FIELD The present disclosure relates to a heating assembly for an aerosol generating device. Also provided are systems comprising aerosol generating devices with such heating assemblies and aerosol generating devices. The disclosure is particularly applicable to portable aerosol generation devices, which may be self- contained and of a low temperature. Such devices may heat, rather than burn, tobacco or other suitable aerosolisable materials by conduction, convection, and/or radiation, to generate an aerosol for inhalation. Heating assemblies in accordance with the invention are safe, reliable, easily manufactured, and have low power requirements. BACKGROUND

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 smoking 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 as in conventional tobacco products.

A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn device. Devices of this type generate an aerosol or vapour by heating an aerosol generating article that typically comprises moist leaf tobacco or other suitable aerosolisable material to a temperature typically in the range 150°C to 350°C. Heating an aerosol generating article, 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. Furthermore, the aerosol produced by heating the tobacco or other aerosolisable material does not typically comprise the burnt or bitter taste resulting from combustion and burning that can be unpleasant for the user and so the substrate does not therefore require the sugars and other additives that are typically added to such materials to make the smoke and/or vapour more palatable for the user.

However, the heat management of aerosol generating devices can prove problematic, especially during periods of frequent or prolonged use. Furthermore, the power required to heat aerosol generating articles is very high, requiring batteries of conventional devices to be frequently recharged or replaced. It is also desirable to simplify the manufacture of aerosol generating devices.

It is an object of the present invention to address the above issues and to provide an aerosol generating device with improved safety and reduced power requirements.

SUMMARY OF INVENTION

According to a first aspect of the invention there is provided a heating assembly for an aerosol generating device comprising an elongated heating cup comprising a tubular wall forming a cavity for receiving a tubular aerosol generating article therein and a resistive heater arranged for heating upon application of an electrical current thereto; the resistive heater being arranged in thermal conduction on the outer surface of the tubular wall; wherein the tubular wall comprises, at its circumference, a successively circumferential and alternate distribution of substantially planar wall portions and convex wall portions; wherein the number of substantially planar wall portions is three or more; and, wherein the substantially planar wall portions are substantially planar both at the outer surface and inner surface of the tubular wall.

Therefore, a tubular aerosol generating article - e.g. a tobacco stick - may be inserted into the heating cup of the heating assembly and heated using the resistive heater to release an aerosol. Subsequently the aerosol may be inhaled by a user. As will be discussed below, such heating assemblies require lower overall temperatures to generate these aerosols and therefore require less power to operate. In addition the heating assemblies are convenient to manufacture and simple to use.

The substantially planar wall portions are preferably flat, planar sections of the tubular wall that extend longitudinally along the length of the heating cup. The substantially planar wall portions may extend in a tangential plane - i.e. a plane perpendicular to the radial direction extending outwards from a centreline and parallel to the longitudinal axis of the heating cup.

By “substantially planar” it will be appreciated that the substantially planar wall portions are broadly flat and planar across their surfaces. In particular the substantially planar wall portions will be significantly flatter than the intervening convex wall portions. However, the substantially planar wall portions may still comprise small curves and/or minor surface reliefs. In preferred examples the substantially planar wall portions are planar (i.e. flat), such that the outer and inner surfaces of the tubular wall are planar.

In contrast the convex wall portions which sit between and join the substantially planar wall portions may be curved or define an internal angle. For instance, the convex wall portions may extend circumferentially between two adjacent substantially planar wall portions. Adjacent substantially planar wall portions are preferably connected by the convex wall portions, such that there are a corresponding number of substantially planar wall portions and convex wall portions. As such, it will be appreciated that the convex wall portions are convex when considering the outer surface of the tubular wall.

The distance between the opposing substantially planar wall portions is typically less than the distance between the opposing convex wall portions. Thus an aerosol generating article that is inserted into the cavity of the heating cup will tend to contact the substantially planar wall portions rather than the convex wall portions. Indeed, the substantially planar wall portions are preferably configured to contact the aerosol generating article during use, and may grip (i.e. hold or retain) the aerosol generating article in place within the cavity of the heating cup. The three or more substantially planar wall portions, which are spaced around the circumference of the tubular wall, accurately and stably hold the article in an appropriate position. Thus the tubular aerosol generating article is easily aligned and centred within the heating cup by the three or more substantially planar wall portions. Therefore, it is easy for a user to correctly insert an aerosol generating article into the heating cup. Hence the heating assembly is safe and straightforward to use.

The resistive heater is provided on the tubularwall, the term “on” being understood herein as meaning in contact with or above an underlying component. Good thermal transfer is achieved between the aerosol generating article and resistive heater. Heat may be quickly transferred by conduction from the resistive heater to the aerosol generating article via the tubular wall. This heat transfer is particularly quick through the substantially planar wall portions which contact or grip the aerosol generating article. This minimises the power required to heat the aerosol generating article and increases safety as the maximum overall temperature of the heating assembly may be reduced.

The resistive heater is preferably configured to raise the temperature of an aerosol generating article received within the cavity of the heating cup to a temperature from 150 degrees Celsius to 350 degrees, more preferably from 190 to 310 degrees Celsius, more preferably still from 230 to 260 degrees Celsius. These temperatures are well suited to generate aerosols from a variety of aerosolisable materials including moist leaf tobacco.

In addition, it will be appreciated that a tubular heating cup with alternating substantially planar and convex wall portions is simple to construct, and may be quickly and conveniently manufactured. By “arranged in thermal conduction” it will be appreciated that heat may be transferred by conduction between the resistive heater and the outer surface tubular wall. As such, the resistive heater may be arranged in direct thermal contact with the tubular wall, being arranged on the tubular wall. As such, the resistive heater may be provided in direct contact with the tubular wall or above the tubular wall in which case the resistive heater and tubular wall may be separated by an intervening layer such as an electrically insulating layer. As such there are no gaps or voids between the resistive heater and the tubular wall. This ensures good thermal transfer between the resistive heater and the tubular wall.

Preferably the substantially planar wall portions are evenly distributed at the circumference of the tubular wall. In other words the substantially planar wall portions are preferably consistently spaced around the circumference of the tubular wall (although his is not essential). This rotationally symmetric arrangement simplifies the production of the tubular wall. Furthermore an aerosol generating article received within the heating assembly may be easily positioned and secured at the centre of the elongated heating cup. Consequently, the aerosol generating article may be evenly heated by the heating assembly. This reduces the power requirements of the heating assembly and maximising the lifespan of the aerosol generating article.

In preferred examples the number of substantially planar wall portions is from three to five. Elongated heating cups that comprise tubular walls with three planar areas (spaced by three convex wall portions) provide particularly stable positioning for aerosol generating articles. Heating cups that comprise tubular walls with larger numbers of substantially planarwall portions are equally possible. However, manufacture of these elongated heating cups with larger numbers of substantially planar wall portions is more complicated, in part because heater tracks applied to the surfaces of the tubular walls (e.g. to the planarwall portions) must be reduced in size and/or span multiple wall portions.

In particularly preferred examples each substantially planarwall portion is covered by a respective resistance track of the heater. Thus a resistance track of the heater overlies each substantially planar wall portion, said resistance track being provided in direct contact with or above the planar outer surface of the respective substantive planar wall portion. The resistance tracks are configured to heat up as electrical current passes therethrough. Therefore heat from the resistance track(s) may be rapidly transferred to an aerosol generating article held or gripped by the planar wall portions. This arrangement is very efficient. Providing the resistance tracks of the heater adjacent to the point at which the elongated heating cup is in contact with the aerosol generating articles allows rapid heat transfer. Hence, arranging resistance tracks on the outer surface of the substantially planar wall sections reduces the overall temperature the heating assembly is required to heat the elongated heating cup to and reduces the power requirements of the heating assembly.

The resistance tracks of different substantially planar wall portions may be placed in series or parallel. In such examples, the resistance tracks form part of a single resistance circuit. However, alternatively, the heating assembly may comprise a plurality of separate resistance circuits. For instance, each circuit may comprise a resistance track provided over a respective substantially planar wall portion.

Preferably, the resistance tracks of different substantially planar wall portions are connected by lower resistance connection tracks. These connection tracks have lower electrical resistance than the resistance tracks covering the substantially planar wall portions and therefore preferably do not generate significant amounts of heat when supplied with electrical current. Therefore, power may be conserved and significant amounts heat is only be applied to the heating cup at the substantially planar wall portions (which offers particularly efficient heat transfer as discussed above).

The lower resistance connection tracks are preferably positioned on the convex wall portions. In other words the connection tracks are arranged in contact with or above the convex wall portions. As such, the resistance tracks at each substantially planar wall section may be spaced around the circumference of the tubular wall by connection tracks which extend across the intervening convex wall portions. In this manner the lower resistance connection tracks may electrically connect adjacent resistance tracks to form an electrical circuit around the circumference of the tubular wall.

Therefore, it will be appreciated that the heating assembly may comprise a corresponding number of resistance tracks and lower resistance connection tracks as the number of substantially planar wall portions and convex wall portions respectively. Moreover, the resistance tracks and lower resistance connection tracks may be successively and alternatively arranged around the circumference of the tubular wall in a corresponding manner to the substantially planar and convex wall portions.

Preferably the lower resistance connection tracks are wider than the resistance tracks on the substantially planar wall sections. As such, the wider tracks of the lower resistance connection tracks have lower electrical resistance than the resistance tacks and may not generate significant amounts of heat, even when formed of the same materials as the resistance tracks.

Together the resistance tracks and connection tracks form heating tracks of the resistive heater. The overall electrical resistance of these heating tracks may be from 0.5 to 1.5 Ohm, more preferably from 0.8 to 1.2 Ohm, more preferably still from 1.0 to 1.1 Ohm. In a particularly preferred example the overall resistance of the resistive heater is 1.05 Ohm.

Preferably the tubular wall comprises a metal or metal alloy of substantially constant thickness. Metals and metal alloys have good thermal transmission properties and may rapidly transfer heat from the resistive heater to an aerosol generating article within the heating assembly. Suitable materials include stainless steel, steel, aluminum and copper. Forming the tubular wall of a material with a substantially constant thickness simplifies manufacture, especially where the tubular wall is formed of a metal. In preferred examples the tubular wall comprises 1mm thick stainless steel. In preferred examples the heater is formed as a thin film wrapped about the tubular wall of the elongated heating cup. Such a thin film heater, which may comprise the resistance tracks and lower resistance connection tracks discussed above, may be easily manufactured separately from the tubular wall and subsequently applied to the outer surface of the tubular wall in the appropriate arrangement (e.g. using an adhesive or a heat shrink film). This approach particularly convenient since the heater may be conveniently manufactured in a flat or planar form before it is applied to (i.e. wrapped around) the circumference of the tubular wall. For instance, the resistive heater may be a thin film heater manufactured in accordance with the methods and techniques described in PCT/EP2020/074150 (claiming priority from EP19196024.4) or PCT/CN2019/104804, the disclosures of which are incorporated herein by reference.

In equally preferred examples the resistive heater comprises heating tracks directly printed on the outer surface of the tubular wall. These heating tracks, which may comprise any of the resistance tracks and lower resistance connection tracks discussed above, may be quickly and conveniently applied directly to the tubular wall. Printing heating tracks in this manner is quick and minimises material waste. In some preferred examples the heating tracks may be printed directly onto tubular wall such that the heating tracks are provided in contact with the outer surface of the tubular wall. However, in further examples an intervening layer (e.g. an electrically insulating layer) may be provided between the heating tracks and the tubular wall such that the heating tracks are arranged above the surface of the tubular wall.

Alternatively, the resistive heater may comprise a plurality of separate thin film segments each of which supports a single resistance track and each of which is applied on or over a corresponding substantially planar wall portion. In further examples the heater track may be applied to the heating cup using a transfer.

In some preferred examples the tubular wall has an electrically insulating layer thereon. Preferably the electrically insulating layer is a coating or polymer film. However alternative dielectric materials may also be used. The electrically insulating layer may separate the resistive heater from the tubular wall. Thus the electrically insulating layer may be provided on the outer surface of the tubular wall, between the tubular wall and the heating tracks discussed above. This may be necessary where the tubular wall is formed of an electrically conductive material. In these examples the resistive heater may be provided in contact with the electrically insulating layer such that it remains in thermal conduction with the underlying tubular wall.

Where the heater is a thin film heater, the electrically insulating layer may be the dielectric backing film (i.e. a carrier film) onto which the tracks of the heater are initially applied, the thin film heater being wrapped or applied around the tubular wall such that the backing film is arranged between the resistance tracks and the tubular wall. Alternatively, an electrically insulating layer may be applied to the outer surface of the tubular wall after the tubular wall is formed and before heating tracks are printed onto the tubular wall.

In further examples an electrically insulating layer may additionally or alternatively be provided over the resistive heater. This may cover and protect the underlying heating tracks. For instance, where the heater is a thin film heater a further dielectric film may be provided over the tracks of the heater so as to enclose it.

In preferred examples the planar or substantially planar wall portions end before a bottom wall of the heating cup, the distance between the bottom wall of the heating cup and the end of the planar or substantially planar wall portions being at least 2 mm. This may allow air to circulate at the closed bottom end of the heating cup. This may allow for heat distribution through the heating cup to be more consistent in use.

Preferably, the planar or substantially planar wall portions are configured to compress an aerosol generating article received in the heating cup at the location of the substantially planar wall portions. As a result the aerosol generating article is securely retained in the heating cup. Furthermore, the contact area between the aerosol generating article and the substantially planar wall portions is increased such that heat may be more quickly transferred from the planar wall portions (and any overlying resistance tracks) to the aerosol generating article. Therefore, aerosol generating devices incorporating the heating assemblies according to the invention may be made easier to use and may require less power.

In preferred examples the convex wall portions define an airflow path between an aerosol generating article received in the heating cup and the heating cup. As such, there may be a gap or void defined between the convex wall portions and an aerosol generating article received in the heating cup through which air may flow. This void may extend longitudinally along the heating cup. The flow of air along this air flow path may allow for heat to be transferred through the heating cup during use. Thus the temperature distribution within the heating cup may be more consistent. This improves both efficiency, safety and taste of the aerosol generated by the aerosol generating article since local hot and cold spots may be reduced or avoided.

According to a further aspect of the invention there is provided a system comprising an aerosol generating device with a heating assembly in accordance with the preceding aspect of the invention and an aerosol generating article configured to be inserted in the cavity such that the aerosol generating article is compressed at the location of the planar or substantially planar wall portions.

The aerosol generating device within this system requires reduced power and lower internal temperatures to generate aerosols from the aerosol generating article. Thus the aerosol generating device may be made safer, more compact and more reliable.

The system may comprise a heating assembly including any of the optional or preferable features discussed above. Consequently, the system may offer any of the corresponding benefits discussed above. The aerosol generating device may comprise a variety of further features. These may include: a power source (e.g. a battery); one or more temperature sensors; a controller; and thermal insulation. The temperature sensor(s) may be configured to measure the temperature of the resistive heater, the aerosol generating device and/or the internal temperature of the heating cup. The controller may be configured to control or regulate the operation of the resistive heater - e.g. by controlling the electrical power supplied to the heater from a power source. The controller may be configured to control the operation of the resistive heater based on measurements received from the temperature sensor(s) discussed above. The thermal insulation may be arranged around the heating assembly and be configured to restrict or reduce the flow of heat away from the heating cup. Therefore, the aerosol generating device may be made more efficient and safer.

The aerosol generating article is preferably tubular. In preferred examples the aerosol generating article is a tobacco stick or equivalent article.

BRIEF DESCRIPTION OF DRAWINGS

Specific examples of the invention will now be discussed with reference to the following figures:

Figures 1a and 1b show two perspective views of a heating assembly in accordance with the invention;

Figure 2 shows a schematic cross section of a heating assembly in accordance with an embodiment of the invention;

Figure 3a shows a schematic cross section of an aerosol generating device comprising a heating assembly in accordance with the invention;

Figure 3b shows a schematic cross section of a system in accordance with an embodiment of the invention, the system comprising an aerosol generating device as shown in Figure 3a and an aerosol generating article. DETAILED DESCRIPTION

Figures 1a and 1b show perspective views of a heating assembly 10 configured to receive and heat an aerosol generating article (e.g. a tubular aerosol article such as a tobacco stick). The aerosol generating article heated using the heating assembly 10 will release an aerosol that may subsequently be inhaled by a user.

The heating assembly 10 comprises an elongated heating cup 12 comprising an open end 12a and an opposing closed bottom end 12b at which a bottom wall is provided. Between the open end 12a and bottom end 12b extends a tubular wall 14. The tubular wall 14 and the bottom end 12b define an internal cavity configured to receive an aerosol generating article. A tubular aerosol generating article may be partially or entirely inserted into the heating cup 12 through the open end 12a such that it is concentrically surrounded by the tubular wall 14.

As will be seen from the figure, the heating cup 12 comprises a lip 12c at its open end 12a. The lip 12c is flared, extending radially outwards from the tubular wall 14. This flared lip 12c allows for aerosol generating articles to be easily inserted into the heating cup 12 during use. However, such a lip positioned at the rim of the cup is not essential and other embodiments of the invention may not include one.

The tubular wall 14 has a substantially constant thickness around its circumference and comprises three planar wall portions 14a and three convex wall portions 14b. The planar wall portions 14a and convex wall portions 14b are alternately distributed around the circumference of the tubular wall 14, such that each planar wall portion 14a is spaced from the remaining planar wall portions 14a by a convex wall portion 14b (and vice versa). As will be seen from Figure 1a the planar wall portions 14a are planar at both the outer surface and inner surface of the tubular wall 14. The planar wall portions 14a and convex wall portions 14b are consistently sized such that the planar wall portions 14a are evenly distributed at and around the circumference of the tubular wall 14. A tubular aerosol generating article inserted into the cavity of the heating cup 12 may contact and be retained by the planar wall portions 14a, the planar wall portions 14a compressing and deforming the aerosol generating article local to the point of contact between the aerosol generating article and the inner surface of the planar wall portion 14a. Thus the aerosol generating article may be securely retained in the heating cup 12, and good thermal conduction may be achieved between the planar wall portion 14a and the aerosol generating article.

The heating assembly 10 further comprises a resistive heater 16 arranged around the outer (i.e. exterior surface) of the tubular wall 14 of the heating cup 12. The resistive heater 16 is arranged in direct thermal contact with the tubular wall 14 of the heating cup, and is configured to apply heat to the internal cavity (and any aerosol generating article contained therein) within the aerosol generating article through the tubular wall 14 of the heating cup 12. As will be appreciated from the figures, the resistive heater 16 is provided in thermal conduction with the outer surface of the tubular wall 14, the resistive heater 16 being arranged on the surface of the tubular wall 14 such that heat may be conducted between the resistive heater and the tubular wall 16.

Specifically, as shown the resistive heater 16 comprises three electrically conductive resistance tracks 16a connected by three electrically conductive lower resistance connection tracks 16b. The resistance tracks 16a are connected in series by the lower resistance connection tracks 16b (although this is not essential).

Each of the three resistance tracks 16a is provided on a respective planar wall portion 14a of the tubular wall 14. Thus each resistance track 16a is in thermal contact with the respective planar wall portion 14a that it covers. As electrical current flows through the resistance tracks 16a are configured to heat up through resistive heating. This heat is transferred to the adjacent planar wall portion 14a, and through the planar wall portion 14a to the interior of the heating cup 12. Thus an aerosol generating article inserted in the heating cup 12 will be efficiently heated by the heating assembly 10 since the article is in strong thermal contact with the resistance tracks 16a via the tubular wall 14, the resistance tracks 16a being positioned on or above (i.e. adjacently) the planar wall portion 14a by which the aerosol generating article contacts the heating cup 12.

The three lower resistance connection tracks 16b are each provided between two adjacent resistance tracks 16a on a respective convex wall portion 14b of the tubular wall 14. As will be seen, the connection tracks 16b have significantly larger dimensions than the resistance tracks 16a, being wider and thicker than the resistance tracks 16a. Thus the connection tracks 16b have a lower resistance than the resistance tracks 16a and do not heat the convex wall portions 14b significantly during use.

As will be seen from Figure 1 , the planar wall portions 14a and convex wall portions 14b each extend along substantially the whole length of the tubular wall 16 and the majority of the length of the heating cup 12. As shown, the planar wall portions 14a and convex wall portions 16b extend between the closed bottom end 12b of the heating cup 12 and the flared lip 12c at the open end 12a of the heating cup 12. These, planar wall portions 14a that extend over substantially the whole length of the tubular wall 16 and the majority of the length of the heating cup 12 enable rapid and consistent transfer of heat to the contents of the heating cup 12 and along the full length of the heating cup 12. This reduces energy requirements and provides a consistent generation of aerosols.

In preferred embodiments of the invention, planar wall portions 14a and/or the convex wall portions 14b extend along at least 75% of the length of the heating cup 12, more preferably at least 80%, more preferably still at least 90% (although this is not essential). Similarly the planar wall portions 14a and/or the convex wall portions 14b preferably extend along at least 75% of the length of the tubular wall 16, more preferably at least 80%, more preferably still at least 90% (although this is not essential). Figure 2 shows a schematic version of a heating assembly 20 in cross section. The cross section extends in a plane perpendicular to a longitudinal axis through the heating assembly 20. This heating assembly 20 shares many features and advantages with the heating assembly 10 shown in Figures 1a and 1b. The heating assemblies 10, 20 of these figures operate in the same manner and have similar structures. The reference signs of features shared between these two examples have been incremented by 10 between the figures.

The heating assembly 20 comprises a heating cup 22 comprising an internal cavity 28 into which a tubular aerosol generating article may be inserted. The heating cup 22 comprises a tubular wall 24 which defines the circumferential boundary of the cavity 28. Around the tubular wall 24 is provided a resistive heater comprising alternating electrically conductive resistance tracks 24a and lower resistance connection tracks 24b. As will be seen, the resistive heater is arranged in thermal conduction with the outer surface of the tubular wall 24 (i.e. the surface of the tubular wall 24 opposite the cavity).

The tubular wall 24 comprises three planar wall portions 24a and three curved convex wall portions 24b. The planar wall portions 24a and convex wall portions 24b are alternately arranged around the circumference of the tubular wall 24, such that a convex wall portion 24b is located between each planar wall portion 24a around the circumference of the tubular wall 24 (and vice versa). The planar wall portions 24a and convex wall portions 24b are consistently (i.e. evenly) distributed around the circumference of the tubular wall.

As seen from Figure 2, the cup 20 comprises a lip 22c which extends around the tubular wall 24. As in Figure 1, the lip 22c is positioned at an open end of the heating cup 22. The cross section shown in Figure 2 looks towards this open end do the heating cup. As such, the lip 22c appears to surround the tubular wall 24 of the cup 20 in the cross section. The lip 22c is preferably flared so as to enable aerosol generating articles to be easily inserted into the cup 12 during use. Having said this, it will be appreciated that the lip 22c is optional and is not essential to the action of the resistive heater 26 discussed below. An exemplary cross section of an aerosol generating article which may be heated using the heating assembly 20 in an uncompressed state before insertion into the heating assembly 20 is indicated by broken line A. As will be seen, the article in its uncompressed state has a circular cross section and is preferably substantially cylindrical (although this is not essential and heating assemblies in accordance with the invention may receive, and be configured to operate with, aerosol generating devices with a variety of shapes). The cross section of the article is sufficiently great that it may not fit within the cavity 28 without contacting the planar wall portions 24a of the tubular wall 24. Instead, when inserted into the heating cup 22 (i.e. into cavity 28) the planar wall portions 24a will contact and push against the aerosol generating article. This force will deform the aerosol generating article such that it is compressed local to the planar wall portions 24a.

The deformation of the aerosol generating article once the article been inserted into the heating cup 12 is shown schematically by the broken lines A'. As will be seen, the article (which originally was of a substantially circular cross section indicated by line A) is compressed local to the planar walls 24a such that the exterior of the article in this compressed state conforms to and follows the interior surface of the planar walls 24a of the tubular wall 24. This deformation increases the contact surface shared between the article and the planar wall portions 24a and ensures that heat may be rapidly transferred between the article and planar wall portions 24a.

It will be appreciated that the aerosol generating article indicated by broken lines A and A' is not compressed local to the convex wall portions 24b which are positioned at a greater radial distance from the centre of the heating cup 24 than the planar wall portions 24a. In these regions the exterior surface of the article will substantially follow its original, uncompressed shape as shown by line A. As such an empty channel 28a may be left between the article and each convex wall portion 24b. These empty channels 28a (i.e. voids between the article and the convex wall portions 24b) define airflow paths which extends longitudinally along the heating assembly between the article and the heating cup 22. Air may flow along these empty channels 28a in use ensuring that the distribution of heat throughout the cavity 28 and the article within the heating cup 22 is consistent. This ensures consistent generation of aerosol and reduces energy requirements.

It will be appreciated that the planar wall sections 14a of the heating cup 12 discussed above with reference to Figures 1a and 1b will compress an aerosol generating article received therein in a similar manner.

The resistive heater 26 comprises three electrically conductive resistance tracks 26a connected by three electrically conductive lower resistance connection tracks 26b.

Each of the three resistance tracks 26a covers a respective planar wall portion 24a of the tubular wall 24. As shown, each resistance track 26a is in direct thermal contact (i.e. thermal conduction) with the respective planar wall portion 24a and any aerosol generating article inserted into the heating assembly 20. As current flows through the resistance tracks 26a are configured to heat up through resistive heating. This heat is transferred to the adjacent planar wall portion 24a, and through the planar wall portion 24a to the interior of the heating cup 22. An aerosol generating article within the heating cup 22 which is compressed by the planar wall portions (e.g. an aerosol generating article with a cross section matching broken line A) may be rapidly heated in this manner. Thus the overall temperature of the resistive heater and its power requirements may be reduced.

The three lower resistance connection tracks 26b are each provided between two adjacent resistance tracks 26a on a respective convex wall portion 24b of the tubular wall 24. The connection tracks 26b have a lower resistance than the resistance tracks 26a and preferably do not heat the convex wall portions 24b significantly during use. As shown, the lower left connection track 26b comprises an electrical connection 29 by which the resistive heater may be connected to further electronic components (e.g. a battery and/or controller). The flow of air through a heating cup and therefore the heat distribution through the heat cup may further be improved if the planar wall portions (which contact an aerosol generating article when inserted into the heating cup as discussed above) end before the closed end of the heating cup. For instance, as shown in Figures 1a and 1b the planar wall portions 14a end approximately 2mm before the bottom wall 12b of the heating cup. In such examples air may circulate around the end of an aerosol generating article inserted furthest into the heating cup and between the empty channels defined between the aerosol generating article and the different convex wall portions.

In each of the examples discussed above with reference to Figures 1a, 1b and 2 the heating assemblies 10, 20 may be formed of a variety of materials. Stainless steel with a thickness of 1mm is particularly preferred for use as the tubular wall 14, 24 of the heating cups 12, 22 as it is cheap, easy to work and offers good thermal properties. The heating tracks (i.e. the resistance tracks 16a, 26a and connection tracks 16b, 26b) may be formed of any suitable electrically conductive material. Preferably the heating tracks of each heating assembly 10, 20 have a total resistance of from 0.5 to 1.5 Ohm, preferably from 0.8 to 1.2 Ohm, more preferably still from 1.0 to 1.1 Ohm. As shown in each of the figures discussed above, the heating tracks of the resistive heater 16, 26 are provided directly on the outer surface of the tubular wall 14, 24. However, this is not essential. In further examples an electrically insulating layer (e.g. a film or coating) may be provided between the tubular walls 14, 24 and the resistive heaters 16, 26.

It will be appreciated that the examples of heating cups 12, 22 described above with reference to Figures 1 and 2 avoid relatively sharp projections that extend radially inwards towards the centre of the heating cups 12, 22. Although these radial projections can be used to grip or locate aerosol generating articles within a heating cup their use can result in significant local deformation of aerosol generating articles and poor distribution of heat with local “hot spots” or “hot zones” around the projections. In addition, insertion and removal of an article may require higher force. Instead, it will be observed from Figures 1 and 2 that the convex wall portions 14b, 24b and the planar wall portions 14a, 24a are located alternately around the circumference of the tubular wall 24. Moreover, the convex wall portions 14b, 24b and planar wall portions 14a, 24a are adjoined, extending continuously and alternately around the circumference of the tubular wall 14, 24. As such, it can be seen that each convex wall portion 14b, 24b is connected or merged to an adjacent planar wall portion 14a, 24a along each of its longitudinal edges. Equally each planar wall portion 14a. 14b is connected or merged to an adjacent convex wall portion 14b, 24b along each of its longitudinal edges. In other words, no further wall portions are provided between the convex wall portions 14b, 24b and the adjacent planar wall portions 14a, 24a.

Moreover, as can be seen most easily from Figure 2, the convex wall portions 14b, 24b are arcuate with cross sections that follow a circular perimeter, whereas the planar wall portions 14a, 24a extend between the adjacent, arcuate convex wall portions 14b, 24b and extend along chords of a circle defined by the convex wall portions 14b, 24b. Thus there are no radial projections or radial walls that extend from the tubular wall 14, 24 towards the centre of the cavity 28.

Although the above features are not essential, avoiding additional wall portions and any radial projections helps to ensure quick transfer of heat to aerosol generating articles within the heating cup 12, 22 and consistent heat distribution through the aerosol generating articles. As such, energy requirements are reduced.

Furthermore, as can be seen from both of Figures 1 and 2, the circumferential distribution and dimensions of the planar wall portions 14a, 24a and the convex wall portions 14b, 24b are similar. The planar wall portions 14a, 24a are provided around approximately half the circumference of the heating cup 12, 22 and the convex wall portions 14b, 24b are also are provided around approximately half the circumference of the heating cup 12, 22. In other words, approximately half of the tubular wall 14, 24 of the heating cups 12, 24 is defined by the planar wall portions 14a, 24a, whereas the remainder of the circumference is defined by the convex wall portions 14b, 24b. Indeed, in preferred embodiments of the invention, planar wall portions may in combination extend around 30 to 70% of the circumference of the heating cups, more preferably from 40 to 60% of the circumference, more preferably from 45 to 55% of the circumference. Similarly, in preferred embodiments, convex wall portions may extend around 30 to 70% of the circumference of the heating cups, more preferably from 40 to 60% of the circumference, more preferably from 45 to 55% of the circumference. These arrangements provide quick and consistent flow of heat from the heating assembly to its contents (e.g. an aerosol generating article received within the heating assembly) and thereby reduce energy requirements.

Furthermore, as discussed the heating cups 12, 22 shown in Figures 1 and 2 comprise planar wall portions 14a, 24a. As shown, these planar wall portions 14a, 24a are planar (i.e. flat) and extend in a tangential direction relative to the longitudinal axis of the heating cups 12, 22 such that the inner and outer surfaces of the tubular walls 14, 24 are planar. However, in further examples the planar wall portions may be replaced with substantially planar wall portions in which either of these surfaces of the tubular walls 14, 24 are slightly curved or comprise a surface relief.

Moreover, although Figures 1 and 2 show heating cups with three planar wall portions 14a, 24a and three convex wall portions 14b, 24b this is not essential. Further embodiments may comprise alternative numbers of planar and convex wall portions (e.g. four, five or more of the planar and/or convex wall portions).

Figures 3a and 3b schematically illustrate a system 100 in accordance with the invention. The system 100 comprises an aerosol generating device 110 and an aerosol generating article 120 that may be inserted into the aerosol generating device 110. Figure 3a shows the aerosol generating device 110 alone, whereas Figure 3b shows the full system in which the aerosol generating article 110 is received within the device 120. The aerosol generating device 110 comprises a heating assembly 111 comprising a heating cup 112 and a resistive heater 113. This heating assembly 111 may be in accordance with any of the examples discussed with reference to Figures 1a, 1b and 2 and may comprise of the preferable or optional features discussed above.

The aerosol generating device comprises an aersolisable substance - e.g. moist leaf tobacco. The heating assembly 111 is configured to heat the aerosol generating article 120 to generate an aerosol when the aerosol generating article 120 is inserted into the heating cup 112 (as shown in Figure 3b).

In addition, the aerosol generating device 110 comprises a controller 114, a battery 115 and a layer of thermal insulation 116 provided around the heating assembly 111. The resistive heater 113, controller 114 and battery 115 are in electrical communication as shown by the lines on Figure 3a. The battery 115 is configured to supply electrical power to the resistive heater 113. The controller 114 is configured to control the heat provided by the resistive heater 113 to the heating cup 112 so as to regulate the internal temperature of the heating cup 112 and therefore control the amount of aerosol formed using the system. The controller 114 may control this heat by varying the electrical power provided to the resistive heater 113 by the battery 115. This control may be empirical or based on pre-determined parameters. However, more preferably the control is based on measurements taken by thermistors or other temperature sensors that are configured to measure the temperature of the resistive heater 113, the heating cup 112 and/or the aerosol generating article 120 when received in the heating cup 112. For example, the controller 114 may use a closed-loop control process to maintain the temperature of the heating cup 112 at a predetermined level.

As shown in Figure 3b the aerosol generating article 120 is longer than the heating cup 112 and as such extends out from the aerosol generating device 110. A user may inhale aerosol from this free, distal end of the aerosol generating article 120. However, this is not essential and in further examples the aerosol generating article 120 may be entirely received in the heating cup 112, in which case the aerosol generating device may comprise a cap and/or mouthpiece configured to close the open end of the heating cup 112.