RU2837105C1 - Aerosol-generating device for generating aerosol by induction heating of aerosol-forming substrate and method of producing aerosol-generating device flow concentrator multilayer foil - Google Patents

Abstract

FIELD: smoking accessories.

SUBSTANCE: group of inventions relates to aerosol-generating devices. Device comprises a housing comprising a cavity configured to receive an aerosol-forming substrate to be heated, induction heating structure containing at least one inductance coil for generation of variable magnetic field inside cavity, flux concentrator. Inductance coil is located around at least a portion of the cavity. Flux concentrator is located around at least a section of the inductance coil and is configured to distort the varying magnetic field of at least one induction heating structure in the direction of the cavity during use of the device. Flow concentrator comprises a multilayer foil having at least one magnetic layer forming a layered structure with at least the first support layer and containing a plurality of separate fragments from a soft magnetic alloy. Plurality of separate fragments are arranged in the form of a pattern containing a plurality of cracking centres, wherein plurality of cracks extends radially outward from each centre of cracking in form of cobweb-like pattern.

EFFECT: providing reliability, compactness of the flow concentrator, ease of manufacture, reduced heating, more efficient use of energy for heating the substrate.

15 cl, 18 dwg

Description

The present invention relates to an aerosol generating device for generating an aerosol by inductively heating an aerosol-forming substrate, wherein the device comprises a flow concentrator foil. The present invention further relates to an aerosol generating system comprising such a device and an aerosol generating article comprising an aerosol-forming substrate to be heated. Furthermore, the present invention relates to a method for producing a multilayer flow concentrator foil in such a device.

Aerosol-generating systems for inductively heating aerosol-forming substrates capable of forming inhalable aerosols are well known in the art (see, for example, publications WO 2020/074622 A1 and RU 2670060 C2). Such systems may comprise an aerosol-generating device having a cavity for receiving a substrate to be heated. The substrate may be an integral part of an aerosol-generating article that is designed to be used with said device. To heat the substrate, the device may comprise an inductive heating structure that includes an induction coil for generating an alternating magnetic field inside said cavity. Said field is used to create heat-generating eddy currents or hysteresis losses in a current collector, which, when the system is used, is in thermal proximity to the substrate to be heated or in direct physical contact with it. In general, the current collector can be either an integral part of the device or an integral part of the product.

The magnetic field may not only cause induction heating of the current collector, but also affect other current-receiving parts of the aerosol-generating device or current-receiving external objects located in the immediate vicinity of the device. In order to reduce such undesirable effects, the aerosol-generating device may be equipped with a flux concentrator, which is located around the induction heating structure and acts essentially in such a way that it localizes the magnetic field generated by the heating structure within the volume surrounded by the flux concentrator. However, it has been found that the localization effect often decreases or even disappears when the device is subjected to excessive force effects or impacts, for example, as a result of an accidental drop of the device. In addition, many flux concentrators are quite bulky and, thus, they can significantly increase the overall mass and size of the aerosol-generating device. In addition, it has been noted that the magnetic flux concentrator itself undesirably heats up during use of the device, in particular when operating the device with changing magnetic fields in the megahertz range.

It would therefore be desirable to have an aerosol generating device and system for inductively heating an aerosol-forming substrate with the advantages of the prior art solutions but with the mitigation of their limitations. In particular, it would be desirable to have an aerosol generating device and system comprising a flow concentrator that would have improved reliability and a compact design but would heat up less when the device is used.

According to an aspect of the present invention, an aerosol generating device is proposed for generating an aerosol by inductively heating an aerosol-forming substrate. The device comprises a device casing comprising a cavity configured to removably accommodate an aerosol-forming substrate to be heated therein. The device further comprises an inductive heating structure comprising at least one inductance coil for generating an alternating magnetic field inside said cavity, wherein said inductance coil is located around at least a portion of the receiving cavity. In addition, the device comprises a flux concentrator located around at least a portion of the inductance coil and configured to distort the alternating magnetic field of the inductive heating structure in the direction of said cavity during use of the device. The flux concentrator comprises a multilayer flux concentrator foil having at least one magnetic layer forming a layered structure with at least a first support layer, wherein the magnetic layer comprises a plurality of individual fragments of a soft magnetic alloy.

According to the present invention, it has been found that a flow concentrator that comprises a flow concentrator foil or is made of it is more flexible than other flow concentrator configurations, such as ferrite solids. Due to this, the flow concentrator foils provide good shock-absorbing properties and are thus able to withstand more powerful force effects or impacts without damage. For example, compared to current collectors made of sintered ferrite powder, a flexible flow concentrator foil has a significantly better resistance to impact loads, such as those created as a result of an accidental fall. In addition, the flow concentrator foils make it possible to obtain a more compact design of the aerosol generating device due to their small dimensions. In particular, compared to sintered ferrite flow concentrators, the flow concentrator foils make it possible to manufacture them significantly thinner. In addition, in contrast to solid flow concentrators, the flow concentrator foils also make it possible to compensate for manufacturing tolerances, as well as fine-tune the inductance. In particular, the flux concentrator foil can advantageously contribute to increasing the stability of the total resistance of the inductor depending on the temperature. In general, the total resistance of the inductor is affected by the presence of the flux concentrator. When using the flux concentrator foil, it is possible to have a smaller change in the conductivity of the induction heating system depending on the temperature, due to the small volume of the foil, in particular, compared to flux concentrators based on a large volume solid. Due to this, it is also possible to have a smaller change in the total resistance depending on the temperature. In addition, flux concentrator foils are easy to manufacture.

Most importantly, since the magnetic layer comprises a plurality of individual fragments, the generation of eddy currents in the magnetic layer is partially suppressed due to the fact that each individual fragment provides only a limited space for the generation of eddy currents. In other words, compared to an unfragmented magnetic layer, a fragmented magnetic layer has a reduced resistance to alternating current. As a result, there is no or only a small amount of energy dissipation in said fragments, which results in the flow concentrator foil as a whole being heated only slightly, if at all. In this way, it is possible that the majority of the energy provided by the changing magnetic field will be dissipated in the current collector and thereby effectively used to heat the aerosol-forming substrate in said cavity.

As used in this document, the term "concentrate a magnetic field" means that the flux concentrator is capable of distorting a magnetic field in such a way that the magnetic field density increases within the specified cavity.

By distorting the magnetic field in the direction of the said cavity, the flux concentrator reduces the degree of magnetic field propagation beyond the inductance coil. In other words, the flux concentrator acts as a magnetic screen. This provides the possibility of reducing the unwanted heating of adjacent current-receiving parts of the device, for example, the metal outer casing, or unwanted heating of adjacent current-receiving objects external to the device. Due to the reduction of unwanted losses during heating, the possibility of additionally increasing the efficiency of the aerosol-generating device is provided.

In addition, due to the distortion of the magnetic field in the direction of said cavity, the flow concentrator can advantageously provide concentration or focusing of the magnetic field inside said cavity. This provides the possibility of increasing the amount of heat generated in the current collector at a given level of power passed through the induction coil, compared to induction coils that do not have a flow concentrator. In this way, the efficiency of the aerosol generating device can be increased.

The term "foil" as used herein refers to a thin sheet material, the thickness of which is much less than its dimension in any direction perpendicular to the thickness direction. The term "thickness" as used herein refers to the dimension of the foil perpendicular to the main surfaces of the foil. The flow concentrator foil may have a thickness in the range of 0.02 millimeters to 0.25 millimeters, in particular from 0.05 millimeters to 0.2 millimeters, preferably from 0.1 millimeters to 0.15 millimeters. For example, the flow concentrator foil may have a thickness of 62 micrometers. The flow concentrator foil may have a thickness of no more than 150 micrometers, in particular no more than 100 micrometers, preferably no more than 80 micrometers. Such thickness values make it possible to obtain a particularly compact design of the aerosol generating device. However, these values are still large enough to sufficiently distort the alternating magnetic field of the induction heating structure in the direction of the said cavity during use of the device.

The thickness of the flow concentrator may be substantially constant along any direction perpendicular to the thickness of the flow concentrator. In other examples, the thickness of the flow concentrator may vary along one or more directions perpendicular to the thickness of the flow concentrator. For example, the thickness of the flow concentrator may gradually decrease or taper from one end to the other end or from the central portion of the flow concentrator toward both ends. The thickness of the flow concentrator may be substantially constant along its circumference. In other examples, the thickness of the flow concentrator may vary along its circumference.

The magnetic layer may have a layer thickness in the range of 15 micrometers to 100 micrometers, in particular from 18 micrometers to 40 micrometers, for example 20 micrometers. The magnetic layer may have a layer thickness of a maximum of 100 micrometers, in particular a maximum of 50 micrometers, preferably a maximum of 40 micrometers. The magnetic layer may have a layer thickness of a maximum of 75%, in particular 50%, more particularly at least 40%, preferably at least 35%, of the thickness of the flow concentrator foil.

As an advantage, the first support layer serves to bind and support the fragments, forming a layered structure with the first support layer. Preferably, the multilayer foil of the flux concentrator can further comprise a second support layer on that side of said at least one magnetic layer or, as will be further described below, on that side of said plurality of adjacent magnetic layers, which is opposite to the first support layer. Like the first support layer, the second support layer preferably forms a layered structure with said at least one magnetic layer or, if applicable, with said plurality of adjacent magnetic layers. As an advantage, the second layer is also used to bind and support the fragments.

At least one of the first support layer and, if present, the substrate of the second support layer may comprise a polymer foam. The polymer film may be selected from polyesters, polyimides, polyolefins or combinations thereof. The substrate may comprise a cover film. Preferably, at least one of the first support layer and, if present, the second support layer may be one of an adhesive layer, an electrically insulating layer or an electrically insulating adhesive layer. The use of an electrically insulating adhesive layer advantageously ensures the prevention of short-circuiting of fragments within said at least one magnetic layer or, if applicable, said plurality of adjacent magnetic layers located adjacent to the first or second support layer, respectively.

The first support layer and, if present, the second support layer may be an edge layer of the multilayer flow concentrator foil, i.e., one of the two outermost layers of the multilayer flow concentrator foil.

As used in this document, the term "magnetic" means either ferromagnetic or ferrimagnetic. In other words, a soft magnetic alloy is either ferromagnetic or ferrimagnetic.

As used herein, the term "soft magnetic alloy" refers to a magnetic alloy that has a low magnetic coercivity, in particular a magnetic coercivity of maximum 100 A/m (ampere/meter), preferably maximum 50 A/m (ampere/meter), more preferably maximum 10 A/m (ampere/meter), most preferably maximum 5 A/m (ampere/meter). Magnetic coercivity is a measure of the ability of a magnetic material to withstand an external magnetic field without demagnetization. Due to the low magnetic coercivity, soft magnetic alloys have the advantage of low hysteresis losses.

Preferably, the soft magnetic alloy is brittle. This provides an advantage against cracking of the soft magnetic alloy into many individual fragments.

The soft magnetic alloy of the flux concentrator may comprise any material or combination of materials suitable for distorting the magnetic field, or it may be made from these materials.

Preferably, the soft magnetic alloy may be a metallic glass (amorphous metal) or a nanocrystalline soft magnetic alloy, in particular a nanocrystalline Fe-based soft magnetic alloy.

In particular, the soft magnetic alloy of the flux concentrator foil may be or contain a composition of Fe _100-abcxyz Cu _a M _b T _c Si _x Z _z and up to 0.5 atomic % of contaminants, where M is one or more from the group consisting of Nb, Mo and Ta; T is one or more from the group consisting of V, Cr, Co and Ni; Z is one or more from the group consisting of C, P and Ge; 0.5 atomic % < a < 1.5 atomic %; 2 atomic % b<4 atomic %; 0 atomic % <c<5 atomic %; 12 atomic %<x<18 atomic %; 5 atomic %<y<12 atomic %; and 0 atomic % <z<2 atomic%.

For example, the soft magnetic alloy of the flux concentrator foil may comprise or be made from an alloy available under the trade name Vitrovac® or Vitroperm® from VACUUMSCHMELZE GmbH & Co. KG, Germany. Vitroperm® alloys are nanocrystalline soft magnetic alloys. For example, the flux concentrator foil may comprise or be made from Vitroperm 220, Vitroperm 250, Vitroperm 270, Vitroperm 400, Vitroperm 500 or Vitroperm 800. In particular, the soft magnetic alloy may be or contain a composition of Fe _73.8 Nb ₃ Cu ₁ Si _15.6 B6.6. This composition corresponds to Vitroperm 800.

The term "flux concentrator" as used herein refers to a component that has a high relative magnetic permeability and serves to concentrate and direct the magnetic field or magnetic field lines generated by the inductor. The term "high relative magnetic permeability" as used herein refers to a relative magnetic permeability of at least 100, in particular at least 1000, preferably at least 10000, even more preferably at least 50000, most preferably at least 80000. These exemplary values refer to maximum values of relative magnetic permeability at frequencies up to 50 kHz at a temperature of 25 degrees Celsius. The term "relative magnetic permeability" refers to the ratio of the magnetic permeability of a material or a medium, such as a flux concentrator, to the magnetic permeability of free space μ_0, where μ_0 is 4π⋅10 ^-7 N⋅A ^-2 (4⋅Pi⋅10E-07 newtons per square ampere). Accordingly, the soft magnetic alloy has a relative magnetic permeability of at least 100, in particular at least 1000, preferably at least 10000, even more preferably at least 50000, most preferably at least 80000. These values preferably relate to the maximum values of the relative magnetic permeability at frequencies of up to 50 kHz at a temperature of 25 degrees Celsius.

As will be described in more detail below with respect to the method according to the present invention, the fragmented magnetic layer can be obtained from a multilayer flux concentrator foil having at least one magnetic layer made of a soft magnetic alloy forming a layered structure with at least a first support layer, wherein the magnetic layer is subjected to cracking into a plurality of individual fragments. Cracking of the magnetic layer can be achieved, for example, by applying an external force to the flux concentrator foil perpendicular to the plane of the foil. Although the magnetic layer cracks into a plurality of fragments, the first support layer and, if present, the second support layer remain intact and do not crack into fragments in order to hold the fragmented magnetic layer as a single whole.

Depending on the tools and method used to crack the magnetic layer into fragments, said plurality of individual fragments may be arranged in a pattern containing a plurality of cracking centers, with the plurality of cracks extending radially outward from each cracking center in a web-like pattern.

In addition, depending on the tools and method used, the fragments may have different shapes. For example, the fragments may have a flaky shape.

Preferably, each individual fragment may have a fragment size of maximum 1 millimeter, in particular maximum 750 micrometers or maximum 500 micrometers. Likewise, said plurality of individual fragments may have an average fragment size of maximum 1 millimeter, in particular not maximum 750 micrometers or maximum 500 micrometers. Such fragment size values provide the possibility of an enhanced reduction in the alternating current resistance of the magnetic layer and, thus, an enhanced reduction in eddy current losses in the flux concentrator foil.

In general, the multilayer flux concentrator foil may comprise a single (one) magnetic layer. It is also possible that the multilayer flux concentrator foil comprises a plurality of adjacent magnetic layers. Said plurality of adjacent magnetic layers provide the possibility of improving the flux concentrating effect. In addition, the use of a foil having a plurality of adjacent magnetic layers provides the possibility of reducing the labor costs for placing the flux concentrator foil around the inductor coil, since one turn of the multilayer flux concentrator foil of the magnetic layer provides the possibility of achieving the same effect as in the case of the flux concentrator foil of the magnetic layer located around the inductor coil in the form of a plurality of turns on top of each other.

With regard to the flow concentrator foil comprising a plurality of adjacent magnetic layers, the multilayer flow concentrator foil may comprise an adhesive film, in particular an electrically insulating adhesive film, which is located between each two adjacent magnetic layers. As an advantage, the adhesive film serves to bind and support a plurality of fragments of different magnetic layers. The use of an electrically insulating adhesive film makes it possible to prevent short-circuiting of fragments within one magnetic layer or adjacent layers via the adhesive film. The adhesive film located between each two adjacent magnetic layers may also be called an intermediate support layer. In other words, the flow concentrator foil may also comprise at least one intermediate support layer. The intermediate support layer may be located between two adjacent magnetic layers. Further details will be described below with respect to the method according to the present invention, and they are equally applicable to the aerosol generating device according to the present invention described in this document.

For example, a multilayer flow concentrator foil may contain the following layers (from bottom to top):

adhesive (polyethylene terephthalate-free) first support layer,

a first magnetic layer comprising or made from a soft magnetic alloy,

adhesive (polyethylene terephthalate-free) intermediate support layer,

a second magnetic layer comprising or made from a soft magnetic alloy, and

second adhesive (based on polyethylene terephthalate) support layer.

As will be described in more detail below, the multilayer flow concentrator foil may be a sealed multilayer flow concentrator foil. In other words, the multilayer flow concentrator foil may be sealed to prevent fragments from being released from the foil in the transverse direction. For this purpose, a sealing adhesive tape may be arranged on one or each side of the (unsealed) flow concentrator foil, the width of which in the direction perpendicular to the opposite (cut) edges of the flow concentrator foil is greater than the width of the unsealed flow concentrator foil in the same direction, i.e. in the direction perpendicular to the opposite cut edges of the (unsealed) flow concentrator foil. As a result, the sealing adhesive tape on each side of the (unsealed) flow concentrator foil comprises transversely projecting flaps that can come into adhesive contact with each other in such a way as to seal the edges of the (unsealed) flow concentrator. For example, a sealed multilayer flow concentrator foil may comprise the following layers (from bottom to top):

a first three-layer adhesive sealing layered structure comprising a film (based on polyethylene naphthalate or polyimide) located between a first adhesive layer and a second adhesive layer,

an adhesive (non-polyethylene terephthalate) first support layer, a first magnetic layer comprising or made from a soft magnetic alloy,

adhesive (polyethylene terephthalate-free) intermediate support layer,

a second magnetic layer containing or made from a soft magnetic alloy,

the second adhesive (based on polyethylene terephthalate) support layer, and

a second three-layer adhesive sealing layered structure comprising a film (based on polyethylene naphthalate or polyimide) located between the first adhesive layer and the second adhesive layer.

In another example, a sealed multilayer flow concentrator foil may contain the following layers (from bottom to top):

the first adhesive film based on polyethylene terephthalate,

adhesive (polyethylene terephthalate-free) first support layer,

a first magnetic layer comprising or made from a soft magnetic alloy,

adhesive (polyethylene terephthalate-free) intermediate support layer,

a second magnetic layer containing or made from a soft magnetic alloy,

the second adhesive (based on polyethylene terephthalate) support layer and

the second adhesive film based on polyethylene terephthalate.

The first and second three-layer adhesive sealing layer structures may comprise a PEN (polyethylene naphthalate) based film located between the first adhesive layer and the second adhesive layer. Similarly, the three-layer adhesive sealing layer structure may comprise a PI (polyimide) based film located between the first adhesive layer and the second adhesive layer. The PEN (polyethylene naphthalate) based film may have a thickness of 2-5 micrometers, in particular 3 micrometers. Similarly, the PI (polyimide) based film may have a thickness of 2-8 micrometers, in particular 5-7 micrometers. In total, the three-layer adhesive sealing layer structure may have a thickness of 3-15 micrometers, in particular 4-13 micrometers, for example 5 micrometers, or 7 micrometers, or 9 micrometers, or 13 micrometers. The first and second adhesive layers of the three-layer sealing adhesive tape may contain an adhesive that is not based on PET (polyethylene terephthalate).

The first and second adhesive films based on polyethylene terephthalate may have a thickness of 2-5 micrometers, in particular 3 micrometers.

The adhesive (non-polyethylene terephthalate-based) first and second support layers and the adhesive (polyethylene terephthalate-based) third support layer may have a thickness in the range of 2 micrometers to 10 micrometers, in particular in the range of 2 micrometers to 5 micrometers, for example 3 micrometers.

The first and second magnetic layers may have a thickness in the range of 15 micrometers to 25 micrometers, in particular in the range of 18 micrometers to 23 micrometers, for example 21 micrometers.

Further details of the various tapes, films and layers will be described below with respect to the method of the present invention, and they apply equally to the aerosol generating device of the present invention described herein.

As used herein, the term "individual fragments" refers to a magnetic layer configuration that comprises a plurality of fragments or a plurality of clusters of fragments that are not in indirect contact, in particular in electrical contact, with adjacent fragments or adjacent clusters of fragments to provide the ability to suppress eddy current effects.

The gaps between the individual fragments or clusters of fragments of said plurality may be at least partially filled with an electrically insulating material, such as a binder, for example, a polymer, such as silicone. In particular, the gaps between the individual fragments or clusters of fragments of said plurality may be at least partially filled with at least one of the following: the material of the first support layer, or, if present, the material of the second support layer, or, if present, the material of the adhesive film between adjacent magnetic layers, or a matrix material (binder) made of a soft magnetic alloy. Filling the gaps provides, as an advantage, helps to maintain said plurality of fragments or clusters of fragments in a state of constant separation from each other and, thus, maintaining a constant suppression of the effects caused by eddy currents, even if the flux concentrator foil as a whole is deformed.

In addition, the aerosol generating device may comprise a radial gap between said at least one inductor coil and the flow concentrator, and wherein the flow concentrator at least partially surrounds the inductor coil. Accordingly, said gap also at least partially surrounds the inductor coil. The gap may have a radial extension in the range from 40 micrometers to 400 micrometers, in particular from 100 micrometers to 240 micrometers, for example 220 micrometers. As an advantage, the gap may contribute to reducing losses in the inductor coil and increasing losses in the current collector to be heated, i.e. increasing the heating efficiency of the aerosol generating device.

The gap may be an air gap or a gap filled with a filler material, such as a polyimide, such as poly(4,4'-oxydiphenylene pyromellitimide), also known as Kapton®, or any other suitable dielectric materials. In particular, a first dielectric wrapper may be located around at least a portion of the inductor between the inductor and the magnetic flux concentrator. For example, the inductor may be wrapped with one or more layers of Kapton tape so as to fill the radial gap between said at least one inductor and the flux concentrator. One layer of Kapton tape may have a thickness in the range from 40 micrometers to 80 micrometers.

In addition, the aerosol generating device may comprise an electrically conductive shielding wrapper that is arranged around the flow concentrator. As an advantage, the electrically conductive shielding wrapper serves to shield the environment of the device from the magnetic field inside the device.

In addition, the aerosol generating device may comprise a second dielectric wrapper, which is located around the flow concentrator, in particular around the shielding wrapper, if present. Similar to the first dielectric wrapper, the second dielectric wrapper provides the possibility of helping to reduce losses in the inductance coil and increase losses in the current collector to be heated, i.e., increase the heating efficiency of the aerosol generating device.

In general, the flux concentrator may have any shape, but preferably a shape corresponding to the shape of the said at least one induction coil, around which the flux concentrator is at least partially located.

For example, the flux concentrator can have a substantially cylindrical shape, in particular a sleeve shape or a tubular shape. In other words, the flux concentrator can be a tubular flux concentrator, or a sleeve flux concentrator, or a cylindrical flux concentrator. Such shapes are particularly suitable in the case where said at least one inductor is a spiral inductor having a substantially cylindrical shape. In such configurations, the flux concentrator completely surrounds said at least one inductor along at least a portion of the axial extension of the coil along the length. The tubular shape or sleeve shape provides a particular advantage with respect to the cylindrical shape of the cavity, as well as with respect to the cylindrical and/or spiral configuration of the inductor. With respect to these shapes, the flux concentrator can have any suitable cross-section. For example, the flux concentrator can have a square, oval, rectangular, triangular, pentagonal, hexagonal or similar cross-sectional shape. Preferably, the flow concentrator has a circular cross-section. For example, the flow concentrator may have a circular cylindrical shape.

It is also possible that the flux concentrator passes around only a section of the circumference of said at least one induction coil.

In any of these configurations, the flux concentrator is preferably located coaxially with the center line of said at least one inductor. Even more preferably, the flux concentrator and said at least one inductor are located coaxially with the center line of said cavity.

In general, the induction heating structure may comprise one induction coil or a plurality of induction coils, in particular two induction coils. In the case of one induction coil, the flux concentrator may be located around at least a section of said one induction coil, preferably around the entire induction coil. In the case of several induction coils, the flux concentrator may be located around at least a section of one of the induction coils, preferably around at least a section of each of the induction coils, even more preferably completely around each induction coil.

The flow concentrator foil may be wound in particular in such a way that its ends overlap or adjoin each other to form a tubular flow concentrator or a flow concentrator sleeve. The ends that overlap or adjoin each other may be attached to each other. Likewise, the ends that overlap or adjoin each other may freely overlap each other, or they may freely adjoin each other.

In particular, the flow concentrator foil may be wound in the form of a single turn so as to form a tubular flow concentrator or a flow concentrator sleeve comprising a single turn of the flow concentrator foil. Alternatively, the flow concentrator foil may be wound in the form of a plurality of turns/windings so as to form a tubular flow concentrator or a flow concentrator sleeve comprising a plurality of turns of the flow concentrator foil, in particular spiral turns.

The flow concentrator foil may also be wound in a spiral in an axial direction relative to the winding axis so as to form a tubular flow concentrator or flow concentrator sleeve comprising one or more spiral turns of flow concentrator foil overlapping each other.

It is also possible to wind the flow concentrator foil in the form of separate concentric turns one on top of the other. In other words, the flow concentrator may contain a plurality of layers of the flow concentrator foil wound in the form of separate concentric single (turns) turns one on top of the other. Similarly, it is also possible to wind the flow concentrator foil in the form of a separate multi-turn spiral or a plurality of turns one on top of the other. In other words, the flow concentrator may consist of a plurality of layers of the flow concentrator foil wound in the form of a separate concentric multi-turn spiral or spiral (turns) turns one on top of the other.

In addition, it is also possible that the flux concentrator comprises a plurality of flux concentrator foil layers arranged side by side next to each other, wherein each flux concentrator foil layer is wound in the form of a single turn or in the form of a plurality of helical turns overlapping each other, or in the form of separate concentric turns one on top of the other.

The configuration comprising a plurality of layers of flow concentrator foil, in particular multiple spiral or multiple helical turns or multiple individual concentric turns one on top of the other, can advantageously be used to form a multilayer flow concentrator foil or a multilayer flow concentrator, in which each turn corresponds to one layer. For example, the flow concentrator can comprise two, or three, or four, or five, or six, or more than six multiple spiral or multiple helical turns or multiple individual concentric turns. Accordingly, such a multilayer flow concentrator foil or a multilayer flow concentrator can have a thickness that substantially corresponds to the thickness of one layer of foil multiplied by the number of turns or layers. For example, if the foil has a thickness in the range from 0.02 mm (millimeter) to 0.25 mm (millimeter), in particular from 0.05 mm (millimeter) to 0.2 mm (millimeter), preferably from 0.1 mm (millimeter) to 0.15 mm (millimeter), then the multilayer flow concentrator foil or the multilayer flow concentrator comprising six layers may have a thickness in the range from 0.12 mm (millimeter) to 1.5 mm (millimeter), in particular from 0.3 mm (millimeter) to 1.2 mm (millimeter), preferably from 0.6 mm (millimeter) to 0.9 mm (millimeter).

In the case where the flow concentrator foil is wound, in particular in the form of a single turn so that a tubular flow concentrator or a flow concentrator sleeve is formed, the flow concentrator foil can be attached to the inner surface of the device casing by means of a tight fit due to a partial release of the elastic restoring force of the wound flow concentrator foil. In other words, the elastic restoring force presses the flow concentrator foil in the radial direction outward to the inner surface of the device casing. In this configuration, the ends of the wound foil preferably overlap each other freely or are loosely adjacent to each other. As an advantage, this configuration ensures simple installation of the flow concentrator, in particular without any additional fixing means.

It is also possible that the flow concentrator is obtained by extruding the flow concentrator foil with direct formation of the final shape of the flow concentrator. In particular, the flow concentrator can comprise or be an extruded flow concentrator foil, for example an extruded foil of a tubular flow concentrator, or an extruded foil of a flow concentrator core, or an extruded foil of a cylindrical flow concentrator. The extruded foil of a tubular flow concentrator, or an extruded foil of a flow concentrator core, or an extruded foil of a cylindrical flow concentrator can have a wall thickness in the range from 0.05 mm (millimeters) to 0.25 mm (millimeters), preferably from 0.1 mm (millimeters) to 0.15 mm (millimeters). The wall thickness may also be in the range from 0.12 mm (millimeter) to 1.5 mm (millimeter), in particular from 0.3 mm (millimeter) to 1.2 mm (millimeter), preferably from 0.6 mm (millimeter) to 0.9 mm (millimeter).

The induction heating structure may comprise at least one current-receiving element, which is a part of the device. Similarly, it is also possible that said at least one current-receiving element is an integral part of an aerosol-generating article, which contains an aerosol-forming substrate to be heated. As a part of the device, said at least one current-receiving element is located or is designed to be located at least partially inside said cavity in such a way as to be in thermal proximity to the aerosol-forming substrate or in thermal contact with it, preferably physical contact, during use.

As used in this document, the term "current collector" refers to an element that is capable of converting electromagnetic energy into heat when exposed to a changing electromagnetic field. This may be the result of hysteresis losses and/or eddy currents generated in the current collector, depending on the electrical and magnetic properties of the current collector material. Hysteresis losses occur in ferromagnetic or ferrimagnetic current collectors due to the reversal of magnetization of magnetic domains within the current collector material under the influence of an alternating magnetic field. Eddy currents may be induced if the current collector is electrically conductive. In the case of a conductive ferromagnetic or ferrimagnetic current collector, heat may be generated due to both eddy currents and hysteresis losses.

Accordingly, the current collecting element may be made of any material that can be inductively heated to a temperature sufficient to generate an aerosol from an aerosol-forming substrate. Preferred current collecting elements comprise a metal or a carbon material. A preferred current collecting element may comprise a ferromagnetic material, such as ferritic cast iron or ferromagnetic steel, or stainless steel. A suitable current collecting element may be or comprise aluminum. Preferred current collecting elements may be made of 400 series stainless steel, such as 410 series stainless steel, or 420 series stainless steel, or 430 series stainless steel.

The current-collecting element may have a plurality of geometric configurations. The current-collecting element may comprise or be a current-collecting pin, a current-collecting rod, a current-collecting blade, a current-collecting strip, or a current-collecting plate. If the current-collecting element is part of an aerosol-generating device, the current-collecting pin, current-collecting rod, current-collecting blade, current-collecting strip, or current-collecting plate may project into the cavity of the device, preferably in the direction of the opening of said cavity, for inserting the aerosol-generating article into said cavity.

The current collecting element may comprise or be a thread-like current collecting element, a mesh current collecting element or a wick current collecting element. Similarly, the current collecting element may comprise or be a current collecting sleeve, a current collecting cup, a cylindrical current collecting element or a tubular current collecting element. Preferably, the internal cavity of the current collecting sleeve, current collecting cup, cylindrical current collecting element or tubular current collecting element is designed with the possibility of removably placing therein at least a portion of an aerosol-forming substrate or an aerosol-generating article comprising an aerosol-forming substrate to be heated.

The above-mentioned current collecting elements may have any cross-sectional shape, such as round, oval, square, rectangular, triangular or any other suitable shape.

The term "aerosol generating device" as used in this document generally refers to an electrical device that is capable of interacting with at least one aerosol-generating substrate, in particular with an aerosol-generating substrate provided inside an aerosol-generating article, so as to generate an aerosol by heating the substrate. Preferably, the aerosol generating device is an inhalation device for generating an aerosol that can be directly inhaled by the user through the mouth. In particular, the aerosol generating device is a hand-held aerosol generating device.

In addition to the induction coil, the induction heating structure may comprise an alternating current (AC) generator. The AC generator may be powered by a power source of the aerosol generating device. The AC generator is operatively connected to said at least one induction coil. In particular, said at least one induction coil may be an integral part of the AC generator. The AC generator is configured to generate a high-frequency oscillating current to be passed through the induction coil to generate an alternating magnetic field. The alternating current may be supplied to the induction coil continuously after activation of the system, or it may be supplied intermittently, for example, from puff to puff.

Preferably, the induction heating structure comprises a DC to AC converter connected to a DC power source including an LC circuit, which in turn contains a series-connected capacitor and an inductor.

The induction heating structure is preferably designed to generate a high-frequency alternating magnetic field. In the context of this document, the high-frequency alternating magnetic field may be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), in particular from 5 MHz (megahertz) to 15 MHz (megahertz), preferably from 5 MHz (megahertz) to 10 MHz (megahertz).

The aerosol generating device may further comprise a controller configured to control the operation of the device. In particular, the controller may be configured to control the operation of the induction heating structure, preferably in a feedback configuration, to control the heating of the aerosol-forming substrate to a predetermined operating temperature. The operating temperature used to heat the aerosol-forming substrate may be at least 180 degrees Celsius, in particular at least 300 degrees Celsius, preferably at least 350 degrees Celsius, more preferably at least 370 degrees Celsius, most preferably at least 400 degrees Celsius. These temperatures are typical operating temperatures for heating, but not burning, the aerosol-forming substrate. Preferably, the operating temperature is in the range from 180 degrees Celsius to 370 degrees Celsius, in particular from 180 degrees Celsius to 240 degrees Celsius or from 280 degrees Celsius to 370 degrees Celsius. In general, the operating temperature may depend on at least one of the type of aerosol-forming substrate to be heated, the configuration of the current collector and the location of the current collector relative to the aerosol-forming substrate when using the system. For example, if the current collector is designed and located in such a way that it surrounds the aerosol-forming substrate when using the system, then the operating temperature may be in the range from 180 degrees Celsius to 240 degrees Celsius. Similarly, if the current collector is designed in such a way that it is located inside the aerosol-forming substrate when using the system, then the operating temperature may be in the range from 280 degrees Celsius to 370 degrees Celsius. The operating temperature described above preferably refers to the temperature of the current collector in use.

The controller may comprise a microprocessor, such as a programmable microprocessor, a microcontroller, or

an application-specific integrated circuit (ASIC), or other electronic circuit capable of providing control. The controller may contain additional electronic components, such as at least one DC-to-AC converter and/or power amplifiers, such as a class C, class D or class E power amplifier. In particular, the induction heating structure may be part of the controller.

The aerosol generating device may comprise a power source, in particular a DC power source configured to supply a DC supply voltage and a DC supply current to the induction heating structure. Preferably, the power source is a battery, such as a lithium iron phosphate battery. Alternatively, the power source may be a charge storage device of another type, such as a capacitor. The power source may require recharging, i.e. the power source may be rechargeable. The power source may have a capacity that provides the ability to store sufficient energy for one or more use sessions. For example, the power source may have a capacity sufficient to provide the ability to continuously generate an aerosol for a period of approximately six minutes, or for a period that is a multiple of six minutes. In another example, the power source may have a capacity sufficient to provide the ability to perform a given number of puffs or individual activations of the induction heating structure.

The aerosol generating device may comprise a main body which preferably includes at least one of an induction heating structure, in particular at least one induction coil, a flow concentrator, a controller, a power supply unit and at least a portion of said cavity.

In addition to the main body, the aerosol-generating device may further comprise a mouthpiece, in particular if the aerosol-generating article to be used with the device does not comprise a mouthpiece. The mouthpiece may be mounted on the main body of the device. The mouthpiece may be designed to close the receiving cavity when the mouthpiece is mounted on the main part. To attach the mouthpiece to the main part, the near end portion of the main body may comprise a magnetic or mechanical fastening, such as a bayonet fastening or a snap fastening, which interacts with a corresponding mating part on the far end portion of the mouthpiece. If the device does not comprise a mouthpiece, the aerosol-generating article to be used with the aerosol-generating device may comprise a mouthpiece, such as a filter plug.

The aerosol generating device may comprise at least one air outlet, such as an air outlet in a mouthpiece (if present).

Preferably, the aerosol generating device comprises an air path extending from said at least one air inlet through the receiving cavity and, possibly, further to an air outlet in the mouthpiece, if present. Preferably, the aerosol generating device comprises at least one air inlet in fluid communication with the receiving cavity. Accordingly, the aerosol generating system may comprise an air path extending from said at least one air inlet into the receiving cavity and, possibly, further through the aerosol-forming substrate inside the article and the mouthpiece into the user's mouth.

The said at least one inductance coil and flux concentrator may be part of an induction module, which is located inside the casing of the device and forms at least a section of the cavity of the device or is located around a circumference, in particular is located with the possibility of extraction around at least a section of the cavity of the device.

In this connection, the present invention also provides an induction module, configured to be positioned inside the aerosol-generating device in such a way as to form at least a section of the cavity of the device or to be positioned circumferentially around it, wherein said cavity is configured to allow for the removable placement therein of an aerosol-forming substrate subject to induction heating. The induction module comprises at least one induction coil for generating an alternating magnetic field inside said cavity during use, wherein said at least one induction coil is positioned around at least a section of the receiving cavity, when the induction module is positioned in the device. The induction module further comprises a flow concentrator, positioned circumferentially around at least a section of said at least one induction coil and configured to distort the alternating magnetic field of the induction coil during use in the direction of said cavity, when the induction module is positioned in the device. The flow concentrator comprises a flow concentrator foil according to the present invention, described in this document, or is made of it. In other words, the flux concentrator foil is a multilayer flux concentrator foil having at least one magnetic layer that forms a layered structure with at least a first support layer, wherein the magnetic layer contains a plurality of individual fragments of a soft magnetic alloy.

Additional features and advantages of the induction module, in particular the induction coil and flow concentrator, have been described in relation to the aerosol generating device and apply to the same extent.

According to another aspect of the present invention, an aerosol generating system is also proposed, which comprises an aerosol generating device according to the present invention, described in this document. The system further comprises an aerosol generating article for use with said device, wherein said article comprises an aerosol-forming substrate subject to induction heating by means of the device. The aerosol generating article is located or is configured to be located at least partially in the cavity of the device.

As used herein, the term "aerosol generating system" refers to a combination of an aerosol generating article, further described herein, with an aerosol generating device according to the present invention, described herein. In the system, the article and the device cooperate to generate an inhalable aerosol.

As used herein, the term "aerosol-generating article" refers to an article comprising at least one aerosol-forming substrate that, when heated, releases volatile compounds capable of forming an aerosol. Preferably, the aerosol-generating article is a heated aerosol-generating article. In other words, the aerosol-generating article comprises at least one aerosol-forming substrate that is designed to be heated, rather than burned, to release volatile compounds that can form an aerosol. The aerosol-generating article may be a consumable part, in particular a consumable part that is disposed of after a single use. For example, the article may be a cartridge comprising a liquid aerosol-forming substrate that is subject to heating. Alternatively, the article may be a rod-shaped article, in particular a tobacco article similar to conventional cigarettes.

As used herein, the term "aerosol-forming substrate" means a substrate that is formed from or contains an aerosol-forming material that is capable of releasing volatile compounds when heated to generate an aerosol. The aerosol-forming substrate is designed to be heated, rather than combusted, to release volatile aerosol-forming compounds. The aerosol-forming substrate may be a solid aerosol-forming substrate, a liquid aerosol-forming substrate, a gel-forming aerosol-forming substrate, or any combination thereof. The aerosol-forming substrate may comprise a tobacco-containing material that contains volatile tobacco flavor compounds that are released from the substrate when heated. Alternatively or additionally, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol-forming agent. Examples of suitable aerosol-forming agents include glycerin and propylene glycol. The aerosol-forming substrate may also contain other additives and ingredients, such as nicotine or flavoring agents. The aerosol-forming substrate may also be a paste-like material, a pouch of porous material containing the aerosol-forming substrate, or, for example, loose tobacco, which is mixed with a gelling agent or adhesive, may include a conventional aerosol-forming agent, such as glycerin, and is pressed or molded into a plug.

As mentioned above, said at least one current-receiving element used for inductively heating the aerosol-forming substrate may be an integral part of the aerosol-generating article, and not a part of the aerosol-generating device. Accordingly, the aerosol-generating article may comprise at least one current-receiving element located in thermal proximity to the aerosol-forming substrate or in thermal contact with it in such a way that, in use, it is possible to inductively heat the current-receiving element using the inductive heating structure, when the article is placed in the cavity of the device.

Additional features and advantages of the aerosol generating system according to the present invention have been described in relation to the aerosol generating device and apply to the same extent.

According to another aspect of the present invention, a method for producing a multilayer foil of a flow concentrator of an aerosol generating device according to the present invention is proposed and described herein. The method comprises:

- providing a multilayer flux concentrator foil having at least one magnetic layer made of a soft magnetic alloy forming a layered structure with at least a first support layer;

- cracking of said at least one magnetic layer into a plurality of fragments by applying an external force to the foil of the flux concentrator perpendicular to the plane of the foil and

- tensioning the flow concentrator foil by pulling the flow concentrator foil with a tension force parallel to the plane of the foil.

In particular, tensioning the flow concentrator foil by pulling may include pulling the flow concentrator foil with a tension force parallel to the plane of the foil, through at least one edge, in particular through only one edge.

According to the present invention, it has been found that the magnetic layer of the flux concentrator foil can be reliably fragmented to form a plurality of individual fragments by first applying an external force to the flux concentrator foil perpendicular to the plane of the foil and then tensioning the flux concentrator foil by pulling the flux concentrator foil with a tension force parallel to the plane of the foil, in particular through at least one edge. While the first step results in cracking the magnetic layer into a plurality of fragments, the second step results in cracking these fragments into even smaller fragments and, most importantly, in separating them so that they are separated from each other. As an advantage, the second step results in an enhanced reduction in the alternating current resistance of the magnetic layer and, thus, in an enhanced reduction in eddy current losses in the magnetic layer of the flux concentrator foil due to the separation of the fragments.

Cracking of said at least one magnetic layer into a plurality of individual fragments may include passing the flow concentrator foil through at least one pair of rollers, in particular counter-rotating rollers, which apply a pressing force to the flow concentrator foil passing through them. In other words, pressure is applied to press the rollers against each other in such a way that the foil passing through them is compressed between these two rollers. At least one of the rollers may comprise a plurality of projections on its outer surface, each of which locally applies a force to the flow concentrator foil perpendicular to the plane of the foil. The corresponding other roller may act as a support roller. It is possible to enhance cracking if each of the rollers comprises a plurality of projections on its outer surface. Said pluralities of projections on both rollers may be made in the form of complementary projections. For example, when used, the projections of one roller may enter between the projections of the corresponding other roller. It is also possible that only one of the rollers comprises a plurality of projections, while the corresponding other roller comprises a smooth outer surface. The roller(s) having a plurality of projections may be made of metal, for example stainless steel. The roller having a smooth outer surface may be made of rubber. The rubber material must have a suitable hardness to ensure cracking. The flow concentrator foil may be passed either through one pair of rollers or through a sequence of pairs of rollers. In order to crack said at least one magnetic layer to form a plurality of individual fragments, a burst pressure in the range of 4 bar to 8 bar, for example 6 bar, may be applied to the flow concentrator foil perpendicular to the plane of the foil, in particular by means of said rollers. Before and after passing through said at least one pair of rollers, the flow concentrator foil may be unwound and re-wound, respectively. Unwinding and rewinding of the flow concentrator foil before and after it passes through said at least one pair of rollers can occur with a tension force of 40-60 N (Newtons), for example, 50 N (Newtons), and a winding speed of 5-10 m/min., for example, 7 m/min.

The step of cracking said at least one magnetic layer into a plurality of fragments by applying an external force to the flow concentrator foil perpendicular to the plane of the foil can be repeated several times, for example, once or twice. Accordingly, the flow concentrator foil can be passed through said at least one pair of rollers two or three times. It is also possible to pass the flow concentrator foil through said at least one pair of rollers only once.

Pulling the flow concentrator foil through said at least one edge may include pulling the flow concentrator foil through said at least one edge forward and backward, in particular repeatedly forward and backward, for example 4-6 times forward and backward. Pulling forward and backward provides the possibility of improving the separation of the fragments.

Preferably, said at least one edge is a sharp edge. In other words, said at least one edge may have a radius of curvature of no more than 1 millimeter, in particular a maximum of 0.3 millimeters, preferably a maximum of 0.2 millimeters, more preferably a maximum of 0.15 millimeters.

The pulling through the edge can be carried out at an angle in the range from 60 degrees to 120 degrees, in particular from 80 degrees to 100 degrees, preferably at an angle of 90 degrees. In other words, the flow concentrator foil is bent at this angle when pulled through the said edge. The said angle is measured between the foil section located earlier along the flow relative to the said edge and the foil section located further along the flow relative to the said edge.

During the pulling of the flow concentrator foil, the tension force may be in the range of 20 N (Newtons) to 60 N (Newtons), in particular 25 N (Newtons) to 40 N (Newtons), for example 30 N (Newtons). These values have been proven to be particularly useful for separating fragments. The pulling of the flow concentrator foil through said edge may be carried out at a speed of 5 to 15 m/min, for example 10 m/min.

The step of providing a multilayer flux concentrator foil having at least one magnetic layer of a soft magnetic alloy forming a layered structure with at least a first support layer may include at least one of the following:

providing a tape containing or made from a soft magnetic alloy;

annealing of a tape containing or made from a soft magnetic alloy;

providing a first adhesive tape comprising a first support layer comprising an adhesive;

forming a layered structure from a first support layer and (annealed) tape containing or made from a soft magnetic alloy, so as to obtain a first layered structure.

The step of providing a multilayer flow concentrator foil may further include at least one of the following:

repeating the above steps of providing a tape, annealing the tape, providing an (intermediate) adhesive tape containing an (intermediate) support layer which is adhesive, and forming a layered structure from the (intermediate) support layer and the (annealed) tape in such a way as to obtain an intermediate layered structure which contains an (intermediate) adhesive tape containing an intermediate support layer;

providing a second adhesive tape comprising a second support layer which is adhesive;

forming a layered structure from the first layered structure, the intermediate layered structure and the second adhesive tape so as to obtain a (non-sealed) multilayer flow concentrator foil, in which the intermediate layered structure is located between the first layered structure and the second adhesive tape.

The tape containing the soft magnetic alloy or made from it may have a thickness in the range from 15 micrometers to 25 micrometers, in particular in the range from 18 micrometers to 23 micrometers, for example 21 micrometers. Preferably, the tape containing the soft magnetic alloy or made from it is provided on a roll or a reel. Before annealing the tape containing the soft magnetic alloy or made from it, the tape may be rewound one or more times, for example from one reel or roll holder to another, to adjust the tape tension. For example, the tape containing the soft magnetic alloy or made from it may be rewound in the first stage with a tension force of 20 N (Newtons) ±10% and in the second stage with a tension force of 10 N (Newtons) ±10%. The rewinding speed can be 30m/min ±10% during the first stage and 20m/min ±10% during the first stage.

The step of annealing the tape containing or made from a soft magnetic alloy may include heating the tape containing or made from a soft magnetic alloy at a temperature in the range of 450 degrees Celsius to 520 degrees Celsius, such as 495 degrees Celsius, for a period of time in the range of 300 min. to 500 min., such as 450 min.

The first support layer of the first adhesive tape and the intermediate support layer of the intermediate adhesive tape may comprise an adhesive, in particular an adhesive that is not based on PET (polyethylene terephthalate). The first support layer and the intermediate support layer may have a thickness in the range of 2 micrometers to 10 micrometers, in particular in the range of 2 micrometers to 5 micrometers, for example 3 micrometers. In addition to the first/intermediate support layer, the first/intermediate adhesive tape may comprise first and second release films on both sides of the adhesive first/intermediate support layer before the first/intermediate adhesive tape is mounted on the (annealed) tape. In other words, the first and/or second release films must be removed before the adhesive first/intermediate support layer is attached to any other object. Accordingly, the step of laminating the first/intermediate support layer onto the tape comprising or made of a soft magnetic alloy may comprise removing the first release film from the first/intermediate adhesive tape, installing the (annealed) tape on the adhesive first/intermediate support layer from the side opposite the second release film, and, preferably, re-installing the first release film on the upper side of the (annealed) tape comprising or made of a soft magnetic alloy. The above steps may be implemented by unwinding the first/intermediate adhesive tape and the (annealed) tape; removing the first release film; bringing into contact with each other and fastening together the unwound (annealed) tape and the unwound adhesive first/intermediate tape (without the first release film); re-installing the first release film; applying pressure to the obtained first/intermediate laminated structure; and, if necessary, rewinding the first/intermediate laminated structure. Unwinding of the first/intermediate adhesive tape and the (annealed) tape may be carried out with a tension force of 40-60 N (Newtons), for example 50 N (Newtons), and an unwinding speed of 5-10 m/min., for example 7 m/min. Similarly, rewinding of the first/intermediate laminated structure may be carried out with a tension force of 40-60 N (Newtons), for example 50 N (Newtons), and a winding speed of 5-10 m/min., for example 7 m/min.

Similarly, the second support layer of the second adhesive tape may comprise a PET (polyethylene terephthalate) based adhesive. The second support layer may have a thickness in the range of 2 micrometers to 10 micrometers, in particular in the range of 2 micrometers to 5 micrometers, for example 3 micrometers. In addition to the second support layer, the second adhesive tape may comprise first and second release films on both sides of the adhesive second support layer before attaching the second adhesive tape to the intermediate layer structure. In other words, the first and/or second release films must be removed before attaching the adhesive second support layer to any other object. Accordingly, the step of laminating the second support layer to the intermediate layer structure may include removing the second release film from the second adhesive tape and installing the adhesive second support layer on the intermediate layer structure from the side opposite to the second release film. The above-mentioned steps can be realized by unwinding the second adhesive tape, the first laminated structure and the intermediate laminated structure; removing the second release film from the second adhesive tape; removing the first and second release films from the intermediate laminated structure and removing the first release film from the first laminated structure; bringing into contact with each other and fastening together the unwound first laminated structure (without the first release film), the intermediate laminated structure (without the first and second release films) and the second adhesive tape (without the second release film); applying pressure to the obtained (unsealed) multilayer flow concentrator foil; and then rewinding the multilayer flow concentrator foil. The unwinding of the second adhesive tape, the first laminated structure and the intermediate laminated structure can be performed with a tension force of 40-60 N (Newtons), for example 50 N (Newtons), and an unwinding speed of 5-10 m/min., for example 7 m/min. Similarly, rewinding of the multilayer flow concentrator foil can be done with a tension force of 40-60 N (Newtons), for example, 50 N (Newtons), and a winding speed of 5-10 m/min., for example, 7 m/min.

The above process enables the production of (unsealed) multilayer flow concentrator foils containing the following layers (from bottom to top):

adhesive (non-PET) first support layer (formed from the first laminated structure),

a first magnetic layer of the (annealed) tape containing or made from a soft magnetic alloy (formed from the first layered structure),

adhesive (non-PET) intermediate support layer (formed from an intermediate laminate structure),

a second magnetic layer of the (annealed) tape comprising or made from a soft magnetic alloy (formed from a second layered structure), and

the second adhesive (based on polyethylene terephthalate) support layer (formed from the second adhesive tape).

In addition, the multilayer flow concentrator foil may comprise a first release film above the adhesive second support layer (formed from the second adhesive tape) and a second release film under the adhesive first support layer (formed from the first adhesive tape of the first layered structure). The first release film (formed from the second adhesive tape) and the second release film (formed from the first adhesive tape of the first layered structure) are removed before placing the multilayer flow concentrator foil around at least a portion of the induction coil of the aerosol generating device in which said multilayer flow concentrator foil is to be used. Similarly, the first release film (formed from the second adhesive tape) and the second release film (formed from the first adhesive tape of the first laminated structure) may be removed prior to a possible additional step of the method described herein, in particular prior to sealing one or more cutting edges of the (unsealed) flow concentrator, more particularly prior to securing the adhesive sealing tape on one or each side of the (unsealed) foil of the flow concentrator.

In addition, the method may include pulling the flow concentrator foil with a tension force parallel to the plane of the foil, through at least one roller, in particular a series of rollers, for bending the flow concentrator foil. This step provides the advantage of cracking said fragments into even smaller fragments, which leads to an increased decrease in the alternating current resistance of the magnetic layer. Pulling the flow concentrator foil through said at least one roller may be performed before pulling the flow concentrator foil through said at least one edge.

The at least one roller mentioned may have a radius of no more than 50 millimetres, in particular no more than 30 millimetres, preferably no more than 10 millimetres.

The tension force for pulling the flow concentrator foil through said at least one roller may be in the range from 20 N (Newtons) to 60 N (Newtons), in particular from 25 N (Newtons) to 40 N (Newtons), for example, 30 N (Newtons).

The method may further include cutting the flow concentrator foil to a specified size. The cutting may be performed before cracking the magnetic layer into a plurality of fragments, or before pulling the flow concentrator foil through said at least one edge, or after pulling the flow concentrator foil through said at least one edge.

The method may further comprise sealing one or more cut edges of the flow concentrator foil cut to size. This advantageously prevents fragments from falling out of the foil in the transverse direction.

Sealing one or more cutting edges of the (unsealed) multilayer flow concentrator foil cut to size may include fixing a sealing adhesive tape on one or on each side of the flow concentrator foil cut to size, wherein the width extension of the adhesive sealing tape in the direction transverse to the opposite cutting edges of the flow concentrator foil is greater than the width extension of the flow concentrator foil cut to size in the same direction, i.e. in the direction transverse to the opposite cutting edges of the flow concentrator foil. As a result, the sealing adhesive tape on each side of the (unsealed) flow concentrator foil comprises lateral protruding wings that can come into adhesive contact with each other in such a way as to seal the cutting edges of the (unsealed) flow concentrator.

The adhesive sealing tape may comprise a three-layer adhesive sealing laminate structure comprising a PEN (polyethylene terephthalate)-based foil located between a first adhesive layer and a second adhesive layer. Similarly, the adhesive sealing tape may comprise a three-layer adhesive sealing laminate structure comprising a PI (polyimide)-based foil located between a first adhesive layer and a second adhesive layer. The PEN (polyethylene naphthalate)-based film may have a thickness of 2-5 micrometers, in particular 3 micrometers. Similarly, the PI (polyimide)-based film may have a thickness of 2-8 micrometers, in particular 5-7 micrometers. In total, the three-layer adhesive sealing layer structure may have a thickness of 3-15 micrometers, in particular 4-13 micrometers, for example 5 micrometers, or 7 micrometers, or 9 micrometers, or 13 micrometers. The first and second adhesive layers of the three-layer sealing adhesive tape may contain an adhesive that is not based on PET (polyethylene terephthalate). In addition to the three-layer adhesive sealing laminated structure, the adhesive sealing tape may comprise a first release film on the first adhesive layer (opposite to the polyethylene terephthalate or polyimide based film) and a second release film on the second adhesive layer (opposite to the polyethylene terephthalate or polyimide based film), wherein one of the first and second release films must be removed before attaching the sealing adhesive tape to the flow concentrator foil cut to size, and the corresponding other of the first and second release films must be removed before placing the sealed multilayer flow concentrator foil around at least a portion of the induction coil of the aerosol generating device in which the multilayer flow concentrator foil is to be used.

Similarly, the adhesive sealing tape may comprise a PET (polyethylene terephthalate) based adhesive film. The PET (polyethylene terephthalate) based adhesive film may have a thickness of 2-5 micrometers, in particular 3 micrometers. In addition to the polyethylene terephthalate based adhesive film, the adhesive sealing tape may comprise a first release film and a second release film, between which the PET (polyethylene terephthalate) based adhesive film is located, wherein one of the first and second release films must be removed before attaching the sealing adhesive tape to the flow concentrator foil cut to size, and the corresponding other of the first and second release films must be removed before placing the sealed multilayer flow concentrator foil around at least a portion of the induction coil of the aerosol generating device in which the multilayer flow concentrator foil is to be used.

Accordingly, the step of attaching the sealing adhesive tape to the multilayer flow concentrator film cut to size may include removing one of the first and second release films from each of the two sealing adhesive tapes and attaching the sealing adhesive tapes to the multilayer flow concentrator foil, one on each side of the multilayer flow concentrator foil. The above-mentioned steps may be realized by unwinding the two sealing adhesive tapes; removing one of the first and second release films from the sealing adhesive tape; if applicable, removing the first release film (formed from the second adhesive tape) and the second release film (formed from the first adhesive tape of the first layered structure) from the multilayer flow concentrator foil; bringing into contact with each other and fastening together the multilayer flow concentrator foil (without the first and second release films) and the unwound sealing adhesive tapes (without one of the first and second release films), one sealing adhesive tape on each side of the multilayer flow concentrator foil, so that the transversely protruding wings of the sealing adhesive tapes come into adhesive contact with each other; applying pressure to the resulting sealed multilayer flow concentrator foil; and, if necessary, rewinding the sealed multilayer flow concentrator foil.

The above mentioned method provides the possibility of obtaining a sealed multilayer flow concentrator foil containing the following layers (from bottom to top):

a first three-layer adhesive sealing layered structure comprising a film (based on polyethylene naphthalate or polyimide) located between a first adhesive layer and a second adhesive layer,

an adhesive (non-PET based) first support layer (formed from the first laminated structure),

a first magnetic layer of the (annealed) tape containing or made from a soft magnetic alloy (formed from the first layered structure),

adhesive (non-PET based) intermediate support layer (formed from the second laminated structure),

a second magnetic layer of the (annealed) tape containing or made from a soft magnetic alloy (formed from a second layered structure),

a second adhesive (polyethylene terephthalate based) support layer (formed from the third adhesive tape), and

a second three-layer adhesive sealing layered structure comprising a film (based on polyethylene naphthalate or polyimide) located between the first adhesive layer and the second adhesive layer.

Similarly, the above process enables the production of a sealed multilayer flow concentrator foil containing the following layers (from bottom to top):

the first adhesive film based on polyethylene terephthalate,

an adhesive (non-PET based) first support layer (formed from the first laminated structure),

a first magnetic layer of the (annealed) tape containing or made from a soft magnetic alloy (formed from the first layered structure),

adhesive (non-PET based) intermediate support layer (formed from the second laminated structure),

a second magnetic layer of the (annealed) tape containing or made from a soft magnetic alloy (formed from a second layered structure),

a second adhesive (polyethylene terephthalate based) support layer (formed from the third adhesive tape), and

the second adhesive film based on polyethylene terephthalate.

In addition, the sealed multilayer flow concentrator foil may comprise a first release film above the second three-layer adhesive sealing layer structure or the second adhesive film based on polyethylene terephthalate, respectively, and a second release film below the first three-layer adhesive sealing layer structure or the first adhesive film based on polyethylene terephthalate, respectively. The first release film and the second release film may be obtained from sealing adhesive tapes, and they must be removed before placing the sealed multilayer flow concentrator foil around at least a portion of the inductance coil of the aerosol generating device in which the multilayer flow concentrator foil is to be used.

Preferably, the flow concentrator foil is provided in the form of a flow concentrator tape, in particular in the form of a continuous flow concentrator foil. As an advantage, this enables the method to be implemented as a roll-to-roll process.

Additional features and advantages of the method according to the present invention have been described in relation to the aerosol generating device and apply to the same extent.

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

Example Ex1: An aerosol generating device for generating an aerosol by inductively heating an aerosol-forming substrate, comprising:

a device casing containing a cavity designed to allow the aerosol-forming substrate to be heated to be removably placed therein;

an induction heating structure comprising at least one induction coil for generating an alternating magnetic field within said cavity, wherein the induction coil is located around at least a portion of the receiving cavity; and

a flux concentrator located around at least a section of the induction coil and configured to distort the alternating magnetic field of said at least one induction heating structure in the direction of said cavity during use of the device, wherein the flux concentrator comprises a multilayer flux concentrator foil having at least one magnetic layer forming a layered structure with at least a first support layer, and wherein said magnetic layer comprises a plurality of individual fragments of a soft magnetic alloy.

Example Ex2: An aerosol generating device according to example 1, wherein the soft magnetic alloy is a nanocrystalline soft magnetic alloy, in particular a nanocrystalline Fe-based soft magnetic alloy.

Example Ex3: An aerosol-generating article according to any of the previous examples, wherein the soft magnetic alloy comprises a composition of Fe _100-abcxyz Cu _a M _b T _c Si _x Z _z and up to 0.5 atomic % of contaminants, where M is one or more from the group consisting of Nb, Mo and Ta; T is one or more from the group consisting of V, Cr, Co and Ni; Z is one or more from the group consisting of C, P and Ge; 0.5 atomic % < a < 1.5 atomic %; 2 atomic % b<4 atomic %; 0 atomic % c<5 atomic %; 12 atomic %<x<18 atomic %; 5 atomic %<y<12 atomic %; and 0 atomic % z<2 atomic%.

Example Ex4: An aerosol generating article according to any of the previous examples, wherein the soft magnetic alloy comprises a composition of Fe _73.8 Nb ₃ Cu ₁ Si _15.6 B _6.6 .

Example Ex5: An aerosol generating device according to any of the previous examples, wherein each individual fragment has a fragment size of at most 1 millimetre, in particular at most 750 micrometres or at most 500 micrometres.

Example Ex6: An aerosol generating device according to any of the previous examples, wherein said plurality of individual fragments may have an average fragment size of at most 1 millimetre, in particular at most 750 micrometres or at most 500 micrometres.

Example Ex7: An aerosol generating device according to any of the previous examples, wherein the soft magnetic alloy has a maximum relative magnetic permeability of at least 100, in particular at least 1000, preferably at least 10000, even more preferably at least 50000.

Example Ex8: An aerosol generating device according to any of the preceding examples, wherein said plurality of individual fragments are arranged in a pattern comprising a plurality of cracking centers, wherein the plurality of cracks extend radially outward from each cracking center in a web-like pattern.

Example Ex9: An aerosol generating device according to any of the previous examples, wherein the multilayer flow concentrator foil comprises a plurality of adjacent magnetic layers.

Example Ex10: An aerosol generating device according to example 9, wherein an adhesive film, in particular an electrically insulating adhesive film, is located between every two adjacent magnetic layers.

Example Ex11: An aerosol generating device according to any of the previous examples, wherein the multilayer flow concentrator foil comprises a second support layer on that side of said at least one magnetic layer or, if applicable, a plurality of adjacent magnetic layers, which is opposite the first support layer.

Example Ex12: An aerosol generating device according to any of the previous examples, wherein at least one of the first support layer and, if present, the second support layer is one of an adhesive layer, an electrically insulating layer or an electrically insulating adhesive layer.

Example Ex13: An aerosol generating device according to any of the previous examples, wherein the gaps between the individual fragments of said plurality are at least partially filled with an electrically insulating material, in particular at least one of the material of the first support layer, or, if present, the material of the second support layer, or, if present, the material of the adhesive film between adjacent magnetic layers, or a matrix material made of a soft magnetic alloy.

Example Ex14: An aerosol generating device according to any of the previous examples, wherein the flow concentrator foil has a thickness in the range from 0.02 millimetres to 0.25 millimetres, in particular from 0.05 millimetres to 0.2 millimetres, preferably from 0.1 millimetres to 0.15 millimetres.

Example Ex15: An aerosol generating device according to any of the previous examples, wherein a first dielectric wrapper is located between the inductor and the flow concentrator around at least a portion of the inductor.

Example Ex16: An aerosol generating device according to any of the previous examples, wherein an electrically conductive shielding wrapper is located around the flow concentrator.

Example Ex17: An aerosol generating device according to any of the previous examples, wherein a second dielectric wrapper is arranged around the flow concentrator, in particular around said shielding wrapper, if present.

Example Ex18: An aerosol generating device according to any of the preceding claims, further comprising at least one current collecting element located at least partially within said cavity.

Example Ex19: An aerosol generating device according to example 18, wherein the current collector is a tubular current collector or a current collector sleeve.

Example Ex20: An aerosol generating system comprising an aerosol generating device according to any of the previous examples and an aerosol generating article placed or configured to be placed in a cavity of the device, wherein said aerosol generating article comprises an aerosol forming substrate that is subject to heating.

Example Ex21: An aerosol generating system according to example 20, wherein the aerosol generating article comprises at least one current collector located in thermal proximity to or in thermal contact with the aerosol forming substrate such that in use the current collector can be inductively heated by the inductive heating structure when the article is placed in the cavity of the device.

Example Ex22: A method for producing a multilayer foil of a flow concentrator of an aerosol generating device according to any of the previous examples, comprising:

- providing a multilayer flux concentrator foil having at least one magnetic layer made of a soft magnetic alloy forming a layered structure with at least a first support layer;

- cracking of the magnetic layer into a multitude of separate fragments by applying an external force to the flux concentrator foil perpendicular to the plane of the foil and

- tensioning the flow concentrator foil by pulling the flow concentrator foil with a tension force parallel to the plane of the foil.

Example Ex23: The method according to example 22, wherein cracking the magnetic layer into a plurality of individual fragments comprises passing the flux concentrator foil through at least one pair of rollers which apply a pressing force to the flux concentrator foil passing therethrough, wherein at least one of the rollers comprises a plurality of projections on its outer surface.

Example Ex24: The method according to example 23, wherein the respective other roller comprises a smooth outer surface or each of the rollers comprises a plurality of projections on its outer surface.

Example Ex25: The method according to any of examples 22-25, wherein the tensioning of the flow concentrator foil by pulling comprises pulling the flow concentrator foil with a tension force parallel to the plane of the foil, through at least one edge, in particular through only one edge.

Example Ex26: The method according to example 25, wherein pulling the flow concentrator foil through at least one edge comprises pulling the flow concentrator foil through at least one sharp edge forwards and backwards, in particular repeatedly forwards and backwards, preferably 4-6 times forwards and backwards.

Example Ex27: The method according to any of examples 25 or 26, wherein said at least one edge has a radius of curvature of no more than 1 millimetre, in particular a maximum of 0.3 millimetres, preferably a maximum of 0.2 millimetres, more preferably a maximum of 0.15 millimetres.

Example Ex28: The method according to any of examples 22-27, wherein the tension force is in the range from 20 N to 60 N, in particular from 25 N to 40 N, for example 30 N.

Example Ex29: The method according to any of examples 22-28, further comprising drawing the flow concentrator foil under a tensile force parallel to the plane of the foil through at least one roller, in particular a series of rollers, for bending the flow concentrator foil.

Example Ex30: The method according to example 29, wherein said at least one roller has a radius of at most 50 millimetres, in particular at most 30 millimetres, preferably at most 10 millimetres.

Example Ex31: The method according to any of examples 29 or 30, wherein the tension force is in the range from 20 N to 60 N, in particular from 25 N to 40 N, for example 30 N.

Example Ex32: The method according to any of examples 22-31, wherein the flow concentrator foil is provided in the form of a flow concentrator tape.

Example Ex33: The method according to any one of examples 22-32, wherein the flow concentrator foil is provided in the form of a continuous flow concentrator foil.

Example Ex34: The method according to any of examples 22-33, further comprising cutting the flow concentrator foil to a given size.

Example Ex35: The method according to example 34, further comprising sealing one or more cut edges of the flow concentrator foil cut to size.

Example Ex36: The method according to examples 22-35, implemented as a roll-to-roll process.

Below are additional examples described with reference to drawings in which:

Fig. 1 is a schematic longitudinal sectional view of an aerosol generating system according to a first embodiment of the present invention;

Fig. 2 - detailed view of the induction module according to Fig. 1;

Fig. 3, 4a-4b - details of the multilayer foil of the flow concentrator used in the device according to Fig. 1;

Fig. 5-8 - three different designs of flow concentrator foil according to the present invention;

Fig. 9 is a schematic view of an exemplary embodiment of a multilayer flux concentrator foil comprising a plurality of magnetic layers;

Fig. 10 is a detailed view of an induction module according to a second embodiment of the present invention;

Fig. 11 is a schematic longitudinal sectional view of an aerosol generating system according to another embodiment of the present invention;

Fig. 12-15 - examples of various steps of the method according to the present invention;

Fig. 16 - details of another example of a multilayer flux concentrator foil that can be used in the device according to Fig. 1 and comprises a plurality of magnetic layers; and

Fig. 17 - multilayer foil of the flow concentrator according to Fig. 16, sealed with a sealing adhesive tape.

Fig. 1 shows a schematic sectional view of a first exemplary embodiment of an aerosol generating system 1 according to the present invention. The system 1 is configured to generate an aerosol by inductively heating an aerosol-forming substrate 91. The system 1 comprises two main components: an aerosol-generating article 90 comprising an aerosol-forming substrate 91 to be heated, and an aerosol-generating device 10 for use with the article 90. The device 10 comprises a receiving cavity 20 for receiving the article 90 and an inductive heating structure for heating the substrate 91 within the article 90 when the article 90 is inserted into the cavity 20.

The article 90 has a rod-shaped form similar to the form of a conventional cigarette. In this embodiment, the article 90 comprises four elements arranged in coaxial alignment: a substrate element 91, a support element 92, an element 94 for cooling the aerosol and a filter plug 95. The substrate element is located at the distal end of the article 90 and contains an aerosol-forming substrate to be heated. The aerosol-forming substrate 91 may include, for example, a corrugated sheet of homogenized tobacco material containing glycerin as an aerosol-forming substance. The support element 92 comprises a hollow core forming a central passage 93 for air. The filter plug 95 serves as a mouthpiece and may include, for example, cellulose acetate fibers. All four elements are essentially cylindrical elements arranged sequentially one after the other. The elements have substantially the same diameter and are surrounded by an outer wrapper 96 made of cigarette paper, so that a cylindrical rod is formed. The outer wrapper 96 can be wrapped around the above elements so that the free ends of the wrapper overlap each other. The wrapper can additionally contain an adhesive that glues the overlapping free ends of the wrapper together.

The device 10 comprises a substantially rod-shaped main body 11 formed by a substantially cylindrical casing of the device. Inside the distant section 13, the device 10 comprises a power source 16, for example, a lithium-ion battery, and an electric circuit 17 including a controller for controlling the operation of the device 10, in particular for controlling the heating process. Inside the near section 14, opposite the distant section 13, the device 10 comprises a receiving cavity 20. The cavity 20 is open at the near end 12 of the device 10, thus providing the possibility of easy insertion of the article 90 into the receiving cavity 20.

The part 21 in the form of the bottom of the receiving cavity separates the distant section 13 of the device 10 from the near section 14 of the device 10, in particular from the receiving cavity 20. Preferably, the part in the form of the bottom is made of a heat-insulating material, for example, PEEK (polyetheretherketone). In this way, it is possible to keep the electrical components inside the distant section 13 separate from the aerosol or residues formed during the process of generating the aerosol inside the cavity 20.

The induction heating structure of the device 10 comprises an induction source including an induction coil 31 for generating an alternating, in particular high-frequency, alternating magnetic field. In this embodiment, the induction coil 31 is a spiral coil encircling the cylindrical receiving cavity 20. The induction coil 31 is made of wire and has a plurality of turns or coils running along its length. The wire may have any suitable cross-sectional shape, such as square, oval or triangular. In this embodiment, the wire has a round cross-section. In other embodiments, the wire may have a flat cross-sectional shape.

The induction heating structure further comprises a current-receiving element 60, which is arranged inside the receiving cavity 20 in such a way that it is exposed to the alternating magnetic field generated by the induction coil 31. In this embodiment, the current-receiving element 60 is a current-receiving blade 61. With its distal end 64, the current-receiving blade is arranged on the part 21 in the form of a bottom of the receiving cavity 20 of the device. From here, the current-receiving blade 61 extends into the interior of the receiving cavity 20 in the direction of the opening of the receiving cavity 20 at the near end 12 of the device 10. The other end of the current-receiving blade 60, i.e. the distal free end 63, is pointed, ensuring the possibility of easy penetration of the current-receiving blade into the aerosol-forming substrate 91 inside the distal end section of the article 90.

When the device 10 is activated, a high-frequency alternating current is passed through the inductance coil 31. This causes the coil 31 to generate a changing magnetic field inside the cavity 20. As a result, the current-collecting blade 61 is heated due to eddy currents and/or hysteresis losses, depending on the magnetic and electrical properties of the materials of the current-collecting element 60. The current collector 60, in turn, heats the aerosol-forming substrate 91 of the article 90 to a temperature sufficient for the formation of an aerosol. The aerosol can be drawn further downstream through the aerosol-generating article 90 for inhalation by the user.

The high frequency alternating magnetic field may be in the range from 500 kHz (kilohertz) to 30 MHz (megahertz), in particular from 5 MHz (megahertz) to 15 MHz (megahertz), preferably from 5 MHz (megahertz) to 10 MHz (megahertz).

In this embodiment, the induction coil 31 is part of the induction module 30, which is located on the near section 14 of the aerosol generating device 10. The induction module 30 has a substantially cylindrical shape and is aligned coaxially with the longitudinal central axis C of the substantially rod-shaped device 10. As can be seen from Fig. 1, the induction module 30 forms at least a section of the cavity 20 or at least a section of the inner surface of the cavity 20.

In Fig. 2, the induction module 30 is shown in more detail. In addition to the induction coil 31, the induction module 30 comprises a tubular internal support sleeve 32 that supports the spirally wound cylindrical induction coil 31. At one end, the tubular internal support sleeve 32 has an annular projection 34 that extends along the circumference of the internal support sleeve 32 to hold the coil 31 in place on the internal support sleeve 32. The internal support sleeve 32 can be made of any suitable material, such as plastic. In particular, the internal support sleeve 32 can be at least a portion of the cavity 20, that is, at least a portion of the inner surface of the cavity 20.

Both of the induction coil 31 and the internal support sleeve 32 (except for the projection 34) are surrounded by a tubular flux concentrator 33, extending along the length of the induction coil 31, which (length) can be in the range from 16 millimeters to 18 millimeters. The flux concentrator 33 is configured to distort the alternating magnetic field generated by the induction coil 31 during use of the device 10, in the direction of the cavity 20. In essence, the flux concentrator 33 acts as a magnetic screen in order to reduce unwanted heating or impact on external objects. In addition, the flux concentrator 33 sets the direction of the magnetic field lines, the distortion of which must be caused, inside the internal volume of the induction module 30 in such a way that the density of the magnetic field inside the cavity 20 increases. This provides the possibility of increasing the current generated inside the current-collecting blade 61 located in the cavity 20. In this way, it is possible to concentrate the electromagnetic field in the direction of the cavity 20 to ensure the possibility of more efficient heating of the current-collecting element 60.

According to the present invention, the flux concentrator 33 is made of a multilayer flux concentrator foil 35. Fig. 3 (not to scale) and Figs. 4a-4b show a corresponding section of the multilayer flux concentrator foil 35 in more detail. Fig. 3 shows a sectional view of the multilayer flux concentrator foil 35. Fig. 4a shows a black and white photograph of a section of a sample of the magnetic layer 36. Fig. 4b shows the magnetic layer 36 according to Fig. 4a with inverted colors to improve the visibility of cracks and fragments 39. As shown in Fig. 3, the multilayer magnetic flux concentrator foil 35 according to the present invention comprises three layers, namely a magnetic layer 36 made of a soft magnetic alloy, a first support layer 37 and a second support layer 36, wherein the magnetic layer 36 is located between the first support layer 37 and the second support layer 38 and forms a layered structure with them. According to the present invention, the magnetic layer 36 comprises a plurality of individual fragments 39. Due to the fragmentation, the formation of eddy currents in the magnetic layer 36 is partially suppressed, since the flake-like fragments 39 are separated from each other, and each individual fragment 39 provides only a limited space for the formation of eddy currents. Therefore, compared to an unfragmented magnetic layer, the fragmented magnetic layer 36 has a reduced resistance to alternating current. As a result, when exposed to an alternating magnetic field, the energy dissipation in the fragments 39 is absent or only insignificant, which leads to the fact that the flux concentrator foil 35 as a whole is heated only slightly, if at all. In this way, it is possible that the main part of the energy provided by the changing magnetic field will be dissipated in the current collector. As shown in Fig. 4a-4b, said plurality of individual fragments 39 may be arranged in a pattern comprising a plurality of cracking centers, wherein the plurality of cracks extend radially outward from each cracking center in a web-like pattern. As can be seen in the figures, each of the individual fragments has different dimensions from the others. The average size of the fragments may be a maximum of 1 millimeter, in particular a maximum of 500 micrometers.

Preferably, the soft magnetic alloy is a nanocrystalline soft magnetic alloy, such as Vitroperm 800. Vitroperm 800 has a maximum relative magnetic permeability of greater than 200,000 at a magnetic field frequency of 50 hertz. Accordingly, this material is particularly suitable for concentrating and directing the magnetic field generated by the induction coil. In addition, Vitroperm 800 is quite brittle, and thus it easily cracks into many fragments.

The first support layer 37 and the second support layer 38 serve primarily to protect the fragile magnetic layer 36, in particular to prevent chipping of the fragmented magnetic layer 36, by binding the fragments 39 of the magnetic layer 36 in a layered structure. For this purpose, the first support layer 37 and the second support layer 38 are preferably adhesive layers. For example, the first and second support layers 37, 38 can be made of transparent glue or plastic tape. Preferably, the material of the first and second support layers 37, 38 is electrically insulating to prevent short-circuiting of individual fragments 39.

In this embodiment, the magnetic layer 36 may have a layer thickness of 20 micrometers. Each of the first support layer 37 and the second support layer 38 may have a layer thickness of 22 micrometers. Accordingly, the flow concentrator foil 35 as a whole may have a thickness of 64 micrometers.

In the embodiment shown in Fig. 1 and Fig. 2, the flow concentrator foil 35 is wound in the form of a single turn so that a tubular flow concentrator or a flow concentrator sleeve is formed, which comprises a single turn of the flow concentrator foil 35 surrounding the inductance coil 31. In principle, the flow concentrator foil 35 can be wound around the inductance coil 31 in different ways. According to the first embodiment, the flow concentrator foil 35 can be wound in such a way that its free ends 351 are adjacent to each other, as shown in Fig. 5. In other words, the longitudinal edges of the layers of the flow concentrator foil 35, which extend along the longitudinal axis C of the aerosol generating device 10, are adjacent to each other. According to the second embodiment, the flow concentrator foil 35 can be wound in such a way that its free ends 351 overlap each other, as shown in Fig. 6. In other words, the longitudinal edges of the flow concentrator foil 35, which extend along the longitudinal axis C of the aerosol generating device 10, are adjacent to each other. According to the third embodiment shown in Fig. 7, the flow concentrator foil 35 can be wound in the form of a plurality of turns so as to form a tubular flow concentrator or a flow concentrator core comprising a plurality of turns, in particular spiral turns, of the flow concentrator foil, overlapping each other. According to the fourth embodiment shown in Fig. 8, the flow concentrator foil 35, 13 can also be wound spirally in the axial direction with respect to the winding axis, that is, along the longitudinal axis C of the aerosol generating device, so as to form a tubular flow concentrator or a flow concentrator core comprising one or more spiral turns of the flow concentrator foil 35, 135.

Fig. 9 shows a second embodiment of the multilayer foil 235 of the flux concentrator. In contrast to the embodiment shown in Fig. 2 and Fig. 3, the multilayer foil 235 of the flux concentrator according to Fig. 9 comprises a plurality of magnetic layers 236 arranged between the first support layer 237 and the second support layer 238 to form a layered structure. In addition, an electrically insulating adhesive film 270 is arranged between each two adjacent magnetic layers 236. In particular, with respect to the multi-turn configuration shown in Fig. 7 and Fig. 8, the plurality of magnetic layers 236 make it possible to limit the number of turns to be wound. As an advantage, this can simplify the manufacture of the flux concentrator.

As shown in the same Fig. 1 and Fig. 2, the flux concentrator foil 35 is directly wrapped around the inductor coil 31 substantially without any radial gap in the radial direction between the inductor coil 31 and the flux concentrator foil 35.

Fig. 10 shows another embodiment of the induction module 130, in which the flow concentrator foil 135 is removed in the radial direction from the induction coil 131. In other words, the aerosol generating device comprises a radial gap 181 between the induction coil 131 and the flow concentrator foil 135. In the illustrated embodiment, the gap 181 is filled with a first dielectric wrap 182. For example, the induction coil 131 can be wrapped with one or more layers of Kapton tape 182 so as to fill the radial gap 181 between the induction coil 131 and the flow concentrator 133. The gap 181 or the first dielectric wrap 182, respectively, can have a radial extension in the range from 40 micrometers to 240 micrometers, for example 80 micrometers. As an advantage, the gap 181 can help to reduce the losses in the inductance coil and increase the losses in the current collector to be heated, that is, to increase the heating efficiency of the aerosol generating device. As an alternative, said gap can be an air gap. In addition, the induction module 130 according to Fig. 10 comprises an electrically conductive shielding wrap 183, which is located around the flow concentrator in order to provide additional shielding of the external parts of the device by electrically closing the field circuit. For example, the electrically conductive shielding wrap 180 can be an aluminum foil, which is wound in the form of one or more turns around the flow concentrator 135. In addition, the induction module 130 comprises a second dielectric wrap 185 made of Kapton tape, which is located around the flux concentrator 135, and a shield wrap 183 for protecting the flux concentrator 135 and the shield wrap 183. Unlike the embodiment shown in Fig. 1 and Fig. 2, the current collecting element 160 according to the embodiment shown in Fig. 10 is a current collecting sleeve 161, which is located on the inner surface of the inner support sleeve 132 in such a way that it surrounds the article when it is placed in the receiving cavity. Except for this, the embodiment shown in Fig. 10 is very similar to the embodiment shown in Fig. 1 and Fig. 2. Therefore, identical or similar features are designated by the same reference numerals, but with an increase of 100.

Fig. 11 shows a schematic cross-sectional view of another embodiment of the aerosol generating system 1 according to the present invention. This system is identical to the system shown in Fig. 1, except for the current collector. Therefore, identical reference numerals are used for identical elements. In contrast to the embodiment shown in Fig. 1, the current collector 68 of the system according to Fig. 11 is not a part of the aerosol generating device 10, but a part of the aerosol generating article 90. In this embodiment, the current collector 68 comprises a current collecting strip 69, which is made of metal, for example stainless steel, and is located inside the aerosol-forming substrate of the substrate element 91. In particular, the current collector 68 is located inside the article 90 in such a way that when the article 90 is inserted into the cavity 20 of the device 10, the current collecting strip 69 is located in the cavity 20, in particular inside the induction coil 31, in such a way that, when used, the current collecting strip 69 is exposed to the magnetic field of the induction coil 31.

Fig. 12-15 show, by way of example, some steps of the method according to the present invention, which is used for producing a multilayer flow concentrator foil of an aerosol generating device according to the present invention. As described above, the method includes, among other things, the step of cracking one or more magnetic layers of the multilayer flow concentrator foil into a plurality of fragments by applying an external force to the flow concentrator foil perpendicular to the plane of the foil. This can be achieved by passing the flow concentrator foil through at least one pair of counter-rotating rollers 710, 720, which are pressed against each other in such a way that the foil passing therethrough is compressed between the two rollers 710, 720. As shown in Fig. 12 and Fig. 13, at least one of the rollers 710 comprises on its outer surface a plurality of protrusions 711, each of which locally applies a force to the flow concentrator foil perpendicular to the plane of the foil. In Fig. 12, each of the upper roller 710 and the lower roller 720 comprises a plurality of projections 711, 721 for the purpose of enhancing the cracking effect. Preferably, the pluralities of projections 711, 721 on both rollers 710, 720 can be designed as complementary projections. For example, in use, the projections 711 of the upper roller 710 can fit between the projections 721 of the lower roller 720. In contrast to this, as shown in Fig. 13, it is also possible that only one of the rollers 710 comprises a plurality of projections 711, while the corresponding other roller 720 comprises a smooth outer surface acting as an opposing surface for the projections 711. It should be noted that for the sake of simplicity, in Fig. 12 and Fig. 13 shows only four rows of projections 711, 721 on the corresponding rollers 710, 720. However, the rollers preferably have more than four rows of projections, uniformly distributed around the circumference of the corresponding rollers.

The method further comprises the step of pulling the flux concentrator foil 35 with a tensile force parallel to the plane of the foil, through at least one edge 730. This is shown in Fig. 14, in which the tensile force is shown by arrow 731. This step results in said fragments cracking into even smaller fragments and, most importantly, in their separation in such a way that they are further separated from each other. As an advantage, this results in an increased reduction in the alternating current resistance of the magnetic layer and, thus, in an increased reduction in the eddy current losses in the magnetic layer of the flux concentrator foil. Preferably, said at least one edge 730 has a curvature radius of a maximum of 0.3 millimetres, in particular a maximum of 0.2 millimetres, preferably a maximum of 0.15 millimetres. The pulling of the foil 35 through the edge 730 can occur at an angle 732 in the range from 60 degrees to 120 degrees, for example, at an angle of 80 degrees, as shown in Fig. 14. The tension force 731 used to pull the foil 35 through the edge 730 can be in the range from 20 N to 60 N, in particular from 25 N to 40 N, for example, 30 N.

In addition, the method may include pulling the flux concentrator foil with a tension force 741 parallel to the plane of the foil through a series of rollers 740 in order to bend the flux concentrator foil 35, as shown in Fig. 15. This step provides the advantage of being able to crack said fragments into even smaller fragments, which leads to an increased decrease in the alternating current resistance of the magnetic layer. This step may be performed before pulling the flux concentrator foil through said at least one edge.

Fig. 16 shows (not to scale) another example of a multilayer flux concentrator foil according to the present invention, which comprises a plurality of magnetic layers. From bottom to top, the multilayer flux concentrator foil of Fig. 16 comprises the following layers:

adhesive (polyethylene terephthalate free) first support layer 340,

a first magnetic layer 350 comprising or made from a soft magnetic alloy,

adhesive (PET-free) intermediate support layer 360,

a second magnetic layer 370 comprising or made from a soft magnetic alloy, and

second adhesive (based on polyethylene terephthalate) support layer 380.

As described in more detail above, the multilayer foil of the flow concentrator can be sealed to prevent the release of fragments from the foil in the transverse direction. For this purpose, on one or on each side of the (unsealed) foil of the flow concentrator according to Fig. 16, a sealing adhesive tape 330, 390 can be arranged. Such a sealed multilayer foil of the flow concentrator is shown in Fig. 17. As can be seen from the figure, the widthwise extension of the adhesive sealing tape 330, 390 in the direction transverse to the opposite edges of the unsealed foil of the flow concentrator is greater than the widthwise extension of the unsealed foil of the flow concentrator in the same direction, that is, in the direction transverse to the opposite edges of the unsealed foil of the flow concentrator. As a result, the sealing adhesive tape 330, 390 on each side of the unsealed flow concentrator foil comprises transversely projecting flaps 335, 395, which can enter into adhesive contact with each other in such a way as to seal the edges of the (unsealed) flow concentrator. Accordingly, the specific example of the sealed multilayer flow concentrator foil according to Fig. 17 comprises the following layers (from bottom to top):

the first adhesive film 331 based on polyethylene terephthalate (the first adhesive sealing tape 330),

adhesive (polyethylene terephthalate free) first support layer 340,

a first magnetic layer 350 comprising or made from a soft magnetic alloy,

adhesive (PET-free) intermediate support layer 360,

a second magnetic layer 370 comprising or made from a soft magnetic alloy,

the second adhesive (based on polyethylene terephthalate) support layer 380, and

a second adhesive film 391 based on polyethylene terephthalate (second adhesive sealing tape 390).

The first and second adhesive films 331, 391 based on polyethylene terephthalate can have a thickness of 2-5 micrometers, in particular 3 micrometers. The adhesive (not based on polyethylene terephthalate) first and second support layers 340, 360 and the third (based on polyethylene terephthalate) support layer 380 can have a thickness in the range of 2 micrometers to 10 micrometers, in particular in the range of 2 micrometers to 5 micrometers, for example 3 micrometers. The first and second magnetic layers 350, 370 can have a thickness in the range of 15 micrometers to 25 micrometers, in particular in the range of 18 micrometers to 23 micrometers, for example 21 micrometers.

Instead of the first and second adhesive films 331, 991 based on polyethylene terephthalate, the first and second sealing tapes 330, 390 may also comprise first and second three-layer adhesive sealing layer structures, each of which comprises a foil (based on polyethylene terephthalate or polyimide) located between the first adhesive layer and the second adhesive layer (not shown in Fig. 17).

For the purposes of the present specification and the appended claims, except where otherwise indicated, all numbers expressing quantities, amounts, percentages, and so forth, are to be understood as modified in all instances by the adverb "about." Furthermore, all ranges include the minimum and maximum points disclosed and include any intermediate ranges therein that may or may not be specifically expressed in numerical form herein. Accordingly, in this context, the number A is to be understood as A ±5 percent of A. In the same context, the number A may be considered to include numerical values that are within the normal standard error of measurement of the property that modifies the number A. The number A, in some instances, when used in the appended claims, may deviate by the percentages expressed in numerical form above, provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. In addition, all ranges include the disclosed maximum and minimum points and include any intermediate ranges therebetween that may or may not be specifically expressed in numerical form herein.

Claims (21)

1. An aerosol generating device for generating an aerosol by inductively heating an aerosol-forming substrate, comprising: a device casing containing a cavity designed to allow the aerosol-forming substrate to be heated to be removably placed therein; an induction heating structure comprising at least one induction coil for generating a changing magnetic field within said cavity, wherein the induction coil is located around at least a portion of the receiving cavity; a flux concentrator located around at least a portion of the induction coil and configured to distort the changing magnetic field of said at least one induction heating structure in the direction of said cavity during use of the device, wherein the flux concentrator comprises a multilayer flux concentrator foil having at least one magnetic layer forming a layered structure with at least a first support layer and containing a plurality of individual fragments made of a soft magnetic alloy, wherein said plurality of individual fragments are arranged in the form of a pattern containing a plurality of cracking centers, wherein the plurality of cracks extend radially outward from each cracking center in the form of a web-like pattern. 2. An aerosol generating device according to claim 1, wherein the soft magnetic alloy is a metallic glass or a nanocrystalline soft magnetic alloy, in particular a nanocrystalline soft magnetic alloy based on Fe. 3. An aerosol-generating article according to claim 1 or 2, wherein the soft magnetic alloy comprises a composition of Fe _100-abcxyz Cu _a M _b T _c Si _x Z _z and up to 0.5 at.% of pollutants, where M is one or more from the group consisting of Nb, Mo and Ta, T is one or more from the group consisting of V, Cr, Co and Ni, and Z is one or more from the group consisting of C, P and Ge, wherein 0.5 at.% < a < 1.5 at.%; 2 at.% b<4 at.%; 0 at.% c<5 at.%; 12 at.%<x<18 at.%; 5 at.%<y<12 at.%; and 0 at.% z<2 at%. 4. An aerosol generating device according to any one of the preceding claims, wherein the multilayer flow concentrator foil comprises a plurality of adjacent magnetic layers. 5. An aerosol generating device according to any one of the preceding claims, wherein the multilayer flow concentrator foil comprises a second support layer on that side of said at least one magnetic layer or, if applicable, said plurality of adjacent magnetic layers, which is opposite the first support layer. 6. An aerosol generating device according to any one of the preceding claims, wherein at least one of the first support layer and, if present, the second support layer is one of an adhesive layer, an electrically insulating layer or an electrically insulating adhesive layer. 7. An aerosol generating device according to any of the preceding claims, wherein the gaps between the individual fragments of said plurality of individual fragments are at least partially filled with an electrically insulating material, in particular at least one of the material of the first support layer or, if present, the material of the second support layer or, if present, the material of the adhesive film between adjacent magnetic layers, or a matrix material made of a soft magnetic alloy. 8. An aerosol generating device according to any one of the preceding claims, wherein a first dielectric wrapper is located between the induction coil and the magnetic flux concentrator around at least a portion of the induction coil. 9. A method for manufacturing a multilayer foil of a flow concentrator of an aerosol generating device according to any of the preceding paragraphs, comprising: - providing a multilayer flux concentrator foil having at least one magnetic layer made of a soft magnetic alloy forming a layered structure with at least a first support layer, - cracking of the magnetic layer into a multitude of separate fragments by applying an external force to the flux concentrator foil perpendicular to the plane of the foil and - stretching the flow concentrator foil by pulling the flow concentrator foil with a tension force parallel to the plane of the foil. 10. The method according to claim 9, wherein cracking the magnetic layer into a plurality of separate fragments comprises passing the flux concentrator foil through at least one pair of rollers that apply a pressing force to the flux concentrator foil passing through them, wherein at least one of these rollers comprises a plurality of projections on its outer surface. 11. The method according to claim 10, wherein the corresponding other roller comprises a smooth outer surface or each of the rollers comprises a plurality of projections on its outer surface. 12. The method according to any one of claims 9-11, wherein pulling the flow concentrator foil comprises pulling the flow concentrator foil with a tension force parallel to the plane of the foil, over at least one edge, in particular over only one edge. 13. The method according to any one of paragraphs. 9-12, further comprising drawing the flow concentrator foil with a tensile force parallel to the plane of the foil, through at least one roller, in particular a series of rollers, for bending the flow concentrator foil. 14. The method according to any one of paragraphs 9-13, further comprising cutting the flow concentrator foil to a given size. 15. The method of claim 14, further comprising sealing one or more cut edges of the flow concentrator foil cut to size.

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