DEVICE WITH CARTRIDGE ATTACHMENT

Technical Field

The present disclosure relates generally to a vapour generating device, such as an electronic cigarette. Embodiments of the present disclosure relate in particular to a reusable vapour generating device and to such a device with a cartridge attachment.

Technical Background

Electronic cigarettes are an alternative to conventional cigarettes. Instead of generating a combustion smoke, they vaporize a liquid which can be inhaled by a user. The liquid typically comprises an aerosol-forming substance, such as glycerine or propylene glycol, that creates the vapour when heated. Other common substances in the liquid are nicotine and various flavourings.

The electronic cigarette is a hand-held inhaler system, typically comprising a mouthpiece section, a liquid store and a power supply unit. Vaporization is achieved by a vaporizer or heater unit which typically comprises a heating element in the form of a heating coil and a fluid transfer element such as a wick. Vaporization occurs when the heater heats the liquid in the wick until the liquid is transformed into vapour.

Conventional cigarette smoke comprises nicotine as well as a multitude of other chemical compounds generated as the products of partial combustion and/or pyrolysis of the plant material. Electronic cigarettes on the other hand deliver primarily an aerosolized version of an initial starting e-liquid composition comprising nicotine and various food safe substances such as propylene glycol and glycerine, etc., but are also efficient in delivering a desired nicotine dose to the user. Electronic cigarettes need to deliver a satisfying amount of vapour for an optimum user experience whilst at the same time maximizing energy efficiency.

WO2017/179043 discloses an electronic cigarette comprising a disposable cartridge and a reusable base part. The cartridge has a simplified structure which is achieved by keeping the main heating element in the re-usable base part, while the cartridge is provided with a heat transfer unit. The heat transfer unit is configured to transfer heat from the heating element to the proximity of liquid in the cartridge to produce a vapour for inhalation by a user. The Applicant’s co-pending Application Publication No. WO 2021/028395 further improves the energy efficiency of an electronic cigarette so that less heat is conveyed to the liquid store in the cartridge but instead is focused on a sorption member that has the liquid to be vaporised absorbed therein. A concentration of heat is present in the sorption member in contact zones due to conduction of heat from the heat transfer unit to the sorption member in the contact zones, thereby maximizing heat input to the sorption member in the contact zones whilst heat transfer to other component parts of the cartridge and/or electronic cigarette, and in particular, the liquid store, is minimized.

A further problem associated with prior art electronic cigarettes is obtaining and maintaining a satisfactory thermal contact between the reusable base part that contains the heat source and the fluid transfer medium, such as a ceramic wick in the disposable cartridge. Typically, the distance between the heat source and vaporization chamber with the fluid transfer medium results in substantial thermal losses.

Thus, it is desirable to improve the efficiency of heat transfer through the device still further, in particular to minimize thermal losses betw een the two parts of the device.

It is an object of the present disclosure to provide an improved vapour generating device, in particular an e-cigarette device, and disposable cartridges for use with said device that aim to overcome, or at least alleviate, the above-mentioned drawbacks.

Summary of the Disclosure

A first aspect of the present invention provides a vapour generating device comprising a reusable base part and a disposable cartridge containing a vapour generating liquid, the base part comprising: a housing releasably connectable to a part of the cartridge and a heating element for heating of the vapour generating liquid when the cartridge is thermically connected to the base part, wherein the heating element at least partially protrudes beyond a perimeter of the housing; and the cartridge comprising: a liquid store for containing the vapour generating liquid; a liquid outlet, a vaporization chamber in communication w ith the liquid store via the liquid outlet, and an interface membrane having at least one region of high thermal conductivity; w-herein the protruding part of the heating element of the base part protrudes into the vaporization chamber to deform the membrane in the at least one region of high thermal conductivity to provide thermal contact between the cartridge and the base part. In a preferred embodiment of the first aspect of the present invention, the base part includes a support member coupled to the heating element and at least one of the heating element and support member is configured to move outwardly from the perimeter of the housing when the heating element is activated by a power supply.

The interface membrane may comprise an insulating region adjacent (e.g. laterally surrounding) the region of high thermal conductivity.

The heating element may comprise a resistive track, optionally protected by a thin ceramic or other coating or may comprise a susceptor which is inductively heated by an induction coil positioned in the base part of the device. The track or susceptor may be made of any suitable material, such as ceramic heater track materials known in the art including, but not limited to, aluminium, brass, copper, tungsten, nichrome, FeCrAl, CuNi, Ag, palladium or mild steel.

Preferably, an exposed top contact surface of the protruding portion of the heating element defines a heater footprint. The heater footprint may have a footprint area, which is preferably smaller than an area of a target to be heated. A shape of the heater footprint may correspond to a shape of the target to be heated, and the shape of the target to be heated may contain the heater footprint. For example, where the heating element is generally rectangular in footprint and the exposed top surface has dimensions of W^HH, where subscript h denotes the heater dimensions, preferably Wh< W _t & Hh< H _t , where subscript t denotes the target to be heated dimensions. Generally, the target to be heated corresponds to the region of high thermal conductivity in the interface membrane and the dimensions Wh ^x Hh of the heating element are lower than W _t ^x H _t dimensions of the target to be heated.

The heating element may be provided with any surface geometry including circular, elliptical or other geometric forms. For example, a circular geometry for the heating element preferably has a radius lower than the radius of the heating target.

In a preferred embodiment, the heating element has an overall curved or domed geometry, where the edges of the heating element are chamfered or filleted to increase the surface area, preferably by a factor of 1.05 to 1.15.

The heating element may comprise a curved surface configured to contact the interface membrane, the curved surface preferably having a radius of curvature in the range 3-10mm. The curved surface may comprise the heater footprint, and may be of any shape when viewed in plan view, e.g. circular, rectangular, square or irregular in shape. A curved surface allows even thermal contact between the heating element and the interface membrane, reducing hot spots and/or areas of high contact pressure.

An edge surface may be provided surrounding the curved surface, the edge surface having a different curvature to the curved surface. The curvature of the edge surface may be greater than the curvature of the curved surface. Such relatively steeply curved edges may further reduce contact pressure. The edge surface may have a shape complementary to the curved surface when viewed in plan view. For example, if the curved surface is substantially circular, the edge surface may be annular so as to surround the curved surface.

The heating element may comprise a ceramic heating element. The ceramic heating element may have a heater body, a top surface comprising the curved surface and a lower surface opposed to the top surface and separated from the top surface by a side wall. The lower surface may comprise a cavity. The cavity may provide thermal insulation between the heating element and other components of the base unit. The cavity may reduce the thermal bulk of the ceramic heater. In such an arrangement the ceramic heating element may not require a heater support. The ceramic heater body may have a thickness which is at least 0.2mm and which does not exceed 0.4mm. The ceramic heater body may be generally cylindrical.

Preferably, the support member (if present) is configured to move outwardly from the perimeter of the housing when the heating element is activated by the power supply. More preferably, this movement causes thermal contact between the heating element and the vaporization chamber. More preferably still, the movement occurs when the heating element is at or above a threshold temperature.

Preferably, the support member is configured to be deformed or to extend when the temperature of the heating element is at or above the threshold temperature whereby the heating element can be moved to contact the vaporization chamber.

In one embodiment, the support member is configured to be elastically deformed when the temperature of the heating element is at or above the threshold temperature and to be substantially reset to its original shape when the temperature of the heating element is at a temperature below the threshold temperature. For example, the support member may be comprised of or substantially consist of a shape memory alloy (SMA) and the threshold temperature corresponds to the transformation temperature of the SMA.

The support member may be configured to extend in one dimension w hen the temperature of the heating element is at or above the threshold temperature and retract to be substantially reset to its original length w-hen the temperature of the heating element is below the threshold temperature. The movement may be such as to effect retraction of the heating element from the vaporization chamber.

The support member may comprise or substantially consist of a material that exhibits a thermostatic behaviour.

The interface membrane that in the cartridge preferably has a thickness of <100 pm and is preferably deformable, more preferably comprising a flexible material such as a laminate of filled silicone rubber/PEEK, a poly imide such as Kapton, mica, polybenzimidazole (PBI) and/or a metal foil window. It is preferable for the membrane material to have a Young’s Modulus of 0.1 to lOGPa. This enables the membrane to deform when connecting the cartridge to the base part but maintain its integrity for heat transfer.

The thermal interface membrane may comprise at least one high thermal conductive section made of material with a high thermal conductivity ⁷ of > 0.7 W/m.K, preferably > 1 W/m.K, more preferably > 10 W/m.K and especially > 100 W/m.K.

The high thermal conductivity section of membrane may be made of a material of a suitable thermal conductivity, for example a metal such as aluminium, flexible loaded polymer such as carbon nanotube loaded polymers, and/or graphene sheets.

The cartridge preferably has a vapour flow channel extending from an inlet, through the chamber to the outlet. Preferably at least one narrowing is provided in the channel and/or the chamber.

It is preferable for a fluid transfer medium to be provided in the cartridge between the liquid store and the vaporisation chamber for absorbing liquid transferred to the vaporization chamber via the liquid outlet. The fluid transfer medium can be made of any material or a combination of materials being able to perform sorption and/or absorption of another material, and can be made, for example, of one or more of the following materials: fibre, glass, aluminium, cotton, ceramic, cellulose, glass fibre wick, stainless steel mesh, polyethylene (PE), polypropylene, polyethylene terephthalate (PET), poly(cyclohexanedimethylene terephthalate) (PCT), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), and BAREX®, etc..

In a preferred embodiment, the fluid transfer medium of the cartridge comprises a porous ceramic wick positioned adjacent to an opening of the liquid store and arranged to hold and transfer vapour generating liquid from the liquid store to the thermal interface membrane by capillary action, wherein the pore size of the porous ceramic range from lOOnm to 10pm.

Preferably, movement of the heating element towards the vaporization chamber causes contact of the heating element with the fluid transfer medium, such as the ceramic wick, thereby providing good thermal contact. More preferably, the interface membrane extends between the heating element and the fluid transfer medium.

In one embodiment, the support member for the heating element and the fluid transfer medium may comprise or substantially consist of a magnetic material such that, when an attractive magnetic force is applied between the support member and the fluid transfer medium contact between heating element and the fluid transfer medium is established. This may occur when the temperature of the heating element is at or above the threshold temperature. The threshold temperature may be below the Curie temperature of the heating element, and the attractive magnetic force betw een the support element and the fluid transfer medium is reduced or eliminated at or below the Curie temperature of the heating element such that the heating element is extended to the fluid transfer medium.

The power supply unit of the base part may be, e.g. a battery, connected to the heat element. In operation, upon activating the electronic cigarette, the power supply unit electrically heats the heat element, of the base part, which then transfers it its heat to the fluid retention medium resulting in vaporization of the liquid absorbed therein. As this process is continuous, liquid from the liquid store is continuously absorbed by the retention medium. Vapour created during the above process is transferred from the vaporization chamber via the vapour flow channel in the cartridge so that it can be inhaled via the outlet by a user of the device.

The power supply unit, e.g. battery, may be a DC voltage source. For example, the power supply unit may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium -Cobalt, a Lithium -Iron-Phosphate, a Lithium-Ion or a Lithium -Polymer battery. The base part may further comprise a processor associated with electrical components of the electronic cigarette, including the battery.

The cartridge may further comprise: a cartridge housing at least partially including the liquid store and the vaporization chamber, and the vapour flow channel extending along the cartridge housing and in fluid communication with the vaporization chamber. The cartridge housing may have a proximal end configured as a mouthpiece end which is in fluid communication with the vaporization chamber via the vapour flow channel and a distal end associated with the base part. The mouthpiece end may be configured for providing the vaporized liquid to the user.

In one embodiment, the liquid store may be provided in the main body of the cartridge with the vapour flow channel extending from an inlet at the base and one side of the cartridge, along the base of the cartridge to the vaporization chamber and up one side of the cartridge to the outlet located centrally at the mouthpiece end. Alternatively, the liquid store may be disposed around the vapour outlet channel.

The cartridge housing may be made of one or more of the following materials: aluminium, poly ether ether ketone (PEEK), polyimides, such as Kapton®, polyethylene terephthalate (PET), polyethylene (PE), high-density polyethylene (HOPE), polypropylene (PP), polystyrene (PS), fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyoxymethylene (POM), polybutylene terephthalate (PBT), Acrylonitrile butadiene styrene (ABS), Polycarbonates (PC), epoxy resins, polyurethane resins and vinyl resins. According to a second aspect of the present disclosure, there is provided a reusable vapour generation device for attachment to a disposable cartridge containing a vapour generating liquid, the vapour generation device comprising: a housing releasably connectable to a part of the cartridge; a heating element for heating of the vapour generating liquid when the cartridge is thermically connected to the base part; a support member coupled to the heating element; and a power supply to activate the heating element; wherein the heating element at least partially protrudes beyond a perimeter of the housing and wherein at least one of the heating element and support member is configured to move outwardly from the perimeter of the housing when the heating element is activated by the power supply.

A third aspect of the present invention provides a vapour generating device according to the second aspect thermically connected to a cartridge, the cartridge comprising a liquid store for containing the vapour generating liquid; a liquid outlet and a vaporization chamber in communication with the liquid store via the liquid outlet, wherein the heating element at least partially protrudes beyond a perimeter of the housing into the vaporization chamber and wherein at least one of the heating element and support member is configured to move outwardly from the perimeter of the housing towards the vaporization chamber when the heating element is activated by the power supply.

In a preferred embodiment of the present invention, the cartridge includes an interface membrane having at least one region of high thermal conductivity extending at least partially across the area of the cartridge that contacts the vapour generating device. Preferably, the protruding heating element contacts the interface membrane in the region of high thermal conductivity upon connection of the device with the cartridge.

The second and third aspects of the invention may be combined with any of the features discussed above in connection w ith the first aspect of the invention.

Brief Description of the Drawings

Figure 1 A is a schematic cross-sectional front view of an electronic cigarette comprising a base part and a cartridge part according to one embodiment of the present disclosure, shown with parts disconnected;

Figure IB is a schematic cross-sectional side view- of the electronic cigarette show-n in Figure 1A; Figure 2A is a perspective cross-sectional view of a cartridge and an upper part of the base part according to an embodiment of the present disclosure, shown with parts disconnected;

Figure 2B is a perspective cross-sectional view of the cartridge and upper part of the base part of Figure 2A, shown with parts connected;

Figure 2C is a schematic cross-sectional view of the whole electronic cigarette shown in the Figures 2A and 2B, shown with parts disconnected;

Figure 3A is a cut-away side view of a cartridge connected to a base part (not shown) in accordance with an embodiment of the present invention;

Figure 3B is an enlarged view of the interface area of the cartridge shown in Figure 3A;

Figure 3C is a structural cross-sectional front view of the cartridge shown in Figure 3A connected to the base part (not visible);

Figure 3D is a perspective view of the exterior of the cartridge of Figure 3 A (base part omitted);

Figure 3E is an isometric view of the cartridge shown in Figure 3D, illustrating its connection to the upper part of the base part (partially shown);

Figure 4 is a schematic drawing illustrating one design of heater unit for an electronic cigarette according to an embodiment of the present invention;

Figure 5 is a schematic drawing illustrating another design of heater unit for an electronic cigarette according to the invention;

Figure 6 is a schematic cross-sectional view of a base part of an electronic cigarette;

Figure 7 is a schematic cross-sectional view of an alternative base part of an electronic cigarette;

Figure 8 illustrates heating elements for use in the base parts shown in Figures 6 and 7;

Figure 9A shows a cross sectional view of a ceramic heating element;

Figure 9B is a plan view of the ceramic heating element of Figure 9A; and

Figure 10 a schematic cross-sectional view of a base part of an electronic cigarette including the ceramic heating element shown in Figures 9A and 9B.

Detailed Description of Embodiments

Embodiments of the present disclosure will now be described by way of example only and with reference to the accompanying drawings and in which like features are denoted with the same reference numerals.

The present invention concerns the provision of improved thermal contact for heat transfer between a heat source within a reusable base part of a vapour generating device and a disposable cartridge or capsule containing a liquid to be heated by the heat source to cause vaporization of the liquid for inhalation. Particularly not exclusively, the vapour generating device comprises an electronic cigarette.

As used herein, the term “electronic cigarette” may include an electronic cigarette configured to deliver an aerosol or vapour to a user, including an aerosol for smoking. An aerosol for smoking may refer to an aerosol with particle sizes of 0.5 to 10 pm. The particle size may be less than 10 or 7 pm. The electronic cigarette may be portable.

In general terms, a vapour is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour can be condensed to a liquid by increasing its pressure without reducing the temperature, whereas an aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. It should, however, be noted that the terms ‘aerosol’ and ‘vapour’ may be used interchangeably in this specification, particularly with regard to the form of the inhalable medium that is generated for inhalation by a user.

Referring initially to Figures 1A and IB of the accompanying drawings, one embodiment of a vapour generating device according to the present invention is illustrated. The device is in the form of an electronic cigarette 10 for vaporizing a liquid L. The electronic cigarette 10 can be used as a substitute for a conventional cigarette. The electronic cigarette 10 comprises a base part 12 and a cartridge 14 (also referred to herein as a capsule) thermically connectable to the base part 12. The base part 12 is thus the main body part of the electronic cigarette and is preferably re-usable.

The base part 12 comprises a housing 16 accommodating therein a power supply unit in the form of a battety 18 connected to a heating element located at a first end of the housing 16. The heating element is provided in a rigid protruding heater unit 20 that protrudes out of the base part for partial receipt within the cartridge or capsule 14. The first end of the housing 16 has an interface configured for matching a corresponding interface of the cartridge 14 and comprises a connector for mechanically coupling the cartridge 14 to the base part. The batter ' 18 is configured for providing the heating element with the necessary power for its operation, via contacts 24, allowing it to become heated to a required temperature.

The batter}' 18 is also connected to a controller 22, enabling the required power supply for its operation and the controller 22 is operationally connected to the heating element. In the illustrated example, the controller is located between the battery 18 and the heater unit 20 but it is to be appreciated that this arrangement is not compulsory and other arrangements of the components within the base part 12 are entirely within the scope of the present disclosure, such as the controller being located on an opposite side of the battery 18 to the heater unit 20, wherein the battery 18 acts as a divider between the heating element and other sensitive components of the electronic cigarette 10.

Referring still to Figures 1 A and IB, the disposable capsule or cartridge 14 comprises a housing 12 having a proximal end and a distal end. The proximal end may constitute a mouthpiece end configured for being introduced directly into a user's mouth. In some embodiments, a mouthpiece may be fitted to the proximal end. However, it is also possible to configure the electronic cigarette 10 with a separate mouthpiece portion, releasably connectable to the base part and whereby the cartridge 14 is enclosed inside the electronic cigarette 10. The cartridge 14 comprises a base portion and a liquid storage portion 25, where the liquid storage portion comprises a liquid store configured for containing therein the liquid L to be vaporized. The liquid L may comprise an aerosol-forming substance such as propylene glycol and/or glycerol and may contain other substances such as nicotine and acids. The liquid L may also comprise flavourings such as e.g. tobacco, menthol or fruit flavour. The liquid store 25 may extend between the proximal end and the distal end, but is spaced from the distal end. In the illustrated embodiment, a vapour transfer channel 32 extends from an inlet 30 provided on one side of the base of the housing, across the base of the cartridge into w hich the heater unit 20 protrudes and up the side of the cartridge to an outlet 34 located centrally in the top part of the cartridge. However, other configurations for the vapour outlet channel are possible. For example, the liquid store 30 may surround, and coextend w-ith, the vapour transfer channel 32.

The base portion of the cartridge 14 is also provided w-ith a porous w-ick 38 (or other fluid transfer medium) which extends between the liquid store 30 and the vapour transfer channel 32. Upon connection of the interfaces betw een the cartridge 14 and the base part 12 of the device, the heater unit 20 protrudes into the vapour transfer channel immediately below the base of the porous w-ick 38, thereby enabling heating of the liquid in the w-ick until the liquid is transformed into vapour.

This design of an electronic cigarette having a reusable base part to the device and a disposable capsule or cartridge is environmentally friendly, cost effective and enables the user to vary the e- liquid dispensed through the device. However, having the heating element in the main body (base part) of the device with the e-liquid contained w ithin a separate cartridge does result in added thermal resistance between the two. This may be remedied by bringing the fluid into contact with the heating element through the use of fluidic connections between the cartridge and the base part (mass transfer) but this may be prone to leakage and also has higher manufacturing costs. Therefore, the present invention is concerned w-ith improving the efficiency of heat transfer betw een the tw o parts of the device, i.e. transferring heat from the base part to the liquid contained in the cartridge without fluid transfer betw een the tw o. This can be problematic due to the large thermal bulk of the heater unit producing thermal spreading. The high thermal conductivity material of the heater improves efficiency but this high thermal conductivity is in all directions, resulting in undesirable lateral spread as w-ell. The heater unit only contacts the w'ick over a small fraction of the heater surface, which means a lot of the energy is lost laterally, reducing the efficiency of the device. The heating element is embedded in ceramic 40 within the base part 16 for insulation but the physical distance between the heater and the liquid results in a poor thermal connection.

The present invention provides a heater unit 20 in the base part of the device that is arranged such that the surface 20a of the heater unit 20 protrudes out beyond the boundary of the surrounding parts (see, for example, Figure 1 A). This ensures that the heater unit 20 makes good thermal contact with the cartridge/capsule when the two are fitted together and that the heater unit 20 applies a fixed amount of deformation and protrusion into the lower part of the capsule in the vaporization chamber. In the embodiment show n, the ceramic insulator 40 is domed to provide the protrusion, w ith the heating element located across the upper surface thereof. In a preferred embodiment, the protruding heating element is configured to be moved tow ards (for example to contact) the fluid transfer medium (ceramic w-ick) of the cartridge upon activation, preferably upon reaching a predetermined threshold temperature, with the heating element being coupled to a support member that is heated by the heating element. This improves the thermal contact between the heater unit and the cartridge with the heating element and/or support applying a fixed amount of deformation and protrusion into the cartridge.

Additionally, the base of the capsule 14 that contacts the heater unit 20 is provided w-ith a deformable thermal interface membrane 50. The membrane is flexible and thin, ideally less than 100pm thick, to reduce the amount of lateral thermal spreading and preferably at least a part of the membrane that contacts the heater surface has a relatively high thermal conductivity, such as polyphenylene sulfide (PPS), PGS graphite or other loaded polymers having a conductivity of >0.7 W/m.K, preferably >1 W/m.K (w-atts per metre kelvin). Ideally this material is recyclable, low- cost and of a similar sort of material as the rest of the capsule casing, so as to reduce recycling issues (i.e. silicone elastomers). Non-metallic flexible films such as graphite sheets are particularly suitable due to their thin structure (50pm) and having an out-of-plane high thermal conductivity of around 10-30 W/m.K. Thin metal membranes may also be used.

To minimize lateral conduction losses in the system the deformable interface membrane 50 should be small, and not extend the entire length and depth of the capsule/cartridge base. To increase the thermal diffusivity of the membrane the thermal mass and specific heat of the membrane should be low-, while the conductivity' should be high. It is to be appreciated that the interface membrane 50 should be tightly pulled across the interface of the cartridge 14 that is connectable to the base part 12. The protruding heater unit 20 deforms the membrane 50 when the cartridge is connected to the base part to provide a high contact pressure between the membrane and heater unit, lowering the interface thermal resistance. Fabrication of the heating element to be slightly raised ensures it is the first point of contact with the flexible interface membrane. When the device is activated, the heat generated is forced into the capsule by insulating the heater unit surroundings. A thermal interface material such as thermal grease can be used to minimise the contact resistance between heater and membrane further, if required but should be avoided if possible.

Additionally, the membrane material should have an acceptable Young’s Modulus so as not to plastically deform during use, preferably being 0.1 - lOGPa. The actual value required will depend upon the amount of displacement of the membrane and the initial film tightness. Plastic deformation of the film will result in reduced contact pressures due to the lower internal stresses now available in the membrane per unit of deformation (strain). Too low of an initial induced stress w ill also have the same end result of poor contact pressure (high thermal resistance). As the temperature of the membrane rises w ith use, the contact pressure is expected to drop due to the change of material properties and dimensions (i.e. Young’s modulus/yield strength is a function of temperature, and drops with increased temperature).

Figures 2A and 2C of the accompanying drawings illustrate another embodiment of a device according to the present invention. As can be seen in Figure 2A, the heater unit 200 includes heating element 202 in the form of a susceptor 202 positioned over the raised upper surface of the unit 200 which is inductively heated by a coil (not shown) in the device. Alternatively, a resistive track may be used in place of the susceptor, preferably being protected by a thin ceramic or other coating. A susceptor may be preferable as this is rugged and cheap and therefore may be replaced easily. The susceptor may made from, for example, aluminium, brass, copper or mild steel. The capsule 14 is provided with liquid in the cavity 25 and a ceramic w-ick 38 extends between the liquid and an interface membrane 50. Connecting the two parts together (by pushing in the direction of arrow-s A and B in Figure 2A) causes the heater 200, 202 to deform membrane 50 to provide close contact between the heating element 202, membrane and the vaporization chamber immediately below the wick 38, with the rest of the housing 12 of the capsule fitting closely around the top of the base part 16 (see Figure 2B). In a preferred embodiment, activation of the resistive track or susceptor causes heating of the element and the surrounding ceramic support w hich, once a threshold temperature has been reached, moves the heating element into contact with the fluid transfer medium 38 in the cartridge. More particularly, the heating element 202 located in the device according to an embodiment of the present invention should be able to deflect or extend outward in a desired direction when activated/heated. This effect can be achieved through use of shape memory alloys, bimetallic strips, thermal buckling or other mechanical means. In the case of thermal buckling actuation, the heating element is made of a material with a high thermal expansion coefficient, such as stainless steels, magnesium alloys or aluminium alloys (11 - 18 pstrain/K), while the material surrounding it has a significantly lower coefficient of thermal expansion, such as ceramics (2 - 10 pstrain/K). As the temperature of the element rises it attempts to expand but is restricted from doing this by the surrounding material and eventually buckles.

Figures 6 and 7 show two alternative examples of a base part 12 of an electronic cigarette which includes a heater unit 200 that comprises a heating element 202 in the form of a susceptor. As in the case of the base unit shown in Figures 1A and IB, the base part 12 includes a power supply unit in the form of a battery (not shown) and a controller 22. The base part 12 additionally includes an induction coil 204, shown as a transverse coil in Figure 6 and as a helical coil in Figure 7. As will be seen from the Figures, a transverse coil is a substantially planar coil which may be placed adjacent (e.g. below, as shown or to one side of) a susceptor to be heated. Conversely, a helical coil is located around a susceptor to be heated. A susceptor heating element 202 requires no electrical contacts and instead is heated by the induction of eddy currents / hysteresis losses within the susceptor when the induction coil 204 is energised by the controller 22 via electrical contacts 224.

As discussed above, the susceptor may be any material commonly used for the purpose (steel, ferritic metals, aluminium, copper, nickel, etc). The susceptor can be oriented in any direction or any angle in the device. However, each susceptor material has an optimal displacement distance from an energising coil. This distance can be accurately controlled when the susceptor is placed in the same device as the coil, as opposed to being included in a cartridge part of the device. Thus the susceptor may be located within the base part 12 at a distance relative to the coil 204 that maximises its coupling to the coil. In the case of a planar coil, the susceptor heating element 202 may be oriented in a plane that is parallel to, but spaced from, the coil 204. A central axis 206 of the susceptor may be aligned with a central axis 208 of the coil. In the case of a helical coil, the susceptor heating element 202 may be oriented such that the central axis 206 of the susceptor is aligned with the central axis 208 of the coil.

The susceptor may have any shape, but as noted above, a substantially planar susceptor can be advantageous to improve coupling to a transverse coil. Figure 8 shows some non-limiting examples of cross-sectional shapes suitable for use in a substantially planar susceptor. These include a domed shape 210, a rectangular shape 212 and a rectangular shape with chamfered comers 214. Domed, chamfered or otherwise curved heating elements may be useful in minimising hotspots and improving thermal coupling when used in conjunction with a thin interface membrane 50 of the type discussed above. Furthermore, susceptors which are small in volume, such as planar susceptors, may lower heat up time.

A susceptor of the type discussed may be located on or mounted in a thermal insulator 40. Alternatively, a susceptor may be deposited/fabricated onto an insulator 40 as a thin metal layer. In that case, the insulator may be formed in the desired final shape (e.g. domed) in order to define the shape of the susceptor layer.

Figures 9A and 9B show a further alternative heater unit 300. The heater unit 300 comprises a resistive heating element 302 having a ceramic heater body 304, a top surface 306 and a lower surface 308 opposed to the top surface and separated from the top surface by one or more side walls 310. The top surface 306 is configured to contact the interface membrane 50 (not shown) in the same manner as the top surface of the heater units 20, 200, discussed above. Like those heater units, the top surface 306 may comprise a curved or domed surface. The curved surface may extend across substantially the entire contact surface of the heater unit (i.e. across the entire heater footprint), and preferably has a radius of curvature in the range 3-10mm, centred on the longitudinal axis 206 of the heater body. In the specific example shown the top surface has a radius of curvature of approximately 5mm. The curved surface may be of any shape, and in the example shown is circular when viewed in plan view, such that the heater body 304 is generally cylindrical. The ceramic heater body shown in Figures 9A and 9B has a thickness which is at least 0.2mm and which does not exceed 0.4mm.

The heating element 300 additionally comprises an edge surface 312 surrounding the curved surface. The edge surface has a different curvature to the curved surface, and smooths the transition betw een the top surface 306 and the side w all 310. The curvature of the edge surface is, in the example shown, greater than the curvature of the curved surface.

As in the case of the heating elements discussed above, the heating element 300 may be located on or mounted in an insulating material 40, as show-n in Figure 10. The lower surface 308 of the heating element 300 may additionally include a cavity 314. The cavity 314 may provide further thermal insulation between the heating element 300 and other components of the base unit, such as the controller 22 and pow-er source 18. The cavity 314 may further reduce the thermal bulk of the ceramic heater. It will be appreciated that in this arrangement the ceramic heating element may not require a heater support, although a heater support may be provided if required (particularly in an embodiment where the heater support is movable, as discussed below-).

Figures 3 A to 3E show- an embodiment of the present invention illustrating the positioning of the protruding heater unit 20, 200, 300 in the capsule 14 in further detail. As discussed above, the heater unit may comprise a heating element, for example a resistive heating element or a susceptor, or a ceramic heater body, on an upper surface of a support member. The heater unit 20, 200, 300 protrudes into the base of the capsule 14 to be in close thermal contact with the lower surface of the ceramic wick 14. However, when the capsule is connected to the base part it may not initially have good thermal contact with the heater. The deformable membrane 50 covers the heating element and support member, w-ith a material of high conductivity 50e being provided in the region of the membrane that contacts the heating element and the ceramic w-ick, w hereas the remainder of the membrane may comprise an insulative material. Once the heating element is activated, the support and heating element heat up and once a threshold temperature is reached, the heating element deflects or extends outwardly (as schematically indicated by region 20e in Figure 3B) to contact the ceramic w ick 38 thereby providing good thermal contact allowing efficient vaporization of the liquid. Air flows from the air inlet 30 through the vaporization channel 32 between the porous wick 38 and the interface membrane 50 as illustrated in the arrow s in Figure 3C and 3E. The attachment of the base part of the device to the cartridge pushes the membrane 50 into the vaporization channel 32 w-hich results in an increase in velocity of the vapour and a decrease in pressure through this region (due to the change in volume of the air channel between sides of the domed membrane) w hich aids evaporation of the liquid.

The cartridge 14 is constructed so that an air flow- path exists between the deformable membrane 50 and the porous wdck 38. In a preferred embodiment, the undeformed airway path should have a hydraulic diameter betw een 1.5 - 7.5mm and a length that extends 70-90% across the wddth of the capsule. The air inlet port 30 of the capsule should be large so as to reduce the pressure drop at this section. The pressure drop (user draw- pressure 500 Pa - 1500 Pa) should instead be controlled at the vaporization chamber/ heater interface area. By designing the incurred pressure drop in this area, more complex heat transfer enhancement methods may be utilised. The pressure reduction being provided in this area also results in reduced required temperature to achieve phase change.

The act of the heater unit deforming when heated and protruding into the capsule also results in a pressure drop across the heating element which can be tuned to result in a desired level of pressure drop to match that of optimal draw- pressures (500 Pa - 1500 Pa). A flexible air valve/flap can be used at the air inlet to prevent liquid outflow-.

Figures 4 and 5 of the accompanying drawings illustrate further embodiments for the base part incorporating a protruding heater unit 300, 400 according to the present invention. In Figure 4, the heating element 300 is provided on a protruding block 302 having a flat upper surface. The exposed top contact surface of the heater should have smaller dimensions Wh x Hh relative to the heating target (such as the area of the interface membrane that has high thermal conductivity) such that Wh < W _t and Hh < H _t In a preferred embodiment, the heating element 402 has a curved or domed geometry, as show n in Figure 5 w herein the edges of the upper surface of the heating element 400 are chamfered or filleted. This increases the surface area of the heating element, preferably by a factor of > 1, especially by a factor of 1.05 to 1.15.

It is to be appreciated that the heating element may be provided in any geometric form so long as it protrudes from the surrounding base part (see, for example, Figure 2C that clearly illustrates how the heating element protrudes from the rest of the device). For example, the element may be circular or elliptical, in which case the radius of the heater should be lower than the radius of the target area (rn < r _t ).

Various alternative embodiments of the base part and cartridge may be provided according to the present invention. It is preferred for the heater unit to comprise a deformable heater, being either the heating element alone or, more preferably the heating element and its support member forming the heater unit. Additionally, the cartridge is provided with a high thermal conductivity membrane. Optionally, passive heat transfer enhancement may be provided in relation to the fluid transfer medium (e.g. ceramic wick), membrane and/or the vaporization chamber or channel to control airflow, pressure drop, heat transfer and vapor mass transport.

It is preferred that the device of the present invention has a support member configured to deform or extend when the temperature of the heating element is at or above a threshold temperature w-hereby the heating element can be moved to contact the heat transfer element. The support member may be configured to be elastically deformed when the temperature of the heating element is at or above the threshold temperature and to be substantially reset to its original shape w hen the temperature of the heating element is at a temperature below- the threshold temperature. The support member may be configured to be extended in one dimension w-hen the temperature of the heating element is at or above the threshold temperature and to be substantially reset to its original length by being shortened when the temperature of the heating element is below- the threshold temperature, thereby retracting the heating element from the fluid transfer medium. For example, the support member may comprise or substantially consist of a shape memory alloy (SMA) and the threshold temperature corresponds to the transformation temperature of the SMA. The support member may also comprise or substantially consist of a material that exhibits a thermostatic behaviour.

In one embodiment, the support member may be made from a magnetic material. The fluid transfer medium of the cartridge may also include a magnetic material, w herein an attractive magnetic force between the support member and the fluid transfer medium may cause enhanced contact between the heating element and the fluid transfer medium to be established w hen the temperature of the heating element is at or above the threshold temperature. For example, when the threshold temperature is below- the Curie temperature of the heating element, and the attractive magnetic force between the support member and the fluid transfer medium is reduced or eliminated at or below- the Curie temperature of the heating element, such that the heating element extends to the fluid transfer medium above the Curie temperature.

The present invention provides a cartridge and a vapour generating device incorporating the cartridge, the cartridge having an interface membrane for contacting a protruding heating element upon connection of the two parts to allow for more efficient heat transfer from the heater in the base part of the device to the cartridge/capsule for vaporisation of the liquid. Thermal transfer is increased further still by incorporating a heating element and support wherein one or both are configured to deform or extend towards the fluid transfer medium in the cartridge when the heating element reaches a predetermined threshold temperature. The skilled person will realize that the present invention by no means is limited to the described exemplary embodiments. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Moreover, the expression "comprising" does not exclude other elements or steps. Other non-limiting expressions include that "a" or "an" does not exclude a plurality and that a single unit may fulfil the functions of several means. Any reference signs in the claims should not be construed as limiting the scope. Finally, while the invention has been illustrated in detail in the drawings and in the foregoing description, such illustration and description are considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.