Aerosol-generating device for inductively heating an aerosol-forming substrate

Abstract

An aerosol-generating device (10) for generating an aerosol by inductively heating an aerosol-forming substrate (91) is provided.SOLUTION: The device comprises a device housing comprising a cavity (20) configured for removably receiving an aerosol-forming substrate (91) to be heated. The apparatus further comprises an induction heating arrangement comprising an induction coil (31) for generating an alternating magnetic field in the cavity, the induction coil being arranged around at least a portion of the receiving cavity (20). The device also comprises a flux concentrator (33) arranged around at least a portion of the induction coil and configured to distort an alternating magnetic field of the induction heating arrangement towards the cavity during use of the device, wherein the flux concentrator comprises, in particular is made of, a flux concentrator foil. The present invention further relates to an aerosol-generating system comprising an aerosol-generating device according to the invention and an aerosol-generating article for use with the device, the article comprising an aerosol-forming substrate to be heated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aerosol-generating device for generating an aerosol by inductive heating of an aerosol-forming substrate. The present invention further relates to an aerosol-generating system comprising such a device and an aerosol-generating article, the article comprising an aerosol-forming substrate to be heated. [Background technology]

[0002] Aerosol generating systems based on induction heating of an aerosol-forming substrate capable of forming an inhalable aerosol are generally known in the prior art. Such systems may comprise an aerosol generating device having a cavity for receiving the substrate to be heated. The substrate may be an integral part of an aerosol-generating article configured for use in the device. To heat the substrate, the device may comprise an induction heating arrangement including an induction coil for generating an alternating magnetic field within the cavity. The magnetic field is used to induce at least one of heat-generating eddy currents or hysteresis losses in a susceptor that is disposed in thermal proximity to or in direct physical contact with the substrate to be heated during use of the system. Generally, the susceptor may be an integral part of either the device or the article.

[0003] However, the magnetic field not only inductively heats the susceptor, but can also interfere with other sensitive parts of the aerosol generating device or sensitive external items in close proximity to the device. To reduce such undesirable interference, the aerosol generating device may be provided with a magnetic flux concentrator disposed around the induction heating arrangement, which acts to substantially confine the magnetic field generated by the heating arrangement within the volume enclosed by the magnetic flux concentrator. However, it has been observed that the containment effect is often reduced or lost if the device is subjected to an excessive force or shock, for example, after being accidentally dropped. In addition, many magnetic flux concentrators are quite bulky and can significantly increase the overall bulk and size of the aerosol generating device.

[0004] It would therefore be desirable to have an aerosol generating apparatus and system for inductively heating an aerosol-forming substrate that has the advantages of prior art solutions but without their limitations. In particular, it would be desirable to have an aerosol generating apparatus and system that includes a magnetic flux concentrator that offers enhanced robustness and a compact design. Summary of the Invention

[0005] According to the present invention, there is provided an aerosol generating device for generating an aerosol by inductively heating an aerosol-forming substrate. The device comprises a device housing having a cavity configured to removably receive the aerosol-forming substrate to be heated. The device further comprises an induction heating arrangement comprising at least one induction coil for generating an alternating magnetic field within the cavity, the at least one induction coil being disposed around at least a portion of the receiving cavity. The device also comprises a magnetic flux concentrator disposed around at least a portion of the induction coil and configured to distort the alternating magnetic field of the induction heating arrangement toward the cavity during use of the device. The magnetic flux concentrator comprises a magnetic flux concentrator foil, and in particular is made of a magnetic flux concentrator foil.

[0006] According to the present invention, it is recognized that magnetic flux concentrators, including, in particular, those made of, magnetic flux concentrator foil, are more flexible than other magnetic flux concentrator configurations, such as, for example, solid ferrite bodies. Therefore, magnetic flux concentrator foils offer good shock absorption properties and can withstand higher excessive force impacts or shocks without cracking. Compared to susceptors made from, for example, sintered ferrite powder, flexible magnetic flux concentrator foils offer significantly improved resistance to shock loads, such as those resulting from accidental drops. Furthermore, magnetic flux concentrator foils, due to their small dimensions, enable more compact designs of aerosol generating devices. In particular, compared to sintered ferrite magnetic flux concentrators, magnetic flux concentrator foils can be made significantly thinner. Furthermore, in contrast to solid magnetic flux concentrators, magnetic flux concentrator foils allow for compensation for manufacturing tolerances and fine-tuning of the inductivity. In particular, magnetic flux concentrator foils can advantageously help enhance the impedance stability of induction coils over temperature. Generally, the impedance of an induction coil is affected by the presence of a flux concentrator. When using flux concentrator foils, the conductance of the induction heating system may change less with temperature due to the small volume of the foil, especially compared to larger-volume solid flux concentrators. As a result, the impedance may also change less with temperature. Apart from that, flux concentrator foils are easy to manufacture.

[0007] As used herein, the phrase "concentrate the magnetic field" means that the magnetic flux concentrator is capable of distorting the magnetic field so that the density of the magnetic field increases within the cavity.

[0008] By distorting the magnetic field toward the cavity, the magnetic flux concentrator reduces the extent to which the magnetic field propagates beyond the induction coil. That is, the magnetic flux concentrator acts as a magnetic shield. This can reduce unwanted heating of adjacent sensitive parts of the device (e.g., the metal outer housing) or adjacent sensitive items outside the device. By reducing unwanted heating losses, the efficiency of the aerosol generating device can be further improved.

[0009] Furthermore, by distorting the magnetic field toward the cavity, the magnetic flux concentrator can advantageously concentrate or focus the magnetic field within the cavity. This can increase the level of heat generated in the susceptor for a given level of power passed through the induction coil compared to an induction coil without a magnetic flux concentrator. Therefore, the efficiency of the aerosol generation device can be improved.

[0010] The term "foil" as used herein refers to a thin sheet material having a thickness that is much smaller than the dimension in any direction perpendicular to the thickness direction. The term "thickness" as used herein refers to the dimension of the foil perpendicular to the major surface of the foil. In particular, the term "foil" may refer to a sheet material that is flexible and preferably bends under its own weight. More specifically, the term "foil" may refer to a sheet material that bends under its own weight at least 5 degrees, particularly at least 20 degrees, more particularly 30 degrees, per 2 centimeters of length on one side of a freely extending sample of the foil. The term "foil" may refer to a sheet material that bends under its own weight with a radius of curvature of up to 5 centimeters, particularly 2 centimeters, more particularly up to 1.5 centimeters.

[0011] The magnetic flux concentrator foil preferably has a thickness in the range of 0.02 mm (millimeter) to 0.25 mm (millimeter), in particular 0.05 mm (millimeter) to 0.2 mm (millimeter), preferably 0.1 mm (millimeter) to 0.15 mm (millimeter), or 0.04 mm (millimeter) to 0.08 mm (millimeter), or 0.03 mm (millimeter) to 0.07 mm (millimeter). Such thickness values ​​allow for a particularly compact design of the aerosol generating device. Furthermore, these values ​​are large enough to sufficiently deflect the AC magnetic field of the induction heating arrangement toward the cavity during use of the device.

[0012] The thickness of the magnetic flux concentrator may be substantially constant along any direction perpendicular to the thickness of the magnetic flux concentrator. In other embodiments, the thickness of the magnetic flux concentrator may vary along one or more directions perpendicular to the thickness of the magnetic flux concentrator. For example, the thickness of the magnetic flux concentrator may taper or decrease from one end to the other, or from a central portion of the magnetic flux concentrator toward both ends. The thickness of the magnetic flux concentrator may be substantially constant around its periphery. In other embodiments, the thickness of the magnetic flux concentrator may vary around its periphery.

[0013] In general, the magnetic flux concentrator may have any shape, and more preferably, a shape that matches the shape of at least one inductor in which the concentrator is at least partially disposed.

[0014] For example, the magnetic flux concentrator may have a substantially cylindrical shape, particularly a sleeve-shaped or tubular shape. That is, the magnetic flux concentrator may be a tubular magnetic flux concentrator, a magnetic flux concentrator sleeve, or a cylindrical magnetic flux concentrator. Such a shape is particularly suitable when the at least one induction coil is a helical induction coil having a substantially cylindrical shape. In such a configuration, the magnetic flux concentrator completely surrounds the at least one induction coil along at least a portion of the axial extension of the coil. A tubular or sleeve shape is particularly advantageous with respect to a hollow cylindrical shape and with respect to a cylindrical and / or helical configuration of the induction coil. With this shape, the magnetic flux concentrator may have any suitable cross-section. For example, the magnetic flux concentrator may have a square, elliptical, rectangular, triangular, pentagonal, hexagonal, or similar cross-sectional shape. Preferably, the magnetic flux concentrator has a circular cross-section. For example, the magnetic flux concentrator may have an annular cylindrical shape.

[0015] The magnetic flux concentrator may also extend only partially around the circumference of the at least one induction coil.

[0016] In any of these configurations, the magnetic flux concentrator is preferably disposed coaxially with the centerline of the at least one induction coil. Even more preferably, the magnetic flux concentrator and the at least one induction coil are coaxial with the centerline of the cavity.

[0017] In general, the induction heating arrangement may comprise a single induction coil or multiple induction coils, particularly two induction coils. In the case of a single induction coil, the magnetic flux concentrator is disposed around at least a portion of the single induction coil, preferably completely around the induction coil. In the case of multiple induction coils, the magnetic flux concentrator may be disposed around at least a portion of one of the induction coils, preferably around at least a portion of each one of the induction coils, and even more preferably completely around each induction coil.

[0018] The flux concentrator foil may be wound, particularly with overlapping or abutting ends, to form a tubular flux concentrator or flux concentrator sleeve. The overlapping or abutting ends may be attached to one another. Similarly, the overlapping or abutting ends may loosely overlap or abut one another.

[0019] In particular, the flux concentrator foil may be wound with a single turn to form a tubular flux concentrator or flux concentrator sleeve with a single turn of the flux concentrator foil. Alternatively, the flux concentrator foil may be wound with multiple turns / windings to form a tubular flux concentrator or flux concentrator sleeve with multiple, particularly spiral, windings.

[0020] The flux concentrator foil may also be spirally wound axially about the winding axis to form a tubular flux concentrator or flux concentrator sleeve with one or more spiral windings of flux concentrator foil overlapping each other.

[0021] Of course, the flux concentrator foils can also be wound with separate concentric windings on top of each other, i.e., the flux concentrator can comprise multiple flux concentrator foils wound with separate concentric single (turn) windings on top of each other. Similarly, the flux concentrator foils can also be wound with separate spiral or multiple windings on top of each other, i.e., the flux concentrator can comprise multiple flux concentrator foils wound with separate concentric multiple spiral or helical (turn) windings on top of each other.

[0022] Furthermore, the magnetic flux concentrator may comprise multiple magnetic flux concentrator foils arranged adjacent to each other, each magnetic flux concentrator foil wound with a single winding, or with multiple overlapping spiral windings, or with separate overlapping concentric windings.

[0023] Configurations of magnetic flux concentrator foils including multiple, particularly multiple spiral or helical, windings or multiple separate concentric windings that overlap each other may be advantageously used to create multilayer magnetic flux concentrator foils or multilayer magnetic flux concentrators, with each winding corresponding to a layer. For example, a magnetic flux concentrator may include two, three, four, five, six, seven, or more spiral or helical windings or multiple separate concentric windings. Such multilayer magnetic flux concentrator foils or multilayer magnetic flux concentrators may thus have a thickness that substantially corresponds to the thickness of a single layer or foil multiplied by the number of windings or layers. For example, if the foil has a thickness in the range of 0.02 mm (millimeter) to 0.25 mm (millimeter), in particular 0.05 mm (millimeter) to 0.2 mm (millimeter), preferably 0.1 mm (millimeter) to 0.15 mm (millimeter), a multilayer magnetic flux concentrator foil or multilayer magnetic flux concentrator comprising 6 layers may have a thickness in the range of 0.12 mm (millimeter) to 1.5 mm (millimeter), in particular 0.3 mm (millimeter) to 1.2 mm (millimeter), preferably 0.6 mm (millimeter) to 0.9 mm (millimeter).

[0024] When the magnetic flux concentrator foil is wound, particularly with a single winding, to form a tubular magnetic flux concentrator or magnetic flux concentrator sleeve, the magnetic flux concentrator foil may be attached to the inner surface of the device housing in a press-fit manner by partial release of the elastic restoring force of the wound magnetic flux concentrator foil. That is, the elastic restoring force presses the magnetic flux concentrator foil radially outward against the inner surface of the device housing. In this configuration, the ends of the wound foil preferably loosely overlap or abut each other. Advantageously, this configuration allows for simple installation of the magnetic flux concentrator, particularly without additional fastening means.

[0025] The magnetic flux concentrator can also result from directly extruding a magnetic flux concentrator foil into its final shape. In particular, the magnetic flux concentrator can comprise or be an extruded magnetic flux concentrator foil, such as an extruded tubular magnetic flux concentrator foil or magnetic flux concentrator foil sleeve, or an extruded cylindrical magnetic flux concentrator foil. The extruded tubular magnetic flux concentrator foil or extruded magnetic flux concentrator foil sleeve or extruded cylindrical magnetic flux concentrator foil can have a wall thickness ranging from 0.05 mm to 0.25 mm, preferably from 0.1 mm to 0.15 mm. The wall thickness can also be in the range of 0.12 mm to 1.5 mm, particularly from 0.3 mm to 1.2 mm, preferably from 0.6 mm to 0.9 mm.

[0026] As used herein, the term "magnetic flux concentrator" refers to a component with a high relative magnetic permeability that functions to concentrate and direct the electromagnetic field or lines of force generated by an induction coil.

[0027] As used herein, the term "high relative permeability" refers to a relative permeability of at least 100, particularly at least 1000, preferably at least 10000, even more preferably at least 50000, and most preferably at least 80000. These exemplary values ​​refer to maximum relative permeability values ​​at frequencies up to 50 kHz and temperatures of 25°C.

[0028] As used herein and in the art, the term "relative permeability" refers to the ratio of the permeability of a material or medium, such as a magnetic flux concentrator, to the permeability of free space, "μ0," where μ0 is 4π 10 -7 N.A. -2 (4·Pi·10E-07 Newtons per square ampere).

[0029] Thus, it is preferred that the magnetic flux concentrator foil comprises, in particular is made of, material(s) having a relative permeability of at least 100, in particular at least 1000, preferably at least 10000, even more preferably at least 50000 and most preferably at least 80000. These values ​​preferably refer to the maximum values ​​of relative permeability at frequencies up to 50 kHz and at a temperature of 25°C.

[0030] The magnetic flux concentrator foil may comprise any suitable material or be made from a combination of materials. Preferably, the magnetic flux concentrator foil comprises a ferrimagnetic or ferromagnetic material, such as a ferrite material, such as ferrite particles or powder, held in a matrix, or any other suitable material, including a ferromagnetic material, such as iron, ferromagnetic steel, iron silicon, or ferromagnetic stainless steel. Similarly, the magnetic flux concentrator foil may comprise a ferrimagnetic or ferromagnetic material, such as ferrimagnetic or ferromagnetic particles or powder, held in a matrix. The matrix may include a binder, such as a polymer (such as silicon). Thus, the matrix may be a polymeric matrix, such as a silicon matrix.

[0031] The ferromagnetic material may include at least one metal selected from iron, nickel, and cobalt, and combinations thereof, and may include other elements such as chromium, copper, molybdenum, manganese, aluminum, titanium, vanadium, tungsten, tantalum, silicon, etc. The ferromagnetic material may include about 78 weight percent to about 82 weight percent nickel, 0 to 7 weight percent molybdenum, and the balance iron.

[0032] The flux concentrator foil may include or be made of Permalloy, which is a nickel-iron magnetic alloy that typically contains additional elements such as molybdenum, copper, and / or chromium.

[0033] The magnetic flux concentrator foil may include or be made of mumetal, a soft ferromagnetic alloy of nickel-iron that has a very high magnetic permeability, particularly about 80,000-100,000. For example, mumetal may contain about 77 weight percent nickel, 16 weight percent iron, 5 weight percent copper, and 2 weight percent chromium or molybdenum. Similarly, mumetal may contain 80 weight percent nickel, 5 weight percent molybdenum, small amounts of various other elements such as silicon, and the remaining 12-15 weight percent iron.

[0034] The magnetic flux concentrator foil may include or be made of an alloy sold under the trademark Nanoperm® by MAGNETEC GmbH of Germany. The Nanoperm® alloy is an iron-based nanocrystalline, soft magnetic alloy containing about 83 weight percent to about 89 weight percent iron. As used herein, the term "nanocrystalline" refers to a material having a grain size of about 5 nanometers to 50 nanometers.

[0035] The magnetic flux concentrator foil may include or be made of alloys sold under the trademarks Vitrovac® or Vitroperm® by VACUUMSCHMELZE GmbH & Co. KG, Germany. Vitrovac® alloys are amorphous (metallic glasses), while Vitroperm® alloys are nanocrystalline soft magnetic alloys. For example, the magnetic flux concentrator foil may include or be made of Vitroperm 220, Vitroperm 250, Vitroperm 270, Vitroperm 400, Vitroperm 500, or Vitroperm 800.

[0036] The magnetic flux concentrator foil may include or be made of brazing foil sold under the trademark Metglas® by Metglas, Inc., USA, or Hitachi Metals Europe GmbH, Germany. Metglas® brazing foil is an amorphous nickel-based brazing foil.

[0037] In general, the magnetic flux concentrator foil can be either a single layer magnetic flux concentrator foil or a multi-layer magnetic flux concentrator foil.

[0038] For example, a multilayer magnetic flux concentrator foil may comprise a substrate layer film and at least one layer of ferromagnetic material disposed on the substrate layer.

[0039] According to another embodiment, the multilayer magnetic flux concentrator foil may comprise a multilayer stack including one or more pairs of layers, each pair comprising a spacing layer and a layer of ferromagnetic material disposed on the spacing layer.

[0040] According to another embodiment, the multilayer magnetic flux concentrator foil may comprise a substrate layer and a multilayer stack disposed on the substrate layer, the multilayer stack including one or more pairs of layers, each pair comprising a spacing layer and a layer of ferromagnetic material disposed on the spacing layer.

[0041] According to another embodiment, the multilayer magnetic flux concentrator foil may comprise a layer of a first ferromagnetic material and a multilayer stack disposed on the first layer of ferromagnetic material, the multilayer stack including one or more pairs of layers, each pair comprising a spacing layer and a layer of a second ferromagnetic material disposed on the spacing layer.

[0042] Conversely, a multi-layer magnetic flux concentrator foil may comprise a multi-layer stack and a layer of a first ferromagnetic material disposed on the multi-layer stack, the multi-layer stack including one or more pairs of layers, each pair comprising a spacing layer and a layer of a second ferromagnetic material disposed on the spacing layer.

[0043] According to another embodiment, the multilayer magnetic flux concentrator foil may comprise a substrate layer, a layer of a first ferromagnetic material disposed on the substrate layer, and a multilayer stack disposed on the first layer of ferromagnetic material, the multilayer stack including one or more pairs of layers, each pair comprising a spacing layer and a layer of a second ferromagnetic material disposed on the spacing layer.

[0044] Conversely, the multilayer magnetic flux concentrator foil may comprise a substrate layer, a multilayer stack disposed on the substrate layer, and a layer of a first ferromagnetic material disposed on the multilayer stack, the multilayer stack including one or more pairs of layers, each pair comprising a spacing layer and a layer of a second ferromagnetic material disposed on the spacing layer.

[0045] One or more layers comprising the (first or second) ferromagnetic layer may comprise at least one metal selected from iron, nickel, copper, molybdenum, manganese, silicon, and combinations thereof. The ferromagnetic material may comprise about 88 weight percent to about 82 weight percent nickel and about 18 weight percent to about 20 weight percent iron. In particular, one or more layers comprising the (first or second) ferromagnetic layer may comprise or be made of a foil. The foil preferably comprises or is made of one of Permalloy, Nanoperm® alloy, Vitroperm® alloy (such as Vitroperm 800), or Metglas® brazing foil.

[0046] The first and second ferromagnetic materials may be the same as or different from one another.

[0047] The substrate layer may comprise a polymeric film. The polymeric film may be selected from polyester, polyimide, polyolefin, or a combination thereof. The substrate layer may comprise a release liner.

[0048] The or one or more of the spacing layers may be a dielectric layer or a non-conductive material to suppress eddy current effects. The or one or more of the spacing layers may be made of a ferromagnetic material having a relatively low magnetic permeability. The or one or more of the spacing layers may include an acrylic polymer.

[0049] Additionally, the multilayer magnetic flux concentrator foil, particularly any one of the aforementioned multilayer magnetic flux concentrator foils, may comprise a protective layer. The protective layer preferably forms at least one of the two outermost layers (edge ​​layers) of the multilayer magnetic flux concentrator foil. The protective layer may comprise or be made of a polymer or a ceramic.

[0050] Furthermore, the multilayer magnetic flux concentrator foil, particularly any one of the aforementioned multilayer magnetic flux concentrator foils, may comprise an adhesive layer, such as an adhesive tape. The adhesive layer preferably forms at least one of the two outermost layers of the multilayer magnetic flux concentrator foil. In particular, the substrate layer of any one of the aforementioned multilayer magnetic flux concentrator foils may be an adhesive layer.

[0051] Preferably, one of the outermost layers of the multi-layer magnetic flux concentrator foil is a protective layer, and each of the other outermost layers of the multi-layer magnetic flux concentrator foil is an adhesive layer.

[0052] The aerosol generating device may include a radial gap between the at least one induction coil and a magnetic flux concentrator, the magnetic flux concentrator at least partially surrounding the induction coil. Thus, the gap also at least partially surrounds the induction coil. The gap may be an air gap or a gap filled with a filler material, e.g., a polyimide such as poly(4,4'-oxydiphenylene-pyromellitic imide), also known as Kapton®, or any other suitable dielectric material. For example, the induction coil may be wrapped with one or more layers of Kapton tape to fill the radial gap between the at least one induction coil and the magnetic flux concentrator. One layer of Kapton tape may have a thickness ranging from 40 micrometers to 80 micrometers.

[0053] The gap may have a radial extension in the range of 40 micrometers to 400 micrometers, particularly 100 micrometers to 240 micrometers, e.g., 220 micrometers. Advantageously, the gap can serve to reduce losses in the induction coil and increase losses in the heated susceptor, i.e., increase the heating efficiency of the aerosol-generating device. The induction heating arrangement may include at least one susceptor element that is part of the device. Alternatively, the at least one susceptor element may be an integral part of the aerosol-generating article that includes the aerosol-forming substrate to be heated. As part of the device, the at least one susceptor element is disposed or disposable at least partially within the cavity so as to be in thermal proximity or thermal contact, preferably physical contact, with the aerosol-forming substrate during use.

[0054] As used herein, the term "susceptor element" refers to an element capable of converting electromagnetic energy into heat when subjected to an alternating electromagnetic field. This can be the result of hysteresis loss and / or eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. Hysteresis loss occurs in ferromagnetic or ferrimagnetic susceptors due to magnetic domains in the material being switched under the influence of the alternating electromagnetic field. Eddy currents may be induced if the susceptor is electrically conductive. In the case of electrically conductive ferromagnetic or ferrimagnetic susceptors, heat can be generated by both eddy currents and hysteresis loss.

[0055] Thus, the susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-forming substrate. Preferred susceptor elements include metal or carbon. Preferred susceptor elements may include a ferromagnetic material (e.g., ferritic iron), or ferromagnetic steel or stainless steel. Suitable susceptor elements may be or include aluminum. Preferred susceptor elements may be formed from 400 series stainless steel, such as grade 410, or grade 420, or grade 430 stainless steel.

[0056] The susceptor element can include a variety of geometric configurations. The susceptor element can include or be a susceptor pin, susceptor rod, susceptor blade, susceptor strip, or susceptor plate. When the susceptor element is part of an aerosol-generating device, the susceptor pin, susceptor rod, susceptor blade, susceptor strip, or susceptor plate can preferably protrude into a cavity of the device toward an opening of the cavity for inserting an aerosol-generating article into the cavity.

[0057] The susceptor element may include or be a filament susceptor, a mesh susceptor, or a wick susceptor.

[0058] Similarly, the susceptor element may include or be a susceptor sleeve, susceptor cup, cylindrical susceptor, or tubular susceptor, the interior cavity of which is preferably configured to removably receive at least a portion of the aerosol-generating article.

[0059] The susceptor elements described above may have any cross-sectional shape, such as, for example, circular, oval, square, rectangular, triangular, or any other suitable shape.

[0060] The term "aerosol-generating device" as used herein generally refers to an electrically operated device capable of interacting with at least one aerosol-forming substrate, particularly an aerosol-forming substrate provided within an aerosol-generating article, to generate an aerosol by heating the substrate. The aerosol-generating device is preferably a smoking device for generating an aerosol that can be inhaled directly by a user through the user's mouth. In particular, the aerosol-generating device is a handheld aerosol-generating device.

[0061] In addition to the induction coil, the induction heating arrangement may include an alternating current (AC) generator. The AC generator may be powered by a power supply of the aerosol generating device. The AC generator is operably coupled to at least one induction coil. In particular, the at least one induction coil may be an integral part of the AC generator. The AC generator is configured to generate a high-frequency oscillating current that passes through the induction coil to generate an alternating electromagnetic field. The AC current may be supplied to the induction coil continuously after activation of the system, or may be supplied intermittently (e.g., with each puff).

[0062] Preferably, the induction heating arrangement comprises a DC / AC converter connected to a DC power supply including an LC network, the LC network comprising a series connection of a capacitor and an induction coil.

[0063] The induction heating arrangement is preferably configured to generate a high frequency electromagnetic field, which as referred to herein may be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), in particular 5 MHz (megahertz) to 15 MHz (megahertz), preferably 5 MHz (megahertz) to 10 MHz (megahertz).

[0064] The aerosol-generating device may further include a controller configured to control the operation of the device. In particular, the controller may be configured to control the operation of the induction heating arrangement, preferably in a closed-loop configuration, to control the heating of the aerosol-forming substrate to a predetermined operating temperature. The operating temperature used to heat the aerosol-forming substrate may be at least 180°C, particularly at least 300°C, preferably at least 350°C, more preferably at least 370°C, and most preferably at least 400°C. These temperatures are typical operating temperatures for heating but not burning the aerosol-forming substrate. The operating temperature is preferably in the range of 180°C to 370°C, particularly 180°C to 240°C, or 280°C to 370°C. Generally, the operating temperature may depend on at least one of the type of aerosol-forming substrate to be heated, the configuration of the susceptor, and the arrangement of the susceptor relative to the aerosol-forming substrate during use of the system. For example, if the susceptor is configured and arranged to surround the aerosol-forming substrate during use of the system, the operating temperature may be in the range of 180°C to 240°C. Similarly, if the susceptor is configured to be disposed within the aerosol-forming substrate when the system is in use, the operating temperature may be in the range of 280° C. to 370° C. The operating temperatures mentioned above preferably refer to the temperature of the susceptor when in use.

[0065] The controller may comprise a microprocessor, e.g., a programmable microprocessor, microcontroller, or application specific integrated circuit chip (ASIC) or other electronic circuitry capable of providing control. The controller may comprise further electronic components, such as at least one DC / AC inverter and / or power amplifier, e.g., a class C, class D, or class E power amplifier. In particular, the induction heating arrangement may be part of the controller.

[0066] The aerosol generating device may include a power source, particularly a DC power source configured to provide a DC supply voltage and a DC supply current to the induction heating arrangement. The power source is preferably a battery, such as a lithium iron phosphate battery. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging, i.e., the power source may be rechargeable. The power source may have a capacity that allows for storage of energy sufficient for one or more user experiences. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes, or a multiple of six minutes. In another embodiment, the power source may have a capacity sufficient to allow for a predetermined number of puffs or individual activations of the induction heating arrangement.

[0067] The aerosol generating device may comprise a main body that preferably includes at least one of an induction heating arrangement, in particular at least one induction coil, a magnetic flux concentrator, a controller, a power supply, and at least a portion of a cavity.

[0068] In addition to the main body, the aerosol-generating device may further include a mouthpiece, particularly if the aerosol-generating article used with the device does not include a mouthpiece. The mouthpiece may be mounted on the main body of the device. The mouthpiece may be configured to close the receiving cavity when the mouthpiece is attached to the main body. To attach the mouthpiece to the main body, the proximal end portion of the main body may include a magnetic or mechanical mount, such as a bayonet mount or a snap-fit ​​mount, that engages with a corresponding counterpart at the distal end portion of the mouthpiece. If the device does not include a mouthpiece, the aerosol-generating article used with the aerosol-generating device may include a mouthpiece, such as a filter plug.

[0069] The aerosol generating device may comprise at least one air outlet, for example an air outlet in the mouthpiece (if present).

[0070] The aerosol-generating device preferably comprises an air path extending from at least one air inlet, through the receiving cavity, and optionally further to an air outlet, if any, of the mouthpiece. The aerosol-generating device preferably comprises at least one air inlet in fluid communication with the receiving cavity. As a result, the aerosol-generating system may comprise an air path extending from the at least one air inlet into the receiving cavity, and optionally through an aerosol-forming substrate within the article and the mouthpiece, and further into the user's mouth.

[0071] The at least one induction coil and magnetic flux concentrator may be part of an induction module disposed within the device housing and forming at least a portion of the cavity of the device or disposed circumferentially around it, in particular removably disposed therearound.

[0072] In this regard, the present invention also provides an induction module disposable within an aerosol-generating device so as to form or be circumferentially disposed around at least a portion of a cavity of the device, the cavity being configured to removably receive an aerosol-forming substrate to be inductively heated. The induction module comprises at least one induction coil for generating an alternating current electromagnetic field within the cavity during use, the at least one induction coil being disposed around at least a portion of the receiving cavity when the induction module is disposed in the device. The induction module further comprises a magnetic flux concentrator disposed circumferentially around at least a portion of the at least one induction coil and configured to distort the alternating current electromagnetic field of the induction coil toward the cavity during use when the induction module is disposed in the device. The magnetic flux concentrator comprises or is made of a magnetic flux concentrator foil according to the present invention, as described herein.

[0073] Further features and advantages of the induction module, in particular the induction coil and magnetic flux concentrator, have been described with respect to the aerosol generating device and will not be repeated.

[0074] According to the present invention, there is also provided an aerosol generation system comprising an aerosol generating device according to the present invention and as described herein. The system further comprises an aerosol-generating article for use with the device, the article comprising an aerosol-forming substrate that is inductively heated by the device. The aerosol-generating article is received or receivable at least partially within the cavity of the device.

[0075] As used herein, the term "aerosol-generating system" refers to the combination of an aerosol-generating article as further described herein and an aerosol-generating device according to the present invention as described herein, in which the article and device cooperate to generate a respirable aerosol.

[0076] The term "aerosol-generating article" as used herein refers to an article comprising at least one aerosol-forming substrate that, when heated, releases a volatile compound capable of forming an aerosol. The aerosol-generating article is preferably a heated aerosol-generating article, i.e., an aerosol-generating article comprising at least one aerosol-forming substrate that is intended to be heated, rather than combusted, to release a volatile compound capable of forming an aerosol. The aerosol-generating article may also be a consumable product, particularly one that is disposed of after a single use. For example, the article may be a cartridge containing a liquid aerosol-forming substrate that is to be heated. Alternatively, the article may be a rod-shaped article (particularly a tobacco article) that resembles a conventional cigarette.

[0077] As used herein, the term "aerosol-forming substrate" refers to a substrate formed from or including an aerosol-forming material capable of releasing a volatile compound upon heating to form an aerosol. The aerosol-forming substrate is intended to be heated, rather than combusted, to release the aerosol-forming volatile compound. The aerosol-forming substrate may be a solid aerosol-forming substrate or a liquid aerosol-forming substrate. In both cases, the aerosol-forming substrate may include both solid and liquid components. The aerosol-forming substrate may include a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, or additionally, the aerosol-forming substrate may include a non-tobacco material. The aerosol-forming substrate may further include an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol. The aerosol-forming substrate may also include other additives and ingredients, such as nicotine or flavoring agents. The aerosol-forming substrate may also be a paste-like material, a sachet of porous material containing the aerosol-forming substrate, or loose tobacco mixed with, for example, a gelling or adhesive agent, which may include a common aerosol former such as glycerin, which is compressed or molded into a plug.

[0078] As previously mentioned, the at least one susceptor element used to inductively heat the aerosol-forming substrate may be an integral part of the aerosol-generating article rather than being part of the aerosol-generating device. Thus, the aerosol-generating article may comprise at least one susceptor element positioned in thermal proximity or thermal contact with the aerosol-forming substrate such that, in use, the susceptor element can be inductively heated by the inductive heating arrangement when the article is received in a cavity of the device.

[0079] Further features and advantages of the aerosol generating system according to the present invention have been described in relation to the aerosol generating device and will not be repeated here.

[0080] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0081] [Figure 1] FIG. 1 shows a schematic longitudinal cross-sectional view of an aerosol generation system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a detailed view of the guidance module according to FIG. [Figure 3] FIG. 3 is a detailed view of a guidance module according to a second embodiment of the present invention. [Figure 4] FIG. 4 shows a schematic longitudinal cross-sectional view of an aerosol generation system according to a third embodiment of the present invention. [Figure 5] FIG. 5 shows three different arrangements of magnetic flux concentrator foils according to the present invention. [Figure 6] FIG. 6 shows three different arrangements of magnetic flux concentrator foils according to the present invention. [Figure 7] FIG. 7 shows three different arrangements of magnetic flux concentrator foils according to the present invention. [Figure 8] FIG. 8 shows three different arrangements of magnetic flux concentrator foils according to the present invention. [Figure 9] FIG. 9 illustrates schematically an exemplary embodiment of a multi-layer magnetic flux concentrator foil according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0082] 1 shows a schematic cross-sectional view of a first exemplary embodiment of an aerosol-generating system 1 according to the present invention. System 1 is configured for generating an aerosol by inductively heating an aerosol-forming substrate 91. System 1 comprises two main components: an aerosol-generating article 90 including the aerosol-forming substrate 91 to be heated, and an aerosol-generating device 10 for use with article 90. Device 10 comprises a receiving cavity 20 for receiving article 90 and an induction heating arrangement for heating the substrate 91 within article 90 when article 90 is inserted into cavity 20.

[0083] The article 90 has a rod shape similar to that of a conventional cigarette. In this embodiment, the article 90 comprises four elements arranged in a coaxial alignment: a substrate element 91, a support element 92, an aerosol-cooling element 94, and a filter plug 95. The substrate element is disposed at the distal end of the article 90 and comprises a heated aerosol-forming substrate. The aerosol-forming substrate 91 may comprise, for example, a crimped sheet of homogenized tobacco material containing glycerin as an aerosol former. The support element 92 comprises a hollow core forming a central air passage 93. The filter plug 95 functions as a mouthpiece and may comprise, for example, cellulose acetate fibers. All four elements are substantially cylindrical elements arranged one after the other in a continuous manner. The four elements have substantially the same diameter and are surrounded by an outer wrapper 96 made of cigarette paper to form a cylindrical rod. An outer wrapper 96 may be wrapped around the aforementioned elements such that the free ends of the wrapper overlap one another. The wrapper may further include an adhesive that adheres the overlapping free ends of the wrapper to one another.

[0084] The device 10 comprises a substantially rod-shaped main body 11 formed by a substantially cylindrical device housing. Within a distal portion 13, the device 10 comprises a power source 16 (e.g., a lithium-ion battery) and electrical circuitry 17 including a controller for controlling the operation of the device 10, particularly the heating process. Within a proximal portion 14 opposite the distal portion 13, the device 10 comprises a receiving cavity 20. The cavity 20 is open at the proximal end 12 of the device 10, thereby allowing an item 90 to be easily inserted into the receiving cavity 20.

[0085] A bottom portion 21 of the receiving cavity separates the distal portion 13 of the device 10 from the proximal portion 14 of the device 10, and in particular from the receiving cavity 20. The bottom portion is preferably made of a thermally insulating material, such as PEEK (polyetheretherketone). Thus, electrical components within the distal portion 13 can be kept isolated from aerosols or residues generated by the aerosol-generating process within the cavity 20.

[0086] The induction heating arrangement of the apparatus 10 comprises an induction source including an induction coil 31 for generating an alternating current, particularly a high frequency, electromagnetic field. In this embodiment, the induction coil 31 is a helical coil that circumferentially surrounds the cylindrical receiving cavity 20. The induction coil 31 is formed from a wire 38 and has multiple turns or windings extending along its length. The wire 38 may have any suitable cross-sectional shape, such as square, oval, or triangular. In this embodiment, the wire 38 has a circular cross-section. In other embodiments, the wire may have a flat cross-sectional shape.

[0087] The induction heating arrangement further includes a susceptor element 60 disposed within the receiving cavity 20 to experience the electromagnetic field generated by the induction coil 31. In this embodiment, the susceptor element 60 is a susceptor blade 61. At its distal end 64, the susceptor blade is disposed in the bottom portion 21 of the receiving cavity 20 of the apparatus. From there, the susceptor blade 61 extends into the interior void of the receiving cavity 20 toward an opening of the receiving cavity 20 at the proximal end 12 of the apparatus 10. The other end, i.e., the distal free end 63, of the susceptor blade 60 is tapered to allow the susceptor blade to easily penetrate the aerosol-forming substrate 91 within the distal end portion of the article 90.

[0088] When the apparatus 10 is operated, a high-frequency alternating current is passed through the induction coil 31. This causes the coil 31 to generate an alternating electromagnetic field within the cavity 20. As a result, the susceptor blades 61 heat up due to eddy currents and / or hysteresis losses, depending on the magnetic and electrical properties of the material of the susceptor element 60. The susceptor 60 then heats the aerosol-forming substrate 91 of the article 90 to a temperature sufficient to form an aerosol. The aerosol is drawn downstream through the aerosol-generating article 90 and can be inhaled by the user. The high-frequency electromagnetic field may preferably be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), particularly 5 MHz (megahertz) to 15 MHz (megahertz), and preferably 5 MHz (megahertz) to 10 MHz (megahertz).

[0089] In this embodiment, induction coil 31 is part of induction module 30 that is disposed with proximal portion 14 of aerosol generation device 10. Induction module 30 has a substantially cylindrical shape that is coaxially aligned with central longitudinal axis C of substantially rod-shaped device 10. As can be seen in FIG. 1 , induction module 30 forms at least a portion of cavity 20 or at least a portion of the interior surface of cavity 20.

[0090] FIG. 2 shows the induction module 30 in more detail. In addition to the induction coil 31, the induction module 30 includes a tubular inner support sleeve 32 that carries the helically wound, cylindrical induction coil 31. One tubular inner support sleeve 32 has annular projections 34 that extend around the circumference of the inner support sleeve 32. The projections 34 are located on either end of the induction coil 31 and hold the coil 31 in place on the inner support sleeve 32. The inner support sleeve 32 may be made from any suitable material, such as plastic. In particular, the inner support sleeve 32 may cover at least a portion of the cavity 20, i.e., at least a portion of the interior surface of the cavity 20.

[0091] Both the induction coil 31 and the inner support sleeve 32 (except for the protrusion 34) are surrounded by a tubular magnetic flux concentrator 33 that extends along the length of the induction coil 31. The magnetic flux concentrator 33 is configured to distort the alternating electromagnetic field generated by the induction coil 31 toward the cavity 20 during use of the device 10. According to the present invention, the magnetic flux concentrator 33 is made of a magnetic flux concentrator foil 35. The magnetic flux concentrator 35 comprises a material having a high relative permeability of at least 100, particularly at least 1000, preferably at least 10,000, even more preferably at least 50,000, and most preferably at least 80,000, at frequencies up to 50 kHz and at a temperature of 25°C. Thus, the electromagnetic field generated by the induction coil 31 is attracted to and guided by the magnetic flux concentrator 33. Therefore, the magnetic flux concentrator 33 acts as a magnetic shield, which can reduce unwanted heating of or interference with external objects. The electromagnetic field lines within the interior volume defined by the induction module 30 are also distorted by the magnetic flux concentrator 33, resulting in an increased density of the electromagnetic field within the cavity 20. This may increase the current generated in the susceptor blades 61 located in the cavity 20. In this manner, the electromagnetic field may be concentrated toward the cavity 20, allowing for more efficient heating of the susceptor elements 60.

[0092] In this embodiment, the flux concentrator foil 35 has a thickness of approximately 0.1 mm (millimeters). It is a single layer foil made of mu metal. The foil 35 is wound with a single winding to form a tubular flux concentrator or flux concentrator sleeve with a single winding of the flux concentrator foil 35 surrounding the induction coil 31.

[0093] As can be further seen in FIG. 2, the flux concentrator foil 35 is wound directly around the induction coil 31 with substantially no radial spacing between the induction coil 31 and the flux concentrator foil 35 .

[0094] FIG. 3 shows another embodiment of the induction module 130, in which the magnetic flux concentrator foil 135 is radially spaced from the induction coil 131. That is, the aerosol generating device includes a radial gap 139 between the induction coil 131 and the magnetic flux concentrator foil 135. In this embodiment, the gap 139 is filled with a filler material 136, such as a polyimide, e.g., poly(4,4'-oxydiphenylene-pyromellitic imide), also known as Kapton®, or any other suitable dielectric material. For example, the induction coil 131 may be wrapped with one or more layers of Kapton tape to fill the radial gap 139 between the induction coil 131 and the magnetic flux concentrator 135. The gap 139 or the filler material 136 may each have a radial extension ranging from 40 micrometers to 240 micrometers, e.g., 80 micrometers. Advantageously, the gap 139 can serve to reduce losses in the induction coil and increase losses in the heated susceptor, i.e., increase the heating efficiency of the aerosol-generating device. Alternatively, the gap can be an air gap.

[0095] In contrast to the embodiment shown in Figures 1 and 2, the susceptor element 160 in the embodiment shown in Figure 3 is a susceptor sleeve 161 disposed on the inner surface of the inner support sleeve 132 so as to surround the article when it is received in the receiving cavity.

[0096] Otherwise, the embodiment shown in Figure 3 is very similar to the embodiment shown in Figures 1 and 2. Accordingly, the same or similar features are designated with the same reference numerals, but incremented by 100.

[0097] FIG. 4 shows a schematic cross-sectional view of an aerosol-generating system 1 according to a third embodiment of the present invention. The system is identical to the system shown in FIG. 1 , except for the susceptor. Therefore, the same reference numerals are used for the same features. In contrast to the embodiment shown in FIG. 1 , the susceptor 68 of the system according to FIG. 4 is not part of the aerosol-generating device 10, but is part of the aerosol-generating article 90. In this embodiment, the susceptor 68 includes a susceptor strip 69 made of metal, e.g., stainless steel, located within the aerosol-forming substrate of the base element 91. In particular, the susceptor 68 is disposed within the article 90 such that, after insertion of the article 90 into the cavity 20 of the device 10, the susceptor strip 69 is disposed within the cavity 20, particularly the induction coil 31, and in use, the susceptor strip 69 experiences the magnetic field of the induction coil 31.

[0098] In principle, the flux concentrator foil 35, 135 may be wound in different ways around the induction coil 33, 133. According to a first embodiment, as shown in Figure 5, the flux concentrator foil 35 may be wound with its free ends 37, 137 abutting each other, i.e. the longitudinal edges of the flux concentrator foil, which extend along the length axis C of the aerosol generating device, abut each other.

[0099] According to a second embodiment, as shown in Figure 6, the magnetic flux concentrator foils 35, 135 may be wound with their free ends 37, 137 overlapping each other, i.e., the longitudinal edges of the magnetic flux concentrator foils 35, 135, which extend along the length axis C of the aerosol generating device, abut each other.

[0100] When the magnetic flux concentrator foil is wound, particularly with a single winding, to form a tubular magnetic flux concentrator or magnetic flux concentrator sleeve, the magnetic flux concentrator foil may be attached to the inner surface of the device housing in a press-fit manner by partial release of the elastic restoring force of the wound magnetic flux concentrator foil. That is, the elastic restoring force presses the magnetic flux concentrator foil radially outward against the inner surface of the device housing. Referring to Figures 1, 2, and 4, such a magnetic flux concentrator foil can be easily inserted through the opening of the cavity 20 at the proximal end of the aerosol generation device 10 into the radial slit between the outer surface of the support sleeve 32 and the inner surface of the device housing.

[0101] According to a third embodiment shown in FIG. 7, the flux concentrator foil 35, 135 may be wound with multiple windings to form a tubular flux concentrator or flux concentrator sleeve comprising multiple, in particular spiral, windings of the flux concentrator foil that overlap each other.

[0102] According to a fourth embodiment shown in Figure 8, the magnetic flux concentrator foil 35, 13 may also be spirally wound axially relative to the winding axis, i.e., along the length axis C of the aerosol generating device, to form a tubular magnetic flux concentrator or magnetic flux concentrator sleeve comprising one or more spiral windings of the magnetic flux concentrator foil 35, 135.

[0103] The two latter configurations shown in Figures 7 and 8 may be advantageously used to create multi-layered flux concentrators (foils), with each winding corresponding to one layer.

[0104] Instead of using multiple windings of a flux concentrator foil to create a multilayer magnetic flux concentrator, the flux concentrator foil itself may be a multilayer magnetic flux concentrator foil. FIG. 9 shows an exemplary embodiment of such a multilayer magnetic flux concentrator foil 235 in cross section. In this embodiment, the multilayer magnetic flux concentrator foil 235 comprises a substrate layer film 250, such as an adhesive tape, and a layer of ferromagnetic material disposed on the substrate layer. On top of the substrate layer film 250, the multilayer magnetic flux concentrator foil 235 comprises a layer of a first ferromagnetic material 251. On top of the layer of first ferromagnetic material 251, the multilayer magnetic flux concentrator foil 235 comprises a multilayer stack 252 including multiple pairs of layers, each pair comprising a spacing layer 253 and a layer of a second ferromagnetic material 254 disposed on the spacing layer 253. The layer of first ferromagnetic material 251 and the layer of second ferromagnetic material 254 may include or be made of foil. Each foil preferably includes or is made of at least one of Permalloy, Nanoperm® alloy, Vitroperm® alloy (such as Vitroperm 800), or Metglas® brazing foil. In principle, the first and second ferromagnetic materials can be the same or different from each other. The spacing layer 253 can be a dielectric layer or a non-conductive material to suppress eddy current effects. For example, the spacing layer 253 can include or be made of an acrylic polymer or a ferromagnetic material with a relatively low magnetic permeability.

[0105] Additionally, the multilayer magnetic flux concentrator foil 235 includes a protective layer 255 over the multilayer stack 252. The protective layer may include or be made of a polymer or a ceramic.

[0106] Both the substrate layer film 250 and the protective layer 255 form the outermost or edge layers of the multilayer magnetic flux concentrator foil 235 .

[0107] The layers of ferromagnetic material 253 may each have a thickness of about 16 micrometers to 20 micrometers, for example 18 micrometers.

[0108] The total thickness of the multilayer magnetic flux concentrator foil 235 may be in the range of 0.1 millimeters to 0.2 millimeters, for example 0.15 millimeters.

Claims

1. 1. An aerosol generating apparatus for generating an aerosol by inductive heating of an aerosol-forming substrate, said apparatus comprising: a device housing comprising a cavity configured to removably receive the aerosol-forming substrate to be heated; an induction heating arrangement comprising at least one induction coil for generating an alternating magnetic field within the cavity, the induction coil being disposed around at least a portion of the receiving cavity; and a magnetic flux concentrator arranged around at least a portion of the induction coil and configured to distort the alternating magnetic field of the at least one induction heating arrangement towards the cavity during use of the apparatus, the magnetic flux concentrator comprising a magnetic flux concentrator foil, in particular made of a magnetic flux concentrator foil.

2. 2. The device according to claim 1, wherein the magnetic flux concentrator foil has a thickness in the range of 0.02 mm to 0.25 mm, in particular 0.05 mm to 0.2 mm, preferably 0.1 mm to 0.15 mm.

3. 3. The device according to claim 1, wherein the magnetic flux concentrator foil is wound so as to form a tubular magnetic flux concentrator or magnetic flux concentrator sleeve, in particular with the ends overlapping or abutting each other.

4. 4. The apparatus of claim 3, wherein the magnetic flux concentrator foil is attached to the interior surface of the apparatus housing in a force-fit manner by partial release of the elastic restoring force of the wrapped magnetic flux concentrator foil.

5. The device of claim 3 , wherein the overlapping or abutting ends are attached to one another.

6. 6. An aerosol generating device according to any one of claims 1 to 5, wherein the magnetic flux concentrator foil is a single layer foil or a multi-layer foil.

7. 7. Apparatus according to any one of claims 1 to 6, wherein the magnetic flux concentrator foil comprises, in particular is made of, a material having a maximum relative magnetic permeability of at least 1000, preferably at least 10000, at a frequency of up to 50 kHz and a temperature of 25°C.

8. An arrangement according to any one of claims 1 to 7, wherein the magnetic flux concentrator foil comprises, in particular is made of, at least one ferromagnetic or ferrimagnetic material.

9. 9. The device according to any one of the preceding claims, wherein the magnetic flux concentrator foil comprises, in particular is made of, at least one of mumetal, permalloy, or nanocrystalline soft magnetic alloy.

10. 10. Apparatus according to any one of claims 1 to 9, wherein the induction heating arrangement comprises a plurality of induction coils, in particular two induction coils, and the magnetic flux concentrator is arranged around at least a portion of one of the induction coils, preferably around at least a portion of each of the induction coils.

11. 11. The apparatus according to any one of claims 1 to 10, wherein the apparatus comprises a radial gap between the at least one induction coil and the magnetic flux concentrator having a radial extension in the range of 40 micrometers to 400 micrometers, in particular 100 micrometers to 240 micrometers.

12. The apparatus of any one of claims 1 to 11, further comprising at least one susceptor element disposed at least partially within the cavity.

13. The apparatus of claim 12 , wherein the susceptor is a tubular susceptor or a susceptor sleeve.

14. An aerosol generation system comprising an aerosol generating device according to any one of claims 1 to 13 and an aerosol-generating article at least partially received or receivable in the cavity of the device, wherein the aerosol-generating article comprises the aerosol-forming substrate to be heated.

15. 15. The system of claim 14, wherein the aerosol-generating article comprises at least one susceptor positioned in thermal proximity or thermal contact with the aerosol-forming substrate such that, in use, the susceptor is inductively heated by the induction heating arrangement when the article is received in the cavity of the apparatus.

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