RU2841205C2 - Heater assembly with fastening element - Google Patents

Abstract

FIELD: smoking accessories.

SUBSTANCE: heater assembly (1) for an aerosol-generating device, the heater assembly comprising: first heater casing (2) comprising an air inlet; second heater housing (4) comprising aerosol outlet (10); heating chamber (6) for heating the aerosol-forming substrate, wherein heating chamber (6) is in fluid communication with both air inlet and aerosol outlet (10) to form an air flow path through heater assembly (1); wherein heating chamber (6) is located between first (2) and second (4) heater casings; wherein first (2) and second (4) heater casings are attached to each other by means of fastening element (26), wherein fastening element (26) is configured to apply an axial force to first (2) and second (4) heater casings to bring axially opposite inner surfaces of first (2) and second (4) heater casings into a sealing engagement with corresponding axially opposite end surfaces of heating chamber (6) to seal the air flow path.

EFFECT: heater assembly with a fastening element is disclosed.

20 cl, 6 dwg

Description

The present invention relates to a heater unit for an aerosol generating device (for generating an aerosol). The present invention also relates to an aerosol generating device comprising a heater unit. In particular, but not exclusively, the present invention relates to a hand-held electric aerosol generating device for heating an aerosol-forming substrate to generate an aerosol and delivering the aerosol to the user's mouth. The present invention also relates to an aerosol generating system (for generating an aerosol) comprising an aerosol generating device and an aerosol-forming substrate.

Aerosol generating devices that heat an aerosol-forming substrate to produce an aerosol without burning the aerosol-forming substrate are known in the art. The aerosol-forming substrate is typically provided inside an aerosol-generating article, along with other components such as filters. The aerosol-generating article may be in the form of a rod for inserting the aerosol-generating article into a heating chamber of the aerosol-generating device. A heating element is typically located in or around the heating chamber to heat the aerosol-forming substrate after the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device.

The heating chamber may be located within the housing of the aerosol generating device and form part of the air flow path through the aerosol generating device. It is known to provide seals around the air flow path and between the heating chamber and the housing to prevent leakage of aerosol from the air flow path to other parts of the aerosol generating device, which may cause damage to the electronic components of the device. The seals may be located in direct contact with the heating chamber and are therefore typically made of a heat-resistant polymer, such as silicone or polysiloxane. However, exposure of such polymer seals to heating temperatures of the heating chamber may result in the formation of unwanted by-products that may contaminate the aerosol. In addition, such heating temperatures may degrade the seals over time.

To heat the heating chamber, the aerosol generating device may comprise a flexible heating element arranged around the heating chamber. In order to allow direct contact between the seals and the heating chamber and to reduce heating of the seals, attempts have been made to move the seals away from the heating element, for example at the downstream end of the heating chamber. However, this may result in a compromise in the overall dimensions of the aerosol generating device, for example by using a longer heating chamber, which increases the energy consumption of the heating chamber and reduces the efficiency of the aerosol generating device. In addition, increasing the length of the heating chamber may result in the heating chamber surrounding other components of the aerosol generating article, such as filters, which may be indirectly heated due to the conduction of heat through the heating chamber. Heating of filters results in an undesirable waste of energy.

An alternative to increasing the length of the heating chamber may be to reduce the length of the heating element surrounding the heating chamber. However, this may result in a portion of the aerosol-forming substrate not being covered or surrounded by the heating element, so that the heat must travel a greater distance along the length of the heating chamber to heat this portion of the aerosol-forming substrate, compared to traveling a relatively short distance through the thickness of the wall of the heating chamber. Therefore, the portion of the aerosol-forming substrate that is not surrounded by the heating element may be heated less efficiently than the portion that is surrounded by the heating element. Consequently, the portion of the aerosol-forming substrate that is not surrounded by the heating element may have a lower temperature than the portion that is surrounded by the heating element, which may result in premature condensation of the aerosol in the cooler portion. This may result in less aerosol being delivered to the user.

Another disadvantage of using polymer seals between the heating chamber and the device body is that they provide a heat conduction path that transfers heat from the heating chamber to the materials surrounding the heating chamber. This lost heat reduces the heat available to heat the aerosol-forming substrate and reduces the efficiency of the aerosol-generating device.

It would be desirable to provide a heater assembly for an aerosol generating device with improved sealing of its air flow path. It would be desirable to provide a heater assembly for an aerosol generating device that is more energy efficient and improves aerosol delivery to a user.

According to an example of the present invention, a heater unit for an aerosol generating device is proposed. The heater unit may comprise a first heater housing. The first heater housing may comprise an air inlet. The heater unit may comprise a second heater housing. The second heater housing may comprise an aerosol outlet. The heater unit may comprise a heating chamber for heating an aerosol-forming substrate. The heating chamber may be in fluid communication with the air inlet. The heating chamber may be in fluid communication with the aerosol outlet. The heating chamber may be in fluid communication with both the air inlet and the aerosol outlet to form an air flow path through the heater unit. The heating chamber may be located between the first and second heater housings. The first and second heater housings may be attached to each other by means of a fastener. The fastening element may be configured to apply an axial force to the first and second heater casings. The fastening element may be configured to bring the axially opposite inner surfaces of the first and second heater casings into sealing engagement with the corresponding axially opposite end surfaces of the heating chamber to seal the air flow path.

According to an example of the present invention, a heater unit for an aerosol generating device is proposed. The heater unit comprises a first heater casing comprising an air inlet. The heater unit comprises a second heater casing comprising an aerosol outlet. The heater unit comprises a heating chamber for heating an aerosol-forming substrate. The heating chamber is in fluid communication with both the air inlet and the aerosol outlet to form an air flow path through the heater unit. The heating chamber is located between the first and second heater casings. The first and second heater casings are attached to each other by means of a fastening element, wherein the fastening element is configured to apply an axial force to the first and second heater casings to bring the axially opposite inner surfaces of the first and second heater casings into sealing engagement with the corresponding axially opposite end surfaces of the heating chamber to seal the air flow path.

Preferably, the above-described example of the present invention does not require polymer seals because the air flow path is sealed by direct interaction of the end surfaces of the heating chamber with the inner surfaces of the first and second heater jackets. This thus eliminates the occurrence of undesirable by-products that can be released by heating the polymer seals.

Another advantage of sealing the air flow path by direct interaction of the end surfaces of the heating chamber with the inner surfaces of the first and second heater housings is that no space is required at the ends of the heating system to ensure direct contact between the polymer seals and the heating chamber. Any space at one or more ends of the heating chamber, for example to prevent direct contact between the heating element and the surrounding heater housings, can be significantly reduced. This means that shorter heating chambers can be used and a greater proportion of the length of the heating tube can be heated. This makes it possible to heat the aerosol-forming substrate more efficiently.

Preferably, the cross-sectional area available for heat transfer from the heating chamber is significantly reduced. The heating chamber will typically have a wall thickness that is smaller than the thickness of the polymer seals, for example, 100 microns versus 2 millimeters, respectively. Therefore, the area of the end walls of the heating chamber in contact with the first and second heater shells is smaller than the area of the polymer seals that typically surround the heating chamber. Consequently, the amount of heat loss to the parts of the aerosol generating device surrounding the heating chamber is reduced.

In the context of this document, the term "axial force" refers to a force that acts in a direction parallel to the axis of the heater assembly. For example, the force may act in a direction parallel to the longitudinal axis of the heater assembly.

In the context of this document, the terms "distal", "upstream", "near" and "downstream" describe the relative positioning of components or parts of components of an aerosol-generating device and an aerosol-generating article. Aerosol-generating articles and devices according to the present invention have a proximal end through which, in use, the aerosol exits the article or device for delivery to the user, and have an opposite distal end. The proximal end of the article and the aerosol-generating device may also be referred to as a mouthpiece end. In use, the user draws on the proximal end of the aerosol-generating article to inhale the aerosol generated by the article or the aerosol-generating device. The terms "upstream" and "downstream" refer to the direction of movement of the aerosol through an aerosol-generating article or an aerosol-generating device when a user puffs on the near end of the aerosol-generating article. The near end of the aerosol-generating article is located downstream of the far end of the aerosol-generating article. The near end of the aerosol-generating article may also be referred to as the downstream end of the aerosol-generating article, and the far end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article.

The aerosol outlet may be an opening for accommodating an aerosol-generating article. The aerosol may exit from the opening through the aerosol-generating article located in the heating chamber.

At least one of the first and second heater casings may comprise an internal cavity. The internal cavity may surround the heating chamber. The length of the heating chamber may be greater than the length of the internal cavity. Preferably, due to the fact that the length of the heating chamber is greater than the length of the internal cavity, elastic deformation is caused in at least one of the first and second heater casings. This elastic deformation is supported by a fastening element, wherein the fastening element applies an axial force to the first and second heater casings to ensure sealing interaction between the first and second heater casings and the heating chamber to seal the air flow path.

The first heater jacket may comprise an internal cavity. The internal cavity may surround the heating chamber. The length of the heating chamber may be greater than the length of the internal cavity.

The second heater housing may comprise an internal cavity. The internal cavity may surround the heating chamber. The length of the heating chamber may be greater than the length of the internal cavity.

The first heater casing may comprise a first internal cavity. The second heater casing may comprise a second internal cavity. The first and second internal cavities may jointly surround the heating chamber. The length of the heating chamber may be greater than the sum of the lengths of the first and second internal cavities.

The length of the heating chamber may be greater than the length of the internal cavity in the unassembled state of the heater unit.

The length of the internal cavity may include the depth of the recess formed on the internal surface of the internal cavity of at least one of the first and second heater casings. The length of the internal cavity may include the depth of the recess formed on the internal surface of the internal cavity and the first and second heater casings.

Alternatively, the length of the internal cavity may include solely the length of the internal cavity from the first end of the internal cavity to the second end of the internal cavity of one of the first and second heater housings.

The length of the heating chamber may be from about 0.05 percent to about 8.5 percent greater than the internal cavity, preferably from about 0.5 percent to 5.0 percent greater than the internal cavity, and more preferably from about 1.3 percent to about 3.1 percent greater than the internal cavity. These ranges have been found to be suitable for creating elastic deformation in at least one of the first and second heater housings.

The length of the heating chamber may be from about 0.05 millimeters to about 1.0 millimeters longer than the internal cavity, and preferably from about 0.2 millimeters to about 0.4 millimeters longer than the internal cavity. These ranges have been found to be suitable for creating elastic deformation in at least one of the first and second heater housings.

The first and second heater housings may enclose the heating chamber.

At least one of the first and second heater housings may comprise a material having an elastic modulus or Young's modulus of less than 6 gigapascals, preferably less than 5 gigapascals and more preferably less than 4 gigapascals. These elastic modulus values are typically less than the elastic modulus of the heating chamber material, which means that at least one of the first and second heater housings will elastically deform to a greater extent than the heating chamber, because the heating chamber is made of more rigid materials than the first and second heater housings. It was also found that these elastic modulus values provide a suitable amount of elastic deformation.

The heating chamber may contain a material having an elastic modulus or Young's modulus greater than about 100 gigapascals, preferably greater than about 150 gigapascals and more preferably about 190 gigapascals or more. The heating chamber may contain a material having an elastic modulus or Young's modulus from about 100 gigapascals to about 250 gigapascals, preferably from about 150 gigapascals to about 220 gigapascals and more preferably from about 190 gigapascals to about 205 gigapascals.

At least one of the first and second heater jackets may comprise a material having a glass transition temperature greater than 130 degrees Celsius. At least one of the first and second heater jackets may comprise a material having a melting temperature greater than 280 degrees Celsius. These properties help the material maintain structural stability at temperatures encountered during heating and help reduce the likelihood of forming undesirable by-products.

At least one of the first and second heater housings may comprise a material having a Shore hardness of less than 90A as determined according to technical standard ISO868 using type A.

Preferably, at least one of the first and second heater housings may comprise a material that can be manufactured by injection molding.

At least one of the first and second heater jackets may comprise a polymer. Polymers have been found to be particularly suitable materials due to their elastic properties.

The first and second heater jackets may comprise any suitable material or combination of materials. Examples of suitable materials include plastic or composite materials comprising one or more materials, or thermoplastics suitable for use in food or pharmaceutical production, such as polypropylene, polyetheretherketone (PEEK), polyphenylsulfone (PPSU) and polyethylene. Preferably, at least one of the first and second heater jackets comprises PEEK or PPSU.

At least one of the first and second heater housings may comprise a bevel or inclined edge located on the inner surface of at least one of the first and second heater housings for aligning the heating chamber in the axial direction. Preferably, the bevel or inclined edge helps to accurately determine the location of the heating chamber inside the first and second heater housings.

The fastener may be a threaded fastener or a locking fastener. These types of fasteners have been found to be suitable for fastening the first and second heater housings to each other. The locking fastener or connector has been found to have many additional advantages. For example, the locking fastener may help reduce the size of the heater assembly because it has a reduced profile compared to other types of fasteners. The locking fastener may also help achieve a balanced alignment of the first and second heater housings because it applies a constant amount of axial force that cannot be changed. In addition, locking fasteners help simplify manufacturing because only one pressing operation is required to fasten the first and second heater housings. Additionally, the locking fastener may be formed integrally with the first and second heater housings to reduce the number of parts required for fastening.

The heater assembly may comprise several fastening elements. The first and second heater housings may be attached to each other by means of several fastening elements. Several fastening elements may be symmetrically distributed around the outer perimeter or outer surface of the first and second heater housings. This arrangement helps to apply a constant pressure between the end surfaces of the first and second heater housings, which are in contact with each other along the entire perimeter of the first and second heater housings. As a result, a constant sealing pressure is created between the contact surfaces of the heating chamber and the first and second heater housings along the entire circumference of the tubular heating chamber to ensure improved sealing. The heater assembly may comprise at least two fastening elements located diametrically opposite to each other.

The first and second heater jackets may be radially spaced from the heating chamber to form a hollow air gap around the heating chamber. Preferably, the hollow air gap helps provide thermal insulation for the heating chamber, which helps reduce heat loss from the heating chamber and also helps reduce heat transfer to the outside of the heater assembly.

The first heater housing may comprise an air flow channel. The air flow channel of the first heater housing may be in fluid communication with the air inlet. The second heater housing may comprise an air flow channel. The air flow channel of the second heater housing may be in fluid communication with the aerosol outlet. The heating chamber may comprise an air flow channel. The air flow channel of the heating chamber may extend along the entire length of the heating chamber. The air flow channels of each of the first heater housing, the second heater housing and the heating chamber may be in fluid communication with each other to form an air flow path through the heater assembly.

The heating chamber may comprise a tubular heating chamber. The diameter of the tubular heating chamber at the first end of the tubular heating chamber may be greater than the diameter along the length of the tubular heating chamber. The diameter of the tubular heating chamber at the second end of the tubular heating chamber may be greater than the diameter along the length of the tubular heating chamber. The diameter of the tubular heating chamber at each end of the tubular heating chamber may be greater than the diameter in the region between the two ends of the tubular heating chamber.

Preferably, providing a diameter of one or both ends of the tubular heating chamber that is larger than the diameter of the tubular heating chamber along the length of the heating chamber, for example in the region between the two ends of the tubular heating chamber, allows for large process tolerances for the heating chamber and also for other components of the heater assembly. In particular, this allows for large process tolerances in the radial or transverse directions. In the context of this document, the terms "radial tolerance" or "transverse tolerance" are used to describe process tolerances in a direction substantially perpendicular to the main longitudinal axis or length of the heater assembly or aerosol generating device, for example tolerances that result in components being wider or narrower than their specified design width, or in diameters being larger or smaller than their specified design diameter. Radial or transverse tolerances are sometimes referred to as "horizontal tolerances".

Preferably, due to the fact that the diameter of the end of the tubular heating chamber is larger than other parts of the tubular heating chamber, the internal diameter at one or both ends of the tubular heating chamber will be larger than the internal diameter of the air flow path in other components of the heater assembly with which the tubular heating chamber interacts, i.e., in the first and second heater jackets. This helps to avoid protruding or penetrating the end surface of the tubular heating chamber into the interior of the air flow path, which can possibly lead to damage to the article generating the aerosol when it is placed in the heating chamber through the air flow path, and can leave less end surface of the tubular heating chamber to ensure sealing interaction with other components. This arrangement also makes possible large tolerances in the radial or transverse directions in other components, which is described in more detail below.

The outer diameter of one or both ends of the tubular heating chamber may be up to 20 percent larger, preferably up to 15 percent larger, more preferably up to 12 percent larger, and even more preferably up to 8 percent larger than the outer diameter of the portion of the tubular heating chamber between the two ends of the tubular heating chamber. The outer diameter of one or both ends of the tubular heating chamber may be from 1 percent to 20 percent larger, from 1 percent to 15 percent larger, from 1 percent to 12 percent larger, or from 1 percent to 8 percent larger than the outer diameter of the portion of the tubular heating chamber between the two ends of the tubular heating chamber.

One or both ends of the tubular heating chamber may have an outer diameter of 7.5 millimeters to 9.0 millimeters, preferably 8.0 millimeters to 8.5 millimeters, and more preferably about 8.4 millimeters. The portion of the tubular heating chamber between the two ends of the tubular heating chamber may have an outer diameter of 6.5 millimeters to 8.0 millimeters, preferably 7.0 millimeters to 8.0 millimeters, and more preferably about 7.5 millimeters.

The internal diameter of the heating chamber may substantially correspond to, or be substantially equal to, the external diameter of the aerosol-generating article. In some embodiments, the internal diameter of the heating chamber may be slightly smaller than the external diameter of the aerosol-generating article, so that the aerosol-generating article is compressed in the heating chamber. For example, the external diameter of the aerosol-generating article may be approximately 7.4 millimeters, and the internal diameter of the heating chamber may be approximately 7.3 millimeters. The length of the heating chamber may substantially correspond to, or be substantially equal to, the length of the aerosol-forming substrate provided in the aerosol-generating article.

At least one end portion of the tubular heating chamber may be flared or funnel-shaped. The portion of the tubular heating chamber at both ends of the tubular heating chamber may be flared or funnel-shaped. The axial length of the flared or funnel-shaped end portion of the tubular heating chamber may be from 0.5 percent to 10 percent of the total length of the tubular heating chamber, preferably from 1 percent to 5 percent of the total length of the tubular heating chamber, and more preferably approximately 3.3 percent of the total length of the tubular heating chamber.

The axial length of the flared or funnel-shaped end portion of the tubular heating chamber may be from 0.2 millimeters to 2 millimeters, preferably from 0.4 millimeters to 1 millimeter and more preferably about 0.5 mm. The flared or funnel-shaped end portion or end portions of the tubular heating chamber may be located at an angle of from 30 to 60 degrees, from 40 to 50 degrees or at an angle of about 45 degrees relative to the longitudinal axis of the heating chamber or the heater assembly. In some preferred embodiments, the flared or funnel-shaped end portion or end portions of the tubular heating chamber may be located at an angle of less than 50 degrees, preferably less than 40 degrees or more preferably less than 30 degrees relative to the longitudinal axis of the heating chamber or the heater assembly. Preferably, providing a flared or funnel-shaped end portion or end portions of the tubular heating chamber at an angle of less than 30 degrees relative to the longitudinal axis of the heating chamber or the heater assembly can provide optimum rigidity for the flared or funnel-shaped end portion or end portions of the tubular heating chamber in the direction of the longitudinal axis of the heating chamber or the heater assembly.

At least one end or end portion of the tubular heating chamber may have a stepped profile or be elbowed. The portion of the tubular heating chamber at both ends of the tubular heating chamber may have a stepped profile or be elbowed. The axial length of the stepped or elbowed end portion of the tubular heating chamber may be from 0.5 percent to 10 percent of the total length of the tubular heating chamber, preferably from 1 percent to 5 percent of the total length of the tubular heating chamber and more preferably approximately 3.7 percent of the total length of the tubular heating chamber. Preferably, a certain radius is provided between the stepped or elbowed portions to eliminate sharp edges and stress concentrators.

The axial length of the flared or funnel-shaped end portion of the tubular heating chamber may be from 0.2 millimeters to 2 millimeters, preferably from 0.4 millimeters to 1 millimeter, and more preferably approximately 0.5 mm.

The tubular heating chamber may have a tubular wall thickness of from 0.05 millimeters to 1.00 millimeters, preferably from 0.05 millimeters to 0.50 millimeters, and more preferably about 0.10 millimeters.

The heating chamber may be made of any suitable material including, but not limited to, ceramics or metal or metal alloy. An example of a suitable material is stainless steel.

The heater unit may comprise at least one electric heating element for heating the aerosol-forming substrate. The heater unit may comprise several electric heating elements. The electric heating element or elements may be arranged around the outer surface of the heating chamber or surround it. The electric heating element or elements may be arranged around the inner surface of the heating chamber or surround it. The electric heating element or elements may be part of the heating chamber or made integral with it.

The electric heating element or elements may comprise an electrically resistive material. Suitable electrically resistive materials include, but are not limited to: semiconductors such as doped ceramics, electrically "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys, and composite materials made from a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, alloys containing nickel, cobalt, chromium, aluminum, titanium, zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese, gold and iron, and superalloys based on nickel, iron, cobalt, stainless steel, TimetalTM, KanthalTM and other iron-chromium-aluminum alloys and alloys based on iron, manganese and aluminum. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated in or coated with the insulating material, or vice versa, depending on the kinetics of energy transfer and the desired external physicochemical properties.

One or more heating elements may be made using a metal or metal alloy characterized by a certain relationship between temperature and specific resistance. Heating elements formed in this way may be used both for heating and for monitoring the temperature of the heating element during operation.

The heating element may be applied within or on a rigid carrier material or substrate. The heating element may be applied within or on a flexible carrier material or substrate. The heating element may be formed as a track on a suitable insulating material such as ceramics or glass or polyimide film. The heating element may be sandwiched between two insulating materials.

The heater assembly may comprise a flexible heating element arranged around the outer surface of the heating chamber or surrounding it. The flexible heating element may have a length substantially equal to the length of the aerosol-forming substrate provided in the aerosol-generating article. The heating chamber may be longer than the heating element. The heating chamber may comprise at least one end portion that is not covered or surrounded by the heating element. An end portion that is not covered or surrounded by the heating element may be provided at both ends of the heating chamber. The end portion or portions may serve as separating portions to prevent direct contact between the heating element and other components of the heater assembly. Each end portion or portions may have a length of less than 2 millimeters, preferably less than 1 millimeter and preferably approximately 0.5 millimeters. Preferably, the separating portions will have a lower temperature during heating than the portion of the heating chamber covered or surrounded by the heating element. The separating portions may comprise funnel-shaped end portions or stepped end portions.

The heating chamber may be configured to accommodate at least a portion of an aerosol generating article (as defined below).

According to one example of the present invention, an aerosol generating device is provided. The aerosol generating device may comprise a heater assembly according to any of the heater assemblies described above. The aerosol generating device may comprise a power supply or a power source for supplying power to the heater assembly.

According to one example of the present invention, an aerosol generating device is proposed. The aerosol generating device comprises a heater unit according to any of the heater units described above, and a power supply or power source for supplying electric power to the heater unit.

The power supply may be any suitable power supply, such as a DC voltage source. In one embodiment, the power supply is a lithium-ion battery. Alternatively, the power supply may be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery, such as a lithium-cobalt, lithium-iron phosphate, or lithium-polymer battery.

Preferably, the aerosol generating device is a hand-held aerosol generating device that is comfortably held by the user between the fingers of one hand.

The aerosol generating device may further comprise a control circuit configured to control the supply of electric power to the heater unit. The control circuit may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC) or other electronic circuit capable of providing control. The control circuit may comprise additional electronic components. For example, in some embodiments, the control circuit may comprise any of: sensors, switches, display elements. The power may be supplied to the heater unit continuously after activation of the device or may be supplied intermittently, for example from puff to puff. The power may be supplied to the heater unit in the form of electric current pulses, for example, by means of pulse width modulation (PWM).

The aerosol generating device may comprise a device housing. The device housing may comprise a heater unit, a power supply unit, and a control circuit. The housing may comprise an opening for accommodating an aerosol generating article. The opening may be connected to an aerosol outlet of the second casing of the heater unit to enable insertion of the aerosol generating article into the heating chamber. The housing may comprise an air inlet. The air inlet may be connected to an air inlet of the first casing of the heater unit.

The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of such materials, or thermoplastic materials suitable for applications in the food or pharmaceutical industries, such as polypropylene, polyetheretherketone (PEEK) and polyethylene. The material is preferably lightweight and non-brittle.

According to an example of the present invention, an aerosol generating system is provided, comprising an aerosol generating device according to any of the examples described above. The aerosol generating system may comprise an aerosol generating article, comprising an aerosol forming substrate.

According to an example of the present invention, there is provided an aerosol generating system comprising: an aerosol generating device according to one of the examples described above; and an aerosol generating article comprising an aerosol forming substrate.

In the context of this document, the term "aerosol-generating article" refers to an article containing an aerosol-forming substrate that, when heated in an aerosol-generating device, releases volatile compounds capable of forming an aerosol. The aerosol-generating article is separate from the aerosol-generating device and is designed to be combined with it to heat the aerosol-generating article.

The aerosol-generating article may have a substantially cylindrical shape. The aerosol-generating article may be substantially elongated. The aerosol-forming substrate may have a substantially cylindrical shape. The aerosol-forming substrate may be substantially elongated.

The aerosol-generating article may have a total length of about 30 mm to about 100 mm. The aerosol-generating article may have an outer diameter of about 5 mm to about 12 mm. The aerosol-forming substrate may have a length of about 10 mm to about 18 mm. In addition, the diameter of the aerosol-forming substrate may be from about 5 mm to about 12 mm. The aerosol-generating article may comprise a filter material rod. The filter material rod may be located at the downstream end of the aerosol-generating article. The filter material rod may be a cellulose acetate filter material rod. The filter material rod in one embodiment has a length of about 7 mm, but may have a length of from about 5 mm to about 12 mm.

In one embodiment, the aerosol-generating article may have a total length of about 45 mm. The aerosol-generating article may have an outer diameter of about 7.3 mm, but may have an outer diameter of about 7.0 mm to about 7.4 mm. In addition, the aerosol-generating substrate may have a length of about 12 mm. Alternatively, the aerosol-generating substrate may have a length of about 16 mm. The aerosol-generating article may comprise an outer paper wrapper. In addition, the aerosol-generating article may comprise a gap between the aerosol-generating substrate and the filter material rod. The gap may be about 21 mm or about 26 mm, but may be in the range of about 5 mm to about 28 mm. The gap may be provided by a hollow tube. The hollow tube may be made of cardboard or cellulose acetate.

The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, the aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, 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 glycerol and propylene glycol.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may comprise, for example, one or more of the following: powder, granules, pellets, grains, thin tubes, strips or sheets containing one or more of the following: grass leaves, tobacco leaves, tobacco rib fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco and blown tobacco. The solid aerosol-forming substrate may be in bulk form or may be provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate may contain additional tobacco or non-tobacco volatile flavor compounds intended to be released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules that, for example, contain additional tobacco or non-tobacco volatile flavor compounds, and such capsules may melt during heating of the solid aerosol-forming substrate.

As used herein, "homogenized tobacco" refers to a material formed by agglomerating loose tobacco. The homogenized tobacco may be in the form of a sheet. The homogenized tobacco material may contain more than 5% by weight of aerosol forming agent on a dry weight basis. Alternatively, the homogenized tobacco material may contain from 5% to 30% by weight of aerosol forming agent on a dry weight basis. Sheets of homogenized tobacco material may be formed by agglomerating loose tobacco obtained by grinding or otherwise comminuting one or both of the lamina of tobacco leaf and the stems of tobacco leaf. Alternatively or additionally, the sheets of homogenized tobacco material may contain one or more of tobacco dust, tobacco fines, and other by-products of the loose tobacco generated, for example, during the processing, handling, and shipping of the tobacco. The sheets of homogenized tobacco material may contain one or more intrinsic binders, i.e., tobacco endogenous binders, one or more extrinsic binders, i.e., tobacco exogenous binders, or a combination thereof, to promote agglomeration of the bulk tobacco; alternatively or additionally, the sheets of homogenized tobacco material may contain other additives, including, but not limited to, tobacco and non-tobacco fibers, aerosol forming agents, humectants, plasticizers, flavoring agents, fillers, aqueous and non-aqueous solvents, and combinations thereof.

In a particularly preferred embodiment, the aerosol-forming substrate comprises an assembled corrugated sheet of homogenized tobacco material. As used herein, the term "corrugated sheet" means a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, when the aerosol-generating article is assembled, the substantially parallel folds or corrugations extend along or parallel to the longitudinal axis of the aerosol-generating article. This advantageously simplifies the assembly of the corrugated sheet of homogenized tobacco material to form the aerosol-forming substrate. However, it will be understood that corrugated sheets of homogenized tobacco material for inclusion in an aerosol-generating article may alternatively or additionally have a plurality of substantially parallel folds or corrugations that are located at an acute or obtuse angle to the longitudinal axis of the aerosol-generating article when the aerosol-generating article is assembled. In certain embodiments, the aerosol-forming substrate may comprise an assembled sheet of homogenized tobacco material that is substantially uniformly textured over substantially the entire surface. For example, the aerosol-forming substrate may comprise an assembled corrugated sheet of homogenized tobacco material that comprises a plurality of substantially parallel folds or corrugations that are substantially uniformly spaced across the width of the sheet.

Optionally, the solid substrate forming the aerosol can be provided on or embedded in a thermally stable carrier. The carrier can be in the form of a powder, granules, beads, grains, thin tubes, strips or sheets. Alternatively, the carrier can be a tubular carrier having a thin layer of the solid substrate deposited on its inner surface, or on its outer surface, or on both its inner and outer surfaces. Such a tubular carrier can be made, for example, of paper or a paper-like material, a non-woven mat of carbon fibers, a lightweight metal mesh with open cells or a perforated metal foil, or any other thermally stable polymer matrix.

The solid aerosol-forming substrate may be applied to the surface of the carrier in the form of, for example, a sheet, foam, gel or suspension. The solid aerosol-forming substrate may be applied to the entire surface of the carrier or, alternatively, may be applied in a pattern to provide non-uniform delivery of the flavor additive during use.

Although solid aerosol-forming substrates are mentioned above, it will be understood by those skilled in the art that other forms of aerosol-forming substrate may be used with other embodiments. For example, the aerosol-forming substrate may be a liquid aerosol-forming substrate. If a liquid aerosol-forming substrate is provided, the aerosol-generating device preferably comprises means for retaining the liquid. For example, the liquid aerosol-forming substrate may be retained in a container or a portion for storing the liquid. Alternatively or additionally, the liquid aerosol-forming substrate may be absorbed by a porous carrier material. The porous carrier material may be made of any suitable absorbent plug or piece, such as a foamed metal or plastic material, polypropylene, terylene, nylon fibers or ceramics. The liquid aerosol-forming substrate may be retained in the porous carrier material prior to use of the aerosol-generating device, or alternatively the liquid aerosol-forming substrate material may be released into the porous carrier material during or immediately prior to use. For example, the liquid aerosol-forming substrate may be provided in a capsule. The capsule shell preferably melts upon heating and releases the liquid aerosol-forming substrate into the porous carrier material. The capsule may optionally contain a solid in combination with a liquid.

Alternatively, the carrier may be a non-woven web or a bundle of fibers in which tobacco components have been incorporated. The non-woven web or bundle of fibers may contain, for example, carbon fibers, natural cellulose fibers, or fibers from cellulose derivatives.

According to an example of the present invention, a method for manufacturing a heater assembly for an aerosol generating device is proposed. The method may include providing a first heater housing comprising an air inlet. The method may include providing a second heater housing comprising an aerosol outlet. The method may include providing a heating chamber for heating an aerosol-forming substrate. The method may include arranging the heating chamber so that it is in fluid communication with both the air inlet and the air outlet to form an air flow path through the heater assembly. The method may include arranging the heating chamber between the first and second heater housings. The method may include attaching the first and second heater housings to each other using a fastener. The fastener may be configured to apply an axial force to the first and second heater housings to bring axially opposite inner surfaces of the first and second heater housings into sealing engagement with the corresponding axially opposite end surfaces of the heating chamber to seal the air flow path.

According to an example of the present invention, a method for manufacturing a heater assembly for an aerosol generating device is proposed. The method includes: providing a first heater housing containing an air inlet; providing a second heater housing containing an aerosol outlet; providing a heating chamber for heating an aerosol-forming substrate, and arranging the heating chamber so that it is in fluid communication with both the air inlet and the aerosol outlet to form an air flow path through the heater assembly; arranging the heating chamber between first and second heater housings and attaching the first and second heater housings to each other using a fastener, wherein the fastener is configured to apply an axial force to the first and second heater housings to bring axially opposite inner surfaces of the first and second heater housings into sealing engagement with corresponding axially opposite end surfaces of the heating chamber to seal the air flow path.

The method may further comprise applying an axial compressive force to the first and second heater housings before attaching the first and second heater housings to each other using the fastener. The compressive force may be from 100 newtons to 300 newtons, preferably the compressive force is approximately 200 newtons.

The heating chamber may be pressed into a recess formed on the inner surface of the first heater casing.

The heating chamber may be pressed into a recess formed on the inner surface of the second heater casing.

The features described in relation to one of the above examples may equally be applied to other examples according to the present invention.

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 can be combined with any one or more features of another example, embodiment or aspect described herein.

Example Ex1: A heater assembly for an aerosol generating device, wherein the heater assembly comprises: a first heater housing comprising an air inlet; a second heater housing comprising an aerosol outlet; and a heating chamber for heating an aerosol-forming substrate, wherein the heating chamber is in fluid communication with both the air inlet and the aerosol outlet to define an air flow path through the heater assembly.

Example Ex2: A heater assembly according to example Ex1, wherein the heating chamber is located between the first and second heater housings.

Example Ex3: A heater assembly according to example Ex1 or Ex2, wherein the first and second heater casings are attached to each other by means of a fastening element, wherein the fastening element is configured to apply an axial force to the first and second heater casings to bring axially opposite inner surfaces of the first and second heater casings into sealing engagement with corresponding axially opposite end surfaces of the heating chamber to seal the air flow path.

Example Ex4: A heater assembly according to any of examples Ex1-Ex3, wherein at least one of the first and second heater housings comprises an internal cavity that surrounds the heating chamber, and wherein the length of the heating chamber is greater than the length of the internal cavity in the unassembled state of the heater assembly.

Example Ex5: A heater assembly according to example Ex4, wherein the length of the heating chamber is from about 0.5 percent to about 8.5 percent longer than that of the internal cavity.

Example Ex6: A heater assembly according to example Ex5, wherein the length of the heating chamber is from about 1.0 percent to about 5.0 percent greater than that of the internal cavity.

Example Ex7: A heater assembly according to example Ex6, wherein the length of the heating chamber is from approximately 1.3 percent to approximately 3.1 percent greater than that of the internal cavity.

Example Ex8: A heater assembly according to any preceding example, wherein at least one of the first and second heater housings comprises a material having an elastic modulus of less than 6 gigapascals.

Example Ex9: A heater assembly according to example Ex8, wherein at least one of the first and second heater housings comprises a material having an elastic modulus of less than 5 gigapascals.

Example Ex10: A heater assembly according to example Ex9, wherein at least one of the first and second heater housings comprises a material having an elastic modulus of less than 4 gigapascals.

Example Ex11: A heater assembly according to any previous example, wherein at least one of the first and second heater housings comprises a polymer.

Example Ex12: A heater assembly according to any previous example, wherein at least one of the first and second heater housings comprises a bevel located on the inner surface of at least one of the first and second heater housings for alignment in the axial direction of the heating chamber.

Example Ex13: A heater assembly according to any preceding example, wherein the fastening element comprises a threaded fastening element.

Example Ex14: A heater assembly according to any of examples Ex1-Ex12, wherein the fastening element comprises a locking fastening element.

Example Ex15: A heater assembly according to any preceding example, wherein the heater assembly comprises multiple fasteners.

Example Ex16: A heater assembly according to example Ex15, wherein a plurality of fasteners are symmetrically distributed around the outer perimeter of the first and second heater casings.

Example Ex17: A heater assembly according to any preceding example, wherein each of the first heater housing, the second heater housing and the heating chamber comprises an air flow passage, wherein the air flow passages communicate to form an air flow path.

Example Ex18: A heater assembly according to any preceding example, wherein the heating chamber comprises a tubular heating chamber.

Example Ex19: A heater assembly according to example Ex18, wherein the diameter of the tubular heating chamber at each end of the tubular heating chamber is larger than the diameter of the tubular heating chamber in the region between the two ends of the tubular heating chamber.

Example Ex20: A heater assembly according to example Ex18 or Ex19, wherein each end of the tubular heating chamber is flared or funnel-shaped.

Example Ex21: A heater assembly according to example Ex20, wherein the axial length of the flared or funnel-shaped end of the tubular heating chamber is from 0.5 percent to 10 percent of the total length of the tubular heating chamber.

Example Ex22: A heater assembly according to example Ex18 or Ex19, wherein each end of the tubular heating chamber has a stepped or elbow profile.

Example Ex23: A heater assembly according to example Ex22, wherein the axial length of the stepped or elbow end of the tubular heating chamber is from 0.5 percent to 10 percent of the total length of the tubular heating chamber.

Example Ex24: An aerosol generating device comprising: a heater unit according to any one of the preceding claims; and a power supply unit for supplying electrical power to the heater unit.

Example Ex25: A method of manufacturing a heater assembly for an aerosol generating device, wherein the method comprises: providing a first heater housing comprising an air inlet; providing a second heater housing comprising an aerosol outlet; providing a heating chamber for heating an aerosol-forming substrate, and arranging the heating chamber so that it is in fluid communication with both the air inlet and the aerosol outlet to form an air flow path through the heater assembly; arranging the heating chamber between first and second heater housings; securing the first and second heater housings to each other using a fastener, wherein the fastener is configured to apply an axial force to the first and second heater housings to bring axially opposite inner surfaces of the first and second heater housings into sealing engagement with corresponding axially opposite end surfaces of the heating chamber to seal the air flow path.

Example Ex26: The method according to example Ex25, further comprising applying an axial compressive force to the first and second heater housings before attaching the first and second heater housings to each other using the fastener.

The examples will now be further described with reference to the drawing figures, where:

Fig. 1 shows a longitudinal section of a heater assembly according to an example of the present invention.

Fig. 2A is a schematic view in longitudinal section of the heater assembly of Fig. 1 in an unassembled state with the heating chamber located outside the heater casings.

Fig. 2B is a schematic view in longitudinal section of the heater assembly of Fig. 1 immediately prior to assembly with the heating chamber located outside the heater housings.

Fig. 3A is a longitudinal sectional view of a heater assembly according to another example of the present invention.

Fig. 3B is an enlarged partial view of the heater assembly located in the area designated D in Fig. 3A.

Fig. 4A and 4B are side views of two exemplary heating chambers for use in a heater assembly according to the present invention.

Figs. 5A-5C are schematic partial cross-sectional views of known tubular heating chambers showing problems that may arise due to process tolerances resulting from pressing the heating chambers into the heater housing.

Fig. 6 is a schematic sectional view showing the inside of an aerosol generating device according to an example of the present invention and an aerosol generating article disposed inside the aerosol generating device.

Fig. 1 shows a longitudinal section of a heater unit 1 comprising a first heater housing 2, a second heater housing 4 and a heating chamber 6 for heating an aerosol-forming substrate. The first heater housing 2 comprises a substantially flat support section 2a and a first tubular section 2b. The support section 2a of the first heater housing 2 has an inner surface 2c which faces the second heater housing 4. An air inlet (not shown) is located at the distal end of the first tubular section 2b, wherein the first tubular section 2b extends in a distal direction from the support section 2a in a direction parallel to the longitudinal axis X-X of the heater unit 1.

The second heater housing 4 comprises a hollow section 4a of the shell and a second tubular section 4b. The hollow section 4a of the shell has an internal cavity 4c which surrounds the heating chamber 6 and is open at its distal end to allow the heating chamber to be placed inside the internal cavity 4c. The internal cavity 4c of the hollow section 4a of the shell is closed at its distal end by the internal surface 2c of the support section 2a of the first heater housing 2. The outlet opening 10 for the aerosol is located at the near end of the second tubular section 4b, wherein the second tubular section 4b extends in the proximal direction from the hollow section 4a of the shell in a direction parallel to the longitudinal axis X-X of the heater assembly 1. The outlet opening 10 for the aerosol is defined by an opening 12 which is configured to receive an article generating an aerosol (not shown). The aerosol exits from the opening 10 through the aerosol generating article placed in the heating chamber 6.

The heating chamber 6 comprises a tubular heating chamber made of a stainless steel tube. The heating element 8 is arranged around the outer surface of the heating chamber for heating the heating chamber 6, which in turn heats an aerosol-forming substrate (not shown) located inside the inner space of the tubular heating chamber 6. The heating element comprises a heat-resistant flexible polyimide film containing electrically resistive heating tracks (not shown) formed in a loop-shaped pattern on the film. The resistive heating tracks are connected to an electric power supply (not shown) and generate heat when an electric current is passed through them. The heating element is arranged along substantially the entire length of the tubular heating chamber 6 for heating substantially the entire length of the tubular heating chamber 6.

The heating chamber 6 rests on the support section 2a of the first heater casing 2. The far or first end 6a of the heating chamber 6 is pressed inside the first recess 14 formed in the second side 2c of the first heater casing 2. The inner circumferential edge of the recess 14 has an inclination or bevel 16 for placing the heating chamber 6 in the recess 14 and for the correct alignment of the heating chamber 6 relative to the longitudinal axis X-X of the heater unit 1. The near or second end 6b of the heating chamber 6 is pressed inside the second recess 18 formed on the inner surface of the internal cavity 4c of the second heater casing 4. The inner circumferential edge of the recess 18 has an inclination or bevel 20 for placing the heating chamber 6 in the recess 18 and for the correct alignment of the heating chamber 6 relative to the longitudinal axis X-X of the heater unit 1. The second recess 18 is located opposite in the axial direction relative to the first recess 14 in a direction parallel to the longitudinal axis X-X of the heater unit 1.

The first 2 and second 4 heater casings are attached to each other and cover the heating chamber 6. The far end of the second heater casing 4 has two projections or connecting elements 22 located diametrically opposite to each other on the outer surface of the second heater casing 4. Each projection 22 has an opening 24 for accommodating a screw 26. Two projections or connecting elements 28 are located on the near end of the first heater casing 2 in places corresponding to the projections 22. Each of the projections 28 has an opening 30 for accommodating a screw 26. To secure the first 2 and second 4 heater casings, the near end of the first casing 2 is brought into interaction with the far end of the second casing 4, and the screw 26 is inserted through the openings 24 and 30 for fixing the first 2 and second 4 heater casings in interaction. Thus, screw 26 acts as a fastening element holding the first 2 and second 4 heater casings in interaction with each other.

The side wall of the inner cavity 4c of the second 4 heater casing is radially removed from the heating chamber 6 to form a hollow air gap 13 around the heating chamber 6. The hollow air gap 13 helps to provide thermal insulation for the heating chamber 6, which helps to reduce heat loss from the heating chamber 6 and also helps to reduce heat transfer to the outside of the heater assembly 1 and the aerosol generating device.

The first 2 and second 4 heater housings are made of polyetheretherketone (PEEK) due to its preferable thermal insulation and mechanical properties. PEEK has a lower thermal conductivity than the tubular heating chamber 6 made of stainless steel, which helps reduce heat transfer or loss through the first 2 and second 4 heater housings. This also helps maintain the temperature of the outer surface of the heater assembly 1 at a lower level than the temperature of the outer surface of the heating chamber 6. In addition, this helps retain heat inside the heating chamber to improve aerosol generation.

Another advantage of PEEK is that its modulus of elasticity or Young's modulus is lower than that of stainless steel. The modulus of elasticity of PEEK is typically in the range of 3.7 to 3.95 gigapascals, while the modulus of elasticity of stainless steel is in the range of 190 to 203 gigapascals, although these values may vary depending on the specific composition of each material. These values mean that when a force is applied to the heater assembly 1, the first 2 and second 4 heater housings will elastically deform to a greater extent than the heating chamber 6, since the heating chamber is stiffer than the first 2 and second 4 heater housings. It has been found that such an advantageous elastic deformation is unexpectedly advantageous for heater assemblies according to the present invention, as discussed in more detail below.

The tubular heating chamber 6 is located between the first 2 and second 4 heater housings. The tubular heating chamber 6 has a length that is slightly longer (by 0.5-8.5 percent) than the length of the internal cavity 4c in the second heater housing 4 (including the depth of the second recess 16 in the second heater housing 4 and the depth of the first recess 14 in the first heater housing 2). The difference in length between the heating chamber 6 and the internal cavity 4c is not visible in the assembled state, as shown in Fig. 1, but this difference in length is shown and discussed in more detail below in connection with Figs. 2A and 2B. When the first 2 and second 4 heater housings are attached to each other around the heating chamber 6, the somewhat longer and more rigid heating chamber 6 causes an elastic deformation of the first 2 and second 4 heater housings when their corresponding ends are brought into interaction. The first 2 and second 4 heater casings are held in an elastically deformed state by screws 26, which hold the first 2 and second 4 heater casings in interaction with each other. The screws 26 apply an axial force (designated by arrows A in Fig. 1) to the first 2 and second 4 heater casings in a direction parallel to the longitudinal axis X-X of the heater unit 1. Under the action of the axial force, the inner surfaces of the first 14 and second 16 recesses enter into a sealing interaction with the end surfaces of the corresponding first 6a and second 6b ends of the heating chamber 6. The sealing interaction occurs under the action of the compressive force (indicated by arrows B in Fig. 1), arising at the interface between the heating chamber 6 and the first 2 and second 4 heater casings under the action of the axial force created by the screws 26. Local plastic deformation of the first 2 and second 4 heater casings occurs in the region of the interface between the heating chamber 6 and the first 2 and second 4 heater casings (i.e., in the region between the arrows B in Fig. 1), which contributes to achieving a seal.

As mentioned above, screws 26 are located diametrically opposite to each other in corresponding projections 22, 28 on the outer surfaces of the first 2 and second 4 heater casings. Such symmetrical arrangement of screws relative to the longitudinal axis X-X of the heater unit 1 makes it possible to create a constant pressure between the end surfaces of the first 2 and second 4 heater casings, which contact each other along the entire circumference of the first 2 and second 4 heater casings. As a result of this, a constant pressure, a constant sealing pressure, is created between the contact surfaces of the heating chamber 6 and the first 2 and second 4 heater casings along the entire circumference of the tubular heating chamber 6.

The tubular heating chamber 6 has an air flow channel 32 defined by the internal space of the tubular heating chamber 6, wherein the air flow channel 32 extends in the axial direction along the length of the heating chamber 6 in a direction parallel to the longitudinal axis X-X of the heater unit 1. In addition, the first tubular section 2b of the first heater casing 2 contains an air flow channel 34, and the second tubular section 4b of the second heater casing 4 contains an air flow channel 36. The air flow channels 34, 32 and 36 of the first tubular section 2b, the tubular heating chamber 6 and the second tubular section 4b are respectively in fluid communication with each other to form an air flow path 38 through the heater unit 1 between the air inlet (not shown) and the aerosol outlet 10. The heating chamber 6 is therefore in fluid communication with both the air inlet and the aerosol outlet 10.

The heating chamber 6 is aligned in the axial direction with the first 2b and second 4b tubular sections of the first 2 and second 4 heater casings, respectively. Therefore, the axial force (indicated by arrows A in Fig. 1) applied by screws 26 helps to bring the heating chamber 6 and the housings of the first 2 and second 4 heaters into a sealing interaction with each other to seal the air flow path 38 and reduce the likelihood of aerosol leakage from the air flow path 38 at the intersections between the heating chamber 6 and the first 2 and second 4 heater casings. Such a sealing interaction is achieved as a result of elastic deformation of the first 2 and second 4 heater casings without using polymer seals. Thus, this scheme makes it possible to reduce the likelihood of the release of undesirable by-products.

The first heater casing 2 has a step or stop 39 formed on the inner surface of the first tubular section 2b inside its air flow channel 34. The stop 39 is arranged to engage with the distal end of the aerosol-generating article (not shown) to prevent the distal end of the aerosol-generating article from moving beyond the stop 28 and to accurately position the aerosol-forming substrate provided inside the aerosol-generating article inside the heating chamber 6.

Fig. 2A shows a schematic view in longitudinal section of the heater unit 1 of Fig. 1 in an unassembled state. For clarity, the tubular heating chamber 6 is shown outside the first 2 and second 4 heater casings. The first 2 and second 4 heater casings are shown so that the distal end 4d of the second heater casing touches the near end 2d of the first heater casing 2, but without any elastic deformation of the first 2 and second 4 heater casings. The axial length l _h of the tubular heating chamber 6 is greater than the axial length l _c of the internal cavity 4c by the amount of the difference in lengths l _d . In this example, the length l _c of the internal cavity 4c includes the depth of the recesses 14 and 18 formed in the first 2 and second 4 heater casings, and is measured from the upper or near flat internal surface of the recess 18 in the second heater casing 4 to the lower or far flat internal surface of the recess 14 in the first heater casing 2. The internal surfaces of the recesses 14 and 18 are part of the internal surface of the first 2 and second 4 heater casings, respectively.

It should be understood that in some examples of heater assemblies it is possible not to use recesses for accommodating the heating chamber 6, but simply rely on the axial force applied by the screws 26 in Fig. 1 to hold the heating chamber in place. With such an arrangement, the length l _c of the inner cavity will simply be the length of the inner cavity 4c of the second 4 heater casing, that is, the axial length from the far end 4d of the second heater casing to the inner surface of the upper or near end wall 4e of the second heater casing.

Fig. 2B shows a schematic view in longitudinal section of the heater unit 1 of Fig. 1 immediately before assembly. The heating chamber 6 is located inside the inner cavity 4c of the second heater casing and is located in the axial direction between the first 2 and second 4 heater casings. Due to the difference in length l _d between the tubular heating chamber 6 and the inner cavity 4c, the far end 4d of the second 4 heater casing is spaced from the near end 2d of the first casing 2 by a distance l _d .

In order to assemble the heater 1, a compressive force (indicated by arrows C in Fig. 2B) equal to approximately 200 Newtons is applied to the heater 1 as a whole. Under the action of the compressive force C, the distant end 4d of the second heater casing comes into interaction with the near end 2d of the first heater casing 2 and closes the space or gap between the first 2 and second 4 heater casings. The longer and more rigid heating chamber 6 causes an elastic deformation of the first 2 and second 4 heater casings, as described above. The screws 26 are inserted into the holes 24, 30 formed in the projections 22, 28 when the compressive force C is applied and are tightened to hold the first 2 and second 4 heater casings in interaction. Then the compressive force C is removed. The screws 26 maintain elastic deformation in the first 2 and second 4 heater casings after the compressive force C is removed. As a result, the screws 26 apply an axial force to the first 2 and second 4 heater casings, as described above, to hold the first 2 and second 4 heater casings in sealing engagement with the tubular heating chamber 6.

It should be noted that Fig. 2A and 2B are schematic and not drawn to scale. For clarity, the figures have been simplified by omitting some details and changing or increasing the size of features.

Fig. 3A shows a longitudinal section of a heater assembly 1 according to another example of the present invention. The structure of the heater assembly 1 in Fig. 3A is identical to the structure in Fig. 1, except that the first 2 and second 4 heater housings are fastened to each other using a snap-in connector 40 instead of a screw 26 and projections 22, 28 in Fig. 1.

Like the screws 26 in Fig. 1, the snap-on connectors 40 hold the first 2 and second 4 heater casings in an elastically deformed state and hold the first 2 and second 4 heater casings in interaction with each other. The snap-on connectors 40 apply an axial force to the first 2 and second 4 heater casings in a direction parallel to the longitudinal axis X-X of the heater assembly 1. The axial force counteracts the elastic deformation of the first 2 and second 4 heater casings, which would otherwise lead to the first 2 and second 4 heater casings coming out of interaction. Under the action of the axial force, the inner surfaces of the first 14 and second 16 recesses enter into a sealing interaction with the end surfaces of the corresponding first 6a and second 6b ends of the heating chamber 6, thereby sealing the air flow path 38. The sealing interaction occurs under the action of a compressive force (indicated by arrows B in Fig. 3A) arising at the interface between the heating chamber 6 and the first 2 and second 4 heater casings under the action of an axial force applied by the snap-in connectors 40. Local plastic deformation of the first 2 and second 4 heater casings occurs in the region of the interface between the heating chamber 6 and the first 2 and second 4 heater casings (i.e., in the region between arrows B in Fig. 3A), which helps to achieve sealing.

As well as the screws 26 in Fig. 1, the snap-on connectors 40 are arranged diametrically opposite to each other on the outer surfaces of the first 2 and second 4 heater casings. Such a symmetrical arrangement of the snap-on connectors relative to the longitudinal axis X-X of the heater unit 1 makes it possible to create a constant pressure between the end surfaces of the first 2 and second 4 heater casings, which are in contact with each other along the entire circumference of the first 2 and second 4 heater casings. As a result of this, a constant pressure, a constant sealing pressure, is created between the contact surfaces of the heating chamber 6 and the first 2 and second 4 heater casings along the entire circumference of the tubular heating chamber 6.

Fig. 3B shows an enlarged view of one of the snap-on connectors 40 of the heater assembly 1 located in the rectangle designated D in Fig. 3A. The snap-on connector 40 comprises a console 42 and a latch 44. The latch 44 is located at the near end of the console 42. The console 44 and the latch 44 form a single unit with the first heater housing 2 at the edge of the near side of the first heater housing 2. The snap-on connector 40 further comprises a groove 46 formed on the inner surface of the second heater housing 4 near the far end of the second heater housing 4. The groove 46 is designed to receive the latch 44. The latch 44 has an inclined front edge, and the console 42 is capable of elastically deforming to allow the latch to pass into the internal cavity of the second casing 4 of the heater and into the groove 46. The latch 44 has a square rear edge, which prevents the latch 44 from being removed from the groove 46 after the latch 44 is in the groove 46.

As can be seen from Fig. 3A, the snap-on connector 40 reduces the dimensions of the heater assembly 1, since there is no need to use the screws and protrusions shown in Fig. 1. Snap-on connectors also help to achieve a balanced alignment of the components of the heater assembly, since the same axial force is applied to each of them. In addition, they allow for simplification of production due to the fact that only one pressing operation is required to attach the first 2 and second 4 heater housings, and also reduce the number of parts required for attachment.

Fig. 4A and 4B are side views of two exemplary heating chambers for use in a heater assembly according to the present invention. Referring to Fig. 4A, a first exemplary heating chamber 6A is shown. The heating chamber 6A comprises a stainless steel pipe having a circular cross-section. A hollow internal space within the tubular heating chamber 6A has an internal diameter substantially corresponding to the external diameter of an aerosol-generating article, so that the tubular heating chamber 6A can receive an aerosol-generating article (not shown) within the internal space. A portion 7a of the heating chamber 6A at each end of the heating chamber 6A is flared outward to form a funnel shape at each end of the heating chamber 6A. Each of the flared portions 7a has a length l ₁ , and the percentage of the total length l of the heating chamber 6A, which each length l ₁ of the flared portions constitutes, can be in the range from 1 to 5 percent. Each of the flared end portions 7a of the heating chamber 6A forms an angle of approximately 45 degrees with the longitudinal axis of the heating chamber 6A. Due to the flared end portions 7a, the outer diameter D at the two ends of the heating chamber 6A is larger than the outer diameter d of the heating chamber 6A between the two flared end portions 7a.

The portion 9a of the heating chamber 6A between the two flared end portions 7a has straight sides which are parallel to the longitudinal axis of the heating chamber 6A. The straight portion 9a of the heating chamber 6A has a length l ₂ which substantially corresponds to the length of the aerosol-forming substrate provided in the aerosol-generating article configured to be placed inside the heating chamber 6A. Substantially the entire length l ₂ of the straight portion 9a of the heating chamber 6A is surrounded by a flexible heating element (not shown, but described above with reference to Fig. 1). The flared portions 7a of the heating chamber 6A are not surrounded by a heating element and serve as separators between the ends of the heating element and the components which support the heating chamber 6A, i.e. the first and second heater housings, and help to prevent direct contact between these components and the heating element.

With reference to Fig. 4B, a second exemplary heating chamber 6B is shown. The heating chamber 6B has essentially the same structure as the heating chamber 6A in Fig. 4A, with the exception that instead of flared end portions, the heating chamber 6B has stepped or cranked end portions 7b. That is, a portion 7b of the heating chamber 6B at each end of the heating chamber 6B is stepped or cranked in a radially outward direction to form a step at each end of the heating chamber 6B. Each of the stepped portions 7b has a length l ₁ , and the percentage of the total length l of the heating chamber 6B that each length l ₁ of the stepped portions constitutes may be in the range of from 1 to 5 percent. Due to the stepped end portions 7b, the outer diameter D at the two ends of the heating chamber 6B is larger than the outer diameter d of the heating chamber 6B between the two stepped end portions 7b.

The portion 9b of the heating chamber 6B between the two stepped end portions 7b has straight sides that are parallel to the longitudinal axis of the heating chamber 6B. The straight portion 9b of the heating chamber 6B has a length l ₂ that substantially corresponds to the length of the aerosol-forming substrate provided in the aerosol-generating article configured to be placed inside the heating chamber 6B. Substantially the entire length l ₂ of the straight portion 9b of the heating chamber 6B is surrounded by a flexible heating element (not shown, but described above with reference to Fig. 1). The stepped portions 7b of the heating chamber 6B are not surrounded by a heating element and serve as separators between the ends of the heating element and the components that support the heating chamber 6B, i.e. the first and second heater housings, and help to prevent direct contact between these components and the heating element. The heating chamber 6B also comprises a transition portion 11 between each stepped portion 7b and the straight portion 9b to provide an inclined or curved transition between the outer diameter D of each stepped portion and the outer diameter d of the straight portion.

Fig. 5A-5C are schematic cross-sectional views of portions of prior art straight wall tubular heating chambers illustrating problems that can arise from manufacturing tolerances in the process of pressing such heating chambers into engagement with the heater shell. Manufacturing tolerances can result in component dimensions that are larger or smaller than the specified design length, which can lead to problems with joining tightly fitted components. Achieving very accurate manufacturing tolerances is more problematic in rapid manufacturing technologies such as injection molding.

With reference to Fig. 5A, there is shown the upper part of a known or conventional tubular heating chamber 6 pressed into a recess 16 in the upper casing 4 of the heater. The entire length of the tubular heating chamber 6 is straight, that is, it has a constant outer diameter along its entire length, and the tubular heating chamber 6 does not have a flared or stepped end portion, like the tubular heating chambers 6A and 6B in Figs. 4A and 4B. As can be seen in Fig. 5A, the inner diameter d ₁ of the heating chamber 6 is smaller than the inner diameter d ₂ of the opening 15 in the heater casing 4, through which the aerosol-generating article passes during the insertion of the aerosol-generating article into the heating chamber 6. As a result, a portion with a thickness t of each of the walls, i.e. the end surface, of the heating chamber 6 projects into the inner space defined by the inner diameter d2 of the opening 15. This forms a sharp projection 17 in the opening 15, which may damage the aerosol-generating article when the aerosol-generating article is inserted through the opening 15, or may make the insertion of the aerosol-generating article impossible. A similar situation may arise if the width w of the recess 16 is less than the thickness t of the walls of the tubular heating chamber 6. In this case, there is not enough space inside the recess 16 to accommodate the ends of the tubular heating chamber 6, and, therefore, the ends will protrude into the internal space defined by the internal diameter d2 of the opening 15.

It should be noted that a situation similar to that shown in Fig. 5A may occur at the lower, or upstream, end of the tubular heating chamber 6. Sharp projections at the upstream end of the heating chamber may present a problem in that residues or deposits form in the cracks formed by the projection, which may be difficult to remove or clean out with a cleaning tool.

In Fig. 5B, a lower part of a known or conventional tubular heating chamber 6 is shown, pressed into a recess 14 in a lower casing 2 of the heater. As in Fig. 5A, the entire length of the tubular heating chamber 6 is straight. The inner diameter d3 of the heating chamber 6 is larger than the inner diameter d4 of the opening 19 formed in the lower casing 2 of the heater, through which a part of the aerosol-generating article protrudes, when the aerosol-generating article is properly positioned in the heating chamber 6. As a result, a sharp projection 21 is formed in the opening 19, which can damage the aerosol-generating article when the aerosol-generating article passes through the opening 19, or can make it impossible to completely insert the aerosol-generating article.

It should be noted that a situation similar to that shown in Fig. 5B may occur at the upper, or downstream, end of the tubular heating chamber 6. Sharp projections at the downstream end of the heating chamber may present a problem in that residues or deposits form in the cracks formed by the projection, which may be difficult to remove or clean out with a cleaning tool.

Fig. 5C shows the upper part of a known or conventional tubular heating chamber 6 to be pressed into a recess 16 in the upper heater casing 4. As in Fig. 5A and 5C, the entire length of the tubular heating chamber 6 is straight. The outer diameter d5 of the tubular heating chamber 6 is smaller than the inner diameter of the opening 15 in the heater casing 4 through which the aerosol-generating article passes during the insertion of the aerosol-generating article into the heating chamber 6. As a result, pressing is impossible in this case, since the tubular heating chamber 6 would simply pass through the opening 15.

Fig. 5D is a schematic cross-sectional view of the upper portion of the tubular heating chamber 6A according to Fig. 4A. As described above, the tubular heating chamber 6A has walls with a funnel-shaped or flared end portion 7a. The flared end portion 7a has been pressed into the recess 16 of the second heater casing 4. The outer diameter D of the flared end portion 7a is larger than the outer diameter d of the portion of the tubular heating chamber 6A between the two flared end portions 7a (only one flared end portion is visible in Fig. 5D). The outer diameter D of the flared end portion 7a is also larger than the inner diameter d ₇ of the opening 15 in the heater casing 4, through which the aerosol-generating article passes during the insertion of the aerosol-generating article into the heating chamber 6. The outer diameter D of the flared end portion 7a is larger than the inner diameter d ₇ of the opening 15, even when permissible technological deviations of the inner diameter d ₇ in the radial or transverse directions are taken into account.

The arrangement according to Fig. 5D significantly reduces the probability of protruding a portion of the end surfaces 6c of the walls of the tubular heating chamber 6A within the diameter d ₇ and the cross-section of the air flow path, which is defined in Fig. 5D by the diameter d ₇ . In addition, the end surfaces 6c of the walls of the tubular heating chamber 6A are located at an angle relative to the cross-section of the air flow path defined by the diameter d ₇ , which further reduces the probability of protruding a portion of the end surfaces 6c of the walls of the tubular heating chamber 6A into the air flow path. The arrangement according to Fig. 5D and, in particular, the use of the tubular heating chamber 6A with flared or funnel-shaped end portions 7a make it possible to use components with large permissible deviations in the radial or transverse directions and are therefore suitable for rapid manufacturing technologies. The arrangement according to Fig. 5D also significantly reduces the risk of damage to the aerosol generating article when the aerosol generating article is inserted into the heating chamber 6A.

It should be noted that the tubular heating chamber 6B of Fig. 4B could also be used in the arrangement of Fig. 5D instead of the heating chamber 6A with the same advantages. The larger outer diameter D in the region of the stepped end portions 7b of the heating chamber 6B reduces the likelihood of a portion of the end surfaces of the walls of the tubular heating chamber 6B protruding within the diameter d ₇ of Fig. 5D and into the air flow path. The heating chamber 6B also makes it possible to use components with large tolerances in the radial or transverse directions and reduces the risk of damage to the aerosol-generating article when the aerosol-generating article is inserted into the heating chamber 6B.

It should be noted that Figs. 5A-5D are schematic and not drawn to scale. For clarity, the figures have been simplified by omitting some details and changing or increasing the size of features.

Fig. 6 is a schematic cross-sectional view showing the interior of the aerosol generating device 100 and the aerosol generating article 200 disposed inside the aerosol generating device 100. Together, the aerosol generating device 100 and the aerosol generating article 200 form an aerosol generating system. In Fig. 6, the aerosol generating device 100 is shown in a simplified manner. In particular, the elements of the aerosol generating device 100 are not shown to scale. In addition, elements that are not essential for understanding the aerosol generating device 100 have been omitted.

The aerosol generating device 100 comprises a housing 102 which may comprise a heater assembly 1 either according to Fig. 1 or according to Fig. 3A, a power supply unit 103 and a control circuit 105. Fig. 6 shows a first heater housing 2, a heating chamber 6 and a second heater housing 4. As described above with reference to Fig. 1, the heating chamber 6 comprises a flexible heating element (not shown) arranged around it for heating the heating chamber 6. The power supply unit 103 is a battery, and in this example it is a rechargeable lithium-ion battery. The control circuit 105 is connected to both the power supply unit 103 and the heating element and controls the supply of electrical energy from the power supply unit 103 to the heating element for regulating the temperature of the heating element.

The housing 102 comprises an opening 104 at the near, or mouthpiece, end of the aerosol generating device 100, through which the aerosol generating article 200 is inserted. The opening 104 is connected to the opening 12 in the heater 1 assembly of Fig. 1, through which the aerosol exits the heater unit 1. However, it should be borne in mind that the aerosol mainly exits the heater unit 1 and the aerosol generating device 100 through the aerosol generating article 200. The housing 102 further comprises an air inlet 106 at the far end of the aerosol generating device 100. The air inlet 106 is connected to an air inlet located at the far end of the first tubular section 2b of the first heater casing 2. The first tubular section 2b delivers air from the air inlet 106 to the heating chamber 6.

The aerosol-generating article 200 comprises an end plug 202, an aerosol-forming substrate 204, a hollow tube 206, a mouthpiece filter 208. Each of the above-mentioned components of the aerosol-generating article 100 is a substantially cylindrical element, wherein each of them has a substantially identical diameter. The components are arranged sequentially in an adjacent coaxial alignment and are surrounded by an outer paper wrapper 210 to form a cylindrical rod. The aerosol-forming substrate 204 is a tobacco rod or rod containing an assembled sheet of corrugated homogenized tobacco material surrounded by a wrapper (not shown). The corrugated sheet of homogenized tobacco material contains glycerin as an aerosol-forming substance. The end plug 202 and the filter 208 of the mouthpiece are made of acetyl cellulose fibers.

The distal end of the aerosol generating article 200 is inserted into the aerosol generating device 100 through the opening 104 in the housing 102 and is pushed into the aerosol generating device 100 until it rests against a stop (not shown in Fig. 6) located on the second heater casing 4, at which point it is completely inserted. The stop helps to properly position the aerosol generating substrate 204 inside the heating chamber 6, so that the heating chamber 6 can heat the aerosol generating substrate 204 to generate an aerosol.

The aerosol generating device 100 may further comprise: a sensor (not shown) for detecting the presence of the aerosol generating article 200; a user interface (not shown), such as a button for activating the heating element; and a display or indicator (not shown) for presenting information to the user, such as the remaining battery charge, heating status, and error messages.

In use, the user inserts the aerosol-generating article 200 into the aerosol-generating device 100, as shown in Fig. 6. The user then starts a heating cycle by activating the aerosol-generating device 100, such as by pressing a switch to turn on the device. In response to this, the control circuit 105 controls the supply of electric power from the power supply unit 103 to the heating element (not shown) to heat the heating element, which in turn heats the heating chamber 6. During the heating cycle, the heating element heats the heating chamber 6 to a predetermined temperature or a range of predetermined temperatures according to a temperature profile. The heating cycle can last approximately 6 minutes. The heat from the heating chamber 6 is transferred to the aerosol-forming substrate 204, which releases volatile compounds from the aerosol-forming substrate 204. The volatile compounds form an aerosol inside the aerosol generation chamber formed by the hollow tube 206. During the heating cycle, the user places the filter 208 of the mouthpiece of the aerosol generating article 200 between the lips of his mouth and puffs or inhales through the filter 208 of the mouthpiece. The generated aerosol is then drawn through the filter 102 of the mouthpiece into the user's mouth.

For the purpose of the present description and the appended claims, except where otherwise indicated, all numbers expressing quantities, amounts, percentages, etc., are to be understood as modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therebetween that may or may not be specifically recited herein. Therefore, in this context, the number A is to be understood as A ± 5 percent (5%) of A. In this context, the number A may be considered to include numerical values that are within the normal standard error for the measurement of the property that the number A modifies. The number A, in some instances, when used in the appended claims, may deviate by the percentages listed above, provided that the amount by which A deviates does not materially affect the essential and novel characteristic(s) of the claimed invention. Also, all ranges include the disclosed maximum and minimum points and include any intermediate ranges therebetween that may or may not be specifically listed herein.

Claims (32)

1. A heater assembly for an aerosol generating device comprising: a first heater housing comprising an air inlet; a second heater housing containing an aerosol outlet; a heating chamber for heating an aerosol-forming substrate, which is in fluid communication with the air inlet and the aerosol outlet to define an air flow path through the heater assembly; wherein the heating chamber is located between the first and second heater casings; the first and second heater casings are attached to each other by means of a fastening element configured to apply an axial force to the first and second heater casings to bring the axially opposite inner surfaces of the first and second heater casings into sealing engagement with the corresponding axially opposite end surfaces of the heating chamber to seal the air flow path. 2. The assembly according to claim 1, wherein at least one of the first and second heater housings comprises an internal cavity that encloses the heating chamber, wherein the length of the heating chamber is greater than the length of the internal cavity in the unassembled state of the heater assembly. 3. The unit according to item 2, in which the length of the heating chamber is from 0.5 to 8.5% greater than the length of the internal cavity. 4. An assembly according to any preceding claim, wherein the first and second heater housings are directly secured to each other by means of a fastener. 5. An assembly according to any preceding claim, wherein the axially opposite end surfaces of the heating chamber are in direct interaction with corresponding axially opposite inner surfaces of the first and second heater housings. 6. An assembly according to any preceding claim, wherein at least one of the first and second heater housings comprises a material having an elastic modulus of less than 6 gigapascals. 7. An assembly according to any preceding claim, wherein at least one of the first and second heater housings comprises a polymer. 8. An assembly according to any preceding claim, wherein at least one of the first and second heater housings comprises a bevel located on the inner surface of at least one of the first and second heater housings for aligning the heating chamber in the axial direction. 9. An assembly according to any preceding claim wherein the fastening element comprises a threaded fastener or a locking fastener. 10. An assembly according to any preceding claim, wherein the first and second heater housings are secured to each other by a plurality of fasteners. 11. The assembly of claim 10, wherein a plurality of fastening elements are symmetrically arranged around the outer perimeter of the first and second heater casings. 12. An assembly according to any preceding claim, wherein each of the first heater housing, the second heater housing and the heating chamber comprises an air flow passage, wherein the air flow passages communicate to form an air flow path. 13. An assembly according to any of the preceding claims, wherein the heating chamber comprises a tubular heating chamber. 14. The assembly of claim 13, wherein the diameter of the tubular heating chamber at each end of the tubular heating chamber is greater than the diameter of the tubular heating chamber in the region between the two ends of the tubular heating chamber. 15. An assembly according to any one of paragraphs 13, 14, in which each end of the tubular heating chamber is flared or funnel-shaped. 16. The assembly according to claim 15, wherein each end of the tubular heating chamber has a stepped or elbow profile. 17. An assembly according to any of the preceding claims, wherein the heating chamber is configured to accommodate at least a portion of the aerosol generating article. 18. An aerosol generating device comprising: a heater assembly according to any of the preceding paragraphs; and power supply for supplying electrical power to the heater unit. 19. A method for manufacturing a heater unit for an aerosol generating device, comprising: providing a first heater housing containing an air inlet; providing a second heater housing containing an outlet for the aerosol; providing a heating chamber for heating an aerosol-forming substrate and arranging the heating chamber to be in fluid communication with the air inlet and the air outlet to form an air flow path through the heater assembly; the location of the heating chamber between the first and second heater casings, fastening the first and second heater casings to each other using a fastening element, wherein the fastening element is configured to apply an axial force to the first and second heater casings to bring the axially opposite inner surfaces of the first and second heater casings into sealing engagement with the corresponding axially opposite end surfaces of the heating chamber to seal the air flow path. 20. The method of claim 19, further comprising applying an axial compressive force to the first and second heater housings prior to attaching the first and second heater housings to each other using a fastener.