Patent Description:
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.

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 <NUM> to <NUM>. 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.

Within known heat-not-burn devices, it is desirable to improve the efficiency of the heating process, whilst also ensuring a reliable operation of the device.

<CIT> discloses a side-by-side segmented heating structure for heating a smoke-emitting medium to emit smoke and a low-temperature smoking appliance therefor. <CIT> discloses a mechanical atomizer with a vibrating mesh.

According to a first aspect of the invention, there is provided a method of manufacturing a heating chamber for an aerosol generating device, as set out in appended claim <NUM>, the method comprising: providing a heating chamber comprising a thermally conductive shell and an opening for receiving an aerosol substrate within the heating chamber; depositing a layer of electrically insulating material onto an outer surface of the thermally conductive shell of the heating chamber using vacuum deposition; and attaching a heating element to the heating chamber such that the heating element is in contact with the layer of electrically insulating material, wherein the layer of electrically insulating material prevents any contact between the heating element and the thermally conductive shell.

In this way, a more efficient heating assembly is provided compared with known aerosol generating devices. The use of vacuum deposition allows for a very thin and uniform layer of electrically insulating material to be deposited between the thermally conductive shell and the heating element. Vacuum deposition further allows for materials to be deposited which have a high electric break down voltage but also a high thermal conductivity to ensure efficient heat transfer through the layer of electrically insulating material to the heating chamber. The arrangement and properties of the electrically insulating material layer acts to prevent a short circuit between the thermally conductive shell and the heating element, and the reduced thickness of the electrically insulating material layer optimises the thermal energy transfer to the thermally conductive shell. Hence, the method of manufacturing provides a heating chamber for an aerosol generating device that is able to operate with improved efficiency and reliability. The step of depositing a layer of electrically insulating material onto an outer surface of the thermally conductive shell of the heating chamber using vacuum deposition may comprise depositing the layer with one or both of physical vapour deposition and chemical vapour deposition.

Preferably, the method comprises depositing the layer of electrically insulating material using chemical vapour deposition. In this way, the layer of electrically insulating material may be deposited having a high purity and density. Moreover, chemical vapour deposition allows for the deposition of electrically insulating material with an even thickness across the surface of the thermally conductive shell, thereby ensuring consistent thermal and electrical properties across the layer.

Preferably, the electrically insulating material comprises at least one of: silicon oxide; diamond; and diamond-like carbon (DLC). In this way, the layer of electrically insulating material separating the thermally conductive shell and the heating element has a high electrical breakdown voltage and a high thermal conductivity. This further reduces the likelihood of a short circuit occurring between the thermally conductive shell and the heating element and also improves the efficiency of thermal energy transfer to the thermally conductive shell. In one example, the electrically insulating layer may comprise a functionalized silica-like coating, e.g. a-SiOX:CHY, which may be referred to as Dursan™.

Preferably, the thickness of the layer of electrically insulating material is between <NUM> and <NUM>. For example, the thickness of the deposited layer of electrically insulating material may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In particular, the layer of electrically insulating material comprising a-SiOX:CHY preferably has a thickness of between <NUM> and <NUM>.

The method further 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 heating chamber with the heating element against the layer of electrically insulating material. In this way, a compact heating chamber is produced without compromising on thermal or electrical properties.

The backing film comprises polyimide or polyether 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.

Preferably, the heating chamber is a tubular heating chamber comprising a tubular thermally conductive shell. In one embodiment, the method comprises wrapping the heating element around the heating chamber with the heating element against the layer of electrically insulating material. In another embodiment, the method comprises wrapping the thin film heater around the heating chamber with the heating element against the layer of electrically insulating material.

Preferably, the method further comprises: wrapping a heat shrink film around the heating chamber to secure the heating element to the heating chamber. In this way, the heating element is ensured to remain in contact with the heating chamber, whilst also maintaining a compact arrangement of the heating assembly.

Preferably, the method further comprises: depositing the layer of electrically insulating material using plasma enhanced chemical vapour deposition. 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.

Preferably, depositing the layer of electrically insulating material using plasma enhanced chemical vapour deposition comprises using a radio frequency electrical excitation source and a carrier gas comprising CH<NUM> to deposit a thin film comprising diamond-like-carbon, DLC, or diamond.

Preferably, depositing the layer of electrically insulating material using plasma enhanced chemical vapour deposition comprises using a microwave frequency electrical excitation source and a carrier gas comprising silane to deposit a thin film comprising silicon oxide, e.g. silicon dioxide or a-SiOX:CHY.

According to a second aspect of the invention, there is provided a heating chamber for an aerosol generating device manufactured by the method of the first aspect, as set out in appended claim <NUM>.

According to a third aspect of the invention, there is provided an aerosol generating device comprising the heating chamber of the second aspect, as set out in appended claim <NUM>.

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

<FIG> illustrates an aerosol generating device <NUM> according to an embodiment of the invention. The aerosol generating device <NUM> is illustrated in an assembled configuration with the internal components visible. The aerosol generating device <NUM> is a heat-not-burn device, which may also be referred to as a tobacco-vapour device, and comprises a heating chamber <NUM> configured to receive an aerosol substrate such as a rod of aerosol generating material, e.g. tobacco. The heating chamber <NUM> is operable to heat, but not burn, the rod of aerosol generating material to produce a vapour or aerosol for inhalation by a user. Of course, the skilled person will appreciate that the aerosol generating device <NUM> depicted in <FIG> 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.

<FIG> shows a cross-sectional view of a heating chamber <NUM> according to an embodiment of the invention. The heating chamber <NUM> comprises a thermally conductive shell <NUM> configured to hold an aerosol substrate (also referred to as a consumable) therein. In particular, the thermally conductive shell <NUM> defines a cylindrical cavity in which a rod of aerosol substrate may be positioned. The thermally conductive shell <NUM> is tubular, e.g. cylindrical, and has an opening <NUM> positioned at a longitudinal end of the thermally conductive shell <NUM>. In use, the user may insert the aerosol substrate through the opening <NUM> in the heating chamber <NUM> such that the aerosol substrate is positioned within the heating chamber <NUM> and interfaces with an inner surface <NUM> of the thermally conductive shell <NUM>. The length of the thermally conductive shell <NUM> may be configured such that a portion of the aerosol substrate protrudes through the opening <NUM> in the thermally conductive shell <NUM> (i.e. out of the heating chamber <NUM>) and can be received in the mouth of the user.

The thermally conductive shell <NUM> preferably comprises a material that allows for efficient heat transfer through a side wall of the thermally conductive shell <NUM> to the aerosol substrate while maintaining sufficient structural stability. Examples of such materials include steel or stainless steel.

The skilled person will appreciate that the heating chamber <NUM> (and thermally conductive shell <NUM>) is not limited to being tubular. For example, the thermally conductive shell <NUM> may be formed as a cuboidal, conical, hemi-spherical or other shaped cavity, and be configured to receive a complementary shaped aerosol substrate. Moreover, in some embodiments, the thermally conductive shell <NUM> may not entirely surround the aerosol substrate, but instead only contact a limited area of the aerosol substrate.

A layer of electrically insulating material <NUM> surrounds an outer surface <NUM> of the thermally conductive shell <NUM>. In particular, the layer of electrically insulating material <NUM> lies adjacent to (i.e. abuts, contacts) the circumferential outer surface <NUM> of the thermally conductive shell <NUM>. In <FIG>, the layer of electrically insulating material <NUM> is depicted as extending along the entire length of the outer surface <NUM> of the thermally conductive shell <NUM>. However, the skilled person will appreciate that, in other embodiments, the layer of electrically insulating material <NUM> may only extend along a portion of the length of the thermally conductive shell <NUM>.

The layer of electrically insulating material <NUM> is deposited using a vacuum deposition technique, and preferably using chemical vapour deposition or plasma enhanced chemical vapour deposition. Thus, the layer of electrically insulating material <NUM> may be deposited as thin layer, e.g. between <NUM> and <NUM>, whilst also exhibiting a high purity and homogeneity.

A thin film heater <NUM> surrounds the layer of electrically insulating material <NUM>. The thin film heater <NUM> comprises a heating element <NUM> that is mounted on a flexible backing film <NUM>. The heating element <NUM> may comprise one or more heater tracks extending across a surface of the flexible backing film <NUM>. The heating element <NUM> comprises a heating material suitable for converting electrical energy into heat (such as stainless steel, titanium, nickel, Nichrome, nickel based alloy, silver etc.). In use, power may be supplied to the heating element <NUM> from a power source such as a battery (not depicted) such that the temperature of the heating element <NUM> increases and heat energy is transferred across the layer of electrically insulating material <NUM> to the thermally conductive shell <NUM>. The aerosol substrate received within the heating chamber <NUM> is conductively heated by the thermally conductive shell <NUM> to produce an aerosol for inhalation by the user.

The flexible backing film <NUM> comprises a flexible material preferably having a high dielectric capability and low thermal mass, such as polyimide or polyether ether ketone (PEEK).

The thin film heater <NUM> is wrapped around the heating chamber <NUM> in a circumferential direction such that the heating element <NUM> lies adjacent to (i.e. abuts, contacts) the layer of electrically insulating material <NUM>. That is, the layer of electrically insulating material <NUM> acts as a barrier to separate the heating element <NUM> and the thermal conductive shell <NUM> such that contact between the heating element <NUM> and the thermally conductive shell <NUM> is prevented. The flexible backing film <NUM> lies on an opposing side of the heating element <NUM> to the layer of electrically insulating material <NUM>, i.e. the heating element <NUM> is mounted to an inner surface of the flexible backing film <NUM> with respect to the heating chamber <NUM>.

The skilled person will appreciate that, in alternative embodiments, the heating chamber <NUM> may not comprise a thin film heater <NUM>. In other words, the heating element <NUM> may not be formed as a thin film heater, and the heating chamber may not comprise the flexible backing film <NUM>. For example, the heating element <NUM> may be a stand-alone heating element <NUM> that is directly applied, e.g. bonded, to the layer of electrically insulating material <NUM>. In particular, the heating element <NUM> may be wrapped around the heating chamber <NUM>, e.g. in a circumferential direction, such that the heating element <NUM> interfaces with the layer of electrically insulating material <NUM>.

The layer of electrically insulating material <NUM> preferably comprises a material with a high electrical breakdown voltage and a high thermal conductivity. Thus, the layer of electrically insulating material <NUM> prevents a short circuit occurring between the heating element <NUM> and the thermally conductive shell <NUM>, whilst allowing an efficient transfer of heat from the heating element <NUM> to the thermally conductive shell <NUM>. The skilled person will appreciate that the thermally conductive shell <NUM> is not a resistive heater, and therefore should not receive a current. The layer of electrically insulating material <NUM> separates the heating element <NUM> and the thermally conductive shell <NUM> and ensures that a current does not flow from the heating element <NUM> to the thermally conductive shell <NUM>. Moreover, the skilled person will appreciate that, as the layer of electrically insulating material <NUM> has a low thickness, the efficiency of heat transfer from the heating element <NUM> to the thermally conductive shell <NUM> remains high.

Examples of suitable materials for the layer of electrically insulating material <NUM> include silica (SiO<NUM>), diamond, and diamond-like-carbon (DLC), which can all be deposited using chemical vapour deposition due to their high temperature stability and resistance to degassing.

A heat shrink film <NUM> is preferably wrapped around the heating element <NUM> (e.g. the thin film heater <NUM>) in a circumferential direction, such that the heating element <NUM> is secured against the layer of electrically insulating material <NUM>. In other words, the heat shrink film <NUM> acts as an external layer which surrounds the exterior of the heating chamber <NUM>, thereby consolidating the structure and ensuring that the heating element <NUM> maintains contact with the layer of electrically insulating material <NUM>. In some examples, the heat shrink film <NUM> may comprise polyimide or polyether ether ketone (PEEK). Such materials provide high electrical and thermal conductivity, which is desirable for the external layer of the heating chamber <NUM>.

<FIG> illustrates a flow chart which is a method <NUM> of manufacturing a heating chamber according to an embodiment of the invention.

The method <NUM> begins at step <NUM>, wherein a heating chamber <NUM> comprising a thermally conductive shell <NUM> and an opening <NUM> for receiving an aerosol substrate within the heating chamber <NUM> is provided. At step <NUM>, a layer of electrically insulating material <NUM> is deposited onto an outer surface <NUM> of the thermally conductive shell <NUM> using vacuum deposition. Vacuum deposition is carried out significantly below atmospheric pressure, i.e. vacuum. Preferably, the layer of electrically insulating material <NUM> is deposited using chemical vapour deposition. However, in some examples, the layer of electrically insulating material <NUM> may be deposited using physical vapour deposition.

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 thermally conductive shell <NUM> and the layer of electrically insulating material <NUM> is the thin film deposit.

In some embodiments, plasma enhanced vapour deposition may be used to form the layer of electrically insulating material <NUM>. 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 electrically insulating material <NUM>) being deposited on the substrate (i.e. the thermally conductive shell <NUM>). Advantageously, plasma enhanced vapour deposition takes place at lower temperatures than other chemical vapour deposition techniques.

In one example, a radio frequency electrical discharge between two electrodes may be used to create a plasma from a carrier gas comprising CH<NUM>. The resultant chemical reaction deposits a thin film comprising diamond or diamond-like-carbon (DLC) on the thermally conductive shell <NUM>. The thin film corresponds to the layer of electrically insulating material <NUM>.

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 (SiH<NUM>) diluted in a carrier gas, such as argon, is then introduced in an afterglow of the plasma. For example, a mixture of <NUM>% silane in argon may be introduced. The resultant chemical reaction deposits a thin film comprising silicon oxide (e.g. silicon dioxide) on the thermally conductive shell <NUM>. The thin film corresponds to the layer of electrically insulating material <NUM>. For example, the deposited thin film may comprise a functionalized silica-like coating, e.g. a-SiOX:CHY.

The chemical vapour deposition process is continued until a desired thickness of the layer of electrically insulating material <NUM> is deposited, e.g. between <NUM> and <NUM>.

At step <NUM>, the heating element <NUM> is attached to the heating chamber <NUM> such that the heating element <NUM> is in contact with the layer of electrically insulating material <NUM>. That is, the heating element <NUM> is positioned adjacent to an outer surface of the layer of electrically insulating material <NUM> so that the heating element <NUM> interfaces with the layer of electrically insulating material <NUM>. In use, the heating element <NUM> may be operated to transfer heat across the electrically insulating layer <NUM> to the thermally conductive shell <NUM>. The layer of electrically insulating material <NUM> separates the heating element <NUM> and the thermally conductive shell <NUM> so that they are not in contact, thereby preventing current from flowing from the heating element <NUM> to the thermally conductive shell <NUM>.

In some embodiments, such as the embodiment depicted in <FIG>, the heating element <NUM> is comprised within a thin film heater <NUM>. In this case, the method <NUM> further comprises providing the thin film heater <NUM> comprising the heating element <NUM> and a flexible backing film <NUM> on which the heating element <NUM> is supported, and attaching the thin film heater <NUM> to the heating chamber <NUM> with the heating element <NUM> against the layer of electrically insulating material <NUM>. Alternatively, in other embodiments, the heating element <NUM> may be a stand-alone heating element <NUM> and a thin film heater <NUM> may not be provided.

In the depicted embodiment of <FIG>, wherein the heating chamber <NUM> is tubular, the heating element <NUM> is wrapped around the layer of electrically insulating material <NUM> of the heating chamber <NUM> in a circumferential direction. In particular, the thin film heater <NUM> comprising the heating element <NUM> and the flexible backing film <NUM> is wrapped around the layer of electrically insulating material <NUM> of the heating chamber <NUM>. The flexible backing film <NUM> is located on an opposing side of the heating element <NUM> to the layer of electrically insulating material <NUM>, thereby providing structural support. Of course, the skilled person will appreciate that, in embodiments wherein the heating element <NUM> is not comprised within a thin film heater <NUM>, the heating element <NUM> may be wrapped around the heating chamber <NUM> without the flexible backing film <NUM>. In some examples, the heating element <NUM> may be supported on a carrier film, and the heating element <NUM> wrapped around the heating chamber <NUM> using the carrier film. Once the heating element <NUM> is correctly positioned against the layer of electrically insulating material <NUM>, the carrier film may be removed.

At step <NUM>, a heat shrink film <NUM> is preferably wrapped around the heating chamber <NUM> to secure the heating element <NUM> to the heating chamber <NUM>. For example, in embodiments wherein the heating chamber <NUM> comprises the thin film heater <NUM>, the heat shrink film <NUM> is manipulated to surround the flexible backing film <NUM> on which the heating element <NUM> is attached. Alternatively, in embodiments wherein the heating element <NUM> is not comprised within a thin film heater <NUM>, the heat shrink film <NUM> may be manipulated to surround and interface with heating element <NUM>. As depicted in <FIG>, the heat shrink film <NUM> may also extend beyond the length of heating element <NUM> and/or the flexible backing film <NUM> and overlap with the layer of electrically insulating layer <NUM>.

Claim 1:
A method (<NUM>) of manufacturing a heating chamber (<NUM>) for an aerosol generating device (<NUM>), the method comprising:
providing (<NUM>) a heating chamber (<NUM>) comprising a thermally conductive shell (<NUM>) and an opening (<NUM>) for receiving an aerosol substrate within the heating chamber (<NUM>);
depositing (<NUM>) a layer of electrically insulating material (<NUM>) onto an outer surface of the thermally conductive shell (<NUM>) of the heating chamber (<NUM>) using vacuum deposition;
providing a thin film heater (<NUM>) comprising a heating element (<NUM>) and a flexible backing film (<NUM>) on which the heating element (<NUM>) is supported, wherein the flexible backing film (<NUM>) comprises polyimide or poly ether ketone (PEEK)
attaching (<NUM>) the thin film heater (<NUM>) to the heating chamber (<NUM>) such that the heating element (<NUM>) is in contact with the layer of electrically insulating material (<NUM>),
wherein the layer of electrically insulating material (<NUM>) prevents any contact between the heating element (<NUM>) and the thermally conductive shell (<NUM>).