jacket 60 manufactured in the sixth step 1006 is received within the inductor assembly 10 formed in the third step 1003. The jacket 60 is snap-fit to securely connect to the inductor assembly 10 via corresponding snap-fit protrusions on the distal potion 61 and the sleeve 12. This seventh step 1007 forms the inductive heating device 50 according to the present disclosure.

In an eighth step 1008, the inductive heating device 50 is received within a housing 101 of an inductive heating device 100 such that the housing 101 at least partially surrounds the inductive heating device 50. The inductive heating device 50 is snap-fit to securely connect to the housing 101 via corresponding snap-fit protrusions on the sleeve 12 and the housing 101. The second ends 24,25 of the first and second electrical connectors 20,21 are electrically connected to the control circuitry 102, as is illustrated in Figure 13. The resistive heating element 66 is also electrically connected to the control circuitry 102. This eighth step 1008 forms the inductive heating device 100 according to the present disclosure.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number “A” is understood as “A” ± 10% of “A”. Within this context, a number “A” may be considered to include numerical values that are within general standard error for the measurement of the property that the number “A” modifies. The number “A,” in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which “A” deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

1 . An inductive heating device for an aerosol-generating system, the device comprising: a heater assembly defining a cavity having an internal surface for receiving at least a portion of an aerosol-forming insert comprising an aerosol-forming substrate and a susceptor, the heater assembly comprising an induction coil having a magnetic axis and arranged to surround at least a portion of the cavity; wherein a wire material forming the induction coil has a cross-section comprising a main portion, the main portion having a longitudinal extension in a direction of the magnetic axis and a lateral extension perpendicular to the magnetic axis, wherein the longitudinal extension is longer than the lateral extension of the main portion, wherein the wire material comprises an electrically conductive coating.

2. An inductive heating device according to claim 1 , wherein the electrically conductive coating has a higher electrical conductivity than the wire material.

3. An inductive heating device according to any preceding claim, wherein the electrically conductive coating has a higher resistance to oxidation than the wire material.

4. An inductive heating device according to any preceding claim, wherein the electrically conductive coating has a maximum thickness within the range of 0.5-100pm.

5. An inductive heating device according to claim 4, wherein the electrically conductive coating has a maximum thickness of less than 30pm.

6. An inductive heating device according to any preceding claim, wherein the main portion comprises two opposing longitudinal ends and two opposing lateral ends, wherein the thickness of the electrically conductive coating around regions of the main portion wherein the longitudinal ends meet the lateral ends is greater than the thickness of the electrically conductive coating at other regions of the main portion.

7. An inductive heating device according to any of claims 1 to 5, wherein the main portion comprises two opposing longitudinal ends and two opposing lateral ends, wherein the thickness of the electrically conductive coating is greater on the longitudinal ends than on the lateral ends of the main portion.

8. An inductive heating device according to claim 7, wherein there is no electrically conductive coating on the lateral ends of the main portion.

9. An inductive heating device according to any preceding claim, wherein the electrically conductive coating comprises at least one of silver or gold.

10. An inductive heating device according to any preceding claim, wherein the device further comprises: a power source connected to the induction coil and configured to provide a high frequency current to the induction coil; and a device housing containing the heating assembly and the power source.

11 . An inductive heating device according to any preceding claim, wherein the main portion forms the entire cross-section of the wire material.

12. An inductive heating device according to any of claims 1 to 10, wherein the crosssection of the wire material further comprises a secondary portion, the secondary portion having a longitudinal extension in the direction perpendicular to the magnetic axis and a lateral extension in the direction of the magnetic axis, which longitudinal extension is longer than a lateral extension of the secondary portion.

13. An inductive heating device according to any preceding claim, wherein the heater assembly comprises: a jacket lining at least a portion of the inner surface of the cavity for heating an aerosol-generating article received within the cavity, and a sleeve at least partially surrounding the jacket, wherein the induction coil is coupled to the sleeve.

14. An aerosol-generating system comprising: an inductive heating device according to any preceding claim; and an aerosol-generating article comprising an aerosol-generating substrate, wherein the aerosol-generating article is received in the cavity of the inductive heating device.

15. A heater assembly for an aerosol-generating device, the inductor assembly comprising: a sleeve configured for internally receiving a jacket for carrying an aerosol-generating article, and an induction coil coupled to the sleeve, wherein a wire material of the induction coil comprises an elongate cross-section, wherein the wire material comprises an electrically conductive coating.

16. A method of manufacturing a heater assembly for an aerosol-generating device, the method comprising: providing an induction coil comprising a wire material having an elongate crosssection; applying an electrically conductive coating to the wire material; providing a sleeve, and coupling the induction coil to the sleeve.