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Title:
AN AEROSOL-GENERATING DEVICE WITH EFFICIENT HEATING
Document Type and Number:
WIPO Patent Application WO/2019/115475
Kind Code:
A1
Abstract:
An aerosol-generating device a housing, a heating element within the housing configured to heat an aerosol-forming substrate so as to generate an aerosol; the housing comprising an air outlet and an air inlet, a first air flow passage extending from the air inlet to the heating element and a second air flow passage in fluid communication with the first air flow passage, the second air flow passage extending from the heating element to the air outlet; and a thermoelectric device between the first air flow passage and the second air flow passage, the thermoelectric device configured to exchange heat between an air supply in the first air flow passage and the generated aerosol in the second air flow passage.

Inventors:
SCHALLER, Jean-Pierre (Rue de la Servette 34, 1202 Genève, 1202, CH)
BESSANT, Michel (Rue Arnold-Guyot 5, 2000 Neuchâtel, 2000, CH)
GONZALEZ FLOREZ, Ana Isabel (Chemin de l'Ochettaz 33 b, 1025 St-Sulpice, 1025, CH)
Application Number:
EP2018/084232
Publication Date:
June 20, 2019
Filing Date:
December 10, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
PHILIP MORRIS PRODUCTS S.A. (Quai Jeanrenaud 3, Neuchâtel, CH-2000, CH)
International Classes:
A24F47/00; A61M15/00; H01L35/00
Domestic Patent References:
WO2012026740A22012-03-01
Foreign References:
US20160044960A12016-02-18
US3084698A1963-04-09
EP2216062A12010-08-11
DE19955078A12001-05-17
Other References:
None
Attorney, Agent or Firm:
REDDIE & GROSE LLP (The White Chapel Building, 10 Whitechapel High Street, London Greater London E1 8QS, E1 8QS, GB)
Download PDF:
Claims:
CLAIMS

1. An aerosol-generating device comprising:

a housing,

a heating element within the housing configured to heat an aerosol-forming substrate so as to generate an aerosol;

the housing comprising an air outlet and an air inlet, a first air flow passage extending from the air inlet to the heating element and a second air flow passage in fluid communication with the first air flow passage, the second air flow passage extending from the heating element to the air outlet, and wherein the first air flow passage and the second air flow passage extend longitudinally in the housing and adjacently to one another, such that the first air flow passage and the second air flow passage share a passage wall; and

a thermoelectric device between the first air flow passage and the second air flow passage, the thermoelectric device configured to exchange heat between an air supply in the first air flow passage and the generated aerosol in the second air flow passage, and wherein the thermoelectric device is positioned across a section of the passage wall to exchange heat between the air supply in the first air flow passage and the generated aerosol in the second air flow passage.

2. The aerosol-generating device of claim 1 , wherein the thermoelectric device is

configured to exchange heat by transferring heat energy from the generated aerosol in the second air flow passage to the air supply in the first air flow passage, so as to reduce the temperature of the generated aerosol exhausted at the air outlet, and to increase the temperature of air supply at the heating element.

3. The aerosol-generating device of claim 1 or claim 2, wherein the air inlet and the air outlet are arranged at a first end of the housing and the heating element is arranged at a second end of the housing opposite to the first end of the housing.

4. The aerosol-generating device of claim 3, wherein the housing is open at the first end to define a cavity for receiving the aerosol-forming substrate, said cavity comprises the second air flow passage.

5. The aerosol-generating device of claim 4, wherein at least a portion of the second air flow passage extends parallel to the heating element and passes through the aerosol-forming substrate received in the cavity.

6. The aerosol-generating device of any of the preceding claims, further comprising at least one additional air inlet along the first airflow passage for supplying an additional air supply to join the air supply in the first air flow passage.

7. The aerosol-generating device of any of the preceding claims, further comprising an air inlet adjustment mechanism for adjusting an aperture size of the air inlet.

8. The aerosol-generating device of any of the preceding claims, wherein the housing comprises an inner tube and an outer tube, wherein the first air flow passage is defined between the inner tube and the outer tube, and wherein a cavity defining the second air flow passage is within the inner tube.

9. The aerosol-generating device of claims 1 -8, wherein the thermoelectric device comprises a first thermoelectric device and a second thermoelectric device, wherein at least a part of the first thermoelectric device is stacked on the second thermoelectric device.

10. The aerosol-generating device of any of the preceding claims, wherein the thermoelectric device, or a passage wall shared between first air flow passage and the second air flow passage, or the thermoelectric device and the passage wall comprises at least one of protrusions and dimples for improving heat transfer between the air supply in the first air flow passage and the generated aerosol in the second air flow passage.

1 1 . The aerosol-generating device of any of the preceding claims, further comprising a controller in communication with the thermoelectric device; wherein the controller is configured to control a current supplied to the thermoelectric device so as to control an amount of heat exchanged between the air supply in the first air flow passage and the generated aerosol in the second air flow passage.

12. An aerosol generating system comprising the aerosol-generating device of any of the preceding claims and an aerosol-forming article having an aerosol-forming substrate in the cavity of the aerosol-generating device.

13. A method of generating an aerosol from an aerosol-forming substrate comprising: drawing an air supply through a first air flow passage;

heating the aerosol-forming substrate to generate an vapour; drawing the air from the first air flow passage and the generated vapour through a second air flow passage; and

exchanging heat between the first air flow passage and the second air flow passage using a thermoelectric device.

14. The method of claim 13, wherein the step of exchanging heat is carried out simultaneously with the step of heating said aerosol-forming substrate.

15. The method of claims 13 or 14, further comprising of determining the temperature of the air supply and/or the air and vapour in the second air flow passage, and wherein the step of exchanging heat is carried out when the determined temperature of the air supply and/or the generated aerosol falls outside a predetermined range.

Description:
AN AEROSOL-GENERATING DEVICE WITH EFFICIENT HEATING

The present specification relates to an aerosol-generating device that is configured to heat an aerosol-forming substrate and to generate an aerosol. In particular, the invention relates to a housing for an aerosol-generating device that provides for management of air temperature in the device.

In many handheld aerosol-generating devices, an electrical heater is used for heating an aerosol-forming substrate to generate an aerosol for user inhalation. The aerosol-forming substrate is typically provided in an aerosol-forming article that is inserted into the device. Typically, the aerosol-forming substrate is heated for vaporising volatile compounds in the substrate to form an aerosol. This can be accomplished either by internal heating, using a pin or blade-shaped resistive heater inside the aerosol-forming substrate, or by external heating, using one or more heaters external to the substrate

In handheld devices one challenge is to cool the vapour within a short space to form a desirable aerosol before the aerosol reaches the user’s mouth. If the aerosol is too hot it can be uncomfortable for the user. Also, if cooling is not sufficiently rapid, it can lead to undesirable aerosol-properties in terms of droplet size and density. This requirement has led to the use of cooling elements, such as crimped polylactic sheets within the aerosol-forming articles. But these cooling elements significantly increase the cost of each aerosol-forming article.

Another challenge, particularly for externally heated systems, is to adequately heat the aerosol-forming substrate to release the volatile compounds without raising the heater temperature so high that other parts of the device and aerosol-forming article become overheated. In particular it is desirable to avoid releasing undesirable compounds from the paper wrapping that typically covers the aerosol-forming substrate.

It would be desirable to provide an efficient aerosol generating device that is able to cool the vapour and aerosol exiting the device so as to improve the user’s experience, and to provide a device that is able to operate with a lower heater temperature.

In a first aspect of the present disclosure there is provided an aerosol-generating device comprising a housing, a heating element within the housing configured to heat an aerosol- forming substrate so as to generate an aerosol, the housing comprising an air outlet and an air inlet, a first air flow passage extending from the air inlet to the heating element and a second air flow passage in fluid communication with the first air flow passage, the second air flow passage extending from the heating element to the air outlet; and a thermoelectric device between the first air flow passage and the second air flow passage, the

thermoelectric device configured to exchange heat between an air supply in the first air flow passage and the generated aerosol in the second air flow passage. A plurality of thermoelectric devices may be provided between the first air flow passage and the second air flow passage. The provision of a plurality of thermoelectric devices increases the amount of heat that can be exchanged between the air supply and the generated aerosol.

The thermoelectric device may advantageously operate as a heat pump to transfer heat energy from the generated aerosol in the second air flow passage to the air supply in the first air flow passage, thus reducing the temperature of generated aerosol exhausted at the air outlet, for example a mouthpiece, as well as increasing the temperature of air supply at the heating element.

A cooler aerosol exhausted through the air outlet may advantageously offer the user a more pleasurable experience.

Moreover, the air supply from the air inlet may be preheated by the thermoelectric device. Thus the energy as required by the heating element, and in particular the temperature of the heating element may be reduced, enabling a more energy efficient aerosol-generating device.

Furthermore, the thermoelectric device may advantageously eliminate the need for an expensive aerosol-cooling device, such as a crimped polylactic sheet, reducing the cost of the consumable portion of the system.

The thermoelectric device may be a Peltier element. The use of a Peltier element provides heating/cooling at the surface of the heater upon applying an electrical current to the Peltier element. The Peltier element is of a simple construction and does not comprise any moving parts and so is reliable. In addition, it is relatively compact and lightweight, making it an ideal choice for use in handheld aerosol-generating devices.

The aerosol-generating device may be a handheld device, i.e. it may be portable and allow the user to operate in a manner similar to smoking a lit-end cigarette. The aerosol- generating device may be connectable to an electrical energy supply for supplying the electrical energy to the heating element so as to heat the aerosol-forming substrate. For example, the electrical energy supply may be a rechargeable battery.

The heating element may be configured to heat an aerosol-forming substrate continuously during operation of the device. “Continuously” in this context means that heating is not dependent on air flow through the device, so that power may be delivered to the heating element even when there is no airflow through the device. Cooling the housing of the device is particularly desirable in continuously heated devices as the temperature of the housing may rise in periods when power is being supplied to the heating element but air is not being drawn through the device. Alternatively, or in addition, the device may include means to detect air flow. The heating element may be configured to heat the aerosol-forming substrate only when the air flow exceeds a threshold level, indicative of a user drawing on the device.

As used herein, an‘aerosol-generating device’ relates to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-forming substrate may be part of an aerosol-forming article. An aerosol-generating device may be a smoking device that interacts with an aerosol-forming substrate of an aerosol- forming article to generate an aerosol that is directly inhalable into a user’s lung thorough the user's mouth.

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- forming article.

As used herein, the terms ‘aerosol- forming article’ refer to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol- forming article may generate an aerosol that is directly inhalable into a user’s lung through the user's mouth. However in contrast to a conventional lit-end cigarette the aerosol-forming article does not require combustion to generate an aerosol. An aerosol-forming article may be disposable. An aerosol-forming article may be, or may comprise, a tobacco stick.

As used herein, the term ‘aerosol generating system’ refers to a combination of an aerosol-generating device and one or more aerosol-forming articles for use with the device. An aerosol-generating system may include additional components, such as a charging unit for recharging an on-board electric power supply in an electrically operated or electric aerosol-generating device.

As used herein the term‘mouthpiece portion’ refers to a portion of an aerosol-forming article that is placed into a user’s mouth in order to directly inhale an aerosol generated by the aerosol-forming article or aerosol-generating device. The aerosol is conveyed to the user’s mouth through the mouthpiece.

The air inlet and the air outlet may be arranged at a first end, or a proximal end, of the housing closest to the user and the heating element further from the user. This arrangement may advantageously lengthen the flow path (the first air flow passage and the second air flow passage) as defined between the air inlet and the air outlet, thus improving the heat transfer efficiency by allowing a lengthier thermoelectric device to be installed along said flow path.

The first air flow passage may be linear, extending straight from the air inlet or inlets to the distal end of the cavity. However, the first air flow passage may be formed in any shape, such as a helical shape or a serpentine shape. Different shaped air flow paths may be used to increase the available surface area so as to improve heat transfer between the first air flow passage and the second air flow passage, and/or to match other aspects of the device, such as the shape of the cavity and the heater.

The housing may be open at the first end to define a cavity for receiving the aerosol- forming substrate. The cavity may comprise the second air flow passage. At least a portion of the second air flow passage may extend parallel to the heating element and passes through the aerosol-forming substrate as received in the cavity. The first air flow passage and the second air flow passage may extend longitudinally in the housing and adjacent to one another, such that the first air flow passage and the second air flow passage share a passage wall. The thermoelectric device may be positioned across a section of a passage wall, e.g. through an opening in the passage wall, to exchange heat between the air supply in the first air flow passage and the generated aerosol in the second air flow passage. By extending the first air flow passage and the second air flow passage longitudinally and adjacently to each other, a large portion of the passage wall may be shared between them, allowing a longer thermoelectric device or several thermoelectric devices to be provided for carrying out heat exchange.

The device may comprise at least one additional air inlet along the first air flow passage. An additional air supply from the additional air inlet may join the air supply in the first air flow passage. The air supply from the air inlet is mixed with the additional air supply from the at least one additional air inlet in the first air flow passage. The thermoelectric device may be configured to exchange heat between the mixed air supply in the first air flow passage and the generated aerosol in the second air flow passage. A plurality of air supplies each from a discrete air inlet may be mixed before being heated at the thermoelectric device. The plurality of air inlets together provide a sufficient amount of air supply for generating an aerosol. Alternatively, the housing may be configured to mix the additional air supply with the air supply from the thermoelectric device in the first air flow passage. That is, an air supply as heated by the thermoelectric device may be mixed with an unheated air supply before the mixed air supplies are further heated at the heating element. These arrangements may advantageously allow selective heating between the air supply and/or the additional air supply by the thermoelectric element, as such allowing the temperature of the mixed air supply and additional air supply at the heating element to be fine-tuned. This may be beneficial to allow different air temperatures to be used for different aerosol-forming articles.

The housing may include an air inlet adjustment mechanism to allow an aperture size of the air inlet, or the at least one additional air inlet to be adjusted. For example, the adjustment mechanism may comprise a shell coupled to the exterior of the housing having an aperture. Rotation or translation of the shell on the housing may block (fully or partially) one or more openings on the housing forming the air inlet or inlets. This provides the ability for the user to adjust the device according to his or her preference or to suit different aerosol-forming articles. Alternatively, the adjustment mechanism may comprise a diaphragm shutter or a leaf shutter that is able to control the size of air inlet in an automated manner.

The housing may comprise an inner tube and an outer tube, wherein the first air flow passage is defined between the inner tube and the outer tube. A cavity defining the second air flow passage may be within the inner tube. The outer tube may mimic the appearance of a conventional cigarette. The heating element may be tubular and accommodated along the inner tube. The thermoelectric device may be tubular or a plurality of thermoelectric devices may be arranged in a tubular configuration, and form part of the inner tube.

One or both of the inner tube and the outer tube may have a circular cross-section. However, they may have another cross-sectional shape, such as a rectangle or a hexagon. In this case, the heating element and the thermoelectric device may be both of a planar shape and be accommodated along one or more planar walls of the inner tube.

The housing may have two flow passages (of any shape) alongside one another, forming the first and second flow passages, and the thermoelectric device may be shaped to the profile of a common passage wall that is shared between the two flow passages.

The air inlet may be formed in the outer tube so that a fresh air supply may be drawn from the exterior of the housing through the air inlet.

The thermoelectric device may comprise a first thermoelectric element and a second thermoelectric element, wherein at least a part of the first thermoelectric element is stacked on the second thermoelectric element, with hot side of one thermoelectric element in contact with the cold side of the other thermoelectric element. This arrangement may advantageously provide a greater temperature differential across the thermoelectric device.

Alternatively, or in addition, the thermoelectric device may comprises a first thermoelectric element and a second thermoelectric element adjacent to one another along a wall of the first air flow passage. This arrangement may advantageously allow heat to be simultaneously transferred across a plurality of thermoelectric devices, in a parallel manner.

The rate of heat transfer in the first thermoelectric device may differ to that in the second thermoelectric device, in both stacked configuration or the sequential configuration. This arrangement may advantageously allow a desired heating profile to be adopted and fine- tuned.

The thermoelectric device, or a passage wall shared between first air flow passage and the second air flow passage, or the thermoelectric device and the passage wall, may comprise fins, protrusions, dimples or other surface profiles for improving heat transfer between the air supply in the first air flow passage and the generated aerosol in the second air flow passage, by inducing turbulence thereat.

The aerosol-generating device may further comprise a controller in communication with the thermoelectric device; wherein the controller is configured to control a current supplied to the thermoelectric device so as to control an amount of heat exchanged between the air supply in the first air flow passage and the generated aerosol in the second air flow passage. For example, the controller may supply a predetermined amount of current to the thermoelectric device whenever the heating element is activated, such that a fixed temperature difference is achieved across the thermoelectric device. Alternatively or in addition, the controller may be in communication an air flow sensor and/or temperature sensor positioned in the air flow passage, and the controller may vary the current supplied to the thermoelectric device based on the amount of air flow in the flow channel and/or the temperature of the air supply and/or the generated aerosol.

The heating element may comprise an electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically“conductive” ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum, platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may 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. Alternatively, the electric heaters may comprise an infra-red heating element, a photonic source, or an inductive heating element.

The aerosol-generating device may comprise an internal heating element or an external heating element, or both internal and external heating elements, where “internal” and “external” refer to the aerosol-forming substrate. An internal heater may take any suitable form. For example, an internal heater may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heater may be one or more heating needles or rods that run through the centre of the aerosol-forming substrate. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel- Chromium), platinum, tungsten or alloy wire or a heating plate. The internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heater may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as a ceramic material like Zirconia, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heaters during operation.

An external heater may take any suitable form. For example, an external heater may take the form of one or more flexible heating foils on a dielectric substrate, such as polyimide. The flexible heating foils can be shaped to conform to the perimeter of the substrate receiving cavity. Alternatively, an external heater may take the form of a metallic grid or grids, a flexible printed circuit board, a moulded interconnect device (MID), ceramic heater, flexible carbon fibre heater or may be formed using a coating technique, such as plasma vapour deposition, on a suitable shaped substrate. An external heater may also be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating materials. An external heater formed in this manner may be used to both heat and monitor the temperature of the external heater during operation.

The internal or external heater may comprise a heat sink, or heat reservoir comprising a material capable of absorbing and storing heat and subsequently releasing the heat over time to the aerosol-forming substrate. The heat stored in the heat sink or heat reservoir may be transferred to the aerosol-forming substrate by means of a heat conductor, such as a metallic tube.

During operation an aerosol-forming article containing the aerosol-forming substrate may be partially contained within the aerosol-generating device.

The aerosol-forming article may be substantially cylindrical in shape. The aerosol-forming article may be substantially elongate. The aerosol-forming article may have a length and a circumference substantially perpendicular to the length. The aerosol-forming substrate may be substantially cylindrical in shape. The aerosol-forming substrate may be substantially elongate. The aerosol-forming substrate may also have a length and a circumference substantially perpendicular to the length.

The aerosol-forming article may have a total length between approximately 30 mm and approximately 100 mm. The aerosol-forming article may have an external diameter between approximately 5 mm and approximately 12 mm. The aerosol-forming article may comprise a filter plug. The filter plug may be located at a downstream end of the aerosol-forming article. The filter plug may be a cellulose acetate filter plug. The filter plug is approximately 7 mm in length in one embodiment, but may have a length of between approximately 5 mm to approximately 10 mm.

In one embodiment, the aerosol-forming article has a total length of approximately 45 mm. The aerosol-forming article may have an external diameter of approximately 7.2 mm. Further, the aerosol-forming substrate may have a length of approximately 10 mm. Alternatively, the aerosol-forming substrate may have a length of approximately 12 mm. Further, the diameter of the aerosol-forming substrate may be between approximately 5 mm and approximately 12 mm. The aerosol-forming article may comprise an outer paper wrapper. Further, the aerosol-forming article may comprise a separation between the aerosol-forming substrate and the filter plug. The separation may be approximately 18 mm, but may be in the range of approximately 5 mm to approximately 25 mm.

The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, 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. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former that facilitates the formation of a dense and stable aerosol. 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. 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.

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.

Although reference is made to solid 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 liquid aerosol- forming substrate. If a liquid aerosol-forming substrate is provided, the aerosol-generating device preferably comprises means for retaining the liquid. For example, the liquid aerosol- forming substrate may be retained in a container. Alternatively or in addition, the liquid aerosol-forming substrate may be absorbed into a porous carrier material. The porous carrier material may be made from any suitable absorbent plug or body, for example, a foamed metal or plastics material, polypropylene, terylene, nylon fibres or ceramic. The liquid aerosol-forming substrate may be retained in the porous carrier material prior to use of the aerosol-generating device or alternatively, the liquid aerosol-forming substrate material may be released into the porous carrier material during, or immediately prior to use. For example, the liquid aerosol-forming substrate may be provided in a capsule. The shell of the capsule preferably melts upon heating and releases the liquid aerosol-forming substrate into the porous carrier material. The capsule may contain a solid in combination with the liquid.

Alternatively, the carrier may be a non-woven fabric or fibre bundle into which tobacco components have been incorporated. The non-woven fabric or fibre bundle may comprise, for example, carbon fibres, natural cellulose fibres, or cellulose derivative fibres.

The aerosol-generating device may further comprise a power supply for supplying power to the internal and external heaters. The power supply may be any suitable power supply, for example a DC voltage source such as a battery. In one embodiment, the power supply is a Lithium-ion battery. Alternatively, the power supply may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium-Cobalt, a Lithium-Iron-Phosphate, Lithium Titanate or a Lithium-Polymer battery. In another aspect of the disclosure, there is aerosol generating system comprising the housing of any of the preceding claims and an aerosol-forming article having an aerosol- forming substrate in the cavity of the aerosol-generating device.

In a further aspect of the disclosure, there is provided a method of generating an aerosol from an aerosol-forming substrate comprising: drawing an air supply through a first air flow passage; heating the aerosol-forming substrate to generate an vapour; drawing the air from the first air flow passage and the generated vapour through a second air flow passage; and exchanging heat between the first air flow passage and the second air flow passage using a thermoelectric device.

The step of exchanging heat between the air supply and the generated aerosol may be carried out simultaneously with the step of heating the aerosol-forming substrate. This may advantageously prevent the thermoelectric device from operating when the generated aerosol is not heated by the heating element.

The method may further comprise determining the temperature of the air supply and/or the air and vapour, or generated aerosol, in the second air flow passage. The step of exchanging heat between the air supply and the generated aerosol may be carried out when the determined temperature of the air supply and/or the generated aerosol falls outside a predetermined range. Such on demand heat exchange may advantageously improve the energy efficiency of the aerosol-generating device, since heating and/or cooling only takes place when it is needed.

Although the disclosure has been described by reference to different aspects, it should be clear that features described in relation to one aspect of the disclosure may be applied to the other aspects of the disclosure. In particular, aspects of a device forming part of a system in accordance with one aspect of the invention may be applied to a device alone in accordance with another aspect of the invention.

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is a schematic cross-section diagram of a housing of an aerosol-generating device according to an embodiment of the present invention;

Figure 2 is a schematic cross-section diagram of an aerosol-forming article for use with the housing as shown in Figure 1 ;

Figure 3 is a schematic cross-section diagram showing the aerosol-forming article of Figure 2 being used in the housing of the aerosol generating-device of Figure 1 .

Figure 4 is a schematic cross-section diagram of an aerosol-forming substrate for used with a housing of an aerosol-generating device according to another embodiment of the present invention; Figure 5a is a schematic cross-section diagram showing a plurality of thermoelectric devices in a layered configuration according to another embodiment of the present invention.

Figure 5b is a schematic cross-section diagram showing a plurality of thermoelectric devices in a sequential arrangement according to yet another embodiment of the present invention.

Figure 1 is a schematic cross-section diagram of a housing 10 of an aerosol- generating device. The housing 10 in this particular case is of a tubular shape so as to mimic the exterior profile of a lit-end cigarette. The housing 10 comprising an air inlet 20 opened at a proximal end of its exterior surface, and a cavity 40 having a tubular heating element 30 extended longitudinally along a portion of a cavity wall towards a distal end of the housing 10. The distal end and the proximal end are defined as the two ends of the housing that are respectively further away from and closer to the user when the aerosol-generating device is in use.

The cavity 40 is configured to receive an aerosol-forming article 80, for example a tobacco rod as shown in Figure 2, through an opening 50 at the proximal end of the housing 10. When the aerosol-forming article 80 is inserted into the cavity 40, a consumable portion 82 of the aerosol-forming article 80, i.e. an aerosol-forming substrate 82, comes into thermal proximity with the heating element 30. Typically the aerosol-forming substrate 82 is heated, by the heating element 30, to an operating temperature of between 200 and 350 degrees centigrade to generate an aerosol. The aerosol-forming article 80, in this particular example, further comprises a mouthpiece 84 for drawing generated aerosol through the article and a cellulose acetate filter between the mouthpiece 84 and the aerosol-forming substrate 82. The aerosol-forming substrate 82 is wrapped in a wrapper, for example paper, so as to form a flow channel extending between the two ends of the aerosol-forming article 80.

The housing 10 is connectable to an electrical energy supply (not shown), for example a rechargeable lithium ion battery. A controller (not shown) is connected to the heating element 30, the electrical energy supply and a user interface (not shown), for example a button or display. Upon activating the user interface, the controller controls the power supplied to the heating element 30 in order to regulate the aerosol-forming substrate 82 to the operating temperature. Alternatively or additionally, the device may comprise an air flow sensor, such as a diaphragm actuator. The controller may then control the operation of the heating element based on detected air flow. This allows the heating element 30 to heat up as soon as the air flow sensor detects an attempt by the user to draw the generated aerosol through the housing 10.

The housing 10 comprises a first air flow passage 22 and a second air flow passage extending alongside each other. The first air flow passage 22, responsible for providing an air supply to the heating element 30, is defined between the air inlet 20 and the heating element 30. The second air flow passage 24 comprises the air channel extending between the two ends of the aerosol-forming article 80when it is fully received into the cavity 40 as shown in Figure 3.

The heating element 30 is a resistive heating element that generates heat when a current is passed through it. For example the heater may comprise one or more electrically conductive tracks on a polyimide film. The heating element 30 is positioned along a portion of a cavity wall of the cavity 40, such that when an aerosol-forming article 80 is inserted into the cavity 40 the aerosol-forming substrate 82 comes into thermal proximity with the heating element 30. More specifically, the heating element 30 is sized and positioned corresponding to a consumable portion 82 of the aerosol-forming article 80 as received in the cavity 40, such that in use the whole or parts of consumable portion 82 can be heated to an operating temperature so as to generate an aerosol.

In use, a user puffs on the mouthpiece 84 of the aerosol-forming article 80 to draw an air supply 90 into the housing 10 through the air inlet 20. The air supply 90 passes through the first airflow passage 22 towards the distal end of the housing before entering the aerosol- forming article 80 at its distal end. The air then flows through the aerosol-forming substrate 82 towards the mouthpiece. As the air supply 90 flows through the aerosol-forming substrate 82, it mixes with condensed droplets to form a generated aerosol 94, before being drawn out through the mouthpiece 84. Without adequate heat dissipation, the generated aerosol 94 may be reach the mouthpiece 84 at a temperature that is higher than desirable. A hot aerosol may cause discomfort for the user and may not be satisfying for the user.

To mitigate this, the housing 10 further comprises a thermoelectric device 60, in this example a Peltier device, positioned between a portion of the first air flow passage 22 and the second air flow passage 24. The thermoelectric device 60 is positioned such that it has a heating first surface 62 in contact with the cooler air supply 90 and a cooling second surface 64 in contact with the aerosol-forming article for cooling the generated aerosol 94. In this embodiment, the thermoelectric device 60 is controlled by the controller, such that upon activation of the heating element 30 an electrical current is applied across the thermoelectric device 60, thereby creating a temperature difference between the first surface 62 and the second surface 64. The controller ensures the thermoelectric device 60 is only switched on when the auxiliary air stream 94 in the first air flow channel 22 is heated. Thus, heat energy is transferred from the warmer generated aerosol 94 to the cooler air supply 90 through the thermoelectric device. Not only is the generated aerosol 94 at the mouthpiece 84 cooled to a lower temperature, but the air supply 90 prior to being heated at the heating element 30 is also preheated. A preheated air supply 90 requires the heating element 30 to provide less heat to the aerosol-forming substrate 80 to raise it to the operating temperature in comparison to an ambient air supply. The heating element can be raised to a lower maximum temperature and still generate a desirable aerosol. This arrangement also allows the generated aerosol 94 to be exhausted at the mouthpiece 84 at a lowered temperature. A lowered temperature ensures that the aerosol droplets are condensed and fully formed as they exhaust at the mouthpiece, thus improving the user’s experience.

In some embodiments, the thermoelectric device 60 is switched on only if the temperature of the generated aerosol 94 rises above a given threshold, thus conserving energy consumed and prolonging battery life. The aerosol temperature can be monitored directly using a suitable thermometer. Alternatively, the thermoelectric device 60 may be activated only if the heating element 30 has been operating for a set period of time and/or if the power supplied to the heating element 30 exceeds a threshold. The temperature in the generated aerosol 94 can be predicted based on the amount of heating that has already been applied.

In some embodiments, the power supplied to the thermoelectric device 60 is adjusted based on measured temperature or other variables. The more current supplied to the thermoelectric device 60, the larger the amount of heat that can be transferred across said thermoelectric device 60. The current as supplied to the thermoelectric device 60 can be adjusted by varying the amplitude of the electrical current, or alternatively, the current may be supplied as a pulses with variable frequency.

As shown in Figure 1 , the thermoelectric device 60 is sealingly mounted in the cavity 40 across an opening in the cavity wall. In other words, the thermoelectric device 60 forms a portion of the cavity wall.

In order to induce turbulence in the air supply 90 and to maximise contact between the air supply 90 and the heating first surface 62 of the thermoelectric device 60, the first air flow passage 22 is provided with a protrusion 26 in the vicinity of the thermoelectric device 60. The incoming air supply 90 is drawn towards the thermoelectric device 60, as shown the air flow path in Figure 3. Additionally or alternatively, fins, dimples and aerofoils are provided in the proximity of, or directly, on the first surface 62 of the thermoelectric device 60 so as to induce turbulence in the passing air flow for improving heat transfer.

Figure 4 shows another embodiment according to the present invention. In Figure 4, a heater assembly comprising an internal heating element 30b is used as an alternative to the external tubular heating element 30 for heating the aerosol-forming substrate. The internal heating element 30b is a blade shaped element that penetrates into the aerosol- forming substrate as the aerosol-forming article 80 is inserted into the cavity 40.

The internal electrical heater 30b comprises an electrically insulating substrate and at least one resistive heating element formed on the electrically insulating substrate. Preferably a plurality of resistive heating elements are connected, in parallel arrangement, to the heating supply. The internal electrical heater 30b is mounted on and extends through a bushing 32 at the distal end of the housing. An electrical connection 34 is provided at the elongated electrical heater 30b for connecting to a power supply.

Similar to the embodiments shown in Figure 3, in use the air supply 90 passes through the first air flow passage 22 towards the distal end of the housing before entering the aerosol- forming article 80 at its distal end. The air then flows through the aerosol-forming substrate 82, alongside the internal heating element 30b. As the air flows through the aerosol-forming substrate 82, it mixes with condensed droplets to form a generated aerosol 94. The generated aerosol is further cooled by the thermoelectric element 60 before being drawn out through the mouthpiece 84

The thermoelectric device 60 may comprise a plurality of thermoelectric devices 60a, 60b arranged adjacent to each other in a variety of orientations. In this way an increase in overall cooling capacity may be provided. A combination of different types of thermoelectric elements can be used. As shown in Figure 5a, two thermoelectric devices 60a, 60b are provided in a stacked configuration. A first thermoelectric device 60a overlies a second thermoelectric device 60b. The second thermoelectric device 60b comprises a cooling second surface 64b in contact with the surface of aerosol-forming article 80, and a heating first surface 62b in contact with a corresponding cooling second surface 64a of the first thermoelectric device 60a. The first thermoelectric device 60a comprises a heating first surface 62a in contact with the air supply 90 in the first air flow passage 22. In use, heat from the generated aerosol 94 is transferred across both the second thermoelectric device 60b and the first thermoelectric device 60a to dissipate into the air supply 90, through the contacting surfaces between the second thermoelectric device 60b and the first thermoelectric device 60a. This allows an increased temperature difference across the thermoelectric devices (between the hot side and the cold side of the thermoelectric devices) for a given current. Heat transfer through such contacting surface may be enhanced by a heat transfer aid, e.g. a thermal conducting paste.

In Figure 5b, two thermoelectric devices 60c, 60d are sequentially provided in the direction of air flow. In this case, the two thermoelectric devices 60c, 60d may be different types of the thermoelectric devices. For example, the two thermoelectric devices 60c, 60d can have different ratings, efficiencies, thicknesses or constructions. The upstream thermoelectric device 60c that is closest to heating element 30 and is in contact with the hottest of the generated aerosol 94, may be a better rated or more efficient device (providing a greater temperature difference between the hot and cold sides of the thermoelectric device) than the downstream thermoelectric device 60d. This widens the temperature difference at the surface of the upstream thermoelectric device 60c and the hot generated aerosol 94, thus improving heat transfer efficiency. In contrast, a lower rated (less powerful) downstream thermoelectric device 60d may be used for further cooling the cooled generated aerosol 94. In some embodiments, the two thermoelectric devices 60c, 60d are identical. In that case, they can be selectively operated depending on the degree of cooling required. For example, only one of the two thermoelectric devices 60c, 60d may switch on when the type of aerosol-forming substrate 80 requires heating at a lower temperature. In that case, less cooling is required to cool the generated aerosol 94. The amount of cooling provided can be based on ambient temperature. Furthermore, selective cooling at different sites along the second air flow passage allows aerosol to form at desirable location.

In the embodiments shown in Figures 1 , 3 and 4, the housing 10 is providing with an additional air inlet 28 opened at the distal end of the housing 10. The provision of said additional air inlet 28 allows an additional air supply 96 to supplement the air supply 94 if needed. This may be required to provide a particular resistance to draw or a particular temperature within the aerosol-forming substrate.

Additionally, the housing 10 may comprise an air flow control valve (not shown) for controlling the amount of additional air supply 96 being drawn in at the additional air inlet 28. This advantageously allows the balance between the air supply 94 and the additional air supply 96 to be controlled, providing an additional means of controlling the air supply temperature at the heating element 30.

The exemplary embodiments described above illustrate but are not limiting. In view of the above discussed exemplary embodiments, other embodiments consistent with the above exemplary embodiments will now be apparent to one of ordinary skill in the art.