Two-layer susceptor arrangement for inductive heating of an aerosol-forming substrate

Abstract

The present invention relates to a two-layer susceptor arrangement (120) for inductively heating an aerosol-forming substrate (130). The susceptor arrangement (120) comprises a first layer (121) including or consisting of a first susceptor material and a second layer (122) including or consisting of a second susceptor material, the first layer (121) and the second layer (122) being intimately connected to each other, the second susceptor material including or consisting of a Ni-Fe alloy having a Ni content of 65% by weight or less. The layer thickness of the second layer (122) is in the range of 11 micrometers to 18 micrometers, or 4 micrometers or less. The present invention also relates to an aerosol-generating article (100), as well as an aerosol-generating system further comprising the aerosol-generating article and an inductively heated aerosol generator for use with the article.

Description

[Technical Field]

[0001] The present invention relates to a multi-layer susceptor arrangement for inductively heating an aerosol-forming substrate, and to an inductively heatable aerosol-generating article comprising an aerosol-forming substrate and such a multi-layer susceptor arrangement for heating the substrate. The present invention further relates to an aerosol-generating article and an aerosol-generating system comprising the aerosol-generating article and an inductively heated aerosol generator for use with the article. [Background technology]

[0002] It is generally known in the prior art to generate aerosols by inductively heating an aerosol-forming substrate capable of forming an inhalable aerosol upon heating. To heat the substrate, the substrate may be part of an aerosol-generating article housed within an aerosol-generating device. The device may include an induction source for generating an alternating magnetic field used to inductively heat the susceptor arrangement by inducing at least one of eddy currents and hysteresis losses in the material of the susceptor arrangement. The susceptor arrangement may be an integral part of the article or may be disposed in thermal proximity or direct physical contact with the substrate to be heated. Alternatively, the susceptor arrangement may be part of the device and, when the article is engaged with the device, be in thermal proximity or direct physical contact with the substrate.

[0003] To control the temperature of a substrate, a multi-layer susceptor arrangement has been proposed, comprising a first layer and a second layer tightly bonded together. The first layer contains a first susceptor material optimized for heat loss and therefore heating efficiency, while the second layer contains a second susceptor material used as a temperature marker. To this end, the second susceptor material is specifically designed to be magnetic (ferromagnetic or ferrimagnetic) and have a Curie temperature corresponding to a predetermined temperature point for heating the substrate. At that Curie temperature, the magnetic permeability of the second susceptor material drops to 1, leading to a change in its magnetic properties from ferromagnetic or ferrimagnetic to paramagnetic. This change in magnetic properties is accompanied by a temporary change in the electrical resistance of the susceptor arrangement. Therefore, by monitoring the corresponding change in current through an induction source, it is possible to detect when the second susceptor material has reached its Curie temperature, and therefore when the predetermined temperature point has been reached.

[0004] However, the use of specially designed materials, such as second susceptor materials specially designed for a particular Curie temperature, makes the susceptor assembly more expensive to manufacture.

[0005] It would therefore be desirable to have a susceptor arrangement for inductively heating an aerosol-forming substrate that alleviates the limitations of prior art solutions while retaining their advantages. In particular, it would be desirable to have a susceptor arrangement that is less expensive to manufacture. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a two-layer susceptor arrangement for inductively heating an aerosol-forming substrate. The susceptor arrangement comprises a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first and second layers being intimately connected to each other, and the second susceptor material including or consisting of a Ni-Fe alloy having a Ni content of 65 wt.% or less. The thickness of the second layer is in the range of 11 micrometers to 25 micrometers, specifically 11 micrometers to 18 micrometers, more specifically 11 micrometers to 16 micrometers, or 12 micrometers to 18 micrometers, 13 micrometers to 18 micrometers, or 12 micrometers to 16 micrometers, or 13 micrometers to 16 micrometers.

[0007] According to a first aspect of the present invention, it has been found that the layer thickness of the second layer can be relatively small, i.e., in the range of 11 micrometers to 25 micrometers, which is beneficial in terms of saving material and therefore making the manufacture of the susceptor arrangement more cost-effective, while at the same time being large enough to ensure that the effect of the above-mentioned changes in the magnetic properties of the second susceptor material on the current through the induction source is still strong enough for reliable temperature detection.

[0008] Generally, the thicker the second layer, the more significant the measurable characteristic change in the current passing through the induction source, and the more reliable the temperature detection. Conversely, the thinner the second layer, the greater the material savings. Therefore, the lower limit of the above-mentioned range may be higher, while the upper limit may be lower. Consequently, the layer thickness of the second layer of the susceptor arrangement according to the first embodiment of the present invention may be within the range of 12 micrometers to 25 micrometers, specifically 13 micrometers to 25 micrometers, preferably 14 micrometers to 25 micrometers, or 13 micrometers to 20 micrometers and 14 micrometers to 20 micrometers. Similarly, the layer thickness of the second layer of the susceptor arrangement according to the first embodiment of the present invention may be within the range of 11 micrometers to 18 micrometers, more specifically 11 micrometers to 16 micrometers, or 12 micrometers to 18 micrometers, 13 micrometers to 18 micrometers, or 12 micrometers to 16 micrometers, or 13 micrometers to 16 micrometers.

[0009] According to a second aspect of the present invention, there is provided a two-layer susceptor arrangement for inductively heating an aerosol-forming substrate. The susceptor arrangement comprises a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first and second layers being intimately connected to each other, and the second susceptor material including or consisting of a Ni-Fe alloy having a Ni content of 65 wt. % or less. The layer thickness of the second layer is 4 micrometers or less.

[0010] According to a second aspect of the present invention, it has been found that if the layer thickness of the second layer is very small, i.e., 4 micrometers or less, this is beneficial not only in terms of material and cost savings, but also in terms of dimensional stability of the susceptor arrangement, since the second layer having such a small layer thickness compared to the first layer cannot cause thermal bending of the susceptor assembly due to the difference in thermal expansion between the first and second layers.

[0011] However, if the second layer is too thin, it may be fragile and prone to decomposition, and therefore the layer thickness of the second layer of the susceptor arrangement according to the second aspect of the present invention is preferably in the range of 1 micrometer to 4 micrometers.

[0012] According to a third aspect of the present invention, there is provided a two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first layer and the second layer being intimately connected to each other, the second susceptor material including or consisting of a Ni-Fe alloy having a Ni content of 65 wt. % or less and a Cr content of 13 wt. % or more, and the layer thickness of the second layer being in the range of 1 micrometer to 22 micrometers.

[0013] According to a third aspect of the present invention, it has been discovered that a Ni-Fe alloy having a Ni content of 65% by weight or less and a Cr content of 13% by weight or more provides sufficient resistance to corrosion due to its chemical composition, primarily its chromium content, so that a protective layer on the second layer (opposite the first layer) can be omitted. This is beneficial from the perspective of material savings. The corrosion resistance results from the relatively high chromium content, which undergoes passivation by reaction with oxygen, thus forming a passive, ultrathin, inert surface film of chromium oxide. This passive film prevents further corrosion by blocking oxygen diffusion to the surface of the second layer, thus preventing corrosion from spreading into the bulk of the metal. The passive film is self-repairing even if scratched or temporarily disturbed by environmental disturbances. Preferably, the layer thickness of the second layer of the susceptor arrangement according to the third aspect of the present invention may be in the range of 1 micrometer to 15 micrometers, specifically 4 micrometers to 15 micrometers, or 1 micrometer to 11 micrometers, more specifically 4 micrometers to 11 micrometers.

[0014] Unless otherwise stated, the following description of further advantageous aspects and features of the present invention refers to both a susceptor arrangement according to the first aspect of the invention and a susceptor arrangement according to the second aspect of the invention.

[0015] As used herein, the term "susceptor material" refers to a material that has the ability to convert electromagnetic energy into heat when subjected to an alternating magnetic field. This may be the result of at least one of hysteresis loss and eddy currents induced in the susceptor material, depending on its electrical and magnetic properties. Hysteresis loss occurs in ferromagnetic or ferrimagnetic susceptor materials due to magnetic domains in the material being switched under the influence of the alternating magnetic field. Eddy currents may be induced if the susceptor material is electrically conductive. In the case of an electrically conductive ferromagnetic susceptor or an electrically conductive ferrimagnetic susceptor, heat can be generated due to both eddy currents and hysteresis loss.

[0016] As mentioned above, the first layer comprising the first susceptor material preferably functions as a primary susceptor for heating the aerosol-forming substrate, and to this end, the first susceptor material may be optimized with respect to heat loss and therefore heating efficiency.

[0017] At least a portion of the outer surface of the first layer is unprotected, i.e., bare, and exposed to the environment or in direct contact with the environment. In particular, when the susceptor arrangement is embedded in the aerosol-forming substrate, at least a portion of the outer surface of the first layer may be exposed to the aerosol-forming substrate and in direct physical contact with the aerosol-forming substrate. This advantageously allows for good heat transfer to the aerosol-forming substrate, which is preferably heated primarily by the first layer. It is preferred that all portions of the outer surface of the first layer are unprotected, bare, or exposed to the environment, unless they are in close physical contact with other layers, particularly the second layer. This advantageously ensures maximum heat transfer to the aerosol-forming substrate.

[0018] The first susceptor material may be at least one of conductive and magnetic (i.e., either ferromagnetic or ferrimagnetic). If the first susceptor material is conductive, it may also be paramagnetic. If the first susceptor material is magnetic (ferromagnetic or ferrimagnetic), it is preferably selected to have a Curie temperature different from, and specifically higher than, the Curie temperature of the second susceptor material. In this specific configuration, the first susceptor material may have a first Curie temperature, and the second susceptor material may have a second Curie temperature.

[0019] The first susceptor material is preferably made of a corrosion-resistant material and is therefore advantageously resistant to any corrosive influences of its own.

[0020] Preferably, the first susceptor material comprises or consists of a metal, such as ferritic iron, or stainless steel, particularly a ferromagnetic stainless steel, such as a ferritic stainless steel. It may be particularly preferred for the first susceptor material to comprise or consist of a 400 series stainless steel (such as grade 410 stainless steel, or grade 420 stainless steel, or grade 430 stainless steel, or a similar grade stainless steel).

[0021] Alternatively, the first susceptor material may comprise or consist of a suitable non-magnetic material, in particular a paramagnetic conductive material (such as aluminum (Al)), in which induction heating occurs solely by resistive heating due to eddy currents.

[0022] Alternatively, the first susceptor material may comprise or consist of a non-conductive ferrimagnetic material, such as a non-conductive ferrimagnetic ceramic, in which case heat is generated solely by hysteresis losses.

[0023] Relatively, the thickness of the first layer may be about 1.5 to 5 times, particularly 2 to 4 times, preferably 2.5 to 3.5 times, and more preferably about 3 times, the thickness of the second layer. Absolutely, the thickness of the first layer is in the range of 20 to 60 micrometers, particularly 30 to 50 micrometers, for example 40 to 42.5 micrometers. Such values ​​have been demonstrated to ensure adequate heating of the aerosol-forming substrate.

[0024] As mentioned above, the second susceptor material preferably functions as a temperature marker. That is, the second susceptor material is preferably configured to monitor the temperature of the susceptor arrangement. To this end, the second susceptor material may be selected to have a Curie temperature that essentially corresponds to a predetermined temperature point in the heating process. Specifically, the second susceptor material may be selected to have a Curie temperature that essentially corresponds to a predetermined maximum heating temperature of the susceptor arrangement. The maximum desired heating temperature may be defined to be approximately the temperature to which the susceptor arrangement should be heated to generate an aerosol from the aerosol-forming substrate. However, the maximum desired heating temperature should be sufficiently low to avoid local overheating or even combustion of the aerosol-forming substrate. The Curie temperature of the second susceptor material should preferably be below the ignition point of the aerosol-forming substrate to be heated. The second susceptor material, particularly a Ni-Fe alloy of the second susceptor material, may have a Curie temperature of less than 500°C, preferably 400°C or less, and particularly 390°C or less. For example, the second susceptor, particularly a Ni-Fe alloy of the second susceptor material, may have a Curie temperature in the range of 180°C to 420°C, particularly 210°C to 380°C, and preferably 250°C to 380°C. The second layer may be a functional layer that provides a temperature marker primarily due to the Curie temperature of the second susceptor material, but may also contribute to inductive heating of the susceptor arrangement. Preferably, the second layer is a first layer including a first susceptor material that is configured primarily to heat the aerosol-forming substrate.

[0025] As defined above, the second susceptor material comprises or consists of a Ni-Fe alloy having a Ni content of 65 wt% or less. As used herein, the term "weight % (wt%)" refers to "weight percent" or "weight percentage." That is, it refers to the mass fraction of an element in the alloy, which is the ratio of the mass of the respective element to the total mass of the alloy sample.

[0026] Advantageously, most Ni-Fe alloys with a Ni content of 65 wt. % or less have Curie temperatures in the range below 600° C. and are therefore well suited as temperature markers for a wide range of heated, non-combustion substrates with ignition points above 600° C. Furthermore, most Ni-Fe alloys with a Ni content of 65 wt. % or less still have sufficiently high magnetic permeability that they exhibit a clearly detectable decrease in magnetic permeability when the temperature of the material approaches the Curie point.

[0027] The Ni content may be much less than 65 wt.%. Thus, the Ni-Fe alloy of the second susceptor material may have a Ni content of up to 50 wt.%, in particular up to 44 wt.%, more particularly in the range of 36 wt.% to 44 wt.%, preferably in the range of 36 wt.% to 40 wt.%, for example 36.1 wt.% or 36.4 wt.% or 40 wt.%, with the remainder being Fe.

[0028] The Ni-Fe alloy of the second susceptor material may be a binary Ni-Fe alloy, ie, a Ni-Fe alloy consisting only of Ni and Fe.

[0029] Alternatively, the Ni-Fe alloy may contain one or more of the following elements: Co, Cr, Cu, Mn, Mo, Nb, Si, Ti and V.

[0030] As used herein, the symbol Ni represents the chemical element nickel, the symbol Fe represents the chemical element iron, the symbol Co represents the chemical element cobalt, the symbol Cr represents the chemical element chromium, the symbol Cu represents the chemical element copper, the symbol Mn represents the chemical element manganese, the symbol Mo represents the chemical element molybdenum, the symbol Nb represents the chemical element niobium, the symbol Si represents the chemical element silicon, the symbol Ti represents the chemical element titanium, and the symbol V represents the chemical element vanadium.

[0031] Advantageously, the Curie temperature of the Ni-Fe alloy may be selectively adjusted by adding chromium. Accordingly, the Ni-Fe alloy of the second susceptor material may additionally contain chromium. In particular, the second susceptor material may include or consist of a Ni-Fe-Cr alloy. The higher the chromium content, the lower the Curie temperature of the alloy. Furthermore, adding chromium affects the corrosion resistance of the Ni-Fe alloy. In general, corrosion resistance can be improved by increasing the chromium content. As a specific example, the Ni-Fe alloy of the second susceptor material may further contain 8% to 12% by weight of Cr, particularly 9% to 11% by weight of Cr. Depending on the actual Ni content, the Curie temperature of the Ni-Fe alloy additionally containing 8% to 12% by weight of Cr, particularly 9% to 11% by weight of Cr, can be advantageously adjusted to be in the range of 200°C to 300°C.

[0032] According to one example, a Ni-Fe alloy may include or consist of 50% Ni and 9% Cr by weight, with the remainder being Fe. This alloy may be commercially available, for example, under the trade name Phytherm 260, and has a Curie temperature of 260°C. According to another example, a Ni-Fe alloy may include or consist of 50% Ni and 10% Cr by weight, with the remainder being Fe. This alloy may also be commercially available, for example, under the trade name Phytherm 220, and has a Curie temperature of 230°C. According to yet another example, a Ni-Fe alloy may include or consist of 50% Ni and 11% Cr by weight, with the remainder being Fe. This alloy may also be commercially available, for example, under the trade name Phytherm 210, and has a Curie temperature of 210°C. Advantageously, all of the aforementioned alloys (Phytherm alloys) are corrosion-resistant materials.

[0033] The Ni-Fe alloy may also contain one or more further elements in addition to chromium.

[0034] According to one example, the Ni-Fe alloy of the second susceptor material may include or consist of 50 wt% Ni, 9 wt% Cr, up to 1 wt% Si, and up to 1 wt% Mn, with the remainder being Fe. According to another example, the Ni-Fe alloy of the second susceptor material may include or consist of 50 wt% Ni, 10 wt% Cr, up to 1 wt% Si, and up to 1 wt% Mn, with the remainder being Fe. According to yet another example, the Ni-Fe alloy of the second susceptor material may include or consist of 50 wt% Ni, 11 wt% Cr, up to 1 wt% Si, and up to 1 wt% Mn, with the remainder being Fe.

[0035] As mentioned above, the Ni-Fe alloy of the second susceptor material may have a Ni content even less than 50% by weight. In particular, the Ni-Fe alloy of the second susceptor material may have a Ni content of 44% by weight or less, more specifically, a Ni content in the range of 36% to 44% by weight, preferably 36% to 40% by weight, e.g., 36.1% by weight, 36.4% by weight, or 40% by weight, with the remainder being Fe. As an example, the Ni-Fe alloy may be an alloy available from Hitachi under the designation "MS-10," which has a Ni content of 36.1% by weight and a Curie temperature of 213°C. Similarly, the Ni-Fe alloy may be an alloy available from Hitachi under the designation "MS-16," which has a Ni content of 36.4% by weight and a Curie temperature of 221.5°C.

[0036] With respect to the fabrication of the susceptor arrangement, and particularly with respect to the assembly of the various layers, one of the first and second layers may be plated, deposited, coated, clad, or welded onto the respective other layer. In particular, one of the first and second layers may be applied onto the respective other layer by spraying, dip coating, roll coating, electroplating, or cladding. Any of the above configurations or layer structures fall within the scope of the term "intimately coupled" as used herein.

[0037] In general, the bilayer susceptor arrangement may have various shapes. In particular, the susceptor arrangement may have the form of a blade, a strip, or a sheet. Preferably, the bilayer susceptor arrangement may be an elongated, particularly a strip-like, susceptor arrangement.

[0038] The overall thickness of the susceptor arrangement according to the first aspect of the invention may be in the range of 31 micrometers to 85 micrometers, particularly in the range of 50 micrometers to 60 micrometers, for example 56.5 micrometers. This is especially true when the layer thickness of the second layer is in the range of 11 micrometers to 25 micrometers, particularly in the range of 11 micrometers to 18 micrometers, more particularly in the range of 11 micrometers to 16 micrometers, or in the range of 12 micrometers to 18 micrometers, or in the range of 13 micrometers to 18 micrometers, or in the range of 12 micrometers to 16 micrometers, or in the range of 13 micrometers to 16 micrometers.

[0039] Similarly, the overall thickness of the susceptor arrangement according to the second aspect of the invention may be in the range of 21 micrometers to 64 micrometers, in particular 31 micrometers to 54 micrometers, for example 45 micrometers, if the layer thickness of the second layer is 4 micrometers or less, in particular in the range of 1 micrometer to 4 micrometers.

[0040] The overall thickness of the susceptor arrangement according to the third aspect of the present invention may be in the range of 21 micrometers to 75 micrometers, or 21 micrometers to 82 micrometers, specifically 24 micrometers to 71 micrometers, and more specifically 44 micrometers to 55 micrometers.

[0041] The width of a susceptor arrangement according to any embodiment of the present invention in a direction perpendicular to the overall thickness of the susceptor arrangement may be in the range of 3 millimeters to 7 millimeters, particularly 4 millimeters to 6 millimeters, for example 5 millimeters.

[0042] The length of a susceptor arrangement according to any embodiment of the invention in a direction perpendicular to the overall thickness of the susceptor arrangement may be in the range of 10 mm to 15 mm, in particular 11 mm to 13 mm, for example 12 mm.

[0043] The term "thickness" as used herein refers to the dimension extending between the upper and lower sides, e.g., between the upper and lower sides of a layer, or between the upper and lower sides of a two-layer susceptor arrangement. Similarly, the term "width" is used herein to refer to any dimension extending between two opposing lateral sides of a layer or susceptor arrangement. The term "length" is used herein to refer to any dimension extending between the front and back sides, or between two other opposing sides, perpendicular to the two opposing lateral sides that form the width. The width extension is preferably greater than the thickness extension. Similarly, the width extension may be less than the length extension. The thickness, width, and length may be perpendicular to each other.

[0044] According to the present invention there is also provided an inductively heatable aerosol-generating article comprising at least one aerosol-forming substrate and a two-layer susceptor arrangement according to the first or second or third aspect of the present invention and as described herein.

[0045] The term "aerosol-generating article" as used herein refers to an article comprising at least one aerosol-forming substrate capable of emitting a volatile compound capable of forming an aerosol when heated. The aerosol-generating article is preferably a heated aerosol-generating article, i.e., an aerosol-generating article comprising at least one aerosol-forming substrate intended to be heated rather than burned. Such an article may also be referred to as a non-heat-and-burn aerosol-generating article, and the substrate may also be referred to as a non-heat-and-burn aerosol-forming substrate. The aerosol-generating article may be a consumable product, particularly a consumable product that is discarded after a single use. The aerosol-generating article may also be a tobacco article. For example, the article may be a cartridge containing a liquid aerosol-forming substrate to be heated. As another example, the article is preferably an elongated or rod-shaped article. The elongated or rod-shaped article may have a shape similar to that of a conventional cigarette. In particular, such an article may have a circular, elliptical, oval, square, rectangular, triangular, or polygonal cross section.

[0046] As used herein, the term "aerosol-forming substrate" refers to a substrate formed from or containing an aerosol-forming material capable of releasing a volatile compound upon heating to generate an aerosol. Preferably, 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, a liquid aerosol-forming substrate, a gel-like aerosol-forming substrate, or any combination thereof. For example, the aerosol-forming substrate may contain 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.

[0047] The two-layer susceptor arrangement is preferably embedded in the aerosol-forming substrate.

[0048] In one embodiment, the aerosol-generating article may be a rod-shaped article, specifically a cylindrical article comprising one or more of a distal front plug element, a base element, a first tube element, a second tube element, and a filter element.

[0049] The substrate element preferably comprises at least one aerosol-forming substrate to be heated and a susceptor arrangement in thermal contact with or in thermal proximity to the aerosol-forming substrate. The substrate element may have a length of 10 to 14 millimeters, for example 12 millimeters. The susceptor arrangement may extend along the entire length of the substrate element or may have an extension of a length shorter than the length of the substrate element.

[0050] The first tube element is distal to the second tube element. Preferably, the first tube element is proximal to the base element, and the second tube element is proximal to the first tube element and distal to the filter element, i.e., between the first tube element and the filter element. At least one of the first tube element and the second tube element may comprise a central air passage. The cross-section of the central air passage of the second tube element may be larger than the cross-section of the central air passage of the first tube element. Preferably, at least one of the first tube element and the second tube element may comprise a hollow cellulose acetate tube. At least one of the first tube element and the second tube element may have a length of 6 to 10 millimeters, for example 8 millimeters.

[0051] The filter element preferably functions as a mouthpiece or as part of a mouthpiece together with a second tube element. As used herein, the term "mouthpiece" refers to the portion of the article through which the aerosol exits the aerosol-generating article. The filter element may have a length of 10 to 14 millimeters, for example 12 millimeters.

[0052] The distal front plug element may be used to cover and protect the distal front end of the base element. The distal front plug element may have a length of 3 to 6 millimeters, for example 5 millimeters. The distal front plug element may be made of the same material as the filter element.

[0053] All of the aforementioned elements may be disposed consecutively along the longitudinal axis of the article in the order described above, with the distal front plug element preferably disposed at the distal end of the article and the filter element preferably disposed at the proximal end of the article. Each of the aforementioned elements may be substantially cylindrical. Specifically, all of the elements may have the same external cross-sectional shape and / or dimensions.

[0054] Additionally, the elements may be surrounded by one or more outer wrappers, such as to hold the elements together and maintain the desired cross-sectional shape of the rod-shaped article. The wrappers are preferably made of paper. The wrappers may further comprise an adhesive that bonds the overlapping free ends of the wrappers to one another. For example, the distal forward plug element, the base element, and the first tubing element may be surrounded by a first wrapper, and the second tubing element and the filter element may be surrounded by a second wrapper. The second wrapper may also surround at least a portion of the first tubing element (after being wrapped by the first wrapper, i.e., the upper part of the first wrapper) to connect the distal forward plug element, the base element, and the first tubing element surrounded by the first wrapper to the second tubing element and the filter element. The second wrapper may comprise perforations around its circumference.

[0055] Further features and advantages of the aerosol-generating article according to the invention have already been described above in relation to the susceptor arrangement according to the first or second or third aspect of the invention and apply equally.

[0056] According to one aspect of the present invention, there is provided an aerosol generating system comprising an inductively heatable aerosol-generating article as invented and described herein, as well as an inductively heated aerosol generating device for use with the aerosol-generating article.

[0057] According to another aspect of the present invention, there is provided an aerosol generation system comprising an inductively heated aerosol generation device and an aerosol-generating article for use with the aerosol generation device, the aerosol generation device comprising a bi-layer susceptor arrangement according to the present invention and the first or second or third aspect as described herein, and the aerosol-generating article comprising an aerosol-forming substrate to be heated by the bi-layer susceptor arrangement.

[0058] That is, according to one aspect of the present invention (first configuration of the system), the susceptor arrangement is part of the aerosol-generating article, while according to another aspect of the present invention (second configuration of the system), the susceptor arrangement is part of the aerosol-generating device.

[0059] The term "aerosol-generating device," as used herein, describes an electrically actuated device for interaction with an aerosol-generating article, in any configuration, to generate an aerosol by heating an aerosol-forming substrate through interaction of a susceptor arrangement with an alternating magnetic field provided by the aerosol-generating device. The aerosol-generating device is preferably a smoking device for generating an aerosol that can be directly inhaled by a user through the user's mouth. Specifically, the aerosol-generating device is a handheld aerosol-generating device.

[0060] In either configuration of the system, the device may comprise a receiving cavity for removably receiving at least a portion of each aerosol-generating article.

[0061] In either configuration of the system, the aerosol generating device may include an induction heating arrangement constructed and arranged to generate an alternating magnetic field within the receiving cavity to inductively heat the susceptor arrangement.

[0062] To generate the alternating magnetic field, the induction heating arrangement may include at least one induction coil surrounding at least a portion of the susceptor arrangement used in the system. The at least one induction coil may be a helical coil or a flat, planar coil, specifically a pancake coil or a curved, planar coil. In a first configuration, the aerosol generating device and the aerosol-generating article are preferably configured such that the susceptor arrangement is disposed within a cavity of the device, particularly within the interior space of the at least one induction coil, so that the susceptor arrangement experiences the alternating magnetic field when the article is received within the aerosol generating device. Similarly, in a second configuration, the susceptor arrangement is preferably fixedly disposed within a cavity of the device, particularly within the interior space of the at least one induction coil, so that the susceptor arrangement experiences the alternating magnetic field.

[0063] The induction heating arrangement may further comprise 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. Specifically, 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 at least one induction coil to generate an alternating magnetic field. The AC current may be supplied to the at least one induction coil continuously after activation of the system, or may be supplied intermittently (e.g., with each puff). The induction heating arrangement may comprise a DC / AC converter including an LC network, the LC network preferably comprising a series connection of a capacitor and an inductor. The DC / AC converter may be connected to a DC power source.

[0064] The induction heating arrangement is preferably configured to generate a high frequency magnetic field, as referred to herein, the frequency of which 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).

[0065] In any configuration of the system, the aerosol generating device may further include a controller configured to control the operation of the heating process. The controller may be the overall controller of the aerosol generating device or may be part of the overall controller of the aerosol generating device. The controller may include a microprocessor (e.g., a programmable microprocessor), a microcontroller, or an application specific integrated circuit (ASIC) or other electronic circuit capable of providing control. The controller may include additional electronic components, such as at least one DC / AC converter and / or a power amplifier (e.g., a Class C power amplifier, a Class D power amplifier, or a Class E power amplifier). Specifically, the induction source may be part of the controller.

[0066] In any configuration of the system, the aerosol generating device may also include a power source, specifically a DC power source configured to provide a DC supply voltage and a DC supply current to the induction source. The power source is preferably a battery, such as a lithium iron phosphate battery. 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 for discontinuous activation of the induction source.

[0067] Further features and advantages of the aerosol-generating system according to any aspect of the present invention are described with respect to the susceptor arrangement and the aerosol-generating article and therefore apply equally.

[0068] The present invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0069] Example 1 A two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first layer and the second layer being intimately connected to each other, the second susceptor material including or consisting of a Ni-Fe alloy having a Ni content of 65 wt % or less, and the layer thickness of the second layer being in the range of 11 micrometers to 25 micrometers.

[0070] Example 2 The bilayer susceptor arrangement of Example 1, wherein the layer thickness of the second layer is within the range of 12 micrometers to 25 micrometers, specifically 13 micrometers to 25 micrometers, preferably 14 micrometers to 25 micrometers, or 13 micrometers to 20 micrometers, or 14 micrometers to 20 micrometers, or the layer thickness of the second layer is within the range of 11 micrometers to 18 micrometers, more specifically 11 micrometers to 16 micrometers, or 12 micrometers to 18 micrometers, 13 micrometers to 18 micrometers, or 12 micrometers to 16 micrometers, or 13 micrometers to 16 micrometers.

[0071] Example 3 A two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising a first layer comprising or consisting of a first susceptor material and a second layer comprising or consisting of a second susceptor material, the first layer and the second layer being intimately connected to each other, the second susceptor material comprising or consisting of a Ni-Fe alloy having a Ni content of 65 wt % or less, and the layer thickness of the second layer being 4 micrometers or less.

[0072] Example 4 The two-layer susceptor arrangement of Example 3, wherein the second layer has a layer thickness in the range of 1 micrometer to 4 micrometers.

[0073] Example 5 The two-layer susceptor arrangement according to any one of Examples 1 to 4, wherein the thickness of the first layer is within the range of about 1.5 to 5 times, specifically 2 to 4 times, preferably 2.5 to 3.5 times, and more preferably about 3 times the thickness of the second layer.

[0074] Example 6 The bilayer susceptor arrangement of any one of Examples 1-5, wherein the first susceptor material comprises or consists of a metal, such as ferritic iron, or stainless steel, specifically grade 410, grade 420, or grade 430 stainless steel.

[0075] Example 7 The bilayer susceptor arrangement of any one of Examples 1-6, wherein the Ni-Fe alloy of the second susceptor material further comprises 8 wt% to 12 wt% Cr, specifically 9 wt% to 11 wt% Cr.

[0076] Example 8 A bilayer susceptor arrangement as described in any one of Examples 1 to 7, wherein the Ni-Fe alloy of the second susceptor material has a Ni content of 50 wt% or less, specifically 44 wt% or less, more specifically in the range of 36 wt% to 44 wt%, preferably in the range of 36 wt% to 40 wt%, for example 36.1 wt% or 36.4 wt% or 40 wt%.

[0077] Example 9 The Ni-Fe alloy of the second susceptor material is -50 wt% Ni, 9 wt% Cr, balance Fe, -50 wt% Ni, 10 wt% Cr, balance Fe, - 50 wt% Ni, 11 wt% Cr, balance Fe, 50% by weight Ni, 9% by weight Cr, max. 1% by weight Si and max. 1% by weight Mn, balance Fe; 50% by weight Ni, 10% by weight Cr, max. 1% by weight Si and max. 1% by weight Mn, balance Fe; The bilayer susceptor arrangement of any one of Examples 1-8, comprising or consisting of one of: 50 wt.% Ni, 11 wt.% Cr, up to 1 wt.% Si, and up to 1 wt.% Mn, the balance being Fe.

[0078] Example 10: A two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising: a first layer including or consisting of a first susceptor material; and a second layer including or consisting of a second susceptor material, the first and second layers being intimately connected to each other; the second susceptor material including or consisting of a Ni-Fe alloy having a Ni content of 65 wt. % or less and a Cr content of 13 wt. % or more; and the layer thickness of the second layer being in the range of 1 micrometer to 22 micrometers.

[0079] Example 11 The bilayer susceptor arrangement of Example 10, wherein the layer thickness of the second layer is in the range of 1 micrometer to 15 micrometers, specifically 4 micrometers to 15 micrometers, or 1 micrometer to 11 micrometers, more specifically 4 micrometers to 11 micrometers.

[0080] Example 12 A bilayer susceptor arrangement as described in one of Examples 10 or 11, wherein the Ni-Fe alloy of the second susceptor material has a Ni content of 50 wt% or less, specifically 44 wt% or less, more specifically in the range of 36 wt% to 44 wt%, preferably in the range of 36 wt% to 40 wt%, for example 36.1 wt% or 36.4 wt% or 40 wt%.

[0081] Example 13: The two-layer susceptor arrangement according to any one of Examples 10 to 12, wherein the thickness of the first layer is within a range of about 1.5 to 5 times, specifically 2 to 4 times, preferably 2.5 to 3.5 times, and more preferably about 3 times the thickness of the second layer.

[0082] Example 14 The bilayer susceptor arrangement of any one of Examples 10-13, wherein the first susceptor material comprises or consists of a metal, such as ferritic iron, or stainless steel, specifically grade 410, grade 420, or grade 430 stainless steel.

[0083] Example 15 The two-layer susceptor arrangement according to any one of Examples 1 to 14, wherein the Ni-Fe alloy of the second susceptor material has a Curie temperature in the range of 180°C to 420°C, specifically 210°C to 380°C, preferably 250°C to 380°C.

[0084] Example 16 The two-layer susceptor arrangement according to any one of Examples 1 to 15, wherein the layer thickness of the first layer is in the range of 20 micrometers to 60 micrometers, specifically 30 micrometers to 50 micrometers, for example 40 micrometers to 42.5 micrometers.

[0085] Example 17 The bilayer susceptor arrangement of any one of Examples 1-16, wherein the susceptor arrangement has the form of a blade or strip or sheet.

[0086] Example 18: The bilayer susceptor arrangement of any one of Examples 1 to 17, wherein the overall thickness of the susceptor arrangement is in the range of 31 micrometers to 85 micrometers, specifically 50 micrometers to 60 micrometers, for example 56.5 micrometers, or the overall thickness of the susceptor arrangement is in the range of 21 micrometers to 64 micrometers, specifically 31 micrometers to 54 micrometers, for example 45 micrometers, or the overall thickness of the susceptor arrangement is in the range of 21 micrometers to 75 micrometers, or 21 micrometers to 82 micrometers, specifically 24 micrometers to 71 micrometers, more specifically 44 micrometers to 55 micrometers.

[0087] Example 19: A two-layer susceptor arrangement according to any one of Examples 1 to 18, wherein the width of the susceptor arrangement in a direction perpendicular to the overall thickness of the susceptor arrangement is in the range of 3 millimeters to 7 millimeters, specifically 4 millimeters to 6 millimeters, for example 5 millimeters.

[0088] Example 20: A two-layer susceptor arrangement according to any one of Examples 1 to 19, wherein the length of the susceptor arrangement in a direction perpendicular to the overall thickness of the susceptor arrangement is in the range of 10 millimeters to 15 millimeters, specifically 11 millimeters to 13 millimeters, for example 12 millimeters.

[0089] Example 21 An inductively heatable aerosol-generating article comprising an aerosol-forming substrate and the two-layer susceptor arrangement according to any one of Examples 1 to 20.

[0090] Example 22 An aerosol-generating article according to Example 21, wherein the two-layer susceptor arrangement is embedded within the aerosol-forming substrate.

[0091] Example 23 An aerosol generating system comprising an inductively heatable aerosol-generating article according to either Example 21 or Example 22, and an inductively heatable aerosol generator for use with the aerosol-generating article.

[0092] Example 24: An aerosol generating system comprising an induction heating aerosol generating device and an aerosol-generating article for use with the aerosol generating device, wherein the aerosol generating device comprises the two-layer susceptor arrangement described in any one of Examples 1 to 20, and the aerosol-generating article comprises an aerosol-forming substrate to be heated by the two-layer susceptor arrangement.

[0093] The embodiments will now be further described with reference to the figures. [Brief explanation of the drawings]

[0094] [Figure 1]FIG. 1 illustrates schematically one exemplary embodiment of an inductively heatable aerosol-generating article comprising a two-layer susceptor arrangement according to the present invention. [Figure 2] FIG. 2 illustrates schematically an exemplary embodiment of an aerosol-generating system comprising an aerosol-generating article according to FIG. [Figure 3] FIG. 3 shows in perspective view a detail of the two-layer susceptor arrangement of the aerosol-generating article of FIG. [Figure 4] FIG. 4 shows in cross-section a detail of the two-layer susceptor arrangement of the aerosol-generating article of FIG. [Figure 5] FIG. 5 shows a detailed perspective view of an exemplary embodiment of a two-layer susceptor arrangement according to a second aspect of the present invention. [Figure 6] FIG. 6 shows a detail of the two-layer susceptor arrangement according to FIG. 5 in a cross-sectional view. DETAILED DESCRIPTION OF THE INVENTION

[0095] FIG. 1 illustrates, in a schematic representation (not to scale), one exemplary embodiment of an inductively heatable aerosol-generating article 100 according to the present invention. The aerosol-generating article 100 is a substantially rod-shaped consumable product comprising five elements arranged consecutively in coaxial alignment: a distal forward plug element 150, a base element 110, a first tube element 140, a second tube element 145, and a filter element 160. The distal forward plug element 150 is disposed at the distal end 102 of the article 100 and covers and protects the distal forward end of the base element 110, while the filter element 160 is disposed at the proximal end 103 of the article 100. Both the distal forward plug element 150 and the filter element 160 may be made of the same filter material. The filter element 160 preferably functions as a mouthpiece, preferably as part of the mouthpiece together with the second tube element 145. The filter element 160 may have a length of 10 to 14 millimeters, e.g., 12 millimeters, while the distal front plug element 150 may have a length of 3 to 6 millimeters, e.g., 5 millimeters. The base element 110 comprises not only the aerosol-forming substrate 130 to be heated, but also a two-layer susceptor arrangement 120 according to an exemplary embodiment of the present invention for heating the substrate 130. The susceptor arrangement 120 has the form of a blade or strip that is fully embedded within the substrate 130 so as to be in direct thermal contact with the substrate 130. The base element 110 may have a length of 10 to 14 millimeters, e.g., 12 millimeters. As shown in FIG. 1, the susceptor arrangement 120 extends along the entire length of the base element 110, but may alternatively have an extension 110 with a length shorter than the length of the base element. Each of the first and second pipe elements 140, 145 is a hollow cellulose acetate tube having a central air passage 141, 146, the cross section of which is larger than the cross section of the central air passage 141 of the first pipe element 140. The first and second pipe elements 140, 145 may have a length of 6 to 10 millimeters, for example 8 millimeters. Each of the aforementioned elements 150, 110, 140, 145, 160 may be substantially cylindrical.Specifically, all elements 150, 110, 140, 145, 160 may have the same external cross-sectional shape and dimensions.

[0096] Additionally, elements 150, 110, 140, 145, 160 may be surrounded by one or more outer wrappers, such as to hold the elements together and maintain the desired cross-sectional shape of the rod-shaped article. In this embodiment, distal forward plug element 150, base element 110, and first tube element 171 are surrounded by first wrapper 140, while second tube element 145 and filter element 160 are surrounded by second wrapper 172. Second wrapper 172 also surrounds at least a portion of first tube element 140 (after being wrapped by first wrapper 171) to connect distal forward plug element 150, base element 110, and first tube element 140, which are surrounded by first wrapper 171, to second tube element 145 and filter element 160. First wrapper 171 and second wrapper 172 are preferably made of paper. Additionally, the second wrapper 172 may include perforations around its periphery (not shown). The wrappers 171, 172 may further include an adhesive that adheres the overlapping free ends of the wrappers 171, 172 to one another.

[0097] As shown in FIG. 2 , the aerosol-generating article 100 is configured for use with an induction heating aerosol-generating device 10. The device 10 and the article 100 together form an aerosol-generation system 1 according to the present invention. The aerosol-generating device 10 includes a cylindrical receiving cavity 20 defined within a proximal portion 12 of the device 10, for receiving at least a distal portion of the article 100 therein. The device 10 further includes an induction heating arrangement including an induction coil 30 for generating a high-frequency alternating magnetic field within the cavity 20. In this embodiment, the induction coil 30 is a helical coil that circumferentially surrounds the cylindrical receiving cavity 20. The coil 30 is arranged such that the susceptor arrangement 120 of the aerosol-generating article 100 is exposed to the alternating magnetic field upon insertion of the article 100 into the cavity 20 of the device 10. Thus, upon activation of the induction heating arrangement, depending on the magnetic and electrical properties of the susceptor material of the susceptor arrangement 120, the susceptor arrangement 120 heats due to eddy currents and / or hysteresis losses induced by the alternating magnetic field. The susceptor arrangement 120 is heated until it reaches an operating temperature sufficient to vaporize the aerosol-forming substrate 130 surrounding the susceptor arrangement 120 within the article 100. In use, an aerosol formed by volatile compounds released from the heated substrate 130 is drawn through the first and second tube elements 140, 145, and further through the filter element 160 toward the proximal end 103 of the article 100.

[0098] Within the distal portion 13, the aerosol generating device 10 further comprises a DC power supply 40 and a controller 50 (shown only diagrammatically in FIG. 2) for supplying power and controlling the heating process. Apart from the induction coil 30, the induction heating arrangement is preferably an at least partially integral part of the controller 50.

[0099] 3 and 4 show detailed views (not to scale) of the susceptor arrangement 120 used in the aerosol-generating article shown in FIG. 1. According to the present invention, the susceptor arrangement 120 is a two-layer susceptor arrangement 120 consisting of a first layer 121 and a second layer 122 that are intimately connected to each other. Thus, the first layer 121 and the second layer 122 each form an edge layer of the susceptor arrangement 120. In manufacturing, the susceptor arrangement 120 may be formed, for example, by cladding the material of the second layer 122 onto the material of the first layer 121.

[0100] The first layer 121 is primarily used for heating purposes. To this end, it consists of a first susceptor material optimized for heat loss and therefore heating efficiency. At hand, the first susceptor material is a 400 series stainless steel (such as grade 410 stainless steel, or grade 420 stainless steel, or grade 430 stainless steel, or a similar grade stainless steel). The use of stainless steel proves advantageous with regard to the aging properties of the first layer 121, which is in direct contact with the aerosol-forming substrate 130 in the base element 110.

[0101] While the first layer 121 is primarily used to heat the substrate 130, the second layer 122 is a functional layer that primarily functions as a temperature marker. To this end, the second layer 122 includes a ferromagnetic second susceptor material selected to have a Curie temperature corresponding to a predetermined temperature point for heating the substrate 130. At that Curie temperature, the magnetic permeability of the second susceptor material drops to 1, leading to a change in its magnetic properties from ferromagnetic to paramagnetic. This change in magnetic properties is accompanied by a temporary change in the electrical resistance of the susceptor arrangement 120. Therefore, by monitoring the corresponding change in current absorbed by the induction heating arrangement of the apparatus 10, it is possible to detect when the second susceptor material has reached its Curie temperature, and therefore, when the predetermined temperature point has been reached.

[0102] As defined above, the second susceptor material comprises or consists of a Ni-Fe alloy with a Ni content of 65% by weight or less. On the other hand, the Ni-Fe alloy contains 50% by weight Ni, 9% by weight Cr, and the remainder Fe. This alloy is commercially available, for example, under the trade name Phytherm 260, and has a Curie temperature of 260°C. If a lower Curie temperature is desired, the Ni-Fe alloy may alternatively comprise or consist of 50% by weight Ni, 10% by weight Cr, and the remainder Fe. This alloy has a Curie temperature of 230°C and is commercially available, for example, under the trade name Phytherm 220. According to yet another alternative, the Ni-Fe alloy may comprise or consist of 50% by weight Ni, 11% by weight Cr, and the remainder Fe. This alloy is also commercially available, for example, under the trade name Phytherm 210, and has a Curie temperature of 210°C. Advantageously, all of the aforementioned alloys (Phytherm alloys) are corrosion resistant materials.

[0103] According to the first aspect of the present invention, the layer thickness of the second layer 122 can be relatively small, i.e., in the range of 11 micrometers to 25 micrometers, particularly 11 micrometers to 18 micrometers, more particularly 11 micrometers to 16 micrometers, or 12 micrometers to 18 micrometers, 13 micrometers to 18 micrometers, or 12 micrometers to 16 micrometers, or 13 micrometers to 16 micrometers, which proves beneficial in terms of material savings and therefore makes the manufacture of the susceptor arrangement 120 more cost-effective. At the same time, the layer thickness in the range is large enough to ensure that the temperature marker function is still sufficiently noticeable for reliable temperature detection. Meanwhile, the layer thickness of the second layer 122 of the susceptor arrangement 120 shown in FIGS. 1-4 is approximately 14 micrometers, while the layer thickness of the first layer 121 is approximately 42.5 micrometers.

[0104] According to a second embodiment of the present invention, it has been found that there are other advantages when the layer thickness of the second layer is even smaller, i.e., 4 micrometers or less. A two-layer susceptor arrangement 220 having such a small layer thickness of the second layer 222 is shown in FIGS. 5 and 6. Similar to the thickness range of the susceptor arrangement 120 according to the first embodiment of the present invention, the thickness range of the susceptor arrangement 220 according to the second embodiment of the present invention proves beneficial in terms of material and cost savings. In addition, a layer thickness of the second layer 222 of 4 micrometers or less is also advantageous in terms of dimensional stability of the susceptor arrangement 220. This is because the second layer 222, which has such a small layer thickness compared to the first layer 221, cannot cause thermal bending of the susceptor assembly 220 due to differences in thermal expansion between the first layer 221 and the second layer 222. On the other hand, the layer thickness of the second layer 222 of the susceptor arrangement 220 shown in FIGS. 5-6 is about 2.5 micrometers, while the layer thickness of the first layer 221 is about 42.5 micrometers.

[0105] As can be seen particularly in Figures 3 and 5, the bilayer susceptor arrangements 120, 220 according to both embodiments are in the form of elongated strips. The strip-like susceptor arrangements 120, 220 have a length L of 10-12 millimeters and a width W of 4-5 millimeters. That is, both layers 121, 122, 221, 222 have a length L of 10-12 millimeters and a width W of 4-5 millimeters, yet have different layer thicknesses. Considering the above values ​​for the respective layer thicknesses, the total thickness T of the susceptor arrangement 120 shown in Figures 1-4 is approximately 56.5 micrometers, while the total thickness T of the susceptor arrangement 220 shown in Figures 5-6 is approximately 45 micrometers.

[0106] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified by the term "about." Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A ± 5%. Within this context, the number A may be considered to include a numerical value that is within the typical standard error for the measurement of the property that the number A modifies. In some cases, as used in the appended claims, the number A may deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. 1. A two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first layer and the second layer being intimately connected to each other, the second susceptor material including or consisting of a Ni—Fe alloy having a Ni content of 65 wt % or less, and the layer thickness of the second layer being in the range of 11 micrometers to 18 micrometers.

2. 10. The bilayer susceptor arrangement of claim 1, wherein the layer thickness of the second layer is in the range of 11 micrometers to 16 micrometers, 12 micrometers to 18 micrometers, 13 micrometers to 18 micrometers, 12 micrometers to 16 micrometers, or 13 micrometers to 16 micrometers.

3. 1. A two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first layer and the second layer being intimately connected to each other, the second susceptor material including or consisting of a Ni—Fe alloy having a Ni content of 65 wt % or less, and the second layer having a layer thickness of 4 micrometers or less.

4. The bilayer susceptor arrangement of claim 3, wherein the layer thickness of the second layer is in the range of 1 micrometer to 4 micrometers.

5. 5. The bilayer susceptor arrangement of claim 1, wherein the Ni—Fe alloy of the second susceptor material further comprises 8 wt % to 12 wt % Cr, specifically 9 wt % to 11 wt % Cr.

6. 6. A bilayer susceptor arrangement according to any one of claims 1 to 5, wherein the Ni-Fe alloy of the second susceptor material has a Ni content of 50 wt% or less, particularly 44 wt% or less, more particularly in the range of 36 wt% to 44 wt%, preferably in the range of 36 wt% to 40 wt%, for example 36.1 wt% or 36.4 wt% or 40 wt%, the remainder being preferably Fe.

7. The Ni—Fe alloy of the second susceptor material is 50% by weight Ni, 9% by weight Cr, the remainder being Fe, 50% by weight Ni, 10% by weight Cr, the remainder being Fe, 50% by weight Ni, 11% by weight Cr, the remainder being Fe, 50% by weight Ni, 9% by weight Cr, max. 1% by weight Si and max. 1% by weight Mn, the balance being Fe; 50% by weight Ni, 10% by weight Cr, max. 1% by weight Si and max. 1% by weight Mn, the balance being Fe; 6. The bilayer susceptor arrangement of any one of claims 1 to 5, comprising or consisting of -50 wt% Ni, 11 wt% Cr, max 1 wt% Si and max 1 wt% Mn, the remainder being Fe.

8. 1. A two-layer susceptor arrangement for inductively heating an aerosol-forming substrate, the susceptor arrangement comprising a first layer including or consisting of a first susceptor material and a second layer including or consisting of a second susceptor material, the first layer and the second layer being intimately connected to each other, the second susceptor material including or consisting of a Ni—Fe alloy having a Ni content of 65 wt % or less and a Cr content of 13 wt % or more, and the layer thickness of the second layer being in the range of 1 micrometer to 22 micrometers.

9. 9. The bilayer susceptor arrangement of claim 8, wherein the layer thickness of the second layer is in the range of 1 micrometer to 15 micrometers, specifically 4 micrometers to 15 micrometers, or 1 micrometer to 11 micrometers, more specifically 4 micrometers to 11 micrometers.

10. 10. A bilayer susceptor arrangement according to claim 8 or 9, wherein the Ni-Fe alloy of the second susceptor material has a Ni content of not more than 50 wt%, particularly not more than 44 wt%, more particularly in the range of 36 wt% to 44 wt%, preferably in the range of 36 wt% to 40 wt%, for example 36.1 wt% or 36.4 wt% or 40 wt%, the remainder being preferably Fe.

11. 11. The two-layer susceptor arrangement according to claim 1, wherein the layer thickness of the first layer is in the range of 1.5 to 5 times, in particular 2 to 4 times, preferably 2.5 to 3.5 times, more preferably about 3 times the layer thickness of the second layer.

12. 12. The bilayer susceptor arrangement of claim 1, wherein the first susceptor material comprises or consists of a metal, such as ferritic iron, or stainless steel, in particular grade 410, grade 420, or grade 430 stainless steel.

13. 13. The bilayer susceptor arrangement according to any one of claims 1 to 12, wherein the Ni-Fe alloy of the second susceptor material has a Curie temperature in the range of 180°C to 420°C, particularly 210°C to 380°C, preferably 250°C to 380°C.

14. 14. The bilayer susceptor arrangement of claim 1, wherein the layer thickness of the first layer is in the range of 20 micrometers to 60 micrometers, particularly 30 micrometers to 50 micrometers, such as 40 micrometers or 42.5 micrometers.

15. The bilayer susceptor arrangement of any one of claims 1 to 14, wherein the susceptor arrangement has the form of a blade or a strip or a sheet.

16. An inductively heatable aerosol-generating article comprising an aerosol-forming substrate and the two-layer susceptor arrangement of any one of claims 1 to 15.

17. 17. An aerosol generating system comprising an inductively heatable aerosol-generating article according to claim 16 and an inductively heated aerosol generator for use with the aerosol-generating article.

18. 16. An aerosol generation system comprising an induction-heated aerosol generator and an aerosol-generating article for use in the aerosol-generating apparatus, the aerosol-generating apparatus comprising the two-layer susceptor arrangement of any one of claims 1 to 15, and the aerosol-generating article comprising an aerosol-forming substrate heated by the two-layer susceptor arrangement.

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