Patent Description:
Devices which heat, rather than burn, a vaporisable substance to produce a vapour for inhalation have become popular with consumers in recent years.

Such devices can use one of a number of different approaches to provide heat to the substance. One such approach is to provide a vapour generating device which employs an induction heating system. In such a device, an induction coil (hereinafter also referred to as an inductor) is provided with the device and a susceptor is provided with the vaporisable substance. Electrical energy is provided to the inductor when a user activates the device which in turn generates an alternating electromagnetic field. The susceptor couples with the electromagnetic field and generates heat which is transferred, for example by conduction, to the vaporisable substance and vapour is generated as the vaporisable substance is heated.

Such an approach has the potential to provide better control of heating and therefore vapour generation. However, a shortcoming of the use of an induction heating system is that leakage of the electromagnetic field generated by the induction coil may occur and there is, therefore, a need to address this shortcoming.

<CIT> discloses an induction heating assembly for a vapour generating device according to the state of the art.

According to the present invention, there is provided an induction heating assembly for a vapour generating device, the induction heating assembly comprising:.

According to a second aspect of the present disclosure, there is provided an induction heating assembly for a vapour generating device, the induction heating assembly comprising:.

According to a third aspect of the present disclosure, there is provided a vapour generating device comprising:.

The one or more electromagnetic shield layers provide a compact, efficient and lightweight electromagnetic shield structure which reduces leakage of the electromagnetic field generated by the induction coil. This in turn allows the provision of a more compact induction heating assembly and, hence, a more compact vapour generating device.

Current flow in the one or more electromagnetic shield layers is suppressed which reduces heat generation in the shield structure (due to Joule heating) and thereby reduces energy losses. This provides a number of advantages, including: (i) a more effective transfer of electromagnetic energy from the induction coil to a susceptor associated with the induction heatable cartridge and, hence, improved heating of a vaporisable substance; (ii) a reduction in temperature, which leads to a reduction in the surface temperature of the vapour generating device and which mitigates potential damage to the device, e.g., by preventing plastics components within the device from melting due to excessively high temperatures; and (iii) protection for other electrical and electronic components within the vapour generating device.

In an embodiment, one of the electromagnetic shield layers comprises a ferrimagnetic, non-electrically conductive material and the other electromagnetic shield layer comprises an electrically conductive material.

The first electromagnetic shield layer comprises a ferrimagnetic, non-electrically conductive material. Examples of suitable materials for the first electromagnetic shield layer include, but are not limited to, ferrite, Nickel Zinc Ferrite and mu-metal. The first electromagnetic shield layer may comprise a laminate structure and may, thus, itself comprise a plurality of layers. The layers may comprise the same material or may comprise a plurality of different materials, for example which are selected to provide the desired shielding properties. The first electromagnetic shield layer could, for example, comprise one or more layers of ferrite and one or more layers of an adhesive material.

The first electromagnetic shield layer may have a thickness between <NUM> and <NUM>. In some embodiments, the thickness may be between <NUM> and <NUM>, more preferably the thickness may be between <NUM> and <NUM>.

The first electromagnetic shield layer may provide a coverage area greater than <NUM>% of the full surface area of the first electromagnetic shield layer. In some embodiments, the coverage area may be greater than <NUM>%, possibly greater than <NUM>%. As used herein, the full surface area means the surface area of a layer when the layer is fully intact, for example without any openings therein such as an air inlet or an air outlet. As used herein, the coverage area means the surface area excluding the area of any openings therein such as an air inlet or an air outlet.

The second electromagnetic shield layer comprises an electrically conductive material. The second electromagnetic shield layer may comprise a mesh. The second electromagnetic shield layer may comprise a metal. Examples of suitable metals include, but are not limited to, aluminium and copper. The second electromagnetic shield layer may comprise a laminate structure and may, thus, itself comprise a plurality of layers. The layers may comprise the same material or may comprise a plurality of different materials, for example which are selected to provide the desired shielding properties.

The second electromagnetic shield layer may have a thickness between <NUM> and <NUM>. In some embodiments, the thickness may be between <NUM> and <NUM>. The second electromagnetic shield layer may have a resistance value of less than <NUM> mΩ. The resistance value may be less than <NUM> mΩ and may be less than <NUM> mΩ. These resistance values minimise heating and conductive losses in the second electromagnetic shield layer.

The second electromagnetic shield layer may provide a coverage area greater than <NUM>% of the full surface area of the second electromagnetic shield layer. In some embodiments, the coverage area may be greater than <NUM>%, possibly greater than <NUM>%. The coverage area of the second electromagnetic shield layer may be noticeably lower than the coverage area of the first electromagnetic shield layer because, as noted above, the second electromagnetic shield layer may comprise a mesh.

The second electromagnetic shield layer may comprise a substantially cylindrical shield portion and may comprise a substantially cylindrical sleeve. The cylindrical shield portion may include a circumferential gap. Thus, the second electromagnetic shield layer may comprise a cylindrical sleeve in which the circumferential gap extends along the entirety of the sleeve in the axial direction. The circumferential gap provides an electrical break in the second electromagnetic shield layer thereby limiting the induced current at this point.

In some embodiments, there is no electrically conductive material between the induction coil and the first electromagnetic shield layer. Such an arrangement helps to suppress current flow in the shield structure.

The induction heating assembly may comprise a first insulating layer. The first insulating layer may be positioned between the induction coil and the first electromagnetic shield layer. The first insulating layer may be substantially non-electrically conductive and may have a relative magnetic permeability substantially equal to <NUM>. A relative magnetic permeability substantially equal to <NUM> means that the relative magnetic permeability may be in the range <NUM> to <NUM>, preferably <NUM> to <NUM>.

The first insulating layer may comprise exclusively a material which is substantially non-electrically conductive and which has a relative magnetic permeability substantially equal to <NUM>. Alternatively, the first insulating layer may comprise substantially a material which is substantially non-electrically conductive and has a relative magnetic permeability substantially equal to <NUM>. The first insulating layer may, for example, comprise a laminate structure or a composite structure and may, thus, itself comprise a plurality of layers and/or a mixture of particles/elements. The layers or mixture of particles/elements may comprise the same material or may comprise a plurality of different materials, for example one or more materials selected from the group consisting of a non-electrically conductive material, an electrically conductive material and a ferrimagnetic material. It will be understood that such a combination of materials would be provided in proportions which ensure that the first insulating layer comprises 'substantially' a material which is substantially non-electrically conductive and has a relative magnetic permeability substantially equal to <NUM>. In one embodiment, the material of the first insulating layer may comprise air.

The first insulating layer may have a thickness between <NUM> and <NUM>. In some embodiments, the thickness may be between <NUM> and <NUM> and may possibly be between <NUM> and <NUM>. Such an arrangement, including the first insulating layer, ensures that an optimal alternating electromagnetic field is generated by the induction coil.

The first insulating layer may provide a coverage area greater than <NUM>% of the full surface area of the first insulating layer. In some embodiments, the coverage area may be greater than <NUM>%, possibly greater than <NUM>%.

The induction heating assembly may further comprise an air passage from an air inlet to the heating compartment and the air passage may form at least part of the first insulating layer. This simplifies the construction of the induction heating assembly and allows the size of the induction heating assembly and, hence, of the vapour generating device, to be minimised. Heat from the induction coil may also be transferred to air flowing through the air passage, thus improving the efficiency of the induction heating assembly and, hence, of the vapour generating device due to preheating of the air.

The induction heating assembly further comprises a housing and the housing comprises the second electromagnetic shield layer. Such an arrangement, in which the housing acts as the second electromagnetic shield layer, leads to a reduced component count and, hence, to an improvement in the size, weight and production cost of the induction heating assembly and, thus, of the vapour generating device.

One or both of the first and second electromagnetic shield layers may be arranged circumferentially around the induction coil and at both first and second axial ends of the induction coil so as to substantially surround the induction coil. The shielding effect is, thus, maximised.

In one embodiment, the induction heating assembly may further comprise:.

Such an arrangement of the first and/or second electromagnetic shield layers ensures that maximum coverage of the first axial end of the induction coil is provided by the first and/or second electromagnetic shield layers and that the shielding effect is maximised.

The induction heating assembly may further comprise a shielding coil which may be positioned at one or both of the first and second axial ends of the induction coil possibly within the first or second electromagnetic shield layers. The shielding coil can operate as a low pass filter thereby reducing component count and, hence, leading to an improvement in the size, weight and production cost of the induction heating assembly and, thus, of the vapour generating device.

The induction heating assembly may further comprise an outer housing layer which may surround the first and second electromagnetic shield layers. This ensures that the outer surface of the vapour generating device does not become hot and that a user can handle the device without any discomfort.

In one embodiment, the induction heating assembly may further comprise a second insulating layer. The second insulating layer may be substantially non-electrically conductive and may have a relative magnetic permeability less than, or substantially equal to, <NUM>. A relative magnetic permeability substantially equal to <NUM> means that the relative magnetic permeability may be in the range <NUM> to <NUM>, preferably <NUM> to <NUM>. A first part of the second insulating layer may lie, in use, between the induction coil and a vaporisable substance inside the induction heatable cartridge. Such an arrangement, including the second insulating layer, ensures that an optimal coupling between the susceptor and the alternating electromagnetic field is achieved. A second part of the second insulating layer may be arranged outwardly of the induction coil and may be positioned between the induction coil and the first electromagnetic shield layer.

The second insulating layer may comprise exclusively a material which is substantially non-electrically conductive and which has a relative magnetic permeability less than, or substantially equal to, <NUM>. Alternatively, the second insulating layer may comprise substantially a material which is substantially non-electrically conductive and has a relative magnetic permeability less than, or substantially equal to, <NUM>. The second insulating layer may, for example, comprise a laminate structure or a composite structure and may, thus, itself comprise a plurality of layers and/or a mixture of particles/elements. The layers or mixture of particles/elements may comprise the same material or may comprise a plurality of different materials, for example one or more materials selected from the group consisting of a non-electrically conductive material, an electrically conductive material and a ferrimagnetic material. It will be understood that such a combination of materials would be provided in proportions which ensure that the second insulating layer comprises 'substantially' a material which is substantially non-electrically conductive and has a relative magnetic permeability less than, or substantially equal to, <NUM>.

In one embodiment, the second insulating layer may comprise a plastics material. The plastics material may comprise polyether ether ketone (PEEK) or any other material which has a very high thermal resistivity (insulator) and a low thermal mass. It will be understood that after a period of non-use of the vapour generating device, the components of the device, and hence of the induction heating assembly, will cool until they reach ambient temperature. Upon initial activation of the vapour generating device when the second insulating layer is contacted by heated vapour, condensation may form on the second insulating layer due to contact between the relatively hot vapour and the cooler second insulating layer, and the condensation will remain until the temperature of the second insulating layer has increased. The use of a material having a very high thermal resistivity and a low thermal mass minimises condensation because it ensures that the second insulating layer heats up as rapidly as possible following initial activation of the device when contacted by the heated vapour.

The induction heating assembly may be arranged to operate in use with a fluctuating electromagnetic field having a magnetic flux density of between approximately 20mT and approximately <NUM>. 0T at the point of highest concentration.

The induction heating assembly may include a power source and circuitry which may be configured to operate at a high frequency. The power source and circuitry may be configured to operate at a frequency of between approximately <NUM> and <NUM>, possibly between approximately <NUM> and <NUM>, and possibly at approximately <NUM>. The power source and circuitry could be configured to operate at a higher frequency, for example in the MHz range, depending on the type of inductively heatable susceptor that is used.

Whilst the induction coil may comprise any suitable material, typically the induction coil may comprise a Litz wire or a Litz cable.

Whilst the induction heating assembly may take any shape and form, it may be arranged to take substantially the form of the induction coil, to reduce excess material use. The induction coil may be substantially helical in shape.

The circular cross-section of a helical induction coil facilitates the insertion of an induction heatable cartridge into the induction heating assembly and ensures uniform heating of the induction heatable cartridge. The resulting shape of the induction heating assembly is also comfortable for the user to hold.

The induction heatable cartridge may comprise one or more induction heatable susceptors. The or each susceptor may comprise one or more, but not limited, of aluminium, iron, nickel, stainless steel and alloys thereof, e.g. Nickel Chromium or Nickel Copper. With the application of an electromagnetic field in its vicinity, the or each susceptor may generate heat due to eddy currents and magnetic hysteresis losses resulting in a conversion of energy from electromagnetic to heat.

The induction heatable cartridge may comprise a vapour generating substance inside an air permeable shell. The air permeable shell may comprise an air permeable material which is electrically insulating and non-magnetic. The material may have a high air permeability to allow air to flow through the material with a resistance to high temperatures. Examples of suitable air permeable materials include cellulose fibres, paper, cotton and silk. The air permeable material may also act as a filter. Alternatively, the induction heatable cartridge may comprise a vapour generating substance wrapped in paper. Alternatively, the induction heatable cartridge may comprise a vapour generating substance held inside a material that is not air permeable, but which comprises appropriate perforations or openings to allow air flow. Alternatively, the induction heatable cartridge may consist of the vapour generating substance itself. The induction heatable cartridge may be formed substantially in the shape of a stick.

The vapour generating substance may be any type of solid or semi-solid material. Example types of vapour generating solids include powder, granules, pellets, shreds, strands, particles, gel, strips, loose leaves, cut filler, porous material, foam material or sheets. The substance may comprise plant derived material and in particular, the substance may comprise tobacco.

The vapour generating substance may comprise an aerosol-former. Examples of aerosol-formers include polyhydric alcohols and mixtures thereof such as glycerine or propylene glycol. Typically, the vapour generating substance may comprise an aerosol-former content of between approximately <NUM>% and approximately <NUM>% on a dry weight basis. In some embodiments, the vapour generating substance may comprise an aerosol-former content of approximately <NUM>% on a dry weight basis.

Also, the vapour generating substance may be the aerosol-former itself. In this case, the vapour generating substance may be a liquid. Also, in this case, the induction heatable cartridge may include a liquid retaining substance (e.g. a bundle of fibres, porous material such as ceramic, etc.) which retains the liquid to be vaporized and allows a vapour to be formed and released/emitted from the liquid retaining substance, for example towards the air outlet for inhalation by a user.

Upon heating, the vapour generating substance may release volatile compounds. The volatile compounds may include nicotine or flavour compounds such as tobacco flavouring.

Since the induction coil produces an electromagnetic field when operating to heat a susceptor, any member comprising an induction heatable susceptor will be heated when placed in proximity to the induction coil in operation, and as such there is no restriction on the shape and form of the induction heatable cartridge being received in the heating compartment. In some embodiments, the induction heatable cartridge may be cylindrical in shape and as such the heating compartment is arranged to receive a substantially cylindrical vaporisable article.

The ability of the heating compartment to receive a substantially cylindrical induction heatable cartridge to be heated is advantageous as, often, vaporisable substances and tobacco products in particular, are packaged and sold in a cylindrical form.

Referring initially to <FIG>, there is shown diagrammatically a vapour generating device <NUM> according to an example of the present disclosure. The vapour generating device <NUM> comprises a housing <NUM>. When the device <NUM> is used for generating vapour to be inhaled, a mouthpiece <NUM> may be installed on the device <NUM> at an air outlet <NUM>. The mouthpiece <NUM> provides the ability for a user to easily inhale vapour generated by the device <NUM>. The device <NUM> includes a power source and control circuitry, designated by the reference numeral <NUM>, which may be configured to operate at high frequency. The power source typically comprises one or more batteries which could, for example, be inductively rechargeable. The device <NUM> also includes an air inlet <NUM>.

The vapour generating device <NUM> comprises an induction heating assembly <NUM> for heating a vapour generating (i.e. vaporisable) substance. The induction heating assembly <NUM> comprises a generally cylindrical heating compartment <NUM> which is arranged to receive a correspondingly shaped generally cylindrical induction heatable cartridge <NUM> comprising a vaporisable substance <NUM> and one or more induction heatable susceptors <NUM>. The induction heatable cartridge <NUM> typically comprises an outer layer or membrane to contain the vaporisable substance <NUM>, with the outer layer or membrane being air permeable. For example, the induction heatable cartridge <NUM> may be a disposable cartridge <NUM> containing tobacco and at least one induction heatable susceptor <NUM>.

The induction heating assembly <NUM> comprises a helical induction coil <NUM> which extends around the cylindrical heating compartment <NUM> and which can be energised by the power source and control circuitry <NUM>. As will be understood by those skilled in the art, when the induction coil <NUM> is energised, an alternating and time-varying electromagnetic field is produced. This couples with the one or more induction heatable susceptors <NUM> and generates eddy currents and/or hysteresis losses in the one or more induction heatable susceptors <NUM> causing them to heat up. The heat is then transferred from the one or more induction heatable susceptors <NUM> to the vaporisable substance <NUM>, for example by conduction, radiation and convection.

The induction heatable susceptor(s) <NUM> can be in direct or indirect contact with the vaporisable substance <NUM>, such that when the susceptors <NUM> is/are inductively heated by the induction coil <NUM> of the induction heating assembly <NUM>, heat is transferred from the susceptor(s) <NUM> to the vaporisable substance <NUM>, to heat the vaporisable substance <NUM> and produce a vapour. The vaporisation of the vaporisable substance <NUM> is facilitated by the addition of air from the surrounding environment through the air inlet <NUM>. The vapour generated by heating the vaporisable substance <NUM> then exits the heating compartment <NUM> through the air outlet <NUM> and may, for example, be inhaled by a user of the device <NUM> through the mouthpiece <NUM>. The flow of air through the heating compartment <NUM>, i.e. from the air inlet <NUM>, through the heating compartment <NUM>, along an inhalation passage <NUM> of the induction heating assembly <NUM>, and out of the air outlet <NUM>, can be aided by negative pressure created by a user drawing air from the air outlet <NUM> side of the device <NUM> using the mouthpiece <NUM>.

The induction heating assembly <NUM> comprises a first electromagnetic shield layer <NUM> arranged outward of the induction coil <NUM> and typically formed of a ferrimagnetic, non-electrically conductive material such as ferrite, Nickel Zinc Ferrite or mu-metal. In the embodiment shown in <FIG>, the first electromagnetic shield layer <NUM> comprises a substantially cylindrical shield portion <NUM>, for example in the form of a substantially cylindrical sleeve, which is positioned radially outwardly of the helical induction coil <NUM> so as to extend circumferentially around the induction coil <NUM>. The substantially cylindrical shield portion <NUM> typically has a layer thickness (in the radial direction) of between approximately <NUM> and <NUM>. The first electromagnetic shield layer <NUM> also comprises a first annular shield portion <NUM>, provided at a first axial end <NUM> of the induction heating assembly <NUM>, which has a layer thickness (in the axial direction) of approximately <NUM>. The first electromagnetic shield layer <NUM> also comprises a second annular shield portion <NUM>, provided at a second axial end <NUM> of the induction heating assembly <NUM>. It will be noted that the second annular shield portion <NUM> comprises first and second layers 42a, 42b of shielding material between which an optional shielding coil <NUM> is positioned. In alternative embodiments, the second annular shield portion <NUM> may comprise a single layer of shielding material, either with or without the shielding coil <NUM> present.

The induction heating assembly <NUM> comprises a second electromagnetic shield layer <NUM> arranged outward of the first electromagnetic shield layer <NUM>. The second electromagnetic shield layer <NUM> typically comprises an electrically conductive material, for example a metal such as aluminium or copper, and may be in the form of a mesh. In the embodiment shown in <FIG>, the second electromagnetic shield layer <NUM> comprises a substantially cylindrical shield portion <NUM>, for example in the form of a substantially cylindrical sleeve having an axially extending circumferential gap (not shown), and an annular shield portion <NUM>, provided at the first axial end <NUM> of the induction heating assembly <NUM>. The substantially cylindrical shield portion <NUM> and the annular shield portion <NUM> may be integrally formed as a single component. In some embodiments, the second electromagnetic shield layer <NUM> has a layer thickness of approximately <NUM>. The resistance value of the second electromagnetic shield layer <NUM> is selected to minimise heating and conductive losses in the second electromagnetic shield layer <NUM>, and may for example have a value of less than <NUM> mΩ.

The induction heating assembly <NUM> comprises an outer housing layer <NUM> which surrounds the first and second electromagnetic shield layers <NUM>, <NUM> and which constitutes the outermost layer of the housing <NUM>. In an alternative embodiment (not illustrated), the outer housing layer <NUM> could be omitted such that the second electromagnetic shield layer <NUM> constitutes the outermost layer of the housing <NUM>.

The induction heating assembly <NUM> comprises a first insulating layer <NUM> which is positioned between the induction coil <NUM> and the first electromagnetic shield layer <NUM>. The first insulating layer <NUM> is substantially non-electrically conductive and has a relative magnetic permeability substantially equal to <NUM>, and in the illustrated embodiment the first insulating layer <NUM> comprises air.

The provision of a first insulting layer <NUM> between the induction coil <NUM> and the first electromagnetic shield layer <NUM> advantageously ensures that an optimal electromagnetic field is generated for coupling with the susceptor(s) <NUM> of the induction heatable cartridge <NUM> and this is illustrated diagrammatically in <FIG>. For example, <FIG> illustrates diagrammatically the electromagnetic field that is generated by a helical induction coil <NUM> in the absence of the electromagnetic shield layers <NUM>, <NUM> described above. <FIG>, on the other hand, illustrates diagrammatically the electromagnetic field that is generated by the helical induction coil <NUM> when the first electromagnetic shield layer <NUM> described above, and in particular the substantially cylindrical shield portion <NUM>, is positioned either very close to, or in contact with, the induction coil <NUM>, in other words when the abovementioned first insulating layer <NUM> is not provided. It can be readily seen in <FIG> that although the first electromagnetic shield layer <NUM> reduces the strength of the electromagnetic field in a region radially outwardly of the first electromagnetic shield layer <NUM>, and thereby reduces leakage of the electromagnetic field, it also reduces the strength of the electromagnetic field in a region radially inwardly of the induction coil <NUM> where the induction heatable cartridge <NUM> is positioned in use. This is undesirable because it adversely affects the coupling of the electromagnetic field with the susceptor(s) <NUM> of the induction heatable cartridge <NUM> and reduces heating efficiency. Referring finally to <FIG>, it will be apparent that when a first insulating layer <NUM> in accordance with aspects of the present disclosure is positioned between the induction coil <NUM> and the first electromagnetic shield layer <NUM>, the first electromagnetic shield layer <NUM>, and in particular the substantially cylindrical shield portion <NUM>, reduces the strength of the electromagnetic field in a region radially outwardly of the first electromagnetic shield layer <NUM>, and thereby reduces leakage of the electromagnetic field, in a similar manner to that shown in <FIG>. However, in contrast to <FIG>, the strength of the electromagnetic field in the region radially inwardly of the induction coil <NUM>, where the induction heatable cartridge <NUM> is positioned in use, is not reduced thereby ensuring optimum coupling of the electromagnetic field with the susceptor(s) <NUM> of the induction heatable cartridge <NUM> and maximising heating efficiency.

Referring again to <FIG>, it will be noted that the induction heating assembly <NUM> comprises an annular air passage <NUM> which extends from the air inlet <NUM> to the heating compartment <NUM>. The air passage <NUM> is positioned radially outwardly of the induction coil <NUM>, between the induction coil <NUM> and the first electromagnetic shield layer <NUM>, and the first insulating layer <NUM> is formed at least in part by the air passage <NUM>.

The induction heating assembly <NUM> further comprises a second insulating layer <NUM>. It will be seen in <FIG> that a first part 58a of the second insulating layer <NUM> is arranged on the inner side of the induction coil <NUM> so that it lies between the induction coil <NUM> and the vaporisable substance <NUM> inside the induction heatable cartridge <NUM>. It will also be seen in <FIG> that a second part 58b of the second insulating layer <NUM> is arranged outwardly of the induction coil <NUM> and is positioned between the induction coil <NUM> and the first electromagnetic shield layer <NUM>. In the illustrated embodiment, the second part 58b comprises a cylindrical sleeve <NUM> positioned radially outwardly of the annular air passage <NUM>, adjacent to the first electromagnetic shield layer <NUM>. The second insulating layer <NUM> is substantially non-electrically conductive and has a relative magnetic permeability less than, or substantially equal to, <NUM>, and typically comprises a plastics material such as PEEK. As will be readily appreciated from <FIG>, the first part 58a of the second insulating layer <NUM> defines the internal volume of the heating compartment <NUM> in which the induction heatable cartridge <NUM> is received in use.

Referring now to <FIG>, there is shown part of a second embodiment of an induction heating assembly <NUM> for a vapour generating device <NUM>. The induction heating assembly <NUM> shown in <FIG> is similar to the induction heating assembly <NUM> shown in <FIG> and corresponding components are identified using the same reference numerals. It should be noted that the substantially cylindrical shield portions <NUM>, <NUM> of the first and second electromagnetic shield layers <NUM>, <NUM> have been omitted from <FIG>.

The induction heating assembly <NUM> comprises an inhalation passage <NUM> which extends from the heating compartment <NUM> to the air outlet <NUM> at the first axial end <NUM> of the induction heating assembly <NUM>. The inhalation passage <NUM> comprises first and second axial portions <NUM>, <NUM> which extend in a direction substantially parallel to the axial direction between the heating compartment <NUM> and the air outlet <NUM>. The inhalation passage <NUM> also comprises a transverse portion <NUM> which extends in a direction substantially perpendicular to the axial direction between the heating compartment <NUM> and the air outlet <NUM>. A plurality of electromagnetic shield assemblies, each comprising first and second electromagnetic shield layers <NUM>, <NUM>, are positioned to run adjacent to the transverse portion <NUM> of the inhalation passage <NUM> on opposite sides thereof. With this arrangement, the electromagnetic shield assemblies at least partially overlap each other so that the first axial end of the induction coil <NUM> is substantially shielded by the electromagnetic shield layers <NUM>, <NUM>.

Referring now to <FIG>, there is shown part of a third embodiment of an induction heating assembly <NUM> for a vapour generating device <NUM>. The induction heating assembly <NUM> shown in <FIG> is similar to the induction heating assembly <NUM> shown in <FIG> and corresponding components are identified using the same reference numerals.

The induction heating assembly <NUM> comprises an inhalation passage <NUM> which extends from the heating compartment <NUM> to the air outlet <NUM> at the first axial end <NUM> of the induction heating assembly <NUM>. The inhalation passage <NUM> comprises first, second, third and fourth axial portions <NUM>, <NUM>, <NUM>, <NUM> which extend in a direction substantially parallel to the axial direction between the heating compartment <NUM> and the air outlet <NUM>. The inhalation passage <NUM> also comprises first, second and third transverse portions <NUM>, <NUM>, <NUM> which extend in a direction substantially perpendicular to the axial direction between the heating compartment <NUM> and the air outlet <NUM>. A plurality of electromagnetic shield assemblies, each comprising first and second electromagnetic shield layers <NUM>, <NUM>, are again positioned to run adjacent to the transverse portions <NUM>, <NUM>, <NUM> of the inhalation passage <NUM> on opposite sides of the transverse portion <NUM>. With this arrangement, it will again be seen that the electromagnetic shield assemblies at least partially overlap each other so that the first axial end of the induction coil <NUM> is substantially shielded by the electromagnetic shield layers <NUM>, <NUM>.

Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims.

Claim 1:
An induction heating assembly (<NUM>) for a vapour generating device (<NUM>), the induction heating assembly (<NUM>) comprising:
an induction coil (<NUM>);
a heating compartment (<NUM>) arranged to receive an induction heatable cartridge (<NUM>);
a first electromagnetic shield layer (<NUM>) arranged outward of the induction coil (<NUM>);
a second electromagnetic shield layer (<NUM>) arranged outward of the first electromagnetic shield layer (<NUM>); and
a housing (<NUM>),
wherein the first electromagnetic shield layer (<NUM>) comprises a ferrimagnetic, non-electrically conductive material;
wherein the second electromagnetic shield layer (<NUM>) comprises an electrically conductive material; and
wherein the housing (<NUM>) comprises the second electromagnetic shield layer (<NUM>).