WO2023073206A1

WO2023073206A1 - A cartridge for a vapour generating device and a vapour generating device

Info

Publication number: WO2023073206A1
Application number: PCT/EP2022/080271
Authority: WO
Inventors: Jaakko MCEVOY; Christoph Lungenschmied
Original assignee: Jt International Sa
Priority date: 2021-10-29
Filing date: 2022-10-28
Publication date: 2023-05-04

Abstract

A vapour generating device (10) having a cartridge (14) for thermal connection to a base part (16) having at least one heat source (20), the cartridge having a liquid store (25) for containing a vapour generating liquid L and having a liquid outlet; a vaporization chamber in communication with the liquid store via the liquid outlet; and a deformable thermal interface membrane (50) configured, when the cartridge is thermally connected to the base part, to transfer heat from the heat source to effect vaporization of the vapour generating liquid, wherein the thermal interface membrane has a thickness < 100 ₁₁m and is comprised of at least two materials having different thermal conductivities.

Description

A CARTRIDGE FOR A VAPOUR GENERATING DEVICE AND A VAPOUR

GENERATING DEVICE

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 cartridge for an electronic cigarette and to an electronic cigarette incorporating the cartridge.

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 the use of a large aluminum disc as the heat transfer unit (HTU). Such a unit represents a large thermal bulk to heat up and produces large amounts of thermal spreading. The HTU is made of a high thermal conductivity material to improve efficiency but the high thermal conductivity is in all directions, so it spreads laterally as well. The HTU only contacts the wick over a small fraction of the entire HTU surface, which means a lot of the energy⁷ is spreading laterally and not being utilized. The heater may be embedded in ceramic for insulation, which is in contact with rough stamped aluminum discs. This can result in very poor thermal conductivity from the heater to e-liquid, with the greater the physical distance between the heater and the liquid the higher the lateral spread.

Thus, it is desirable to improve the efficiency of heat transfer through the device still further, in particular to minimize lateral thermal conduction losses and thermal hotspots to provide more uniform heating of the e-vapour and t-vapour fluids/solids.

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

According to a first aspect of the present disclosure, there is provided a cartridge for a vapour generating device, the cartridge being configured to thermically connect to a base part having at least one heat source, the cartridge comprising: a liquid store for containing a vapour generating liquid and having a liquid outlet; a vaporization chamber in communication with the liquid store via the liquid outlet; and and a thermal interface membrane configured, when the cartridge is thermically connected to the base part, to transfer heat from the heat source to effect vaporization of the vapour generating liquid, wherein the thermal interface membrane is comprised of at least two materials having different thermal conductivities, the membrane having a thickness < 100 pm.

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.

According to a second aspect of the present disclosure, there is provided a vapour generating device comprising: a base part having at least one heat source; and a cartridge according to the first aspect thermically connected to the base part via the interface membrane.

Preferably, 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 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 7pm . The electronic cigarette may be portable.

The interface membrane 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 and/or a metal foil window. The thin material of the membrane reduces the amount of lateral spread, thereby reducing thermal losses between the vaporization chamber and the heat source. It is preferable for the membrane material to have a Young’s Modulus of 0.1 to lOGP . This enables the membrane to deform when connecting the cartridge to the base part but maintain its integrity for heat transfer.

In a preferred embodiment of the present invention, the thermal interface membrane has at least two sections, each section being of a material having a different thermal conductivity, namely a high thermal conductive section having a first thermal conductivity and at least one low thermal conductive section having a second thermal conductivity lower than the first thermal conductivity.

The thermal interface membrane may comprise at least one high thermal conductive section made of material with a high thermal conductivity of >0.7 W/ K, preferably > 1 W/m.K, more preferably > lOW/m.K and especially > 100 W/m.K and at least one low thermal conductive section made of material with a low thermal conductivity of <1 W/m.K, preferably <0.7W/m.K. This aids rapid and even heating of the target vaporization chamber and avoids heat spread to non-target areas.

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 low thermal conductivity section of the membrane is preferably made of insulative material such as polymers, flexible ceramics (e.g. Min-K™), a polyimide such as Kapton and/or Nomex™.

The membrane sections of different thermal conductivity may be provided in a design to suit the intended application. Typically the thermal interface membrane is planar (being thin), and may comprise a heater interface surface (for example, a lower surface of the membrane when the cartridge is in a use orientation), configured to receive heat from a heat source in the base part. The membrane may further comprise a heating target interface surface (for example, an upper surface of the membrane when the cartridge is in the use orientation), configured to deliver heat to a heating target within the cartridge. The heater interface surface may comprise a first surface of a high thermal conductive section and the heating target interface surface may comprise a second surface of the high thermal conductive section. The first surface may be shaped to receive heat from a heating element within the base part. For example, the heating element may comprise a heater footprint, and the shape of the first surface may be selected to contain the heater footprint. In some examples, the first surface may be shaped to correspond to (i.e. to comprise the same shape as, or a substantially similar shape to) the heater footprint. This may ensure heat is transferred primarily to the high thermal conductivity section from the heat source and not to the adj cent low thermal conductivity section.

The second surface may be shaped to deliver heat to a vaporisation chamber within the cartridge. The vaporisation chamber may be defined by a chamber footprint. The shape of the second surface may be selected to contain the chamber footprint. In some examples, the second surface may be shaped to correspond to (i.e. to comprise the same shape as, or a substantially similar shape to) the chamber footprint. This may ensure heat is transferred efficiently from the high thermal conductivity section to the vaporisation chamber.

The or each low thermal conductive section may be laterally adjacent the high thermal conductivity region, and may laterally surround the high thermal conductive section on one or more sides. A low thermal conductive section may laterally enclose the high thermal conductive section so as to provide an insulating rim around the first surface and the second surface, whilst leaving both said surfaces exposed. Thus, preferably a section of the membrane with high thermal conductivity is located at the core of the membrane and the section with a low thermal conductivity is located around the core, i.e. cross-sectionally, the high thermal conductivity section is in the centre with an insulative material on opposing sides of the membrane.

The at least two sections of the membrane may be bonded together by any suitable technique, such as using either adhesives, thermal bonding, or any other method of bonding two dissimilar material sheets together that is known in the art.

The structure of the membrane comprising at least two materials may be configured to concentrate heat transfer in a preferred direction from the heat source, comprising the heating element in the base part, to the vaporization chamber in the cartridge, thereby reducing lateral thermal losses and/or hot spots. The sections may be chosen to provide even spread of heat in an in-plane and out-of-plane direction or concentrate spread in one or other of these planes dependent upon the configuration of the device. In one embodiment, the at least one high thermally conductive section comprises a material with isotropic properties to provide an even spread of heat in both an in-plane and an out-of- plane direction of the membrane.

Alternatively, the at least one high thermally conductive section may comprise a material with anisotropic properties, with lower thermal conductivity in an out-of-plane direction of the membrane compared to its thermal conductivity in an in-plane direction of the membrane or vice versa.

In one embodiment, the high thermal conductive section of the interface membrane is comprised of anisotropic materials, preferably graphene sheets having higher thermal conductivities (preferably > 1000 W/m.K, more preferably > 1500 W/m.K , especially around 1700 W/m.K) in the in-plane direction and lower thermal conductivities (preferably < 100 W/m.K , preferably < 50 W/m.K, especially around 20 W/m.K) in the out-of-plane direction. More preferably, this high thermal conductive section is provided at the core of the membrane and is surrounded by a low thermal conductive section in the form of a flexible thin insulator material. In such an arrangement, the high thermal conductive section may be shaped to deliver heat to the vaporisation chamber within the cartridge. This arrangement provides for rapid lateral thermal spreading, mitigating thermal hotspots and allows for complex heat transfer footprint geometries to be used between the heat source and the vaporization chamber, in particular wherein different geometries exist for the heat source and receiver.

In another embodiment, the high thermal conductive section of the interface membrane is comprised of anisotropic materials having a low thermal conductivity in the in-plane direction and a higher thermal conductivity in the out-of-plane direction. For example, carbon nanotube loaded polymer sheets may be provided in a high thermal conductive section at the core of the membrane to provide these properties, preferably being surrounded by a low thermal conductive section in the form of a flexible thin insulator material. Such an arrangement provides for transfer of thermal energy⁷ directly upwards into the vaporization chamber and is more suitable for matching or regular footprint geometries.

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 capillary⁷ action, wherein the pore size of the porous ceramic range from lOOnm to 10pm.

The ceramic wick or other fluid transfer medium may have a planar or non-planar surface which may face tow ards the interface membrane. The non-planar surface may comprise a plurality of recessed areas in a surface of the ceramic w ick and the recessed areas may face towards, and may be aligned with, sections of the interface membrane having high thermal conductivity. With such a non-planar surface for the ceramic wdck, it may be preferable to provide an interface membrane comprised of anisotropic materials surrounded by insulative materials. For example, if the footprint of the heat source, such as a heater, is regular, the interface membrane is preferably comprised of graphene sheets having higher thermal conductivities in the in-plane direction and lower thermal conductivities in the out-of-plane direction surrounded by insulative material. The high thermal conductive section of the membrane may be shaped to match the footprint of the heater and the footprint of the ceramic wick. Alternatively, if the footprint of the heater matches the footprint of the ceramic wick, for example if the heater has a specific resistive track or induction heater susceptor fabricated to match the footprint of the vaporization area, the high thermal conductive material of the interface membrane is preferably comprised of anisotropic materials having a low thermal conductivity in the in-plane direction and a higher thermal conductivity in the out-of-plane direction, such as carbon nanotube loaded polymer sheets. The interface membrane and/or the fluid transfer medium may further comprise at least one surface structure extending from their surface in the direction of the vaporization chamber, for example from an intended top membrane surface facing away from the base part of the device (e.g. the heating target interface surface) and/or from a bottom surface of the fluid transfer medium facing towards the base part of the device. These surface structures, for example in the form of protrusions or extensions are arranged to prevent a direct flow path from inlet to outlet in the vaporization channel.

Examples of suitable surface structures include fins, pin fins, wall mounted ribs, baffles, rods or any other suitable shapes. The structures may be regular or irregular. The structures may be arranged regularly or irregularly. Preferably, the structures are staggered across one or both of the fluid transfer medium and membrane surfaces. The structures may also be arced across the surface. For example, the structures on the surface of the interface membrane may be fabricated in an arced amplitude across the length of the membrane. Additionally, or alternatively, the structures extending from the fluid transfer medium may form an arced profile. The structures may be made of material such as porous ceramic, metal mesh and etched structures in Si__ microchannel.

The base part of the device may include a power supply unit, e.g. a battery, connected to the heat source. In operation, upon activating the electronic cigarette, the power supply unit electrically heats the heat source, such as a heating element, of the base part, which then provides its heat by conduction to a heat transfer unit. The heat transfer unit, in turn, provides the 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 heat source of the base part may comprise a protruding heater extending from the base part so that, in use, the heater extends into the chamber of the cartridge deforming the membrane around the heater.

The power supply unit, e.g. battery⁷, may be a DC voltage source. For example, the power supply unit may be aNickel-metal hydride battery⁷, a Nickel cadmium battery⁷, 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.

Brief Description of the Drawings

Figure 1 is a schematic cross-sectional view of an electronic cigarette comprising a base part and a cartridge according to one embodiment of the present disclosure;

Figure 2A is a schematic cross-sectional view of the base part shown in Figure 1;

Figure 2B is a schematic cross-sectional view of the cartridge shown in Figure 1; Figure 3 A is a schematic drawing illustrating heat transfer and losses with a single material membrane;

Figure 3B is a schematic drawing illustrating heat transfer and losses with a bi-material membrane;

Figure 4 is a schematic drawing illustrating heat transfer and losses with one type of interface membrane for use in a device according to the present invention;

Figure 5 is a schematic drawing illustrating heat transfer and losses with another type of interface membrane for use in a device according to the present invention;

Figure 6 is a schematic drawing of heat transfer and losses with yet another type of interface membrane for use in a device according to the present invention;

Figure 7A is a schematic perspective view⁷ of an example of heater unit for use in a device of the present invention;

Figure 7B is a schematic perspective view⁷ of an example of a ceramic wick for contacting a heater unit in a device of the present invention;

Figure 7C is a schematic cross section of an example of an interface membrane for placement between a heater unit and ceramic wick in a device according to an embodiment of the present invention;

Figure 7D is a schematic cross section of the interface membrane of Figure 7C in contact with the heater unit of Figure 7A;

Figure 7E is a schematic drawing of the interface membrane of Figure 7C betw een the heater unit of Figure 7A and the ceramic wick of Figure 7B;

Figure 8A is a schematic perspective view of another example of a heater unit for use in a device of the present invention;

Figure 8B is a schematic perspective view⁷ of an example of a ceramic wick for contacting the heater unit of Figure 8A;

Figure 8C is a schematic drawing of an example of an interface membrane for placement between a heater unit and ceramic wick in a device according to another embodiment of the present invention; Figure 8D is a schematic cross section illustrating heat transfer between the heater unit and ceramic wick of Figures 8A and 8B respectively via the interface membrane of Figure 8C;

Figures 9 A and 9B are schematic cross-sectional front views of a lower part of a cartridge according to an embodiment of the present invention, illustrating air flow through the vapour outlet channel;

Figures 10A to 10C are respectively schematic cross-sectional front, side and end views of a lower part of a cartridge according to another embodiment of the present invention;

Figures 11 A and 1 IB are schematic cross-sectional front views of a lower part of a cartridge according to another embodiment of the present invention, shown respectively with the interface membrane post and prior to connection with a heater unit;

Figures 12A and 12B are schematic cross-sectional front views of a lower part of a cartridge according to yet another embodiment of the present invention, shown respectively with the interface membrane post and prior to connection with a heater unit; and

Figure 13 is a schematic cross-sectional front view of a lower part of a cartridge according to yet another embodiment of the present invention.

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.

Referring initially to Figures 1 to 2B, there is shown one embodiment of a vapour generating device according to the present invention, 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 (see Fig. 2A) and a cartridge 14 (Fig. 2B) (also referred to as a capsule) thermically connectable to the base part 12 (See Fig.1). 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 powder supply unit in the form of a battery 18 connected to a heating element 20a located at a first end 16a of the housing 16. The heating element 20a 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 16a 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 battery 18 is configured for providing the heating element 20a with the necessary power for its operation, via contacts 24, allowing it to become heated to a required temperature.

The battery 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 20a. 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 compulsory⁷ 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 battery⁷ 18 to the heater unit 20, wherein the battery⁷ 18 acts as a divider between the heating element 20a and other sensitive components of the electronic cigarette 10.

Referring still to Figures 1 to 2B, in particular Figures 1 and 2B, the cartridge 14 comprises a cartridge housing having a proximal end 26 and a distal end 28. The proximal end 26 may constitute a mouthpiece end configured for being introduced directly into a user's mouth (not shown). In some embodiments, a mouthpiece may be fitted to the proximal end 26. 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 26 and the distal end 28, but is spaced from the distal end 28. In the illustrated embodiment, a vapour transfer channel 32 extends from an inlet 30 provided on one side of the base portion 26, across the base of the cartridge into which the heater unit 20 protrudes and up the side of the cartridge to an outlet 34 located centrally in the top part 26 of the cartridge. However, other configurations for the vapour outlet channel are possible. For example, the liquid store 30 may surround, and coextend with, the vapour transfer channel 32.

The base portion of the cartridge 14 is provided with a porous wick 38 (or other fluid transfer medium) which extends between the liquid store 30 and the vapour transfer channel 32.

Upon connection of the interfaces between 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 wick 38, thereby enabling heating of the liquid in the wick until the liquid is transformed into vapour.

Prior hereto heat transfer betw een the heater unit 20 and the liquid L has been inefficient 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 w⁷ell. The heater unit only contacts the wick over a small fraction of the heater surface, which means a lot of the energy⁷ is lost laterally, reducing the efficiency of the device. The heating element 20a is embedded in ceramic 40 within the top part 16a of the base part 16 for insulation but the physical distance between the heater and the liquid can result in significant lateral losses therebetween.

The present invention addresses this problem by the provision of a deformable bi-material thermal interface membrane 50 between the heater unit 20 and the porous w-ick 38. The membrane 50 is a flexible, thin membrane consisting of tw o or more materials w-ith vastly differing thermal conductivities but the membrane itself can be provided in many different configurations as described herein below⁷. The provision of a membrane with multiple sections of material having different thermal conductivities enables the membrane to be configured to ensure rapid and even heating of the target in an accurate and defined geometry⁷, reducing the amount of lateral thermal spreading (i.e. thermal losses).

Referring to Figure 3B, the membrane 50 is substantially planar (being thin), and has a high conductive section 102a formed of a first material having a high thermal conductivity⁷ and a pair of low⁷ thermal conductive sections 102b formed of a second material having a low thermal conductivity relative to the first material.

The membrane has a heater interface surface 51 configured to contact the heating element 20a in the base part 12, as well as a heating target interface surface 53 configured to deliver heat to a heating target within the cartridge, such as the vaporisation chamber beneath and/or within the wdck 38. In the example shown, a first (low er) surface 55 of the high thermal conductive section 102a is comprised within the heater interface surface and a second (upper) surface 57 of the high thermal conductive section is comprised within the heating target interface surface.

The first surface 55 is shaped to receive heat from the heating element 20a within the base part. The second surface 57 is shaped to deliver heat to the vaporisation chamber within the cartridge.

Each low thermal conductive section 102b is laterally adjacent the high thermal conductivity section 102a, so as to provide an insulating area adjacent the first surface 55 and the second surface 57, whilst leaving both said surfaces 55, 57 exposed.

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.

Figures 3 A and 3B illustrate schematically how lateral thermal spreading may be reduced by employing a bi-material membrane compared with a membrane comprised of a single material. Figure 3 A represents a membrane 100 comprised of a single conductive material. Heat does pass through the membrane to the other side as indicated by arrows A but there are significant lateral conduction losses, as indicated by the size of the arrows B in the lateral directions. In contrast, Figure 3B illustrates heat transfer through a bi-material membrane 102, having a central section 102a of a high thermal conductivity' material and opposing outer sections 102b of a low thermal conductivity⁷. Additional heat (arroyv A) is directed through the central section with less lateral conduction losses, again illustrated by the size of the arro vs B in Figure 3B. In this manner, a bi-material membrane may be interfaced betyveen the heater unit and the fluid transfer medium, such as a porous wick to direct heat into the vapour transfer channel and reduce lateral thermal losses.

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 (see Figure 2B). The protruding heater unit 20 deforms the membrane 50 when the cartridge is connected to the base part to provide a high contact pressure betyveen the membrane and heater (see Figure 1), lowering the interface thermal resistance. The materials of the membrane and their geometry may be selected to allow for spreading or concentration of the heat flow, depending on the desired application, thereby providing for customization of the heat flow path through the membrane to the vapour transfer channel 32.

The interface material membrane incorporated into the device of the present invention is of a thin flexible material, preferably being < 100pm thick and has at least one section of a high thermal conductivity, preferably being > 1 watt per meter-kelvin (W/m.K), more preferably > 10 W/m.K, especially > 100 W/m.K and at least one section of a low thermal conductivity, preferably < 1 W/m.K. Examples of suitable materials for the high thermal conductivity section include but are not limited to aluminium, flexible loaded polymers or graphene sheets. Ideally, the material has a low thermal expansion coefficient (a), preferably being less than that of the heater to ensure good contact throughout the heating cycle. Examples of suitable materials for the low thermal conductivity⁷ sections include, but are not limited to, flexible insulative materials such as polymers, flexible ceramics (e.g. Min-K™), Nomex™. In preferred embodiments, the bulk of the interface membrane material is comprised of the low thermal conductivity material with a section of the membrane, generally in the middle, made of the higher thermal conductivity material. The materials are bonded together using either adhesives, thermal bonding or any other method of bonding two dissimilar material sheets together as is known in the art.

Additionally, the membrane materials 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.

Figure 4 of the accompanying drawings illustrates in further detail one type of interface membrane 50 for providing in the cartridge shown in Figures 1 and 2B. The membrane has a high thermal conductive section comprising a material with a high thermal conductive and isotropic properties 52, such as a metal, and a low thermal conductive section comprising a flexible thin insulator material 54. The high thermal conductive section is located centrally in the thin membrane (i.e. at its core) and the low thermal conductive region is located surrounding the core. This configuration of membrane provides standard thermal spreading conditions and the degree of spreading is dictated by the thickness of the material, as indicated by the arrow-s in the figure. A thin material, less than 100pm thick, is desirable to reduce the amount of lateral thermal spreading. Another type of interface membrane 60 that may be incorporated into a cartridge according to the invention is shown in Figure 5. In this embodiment, a high thermal conductive section comprising anisotropic materials such as graphene sheets 62 having higher thermal conductivities (around 1700 W/m.K) in the in-plane direction and lower thermal conductivities (around 20 W/m.K) in the out-of-plane direction are provided at the core and are surrounded by a low⁷ thermal conductive section comprising a flexible thin insulator material 64. This arrangement provides for rapid lateral thermal spreading (as indicated by arrows in Fig. 5), mitigating thermal hotspots and allows for complex heat transfer footprint geometries to be used, as described in further detail below⁷.

Figures 7A to 7E of the accompanying drawings illustrate the type of vapour generating device that benefits from the type of interface membrane 60 discussed in relation to Figure 5. The heating unit 200 and heating target, such as the ceramic wick 380, have different footprints. For example, the heater unit 200 is of a standard rectangular geometry⁷, as shown in Figure 7A, and the ceramic wick 380 has a complex geometry⁷, as shoyvn in Figure 7B, the yvick having microchannels for vapour to escape once it vaporizes. The membrane 60 has a thermally conductive region comprised of a graphene sheet 62 which may be provided to correspond to the footprints of the heater and wick, for example having a rectangular central region 62a corresponding to the footprint of the heater unit yvith parallel strips 62b extending laterally yvhich correspond to the microchannels of the wick (see Figure 7C). The complex graphene sheet 62 is surrounded by an insulative material 64 yvhich is bonded thereto to form the interface membrane 60.

This type of interface membrane enables the heater unit 200 to be pushed up against the rectangular central region 62a of the thermally conductive region, as shown in Figure 7D. The complex footprint of the ceramic yvick 380 corresponds to the parallel strips 62b extending laterally from the central region, as shoyvn in Figure 7E with the insulative material 64 extending outwardly from the w⁷ick and the heater. In this manner, the conductive layer 62a, 62b spreads heat from the smaller footprint heater to the complex shape of the yvick (vaporisation zone), thus dissipating energy⁷ to where it is needed to heat the liquid.

Yet another type of interface membrane 70 for incorporation into a cartridge according to the invention is illustrated in Figure 6 of the accompanying figures. This configuration is particularly⁷ suitable for use when the heater geometry⁷ matches the geometry⁷ of the yvick/ vaporisation area. A high thermal conductive section comprising an anisotropic material 72 with lower thermal conductivity in the in-plane direction and higher thermal conductivity in the out of plane direction, such as carbon nanotube loaded polymer sheets, is provided at the core with a low thermal conductive section comprising a flexible thin insulator material 74 surrounding the core. Such an arrangement provides for transfer of thermal energy' directly upwards into the wick/vaporization area, as indicated by the arrow's in Figure 6. How ever, in other configurations, it may be preferable for the high thermal conductivity to be in plane, and low thermal conductivity to be out of plane, such as by using graphene sheets, so that localised hot spots can be avoided.

Figures 8A to 8D of the accompanying drawings illustrate a vapour generating device that w'ould benefit from the type of interface membrane 70 discussed in relation to Figure 6. The heater unit 200 is provided with a track geometry' 200t (see Fig. 8A) that is very' similar to the vaporization zone footprint provided by the ceramic wick 380 (see Fig. 8B). An interface membrane 70 as shoyvn in Figure 6 provides for heat transfer directly from the track 200t to the wick 380 so there is a need for high out of plane conductivity' but loyv in plane thermal conductivity. As illustrated by the arroyvs in Figure 8D, heat is passed directly from the heater unit 200 through the material of high thermal conductivity 72 to the yvick 380, thereby heating liquid to effect vaporization thereof yvhile minimizing lateral thermal losses. Thus, this type of membrane is particularly useful in relation to heaters yvhere a specific resistive track or induction heater susceptor can be fabricated to match the footprint of the vaporization area.

The different materials of the membrane may be provided in any shape and may vary' in thickness. Thus, it is to be appreciated that any geometry' of the thermally conductive and thermally insulative materials may be provided in the flexible interface membrane dependent upon the geometries and arrangements of the heater and the vaporization area, thereby providing for optimization of heat transfer betyveen the heater and the vaporization area. For example, yvhere the heating element has a heater footprint, the shape of the first, lo ver, surface of the high thermal conductive region may be selected to contain the heater footprint (e.g. it may comprise the same shape, or a substantially similar shape as the heater footprint such that the heater footprint is entirely received within the shape of the second surface, without significant overlap). Similarly, where the vaporisation chamber has a chamber footprint (e.g. a yvick footprint, as discussed above) the shape of the second, upper, surface of the high thermal conductive region may be selected to contain the chamber footprint (e.g. it may comprise the same shape, or a substantially similar shape as the chamber footprint such that the chamber footprint is entirely received within the shape of the second surface, without significant overlap).

Whatever the shape of the high thermal conductive section, one or more low thermal conductive sections may be located laterally adjacent the high thermal conductivity section, so as to laterally surround the high thermal conductive section on one or more sides. The low thermal conductive section may laterally enclose the high thermal conductive section so as to provide an insulating rim around the first surface and the second surface, whilst leaving both said surfaces exposed. For example the low thermal conductive section may generally form a ring or annulus around the high thermal conductive section when viewed in plane. It will be appreciated that the use of the word “ring” does not necessarily imply a circular shape - as discussed above, the sections of the membrane may have any shape, for example as dictated by the shape of the heater, vaporisation chamber/wick and heater unit.

Referring to Figures 9 A and 9B of the accompanying drawings, the air flow from the air inlet through the vaporization channel 32 between the porous wick 38 and the interface membrane 50 is illustrated. As can be seen in Figure 9B, the attachment of the base part of the device (not shown) to the cartridge pushes the membrane 50 into the vaporization channel 32. This results in 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) which aids evaporation of the liquid.

Prior devices typically control the pressure drop through the device using a small inlet port. In the present disclosure however, the air inlet port of the cartridge can be large so as to reduce the pressure drop at this section. The pressure drop (user draw pressure 500 Pa - 1500 Pa) can 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 in this area also results in reduced required temperature to achieve phase change.

Once the energy from the heat source is conducted through the membrane it is converted away by the air flow. To ensure efficient convection, vapor generation and transport different passive convective heat transfer enhancement structures can be used to increase out of plane mixing, impinging flow, flow fluctuations, surface area, surface roughness, wicking etc. These enhancement structures can be fabricated on either the internal side of the flexible interface membrane or as a part of the wick structure, or both, as illustrated in Figure 10A to 13. This increased surface area increases convective heat transfer. Furthermore, these structures may also aid wicking actions due to capillary action when extended into contact with the wick.

Thus, embodiments of the present invention may include the incorporation of surface structures into one or both of the interface membrane 50 and the fluid retention medium, such as the porous wick 38. Figures 10A to 10C of the accompanying drawings illustrate an embodiment wherein the porous wick 38 is provided with staggered pin fin arrays 38a extending from the low er surface thereof into the channel 32. The staggering of the fins 38a prevents a direct flow- path from air inlet to air outlet (see arrows in Figure 10C) which maximizes vapour concentration for heating, increasing heat transfer and vapour density at the outlet. In the illustrated embodiment, the fins are in the form of cylinders which may vary⁷ in length but it is to be appreciated that the surface structures could be any size and shape. The structures may be fabricated with varying heights to ensure even contact of structures to the wick over the stretched membrane.

Figures 11A to 12B illustrate embodiments wherein the interface membrane 50 is provided wdth surface structures 50a, 50b in the form of substantially parallel extension members. In Figures 11 A and 1 IB the extensions 50b nearer the centre of the membrane are shorter in height than those 50a tow ards either side of the membrane. This surface structuring fabricated in an arced amplitude across the length of the membrane results in a higher deflection amplitude and helps to maintain even contact of the structures wdth the wdck over the stretched membrane. The low⁷er surface 38s of the porous wdck 38 is straight. In contrast, in Figures 12A and 12B, instead of fabricating the arced surface by vary ing the height of the membrane extensions 50a, the extensions are a single height and the lower surface 38c of the porous wdck is arced. Again, the structures may be in line or staggered wdth respect to each other and may be of any size and shape.

The provision of surface structures on both the porous wdck 38 and interface membrane 50 provides for high rates of out of plane mixing, by impinging flow on w etted wdck and heated surface periodically, significantly increasing heat transfer from wall to fluid. An embodiment of such an arrangement is illustrated in Figure 13, wdiere the porous wick has pin fins 38a intermeshing wdth extensions 50a provided on the interface membrane 50. It is also important to ensure high contact pressure is maintained between the heater and the membrane when it is connected to the cartridge/capsule. This is achieved by ensuring that the interface membrane is taught across the opening of the cartridge. The membrane should also be thin but it advantageous for a smaller length of membrane to be provided rather than it spanning the length of the base of the unit.

It is to be appreciated that a rise in temperature during operation of the device will cause thermal expansion of the heater and the membrane. This will reduce the contact pressure if the thermal expansion coefficient of the membrane is higher than that of the heater material. Thermal grease or other thermal interface fillers may be used between the components to reduce air gaps and thermal resistance.

The present invention provides a cartridge and a vapour generating device incorporating the cartridge having an interface membrane that allows for more efficient heat transfer from the heater in a base part of the device to the cartridge/capsule for vaporisation of the liquid. The heat energy is concentrated towards the fluid transfer medium and lateral thermal losses and hot spots are reduced. Furthermore, the membrane and fluid transfer medium may include surface structures extending into the vaporization chamber to aid heat transfer further still.

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 is considered illustrative or exemplary' and not restrictive; the invention is not limited to the disclosed embodiments.

Claims

CLAIMS:

1. A cartridge for a vapour generating device, the cartridge being configured to thermically connect to a base part having at least one heat source, the cartridge comprising: a liquid store for containing a vapour generating liquid and having a liquid outlet; a vaporization chamber in communication with the liquid store via the liquid outlet; and a thermal interface membrane configured, when the cartridge is thermically connected to the base part, to transfer heat from the heat source to effect vaporization of the vapour generating liquid, wherein the thermal interface membrane is comprised of at least two materials having different thermal conductivities, the membrane having a thickness < 100 pm.

2. The cartridge as claimed in claim 1, wherein the thermal interface membrane has a heater interface surface configured to receive heat from the heat source in the base part and a heating target interface surface configured to deliver heat to a heating target within the cartridge, and wherein the thermal interface membrane comprises a high thermal conductive section having a first thermal conductivity and at least one low thermal conductive section having a second thermal conductivity lower than the first thermal conductivity, a first surface of the high thermal conductive section being comprised in the heater interface surface and a second surface of the high thermal conductive section being comprised in the heating target interface surface.

3. The cartridge as claimed in claim 1 or claim 2, wherein the thermal interface membrane comprises at least one high thermal conductive section made of material with a high thermal conductivity of >0.7 W/m.K and at least one low thermal conductive section made of material with a low thermal conductivity <0.7 W/m.K.

4. The cartridge as claimed in claim 3, wherein the high thermal conductive section has a thermal conductivity of>10W/m.K, preferably > 100 W/m.K.

5. The cartridge as claimed in claim 2 or claim 3 or claim 4 wherein the high thermal conductive section of the thermal interface membrane is selected from at least one of a metal, flexible loaded polymers and graphene sheets and the low thermal conductive section of the thermal interface membrane comprises an insulative material selected from at least one of polymers, flexible ceramics, a poly imide such as Kapton and/or Nomex™.

6. The cartridge as claimed in any one of claims 2 to 5, wherein the high thermal conductive section is located at the core of the thermal interface membrane and the low thermal conductive section surrounds the core.

7. The cartridge as claimed in any one of claims 2 to 6, wherein the or each low thermal conductive section is located laterally adjacent the high thermal conductive section.

8. The cartridge as claimed in claim 2, or any one of claims 3 to 7 as dependent on claim 2, wherein the low thermal conductive section laterally encloses the high thermal conductive section so as to provide an insulating rim around the first surface and the second surface, whilst leaving both said surfaces exposed.

9. The cartridge as claimed in any one of claims 2 to 8 wherein the at least one high thermal conductive section of the thermal interface membrane comprises a material with isotropic properties to provide an even spread of heat in both an in-plane and an out-of- plane direction of the thermal interface membrane.

10. The cartridge as claimed in any one of claims 2 to 8 wherein the at least one high thermal conductive section of the thermal interface membrane comprises a material with anisotropic properties, with lower thermal conductivity in an out-of-plane direction of the thermal interface membrane compared to its thermal conductivity in an in-plane direction of the thermal interface membrane or higher thermal conductivity in an in-plane direction of the thermal interface membrane compared to its thermal conductivity in an out-of-plane direction.

11. The cartridge as claimed in claim 10 wherein the at least one high thermal conductive section of the thermal interface membrane having anisotropic properties with lower thermal conductivity in an out-of-plane direction of the thermal interface membrane compared to its thermal conductivity in an in-plane direction of the thermal interface membrane comprises graphene sheets having in-plane thermal conductivities of >1500 W/m.K, preferably 1700 W/mK and out-of-plane thermal conductivities of <50 W/mK, preferably 20 W/m.K or the at least one high thermal conductive section of the thermal interface membrane having anisotropic properties with lower thermal conductivity⁷ in an in-plane direction of the thermal interface membrane compared to its thermal conductivity⁷ in an out-of-plane direction of the thermal interface membrane comprises carbon nanotube loaded sheets.

12. The cartridge as claimed in any one of the preceding claims, wherein a fluid transfer medium is provided in the cartridge between the liquid store and the vaporisation chamber for transferring liquid from the liquid store to the thermal interface membrane by capillary⁷ action.

13. The cartridge as claimed in claim 12, wherein at least one of the thermal interface membrane and the fluid transfer medium further comprises at least one surface structure extending from their surface in the direction of the vaporization chamber, being from an intended top membrane surface facing away from the base part of the device and/or from a bottom surface of the fluid transfer medium facing towards the base part of the device.

14. The cartridge as claimed in claim 13 wherein the surface structures are selected from at least one of fins, pin fins, wall mounted ribs, baffles and rods extending into the vaporization chamber.

15. The cartridge as claimed in claim 13 or claim 14 wherein the surface structures are staggered across one or both of the fluid retention and membrane surfaces.

16. The cartridge as claimed in any one of the preceding claims, wherein the cartridge has a vapour flow channel extending from an inlet, through the chamber to the outlet, the channel and/or chamber having at least one narrowing therein.

17. A vapour generating device comprising: a base part having at least one heat source and a power supply and a cartridge according to any one of the preceding claims thermically connected to the base part via the thermal interface membrane.