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Title:
AEROSOL GENERATING DEVICE WITH PIERCING ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2017/207416
Kind Code:
A1
Abstract:
There is provided an electrically heated aerosol-generating device (100) for use with a consumable cartridge (200) comprising a storage portion (202) containing an aerosol-forming substrate and having a fluid permeable internal surface (204) surrounding an open ended passage (208) extending through the cartridge. The device includes a main housing (102) having a cavity (108) for receiving a consumable cartridge, a closure body (110) engageable with the main housing to enclose the cartridge in the cavity,and a heater assembly (300) for heating the cartridge. The heater assembly includes an elongate piercing assembly (302) arranged to extend into the open-ended passage of the cartridge and one or more electric heaters (400) fixed thereto. The piercing assembly has a first hollow shaft portion (304) connected to the main housing and a second hollow shaft portion (324) connected to the closure body. The first and second hollow shaft portions (304, 324) have first and second piercing surfaces(308, 328) at their distal ends for breaking through first and second frangible seals (210, 212) across first and second ends of the open ended passage when the cartridge is enclosed in the cavity. The first and second hollow shaft portions are arranged to extend along the same longitudinal axis and are sized to meet at a junction (330) such that the elongate piercing assembly extends along the entire length of the cavity when the closure body is engaged with the main housing.

Inventors:
BATISTA, Rui Nuno (Avenue Alois Hugonnet 10, 1110 Morges, 1110, CH)
MANCA, Laurent (Chemin de la Butte 6, 1036 Sullens, 1036, CH)
Application Number:
EP2017/062720
Publication Date:
December 07, 2017
Filing Date:
May 25, 2017
Export Citation:
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Assignee:
PHILIP MORRIS PRODUCTS S.A. (Quai Jeanrenaud 3, Neuchâtel, CH-2000, CH)
International Classes:
A61M15/06; A24F47/00; A61M11/04; A61M15/00; H05B3/06; H05B3/58
Domestic Patent References:
WO2015197627A12015-12-30
WO2009132793A12009-11-05
Foreign References:
US20100006113A12010-01-14
Attorney, Agent or Firm:
PALMER, Benjamin (Reddie & Grose LLP, The White Chapel Building10 Whitechapel High Street, London Greater London E1 8QS, E1 8QS, GB)
Download PDF:
Claims:
CLAIMS:

1. An electrically heated aerosol-generating device for use with a consumable cartridge comprising a storage portion containing an aerosol-forming substrate, the storage portion having a fluid permeable internal surface surrounding an open ended passage extending through the cartridge, the device comprising:

a main housing having a cavity for receiving a consumable cartridge;

a closure body engageable with the main housing to enclose the cartridge in the cavity; and

a heater assembly for heating the cartridge, the heater assembly comprising:

an elongate piercing assembly arranged to extend into the open-ended passage of the cartridge and defining an internal airflow passage forming part of an airflow pathway through the device; and

one or more electric heaters fixed to the elongate piercing assembly, the one or more electric heaters each having at least one heating element for heating the aerosol forming substrate when the cartridge is enclosed in the cavity,

wherein the elongate piercing assembly comprises a first hollow shaft portion connected to the main housing and having a first piercing surface at its distal end for breaking through a first frangible seal across a first end of the open ended passage when the cartridge is inserted into the cavity, and a second hollow shaft portion connected to the closure body and having a second piercing surface at its distal end for breaking through a second frangible seal across a second end of the open ended passage when the closure body is engaged with the main housing, wherein the first and second hollow shaft portions are arranged to extend along the same longitudinal axis when the closure body is engaged with the main housing, and wherein the first and second hollow shaft portions are sized to meet at a junction such that the elongate piercing assembly extends along the entire length of the cavity when the closure body is engaged with the main housing. 2. An electrically heated aerosol-generating device according to claim 1 , wherein the distal ends of the first and second hollow shaft portions are co-operatively shaped such that a seal is formed around the junction.

3. An electrically heated aerosol-generating device according to claim 2, wherein the distal end of one of the first and second hollow shaft portions has an inwardly tapering outer surface and the distal end end of the other one of the first and second hollow shaft portions has an outwardly tapering inner surface, the inner and outer surfaces being shaped such that the inwardly tapering outer surface fits within the outwardly tapering inner surface to form the seal when the closure body is engaged with the main housing.

4. An electrically heated aerosol-generating device according to any of the preceding claims, wherein the closure body forms a mouthpiece portion by which air can be drawn through the airflow pathway of the aerosol generating device.

5. An electrically heated aerosol-generating device according to any of the preceding claims, wherein the first and second hollow shaft portion are electrically conductive and arranged to connect the one or more electric heaters to an electrical power supply.

6. An electrically heated aerosol-generating device according to any of the preceding claims, wherein the heater assembly comprises a plurality of electric heaters which are fixed to and spaced along the length of the elongate piercing assembly.

7. An electrically heated aerosol-generating device according to claim 6, wherein the plurality of electric heaters comprises one or more electric heaters fixed to the first hollow shaft portion and one or more electric heaters fixed to the second hollow shaft portion. 8. An electrically heated aerosol-generating system according to claim 6 or claim 7, wherein the plurality of electric heaters each extend across the internal airflow passage trasverse to the longitudinal direction of the elongate piercing assembly.

9. An electrically heated aerosol-generating system according to any one of claims 6 to 8, wherein one or both of the first and second hollow shaft portions comprises a plurality of apertures in which the plurality of electric heaters are held, the plurality of electric heaters being in fluid communication with the storage portion of a cartridge received in the cavity through the plurality of apertures. 10. An electrically heated aerosol-generating system comprising an electrically heated aerosol-generating device according to any one of claims 1 to 9, and a consumable cartridge comprising a storage portion containing an aerosol forming substrate, the storage portion having a fluid permeable internal surface surrounding an open-ended passage extending through the cartridge, wherein the cartridge is enclosed in the cavity such that the elongate piercing assembly extends into the open-ended passage of the cartridge.

Description:
AEROSOL GENERATING DEVICE WITH PIERCING ASSEMBLY

The present invention relates to an aerosol-generating device for use with a consumable cartridge. In particular, the present invention relates to an electrically heated aerosol-generating device for use with a consumable cartridge having an internal passage and containing an aerosol-forming substrate. The disclosure also relates to consumable cartridges for use with aerosol-generating devices, to electrically heated aerosol-generating systems comprising an electrically heated aerosol-generating device and a consumable cartridge, and to kits for an electrically heated aerosol-generating system comprising an electrically heated aerosol- generating device and a plurality of consumable cartridges.

Electrically heated smoking systems that are handheld and operate by heating an aerosol- forming substrate in an aerosol-generating article, or cartridge, are known in the art. For example, WO2009/132793 describes an electrically heated smoking system comprising a shell and a replaceable mouthpiece. The shell comprises an electric power supply and electric circuitry. The mouthpiece comprises a liquid storage portion and a capillary wick having a first end and a second end. The first end of the wick extends into the liquid storage portion for contact with liquid therein. The mouthpiece also comprises a heating element for heating the second end of the capillary wick, an air outlet, and an aerosol-forming chamber between the second end of the capillary wick and the air outlet. The heating element is typically a coil of wire that is wound around the wick. When the shell and mouthpiece are engaged, the heating element is in electrical connection with the power supply via the circuitry, and a flow route for air is defined from at least one air inlet to the air outlet via the aerosol-forming chamber. In use, liquid is transferred from the liquid storage portion towards the heating element by capillary action in the wick. Liquid at the second end of the capillary wick is vaporised by the heating element. The supersaturated vapour created, is mixed and carried in the air-flow from the at least one air inlet to the aerosol-forming chamber. In the aerosol-forming chamber, the vapour condenses to form an aerosol, which is carried towards the air outlet into the mouth of a user.

According to a first aspect of the present invention, there is provided an electrically heated aerosol-generating device for use with a consumable cartridge comprising a storage portion containing an aerosol-forming substrate, the storage portion having a fluid permeable internal surface surrounding an open ended passage extending through the cartridge, the device comprising: a main housing having a cavity for receiving a consumable cartridge; a closure body engageable with the main housing to enclose the cartridge in the cavity; and a heater assembly for heating the cartridge, the heater assembly comprising: an elongate piercing assembly arranged to extend into the open-ended passage of the cartridge and defining an internal airflow passage forming part of an airflow pathway through the device; and one or more electric heaters fixed to the elongate piercing assembly, the one or more electric heaters each having at least one heating element for heating the aerosol forming substrate when the cartridge is enclosed in the cavity, wherein the elongate piercing assembly comprises a first hollow shaft portion connected to the main housing and having a first piercing surface at its distal end for breaking through a first frangible seal across a first end of the open ended passage when the cartridge is inserted into the cavity, and a second hollow shaft portion connected to the closure body and having a second piercing surface at its distal end for breaking through a second frangible seal across a second end of the open ended passage when the closure body is engaged with the main housing, wherein the first and second hollow shaft portions are arranged to extend along the same longitudinal axis when the closure body is engaged with the main housing, and wherein the first and second hollow shaft portions are sized to meet at a junction such that the elongate piercing assembly extends along the entire length of the cavity when the closure body is engaged with the main housing.

Advantageously, having a two-part piercing assembly may allow the seals at either ends of a cartridge to be more easily broken by the user. Without wishing to be bound by theory, it is believed that by breaking the seals inwardly, the seals are prevented from moving away from the hollow shaft portions and the stresses exerted by the first and second piercing surfaces on the seals are higher, causing the seals to break more easily. Additionally, by connecting one of the hollow shaft portions to the closure body, it may be possible to prevent the seal at the downstream end of the cartridge from being broken until the closure body is placed over the main housing. This may reduce the risk of liquid leakage during insertion of the cartridge. Further, by providing the electric heaters as part of the device, cartridges for use with the device may be simplified, less expensive and more robust than cartridges which include an electric heater. Accordingly, reducing the cost of cartridges, even if it requires a more expensive device, can lead to significant cost savings for both manufacturers and consumers.

The heater assembly comprises an elongate piercing assembly to which one or more electric heaters is fixed. Thus, the elongate piercing assembly doubles as a mount for the one or more electric heaters and as a piercing member. This may allow the elongate piercing assembly to pierce the seal at the end of a cartridge conveniently and easily during insertion of the cartridge into the device. To facilitate piercing of the seal, the distal ends of the first and second hollow shaft portions at which the first and second piercing surfaces are located preferably have a cross-sectional area that is smaller than the cross-sectional area of the region of the hollow shaft member immediately proximal of the piercing surface. Preferably, the cross- sectional areas of the first and second hollow shaft portions narrow towards a tapered tip at their respective distal ends. The cross-sectional areas of the first and second hollow shaft portions may narrow towards a point at their respective distal ends.

The elongate piercing assembly has an internal airflow passage forming part of an airflow pathway through the device. With this arrangement, the elongate piercing assembly may provide a support for the electric heaters as well as providing an airflow channel. This may allow for a device which is compact and may facilitate cost-effective high volume manufacturing. Having an airflow passage within the first and second hollow shaft portions may help to minimise heat loss from the device and may allow the housing of the device to be easily maintained at a temperature which is comfortable to hold. Furthermore, vaporised aerosol-forming substrate in the air flow through the hollow shaft portions can begin to cool within the airflow passage to form an aerosol, allowing the overall length of the device to be reduced.

The frangible seals form barriers across the ends of the cartridge prior to insertion into the cavity of the device. The frangible seals may be made from any suitable material or materials, for example from a film, such as a metal film, preferably an aluminium film.

In electrically heated aerosol-generating devices of the invention, the first and second hollow shaft portions are arranged to extend along the same longitudinal axis when the closure body is engaged with the main housing.

The first and second hollow shaft portions are also sized to meet at a junction such that the elongate piercing assembly extends along the entire length of the cavity when the closure body is engaged with the main housing.

The distal ends of the first and second hollow shaft portions are preferably co-operatively shaped such that a seal is formed around the junction. With this arrangement, air flow may be substantially confined to the internal airflow passage through the elongate piercing assembly, rather than passing into the storage portion of the cartridge, thereby facilitating the delivery of a consistent aerosol. In such embodiments, one or both of the hollow shaft portions may be fluid permeable. This may allow liquid from the storage portion, or aerosol formed from the aerosol- forming substrate in the storage portion to enter the internal airflow passage of the elongate piercing assembly. For example, one or both of the first and second hollow shaft portions may comprise one or more apertures. One or more electric heaters may be held in the one or more apertures. In such embodiments, the one or more electric heaters may be in fluid communication with the storage portion of a cartridge received in the cavity through the one or more apertures.

The distal ends of the first and second hollow shaft portions may have any suitable, co- operative piercing shape. Preferably, the distal end of one of the first and second hollow shaft portions has an inwardly tapering outer surface and the distal end end of the other one of the first and second hollow shaft portions has an outwardly tapering inner surface, the inner and outer surfaces being shaped such that the inwardly tapering outer surface fits within the outwardly tapering inner surface to form the seal when the closure body is engaged with the main housing. This may allow the first and second hollow shaft portions to be mated easily. For example, the distal end of the first hollow shaft portion may have an inwardly tapering outer surface and the distal end end of the second hollow shaft portion may have an outwardly tapering inner surface, the inner and outer surfaces being shaped such that the inwardly tapering outer surface fits within the outwardly tapering inner surface to form the seal when the closure body is engaged with the main housing.

The closure body may function simply as a lid for closing the cavity. Preferably, the closure body forms a mouthpiece portion by which air can be drawn through the airflow pathway of the aerosol generating device. The mouthpiece portion may have an outlet through which aerosol generated by the device can be drawn into a user's mouth. As used herein, the term "mouthpiece portion" means a portion of the device that is configured to be placed in a user's mouth in order to directly inhale an aerosol generated by the system, the aerosol being conveyed to the user's mouth through the mouthpiece.

The first and second hollow shaft portions are preferably electrically conductive. In such examples, the first and second hollow shaft portions may be arranged to connect the one or more electric heaters to an electrical power supply. For example, the first and second hollow shaft portions may be formed from an electrically conductive material, such as metal. In other examples, the first and second hollow shaft portions may be formed from an electrically insulative substrate, such as a polymer substrate, and may further comprise one or more electrical conductors attached to the substrate for connecting the electric heaters to an electrical power source. For example, the first and second hollow shaft portions may comprise an electrically insulative substrate on which electrical conductors are applied for example by deposition, printing, or by laminating with the substrate as a laminated foil. The laminate foil may then be shaped or folded to form the first and second hollow shaft portions.

The heater assembly may comprise a single electric heater comprising at least one heating element for heating the aerosol-forming substrate of a cartridge received in the cavity. Preferably, the heater assembly comprises a plurality of electric heaters which are fixed to and spaced along the length of the elongate piercing assembly.

Advantageously, this arrangement may allow for more even heating of the aerosol- forming substrate in the cartridge relative to devices in which only one electric heater is provided or in which a plurality of electric heaters are provided but which are not spaced along the length of the elongate piercing assembly. It may also allow the device to heat parts of a cartridge to which would not be heated by devices having only a single heater, enabling more of the aerosol- forming substrate in each cartridge to be vaporised, reducing waste. Additionally, when used with cartridges having a plurality of different aerosol-forming substrates stored separately, the plurality of longitudinally spaced apart electric heaters allow separate heating of the different aerosol-forming substrates to produce an aerosol with particularly desirable characteristics.

Where the heater assembly comprises a plurality of electric heaters, all of the electric heaters may be fixed to one of the first and second hollow shaft portions. In some examples, the plurality of electric heaters comprises one or more electric heaters fixed to the first hollow shaft portion and one or more electric heaters fixed to the second hollow shaft portion. The plurality of electric heaters may be evenly or unevenly divided between the first and second hollow shaft portions. For example, one of the first and second hollow shaft portions may comprise a single electric heater, with the remaining electric heaters being fixed to the other of the first and second hollow shaft portions.

One or more electric heaters may extend across the airflow passage transverse to the longitudinal axis of the elongate piercing assembly. In such embodiments, the one or more electric heaters may span the airflow passage. Advantageously, this may place the electric heater directly in the path of being drawn through the device when in use. This may allow vaporised aerosol-forming substrate to be more readily entrained into air flowing through the device to form an aerosol. It may also allow the electric heater to be cooled by the air flowing through the device, reducing the risk of overheating. By extending across the airflow passage, the electric heaters may help to mix the vaporise aerosol-forming substrate with the air flow through the hollow shaft portion, for example by creating turbulence in the air flow. This may result in a more homogenous aerosol when compared to examples in which no electric heaters extend across the airflow passage.

Where the heater assembly comprises a plurality of electric heaters, the plurality of electric heaters may each extend across the internal airflow passage trasverse to the longitudinal direction of the elongate piercing assembly. In such embodiments, the plurality of electric heaters may each span the airflow passage.

Where one or more of the electric heaters extend across the airflow passage, the longitudinal axis of one or more of the electric heaters may be perpendicular to the longitudinal axis of the hollow shaft portion. One or more of the electric heaters extending across the airflow passage may be arranged such that its longitudinal axis is oblique to the longitudinal axis of the hollow shaft portion.

Where the plurality of electric heaters extend across the airflow passage transverse to the longitudinal axis of the hollow shaft portion, one or more of the plurality of electric heaters may extend across the airflow passage such that its longitudinal axis is rotated about the longitudinal axis of the elongate piercing assembly relative to the longitudinal axis of at least one other of the electric heaters. That is, when longitudinal axes of the electric heaters are projected onto a plane extending perpendicularly to the longitudinal axis of the elongate piercing assembly, the longitudinal axis of one or more of the plurality of electric heaters extends across the airflow passage at an angle to the longitudinal axis of at least one other of the electric heaters. With this arrangement, the electric heaters may more readily intercept air flowing through the device relative to arrangements in which the electric heaters are aligned about the longitudinal axis of the elongate piercing assembly. It also means that at least one of the electric heaters may be in fluid communication with the storage portion of a cartridge at a position which is offset around the circumference of the elongate piercing assembly from one or more of the remaining electric heaters. This may allow the device to more uniformly consume aerosol-forming substrate stored in a cartridge, reducing waste, relative to arrangements in which the electric heaters are aligned about the longitudinal axis of the hollow shaft portion. Additionally, in the event that liquid aerosol-forming substrate leaks from one of the electric heaters during use, by having one or more of the electric heaters extending at a different angle, the liquid may be more readily intercepted and absorbed into one of the adjacent electric heaters and may thus reduce liquid leakage from the device.

Preferably, one or both of the first and second hollow shaft portions comprises a plurality of apertures in which the plurality of electric heaters are held, the plurality of electric heaters being in fluid communication with the storage portion of a cartridge received in the cavity through the plurality of apertures.

The apertures may be formed in the first or second hollow shaft portion after the respective hollow shaft portion has been formed, for example by punching, drilling, milling, erosion, electro erosion, cutting, or laser cutting. The apertures may be formed integrally with the first or second hollow shaft portion at the time of forming the hollow shaft portion, for example by casting or moulding the hollow shaft portion with the apertures or by a deposition process, such as electrodeposition.

As used herein, the term "aerosol-generating device" refers to a device that interacts with an aerosol-generating article, such as a consumable cartridge, to generate an aerosol.

Preferably, the aerosol-generating device is portable. The aerosol-generating device may have a size comparable to a conventional cigar or cigarette. The aerosol-generating device may have a total length between approximately 30 mm and approximately 150 mm. The aerosol-generating device may have an external diameter between approximately 5 mm and approximately 30 mm.

The heater assembly may be fixed to, or integral with, the main housing and the closure body of the device. In other embodiments, the heater assembly may be removably fastened to one or both of the main housing and the closure body. This may allow the heater assembly to be at least partially removed from the device, for example for maintenance or cleaning or to enable replacement of the heater assembly. The heater assembly may be removable coupled to the main housing or the closure body by one or more electrical and mechanical connection means.

The heater assembly comprises one or more electric heaters. For example, the heater assembly may comprise one, two, three, four, five, six or more electric heaters fixed to the elongate piercing assembly. Where the heater assembly comprises one or more electric heaters, the electric heaters may be spaced along the length of the elongate piercing assembly. Each electric heater comprises at least one heating element. Each electric heater may comprise more than one heating element, for example two, or three, or four, or five, or six or more heating elements. The heating element or heating elements may be arranged appropriately so as to most effectively heat the aerosol-forming substrate of a cartridge inserted into the cavity of the main housing.

Each heating element may be a coil of electrically resistive wire. The heating element may be formed by stamping or etching a sheet blank that can be subsequently wrapped around a wick. Preferably, the heating element is a coil of electrically resistive wire. The pitch of the coil is preferably between 0.5 and 1.5 mm, and most preferably approximately 1 .5mm. The pitch of the coil means the spacing between adjacent turns of the coil. The coil may advantageously comprise fewer than six turns, and preferably has fewer than five turns. The electrically resistive wire advantageously has a diameter of between 0.10 and 0.15mm, and preferably of approximately 0.125mm. The electrically resistive wire is preferably formed of 904 or 301 stainless steel. Examples of other suitable metals include titanium, zirconium, tantalum and metals from the platinum group. Examples of other suitable metal alloys include, Constantan, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal®, iron-aluminium based alloys and iron-manganese-aluminium based alloys. Timetal® is a registered trade mark of Titanium Metals Corporation, 1999 Broadway Suite 4300, Denver Colorado. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required. The heating element may comprise a metallic etched foil insulated between two layers of an inert material. In that case, the inert material may comprise Kapton®, all-polyimide or mica foil. Kapton® is a registered trade mark of E.I. du Pont de Nemours and Company, 1007 Market Street, Wilmington, Delaware 19898, United States of America. The heating element may also comprise a metal foil, e.g., an aluminium foil, which is provided in the form of a ribbon.

The at least one heating element may operate by resistive heating. In other words the material and dimensions of the heating element may be chosen so that when a particular current is passed through the heating element the temperature of the heating element is raised to a desired temperature. The current through the heating element may be applied by conduction from a battery or may be induced in the heating element by the application of a variable magnetic field around the heating element.

The at least one heating element may comprise an inductive heating element, such that, where the device forms part of an aerosol-generating system consisting of the aerosol generating device and a removable aerosol-generating article, no electrical contacts are formed between the article and the device. The device may comprise an inductor coil and a power supply configured to provide high frequency oscillating current to the inductor coil. The article may comprise a susceptor element positioned to heat the aerosol-forming substrate. As used herein, a high frequency oscillating current means an oscillating current having a frequency of between 500 kHz and 10 MHz.

Electric heaters according to the invention may comprise a capillary body. The at least one heating element may be arranged on an outer surface of the capillary body, for example as a coil. The capillary body may comprise any suitable material or combination of materials which is able to convey a liquid aerosol-forming substrate along its length. The capillary body may be formed from a porous material, but this need not be the case. The capillary body may be formed from a material having a fibrous or spongy structure. The capillary body preferably comprises a bundle of capillaries. For example, the capillary body may comprise a plurality of fibres or threads or other fine bore tubes. The capillary body may comprise sponge-like or foam-like material. The structure of the capillary body forms a plurality of small bores or tubes, through which an aerosol-forming liquid can be transported by capillary action. The particular preferred material or materials will depend on the physical properties of the aerosol-forming substrate. Examples of suitable capillary materials include a sponge or foam material, ceramic- or graphite- based materials in the form of fibres or sintered powders, foamed metal or plastics material, a fibrous material, for example made of spun or extruded fibres, such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene or polypropylene fibres, nylon fibres, ceramic, glass fibres, silica glass fibres, carbon fibres, metallic fibres of medical grade stainless steel alloys such as austenitic 316 stainless steel and martensitic 440 and 420 stainless steels. The capillary body may have any suitable capillarity so as to be used with different liquid physical properties. The liquid has physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and vapour pressure, which allow the liquid to be transported through the capillary body. The capillary body may be formed from heat- resistant material. Advantageously, the capillary body may comprise a plurality of fibre strands. The plurality of fibre strands may be generally aligned along the length of the capillary body.

Electric heaters according to the invention may comprise a capillary body; a heating element arranged on an outer surface of the capillary body; and a pair of spaced apart electrical contacts fixed around the capillary body and over the heating element for electrically coupling the electric heater to the elongate support member. By fixing the electrical contacts around the capillary body and over the heating element, the electrical contacts may secure the heating element to the outer surface of the capillary body as well as providing an electrical connection. Advantageously, this may require fewer manufacturing steps than existing systems in which the ends of the heater element are manually connected to the electrical contacts, for example by welding. It may also allow the electric heater to be manufactured on an automated assembly line, so such devices can be manufactured more quickly with high repeatability. In such embodiments, at least one of the electrical contacts is dimensioned such that there is a frictional fit between an inner surface of that electrical contact and the outer surface of the capillary body. Providing such a frictional fit may allow the electrical contact to be secured on the capillary body without the need for additional fastening means or fastening steps. Preferably, each electrical contact is dimensioned such that there is a frictional fit between the inner surface of the electrical contact and the outer surface of the capillary body. The heating element may comprise a coil of electrically resistive wire wound around the capillary body, for example along the entire length of the capillary body.

Where electric heaters according to the invention comprise a capillary body, a heating element arranged on an outer surface of the capillary body, and a pair of spaced apart electrical contacts fixed around the capillary body and over the heating element, the capillary body is preferably compressible and the electrical contacts preferably extend around the circumference of the capillary body such that there is an interference fit between the electrical contacts and the capillary body. This may help to ensure that the heating element is securely fixed to the capillary body by the electrical contact without the need for adhesive or additional fixation steps, such as soldering or welding. It may also help to ensure a reliable electrical connection between the electrical contact and the heating element. The electrical contacts preferably extend around more than 50 percent of the circumference of the capillary body. This may result in a more secure fixation of the electrical contacts to the capillary body relative to examples in which the electrical contacts extend around less than 50 percent of the circumference of the capillary body. It may also help to ensure a reliable electrical connection between the electrical contact and the heating element.

Where electric heaters according to the invention comprise a capillary body, a heating element arranged on an outer surface of the capillary body, and a pair of spaced apart electrical contacts fixed around the capillary body and over the heating element, one or both of the electrical contacts may extend around substantially the entire circumference of the capillary body. At least one of the electrical contacts may circumscribe the capillary body. In such embodiments, the electrical contact may be ring shaped. Preferably, both electrical contacts circumscribe the capillary body. This may result in a more secure fixation of the electrical contacts to the capillary body relative to examples in which the electrical contacts extend around less than the entire circumference of the capillary body. It may also help to ensure a reliable electrical connection between the electrical contact and the heating element irrespective of the specific arrangement of the heating element on the outer surface of the capillary body and without restricting the arrangement of the heating element to ensure contact between the electrical contacts and the heating element. In certain embodiments, both electrical contacts circumscribe the capillary body and are dimensioned such that there is an interference fit between the electrical contacts and the capillary body. Where electric heaters according to the invention comprise a capillary body, a heating element, and a pair of spaced apart electrical contacts fixed around the capillary body and over the heating element, the electrical contacts may be rigid. This may result in a more robust assembly than one in which the electrical contacts are flexible. The electrical contacts may each comprise a ring of rigid material, such as a metallic ring. This may provide an electrical contact with high mechanical resistance and reliable electrical connection to the heating element. It may also enable the electric heater to be connected to the heater assembly by snap fitting the electrical contacts into a retaining clip in the device. Where the electrical contacts extend around the circumference of the capillary body, the opposed ends of each electrical contact may be co- operatively shaped such that the joint is non-linear or extends along an oblique line. In this context, the term "oblique line" means that the joint extends along a line which is nonparallel to the longitudinal axis of the capillary body. By having a joint which is non-linear or extending along an oblique line, relative movement between the opposed ends of each electrical contact in the longitudinal direction of the capillary body can be prevented or minimised.

Where electric heaters according to the invention comprise a capillary body, a heating element, and a pair of spaced apart electrical contacts fixed around the capillary body and over the heating element, the capillary body may be any suitable shape. In certain embodiments, the capillary body is elongate. The pair of electrical contacts may be spaced apart in a length direction of the capillary body. For example, the pair of electrical contacts may comprise a first electrical contact at or adjacent to a first end of the capillary body and a second electrical contact at any other location, such as at a midpoint along the length of the capillary body. The pair of electrical contacts may comprise a first electrical contact at or adjacent to a first end of the capillary body and a second electrical contact at or adjacent to the second end of the capillary body.

Where electric heaters according to the invention comprise a capillary body, the electric heater may further comprise a rigid support member extending along at least part of the length of the capillary body. The rigid support member increases the strength and rigidity of the electric heater to ensure a robust assembly which is easy to handling during manufacture. The rigid support member may be formed from a single, unitary component or from a plurality of components connected together. The rigid support member may extend through the core of the capillary body. The support member may be surrounded by the capillary body. The support member may be circumscribed by the capillary body. The presence of the rigid support member may reduce the overall radial compressibility of the capillary body, thus helping to ensure a tight fit between the electrical contacts and the heating element. The support member may be arranged on an outer surface of the capillary body. In some examples, the rigid support member comprises a central portion and a plurality of transverse ribs. This cross-sectional shape may result in a support member having a suitable rigidity without occupying a large amount of space within the capillary body and thus significantly reducing the wicking ability of the capillary body.

The plurality of transverse ribs may comprise a plurality of radially extending ribs.

In aerosol-generating devices according to the present invention, one or both of the first and second hollow shaft portions may be electrically conductive. The electrically conductive hollow shaft portion or portions may comprise a plurality of apertures, wherein the one or more electric heaters may be formed by one or more narrow regions of the hollow shaft portion between adjacent apertures.

Advantageously, having a heater assembly with one or more integral electric heaters may require fewer manufacturing steps and may allow the heater assembly to be manufactured on an automated assembly line. This may allow aerosol-generating devices according to the invention to be manufactured more quickly, simply and with high repeatability and consistency.

Such devices may be simplified, less expensive and more robust than devices in which the heater assembly comprises complicated and potentially fragile connections.

The apertures may be formed in one or both hollow shaft portions after the hollow shaft portion has been formed, for example by punching, drilling, milling, erosion, electro erosion, cutting, or laser cutting. The apertures may be formed integrally with the hollow shaft portion at the time of forming the hollow shaft portion, for example by casting or moulding the hollow shaft portion with the apertures or by forming the hollow shaft portion with the apertures in a deposition process, such as electrodeposition.

As used herein, "electrically conductive" means formed from a material having a resistivity of 1x10 "4 Qm, or less. As used herein, "electrically insulating" means formed from a material having a resistivity of 1 x10 4 Dm or more.

The at least one electric heater may be arranged on the hollow shaft portion in any suitable manner. In some embodiments, the at least one electric heater circumscribes the hollow shaft portion. This may allow for more even heating of the aerosol-forming substrate in the cartridge relative to devices in which the at least one electric heater does not circumscribe the hollow shaft portion. The at least one electric heater may circumscribe the hollow shaft portion continuously. The at least one electric heater may circumscribe the hollow shaft portion discontinuously in the form of a plurality of electric heaters spaced apart in the circumferential direction of the hollow shaft portion. In other embodiments, the at least one electric heater may extend around only part of the circumference of the hollow shaft portion.

Devices according to the invention comprise a main housing and a closure body. The main housing may be elongate. The main housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics that are suitable for food or pharmaceutical applications, for example polypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably, the material is light and non-brittle. Devices according to the invention may further comprise electric circuitry connected to the heater assembly and to an electrical power source. The electric circuitry may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of current to the heater assembly. Current may be supplied to the heater assembly continuously following activation of the device or may be supplied intermittently, such as on a puff by puff basis. The electric circuitry may advantageously comprise DC/AC inverter, which may comprise a Class-D or Class-E power amplifier.

The device advantageously comprises a power supply within the housing. For example the power supply may be a battery such as a lithium iron phosphate battery, or another form of charge storage device such as a capacitor. The power supply may require recharging and may have a capacity that allows for the storage of enough energy for one or more smoking experiences. For example, the power supply may have sufficient capacity to allow for the continuous generation of aerosol for a period of around six minutes, corresponding to the typical time taken to smoke a conventional cigarette, or for a period that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to allow for a predetermined number of puffs or discrete activations.

The device may comprises power supply connected to the heater assembly and electric circuitry connected to the power supply and to the heater assembly.

Where the heater assembly comprises a plurality of electric heaters which are fixed to and spaced along the length of the elongate piercing assembly, the electric circuitry is preferably configured to measure one or more electrical parameters of the plurality of electric heaters and to calculate an estimated remaining amount of aerosol forming substrate in the cartridge or an estimated distribution of aerosol forming substrate in the cartridge, based on the measured electrical parameters.

As used herein, the term "electrical parameter" is used to describe an electrical property, value or attribute that can be quantified by measurement, for example, resistivity, conductivity, impedance, capacitance, current, voltage, and resistance.

Advantageously, with this arrangement, the electric heaters have dual functionality: heating and sensing. This may allow the device to determine at any time an estimate of the state of the aerosol-forming substrate remaining in the cartridge. From this, the device may be operated differently by the electric circuitry to maintain desirable aerosol properties, or may inform the user of the current state of the aerosol-forming substrate to allow the user to take appropriate action, such as changing the cartridge or the orientation of the device, to avoid an adverse effect on aerosol characteristics. ln such embodiments, the electric circuitry is configured to separately measure the one or more electrical parameters of each of the plurality of electric heaters and to calculate the estimated remaining amount, or the estimated distribution, or the estimated remaining amount and the estimated distribution, based on differences in the measured electric parameters of two or more of the plurality of electric heaters.

Where the device comprises a power supply connected to the heater assembly and electric circuitry connected to the power supply and to the heater assembly, the device preferably further comprises a user indicator connected to power supply. The electric circuitry may be configured to operate the user indicator in response to the estimated remaining amount or the estimated distribution. The user indicator may have any suitable configuration, for example the user indicator may be for example a display, an audio output, a haptic output, or any combination thereof. This may allow the device to convey information to the user regarding the estimated remaining amount or the estimated distribution, or both, of liquid aerosol-forming substrate in the cartridge.

The electric circuitry may be configured to operate the user indicator when the estimated remaining amount falls below a threshold value to alert the user and to prompt the user into replacing the cartridge. The control circuitry may be configured to operate the user indicator when the estimated distribution suggests that device has been held at a particular angle for too long so that the user may be prompted to alter the orientation of the device, at least temporarily, so that the aerosol-forming substrate may be redistributed in the storage portion.

The control circuitry may be configured to inform a user about the estimated remaining amount or estimated distribution via a communication link with a separate device, such as a smartphone, swart-watch, tablet, desktop computer, or similar device.

Where the device comprises electric circuitry connected to a power source and configured to measure one or more electrical parameters of the plurality of electric heaters and to calculate an estimated remaining amount or estimated distribution, the electric circuitry may be further configured to control a supply of power to one or more of the plurality of electric heaters separately in response to the estimated remaining amount or the estimated distribution.

Advantageously, this may allow the device to determine which of the electric heaters is in the best condition to generate aerosol in the most effective way and to vary the supply of power accordingly. This may help to minimise variations in aerosol properties caused by variations in the distribution of the aerosol-forming substrate within the cartridge. It may also reduce overall energy consumption of the device by allowing the energy draw of the electric heaters to be selected in the most effective manner. The electric circuitry may be configured to increase the supply of power to one or more of the plurality of electric heaters in response to the estimated remaining amount or the estimated distribution. The electric circuitry may be configured to reduce the supply of power to one or more of the plurality of electric heaters in response to the estimated remaining amount or the estimated distribution.

Advantageously, this may allow the energy consumption of one or more of the electric heaters to be selectively reduced, for example where the estimated remaining amount or estimated distribution indicates that a particular electric heater is not well placed to generate an aerosol. It may also reduce the risk of damage to the electric heaters due to over heating, for example where a liquid aerosol-forming substrate is used and the electrical parameters indicate that one or more of the electric heaters is dry or partially dry.

The electric circuitry may be configured to reduce or increase the supply of power to one or more of the plurality of electric heaters in response to the estimated remaining amount or the estimated distribution. The electric circuitry may be configured to reduce the supply of power to one or more of the plurality of electric heaters while simultaneously increasing the supply of power to a different one or more of the plurality of electric heaters, in response to the estimated remaining amount or the estimated distribution.

According to a second aspect of the present invention, there is provided an electrically heated aerosol-generating system comprising an electrically heated aerosol-generating device according to any of the embodiments described above, and a consumable cartridge comprising a storage portion containing an aerosol forming substrate, the storage portion having a fluid permeable internal surface surrounding an open-ended passage extending through the cartridge, wherein the cartridge is enclosed in the cavity such that the elongate piercing assembly extends into the open-ended passage of the cartridge.

The system comprises a consumable cartridge. The consumable cartridge may be removably coupled to the aerosol-generating device. As used herein, the term 'removably coupled' is used to mean that the cartridge and device can be coupled and uncoupled from one another without significantly damaging either the device or cartridge. The cartridge may be removed from the aerosol-generating device when the aerosol-forming substrate has been consumed. The cartridge may be disposable. The cartridge may be reusable. The cartridge may be refillable with aerosol-forming substrate. The cartridge may be replaceable in the aerosol-generating device.

The aerosol-generating system may comprise an aerosol-forming chamber in which aerosol forms from a super saturated vapour and is then carried into the mouth of a user. An air inlet, air outlet and the chamber are preferably arranged so as to define an airflow route from the air inlet to the air outlet via the aerosol-forming chamber, so as to convey the aerosol to the air outlet and into the mouth of a user. The aerosol-forming chamber may be defined by one or both of the cartridge and the aerosol-generating device. As used herein, the term 'aerosol-forming substrate' relates to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may conveniently be part of an aerosol-generating article, such as a cartridge, or smoking article.

The aerosol-forming substrate is preferably an aerosol-forming liquid. As used herein, the terms "aerosol-forming liquid" and "liquid aerosol-forming substrate" are interchangeable. The storage portion preferably comprises a capillary wick forming part or all of the internal surface for transporting liquid aerosol-forming substrate from the storage portion to the heater assembly.

The storage portion may contain a single aerosol-forming substrate. The storage portion may contain two or more aerosol-forming substrates stored separately. For example, the storage portion may contain three aerosol-forming substrates stored separately, four aerosol- forming substrates stored separately, five aerosol-forming substrates stored separately, or six or more aerosol-forming substrates stored separately. Where the storage portion contains two or more aerosol-forming substrates stored separately, the heater assembly preferably comprises a plurality of electric heaters spaced along the length of the elongate piercing assembly, the plurality of electric heaters including at least one electric heater for each of the aerosol-forming substrates, each of the electric heaters being configured to heat its corresponding aerosol-forming substrate. This allows the aerosol-forming substrates to be heated independently.

In one particular embodiment, the storage portion of the consumable cartridge contains first and second aerosol forming substrates stored separately and the heater assembly comprises a plurality of electric heaters spaced along the length of the elongate piercing assembly, the plurality of electric heaters comprising a first electric heater for heating the first aerosol forming substrate to form a first aerosol and a second electric heater for heating the second aerosol forming substrate to form a second aerosol.

In aerosol-generating systems according to the invention, the storage portion is preferably compressible and the diameter of the open-ended passage extending through the cartridge is less than the outer diameter of one or both of the first and second hollow shaft portions. With this arrangement, the storage portion may be radially compressed by the piercing assembly to ensure a tight fit between the cartridge and the respective hollow shaft portion. This may facilitate contact between the electric heaters and the aerosol-forming substrate in the storage portion to allow consistent aerosol properties. It may also restrict or eliminate air flow between the cartridge and the outside of the hollow shaft portion, thereby facilitating the delivery of a consistent aerosol.

Also disclosed is a consumable cartridge for use with an electrically heated aerosol- generating device according to any of the embodiments described above, the cartridge comprising a storage portion containing an aerosol-forming substrate and having a fluid permeable internal surface surrounding an open ended passage extending through the cartridge; a first frangible seal across a first end of the open-ended passage; and a second frangible seal across a second end of the open-ended passage.

The provision of an open-ended passage within the cartridge may allow for a system that is compact. It may also allow the cartridge to be used in a system which is symmetrical and balanced which is advantageous when the system is a handheld system. An internal passage may also minimise heat losses from the device and allow the housing of the device and cartridge to be easily maintained at a temperature than is comfortable to hold.

The open-ended passage preferably forms a guiding and aligning means that co-operates with the elongate piercing assembly of devices according to the invention to facilitate the correct orientation and position of the cartridge into the device.

As used herein, the term "fluid permeable surface" refers to a surface that allows liquid or gas to permeate through it. The internal surface may have a plurality of openings formed in it to allow fluid to permeate through it.

The upstream and downstream ends of the cartridge may be capped by frangible seals. The cartridge may further include a sealing ring at one or both of the upstream and downstream ends of the open-ended passageway.

In aerosol-generating systems according to the invention, the aerosol forming substrate preferably comprises a liquid aerosol forming substrate.

The storage portion preferably contains first and second aerosol forming substrates stored separately. The first and second aerosol-forming substrates may be different.

The cartridge may comprise a first sealed compartment comprising a first aerosol-forming substrate and a second sealed compartment comprising a second aerosol-forming substrate. The first compartment and the second compartment are preferably arranged in series from the upstream end to the downstream end of the cartridge. That is, the second compartment is downstream of the first compartment. Preferably, each of the first compartment and the second compartment comprises a frangible barrier at each end. The frangible barrier is configured such that the barrier can be pierced by the elongate support member when the cartridge is inserted into the aerosol-generating device by the user. Preferably, each frangible barrier is made from metal film, and more preferably from aluminium film. Preferably, the first compartment and the second compartment of the cartridge abut one another. Alternatively, the first compartment and the second compartment may be spaced apart. The volume of the first compartment and the second compartment may be the same or different. Preferably, the volume of the second compartment is greater than the volume of the first compartment. The storage portion preferably forms an annular space surrounding the internal open- ended passage. The cartridge may have a generally cylindrical shape and may have any desired cross-section, such as circular, hexagonal, octagonal or decagonal.

In aerosol-generating systems according to the invention, the storage portion may comprise a tubular porous element in which a liquid aerosol-forming substrate is absorbed.

The storage portion preferably comprises a capillary wick and a capillary material containing liquid aerosol-forming substrate. The capillary wick may define the internal surface surrounding the open-ended passage. A capillary material is a material that actively conveys liquid from one end of the material to another. The capillary material may be advantageously oriented in the storage portion to convey liquid aerosol-forming substrate to the open-ended passage. The capillary material may have a fibrous structure. The capillary material may have a spongy structure. The capillary material may comprise a bundle of capillaries. The capillary material may comprise a plurality of fibres. The capillary material may comprise a plurality of threads. The capillary material may comprise fine bore tubes. The capillary material may comprise a combination of fibres, threads and fine-bore tubes. The fibres, threads and fine- bore tubes may be generally aligned to convey liquid to the electric heater. The capillary material may comprise sponge-like material. The capillary material may comprise foam-like material. The structure of the capillary material may form a plurality of small bores or tubes, through which the liquid can be transported by capillary action.

The capillary material may comprise any suitable material or combination of materials.

Examples of suitable materials are a sponge or foam material, ceramic- or graphite-based materials in the form of fibres or sintered powders, foamed metal or plastics materials, a fibrous material, for example made of spun or extruded fibres, such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene or polypropylene fibres, nylon fibres or ceramic. The capillary material may be made of a polymeric compound, including medical grade polymers such as ALTUGLAS® Medical Resins Polymethlymethacrylate (PMMA), Chevron Phillips K- Resin® Styrene-butadiene copolymer (SBC), Arkema special performance polymers Pebax®, Rilsan®, and Rilsan® Clear, DOW (Health+™) Low-Density Polyethylene (LDPE), DOW™ LDPE 91003, DOW™ LDPE 91020 (MFI 2.0; density 923), ExxonMobil™ Polypropylene (PP) PP1013H1 , PP1014H1 and PP9074MED, Trinseo CALIBRE™ Polycarbonate (PC) 2060- SERIES. The capillary material may be made of a metallic alloy, for example aluminium or stainless steel medical grade alloys. The capillary material may have any suitable capillarity and porosity so as to be used with different liquid physical properties. The liquid aerosol-forming substrate has physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and atom pressure, which allow the liquid to be transported through the capillary material by capillary action. The capillary material may be configured to convey the aerosol-forming substrate to the atomiser. ln aerosol-generating systems according to the invention, the aerosol-forming substrate may be an aerosol-forming liquid. In such embodiments, preferably the storage portion is a liquid storage portion for storing the aerosol-forming liquid.

The liquid aerosol-forming substrate may comprise nicotine. The nicotine containing liquid aerosol-forming substrate may be a nicotine salt matrix. The liquid aerosol-forming substrate may comprise plant-based material. The liquid aerosol-forming substrate may comprise tobacco. The liquid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol- forming substrate upon heating. The liquid aerosol-forming substrate may comprise homogenised tobacco material. The liquid aerosol-forming substrate may comprise a non- tobacco-containing material. The liquid aerosol-forming substrate may comprise homogenised plant-based material.

The liquid aerosol-forming substrate may comprise at least one aerosol-former. An aerosol-former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the system. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3- butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Aerosol formers may be polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1 ,3-butanediol and glycerine. The liquid aerosol-forming substrate may comprise other additives and ingredients, such as flavourants.

The aerosol-forming substrate may comprise nicotine and at least one aerosol former. The aerosol former may be glycerine. The aerosol-former may be propylene glycol. The aerosol former may comprise both glycerine and propylene glycol. The aerosol-forming substrate may have a nicotine concentration of between about 2% and about 10%.

Although reference is made to liquid aerosol-forming substrates above, it will be clear to one of ordinary skill in the art that other forms of aerosol-forming substrate may be used with other embodiments. For example, the aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds which are released from the substrate upon heating. The aerosol- forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former. Examples of suitable aerosol formers are glycerine and propylene glycol.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol- forming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, spaghettis, strips or sheets containing one or more of: herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco, extruded tobacco, cast leaf tobacco and expanded tobacco. The solid aerosol-forming substrate may be in loose form, or may be provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate may contain additional tobacco or non-tobacco volatile flavour compounds, to be released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules that, for example, include the additional tobacco or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol-forming substrate.

As used herein, homogenised tobacco refers to material formed by agglomerating particulate tobacco. Homogenised tobacco may be in the form of a sheet. Homogenised tobacco material may have an aerosol-former content of greater than 5% on a dry weight basis. Homogenised tobacco material may alternatively have an aerosol former content of between 5% and 30% by weight on a dry weight basis. Sheets of homogenised tobacco material may be formed by agglomerating particulate tobacco obtained by grinding or otherwise comminuting one or both of tobacco leaf lamina and tobacco leaf stems. Alternatively, or in addition, sheets of homogenised tobacco material may comprise one or more of tobacco dust, tobacco fines and other particulate tobacco by-products formed during, for example, the treating, handling and shipping of tobacco. Sheets of homogenised tobacco material may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco; alternatively, or in addition, sheets of homogenised tobacco material may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and non-aqueous solvents and combinations thereof.

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

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

Also provided is a kit for an electrically heated aerosol-generating system, the kit comprising an electrically heated aerosol generating device according to any of the embodiments described above, and a plurality of consumable cartridges according to any of the embodiments described above.

As used herein, the terms 'upstream' and 'downstream' are used to describe the relative positions of components, or portions of components, of cartridges, aerosol-generating devices and aerosol-generating systems in relation to the direction of air drawn through the cartridges, aerosol-generating devices and aerosol-generating systems during use thereof. The terms 'distal' and 'proximal', are used to describe the relative positions of components of aerosol- generating devices and aerosol-generating systems in relation to their connection to the device, such that the proximal end of a component is at the 'fixed' end which is connected to the device, and the distal end is at the 'free' end, opposite to the proximal end. Where a component is connected to the device at the downstream end of the component, the downstream end may be considered as the 'proximal' end, and vice versa.

As used herein, the terms "longitudinal" and "length" refer to the direction between the opposed ends of the cartridge, the device, or a component of the device, such as between its downstream or proximal end and the opposed upstream or distal end. The term "transverse" is used to describe the direction perpendicular to the longitudinal direction.

The upstream and downstream ends of the cartridge and the aerosol-generating device are defined with respect to the airflow when a user draws on the mouth end of the aerosol- generating device. Air is drawn into the cartridge or the device at its upstream end, passes downstream through the cartridge or the device and exits the cartridge or device at its downstream end.

As used herein, the term "air inlet" is used to describe one or more apertures through which air may be drawn into the aerosol-generating system.

As used herein, the term "air outlet" is used to describe one or more aperture through which air may be drawn out of the aerosol-generating system.

Features described in relation to one or more aspects may equally be applied to other aspects of the invention. In particular, features described in relation to the aerosol-generating device of the first aspect may be equally applied to the aerosol-generating system of the second aspect, and vice versa.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a longitudinal cross-section of an aerosol-generating system according to a first embodiment;

Figure 2 illustrates a longitudinal cross-section of a consumable cartridge for use with the aerosol-generating system of Figure 1 ;

Figure 3A illustrates a longitudinal cross-section of a first embodiment of heater assembly for the aerosol-generating system of Figure 1 ; Figure 3B illustrates a distal end view of the heater assembly of Figure 3A;

Figure 3C illustrates a side view of the heater assembly of Figure 3A;

Figure 4A illustrates a side view of a first embodiment of electric heater for the heater assembly of the aerosol-generating system of Figure 1 ;

Figure 4B illustrates an end view of the electric heater of Figure 4A;

Figure 4C illustrates a side view of an electric contact of the electric heater of Figure 4A, with the other components of the electric heater removed for clarity;

Figures 5A to 5C illustrate a method of inserting a consumable cartridge into the aerosol- generating device of the aerosol-generating system of Figure 1 ;

Figure 5D illustrates a longitudinal cross-section of the cartridge and heater assembly of the system of Figures 5A to 5C in which the system is held in a tilted position;

Figure 6A illustrates a longitudinal cross-section of a second embodiment of heater assembly for the aerosol-generating system of Figure 1 ;

Figure 6B illustrates a distal end view of the heater assembly of Figure 6A, in the direction of arrow B in Figure 6A;

Figure 6C illustrates a side view of the heater assembly of Figure 6A;

Figure 7A illustrates a longitudinal cross-section of a third embodiment of heater assembly for the aerosol-generating system of Figure 1 ;

Figure 7B illustrates a distal end view of the heater assembly of Figure 7A; and

Figure 8 illustrates a side view of a fourth embodiment of heater assembly for the aerosol- generating system of Figure 1.

Figure 1 is a schematic illustration of an aerosol-generating system 10 according to a first embodiment of the present invention comprising an aerosol-generating device 100 and an aerosol-generating article in the form of a consumable cartridge 200.

The device 100 comprises a main housing 102 containing a battery 104 and control electronics 106. The main housing 102 also defines a cavity 108 into which the cartridge 200 is received. The device 100 further includes a closure body in the form of a mouthpiece portion 1 10 including an outlet 1 12. In this example, the mouthpiece portion 1 10 is connected to the main housing 102 by a screw fitting, but any suitable kind of connection may be used, such as a hinged connection or a snap fitting. The device 100 further includes a heater assembly 300 comprising an elongate piercing assembly 302 and a plurality of electric heaters 400 supported by the piercing assembly 302. The elongate piercing assembly 302 is positioned centrally within the cavity 108 of the device 100 and extends along the longitudinal axis of the cavity 108. The piercing assembly 302 comprises a first hollow shaft portion 304 connected to the main housing 102 and a second hollow shaft portion 324 connected to the mouthpiece portion 1 10 via mouthpiece connectors 31 1. The first and second hollow shaft portions 304, 324 extend along the same longitudinal axis and meet at a junction 330 such that the elongate piercing assembly extends along the entire length of the cavity 108. The first and second hollow shaft portions 304, 324 together define an internal airflow passage 306 extending along the elongate piercing assembly 302. Air inlets 1 14 are provided in the main housing 102 upstream of the heater assembly 300 and are in fluid communication with the outlet 1 12 via the airflow passage 306.

As best seen in Figure 2, the cartridge 200 comprises a storage portion 202 including a tubular capillary wick 204 surrounded by a tubular capillary material 206 containing liquid aerosol-forming substrate. The cartridge 200 has a hollow cylindrical shape through which extends an internal passageway 208. The capillary wick 204 surrounds the internal passageway 208 so that the internal passageway 208 is at least partly defined by an inner surface of the capillary wick 204. The upstream and downstream ends of the cartridge 200 are capped by frangible seals 210, 212. The cartridge 200 further includes a sealing ring 214, 216 at each of the upstream and downstream ends of the internal passageway 208.

As shown in Figures 3A, 3B and 3C, the first hollow shaft portion 304 has a piercing surface 308 at its distal, or downstream end and the second hollow shaft portion 324 has a piercing surface 328 at its distal, or upstream end. In this example, the piercing surfaces 308 are each formed by a sharp tip at the distal end of the first and second hollow shaft portions 304, 324. The distal end of the first hollow shaft portion 304 has an inwardly tapering outer surface 309 and the distal end of the second hollow shaft portion 324 has an outwardly tapering inner surface 329, the outer and inner surfaces 309 and 329 being co-operatively shaped such that the outer surface 309 of the first hollow shaft portion 304 fits within the inner surface 329 of the second hollow shaft portion 324 to form a seal around the junction 330.

In the example shown, the heater assembly 300 includes three electric heaters 400 fixed to and spaced along the length of the elongate piercing assembly. One of the electric heaters 400 is fixed to the first hollow shaft portion 304 while the remaining two electric heaters 400 are fixed to the second hollow shaft portion 324. It wil be appreciated the heater assembly may comprise any suitable number of electric heaters. For example, the heater assembly may comprise a single electric heater, or two, three, four, five, six, seven, or eight or more electric heaters fixed to and spaced apart along the length of the elongate piercing member. Where the heater assembly comprises a plurality of electric heaters, these may be divided equally or unequally between the first and second hollow shaft portions.

Each of the electric heaters 400 is held within a plurality of apertures 310 in the first and second hollow shaft portions 305, 324. The apertures 310 are provided in pairs, with each pair supporting a single electric heater 400 at both of its ends. The two apertures in each pair are spaced apart around the circumferences of the hollow shaft portions 304, 324 so that each of the electric heaters 400 extends across the airflow passage 306. In this example, the plurality of apertures 310 comprises three pairs of apertures 312, 314, 316 supporting three electric heaters 400. The three pairs of apertures 312, 314, 316 are spaced apart along the length of the elongate piercing assembly 302 and aligned around the circumferences of the hollow shaft portions 304, 324 such that the longitudinal axes of the three electric heaters 400 are parallel and rotationally aligned. It will be appreciated that other arrangements of heater assembly are envisaged. For example, three alternative arrangements of heater assembly are discussed below in relation to Figures 6A to 6C, Figures 7A and 7B and Figure 8.

The first and second hollow shaft portions 304, 324 are both electrically conductive and at least partially divided into a plurality of electrically isolated sections 318, each associated with one or more electric heaters 400 and each electrically connected to the battery in the device. In the case of the first hollow shaft portion 304, the electrically isolated sections 318 are connected to the battery by electrical connections (not shown) at the base of the first hollow shaft portion 304. In the case of the second hollow shaft portion 324, electrically isolated sections 318 may be electrically connected to the battery in the device via the first hollow shaft portion 304 and the junction 330, or via the mouthpiece connectors between the second hollow shaft portion 324 and the mouthpiece portion 310 and via electrical connections (not shown) between the mouthpiece portion 1 10 and the main housing 102.

The apertures 310 are each formed in one of the electrically isolated sections 318. The electrically isolated sections 318 are electrically isolated from each other by insulating gaps 320. Thus, the electric heaters 400 may be electrically isolated from the each other to allow separate operation, control, or monitoring, without the need for separate electrical wiring for each heater. In this example, the gaps 320 are air gaps. That is, the gaps 320 do not contain insulating material. In other examples, one or more of the gaps 320 may be filled or partially filled with an electrically insulating material.

As best seen in Figures 4A to 4C, each electric heater 400 comprises a capillary body 402, a heating element 404 arranged on an outer surface of the capillary body 402, and a pair of spaced apart electrical contacts 406 fixed around the capillary body 402 and over the heating element 404. The capillary body 402, or capillary wick, comprises a plurality of fibres 408 through which an aerosol-forming liquid can be transported by capillary action. In this example, the plurality of fibres 408 are generally aligned along the length of the capillary body 402. In other examples, the plurality of fibres may be woven or braided in a specific pattern. This allows the physical characteristics of the capillary wick, such as mechanical strength or capillarity, to be altered by using a particular pattern of fibres. It may also allow the capillary wick to maintain its shape and dimensions more effectively than with parallel fibres. The capillary body is compressible, for example due to the presence of interstices between adjacent fibres. In this example, the ends of the capillary body 402 are rounded or domed. This may help to increase the surface area between the capillary body 402 and an aerosol-forming liquid in the cartridge 200. In other examples, the ends of the capillary body 402 may be flat or planar. The heating element 404 of each electric heater 400 is formed from a coil of electrically resistive wire wound around the capillary body 402 and extending along its entire length. The wire may have any suitable cross-sectional shape. In this example, the wire has a round cross- sectional shape. In other examples, the wire may have an oval, triangular, square, rectangular, or flat cross-sectional shape. This may increase heat transfer between the fibres 408 of the capillary body 402 and the heating element 404.

The electrical contacts 406 of each electric heater 400 comprise a first metallic ring 412 at a first end of the capillary body 402 and a second metallic ring 414 at a second end of the capillary body 402. The first and second rings 412, 414 extend around the entire circumference of the capillary body 402 and over the heating element 404. The inner diameter of each of the rings 412, 414 is less than the outer diameter of the capillary body 402. Consequently, there is an interference fit between the rings 412, 414 and the capillary body 402 underneath. This ensures that the rings 412, 414 press into the capillary body 402 and are secured thereto, with the heating element 404 retained between. This helps to ensure a reliable electrical connection between the electrical contacts 406 and the heating element 404. As the electrical contacts 406 extend around the entire circumference of the capillary body 402, it is not necessary to carefully match the rotational position of the electrical contacts with the position of the heating coil 404 during assembly to ensure an electrical connection.

The first and second rings 412, 414 of the electrical contacts 406 are rigid and formed from a bent sheet of metal. The opposed ends of the bent sheet are connected together at a joint 416. In this example, the opposed ends are co-operatively shaped such that the joint 416 extends along an oblique line. This helps each of the electrical contacts 406 to maintain its shape by resisting relative movement between its opposed ends in the length direction of the electric heater 400. In other examples, the opposed ends may be co-operatively shaped so that joint has a non-linear shape, such as a wavy, sinusoidal, parabolic, U-, V-, curved, or zig-zag shape. Again, this helps each of the electrical contacts 406 to maintain its shape for the reasons discussed above.

In the example shown in Figures 4A to 4C, the capillary body 402 has a circular cross- section and the electrical contacts 406 are in the form of circular rings. However, in other examples, the capillary body 402 and electrical contacts 406 may have any suitable cross- sectional shape. For example, the capillary body and electrical contacts may have an oval, triangular, square, rectangular, or lozenge-shaped cross-sectional shape.

The electrical contacts 406 and the apertures 310 in the elongate piercing assembly 302 are co-operatively sized to provide a frictional fit. This ensures a secure fit between the hollow shaft portion 304 and the electric heaters 400. This may also enable a good electrical connection to be maintained between the heating element of each electric heater and the battery 104 in the device 100. In this example, the apertures 310 are circular to match the shape of the electrical contacts of the electric heaters 400. In other examples, the cross-sectional shape of the electrical contacts may be different and the shape of the apertures determined accordingly. In some examples, the electrical contacts may have one or more outwardly extending tabs and the first and second hollow shaft portions may have corresponding notches around the apertures which form ports into which the tabs may be received. Alternatively, or in addition, the elongate piercing assembly 302 may include one or more clips in which the tabs may be located and retained.

Referring to Figures 5A, 5B and 5C, insertion of the cartridge 200 into the device 100 of the system 10 will now be described.

To insert the cartridge 200 into the device 100, and thereby assemble the system 10, the first step is to remove the mouthpiece portion 1 10 from the main housing 102 of the device 100 and to insert the article 200 into the cavity 108 of the device 100. During insertion of cartridge 200 into the cavity 108, the first piercing surface 308 at the distal end of the first hollow shaft portion 304 breaks the first frangible seal at the upstream end of the cartridge 200, as shown in Figure 5A.

The mouthpiece portion 1 10 is then placed over the end of the main housing 102 so that the second hollow shaft portion 324 is aligned with the internal passageway in the cartridge 200, as shown in Figure 5B.

As the mouthpiece portion 1 10 is further engaged with the main housing 102, the second piercing surface 328 at the distal end of the second hollow shaft portion 324 engages with and breaks through the second frangible seal at the downstream end of the cartridge 200 to create a hole in the second frangible seal. The mouthpiece portion 1 10 is then fully engaged with the main housing 102 to fully insert and enclose the cartridge 200 in the cavity 108, as shown in Figure 5C.

When the cartridge 200 is fully inserted into the cavity 108, the holes in the first and second frangible seals at the upstream and downstream ends of the cartridge 200 caused by the first and second hollow shaft portions 304, 324 each have a diameter approximately equal to the outer diameters of the hollow shaft portions 304, 324. The sealing rings at the upstream and downstream ends of the cartridge 200 form a seal around the hollow shaft portions 304, 324. Together with the frangible seals this reduces or prevents leakage of liquid aerosol-forming substrate from the cartridge 200 and out of the system 10.

As also shown in Figure 5C, when the cartridge 200 is fully inserted into the cavity 108 of the aerosol-generating device 100, an airflow pathway, shown by arrows in Figure 5C, is formed through the aerosol-generating system 10 via the internal passageway 208 in the cartridge 200 and the airflow passage 306 in the heater assembly 1300. As further shown in Figure 5C, when the cartridge 200 is fully inserted, the electric heaters 400 are in fluid communication with the storage portion 202 of the cartridge 200 via the capillary wick 204 at the inner surface of the internal passageway 208 of the cartridge 200 and via the apertures in the first and second hollow shaft portions 304, 324.

In use, liquid aerosol-forming substrate is transferred from the storage portion 202 to the capillary body 402 of each electric heater 400 via capillary action and through the plurality of apertures in the first and second hollow shaft portions 304, 324. In this example, the outer diameter of the first and second hollow shaft portions 304, 324 of the elongate piercing assembly 302 is greater than the inner diameter of the internal passageway 208 of the cartridge 200 so that the storage portion 202 of the cartridge 200 is compressed by the heater assembly 300. This ensures direct contact between the ends of the electric heaters 400 and the storage portion 202 to help transfer of liquid aerosol-forming substrate to the electric heaters 400.

The battery supplies electrical energy to the heating element of each electric heater 400, via the first and second hollow shaft portions 304, 324 and the electrical contacts 406. The heating elements heat up to vaporise liquid substrate in the capillary body of the electric heaters 400 to create a supersaturated vapour. At the same time, the liquid being vaporised is replaced by further liquid moving along the capillary wick of the liquid storage portion 202 and the capillary body of each electric heater 400 by capillary action. (This is sometimes referred to as "pumping action".) When a user draws on the mouthpiece portion 1 10, air is drawn through the air inlets 1 14, through the airflow passage of the hollow shaft portion 304, past the electric heaters 400, into the mouthpiece portion 1 10 and out of the outlet 1 12. The vaporised aerosol-forming substrate is entrained in the air flowing through the airflow passage of the hollow shaft portion 304 and condenses within the mouthpiece portion 1 10 to form an inhalable aerosol, which is carried towards the outlet 1 12 and into the mouth of a user.

The device may be operated by a user-operated switch (not shown) on the device 100. Alternatively, or in addition, the device may include a sensor for detecting a user puff. When a puff is detected by the sensor, the control electrics control the supply of electrical energy from the battery to the electric heaters 400. The sensor may comprise one or more separate components. In some examples, the puff sensing function is performed by the heating elements of the heater and wick assemblies. For example, by measuring with the control electronics one or more electrical parameters of the heating elements and detecting a particular change in the measured electrical parameters which is indicative of a puff.

During use of the system, the distribution of liquid aerosol-forming substrate in the cartridge may change. For example, as the liquid aerosol-forming substrate in the storage portion is depleted during use, or where the system is held at an angle for a sufficient period of time. This change in the distribution of liquid aerosol-forming substrate may lead to differences in the amount of liquid in the capillary body of each electric heater and, consequently, the temperature of the heating element of each electric heater. This is discussed below in relation to Figure 6. Figure 5D shows a longitudinal cross-section of the cartridge 200 and heater assembly 300 of the aerosol-generating system following a period in which the system has been held in a tilted position. As shown, the remaining liquid 203 in the cartridge 200 has settled in the storage portion 202 at an angle to the heater assembly 300. As the electric heaters are spaced apart along the length of the cartridge 200, the amount of liquid aerosol-forming substrate drawn up by the capillary bodies of the electric heaters is not uniform. In particular, the capillary body 402 of the first electric heater 401 at the upstream end of the heater assembly 300 is saturated with liquid aerosol-forming substrate, while the second electric heater 403 midway along the length of the heater assembly 300 is only partially wet with liquid aerosol-forming substrate, and the third electric heater 405 at the downstream end of the heater assembly 300 is dry. Consequently, the electric heaters 401 , 403, 405 run at different temperatures. As the electrical parameters of each electric heater, such as the resistivity, conductivity, impedance, capacitance, current, voltage, and resistance of the heating element, may vary as a function of the temperature, the distribution of the liquid aerosol-forming substrate or the remaining amount of liquid aerosol-forming substrate may be estimated by the control circuitry through measuring the electrical parameters of each electric heater. The control electronics is configured to separately measure one or more electrical parameters of each electric heater during use and to calculate an estimated remaining amount, or estimated distribution, of liquid aerosol-forming substrate in the cartridge based on differences in the measured electrical parameters from the electric heaters. Thus, the electric heaters function both as heaters and as sensors.

The device includes a user indicator (not shown), such as a display or audio or haptic output, connected to the control circuitry, which may be used to convey information to the user regarding the estimated remaining amount of liquid aerosol-forming substrate in the cartridge 200. When the estimated remaining amount falls below a threshold level, the electric circuitry may also be configured to operate the user indicator to alert the user and to prompt the user into replacing the cartridge needs changing. The control circuitry may also be configured to estimated the distribution of liquid aerosol-forming substrate in the cartridge based on differences in the measured electrical parameters from the electric heaters and to operate the user indicator when the estimated distribution suggests that system has been held at a particular angle for too long to alert the user that the orientation of the device 100 should be altered, at least temporarily, to allow the liquid aerosol-forming substrate to be redistributed in the storage portion. In this, or other examples, the control circuitry may be configured to alert the user about the estimated remaining amount or estimated distribution via a communication link with a separate device, such as a smartphone, swart-watch, tablet, desktop computer, or similar device.

In addition to detecting differences in electrical parameters in the electric heaters 400 and calculated an estimated remaining amount, or estimated distribution, of liquid aerosol-forming substrate in the cartridge 200, the control circuitry 106 is also configured to control the supply of electrical power to each of the electric heaters 400 in response to the estimated remaining amount, or estimated distribution. In particular, where the measured electrical parameters indicate that one or more of the electric heaters 400 is partially dry, the control electronics 106 is configured to reduce the supply of electrical energy to that electric heater. This allows the system 10 to determine which of the electric heaters 400 is in the best condition to generate aerosol in the most effective way. This allows adverse changes to the properties of aerosol generated by the system 10, caused by variations in wetness and temperature across the electric heaters, to be minimised. It may also reduce energy consumption of the system 10, and reduce the risk of damage to the electric heaters due to over heating. Where the electrical parameters indicate that one or more of the electric heaters 400 is dry, the control electronics 106 is configured to reduce the supply of electrical energy to that electric heater to zero.

Figures 6A, 6B and 6C illustrate a heater assembly 600 according to a second embodiment of the invention. The heater assembly 600 has a similar structure to the heater assembly 300 of the first embodiment and where the same features are present, like reference numerals have been used. As with the heater assembly of the first embodiment, the elongate piercing member 602 formed by the first and second hollow shaft portions 604, 624 comprises three pairs of apertures 612, 614, 616 in which three electric heaters 401 , 403, 405 are held such that their longitudinal axes are parallel in the transverse direction. However, unlike in the heater assembly 300 of the first embodiment, in the heater assembly 600 according to a second embodiment, the central, second pair of apertures 614 is offset around the circumference of the first hollow shaft portion 604 by 90 degrees relative to the first and third pairs of apertures 612, 616. Consequently, the longitudinal axis of the central electric heater 403 is rotated by 90 degrees about the longitudinal axis of the hollow shaft portions 604, 624 relative to the first and second electric heaters 401 , 405. This may allow for more efficient use of the liquid aerosol- forming substrate in the cartridge in comparison to the heater assembly 300 of the first embodiment.

Figures 7A and 7B illustrate a heater assembly 700 according to a third embodiment of the invention. The heater assembly 700 has a similar structure to the first and second embodiments of heater assembly 300 and 600 and where the same features are present, like reference numerals have been used. As with the heater assembly 600 of the second embodiment, the hollow shaft portion 704 comprises three pairs of apertures 712, 714, 716 in which three electric heaters 401 , 403, 405 are held such that their longitudinal axes are parallel in the transverse directions. However, unlike in the heater assembly 600 of the second embodiment, in the heater assembly 700 according to the third embodiment, the pairs of apertures 712, 714, 716 are each offset around the circumference of the first and second hollow shaft portions 704, 724 so that the longitudinal axes of the electric heaters 401 , 403, 405 are parallel in the transverse direction but rotated about the longitudinal axis of the hollow shaft portions 704, 724 relative to each other. In this example, the longitudinal axis of each electric heater 401 , 403, 405 is rotated by a uniform amount of less than 90 degrees from its adjacent electric heater or heaters. Consequently, the electric heaters 401 , 403, 405 are arranged in a spiral, or helix, pattern along the elongate piercing member 702. In other examples, the electric heaters may be rotated about the longitudinal axis of the hollow shaft portions 704, 724 by a non-uniform amount.

Figure 8 illustrates a heater assembly 800 according to a fourth embodiment of the invention. As with the heater assemblies 300, 600 and 700 of the first, second and third embodiments, the heater assembly 800 of the fourth embodiment comprises an elongate piercing assembly 802 comprising first and second electrically conductive hollow shaft portions 804, 824 defining an airflow passage. Again, the first and second hollow shaft portions 804, 824 comprise a plurality of apertures 810 spaced apart along the length of the elongate piercing assembly 802 and are at least partially divided into a plurality of electrically isolated sections 818 which are separated from each other by insulating gaps 820. Unlike the heater assemblies of the first, second and third embodiments, the apertures 810 of the heater assembly 800 of the fourth embodiment are not arranged to support separate electric heaters. Instead, the apertures 810 are arranged in a plurality of groups of apertures 810 spaced apart along the length of the elongate piercing assembly 802, with each group of apertures 810 defining an electric heater 850 comprising one or more heating elements formed by narrow regions of the hollow shaft portion 804, 824 located between adjacent apertures 810. In this manner, the electric heaters 850 are defined by the hollow shaft portions 804, 824 themselves. The groups of apertures 810, and thus the electric heaters 850, are each formed such that they extend between two of the electrically isolated sections 818. In the example shown in Figure 8, the electric heaters 850 are each located at the end of a different electrically isolated section 818. In this manner, the electric heaters 850 are electrically isolated from each other by the insulating gaps 820. The apertures 810 are preferably sized so that, when in use, liquid aerosol-forming substrate is drawn in to the electric heaters 850 by capillary action through the apertures 810. In the example shown in Figure 8, the groups of apertures 810 are aligned around the circumference of the hollow shaft portions 804, 824. In other examples, two or more of the groups of apertures 810 may be offset around the circumferences of the hollow shaft portions 804, 824.

The specific embodiments and examples described above illustrate but do not limit the invention. It is to be understood that other embodiments of the invention may be made and the specific embodiments and examples described herein are not exhaustive.