Heating chamber for an aerosol generating device

Abstract

Heating Chamber for an Aerosol Generating Device A method (300) of manufacturing a heating chamber for an aerosol generating device is disclosed. The method comprising: providing (302) a tube comprising a wall (202) which defines a cavity (206) for receiving an aerosol generating substrate through an opening (208) of the tube; depositing (304) a dielectric coating (210) to the tube in a continuous layer such that the continuous layer extends over an inner surface (201) of the wall and an outer surface (203) of the wall; and attaching (306) a heating element (212) to the outer surface of the coated tube.

Description

[0001] HEATING CHAMBER FOR AN AEROSOL GENERATING DEVICE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an aerosol generating device, and a method of manufacturing a heating chamber for the aerosol generating device. The disclosure is particularly applicable to a portable aerosol generation device, which may be self-contained and low temperature. Such devices may heat, rather than bum, tobacco or other suitable aerosol substrate materials by conduction, convection, and / or radiation, to generate an aerosol for inhalation.

[0004] BACKGROUND

[0005] The popularity and use of reduced-risk or modified-risk devices (also known as vaporisers) has grown rapidly in the past few years as an aid to assist habitual smokers wishing to quit using traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm aerosolisable substances as opposed to burning tobacco in conventional tobacco products.

[0006] A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn (HNB) device. Devices of this type generate an aerosol or vapour by heating an aerosol substrate (i.e. consumable) that typically comprises moist leaf tobacco or other suitable aerosolisable material to a temperature typically in the range 150°C to 300°C. Heating an aerosol substrate, but not combusting or burning it, releases an aerosol that comprises the components sought by the user but not the undesirable by-products of combustion. In addition, the aerosol produced by heating the tobacco or other aerosolisable material does not typically comprise the burnt or bitter taste that may result from combustion that can be unpleasant for the user.

[0007] The aerosol substrate is generally inserted into a cup. The cup is arranged so that its interior can be accessed from the outside. The cup has on its periphery a means of heating the substrate. Using those means, the cup is capable transferring heat from the means of heating it to the material housed inside it. Accordingly, the material housed in the cup, that is, the consumable, is heated and thus vaporised. A user then inhales the vapour that is generated by the heating of the consumable.

[0008] In the prior art, a stainless-steel material is typically used to make such cups. These cups have a thin film heater wrapped around the outside of the cup to heat up the stainless steel. The heat is then conducted to the consumable.

[0009] Such a way of attaching and heating up the cup is rather effective for heat conduction. However, it is less effective for heat radiation, which is another significant method of heat transfer in particular to the aerosol generating substance. Thermal radiation can be expressed through the Stefan-Boltzmann law which contains a value £ for emissivity, that is j*=eoT4

[0010] Here, j* refers to the total energy emitted per unit surface area of a black body across all wavelengths per unit time, o is the Stefan-Boltzmann constant, and T is the temperature of the black body. The emissivity £ is a number between 0 and 1 where 1 would be a perfect black body radiator of heat and 0 would be the opposite.

[0011] In order to have as efficient a heat transfer by thermal radiation as possible, the surface of the cup should have a value close to 1 . However, known heater cups having a wall thickness of around 0.08 mm are made of stainless steel of grade 316L, which has a value of £ of 0.26 which is unsatisfactory.

[0012] An object of the present invention is therefore to optimise the thermal efficiency and the manufacturing of heating chambers in heat-not-burn devices whilst also ensuring a reliable operation of the device.

[0013] SUMMARY OF INVENTION

[0014] According to an aspect of the invention there is provided a method of manufacturing a heating chamber for an aerosol generating device, the method comprising: providing a tube comprising a wall which defines a cavity for receiving an aerosol generating substrate through an opening of the tube; depositing a dielectric coating to the tube in a continuous layer such that the continuous layer extends over an inner surface of the wall and an outer surface of the wall; and attaching a heating element to the outer surface of the coated tube.

[0015] In this way, the manufacturing process of the heating chamber is advantageously simplified by applying the dielectric coating to both the outer surface and the inner surface of the wall in a continuous way. The dielectric coating is deposited across the open end of the wall (i.e. at the position of the opening of the wall) such that the dielectric coating layer is continuously coated across the inner and outer surfaces.

[0016] The dielectric coating that is applied to the wall is applied to as to increase the thermal emissivity of the surface of the wall, where the dielectric coating helps the wall material to absorb heat from the heat source (i.e. the heating element) as well as radiate the absorbed heat out. The dielectric coating may be a ceramic and / or glass-like coating. Preferably, the wall is thermally conductive. Preferably, the wall is electrically conductive. As will be appreciated, the wall may comprise a metallic material such as stainless steel SS316L.

[0017] Heat transfer from the heating element to the wall mainly takes place by conduction. Therefore, a dielectric coating on the outer surface of the wall further acts as an electrically insulating layer between the heating element and the wall. Heat in the wall is transferred to a received aerosol generating substrate by conduction and radiation.

[0018] Preferably, the dielectric coating is deposited in a single deposition process. In this way, the wall is coated in a single step and the manufacturing process is further optimised.

[0019] Preferably, depositing the dielectric coating comprises coating the entire outer surface of the wall. In this way, the thermal emissivity of the entire outer surface of the wall is increased such that heat generated by the heating element is optimally absorbed into the wall to be further radiated out toward a consumable received in the cavity.

[0020] Preferably, depositing the dielectric coating comprises coating the entire inner surface of the wall. In this way, heat in the wall may be effectively radiated and transferred into a received consumable.

[0021] Preferably, the method further comprises providing a base wall at an end of the tube, and wherein depositing the dielectric coating comprises coating at least an inner surface of the base wall, and preferably an outer surface of the base wall. In this way, the thermal emissivity of the heating chamber may be further increased. As will be appreciated, the opening may be positioned at a first end of the tube and the base wall may be positioned at a second end of the tube.

[0022] Preferably, attaching the heating element comprises printing a heater track onto the coated outer surface of the wall. The heating element may comprise one or more heater tracks. In this way, the manufacturing process is simplified since the heating element is directly applied onto the dielectric coating.

[0023] Preferably, attaching the heating element comprises: providing a thin film heater comprising the heating element and a flexible backing film on which the heating element is supported; and attaching the thin film heater to the coated outer surface of the wall with the heating element against the dielectric coating. In this way, a compact heating chamber is produced without compromising on thermal or electrical properties.

[0024] Preferably, the flexible backing film comprises polyimide or poly ether ketone (PEEK). PEEK is a highly temperature resistant material, which is ideal for use in components arranged near a source of heat. When used in components directly in contact with the heating components, PEEK reduces the heat conduction to other components in the device.

[0025] Preferably, depositing the dielectric coating comprises using at least one of: a vacuum deposition technique; or a thermal spray technique. In this way, plasma enhanced chemical vapour deposition allows for the use of lower film formation temperatures, more even film thickness, and the improved ability to form film layers with a three-dimensional structure. A thermal spray technique or process may also be used, such as a plasma arc coating or plasma spray coating technique, or sputtering. Such techniques can effectively deposit ceramic coatings which may have higher melting temperatures.

[0026] Preferably, the dielectric coating comprises at least one of: hydrogenated amorphous silicon (a-Si:H); a carbon-based coating; a ceramic material; silicon carbide; aluminium-titania; aluminium chromium nitride (e.g. AICrN-based coatings); or aluminium nitride.

[0027] Examples of carbon-based coatings may include a mixture of carbon and metal (such as tungsten carbide I carbon (WC / C)), the carbon may be diamond-like carbon. Carbon-based coatings are biocompatible and suitable for aerosol generating applications. Carbon-based coatings typically also have low friction coefficients which advantageously allow aerosol generating substrates I consumables to be readily received into the heating chamber.

[0028] Preferably, the thickness of the applied dielectric coating is between 0.3 pm and 10 pm, preferably between 0.3 pm and 5 pm. In this way, the heat-up times of the tube and overall energy efficiency of the heating chamber is optimised. The coating should be thin so as to reduce the time for coating application and also reduce the thickness of the material through which heat is to be transported, thereby improving the heat transfer efficiency.

[0029] Preferably, the wall comprises a thermally conductive material. Preferably, the wall comprises an electrically conductive material.

[0030] According to another aspect of the invention, there is provided a heating chamber for an aerosol generating device manufactured according to the first aspect, wherein the heating chamber comprises a dielectric coating in a continuous layer that extends over an inner surface and an outer surface of a wall of a tube which defines a cavity for receiving an aerosol generating substrate. According to yet another aspect of the invention, there is provided an aerosol generating device comprising the heating chamber according to the second aspect, wherein the heating chamber comprises a dielectric coating in a continuous layer that extends over an inner surface and an outer surface of a wall of a tube which defines a cavity for receiving an aerosol generating substrate.

[0031] BRIEF DESCRIPTION OF DRAWINGS

[0032] Embodiments of the invention are now described, by way of example, with reference to the drawings, in which:

[0033] Figure 1 is an exemplary aerosol generating device according the invention;

[0034] Figure 2 is a schematic cross-sectional view of a heating chamber according the invention; and

[0035] Figure 3 is a flow diagram showing method steps for manufacturing the heating chamber according to an embodiment of the invention.

[0036] DETAILED DESCRIPTION

[0037] As described herein, a vapour is generally understood to refer to a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour can be condensed to a liquid by increasing its pressure without reducing the temperature, whereas an aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. It should, however, be noted that the terms ‘aerosol’ and ‘vapour’ may be used interchangeably in this specification, particularly with regard to the form of the inhalable medium that is generated for inhalation by a user.

[0038] Figure 1 illustrates an aerosol generating device 100 according to an embodiment of the invention. The aerosol generating device 100 is illustrated in an assembled configuration with the internal components visible. The aerosol generating device 100 is a heat-not-burn device, which may also be referred to as a tobacco-vapour device, and comprises a heating chamber 150 configured to receive an aerosol generating substrate such as a tobacco rod. The heating chamber 150 is operable to heat, but not bum, a rod of aerosol generating material to produce a vapour or aerosol for inhalation by a user. As will be appreciated, the aerosol generating device 100 depicted in Figure 1 is simply an exemplary aerosol generating device according to the invention. Other types and configurations of tobacco-vapour products, vaporisers, or electronic cigarettes may also be used as the aerosol generating device according to the invention.

[0039] Figure 2 shows a heating chamber 200 according to the present invention. The heating chamber 200 comprises a wall 202 in tubular form and a base wall 204 is shaped to form a heater cup having a cavity 206 which is configured to receive the aerosol generating substrate through an opening 208 at a top end of the heating chamber 200.

[0040] The wall 202 is in a tubular, e.g. cylindrical, form, but as will be appreciated may comprise other shapes, such as cuboidal. In use, an aerosol generating substrate is received within the cavity 206 of the heating chamber 200 and interfaces with an inner surface 201 of the wall 202. The length of the wall 202 may be configured such that a mouthpiece portion of the aerosol generating substrate extends out of the cavity 206 from the opening 208 to be received in the mouth of a user for inhalation. The wall 202 and base wall 204 is made of a thermally conductive material, such as steel or stainless steel, that allows for heat transfer to an aerosol generating substrate received in the cavity 206 while maintaining sufficient structural stability under temperature stress. As will be appreciated by the skilled person, a metallic material, or steel or stainless steel is electrically conductive. Both the inner surface 201 and the outer surface 203 of the wall 202 and the base wall 204 are coated with a continuous layer of ceramic and / or glasslike coating 210, wherein the coating 210 has a high thermal emissivity so as to, in use, enhance heat transfer from a heating element 212 of the heating chamber 200 to the wall 202 (and base wall 204) and from the wall 202 (and base wall 204) to the aerosol generating substrate received in the cavity 206. In order to deposit the coating 210 in a continuous layer across both the inner and outer surfaces of the wall 202 the open end 205 of the wall 202, i.e. at the opening 208 of the heater cup, is also coated with the coating 210.

[0041] In this specific example in Figure 2, the entire surface, i.e. both inner and outer surfaces, of the wall 202 and the base wall 204 is coated. In further examples, a portion of the outer surface of the wall and a portion of the inner surface of the wall may be coated with the dielectric coating 210, where the continuity between the outer surface coating and the inner surface coating is provided by applying the dielectric coating 210 across at least a portion of the open end 205 of the wall 202.

[0042] The coating 210 is also electrically insulating, i.e. to act as a dielectric barrier to the wall I base wall. In this example the heating element is a resistive heater and since the coating 210 is electrically insulating, i.e. a dielectric coating, the heating element 212 is separated from the wall 202. For example, the coating 210 may comprise silicon carbide or aluminium nitride.

[0043] The coating 210 has a thickness between 0.3 pm and 10 pm and may be deposited using vacuum deposition, such as chemical vapour deposition or physical vapour deposition. As will be appreciated, the thickness of the coating 210 may be varied across the wall 202 and / or the base wall 204. For example, the thickness of the coating 210 on at least a portion of the outer surface of the wall 202 may be thicker than other portions of the outer surface of the wall 202 or the coating 210 on the inner surface of the wall 202, since the coating on the outer surface is required to act as an electrically insulating layer between the heating element 212 and the wall 202. The thickness of the coating 210 on the inner surface may be different, e.g. thinner than the coating on the outer surface, as will be appreciated by the skilled person to improve the overall energy efficiency of the heating chamber 200.

[0044] The heating element 212 comprises one or more heater tracks that are directly printed onto the coating 210 around the outer circumference of the coating 210 on the outer surface of the wall 202. The heating element 212 comprises a heating material suitable for converting electrical energy into heat (such as stainless steel, titanium, nickel, nichrome, nickel-based alloys, silver, ...). In use, power may be supplied to the heating element 212 from a power source such as a battery (not shown) such that the temperature of the heating element 212 increases and heat energy is transferred across the coating 210 to the wall 202.

[0045] Alternatively (not shown), the heating element 212 may be part of a thin film heater, where the thin film heater further comprises a flexible backing film on which the heating element 212 is mounted before the thin film heater is applied onto the coating 210. The flexible backing film may comprise a flexible material preferably having a high dielectric capability and low thermal mass, such as polyamide or polyetheretherketon (PEEK). The thin film heater may be wrapped around the wall 202 in a circumferential direction such that the heating element 212 lies adjacent to (i.e. , abuts, contacts) the coating 210. As explained above, the coating 210 acts as a separation between the heating element 212 and the wall 202 such that a contact between the heating element 212 and the wall 202 is prevented.

[0046] The heating element 212, whether directly printed onto the coating 210 or applied as a thin film heater, is positioned along the longitudinal axis of the wall 202 to correspond with a tobacco or aerosol generating material portion of an aerosol generating substrate received in the cavity 206. In this way, distance of heat transfer, e.g. conduction, from the heating element 212 to the aerosol generating material in a received consumable is minimised and the thermal efficiency of the heating chamber 200 is optimised.

[0047] Figure 3 illustrates a flow chart which is a method 300 of manufacturing a heating chamber according to an embodiment of the invention.

[0048] The method 300 begins at step 302, wherein a heating chamber comprising a wall in the form of a tube and an opening for receiving an aerosol substrate within the heating chamber is provided.

[0049] At step 304, the wall is treated with a dielectric material by applying a coating of the dielectric material in a continuous way to the both the inner surface of the wall and the outer surface of the wall, such that a continuous layer of dielectric material is deposited across the inner and outer surfaces of the thermal conductive wall. In order to coat both inner and outer surfaces with a continuous layer of dielectric material, the coating will also be applied across at least a portion of the top end of the wall (i.e. across the end of the wall at the opening of the tube).

[0050] The coating may be deposited by vacuum deposition below atmospheric pressure, i.e. vacuum. For example, the layer of dielectric material may be deposited using chemical vapour deposition. However, in some examples, the layer of dielectric material may be deposited using physical vapour deposition.

[0051] Chemical vapour deposition is a technique in which a substrate is exposed to one or more volatile precursors in a vacuum (or low-pressure plasma) environment, which react and / or decompose on a surface of the substrate to produce a thin film deposit. In this case, the substrate is the wall and the layer of dielectric material is the thin film deposit.

[0052] In some embodiments, plasma enhanced vapour deposition may be used to form the layer of dielectric material. Plasma enhanced vapour deposition utilizes a plasma to provide some of the energy which is required for the deposition reaction to occur. In particular, deposition is achieved by introducing reactant gases between parallel electrodes, wherein a capacitive coupling between the electrodes excites the reactant gases into a plasma. This induces a chemical reaction and results in the reaction product (i.e. the dielectric material) being deposited on the substrate (i.e. the wall). Advantageously, plasma enhanced vapour deposition takes place at lower temperatures than other chemical vapour deposition techniques.

[0053] In one example, a radio frequency electrical discharge between two electrodes may be used to create a plasma from a carrier gas comprising CH4. The resultant chemical reaction deposits a thin film comprising diamond or diamond-like-carbon (DLC) on the wall. The thin film corresponds to the layer of dielectric material.

[0054] In another example, a microwave frequency electrical discharge between two electrodes may be used to excite oxygen to form a plasma. A mixture of silane (SiH4) diluted in a carrier gas, such as argon, is then introduced in an afterglow of the plasma. For example, a mixture of 5% silane in argon may be introduced. The resultant chemical reaction deposits a thin film comprising silicon oxide (e.g. silicon dioxide) on the wall. The thin film corresponds to the layer of dielectric material. For example, the deposited thin film may comprise a functionalized silica-like coating. The deposition process is continued until a desired thickness of the layer of dielectric material is deposited, e.g. between 0.3 pm and 10 pm.

[0055] At step 306, a heating element is attached to the outer surface of the coated heating chamber. The heating element may comprise one or more heater tracks that are directly printed onto the coated surface, or alternatively the heating element may be part of a thin film heater that is applied to the coated outer surface.

Claims

CLAIMS1 . A method of manufacturing a heating chamber for an aerosol generating device, the method comprising: providing a tube comprising a wall which defines a cavity for receiving an aerosol generating substrate through an opening of the tube; depositing a dielectric coating to the tube in a continuous layer such that the continuous layer extends over an inner surface of the wall and an outer surface of the wall; and attaching a heating element to the outer surface of the coated tube.

2. The method of claim 1 , wherein the dielectric coating is deposited in a single deposition process.

3. The method of claim 1 or claim 2, wherein depositing the dielectric coating comprises coating the entire outer surface of the wall.

4. The method of any preceding claim, wherein depositing the dielectric coating comprises coating the entire inner surface of the wall.

5. The method of any preceding claim further comprising: providing a base wall at an end of the tube, and wherein depositing the dielectric coating comprises coating at least an inner surface of the base wall, and preferably an outer surface of the base wall.

6. The method of any preceding claim, wherein attaching the heating element comprises printing a heater track onto the coated outer surface of the wall.

7. The method of any of claims 1 to 5, wherein attaching the heating element comprises: providing a thin film heater comprising the heating element and a flexible backing film on which the heating element is supported; and attaching the thin film heater to the coated outer surface of the wall with the heating element against the dielectric coating.

8. The method of claim 7, wherein the flexible backing film comprises polyimide or poly ether ketone (PEEK).

9. The method of any preceding claim, wherein depositing the dielectric coating comprises using at least one of: a vacuum deposition technique; or a thermal spray technique.

10. The method of any preceding claim, wherein the dielectric coating comprises at least one of: hydrogenated amorphous silicon (a-Si:H); a carbon-based coating; a ceramic material; silicon carbide; aluminium-titania; aluminium chromium nitride; or aluminium nitride.11 . The method of any preceding claim, wherein the thickness of the applied dielectric coating is between 0.3 pm and 10 pm, preferably between 0.3 pm and 5 pm.

12. The method of any preceding claim, wherein the wall comprises a thermally conductive material.

13. The method of any preceding claim, wherein the wall comprises an electrically conductive material.

14. A heating chamber for an aerosol generating device manufactured by the method of any preceding claim, wherein the heating chamber comprises a dielectric coating deposited in a continuous layer that extends over an inner surface and an outer surface of a wall of a tube which defines a cavity for receiving an aerosol generating substrate.

15. An aerosol generating device comprising the heating chamber of claim 14, wherein the heating chamber comprises a dielectric coating deposited in acontinuous layer that extends over an inner surface and an outer surface of a wall of a tube which defines a cavity for receiving an aerosol generating substrate.

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