EP4225079A1

EP4225079A1 - Aerosol generating device

Info

Publication number: EP4225079A1
Application number: EP21790842.5A
Authority: EP
Inventors: Alec WRIGHT; Andrew Robert John ROGAN
Original assignee: JT International SA
Current assignee: JT International SA
Priority date: 2020-10-08
Filing date: 2021-10-08
Publication date: 2023-08-16
Also published as: WO2022074220A1; JP2023544691A

Abstract

An aerosol generating device (100) is described. The aerosol generating device (100) includes a heating chamber (110) arranged to receive an aerosol substrate (121), the heating chamber (110) operable to heat the aerosol substrate (121) to generate an aerosol; a compressing element (130) configured to change shape above a threshold temperature; such that the compressing element (130) extends into the heating chamber (110) during a heating operation of the aerosol generating device (100). In this way, an improved thermal contact with the aerosol substrate (121) is achieved and maintained even where shrinkage of the aerosol substrate (121) occurs during heating.

Description

Aerosol Generating Device

The present invention relates to an aerosol generating device. The disclosure is particularly applicable to a portable aerosol generation device, which may be self-contained and low temperature. Such devices may heat, rather than bum, tobacco or other suitable aerosol substrate materials by conduction, convection, and/or radiation, to generate an aerosol for inhalation.

The popularity and use of reduced-risk or modified-risk devices (also known as vaporisers) has grown rapidly in the past few years as an aid to assist habitual smokers wishing to quit using traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm aerosolisable substances as opposed to burning tobacco in conventional tobacco products.

A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn (HNB) device. Devices of this type generate an aerosol or vapour by heating an aerosol substrate (i.e. consumable) that typically comprises moist leaf tobacco or other suitable aerosolisable material to a temperature typically in the range 150°C to 300°C. Heating an aerosol substrate, but not combusting or burning it, releases an aerosol that comprises the components sought by the user but not the toxic and carcinogenic by-products of combustion and burning. In addition, the aerosol produced by heating the tobacco or other aerosolisable material does not typically comprise the burnt or bitter taste that may result from combustion that can be unpleasant for the user.

However, within such devices, the aerosol substrate is known to lose structural integrity during the heating process and may shrink and/or begin to release aerosolisable material. This may result in inconsistent heating of the aerosol substrate and adversely affect the aerosol generating properties of the device. Furthermore, if a user removes the aerosol substrate from the device during the heating operation, there is a risk of the user contacting a hot portion of the aerosol substrate.

Therefore, an object of the present invention is to address one or more of these issues.

SUMMARY

According to an aspect of the present invention, there is provided an aerosol generating device, comprising: a heating chamber arranged to receive an aerosol substrate, the heating chamber operable to heat the aerosol substrate to generate an aerosol; a compressing element configured to change shape above a threshold temperature; such that the compressing element extends into the heating chamber during a heating operation of the aerosol generating device.

In this way, as the aerosol substrate is heated during a heating operation the compressing elements extend into the heating chamber to contact the aerosol substrate. This improves the heat transfer to the aerosol substrate for more uniform and efficient heating. It further restricts removal of the aerosol substrate during a heating operation to reduce the risk of the aerosol substrate being inadvertently removed, where the elevated temperature of the aerosol substrate could pose a safety risk. A further advantage is that it compensates for shrinkage of the aerosol substrate during heating, common to many substrate materials such as tobacco, to ensure that heat is effectively transferred to the aerosol substrate throughout the heating process.

The phrase “extends into the heating chamber” is intended to encompass examples where the compressing element is outside of the internal volume of the heating chamber below the threshold temperature and extends into the heating chamber above the threshold temperature. It also encompasses examples in which the compressing element is positioned at an outer edge within the heating chamber, i.e. an extremity of the internal volume of the heating chamber, and extends further into the internal volume of the heating chamber above the threshold temperature. In all examples the compressing element is preferably configured such that it allows an aerosol substrate to be inserted and removed below the threshold temperature and moves above the threshold temperature to press against the aerosol substrate when received in the heating chamber.

Preferably the compressing element is configured to change shape above a threshold temperature such that the compressing element extends radially inward into the heating chamber. In this way, the compressing element acts so as to contact an outer side surface of the aerosol substrate, providing a gripping action on the side surface of the aerosol substrate. In this way the aerosol substrate is more effectively secured in the heating chamber and improved heat conduction to the aerosol substrate is provided.

The one or more compressing elements are preferably positioned at an inner side of the heating chamber and extend away from the inner side of the heating chamber towards the centre of the heating chamber (i.e. in a radially inward direction). The radial direction is defined as a direction perpendicular to a side wall of the heating chamber, directed towards the centre of heating chamber, for example in a direction perpendicular to an elongate axis of the heating chamber.

The radial direction may equally be defined as a direction perpendicular to an insertion direction of the aerosol substrate. The radial direction distinguishes from extending in a longitudinal or axial direction, to compress an end of the aerosol substrate, which would not secure the aerosol substrate in the chamber.

In some example, the heating chamber may be tubular and the radial direction being a direction from the inner surface of the heating chamber towards the longitudinal axis of the heating chamber.

Preferably a plurality of compressing elements are provided, each positioned at an inner side wall of the heating chamber (they may form part of the heating chamber side wall or be separate components within the heating chamber positioned at a radial extremity) and each configured to extend inwardly to compress the aerosol generating substrate. In this way, an aerosol substrate is gripped around its circumference to further secure the aerosol substrate in the heating chamber while being heated, and improve the uniform application of heat around the aerosol substrate.

Preferably the heating chamber comprises an opening and is arranged to receive the aerosol substrate into the heating chamber through the opening in a longitudinal direction; and wherein the compressing element is positioned at an inner surface of the heating chamber and configured to change shape above the threshold temperature to extend into the heating chamber in a direction perpendicular to the longitudinal direction. The radial direction may therefore be defined as a direction perpendicular to the longitudinal direction towards the centre of the heating chamber. By compressing an aerosol substrate in a direction perpendicular to the insertion direction, the aerosol substrate is better secured in the heating chamber during use, with improved heat transfer to the aerosol substrate, while allowing the aerosol substrate to be easily inserted and removed when the compressing elements are subtracted.

Preferably the heating chamber is tubular and arranged to receive a tubular aerosol substrate, wherein the compressing element is configured to extend into the heating chamber in a direction perpendicular to the elongate axis of the tubular aerosol substrate. In this way, the side edges of the aerosol substrate are compressed during extension of the compressing element, improving the grip of the compressing element on the aerosol substrate to secure it in the chamber.

Preferably the compressing element is configured to change shape during a heating operation of the aerosol generating device to contact an aerosol substrate received within the heating chamber. That is, the compressing element moves above the threshold temperature to constrict the internal dimensions of the heating chamber. Preferably, the compressing element is configured to be moved such that a compressive force is provided to the aerosol substrate during the heating operation of the aerosol generating device. Preferably the compressing element is configured to change shape due to heating by the heating chamber during a heating operation of the aerosol generating device. In this way, the compressing element does not require a separate activation mechanism but changes shape automatically during heating of the aerosol substrate. This reduces the complexity of the control circuitry required.

It is known that, if the compressive force is too large, voids may be removed from within the aerosol substrate which are otherwise required for aerosol production and to provide a pressure drop. Conversely, if the compressive force is too small, there may be poor contact between the second heating element and aerosol substrate resulting in an inefficient transfer of heat. Hence, the compressing element is preferably configured to provide a controlled compression against the aerosol substrate during the heating operation.

In some examples, the compressing element is positioned within the heating chamber; wherein the compressing element: lies along an inner wall of the heating chamber below the threshold temperature to allow an aerosol substrate to be inserted and removed from the chamber; and extends away from the inner wall into the heating chamber above the threshold temperature. This facilitates insertion of the aerosol substrate in the heating chamber when the chamber is below the threshold temperature while improving the heat transfer by reducing the size of the chamber and so compressing of the substrate when the chamber is heated. It also permits a reduced size of the heating chamber as much as possible. This improve over prior art devices in which the chamber is partially occupied by the comprising element and so its volume must be sized accordingly.

In other examples, the compressing element forms part of a wall of the heating chamber and extends into the heating chamber to reduce the inner volume of the heating chamber above the threshold temperature. Other examples may combine both compressing elements that form part of the wall of the heating chamber and separate compressing elements positioned within the heating chamber. These examples also provide the above described advantages in terms of facilitating insertion of the aerosol substrate, while increasing the usable size of the chamber into which a larger aerosol substrate can therefore be inserted.

In some examples of the invention one or more compressing elements may comprise a heating element. For example the compressing element may be configured to provide resistive heating upon application of an electrical current. For examples the compressing element may comprise a resistive heating material such as stainless steel, titanium, nickel, and/or Nichrome. The aerosol generating device may comprise electrical contacts to which the one or more compressing elements are connected such that an electrical current may be applied through the compressing element.

In some examples of the invention, one or more compressing elements may comprise a heat conductive material and the aerosol generating device further comprises a heater arranged to transfer heat to the compressing element. For example, an external heater may be applied to an outer surface of the heating chamber such that heat is conducted through the heating chamber and/or compressing elements to heat the aerosol substrate. Preferably the heater is a thin film heater wrapped around an outer surface of the heating chamber. These examples ensure more uniform heating and less complexity to fabricate the heater. In particular, the heating functions and the deforming functions are handled by two specific elements so that it opens more flexibility to select optimum heating technology and it allows more flexibility to select the optimum deformable material (e.g. SMA) for the compressing element. This would not be the case where the penetrating element is also the heating element thereby limiting the choice of heating technologies and materials.

Preferably the aerosol generating device comprises a plurality of compressing element arranged around a circumference of the heating chamber. In this way the aerosol substate is compressed around its circumference, ensuring improved thermal contact which is especially effective when applying an external heating of the substrate Preferably the compressing elements are arranged periodically at regular intervals around the circumference of the heating chamber. In this way, the aerosol substrate is gripped uniformly around its circumference and uniform heating is provided. Alternatively the compressing elements may extend fully around the circumference, further improving the uniformity of heat transfer.

The compressing elements may provide point contacts against the aerosol substrate. In other examples the compressing elements comprise longitudinal strips running along a length of the heating chamber and spaced around the circumference of the heating chamber. The longitudinal strips may be configured to bend inwardly into the heating chamber (i.e. radially inwardly toward the centre of the heating chamber) above the threshold temperature. These examples of the invention ensure air flow between the compressing elements or strips to improve air circulation around the substrate as well as providing convection heating.

The ends of the longitudinal strips may be fixed such that a longitudinal centre point along the longitudinal strips bends outwardly into the heating chamber. In other examples the longitudinal strips may have a width between a first longitudinal edge and a second longitudinal edge, where the first and second longitudinal edges are fixed and a central longitudinal portion of the total width bends outwardly into the internal volume of the heating chamber.

In some examples the compressing elements may comprise at least partially annular elements extending around at least a part of the circumference of the heating chamber and spaced along the length of the heating chamber, the annular element configured to contract above the threshold temperature. In particular the elements are annular elements configured to radially contract above the threshold temperature. These examples provide improved gripping of the aerosol substrate and improved thermal conduction since the substrate is contacted fully around its circumference, thereby also enhancing the uniformity of heating. In some examples the compressing element comprise annular elements extending around the majority or preferably the entirety of the circumference of the heating chamber. In other examples the compressing element may comprise a continuous spiral which contacts above the threshold temperature. For examples the compressing element may spiral around an inner surface of the heating chamber.

One or more compressing element may comprise a shape memory alloy, for example one or more of Ni-Ti, Cu-AI-Ni, Cu-Zn-AI. The threshold temperature may correspond to the martensitic transformation temperature of the shape memory alloy. One or more compressing elements may comprise a bimetallic element.

Preferably the compressing element is configured to change shape to 3extend into the heating chamber above a first threshold temperature and the compressing element is configured to return to its original shape when the temperature of the heating chamber drops below a second threshold temperature, thereby retracting from the heating chamber to allow an aerosol substrate to be inserted into or removed from the chamber. The second threshold temperature may be equal to the first threshold temperature.

The aerosol generating device may further comprise an aerosol substrate, wherein the aerosol substrate comprises a material which shrinks when heated; wherein the compressing element is arranged such that contact is maintained between the compressing element and the aerosol substrate during a heating operation of the aerosol generating device. The aerosol substrate may comprise tobacco.

Preferably, the aerosol substrate is a rod of aerosol substrate having a first end for insertion into the aerosol generating device and an opposing second end to be received in a mouth of a user, and wherein the compressing element is configured to be moved such that a compressive force is applied adjacent the first end of the rod of aerosol substrate, thereby preventing aerosol substrate from being released out the first end. Preferably, the compressive force is applied adjacent the first end of the rod of aerosol substrate across between 1/6th and 1/4th of a length of the rod of aerosol substrate. More preferably, the compressive force is applied adjacent the first end of the rod of aerosol substrate across 1/6th of a length of the rod of aerosol substrate. In this way, the compressing element is positioned to only provide compression to the region of aerosol substrate where compression is most desired, i.e. at the end of the rod of aerosol substrate where there is a risk of aerosol substrate falling out. Moreover, as the compressing element is positioned to contact a region of the rod of aerosol substrate opposite to the mouth end of the rod of aerosol substrate, energy is not wasted heating non-aerosol generating material, e.g. non-tobacco material (NTM).

In a second aspect of the invention there is provided a heating arrangement for an aerosol generating device, the heating arrangement comprising a heating chamber arranged to receive an aerosol substrate, the heating chamber operable to heat the aerosol substrate to generate an aerosol; a compressing element configured to change shape above a threshold temperature; such that the compressing element extends into the heating chamber during a heating operation of the aerosol generating device. The components of the second aspect may comprise any of the features of the first aspect defined above. The heating arrangement may be configured to be implemented within an aerosol generating device.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention are now described, by way of example, with reference to the drawings, in which:

Figure 1A and 1 B show a schematic cross-sectional view of an aerosol generating device in an embodiment of the invention with the compressing element below and above the threshold temperature respectively; Figure 2A, 2B and 2C show schematic cross-sectional views of a heating chamber of an aerosol generating device in an embodiment of the invention;

Figure 3A, 3B and 3C show schematic cross-sectional views of a heating chamber of an aerosol generating device in an embodiment of the invention;

Figure 4A and 4B show schematic cross-sectional views of a heating chamber of an aerosol generating device in an embodiment of the invention; and

Figure 5A and 5B show schematic cross-sectional views of a heating chamber of an aerosol generating device in an embodiment of the invention;

DETAILED DESCRIPTION

Figures 1A and 1 B schematically illustrate an aerosol generating device 100 according to the present invention. The aerosol generating device 100 comprises a heating chamber 110 arranged to receive a consumable 120 comprising an aerosol substrate 121. The heating chamber 110 is operable to heat the aerosol substrate 121 to generate an aerosol (also referred to interchangeably as a vapour) for inhalation by a user. The device 100 further includes a compressing element 130 which is configured to change shape above a threshold temperature such that the compressing element 130 extends into the heating chamber 110 during a heating operation of the aerosol generating device 100.

Figure 1A illustrates the aerosol generating device 100 when the compressing element 130 is below the threshold temperature and Figure 1 B illustrates the device 100 during heating operation when the compressing element has exceeded the threshold temperature such that it extends into the heating chamber to compress the aerosol substrate 121 of a consumable 120 received in chamber 110. This way, the compressing element contacts a consumable 120 received in the chamber 110 during heating so as to provide improved heat transfer from the heating chamber 110 to the aerosol substrate 121. The compressing elements 130 are preferably configured to move with respect to the heating chamber 110. Each compressing element is preferably moveable in a direction perpendicular to the surface of the aerosol substrate 121 (e.g. perpendicular to the length of the rod of aerosol substrate 121) to alter the level of contact between the compressing element and the aerosol substrate 121. In particular, the compressing element 130 may grip the consumable 120 so as to provide an efficient thermal conduction to the aerosol substrate 121 and further restrain the consumable within the device 100 during use. The invention solves the problem described above related to shrinking of aerosol substrates, such as tobacco, during heating as the compressing element moves to reduce the internal dimensions of the chamber and grips the consumable 120 to compensate for any reduction in volume of the aerosol substrate 121 due to the heating operation.

The aerosol generating device 100 may comprise a housing 101 comprising a heating chamber opening 111 at a first end 102 of the housing 101. The aerosol generating device 100 further comprises a battery 140 and control electronics 141 for selectively transferring power from the battery 140 to a heater of the heating chamber 110. In this embodiment the heating chamber 110 is substantially tubular and arranged to receive a tubular consumable 120 comprising an aerosol substrate 121 extending over a portion of the total length of the consumable 120. The aerosol substrate 121 is positioned towards one end of the tubular body of the consumable 120 with a mouthpiece 122 positioned at the opposite end. In alternative embodiments, the heating chamber 110 may not be tubular. For example, the heating chamber 110 may be formed as a cuboidal, conical, hemi-spherical or other shaped cavity, and be configured to receive a complementary shaped consumable 120.

As shown in Figures 1A and 1 B consumable 120 is longer than the heating chamber 110 such that the mouthpiece 122 extends out of the heating chamber opening 111 such that a user can inhale the vapour generated by the heating of the aerosol substrate 121 through the mouthpiece 122. The aerosol generating device 100 may be a heat or bum device configured to selectively controllably provide heating of the aerosol substrate 121 so as to release an aerosol from the substrate without burning the aerosol substrate 121 .

The compressing elements 130 may be provided in a number of different ways but generally share the common feature that they comprise a material which changes shape under heating so as to contact the aerosol substrate 121. The compressing elements 130 preferably require no control electronics but instead simply comprise a material which has suitable properties such that it deforms above a threshold temperature in a known controllable way such that it can be configured to contact the consumable and aerosol substrate 121 to achieve the effects described above. In this way, the aerosol generating device 100 does not require either an additional actuation mechanism or a temperature sensor, simplifying the structure and improving ease of manufacturing while also reducing the size and energy consumption of the device 100.

The one or more compressing elements 130 preferably comprise a shape memory alloy configured to deform above a threshold temperature. For example, the compressing elements 130 may comprise Ni-Ti, Cu-AI-Ni, Cu-Zn- Al. The shape memory alloy exhibits the shape memory effect such that it deforms (i.e. undergoes a phase transformation) as a function of temperature to move into the internal volume of the heating chamber 110. In particular, the compressing element 130 may be configured to deform at a first threshold temperature during the heating operation of the aerosol generating device 100, where the first threshold temperature may correspond to the martensitic transformation temperature of the shape memory alloy. Moreover, the compressing element 130 may be further configured to continue to deform (i.e. actuate) above the first threshold temperature such that the compressing element 130 is moved further in the direction (i.e. towards) the aerosol substrate 121 as the temperature increases. As the aerosol substrate 121 is prone to shrinking during heating, this mode of operation ensures that contact is maintained with the aerosol substrate 121 during the heating operation and/or ensures a compressive (e.g. constant compressive force) is provided to the aerosol substrate 121 during the heating operation. The compressing elements 130 may also be configured to deform (i.e. actuate) at a second threshold temperature during the cooling operation of the aerosol generating device, such that the compressing element 130 is moved out of contact with the aerosol substrate 121. Preferably, the compressing element 130 comprises a two-way shape memory alloy, but in other examples, the compressing element 130 may comprise a one-way shape memory alloy.

Transformation temperatures of conventional shape memory alloys (SMAs) are up to 100°C and therefore suitable for use in a heat or bum aerosol generating device where the heating temperature is typically in the range 150°C to 300°C such that the temperature applied during a heating operation is sufficient to cause the shape memory alloy to transform to apply the compressing force to a consumable 120.

The compressing elements could also be provided by bimetallic materials which deform under heating due to the difference in properties of the two metals. As shown in Figure 1A, below the threshold temperature the compressing elements 130 lie along the outer edges of the heating chamber 110 so that the internal volume of the heating chamber 110 is not restricted and the consumable 120 can be inserted and removed. When a user operates the device to apply current to the heater of the heating chamber 110 in order to heat the consumable, as the temperature increases above the threshold temperature of the compressing elements, the compressing elements 130 move into the clamping position shown in Figure 1 B in which a mechanical stress applied to the consumable 120 to improve the thermal transfer, secure the consumable 120 in the device and compensate for any shrinkage of the aerosol substrate 121. The compressing elements 130 return to the retracted position shown in Figure 1A when the temperature drops back below the threshold temperature. The consumable 120 can then be removed from the device such that the compressing elements 130 also act as a safety feature to prevent the user from removing the consumable when it is too hot.

As will be described below, the heating chamber 110 may comprise an external heating element applied to the outside of the heating chamber 110 such that heat is transferred to the consumable 120 through the conductive shell of the heating chamber 110 and through the compressing elements 130. In other examples, the compressing elements 130 themselves may comprise the heating element such that during use the heating element is moved into direct contact with the aerosol substrate 121. During heating, as shown in Figure 1 B, the compressing elements move to compress the consumable while the remainder of the tubular heating chamber 110 stays stationary. The compressing elements 130 may contact the aerosol substrate 121 along 1/4 to 5/6, preferably around 3/4 of the length of the aerosol substrate 121 .

Figures 2 to 5 illustrate a number of different possible arrangements of the compressing elements 130 and heating chamber 110.

Figures 2A to 2C illustrate an example of a heating chamber 110 according to the present invention. Figure 2A shows a longitudinal cross section through an exemplary heating chamber 110 according to the present invention. As described above the heating chamber 110 comprises a tubular conductive shell 112 with an open end 111 for receiving the consumable 120 and an opposing closed end. In this example the heating chamber 110 comprises a substantially circular cross section as shown in Figures 2B and 2C and is thus preferably configured for receiving a cylindrical consumable 120. In this example the compressing elements 130 comprise strips of material which run along a portion of a length of the heating chamber between a first end 131 of the compressing element 130 and a lower second end 132.

The compressing elements 130 comprise strips of a shaped memory alloy or a bimetallic material configured to bend inwardly as shown in Figure 1 B during heating. As will be described in more detail below an external heater may be applied to the outer surface of the heating chamber wall 112 so that heat is conducted through the conductive shell 112 of the heating chamber and through the compressing elements 130 to the consumable 120 when received in the chamber. Alternatively, the compressing elements 130 may comprise a heating element themselves with the compressing elements 130 connected to the power source to provide a current to heat the heating element of the compressing elements to provide heating of the consumable.

Figures 2B and 2C show a cross section along line A-A of Figure 2A through the heating chamber 110 with Figure 2B showing the heating chamber 110 below the threshold temperature and Figure 2C showing the heating chamber 110 above the threshold temperature. As shown in Figures 2B and 2C, in this example there are four longitudinal strips of deformable material positioned around the internal circumference of the heating chamber wall 112. Each compressing element 130 runs along a portion of the total length of the heating chamber 110, where the portion preferably corresponds with the position of the aerosol substrate 121 of the consumable.

In other examples there may be a single compressing element 130 or a different number of compressing elements 130 positioned around the internal circumference of the heating chamber wall 112. As shown in Figure 1 B when the temperature exceeds the threshold temperature a middle portion 133 of the compressing element bends inwardly to compress the aerosol substrate 121. This is shown in cross section in Figure 2C in which the middle part of the compressing element 130 extends radially inward into the internal volume of the heating chamber to restrict the internal dimensions of the heating chamber 110 and compress the consumable.

The cross section of the heating chamber 110 of Figure 2A shows that the heating chamber may comprise a number of other features. For example, it may comprise internal protrusions 114 near the open end 111 which extend from the internal surface 113 of the heating chamber wall 112 into the internal volume of the heating chamber to provide additional gripping of the consumable when received in the chamber 110. The base of the heating chamber 115 at the closed end may also comprise an internal protrusion which extends upwardly into the internal volume of the heating chamber to abut the end of the aerosol substrate 121 when it is received in the heating chamber 110. In the example shown these features 114, 115 are stationary features of the heating chamber shell 112 created during manufacture of the heating chamber 110. However it will be appreciated that they could also comprise compressing elements 130 configured to deform at the same or different temperatures to the compressing elements 130 shown in Figure 2A to 2C. These additional compressing elements 130 could further assist in gripping the consumable and improving the thermal transfer from the heater to the aerosol substrate 121 of the consumable 120. In the example of Figure 2 the compressing elements 130 are separate to the shell 112 of the heating chamber 110 and lie within the heating chamber 110, along the inner wall 113 of the heating chamber 130. The ends of the compressing elements 131 , 132 may be attached to the inner surface 131 of the heating chamber wall 112 with the central section 133 of the compressing element 130 being free to move away from the inner surface 113 of the heating chamber wall 112 as shown in Figure 1 B and Figure 2C. For example, the ends may be soldered to the heating chamber wall or be intermediately fixed to the heating chamber by brackets.

Figures 3A to 3C show an alternative example of a heating chamber 110 according to the present invention in which the compressing elements 130 form part of the wall 112 of the heating chamber 110 itself, rather than being separate elements lying within the heating chamber 110 as in the example of Figure 2. In the example of Figure 3 the compressing elements 130 comprise longitudinal strip portions of the heating chamber wall 112 which comprise a material configured to change shape under heating to contact a consumable 120 received in the heating chamber 110. As with Figure 2, in this example there are four longitudinal strips provided as the compressing elements 130 which are arranged periodically around the circumference of the heating chamber wall 112, each extending along a portion of the length of the heating chamber between a first end 131 and a second end 132.

Figures 3B and 3C again show the compressing elements 130 below and above the threshold temperature respectively. As shown in Figure 3C, as the temperature of the heating chamber 130 rises above the threshold temperature the portions of the heating chamber wall comprising the compressing elements 130 deform to extend radially inward into the internal volume of the heating chamber 110. In this example, rather than the longitudinal ends 131 , 132 of the compressing elements 130 being fixed with a longitudinal central portion of the compressing element bending inwardly into the internal volume of the heating chamber 110, in this example the edges of the strips in the circumferential direction 134, 135, shown in Figure 3B, remain fixed with the central portion between the two ends 134, 135 bending inwardly into the heating chamber. In this way, as the temperature exceeds the threshold temperature, the compressing elements deform to provide longitudinal ridges running along the elongate axis of the heating chamber on the inner wall 113. The compressing elements 130 of this example could equally be configured to deform in the way shown in Figure 1 B and 2C.

As described above with respect to Figure 2, although in the example of Figure 3 there are four compressing elements 130 provided periodically around the circumference of the heating chamber there may be a single compressing element 30 or a different number of compressing elements. Figure 3A further shows the additional shaped features of the heating chamber wall, in particular one or more internal protrusions 114 near the opening 111 of the heating chamber arranged around the circumference and a base protrusion 114 extending upwardly from the inner surface of the closed end of the heating chamber 110.

Although as shown these features are parts of the heating chamber wall and fixed they may equally be made of a temperature dependent material such as a shaped memory alloy or bimetallic element such that they are configured as compressing elements 130 configured to extend into the internal volume of the heating chamber 110 during heating. In this way the internal volume of the heating chamber 110 is further constricted such that the multiple compressing elements 130 contact the consumable 120 from multiple directions to securely hold it within the heating chamber and improve the thermal transfer to the aerosol substrate 121. Figures 4A and 4C schematically illustrate a further example of a heating chamber 110 for an aerosol generating device according to the present invention. In Figures 4A and 4B the consumable 120 including the mouthpiece 122 and aerosol substrate 121 is shown received within the heating chamber 110. In this example, rather than being longitudinal strips, the compressing elements 130 comprise annular elements 130 extending around the circumference of the heating chamber 110 and spaced along the length of the heating chamber 110. The annular compressing elements 130 are configured to radially contract under heating as shown in Figure 4B to grip the consumable 120 when the threshold temperature is exceeded. Figure 4A shows the heating chamber at ambient temperature below the threshold temperature such that the annular compressing elements 130 are retracted to allow the consumable 120 to be received and removed through the opening 111 of the heating chamber. As the temperature is exceeded as shown in Figure 4B the annular compressing elements 130 deform to grip the aerosol substrate 121 of the consumable 120. In a variant, the elements 130 extend only along a part of the circumference of the heating chamber, for example, along a circumferential part of from 180 to 350°.

As described above with respect to Figures 2 and 3, the annular compressing elements 130 may either form part of the conductive shell 112 of the heating chamber 110 or they may be separate elements provided within the heating chamber such that they run around the internal circumference of the heating chamber wall 112. Again, the compressing elements 130 may comprise heating elements themselves or they may comprise conductive material such that an external heating element may be applied to the outer surface of the heating chamber 110 such that heat is conducted through the shell and compressing elements to the aerosol substrate 121. It will be appreciated that the compressing elements may be provided in any other suitable form such that they deform to contract and restrict the internal volume of the heating chamber 110 and compress the consumable 120. For example, rather than be provided as a plurality of individual annular compressing elements 130 the compressing element may be provided as a single coiled structure which spirals around the internal surface of the heating chamber 110 and radially contracts inwardly to restrict the internal volume and compress the consumable when the threshold temperature is exceeded.

Figures 5A and 5B show possible ways in which the heater may be applied to the heating chamber in order to heat the consumable during use. Figure 5A shows the heating chamber 110 with an external heater 150 applied to an outer surface of the heating chamber shell 112. In this example the external heater comprises a thin film heater comprising a flexible electrically insulating (dielectric) backing film 152 and a conductive heating element track 151 provided across the thin film backing film 152. By connecting the heating element 151 to the power supply the heater track 151 may be heated through resistive heating and accordingly the heating chamber and substrate 121 may be heated.

In the case of Figure 5A the compressing elements (not shown) may be provided within the heating chamber 110 or as part of the heating chamber shell 112. By providing current to the heater 150 heat is transferred through the conductive shell 112 and the compressing elements (not shown) to the consumable 120. In the example of Figure 5B, the compressing elements 130 themselves comprise the heating elements. In particular the compressing elements may comprise appropriate material to provide resistive heating when a current is applied. The compressing elements 130 comprising the heating elements may be connected to the current with electrical contact 153 wherein the compressing elements 130 run between the electrical contacts 153 such that the currents may be applied to the compressing elements 130.

A current may be applied directly to the temperature dependent material, such as the SMA or bimetallic element, or the compressing elements 130 may comprise both a temperature dependent material and a resistive heating material (such as stainless steel, titanium, nickel, Nichrome etc.), such that a current is applied only to the resistive heating material. In either case, the compressing elements are directly heated in order to provide heating directly to the aerosol substrate 121 of the consumable 120 when received in the chamber 110.

Claims

1. An aerosol generating device, comprising: a heating chamber arranged to receive an aerosol substrate, the heating chamber operable to heat the aerosol substrate to generate an aerosol; a compressing element configured to change shape above a threshold temperature; such that the compressing element extends radially inward into the heating chamber during a heating operation of the aerosol generating device.

2. The aerosol generating device of claim 1 , wherein the heating chamber comprises an opening and is arranged to receive the aerosol substrate into the heating chamber through the opening in a longitudinal direction; and wherein the compressing element is positioned at an inner surface of the heating chamber and configured to change shape above the threshold temperature to extend into the heating chamber in a direction perpendicular to the longitudinal direction.

3. The aerosol generating device of claim 1 or claim 2 wherein the heating chamber is tubular and arranged to receive a tubular aerosol substrate, wherein the compressing element is configured to extend into the heating chamber in a direction perpendicular to the elongate axis of the tubular aerosol substrate.

4. The aerosol generating device of any preceding claim comprising a plurality of compressing elements arranged around a circumference of the heating chamber.

5. The aerosol generating device of claim 4 wherein the compressing elements comprise longitudinal strips running along a length of the heating chamber and spaced around the circumference of the heating chamber, the longitudinal strips configured to bend inwardly into the heating chamber above the threshold temperature.

6. The aerosol generating device of claim 4 wherein the compressing elements comprise at least partially annular elements extending around at least a part of the circumference of the heating chamber and spaced along the length of the heating chamber, the annular element configured to contract above the threshold temperature

7. The aerosol generating device of any preceding claim, wherein the compressing element is configured to change shape due to heating by the heating chamber during a heating operation of the aerosol generating device..

8. The aerosol generating device of any preceding claim wherein the compressing element is positioned within the heating chamber; wherein the compressing element: lies along an inner wall of the heating chamber below the threshold temperature to allow an aerosol substrate to be inserted and removed from the chamber; and extends away from the inner wall into the heating chamber above the threshold temperature.

9. The aerosol generating device of any of claims 1 to 7 wherein the compressing element forms part of a wall of the heating chamber and extends into the heating chamber to reduce the inner volume of the heating chamber above the threshold temperature.

10. The aerosol generating device of any preceding claim wherein the compressing element comprises a heating element.

11. The aerosol generating device of any of claims 1 to 9 wherein the compressing element comprises a heat conductive material and the aerosol generating device further comprises a heater arranged to transfer heat to the compressing element.

12. The aerosol generating device of any preceding claim further comprising a heater positioned around an outer surface of the heating chamber, wherein the heater is preferably a thin film heater.

13. The aerosol generating device of any preceding claim wherein the compressing element comprises a shape memory alloy.

14. The aerosol generating device of any preceding claim wherein the compressing element comprises a bimetallic element.

15. The aerosol generating device of any preceding claim wherein the compressing element is configured to return to its original shape when the temperature of the heating chamber drops below the threshold temperature, thereby retracting from the heating chamber to allow an aerosol substrate to be inserted into or removed from the chamber.

16. The aerosol generating device of any preceding claim further comprising an aerosol substrate, wherein the aerosol substrate comprises a material which shrinks when heated; wherein the compressing element is arranged such that contact is maintained between the compressing element and the aerosol substrate during a heating operation of the aerosol generating device.

17. The aerosol generating device of claim 16 wherein the aerosol substrate comprises tobacco.