HEATER ASSEMBLY WITH FASTENERS

Abstract

A heater assembly (1) for an aerosol generating device, the heater assembly comprising a first heater casing (2) including an air inlet, a second heater (4) casing including an aerosol outlet (10), and a heating chamber (6) for heating an aerosol-forming substrate, the heating chamber (6) being in fluid communication with both the air inlet and the aerosol outlet (10) to define an airflow path through the heater assembly (1), the heating chamber (6) being configured to include a first heater casing (2) and a second heater casing (4) including an aerosol outlet (10). The first heater casing (2) and the second heater casing (4) are disposed between the first heater casing (2) and the second heater casing (4), and the first heater casing (2) and the second heater casing (4) are attached to one another by fasteners (26), which are configured to apply an axial force to the first heater casing (2) and the second heater casing (4) to urge axially opposite inner surfaces of the first heater casing (2) and the second heater casing (4) into sealing engagement with respective axially opposite end faces of the heating chamber (6) to seal the airflow path.

Description

[Technical field]

[0001] The present disclosure relates to a heater assembly for an aerosol generating device. The present disclosure further relates to an aerosol generating device comprising the heater assembly. In particular, but not exclusively, the present disclosure relates to a handheld, electrically operated aerosol generating device for heating an aerosol-forming substrate to generate an aerosol and deliver the aerosol into a user's mouth. The present invention also relates to an aerosol generating system comprising an aerosol generating device and an aerosol-forming substrate. [Background technology]

[0002] Aerosol-generating devices that heat an aerosol-forming substrate to generate an aerosol without burning the aerosol-forming substrate are known in the art. The aerosol-forming substrate is typically provided in an aerosol-generating article together with other components such as a filter. The aerosol-generating article may have a rod shape for inserting the aerosol-generating article into the heating chamber of the aerosol-generating device. A heating element is typically disposed 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.

[0003] The heating chamber may be disposed within the housing of the aerosol generating device and form part of the airflow path through the aerosol generating device. To attempt to prevent the aerosol from escaping the airflow path and entering other parts of the aerosol generating device, which may damage the electronics of the device, it is known to provide a seal around the airflow path and between the heating chamber and the housing. The seal may be placed in direct contact with the heating chamber, and as a result is typically formed from a heat-resistant polymer such as silicone or polysiloxane. However, exposing such a polymer seal to the heating temperature of the heating chamber may generate undesirable by-products that may contaminate the aerosol. Furthermore, such heating temperatures may degrade the seal over time.

[0004] To heat the heating chamber, the aerosol generating device may include a flexible heating element disposed around the heating chamber. In order to allow direct contact between the seal and the heating chamber and reduce heating of the seal, attempts have been made to distance the seal from the heating element, for example at the downstream end of the heating chamber. However, this may require compromising the overall dimensions of the aerosol generating device, for example through the use of a long heating chamber, increasing the energy consumption of the heating chamber and reducing the efficiency of the aerosol generating device. Furthermore, increasing the length of the heating chamber may result in the heating chamber surrounding other components of the aerosol generating article, such as the filter, which may be indirectly heated via thermal conduction through the heating chamber. Undesirably, heating the filter wastes energy.

[0005] As an alternative to increasing the length of the heating chamber, the length of the heating element surrounding the heating chamber may be reduced. However, this may result in a portion of the aerosol-forming substrate not being covered or surrounded by the heating element, which may require heat to travel a longer 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 heating chamber wall. Thus, the portion of the aerosol-forming substrate not surrounded by the heating element may not be heated as effectively as the portion surrounded by the heating element. As a result, the portion of the aerosol-forming substrate not surrounded by the heating element may be cooler than the portion surrounded by the heating element, which may lead to premature condensation of the aerosol in the cooler portion. This may result in less aerosol being delivered to the user.

[0006] A further disadvantage of using a polymer seal between the heating chamber and the housing of the device is that the polymer seal provides a thermal conduction path for heat to be transferred away from the heating chamber to the material surrounding the heating chamber. This heat loss reduces the heat available to heat the aerosol-forming substrate and reduces the efficiency of the aerosol generating device.

[0007] It would be desirable to provide a heater assembly for an aerosol generating device that has improved sealing of its airflow path.It would be desirable to provide a heater assembly for an aerosol generating device that is more energy efficient and improves delivery of the aerosol to the user. Summary of the Invention

[0008] According to one embodiment of the present disclosure, a heater assembly for an aerosol generating device is provided. The heater assembly may include a first heater casing. The first heater casing may include an air inlet. The heater assembly may include a second heater casing. The second heater casing may include an aerosol outlet. The heater assembly may include 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 define an airflow path through the heater assembly. The heating chamber may be disposed between the first heater casing and the second heater casing. The first and second heater casings may be attached to one another by a fastener. The fastener may be configured to apply an axial force to the first and second heater casings. The fasteners may be configured to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path.

[0009] According to one embodiment of the present disclosure, there is provided a heater assembly for an aerosol generating device. The heater assembly comprises a first heater casing including an air inlet. The heater assembly comprises a second heater casing including an aerosol outlet. The heater assembly 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 define an airflow path through the heater assembly. The heating chamber is disposed between the first heater casing and the second heater casing. The first and second heater casings are attached to one another by a fastener configured to apply an axial force to the first and second heater casings to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path.

[0010] Advantageously, the above-described embodiments of the present disclosure do not require polymer seals because the airflow paths are sealed by direct engagement of the end faces of the heating chamber with the inner surfaces of the first and second heating cases, thus eliminating undesirable by-products that may be released by heating the polymer seal.

[0011] An additional advantage of sealing the airflow path using direct engagement of the end faces of the heating chamber with the inner surfaces of the first and second heating casings is that no space is required at the ends of the heating chamber to allow direct contact between the polymer seal and the heating chamber. For example, any space at one or more ends of the heating chamber to avoid direct contact between the heating element and the surrounding heater casing can be significantly reduced. This means that a shorter heating chamber can be used and a larger percentage of the length of the heating tube can be heated. This allows for more efficient heating of the aerosol-forming substrate.

[0012] Advantageously, the cross-sectional area available for heat conduction away from the heating chamber is greatly reduced. The heating chamber typically has a wall thickness less than the thickness of the polymer seal, e.g., 100 microns versus 2 millimeters, respectively. Thus, the area of ​​the end walls of the heating chamber in contact with the first and second heater casings is conventionally less than the area of ​​the polymer seal surrounding the heating chamber. As a result, the amount of heat loss to the portion of the aerosol generating device surrounding the heating chamber is reduced.

[0013] As used herein, the term "axial force" refers to a force acting 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.

[0014] The terms "distal," "upstream," "proximal," and "downstream" as used herein describe the relative locations of components or portions of components of aerosol-generating devices and aerosol-generating articles. Aerosol-generating articles and devices according to the present disclosure have a proximal end through which aerosol exits the aerosol-generating article or device for delivery to a user during use, and an opposite distal end. The proximal end of the aerosol-generating article and device may also be referred to as the oral end. During use, a user sucks on the proximal end of the aerosol-generating article to inhale the aerosol generated by the aerosol-generating article or device. The terms upstream and downstream are relative to the direction of travel of the aerosol through the aerosol-generating article or aerosol-generating device when a user sucks on the proximal end of the aerosol-generating article. The proximal end of the aerosol-generating article is downstream of the distal end of the aerosol-generating article. The proximal end of the aerosol-generating article may also be referred to as the downstream end of the aerosol-generating article, and the distal end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article.

[0015] The aerosol outlet may be an opening for receiving an aerosol-generating article. The aerosol may exit the opening through the aerosol-generating article received within the heating chamber.

[0016] At least one of the first and second heater casings may include an internal cavity. The internal cavity may surround a heating chamber. A length of the heating chamber may be greater than a length of the internal cavity. Advantageously, by making the length of the heating chamber greater than the length of the internal cavity, an elastic deformation is induced in at least one of the first and second heater casings. This elastic deformation is maintained by a fastener that applies an axial force to the first and second heater casings to provide a sealing engagement between the first and second heater casings and the heating chamber to seal the airflow path.

[0017] The first heater casing may include an internal cavity. The internal cavity may surround a heating chamber. The length of the heating chamber may be greater than the length of the internal cavity.

[0018] The second heater casing may include an internal cavity. The internal cavity may surround a heating chamber. The length of the heating chamber may be greater than the length of the internal cavity.

[0019] The first heater casing may include a first internal cavity. The second heater casing may include a second internal cavity. The first and second internal cavities may together enclose a heating chamber. The length of the heating chamber may be greater than the sum of the lengths of the first and second internal cavities.

[0020] The length of the heating chamber may be greater than the length of the interior cavity within the heater assembly in an unassembled state.

[0021] The length of the internal cavity may include a depth of a recess formed in an inner surface of the internal cavity of at least one of the first and second heater casings. The length of the internal cavity may include a depth of a recess formed in an inner surface of the internal cavity of each of the first and second heater casings.

[0022] Alternatively, the length of the internal cavity may include only the length of the internal cavity from a first end of the internal cavity to a second end of the internal cavity of one of the first and second heater casings.

[0023] The length of the heating chamber may be about 0.05 percent to about 8.5 percent longer than the internal cavity, preferably about 0.5 percent to about 5.0 percent longer than the internal cavity, and more preferably about 1.3 percent to about 3.1 percent longer than the internal cavity. These ranges have been found to be suitable for inducing elastic deformation of at least one of the first and second heater casings.

[0024] The length of the heating chamber may be from about 0.05 mm to about 1.0 mm longer than the internal cavity, and preferably from about 0.2 mm to about 0.4 mm longer than the internal cavity, which ranges have been found to be suitable for inducing elastic deformation of at least one of the first and second heater casings.

[0025] The first and second heater casings may enclose a heating chamber.

[0026] At least one of the first and second heater casings may comprise a material having a tensile modulus or Young's modulus of less than 6 gigapascals, preferably less than 5 gigapascals, more preferably less than 4 gigapascals. These values ​​of tensile modulus are typically less than the tensile modulus of the material of the heater chamber, meaning that at least one of the first and second heater casings elastically deforms preferentially than the heater chamber, since the heater chamber is made of a stiffer material than the first and second heater casings. These values ​​of tensile modulus have also been found to provide an appropriate amount of elastic deformation.

[0027] The heater chamber may include a material having a tensile modulus or Young's modulus of greater than about 100 gigapascals, preferably greater than about 150 gigapascals, more preferably greater than about 190 gigapascals. The heater chamber may include a material having a tensile modulus or Young's modulus of about 100 gigapascals to about 250 gigapascals, preferably about 150 gigapascals to about 220 gigapascals, more preferably about 190 gigapascals to about 205 gigapascals.

[0028] At least one of the first and second heater casings may include a material having a glass transition temperature greater than 130 degrees C. At least one of the first and second heater casings may include a material having a melting temperature greater than 280 degrees C. These properties help the material maintain its structural stability at the temperatures it experiences during heating and help reduce the likelihood of undesirable by-products being created.

[0029] At least one of the first and second heater casings may comprise a material having a Shore hardness of less than 90A as determined by technical standard ISO 868 Type A.

[0030] Preferably, at least one of the first and second heater casings may comprise a material that can be injection molded.

[0031] At least one of the first and second heater casings may comprise a polymer, which has been found to be a particularly suitable material due to its elastic properties.

[0032] The first and second heater casings may comprise any suitable material or combination of materials. Examples of suitable materials include plastics, or composites containing one or more materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), polyphenylsulfone (PPSU), and polyethylene. Preferably, at least one of the first and second heater casings comprises PEEK or PPSU.

[0033] At least one of the first and second heater casings may include a chamfer or beveled edge disposed on an inner surface of at least one of the first and second heater casings for axially aligning the heating chamber. Advantageously, the chamfer or beveled edge aids in accurately locating the heating chamber within the first and second heater casings.

[0034] The fasteners may include threaded fasteners or snap-fit ​​fasteners. These have been found to be suitable types of fasteners for attaching the first and second heater casings together. Snap-fit ​​fasteners or connectors have been found to have several additional advantages. For example, snap-fit ​​fasteners may help reduce the size of the heater assembly because they have a reduced profile compared to other types of fasteners. Snap-fit ​​fasteners may also help achieve a balanced alignment of the first and second heater casings because they apply a constant amount of axial force that cannot be varied. Additionally, snap-fit ​​fasteners help simplify manufacturing because only a single press-fit operation is required to attach the first and second heater casings. Additionally, snap-fit ​​fasteners may be integrally formed with the first and second heater casings to reduce the number of parts required for installation.

[0035] The heater assembly may include a plurality of fasteners. The first and second heater casings may be attached to one another by a plurality of fasteners. The plurality of fasteners may be symmetrically spaced around the circumference or outer surface of the first and second heater casings. This arrangement serves to apply a constant pressure between the end faces of the first and second heater casings that contact one another around the entire circumference of the first and second heater casings. As a result of this constant pressure, a constant sealing pressure is created between the contact surfaces of the heating chamber and the first and second heater casings around the entire circumference of the tubular heating chamber, improving the seal. The heater assembly may include at least two fasteners disposed diametrically opposite one another.

[0036] The first and second heater casings may be radially spaced from the heating chamber to define a hollow air space about the heating chamber. Advantageously, the hollow air space helps to insulate the heating chamber, which helps to reduce heat loss from the heating chamber and also helps to reduce heat transfer to the exterior of the heater assembly.

[0037] The first heater casing may have an airflow channel. The airflow channel of the first heater casing may be in fluid communication with the air inlet. The second heater casing may have an airflow channel. The airflow channel of the second heater casing may be in fluid communication with the aerosol outlet. The heating chamber may have an airflow channel. The airflow channel of the heating chamber may pass through the length of the heating chamber. The airflow channels of each of the first heater casing, the second heater casing, and the heating chamber may be in fluid communication with each other to define an airflow path through the heater assembly.

[0038] The heating chamber may include a tubular heating chamber. A diameter of the tubular heating chamber at a first end of the tubular heating chamber may be greater than a diameter along the length of the tubular heating chamber. A diameter of the tubular heating chamber at a second end of the tubular heating chamber may be greater than a diameter along the length of the tubular heating chamber. A diameter of the tubular heating chamber at each end of the tubular heating chamber may be greater than a diameter in a region between the two ends of the tubular heating chamber.

[0039] Advantageously, having a diameter at one or both ends of the tubular heating chamber 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 greater manufacturing tolerances of the heating chamber and of other components of the heater assembly. In particular, greater radial or lateral tolerances are allowed. As used herein, the terms "radial tolerance" or "lateral tolerance" are used to describe manufacturing tolerances in a direction substantially perpendicular to the major longitudinal axis or length of the heater assembly or aerosol generating device, for example, tolerances that result in components that are wider or narrower than their specified design width, or have a larger or smaller diameter than their specified design diameter. Radial or lateral tolerances are sometimes referred to as "horizontal tolerances".

[0040] Advantageously, by making the diameter of the ends of the tubular heating chamber larger than the rest of the tubular heating chamber, the inside diameter at one or both ends of the tubular heating chamber is larger than the inside diameter of the other components of the heater assembly with which the tubular heating chamber engages, i.e., the airflow paths in the first and second heater casings. This helps to avoid the end faces of the tubular heating chamber protruding or encroaching into the interior space of the airflow paths, which could damage the aerosol-generating article when it is received in the heating chamber via the airflow paths, resulting in a smaller end face of the tubular heating chamber to provide a sealing engagement with the other components. This arrangement also allows for larger radial or lateral tolerances in the other components, as described in more detail below.

[0041] 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 1 percent to 20 percent larger, 1 percent to 15 percent larger, 1 percent to 12 percent larger, or 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.

[0042] One or both ends of the tubular heating chamber may have an outer diameter of 7.5 mm to 9.0 mm, preferably 8.0 mm to 8.5 mm, more preferably about 8.4 mm. A portion of the tubular heating chamber between the two ends of the tubular heating chamber may have an outer diameter of 6.5 mm to 8.0 mm, preferably 7.0 mm to 8.0 mm, more preferably about 7.5 mm.

[0043] The inner diameter of the heating chamber may substantially correspond to or be substantially equal to the outer diameter of the aerosol-generating article. In some embodiments, the inner diameter of the heating chamber may be slightly smaller than the outer diameter of the aerosol-generating article such that the aerosol-generating article is compressed within the heating chamber. For example, the outer diameter of the aerosol-generating article may be about 7.4 millimeters and the inner diameter of the heating chamber may be about 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 within the aerosol-generating article.

[0044] At least one end portion of the tubular heating chamber may be flared or funnel shaped. Portions 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 between 0.5 percent and 10 percent of the total length of the tubular heating chamber, preferably between 1 percent and 5 percent of the total length of the tubular heating chamber, and more preferably about 3.3 percent of the total length of the tubular heating chamber.

[0045] The axial length of the flared or funnel-shaped end portion of the tubular heating chamber may be between 0.2 mm and 2 mm, preferably between 0.4 mm and 1 mm, more preferably about 0.5 mm. The flared or funnel-shaped end portion or portions of the tubular heating chamber may be disposed at an angle of 30 degrees to 60 degrees, 40 degrees to 50 degrees, or about 45 degrees relative to the longitudinal axis of the heating chamber or heater assembly. In some preferred embodiments, the flared or funnel-shaped end portion or portions of the tubular heating chamber may be disposed 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 heater assembly. Advantageously, providing the flared or funnel-shaped end portion or portions of the tubular heating chamber at an angle of less than 30 degrees relative to the longitudinal axis of the heating chamber or heater assembly may provide optimal stiffness for the flared or funnel-shaped end portion or portions of the tubular heating chamber in the direction of the longitudinal axis of the heating chamber or heater assembly.

[0046] At least one end or end portion of the tubular heating chamber may have a stepped profile or may be crimped. Portions of the tubular heating chamber at both ends of the tubular heating chamber may have a stepped profile or may be crimped. The axial length of the stepped or crimped end portion of the tubular heating chamber may be between 0.5 percent and 10 percent of the total length of the tubular heating chamber, preferably between 1 percent and 5 percent of the total length of the tubular heating chamber, more preferably about 3.7 percent of the total length of the tubular heating chamber. A radius is preferably provided between the stepped or crimped portions to avoid sharp edges and stress concentrations.

[0047] The axial length of the flared or funnel-shaped end portion of the tubular heating chamber may be between 0.2 mm and 2 mm, preferably between 0.4 mm and 1 mm, more preferably about 0.5 mm.

[0048] The tubular heating chamber may have a tubular wall thickness of between 0.05 millimeters and 1.00 millimeters, preferably between 0.05 millimeters and 0.50 millimeters, and more preferably about 0.10 millimeters.

[0049] The heating chamber may be made from any suitable material, including but not limited to ceramic or metal or metal alloy. An example of a suitable material is stainless steel.

[0050] The heater assembly may comprise at least one electric heating element for heating the aerosol-forming substrate. The heater assembly may comprise multiple electric heating elements. The electric heating element or elements may be disposed about or surround the outer surface of the heating chamber. The electric heating element or elements may be disposed about or surround the inner surface of the heating chamber. The electric heating element or elements may be part of or integral with the heating chamber.

[0051] The electric heating element or elements may include an electrically resistive material. Suitable electrically resistive materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composites made of ceramic and metallic materials. Such composites may include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steels, nickel-containing alloys, cobalt-containing alloys, chromium-containing alloys, aluminum-containing alloys, titanium-containing alloys, zirconium-containing alloys, hafnium-containing alloys, niobium-containing alloys, molybdenum-containing alloys, tantalum-containing alloys, tungsten-containing alloys, tin-containing alloys, gallium-containing alloys, manganese-containing alloys, gold-containing alloys, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal™, Kanthal™, and other iron-chromium-aluminum alloys, and iron-manganese-aluminum-based alloys. In composite materials, the electrically resistive material may be embedded in, encapsulated in, or coated with an insulating material, or vice versa, depending on the required energy transfer kinetics and external physicochemical properties.

[0052] One or more heating elements may be formed using a metal or metal alloy that has a well-defined relationship between temperature and resistivity. Heating elements formed in this manner may be used to both heat the heating element and to monitor the temperature of the heating element during operation.

[0053] The heating element may be disposed in or on a rigid carrier material or substrate. The heating element may be disposed in or on a flexible carrier material or substrate. The heating element may be formed as a track on a suitable insulating material such as ceramic or glass or polyimide film. The heating element may be sandwiched between two insulating materials.

[0054] The heater assembly may comprise a flexible heating element disposed around or surrounding the outer surface of the heating chamber. 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 have at least one end portion that is not covered or surrounded by the heating element. End portions may be provided at both ends of the heating chamber that are not covered or surrounded by the heating element. The end portion or portions may act as spacer portions to prevent direct contact between the heating element and other components of the heater assembly. The end portion or portions may each have a length of less than 2 millimeters, preferably less than 1 millimeter, preferably about 0.5 millimeters. Advantageously, the spacer portion may be cooler during heating than the portion of the heating chamber that is covered or surrounded by the heating element. The spacer portion may include a funnel-shaped end portion or a stepped end portion.

[0055] The heating chamber may be configured to receive at least a portion of the aerosol-generating article (as defined below).

[0056] According to an embodiment of the present disclosure, there is provided an aerosol generating device, which may comprise a heater assembly according to any of the heater assemblies described above, and which may comprise a power source or sources of electricity for providing power to the heater assembly.

[0057] According to an embodiment of the present disclosure, there is provided an aerosol generating device comprising a heater assembly according to any of the heater assemblies described above, and a power source or source for supplying power to the heater assembly.

[0058] The power source may be any suitable power source, such as, for example, a DC voltage source. In one embodiment, the power source is a lithium ion battery. Alternatively, the power source 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.

[0059] The aerosol generating device is preferably a handheld aerosol generating device that is comfortable for a user to hold between the fingers of one hand.

[0060] The aerosol generating device may further comprise a control circuit configured to control the supply of power to the heater assembly. The control circuit may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuit capable of providing control. The control circuit may comprise further electronic components. For example, in some embodiments, the control circuit may comprise any of a sensor element, a switch element, and a display element. Power may be continuously supplied to the heater assembly after activation of the device, or may be supplied intermittently (such as every puff). Power may be supplied to the heater assembly in the form of current pulses, for example by pulse width modulation (PWM).

[0061] The aerosol generating device may include a device housing. The device housing may house the heater assembly, a power source, and a control circuit. The housing may include an opening for receiving the aerosol-generating article. The opening may be connected to an aerosol outlet of a second heater casing of the heater assembly to allow the aerosol-generating article to be inserted into the heating chamber. The housing may include an air inlet. The air inlet may be connected to an air inlet of a first heater casing of the heater assembly.

[0062] The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and not brittle.

[0063] According to an embodiment of the present disclosure, there is provided an aerosol generation system comprising an aerosol generating device according to any of the above-described embodiments. The aerosol generation system may also comprise an aerosol-generating article including an aerosol-forming substrate.

[0064] According to an embodiment of the present disclosure, there is provided an aerosol-generating system comprising an aerosol-generating device according to any of the above-described embodiments and an aerosol-generating article including an aerosol-forming substrate.

[0065] As used herein, the term "aerosol-generating article" refers to an article that includes an aerosol-forming substrate that releases a volatile compound capable of forming an aerosol when heated in an aerosol-generating device. The aerosol-generating article is separate from the aerosol-generating device and is configured to be combined with the aerosol-generating device to heat the aerosol-generating article.

[0066] The aerosol-generating article may be substantially cylindrical in shape. The aerosol-generating article may be substantially elongated. The aerosol-forming substrate may be substantially cylindrical in shape. The aerosol-forming substrate may be substantially elongated.

[0067] The aerosol-generating article may have an overall 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. Further, the diameter of the aerosol-forming substrate may be about 5 mm to about 12 mm. The aerosol-generating article may comprise a filter plug. The filter plug may be located at the downstream end of the aerosol-generating article. The filter plug may be a cellulose acetate filter plug. In one embodiment, the filter plug is about 7 mm long, but may have a length of about 5 mm to about 12 mm.

[0068] In one embodiment, the aerosol-generating article may have an overall length of approximately 45 mm. The aerosol-generating article may have an outer diameter of approximately 7.3 mm, but may have an outer diameter of approximately 7.0 mm to approximately 7.4 mm. Furthermore, the aerosol-forming substrate may have a length of approximately 12 mm. Alternatively, the aerosol-forming substrate may have a length of approximately 16 mm. The aerosol-generating article may comprise an outer paper wrapper. Furthermore, the aerosol-generating article may comprise a separation between the aerosol-forming substrate and the filter plug. The separation may be approximately 21 mm or approximately 26 mm, but may be in the range of approximately 5 mm to approximately 28 mm. The separation may be provided by a hollow tube. The hollow tube may be made of cardboard or cellulose acetate.

[0069] 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 that contains volatile tobacco flavour 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 former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0070] When the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may comprise, for example, one or more of powder, granules, pellets, pieces, spaghetti, strips, or sheets containing one or more of herb leaves, tobacco leaves, tobacco vein fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. The solid aerosol-forming substrate may be in loose 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 that are released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules, for example containing additional tobacco or non-tobacco volatile flavor compounds, which may melt during heating of the solid aerosol-forming substrate.

[0071] As used herein, "homogenized tobacco" refers to a material formed by agglomerating particulate tobacco. The homogenized tobacco may be in the form of a sheet. The homogenized tobacco material may have an aerosol former content of greater than 5% on a dry weight basis. Alternatively, the homogenized tobacco material may have an aerosol former content of between 5% and 30% by weight on a dry weight basis. The homogenized tobacco material sheet may be formed by agglomerating particulate tobacco obtained by grinding or otherwise comminuted one or both of the tobacco blades and the tobacco stems. Alternatively, or additionally, the homogenized tobacco material sheet may include one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed, for example, during tobacco processing, handling, and shipping. The homogenized tobacco material sheet may include one or more inherent binders (i.e., tobacco intrinsic binders), one or more extrinsic binders (i.e., tobacco extrinsic binders), or combinations thereof to aid in the cohesion of the particulate tobacco, although alternatively or additionally, the homogenized tobacco material sheet may include other additives including, but not limited to, tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavorants, fillers, aqueous and non-aqueous solvents, and combinations thereof.

[0072] In a particularly preferred embodiment, the aerosol-forming substrate comprises an assembly of crimped sheets of homogenized tobacco material. As used herein, the term "crimped sheet" refers to a sheet having a plurality of substantially parallel ridges or corrugations. When the aerosol-generating article is assembled, the substantially parallel ridges or corrugations preferably run along or parallel to the longitudinal axis of the aerosol-generating article. This advantageously facilitates assembling the crimped sheets of homogenized tobacco material to form the aerosol-forming substrate. However, it will be appreciated that a crimped sheet of homogenized tobacco material for inclusion in an aerosol-generating article may alternatively or additionally have a plurality of substantially parallel ridges or corrugations that are disposed at an acute or obtuse angle relative 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 assembly of sheets of homogenized tobacco material that are substantially evenly textured across substantially its entire surface. For example, the aerosol-forming substrate may comprise an assemblage of a crimped sheet of homogenized tobacco material that includes a plurality of substantially parallel ridges or corrugations that are substantially evenly spaced across the width of the sheet.

[0073] Optionally, the solid aerosol-forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may take the form of a powder, granules, pellets, pieces, spaghetti, strips, or sheets. Alternatively, the carrier may be a tubular carrier having a thin layer of solid substrate deposited on its inner surface, or on its outer surface, or on both its inner and outer surfaces. Such a tubular carrier may be formed, for example, of paper or paper-like material, non-woven carbon fiber mat, low-mass open mesh metal screen, or perforated metal foil, or any other thermally stable polymeric matrix.

[0074] The solid aerosol-forming substrate may be deposited on the surface of the carrier in the form of, for example, a sheet, foam, gel, or slurry. The solid aerosol-forming substrate may be deposited over the entire surface of the carrier or, alternatively, in a pattern to provide a non-uniform flavour delivery during use.

[0075] Although reference has been made above to solid aerosol-forming substrates, it will be clear to the skilled person that other forms of aerosol-forming substrates may be used in other embodiments. For example, the aerosol-forming substrate may be a liquid aerosol-forming substrate. When a liquid aerosol-forming substrate is provided, the aerosol-generating device preferably comprises a means for holding the liquid. For example, the liquid aerosol-forming substrate may be held in a container or liquid storage portion. Alternatively, or additionally, the liquid aerosol-forming substrate may be absorbed into a porous carrier material. The porous carrier material may be made of any suitable absorbent plug or body, for example foamed metal or plastic materials, polypropylene, terylene, nylon fibers, or ceramics. The liquid aerosol-forming substrate may be held in the porous carrier material before 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 before use. For example, the liquid aerosol-forming substrate may be provided in a capsule. The shell of the capsule preferably melts upon heating and releases the liquid aerosol-forming substrate into the porous carrier material. Capsules may optionally contain a solid in combination with a liquid.

[0076] Alternatively, the carrier may be a nonwoven fiber or fiber bundle having tobacco components incorporated therein. The nonwoven fiber or fiber bundle may comprise, for example, carbon fiber, natural cellulose fiber, or cellulose derivative fiber.

[0077] According to an embodiment of the present disclosure, a method of manufacturing a heater assembly for an aerosol generating device is provided. The method may include providing a first heater casing including an air inlet. The method may include providing a second heater casing including an aerosol outlet. The method may include providing a heating chamber for heating an aerosol-forming substrate. The method may include disposing the heating chamber in fluid communication with both the air inlet and the air outlet to define an airflow path through the heater assembly. The method may include disposing the heating chamber between the first heater casing and the second heater casing. The method may include attaching the first and second heater casings to one another using a fastener. The fastener may be configured to apply an axial force to the first and second heater casings to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path.

[0078] According to an embodiment of the present disclosure, there is provided a method of manufacturing a heater assembly for an aerosol generating device, the method including providing a first heater casing including an air inlet, providing a second heater casing including an aerosol outlet, providing a heating chamber for heating an aerosol-forming substrate, disposing the heating chamber in fluid communication with both the air inlet and the air outlet to define an airflow path through the heater assembly, disposing the heating chamber between the first heater casing and the second heater casing, and attaching the first and second heater casings to one another using fasteners, the fasteners being configured to apply an axial force to the first and second heater casings to urge opposing inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path.

[0079] The method may further include applying an axial compressive force to the first and second heater casings prior to attaching the first and second heater casings to one another using the fasteners. The compressive force may be between 100 Newtons and 300 Newtons, and preferably the compressive force is about 200 Newtons.

[0080] The heating chamber may be press-fit into a recess formed in the inner surface of the first heater casing.

[0081] The heating chamber may be press-fit into a recess formed in the inner surface of the second heater casing.

[0082] Features described with respect to one of the above embodiments may equally be applied to other embodiments of the present disclosure.

[0083] The invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein. EXAMPLES

[0084] Example 1: A heater assembly for an aerosol generating device, the heater assembly comprising: a first heater casing including an air inlet; a second heater casing including an aerosol outlet; and a heating chamber for heating an aerosol-forming substrate, the heating chamber being in fluid communication with both the air inlet and the aerosol outlet to define an airflow path through the heater assembly. Example 2: 2. The heater assembly according to example 1, wherein the heating chamber is disposed between the first heater casing and the second heater casing. Example 3: A heater assembly according to example 1 or 2, wherein the first and second heater casings are attached to one another by a fastener, the fastener being configured to apply an axial force to the first and second heater casings to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path. Example 4: A heater assembly according to any of Examples 1-3, wherein at least one of the first and second heater casings includes an internal cavity surrounding a heating chamber, and the length of the heating chamber is greater than the length of the internal cavity in the heater assembly in an unassembled state. Example 5: The heater assembly according to example 4, wherein the length of the heating chamber is between about 0.5 percent and about 8.5 percent longer than the inner cavity. Example 6: The heater assembly according to example 5, wherein the length of the heating chamber is between about 1.0 percent and about 5.0 percent longer than the inner cavity. Example 7: The heater assembly according to example 6, wherein the length of the heating chamber is about 1.3 percent to about 3.1 percent longer than the inner cavity. Example 8: A heater assembly according to any of Examples 1-7, wherein at least one of the first and second heater casings comprises a material having a tensile modulus of less than 6 gigapascals. Example 9: The heater assembly according to example 8, wherein at least one of the first and second heater casings comprises a material having a tensile modulus of less than 5 gigapascals. Example 10: The heater assembly according to example 9, wherein at least one of the first and second heater casings comprises a material having a tensile modulus of less than 4 gigapascals. Example 11: The heater assembly according to any of Examples 1-10, wherein at least one of the first and second heater casings comprises a polymer. Example 12: A heater assembly according to any of Examples 1-11, wherein at least one of the first and second heater casings includes a chamfer disposed on an inner surface of at least one of the first and second heater casings for axially aligning the heating chamber. Example 13: The heater assembly according to any of Examples 1-12, wherein the fastener comprises a threaded fastener. Example 14: The heater assembly according to any of Examples 1-12, wherein the fasteners comprise snap-fit ​​fasteners. Example 15: The heater assembly according to any of Examples 1-14, wherein the heater assembly includes a plurality of fasteners. Example 16: The heater assembly according to example 15, wherein the plurality of fasteners are symmetrically spaced around the circumference of the first and second heater casings. Example 17: The heater assembly according to any of Examples 1-16, wherein the first heater casing, the second heater casing, and the heating chamber each include an airflow channel, the airflow channels communicating to define an airflow path. Example 18: The heater assembly according to any of Examples 1-17, wherein the heating chamber comprises a tubular heating chamber. Example 19: The heater assembly according to example 18, 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 a region between the two ends of the tubular heating chamber. Example 20: The heater assembly according to example 18 or 19, wherein each end of the tubular heating chamber is flared or funnel shaped. Example 21: 21. The heater assembly according to example 20, wherein the axial length of the flared or funnel-shaped end of the tubular heating chamber is between 0.5 percent and 10 percent of the overall length of the tubular heating chamber. Example 22: A heater assembly according to example 18 or 19, wherein each end of the tubular heating chamber has a stepped or hemmed profile. Example 23: 23. The heater assembly of embodiment 22, wherein the axial length of the stepped or beveled end of the tubular heating chamber is between 0.5 percent and 10 percent of the overall length of the tubular heating chamber. Example 24: An aerosol generating device comprising a heater assembly according to any one of Examples 1 to 23, and a power source for supplying power to the heater assembly. Example 25: 1. A method of manufacturing a heater assembly for an aerosol generating device, the method comprising: providing a first heater casing including an air inlet; providing a second heater casing including an aerosol outlet; disposing a heating chamber to heat an aerosol-forming substrate and in fluid communication with both the air inlet and the air outlet to define an airflow path through the heater assembly; disposing the heating chamber between the first heater casing and the second heater casing; and attaching the first and second heater casings to one another using fasteners, the fasteners being configured to apply an axial force to the first and second heater casings to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chambers to seal the airflow path. Example 26: The method according to example 25, further comprising applying an axial compressive force to the first and second heater casings prior to attaching the first and second heater casings to one another using the fasteners.

[0085] The embodiments will now be further described with reference to the figures. [Brief description of the drawings]

[0086] [Figure 1] FIG. 1 is a longitudinal cross-section of a heater assembly according to an embodiment of the present disclosure. [Diagram 2] Figure 2A is a schematic longitudinal cross-sectional view of the heater assembly of Figure 1 in an unassembled state with the heating chamber located outside the heater casing, and Figure 2B is a schematic longitudinal cross-sectional view of the heater assembly of Figure 1 immediately prior to assembly with the heating chamber located inside the heater casing. [Figure 3A-3B] Figure 3A is a longitudinal cross-section of a heater assembly according to another embodiment of the present disclosure, and Figure 3B is an enlarged view of a portion of the heater assembly contained within the box labeled D in Figure 3A. [Figure 4A-4B] 4A and 4B are side views of two exemplary heating chambers for use in a heater assembly according to the present disclosure. [Figure 5A-5C] 5A-5C are schematic cross-sectional partial views of a known tubular heating chamber illustrating problems that can arise due to manufacturing tolerances as a result of press-fitting the heating chamber into the heater casing. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the interior of an aerosol generating device and an aerosol-generating article received within the aerosol generating device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0087] Referring to Figure 1, Figure 1 shows a longitudinal cross section of a heater assembly 1 comprising a first heater casing 2, a second heater casing 4 and a heating chamber 6 for heating an aerosol-forming substrate. The first heater casing 2 comprises a substantially flat support section 2a and a first tubular section 2b. The support section 2a of the first heater casing 2 has an inner surface 2c facing the second heater casing 4. An air inlet (not shown) is disposed at a distal end of the first tubular section 2b, which extends distally away from the support section 2a in a direction parallel to the longitudinal axis XX of the heater assembly 1.

[0088] The second heater casing 4 includes a hollow shell section 4a and a second tubular section 4b. The hollow shell section 4a has an internal cavity 4c surrounding the heating chamber 6 and is open at its distal end to allow the heating chamber to be received within the internal cavity 4c. The internal cavity 4c of the hollow shell section 4a is closed at its distal end by the inner surface 2c of the support section 2a of the first heater casing 2. An aerosol outlet 10 is disposed at the proximal end of the second tubular section 4b, which extends proximally away from the hollow shell section 4a in a direction parallel to the longitudinal axis XX of the heater assembly 1. The aerosol outlet 10 is defined by an opening 12 configured to receive an aerosol-generating article (not shown). The aerosol exits the opening 10 via the aerosol-generating article received within the heating chamber 6.

[0089] The heating chamber 6 includes a tubular heating chamber made from stainless steel tubing. A heating element 8 is disposed around the outer surface of the heating chamber to heat the heating chamber 6, which in turn heats an aerosol-forming substrate (not shown) received within the interior space of the tubular heating chamber 6. The heating element includes a heat-resistant flexible polyimide film having electrical resistive heating tracks (not shown) formed in a serpentine pattern on the film. The resistive heating tracks are connected to a power supply (not shown) and generate heat when an electric current is passed through the resistive heating tracks. The heating element is disposed around substantially the entire length of the tubular heating chamber 6, and heats substantially the entire length of the tubular heating chamber 6.

[0090] The heating chamber 6 is supported on the support section 2a of the first heater casing 2. The distal or first end 6a of the heating chamber 6 is press-fitted into a first recess 14 formed in the inner surface 2c of the first heater casing 2. The inner peripheral edge of the recess 14 has a bevel or chamfer 16 for locating the heating chamber 6 within the recess 14 and for precisely aligning the heating chamber 6 with respect to the longitudinal axis XX of the heater assembly 1. The proximal or second end 6b of the heating chamber 6 is press-fitted into a second recess 18 formed in the inner surface of the inner cavity 4c of the second heater casing 4. The inner peripheral edge of the recess 18 has a bevel or chamfer 20 for locating the heating chamber 6 within the recess 18 and for precisely aligning the heating chamber 6 with respect to the longitudinal axis XX of the heater assembly 1. The second recess 18 is disposed axially opposite the first recess 14 in a direction parallel to the longitudinal axis XX of the heater assembly 1.

[0091] The first heater casing 2 and the second heater casing 4 are attached to each other to enclose the heating chamber 6. The distal end of the second heater casing 4 has two bosses or connection blocks 22 disposed diametrically opposite each other on the outer surface of the second heater casing 4. Each boss 22 has a hole 24 for receiving a screw 26. Two bosses or connection blocks 28 are disposed at the proximal end of the first heater casing 2 in positions corresponding to the boxes 22. Each of the bosses 28 has a hole 30 for receiving a screw 26. To attach the first heater casing 2 and the second heater casing 4, the proximal end of the first heater casing 2 is engaged with the distal end of the second heater casing 4, and the screw 26 is inserted through the holes 24 and 30 to hold the first heater casing 2 and the second heater casing 4 in engagement. Thus, the screw 26 acts as a fastener that holds the first heater casing 2 and the second heater casing 4 in engagement with each other.

[0092] The sidewall of the internal cavity 4c of the second heater casing 4 is radially spaced from the heating chamber 6 to define a hollow air space 13 around the heating chamber 6. The hollow air space 13 helps to insulate the heating chamber 6, which helps to reduce heat loss from the heating chamber 6 and also helps to reduce heat transfer to the exterior of the heater assembly 1 and the aerosol generating device.

[0093] The first heater casing 2 and the second heater casing 4 are made from polyetheretherketone (PEEK) due to its advantageous insulating and mechanical properties. PEEK has a lower thermal conductivity than the stainless steel tubular heating chamber 6, which helps reduce heat transfer or loss through the first heater casing 2 and the second heater casing 4. It also helps to keep the outer surface of the heater assembly 1 cooler than the outer surface of the heating chamber 6. It also helps to retain heat within the heating chamber to improve aerosol generation.

[0094] Another advantage of PEEK is that it has a lower tensile modulus or Young's modulus than stainless steel. The tensile modulus of PEEK is typically in the range of about 3.7 gigapascals to about 3.95 gigapascals, and the tensile modulus of stainless steel is typically in the range of 190 gigapascals 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 heater casing 2 and the second heater casing 4 will elastically deform preferentially over the heating chamber 6 because the heating chamber is stiffer than the first heater casing 2 and the second heater casing 4. Such preferential elastic deformation has been found to be highly advantageous for the heater assemblies of the present disclosure, as discussed in more detail below.

[0095] The tubular heating chamber 6 is disposed between the first heater casing 2 and the second heater casing 4. The tubular heating chamber 6 has a length that is slightly longer (0.5 to 8.5 percent longer) than the length of the internal cavity 4c of the second heater casing 4 (including the depth of the second recess 16 of the second heater casing 4 and the depth of the first recess 14 of the first heater casing 2). The difference in length between the heating chamber 6 and the internal cavity 4c is not visible in the assembled heater assembly as shown in FIG. 1, but the difference in length is shown and discussed in more detail below with respect to FIGS. 2A and 2B. When the first heater casing 2 and the second heater casing 4 are attached to each other around the heating chamber 6, the slightly longer and stiffer heating chamber 6 allows the first heater casing 2 and the second heater casing 4 to elastically deform when their respective ends are engaged. The first heater casing 2 and the second heater casing 4 are maintained in their elastically deformed state by screws 26 that hold the first heater casing 2 and the second heater casing 4 in engagement with each other. The screws 26 apply an axial force (indicated by arrow A in FIG. 1 ) to the first heater casing 2 and the second heater casing 4 in a direction parallel to the longitudinal axis XX of the heater assembly 1. The axial force urges the inner surfaces of the first recess 14 and the second recess 16 into sealing engagement with the end faces of the respective first end 6a and second end 6b of the heating chamber 6. The sealing engagement is the result of a compressive force (indicated by arrow B in FIG. 1 ) that develops at the interface between the heating chamber 6 and the first heater casing 2 and the second heater casing 4 due to the axial force applied by the screws 26. Localized plastic deformation of the first heater casing 2 and the second heater casing 4 occurs at the interface between the heating chamber 6 and the first heater casing 2 and the second heater casing 4 (i.e., in the area between arrows B in FIG. 1 ), helping to achieve a seal.

[0096] As mentioned above, the threads 26 are disposed diametrically opposite each other on the respective bosses 22, 28 on the outer surfaces of the first heater casing 2 and the second heater casing 4. The symmetrical arrangement of the threads with respect to the longitudinal axis XX of the heater assembly 1 serves to apply a constant pressure between the end faces of the first heater casing 2 and the second heater casing 4 that are in contact with each other around the entire circumference of the first heater casing 2 and the second heater casing 4. As a result of this constant pressure, a constant sealing pressure is created between the heating chamber 6 and the first heater casing 2 and the second heater casing 4 around the entire circumference of the tubular heating chamber 6.

[0097] The tubular heating chamber 6 has an airflow channel 32 defined by an interior space of the tubular heating chamber 6, the airflow channel 32 extending axially along the length of the heating chamber 6 in a direction parallel to the longitudinal axis XX of the heater assembly 1. Additionally, the first tubular section 2b of the first heater casing 2 has an airflow channel 34, and the second tubular section 4b of the second heater casing 4 has an airflow channel 36. The airflow channels 34, 32 and 36 of the first tubular section 2b, the tubular heating chamber 6 and the second tubular section 4b, respectively, are in fluid communication with each other to define an airflow path 38 through the heater assembly 1 between the air inlet (not shown) and the aerosol outlet 10. Thus, the heating chamber 6 is in fluid communication with both the air inlet and the aerosol outlet 10.

[0098] The heating chamber 6 is axially aligned with the first tubular section 2b and the second tubular section 4b of the first heater casing 2 and the second heater casing 4, respectively. Thus, the axial force applied by the screw 26 (indicated by arrow A in FIG. 1 ) urges the heating chamber 6 and the first heater casing 2 and the second heater casing 4 into sealing engagement with each other to seal the airflow path 38 and reduce the possibility of aerosol escaping from the airflow path 38 at the intersection between the heating chamber 6 and the first heater casing 2 and the second heater casing 4. Such sealing engagement is achieved as a result of elastic deformation of the first heater casing 2 and the second heater casing 4 without the use of polymer seals. Thus, such an arrangement helps reduce the possibility of undesirable by-products being released.

[0099] The first heater casing 2 has a stop or step 39 formed on the inner surface of the first tubular section 2b within its airflow channel 34. The stop 39 is arranged to engage a distal end of an 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 an aerosol-forming substrate provided within the aerosol-generating article within the heating chamber 6.

[0100] FIG. 2A shows a schematic longitudinal cross-sectional view of the heater assembly 1 of FIG. 1 in an unassembled state. For clarity, the tubular heating chamber 6 is shown outside the first heater casing 2 and the second heater casing 4. The first heater casing 2 and the second heater casing 4 are shown with the distal end 4d of the second heater casing abutting the proximal end 2d of the first heater casing 2, but without elastic deformation of the first heater casing 2 and the second heater casing 4. The longitudinal length l of the tubular heating chamber 6 is shown in FIG. h is the difference in length l d The axial length of the internal cavity 4c is l c In this embodiment, the length l of the internal cavity 4c is cincludes the depth of the recesses 14 and 18 formed in the first heater casing 2 and the second heater casing 4 and is measured from the upper or proximal flat inner surface of the recess 18 of the second heater casing 4 to the lower or distal flat inner surface of the recess 14 of the first heater casing 2. The inner surfaces of the recesses 14 and 18 form the inner surfaces of the first heater casing 2 and the second heater casing 4, respectively.

[0101] Of course, in some embodiments, the heater assembly may not use a recess to locate the heating chamber 6, but may rely solely on the axial force applied by the screw 26 shown in FIG. 1 to hold the heating chamber in place. In such an arrangement, the length l of the internal cavity c is simply the length of the internal cavity 4c of the second heater casing 4, i.e., the axial length from the distal end 4d of the second heater casing to the inner surface of the upper or proximal end wall 4e of the second heater casing.

[0102] 2B is a schematic longitudinal cross-sectional view of the heater assembly 1 of FIG. 1 immediately prior to assembly. The heating chamber 6 is located within the inner cavity 4c of the second heater casing and is axially located between the first heater casing 2 and the second heater casing 4. The difference in length between the tubular heating chamber 6 and the inner cavity 4c is l d Due to this, the distal end 4d of the second heater casing 4 is spaced apart from the heater casing 4 by a distance l d 2d of the first heater casing 2.

[0103] To assemble the heater assembly 1, a compressive force of approximately 200 Newtons (indicated by arrow C in FIG. 2B ) is applied to the heater assembly 1. The compressive force C urges the distal end 4d of the second heater casing into engagement with the proximal end 2d of the first heater casing 2, closing the space or gap between the first heater casing 2 and the second heater casing 4. The longer, stiffer heating chamber 6 causes the first heater casing 2 and the second heater casing 4 to elastically deform as described above. The screws 26 are then inserted into the holes 24, 30 formed in the bosses 22, 28 and a compressive force C is applied and tightened to hold the first heater casing 2 and the second heater casing 4 in engagement. The compressive force C is then removed. After the compressive force C is removed, the screws 26 maintain the elastic deformation of the first heater casing 2 and the second heater casing 4. As a result, the screws 26 apply an axial force to the first heater casing 2 and the second heater casing 4, as described above, holding the first heater casing 2 and the second heater casing 4 in sealing engagement with the tubular heating chamber 6.

[0104] It should be noted that Figures 2A and 2B are schematic and not to scale: for clarity, the figures have been simplified by omitting some details and the sizes of features have been altered or exaggerated.

[0105] Figure 3A is a longitudinal cross-section of a heater assembly 1 according to another embodiment of the present disclosure. The structure of the heater assembly 1 of Figure 3A is identical to that of Figure 1, except that the first heater casing 2 and the second heater casing 4 are attached to each other using a snap-fit ​​connector 40 instead of the screws 26 and bosses 22, 28 of the arrangement of Figure 1.

[0106] Similar to the screw 26 shown in FIG. 1, the snap-fit ​​connector 40 supports the first heater casing 2 and the second heater casing 4 in their elastically deformed condition and holds the first heater casing 2 and the second heater casing 4 in engagement with one another. The snap-fit ​​connector 40 applies an axial force to the first heater casing 2 and the second heater casing 4 in a direction parallel to the longitudinal axis XX of the heater assembly 1. The axial force resists elastic deformation of the first heater casing 2 and the second heater casing 4 that would otherwise cause the first heater casing 2 and the second heater casing 4 to disengage. The axial force urges the inner surfaces of the first recess 14 and the second recess 16 and the end faces of the first end 6a and the second end 6b of the heating chamber 6, respectively, into sealing engagement, thereby sealing the airflow path 38. The sealing engagement is the result of a compressive force (indicated by arrow B in FIG. 3A ) that develops at the interface between the heating chamber 6 and the first and second heater casings 2 and 4 due to the axial force applied by the snap-fit ​​connectors 40. Localized plastic deformation of the first and second heater casings 2 and 4 occurs at the interface between the heating chamber 6 and the first and second heater casings 2 and 4 (i.e., in the region between arrows B in FIG. 3A ) and helps achieve the seal.

[0107] 1, the snap-fit ​​connectors 40 are disposed diametrically opposite one another on the outer surfaces of the first heater casing 2 and the second heater casing 4. The symmetrical arrangement of the snap-fit ​​connectors relative to the longitudinal axis XX of the heater assembly 1 serves to apply a constant pressure between the end faces of the first heater casing 2 and the second heater casing 4 that are in contact with one another around the entire circumference of the first heater casing 2 and the second heater casing 4. As a result of this constant pressure, a constant sealing pressure is created between the heating chamber 6 and the first heater casing 2 and the second heater casing 4 around the entire circumference of the tubular heating chamber 6.

[0108] 3B is an enlarged view of one of the snap-fit ​​connectors 40 of the heater assembly 1 contained within the box labeled D in FIG. 3A. The snap-fit ​​connector 40 includes a cantilever 42 and a ratchet 44. The ratchet 44 is disposed at a proximal end of the cantilever 42. The cantilever 44 and the ratchet 44 are integrally formed with the first heater casing 2 at a proximal edge of the first heater casing 2. The snap-fit ​​connector 40 further includes a slot 46 formed in an inner surface of the second heater casing 4 near a distal end of the second heater casing 4. The slot 46 is configured to receive the ratchet 44. The ratchet 44 has a beveled leading edge, and the cantilever 42 can elastically deform to allow the ratchet to pass into an internal cavity of the second heater casing 4 and into the slot 46. The ratchet 44 has a squared rear edge that prevents the ratchet 44 from being removed from the slot 46 after the ratchet 44 is received therein.

[0109] As can be seen in Figure 3A, the snap-fit ​​connectors 40 reduce the size of the heater assembly 1 by eliminating the need for the screw and boss arrangement of Figure 1. The snap-fit ​​connectors also help achieve balanced alignment of the heater assembly components since each applies the same amount of axial force. Additionally, the snap-fit ​​connectors help simplify manufacturing by only requiring a single press-fit operation to attach the first heater casing 2 and the second heater casing 4, reducing the number of parts required for installation.

[0110] 4A and 4B are side views of two exemplary heating chambers for use in a heater assembly according to the present disclosure. Referring to FIG. 4A, FIG. 4A shows a first embodiment of a heating chamber 6A. The heating chamber 6A comprises a stainless steel tube having a circular cross section. A hollow interior space within the tubular heating chamber 6A has an inner diameter substantially corresponding to an outer diameter of an aerosol-generating article (not shown) such that the tubular heating chamber 6A can receive the aerosol-generating article within the interior space. A portion 7a of the heating chamber 6A at each end of the heating chamber 6A is flared outwardly to form a funnel shape at each end of the heating chamber 6A. The flared portions 7a each have a length l1, and the percentage of the total length l of the heating chamber 6A constituted by each of the flared portion lengths l1 may be in the range of 1 to 5 percent. The flared end portions 7a of the heating chamber 6A each form an angle of about 45 degrees with the longitudinal axis of the heating chamber 6A. As a result of the flared end portions 7a, the outer diameter D at the two ends of the heating chamber 6A is greater than the outer diameter d of the heating chamber 6A between the two flared end portions 7a.

[0111] A portion 9a of the heating chamber 6A between the two flared end portions 7a has straight sides parallel to the longitudinal axis of the heating chamber 6A. The straight portion 9a of the heating chamber 6A has a length l2 that substantially corresponds to the length of an aerosol-forming substrate provided in an aerosol-generating article configured to be received in the heating chamber 6A. Substantially all of the length l2 of the straight portion 9a of the heating chamber 6A is surrounded by a flexible heating element (not shown, but described above in connection with FIG. 1). The flared portion 7a of the heating chamber 6A is not surrounded by the heating element and acts as a spacer between the ends of the heating element and the components that hold the heating chamber 6A, i.e., the first and second heater casings, and helps to prevent direct contact between these components and the heating element.

[0112] Referring to FIG. 4B, FIG. 4B shows a second embodiment of the heating chamber 6B. The heating chamber 6B has essentially the same structure as the heating chamber 6A of FIG. 4A, except that instead of flared end portions, the heating chamber 6B has stepped or beveled end portions 7b. That is, a portion 7b of the heating chamber 6B at each end of the heating chamber 6B is stepped or beveled radially outward to form a step at each end of the heating chamber 6B. The stepped portions 7b each have a length l1, and the proportion of the total length l of the heating chamber 6B constituted by each of the stepped portion lengths l1 may be in the range of 1 to 5 percent. As a result of the stepped end portions 7b, the outer diameter D at the two ends of the heating chamber 6B is greater than the outer diameter d of the heating chamber 6B between the two stepped end portions 7b.

[0113] A portion 9b of the heating chamber 6B between the two stepped end portions 7b has straight sides parallel to the longitudinal axis of the heating chamber 6B. The straight portion 9b of the heating chamber 6B has a length l2 that corresponds substantially to the length of an aerosol-forming substrate provided in an aerosol-generating article configured to be received in the heating chamber 6B. Substantially all of the length l2 of the straight portion 9b of the heating chamber 6B is surrounded by a flexible heating element (not shown, but described above in connection with FIG. 1). The stepped portion 7b of the heating chamber 6B is not surrounded by the heating element and acts as a spacer between the ends of the heating element and the components that hold the heating chamber 6B, i.e., the first and second heater casings, and helps prevent direct contact between these components and the heating element. The heating chamber 6B also includes a transition portion 11 between each of the stepped portions 7b and the straight portion 9b, providing an inclined or curved transition between the outer diameter D of each of the stepped portions and the outer diameter d of the straight portion.

[0114] 5A-5C are schematic cross-sectional views of a portion of a known tubular heating chamber having a straight tubular wall, illustrating problems that can arise due to manufacturing tolerances during press fitting of such a heating chamber with a heater casing. Manufacturing tolerances can cause component dimensions to be larger or smaller than specified design lengths, leading to connection problems for tightly mated components. Very precise manufacturing tolerances are more difficult to achieve with rapid manufacturing techniques such as injection molding.

[0115] Referring to FIG. 5A, FIG. 5A shows the upper part of a known or conventional tubular heating chamber 6 press-fitted into a recess 16 of the upper heater casing 4. The entire length of the tubular heating chamber 6 is straight, i.e., has a constant outer diameter along its entire length, and the tubular heating chamber 6 does not have a flared or stepped end portion as the tubular heating chambers 6A and 6B of FIGS. 4A and 4B. As seen in FIG. 5A, the inner diameter d1 of the heating chamber 6 is smaller than the inner diameter d2 of the opening 15 of the heater casing 4 through which the aerosol-generating article passes during insertion of the aerosol-generating article into the heating chamber 6. As a result, a portion of the thickness t of each of the walls, i.e., the end face of the heating chamber 6, protrudes into the interior space defined by the inner diameter d2 of the opening 15. This forms a sharp step 17 in the opening 15, which may damage the aerosol-generating article when it is inserted through the opening 15, or may prevent the aerosol-generating article from being inserted. A similar situation may arise if the width w of the recess 16 is smaller than the wall thickness t of the tubular heating chamber 6. In this case, there is not enough space in the recess 16 to receive the end of the tubular heating chamber 6, and as a result, the end protrudes into the interior space defined by the inner diameter d2 of the opening 15.

[0116] Of course, a similar situation to that shown in Figure 5A may occur at the lower or upstream end of the tubular heating chamber 6. The sharp step at the upstream end of the heating chamber may suffer from problems with debris or deposits building up in the gap formed by the step, which may be difficult to remove or clean using a cleaning tool.

[0117] Figure 5B shows the lower part of a known or conventional tubular heating chamber 6 press-fitted into the recess 14 of the lower heater casing 2. As in Figure 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 heater casing 2, through which a portion of the aerosol-generating article protrudes when the aerosol-generating article is properly positioned within the heating chamber 6. As a result of a sharp step 21 formed in the opening 19, the aerosol-generating article may be damaged as it passes through the opening 19, or may be prevented from being fully inserted.

[0118] Of course, a similar situation to that shown in Figure 5B may occur at the upper or downstream end of the tubular heating chamber 6. The sharp step at the downstream end of the heating chamber may suffer from problems with debris or deposits building up in the gap formed by the step, which may be difficult to remove or clean using a cleaning tool.

[0119] Figure 5C shows the upper part of a known or conventional tubular heating chamber 6 being press-fitted into a recess 16 in the upper heater casing 4. As in Figures 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 insertion into the heating chamber 6. As a result, the tubular heating chamber 6 simply passes through the opening 15, and therefore a press-fit is not possible in this situation.

[0120] Figure 5D is a schematic cross-sectional view of the top of the tubular heating chamber 6A of Figure 4A. As mentioned above, the tubular heating chamber 6A has a wall with a funnel-shaped or flared end portion 7a. The flared end portion 7a is press-fitted into a 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 Figure 5D). The outer diameter D of the flared end portion 7a is also larger than the inner diameter d7 of the opening 15 of the heater casing 4, through which the aerosol-generating article passes during 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 d7 of the opening 15, even when taking into account the radial or lateral manufacturing tolerances of the inner diameter d7.

[0121] The arrangement of FIG. 5D significantly reduces the possibility that a portion of the end surface 6c of the wall of the tubular heating chamber 6A will protrude into the diameter d7 and the cross-section of the airflow path defined by the diameter d7 in FIG. 5D. Additionally, the end surface 6c of the wall of the tubular heating chamber 6A is angled away from the cross-section of the airflow path defined by the diameter d7, further reducing the possibility that a portion of the end surface 6c of the wall of the tubular heating chamber 6A will protrude into the airflow path. The arrangement of FIG. 5D, and in particular the use of the tubular heating chamber 6A having a flared or funnel-shaped end portion 7a, is suitable for rapid manufacturing techniques, as it allows the use of components with larger radial or lateral tolerances. The arrangement of FIG. 5D also significantly reduces the risk of damage to the aerosol-generating article when it is inserted into the heating chamber 6A.

[0122] It will be appreciated that the tubular heating chamber 6B of Figure 4B may also be used in the arrangement of Figure 5D in place of heating chamber 6A to achieve the same benefits. The larger outer diameter D of the stepped end portion 7b of heating chamber 6B reduces the likelihood that a portion of the end face of the wall of tubular heating chamber 6B will protrude into diameter d7 of Figure 5D and into the airflow path. Heating chamber 6B also allows for the use of components with larger radial or lateral tolerances, reducing the risk of damage to the aerosol-generating article when it is inserted into heating chamber 6B.

[0123] It should be noted that Figures 5A-5D are schematic and not to scale: for clarity, the figures have been simplified by omitting some details and the sizes of features have been altered or exaggerated.

[0124] Figure 6 is a schematic cross-sectional view of an aerosol generating device 100 and an aerosol generating article 200 received within the aerosol generating device 100. Together, the aerosol generating device 100 and the aerosol generating article 200 form an aerosol generating system. In Figure 6, the aerosol generating device 100 is shown in a simplified manner. In particular, the elements of the aerosol generating device 100 are not drawn to scale. Furthermore, elements that are not relevant for understanding the aerosol generating device 100 have been omitted.

[0125] The aerosol generating device 100 comprises a housing 102 that may house the heater assembly 1 of either FIG. 1 or 3A, a power source 103, and a control circuit 105. In FIG. 6, a first heater casing 2, a heating chamber 6, and a second heater casing 4 are shown. As described above in connection with FIG. 1, the heating chamber 6 has a flexible heating element (not shown) disposed therearound for heating the heating chamber 6. The power source 103 is a battery, which in this embodiment is a rechargeable lithium ion battery. The control circuit 105 is connected to both the power source 103 and the heating element and controls the supply of electrical energy from the power source 103 to the heating element to regulate the temperature of the heating element.

[0126] The housing 102 includes an opening 104 at a proximal or mouth end of the aerosol generating device 100, through which the aerosol-generating article 200 is received. The opening 104 is connected to the opening 12 of the heater assembly 1 of FIG. 1, through which the aerosol exits the heater assembly 1. However, it will be appreciated that the aerosol exits the aerosol generating device 100 mostly through the heater assembly 1 and the aerosol-generating article 200. The housing 102 further includes an air inlet 106 at a distal end of the aerosol generating device 100. The air inlet 106 is connected to an air inlet disposed at the distal 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.

[0127] The aerosol-generating article 200 comprises an end plug 202, an aerosol-forming substrate 204, a hollow tube 206, and a mouthpiece filter 208. Each of the above-mentioned components of the aerosol-generating article 100 are substantially cylindrical elements, each having substantially the same diameter. The components are arranged consecutively in coaxial alignment and abutting contact and surrounded by an outer paper wrapper 210 to form a cylindrical rod. The aerosol-forming substrate 204 is a tobacco rod or plug comprising an assembly of crimped sheets of homogenized tobacco material surrounded by a wrapper (not shown). The crimped sheets of homogenized tobacco material contain glycerin as an aerosol former. The end plug 202 and the mouthpiece filter 208 are formed from cellulose acetate fibers.

[0128] 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 pushed into the aerosol-generating device 100 until it engages a stop (not shown in FIG. 6 ) disposed on the second heater casing 4, up to which point the aerosol-generating article 200 is fully inserted. The stop serves to precisely position the aerosol-forming substrate 204 within the heating chamber 6 so that the heating chamber 6 can heat the aerosol-forming substrate 204 to form an aerosol.

[0129] The aerosol generating device 100 may further include 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, for example, remaining battery power, heating status, and error messages.

[0130] In use, a user inserts the aerosol-generating article 200 into the aerosol-generating device 100 as shown in FIG. 6. The user then initiates a heating cycle by activating the aerosol-generating device 100, for example, by pressing a switch to turn the device on. In response, the control circuitry 105 controls the supply of power from the power source 103 to a 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 to a predetermined temperature range according to a temperature profile. The heating cycle may last for approximately six minutes. 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 in the aerosolization chamber formed by the hollow tube 206. During the heating cycle, the user places the mouthpiece filter 208 of the aerosol-generating article 200 between their lips and smokes or inhales the mouthpiece filter 208. The generated aerosol is drawn through the mouthpiece filter 102 and into the user's mouth.

[0131] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like, should be understood in all instances as modified by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A ± five percent (5%) A. Within this context, the number A may be considered to include values ​​that are within the typical standard error for the measurement of the property that the number A modifies. The number A may, in some cases, as used in the appended claims, deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel properties of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. 1. A heater assembly for an aerosol generating device, the heater assembly comprising: a first heater casing including an air inlet; a second heater casing including an aerosol outlet; a heating chamber for heating an aerosol-forming substrate, said heating chamber being in fluid communication with both the air inlet and the aerosol outlet to define an airflow path through said heater assembly; the heating chamber is disposed between the first heater casing and the second heater casing; a heater assembly, wherein the first and second heater casings are attached to one another by fasteners, the fasteners being configured to apply an axial force to the first and second heater casings to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path.

2. 2. The heater assembly of claim 1, wherein at least one of the first and second heater casings includes an internal cavity surrounding the heating chamber, the length of the heating chamber being greater than a length of the internal cavity in the heater assembly in an unassembled state.

3. The heater assembly of claim 2 , wherein the length of the heating chamber is between 0.5 percent and 8.5 percent longer than the interior cavity.

4. The heater assembly of any of claims 1 to 3, wherein the first and second heater casings are directly attached to one another by fasteners.

5. A heater assembly as described in any one of claims 1 to 3, wherein the axially opposite end faces of the heating chamber directly engage with axially opposite end faces of each of the first and second heater casings.

6. The heater assembly of any of claims 1 to 3, wherein at least one of the first and second heater casings comprises a material having a tensile modulus of elasticity of less than 6 gigapascals.

7. The heater assembly of any of claims 1 to 3, wherein at least one of the first and second heater casings comprises a polymer.

8. 4. The heater assembly of claim 1, wherein at least one of the first and second heater casings includes a chamfer disposed on an inner surface of the at least one of the first and second heater casings for axially aligning the heating chamber.

9. The heater assembly of any of claims 1 to 3, wherein the fasteners comprise threaded fasteners or snap-fit ​​fasteners.

10. The heater assembly of any of claims 1 to 3, wherein the first and second heater casings are attached to one another by a plurality of fasteners.

11. The heater assembly of claim 10 , wherein said plurality of fasteners are symmetrically spaced about a circumference of said first and second heater casings.

12. A heater assembly as described in any one of claims 1 to 3, wherein the first heater casing, the second heater casing, and the heating chamber each include an airflow channel, the airflow channels communicating to define the airflow path.

13. The heater assembly of any of claims 1 to 3, wherein the heating chamber comprises a tubular heating chamber.

14. 14. The heater assembly of claim 13, wherein a diameter of the tubular heating chamber at each end of the tubular heating chamber is greater than a diameter of the tubular heating chamber in a region between the two ends of the tubular heating chamber.

15. The heater assembly of claim 13 , wherein each end of the tubular heating chamber is flared or funnel shaped.

16. The heater assembly of claim 13 , wherein each end of the tubular heating chamber has a stepped or hemmed profile.

17. The heater assembly of any of claims 1 to 3, wherein the heating chamber is configured to receive at least a portion of an aerosol-generating article.

18. An aerosol generating device, comprising: A heater assembly according to any one of claims 1 to 3; a power supply for supplying power to the heater assembly.

19. 1. A method of manufacturing a heater assembly for an aerosol generating device, the method comprising: providing a first heater casing including an air inlet; providing a second heater casing including an aerosol outlet; providing a heating chamber for heating an aerosol-forming substrate, said heating chamber being disposed in fluid communication with both said air inlet and said air outlet to define an airflow path through said heater assembly; disposing the heating chamber between the first heater casing and the second heater casing; and attaching the first and second heater casings to one another using the fasteners, the fasteners being configured to apply an axial force to the first and second heater casings to urge axially opposed inner surfaces of the first and second heater casings into sealing engagement with respective axially opposed end faces of the heating chamber to seal the airflow path.

20. 20. The method of claim 19, further comprising applying an axial compressive force to the first and second heater casings prior to attaching the first and second heater casings to one another using the fasteners.

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