AEROSOL-GENERATING DEVICE FOR GENERATING AN AEROSOL BY INDUCTIVE HEATING OF AN AEROSOL-FORMING SUBSTRATE

Abstract

An aerosol-generating device for generating an aerosol by inductive heating of an aerosol-forming substrate is provided, the device including: a device housing including a cavity to removably receive the substrate; an inductive heating arrangement including an induction coil to generate a varying magnetic field within the cavity and being arranged around at least a portion of the cavity; and a flux concentrator arranged around at least a portion of the coil and being configured to distort the field of the arrangement towards the cavity, the flux concentrator including a multi-layer flux concentrator foil having a magnetic layer laminated with at least a first support layer, the magnetic layer including a plurality of separated fragments of a soft magnetic alloy and being arranged in a pattern including a plurality of crack centers, and a plurality of cracks spread radially outwards from each crack center in a web-shaped pattern.

Claims

1.-15. (canceled)

16. An aerosol-generating device for generating an aerosol by inductive heating of an aerosol-forming substrate, the aerosol-generating device comprising: a device housing comprising a cavity configured to removably receive the aerosol-forming substrate to be heated; an inductive heating arrangement comprising at least one induction coil configured to generate a varying magnetic field within the cavity, wherein the at least one induction coil is arranged around at least a portion of the cavity; and a flux concentrator arranged around at least a portion of the induction coil and being configured to distort the varying magnetic field of the inductive heating arrangement towards the cavity, wherein the flux concentrator comprises a multi-layer flux concentrator foil having at least one magnetic layer laminated with at least a first support layer, wherein the magnetic layer comprises a plurality of separated fragments of a soft magnetic alloy, wherein the plurality of separated fragments are arranged in a pattern comprising a plurality of crack centers, and wherein a plurality of cracks spread radially outwards from each crack center in a web-shaped pattern.

17. The aerosol-generating device according to claim 16, wherein the soft magnetic alloy is a metallic glass or a nanocrystalline soft magnetic Fe-based alloy.

18. The aerosol-generating device according to claim 16, wherein the soft magnetic alloy comprises a composition of Fe.sub.100-a-b-c-x-y-zCu.sub.aM.sub.bT.sub.cSi.sub.xZ.sub.z and up to 0.5 atom % contaminants, wherein M is one or more of the group consisting of Nb, Mo, and Ta, T is one or more of the group consisting of V, Cr, Co, and Ni, and Z is one or more of the group consisting of C, P, and Ge, and wherein 0.5 atom %<a<1.5 atom %, 2 atom %≤b<4 atom %, 0 atom %≤c<5 atom %, 12 atom %<x<18 atom %, 5 atom %<y<12 atom %, and 0 atom %≤z<2 atom %.

19. The aerosol-generating device according to claim 16, wherein the multi-layer flux concentrator foil comprises a plurality of adjacent magnetic layers.

20. The aerosol-generating device according to claim 16, wherein the multi-layer flux concentrator foil comprises a second support layer on a side of the at least one magnetic layer or the plurality of adjacent magnetic layers opposite to the first support layer.

21. The aerosol-generating device according to claim 16, wherein at least one of the first support layer and the second support layer is one of an adhesive layer, an electrically insulating layer, or an electrically insulating adhesive layer.

22. The aerosol-generating device according to claim 16, wherein gaps between the plurality of separated fragments are at least partially filled with an electrically insulating material.

23. The aerosol-generating device according to claim 16, wherein gaps between the plurality of separated fragments are at least partially filled with at least one of material of the first support layer, or material of the second support layer, or material of the adhesive film between the adjacent magnetic layers, or with matrix material of the soft magnetic alloy.

24. The aerosol-generating device according to claim 16, wherein between the induction coil and the flux concentrator a first dielectric wrapper is arranged around at least a portion of the induction coil.

25. A method for manufacturing a multi-layer flux concentrator foil of an aerosol-generating device according to claim 16, the method comprising: providing a multi-layer flux concentrator foil having at least one magnetic layer of a soft magnetic alloy laminated with at least a first support layer; cracking the magnetic layer into a plurality of separated fragments by applying an external force to the flux concentrator foil transvers to the foil plane; and stretching the flux concentrator foil by pulling the flux concentrator foil under a tensile force parallel to the foil plane.

26. The method according to claim 25, wherein the cracking the magnetic layer into a plurality of separated fragments comprises passing the flux concentrator foil through at least one pair of rollers, which apply a pressure force onto the flux concentrator foil passing therethrough, wherein at least one of the rollers comprises a plurality of protrusions on an outer surface thereof.

27. The method according to claim 26, wherein the respective other roller comprises a smooth outer surface, or wherein each of the rollers comprises a plurality of protrusions on an outer surface thereof.

28. The method according to claim 25, wherein the pulling the flux concentrator foil comprises pulling the flux concentrator foil under a tensile force parallel to the foil plane over at least one edge, in particular over one edge only.

29. The method according to claim 25, wherein the pulling the flux concentrator foil comprises pulling the flux concentrator foil under a tensile force parallel to the foil plane over one edge only.

30. The method according to claim 25, further comprising pulling the flux concentrator foil under a tensile force parallel to the foil plane over at least one roller for bending the flux concentrator foil.

31. The method according to claim 25, further comprising pulling the flux concentrator foil under a tensile force parallel to the foil plane over a sequence of rollers for bending the flux concentrator foil.

32. The method according to claim 25, further comprising cutting the flux concentrator foil to a predetermined size.

33. The method according to claim 32, further comprising sealing one or more cut edges of the flux concentrator foil cut to size.

Description

[0203] Examples will now be further described with reference to the figures in which:

[0204] FIG. 1 shows a schematic longitudinal cross-section of an aerosol-generating system in accordance with a first embodiment the present invention;

[0205] FIG. 2 is a detail view of the induction module according to FIG. 1;

[0206] FIGS. 3, 4a-4b show details of the multi-layer flux concentrator foil used in the device according to FIG. 1;

[0207] FIGS. 5-8 show different arrangements of a flux concentrator foil according to the present invention;

[0208] FIG. 9 schematically illustrates an exemplary embodiment of a multi-layer flux concentrator foil comprising a plurality of magnetic layers.

[0209] FIG. 10 is a detail view of an induction module according to a second embodiment the present invention;

[0210] FIG. 11 shows a schematic longitudinal cross-section of an aerosol-generating system in accordance with another embodiment the present invention;

[0211] FIGS. 12-15 exemplarily illustrate various steps of the method according to the present invention;

[0212] FIG. 16 shows details of another example of a multi-layer flux concentrator foil which can be used in the device according to FIG. 1 and which comprises a plurality of magnetic layers; and

[0213] FIG. 17 shows the multi-layer flux concentrator foil according to FIG. 16 being sealed by a sealing adhesive tape.

[0214] FIG. 1 shows a schematic cross-sectional illustration of a first exemplary embodiment of an aerosol-generating system 1 according to the present invention. The system 1 is configured for generating an aerosol by inductively heating an aerosol-forming substrate 91. The 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 the article 90. The device 10 comprises a receiving cavity 20 for receiving the article 90, and an inductive heating arrangement for heating the substrate 91 within the article 90 when the article 90 is inserted into the cavity 20.

[0215] The article 90 has a rod shape resembling the shape of a conventional cigarette. In the present embodiment, the article 90 comprises four elements arranged in coaxial alignment: a substrate element 91, a support element 92, an aerosol-cooling element 94, and a filter plug 95. The substrate element is arranged at a distal end of the article 90 and comprises the aerosol-forming substrate to be heated. The aerosol-forming substrate 91 may include, for example, a crimped sheet of homogenized tobacco material including glycerin as an aerosol-former. The support element 92 comprises a hollow core forming a central air passage 93. The filter plug 95 serves as a mouthpiece and may include, for example, cellulose acetate fibers. All four elements are substantially cylindrical elements being arranged sequentially one after the other. The elements substantially have the same diameter and are circumscribed by an outer wrapper 96 made of cigarette paper such as to form a cylindrical rod. The outer wrapper 96 may be wrapped around the aforementioned elements so that free ends of the wrapper overlap each other. The wrapper may further comprise adhesive that adheres the overlapped free ends of the wrapper to each other.

[0216] 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 supply 16, for example a lithium ion battery, and an electric circuitry 17 including a controller for controlling operation of the device 10, in particular for controlling the heating process. Within a proximal portion 14 opposite to the distal portion 13, the device 10 comprises the receiving cavity 20. The cavity 20 is open at the proximal end 12 of device 10, thus allowing the article 90 to be readily inserted into the receiving cavity 20.

[0217] 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, in particular from the receiving cavity 20. Preferably, the bottom portion is made of a thermally insulating material, for example, PEEK (polyether ether ketone). Thus, electric components within the distal portion 13 may be kept separate from aerosol or residues produced by the aerosol generating process within the cavity 20.

[0218] The inductive heating arrangement of the device 10 comprises an induction source including an induction coil 31 for generating an alternating, in particular high-frequency varying magnetic field. In the present embodiment, the induction coil 31 is a helical coil circumferentially surrounding the cylindrical receiving cavity 20. The induction coil 31 is formed from a wire and has a plurality of turns, or windings, extending along the length extension of the cavity 20. The wire may have any suitable cross-sectional shape, such as square, oval, or triangular. In this embodiment, the wire has a circular cross-section. In other embodiments, the wire may have a flat cross-sectional shape.

[0219] The inductive heating arrangement further comprises a susceptor element 60 that is arranged within the receiving cavity 20 such as to experience the varying magnetic field generated by the induction coil 31. In the present embodiment, the susceptor element 60 is a susceptor blade 61. With its distal end 64, the susceptor blade is arranged at the bottom portion 21 of the receiving cavity 20 of the device. From there, the susceptor blade 61 extends into the inner void of the receiving cavity 20 towards the opening of the receiving cavity 20 at the proximal end 12 of the device 10. The other end of the susceptor blade 60, that is, the distal free end 63 is tapered enabling the susceptor blade to penetrate the aerosol-forming substrate 91 within the distal end portion of the article 90.

[0220] When the device 10 is actuated, a high-frequency alternating current is passed through the induction coil 31. This causes the coil 31 to generate a varying magnetic field within the cavity 20. As a consequence, the susceptor blade 61 heats up due to eddy currents and/or hysteresis losses, depending on the magnetic and electric properties of the materials of the susceptor element 60. The susceptor 60 in turn heats the aerosol-forming substrate 91 of the article 90 to a temperature sufficient to form an aerosol. The aerosol may be drawn downstream through the aerosol-generating article 90 for inhalation by the user.

[0221] The high-frequency varying magnetic field may be in the range between 500 kHz (kilo-Hertz) to 30 MHz (Mega-Hertz), in particular between 5 MHz (Mega-Hertz) to 15 MHz (Mega-Hertz), preferably between 5 MHz (Mega-Hertz) and 10 MHz (Mega-Hertz).

[0222] In the present embodiment, the induction coil 31 is part of an induction module 30 that is arranged with the proximal portion 14 of the aerosol-generating device 10. The induction module 30 has a substantially cylindrical shape that is coaxially aligned with a longitudinal center axis C of the substantially rod-shaped device 10. As can be seen from FIG. 1, the induction module 30 forms a least a portion of the cavity 20 or at least a portion of an inner surface of the cavity 20.

[0223] FIG. 2 shows the induction module 30 in more detail. Besides the induction coil 31, the induction module 30 comprises a tubular inner support sleeve 32 which carries the helically wound, cylindrical induction coil 31. At one end, the tubular inner support sleeve 32 has an annular protrusion 34 extending around the circumference of the inner support sleeve 32 to retain the coil 31 in position on the inner support sleeve 32. The inner support sleeve 32 may be made from any suitable material, such as a plastic. In particular, the inner support sleeve 32 may be a least a portion of the cavity 20, that is, at least a portion of an inner surface of the cavity 20.

[0224] Both the induction coil 31 and the inner support sleeve 32 (apart from the protrusion 34) are surrounded by a tubular flux concentrator 33 which extends along the length of the induction coil 3, which may be in the range of 16 millimeter to 18 millimeter. The flux concentrator 33 is configured to distort the varying magnetic field generated by the induction coil 31 during use of the device 10 towards the cavity 20. Basically, the flux concentrator 33 acts as a magnetic shield in order to reduce undesired heating of or interference with external objects. In addition, the flux concentrator 33 courses the magnetic field lines within the inner volume of the induction module 30 to be distorted so that the density of the magnetic field within the cavity 20 is increased. This may increase the current generated within the susceptor blade 61 located in the cavity 20. In this manner, the electromagnetic field can be concentrated towards the cavity 20 to allow for more efficient heating of the susceptor element 60.

[0225] According to the invention, the flux concentrator 33 is made of a multi-layer flux concentrator foil 35. FIG. 3 (not to scale) and FIG. 4a-4b show a respective portion of the multi-layer flux concentrator foil 35 in more detail. FIG. 3 is a cross-sectional view through the multi-layer flux concentrator foil 35. FIG. 4a is a black-white photograph of a portion of a specimen of the magnetic layer 36. FIG. 4b shows the magnetic layer 36 according to FIG. 4a with inverted colors in order to enhance the visibility of the cracks and fragments 39. As shown in FIG. 3, the multi-layer flux concentrator foil 35 according to the present invention comprises three layers, namely, a magnetic layer 36 of a soft magnetic alloy, a first support layer 37 and a second support layer 36, wherein the magnetic layer 36 is laminated between the first support layer 37 and the second support layer 38. According to the invention, the magnetic layer 36 comprises a plurality of separated fragments 39. Due to the fragmentation, the formation of eddy currents in the magnetic layer 36 is partially inhibited as the flake-like fragments 39 are separated from each other and as every single fragment 39 thus provides only limited space for eddy currents to form up. Hence, as compared to a non-fragmented magnetic layer, the fragmented magnetic layer 36 has a reduced AC resistance. As a result, when exposed to a varying magnetic field, there is no or only little energy dissipation in the fragments 39 causing the flux concentrator foil 35 as a whole to heat up only slightly, if at all. Hence, the vast majority of the energy provided by the varying magnetic field can be dissipated in the susceptor. As shown in FIG. 4a-4b, the plurality of separated fragments 39 may be arranged in a pattern comprising a plurality of crack centers, wherein a plurality of cracks spread radially outwards from each crack center in a web-shaped pattern. As can be seen, the separated fragments each have different fragment sizes. A mean fragment size may be at most 1 millimeter, in particular at most 500 micrometer.

[0226] Preferably, the soft magnetic alloy is a nanocrystalline soft magnetic alloy, for example, made of Vitroperm 800. Vitroperm 800 has a maximum relative magnetic permeability of more than 20.0000 at a magnetic field frequency of 50 Hertz. Accordingly, this material is particularly suited to concentrate and guide the magnetic field generated by an induction coil. Furthermore, Vitroperm 800 is rather brittle and thus easy to crack into a plurality fragments.

[0227] The first support layer 37 and the second support layer 38 basically serve to protect the brittle magnetic layer 36, in particular to prevent the fragmented magnetic layer 36 to crumble away by bonding the fragments 39 of the magnetic layer 36 in a laminate structure. For that purpose, the first support layer 37 and the second support layer 38 preferably are adhesive layers. For example, the first and second support layers 37, 38 may be made of transparent glue or plastic tape. Preferably, the material of the first and second support layer 37, 38 is electrically insulating in order to prevent short-circuiting of the separated fragments 39.

[0228] In the present embodiment, the magnetic layer 36 may have a layer thickness of 20 micrometer. The first support layer 37 and the second support layer 38 may each have a layer thickness of 22 micrometer. Accordingly, the flux concentrator for 35 as a whole may have a thickness of 64 micrometer.

[0229] In the embodiment shown in FIG. 1 and FIG. 2, the flux concentrator for 35 is wound up in a single winding such as to form a tubular flux concentrator or a flux concentrator sleeve which comprises a single winding of the flux concentrator foil 35 surrounding the induction coil 31. In principle, the flux concentrator foil 35 may be wound up in different ways around the induction coil 31. According to a first embodiment, the flux concentrator foil 35 may be wound up with its free ends 351 abutting against each other as shown in FIG. 5. That is, the longitudinal edges of the flux concentrator foils 35 which extend along the length axis of C of the aerosol-generating device 10 abut against each other. According to a second embodiment, the flux concentrator foil 35 may be wound up with free ends 351 overlapping each other as shown in FIG. 6. That is, the longitudinal edges of the flux concentrator foil 35 which extend along the length axis of C of the aerosol-generating device 10 abut against each other. According to a third embodiment as shown in FIG. 7, the flux concentrator foil 35 may be wound up in multiple windings such as to form a tubular flux concentrator or a flux concentrator sleeve comprising multiple, in particular spiral windings of a flux concentrator foil overlapping each other. According to a fourth embodiment as shown in FIG. 8, the flux concentrator foil 35, 13 may also be wound up helically in an axially direction with respect to winding axis, that is, along the length axis of C of the aerosol-generating device, such as to form a tubular flux concentrator or a flux concentrator sleeve comprising one or more helical windings of a flux concentrator foil 35, 135.

[0230] FIG. 9 shows a second embodiment of the multi-layer flux concentrator foil 235. As compared to the embodiment shown in FIG. 2 and FIG. 3, the multi-layer flux concentrator foil 235 according to FIG. 9 comprises a plurality of magnetic layers 236 laminated between a first support layer 237 and a second support layer 238. In addition, an electrically insulating adhesive film 270 is arranged between each pair of adjacent magnetic layers 236. In particular with regard to the multiple-winding configuration shown in FIG. 7 and FIG. 8, the plurality of magnetic layers 236 may limit the number of turns necessary to be wound up. Advantageously, this may simplify the manufacturing of the flux concentrator.

[0231] Again with reference to FIG. 1 and FIG. 2, the flux concentrator foil 35 is directly wrapped around the induction coil 31 substantially without any radial spacing between the induction coil 31 and the flux concentrator foil 35.

[0232] FIG. 10 shows another embodiment of the induction module 130, in which the flux concentrator foil 135 is radially spaced apart from the induction coil 131. That is, the aerosol-generating device comprises a radial gap 181 between the induction coil 131 and the flux concentrator foil 135. In the present embodiment, the gap 181 is filled with a first dielectric wrapper 182. For example, the induction coil 131 may be wrapped by one or more layers of Kapton tape 182 such as to fill the radial gap 181 between the induction coil 131 and the flux concentrator 133. The gap 181 or the first dielectric wrapper 182, respectively, may have a radial extension in a range between 40 micrometers and 240 micrometers, for example 80 micrometers. Advantageously, the gap 181 may help to reduce losses in the induction coil and to increase losses in the susceptor to be heated, that is, to increase the heating efficiency of the aerosol-generating device. Alternatively, the gap may be an air gap. Furthermore, the induction module 130 according to FIG. 10 comprises an electrically conductive shielding wrapper 183 that is arranged around the flux concentrator in order to provide an additional shielding of the outer portions of the device by electrically closing the field loop. For example, the conductive shielding wrapper 180 may be an aluminum foil that is wound in one or more turns around the flux concentrator 135. In addition to that, the induction module 130 comprises a second dielectric wrapper 185 made of a Kapton tape that is arranged around the flux concentrator 135 and the shielding wrapper 183 for protecting the flux concentrator 135 and the shielding wrapper 183. Further in contrast to the embodiment shown in FIG. 1 and FIG. 2, the susceptor element 160 according to the embodiment shown in FIG. 10 is a susceptor sleeve 161 which is arranged at the inner surface of the inner support sleeve 132 such as to surround the article when the article is received in the receiving cavity. Apart from that, the embodiment shown in FIG. 10 is very similar to the embodiment shown in FIG. 1 and FIG. 2. Therefore, identical or similar features are denoted with the same reference signs, however, incremented by 100.

[0233] FIG. 11 shows a schematic cross-sectional illustration of yet another embodiment of an aerosol-generating system 1 according of the present invention. The system is identical to the system shown in FIG. 1, apart from the susceptor. Therefore, identical reference numbers are used for identical features. In contrast to the embodiment shown in FIG. 1, the susceptor 68 of the system according to FIG. 11 is not part of the aerosol-generating device 10 but part of the aerosol-generating article 90. In the present embodiment, the susceptor 68 comprises a susceptor strip 69 made of metal, for example, stainless steel, which is located within the aerosol-forming substrate of the substrate element 91. In particular, the susceptor 68 is arranged within the article 90 such that upon insertion of the article 90 into the cavity 20 of the device 10, the susceptor strip 69 is arranged the cavity 20, in particular within the induction coil 31 such that in use the susceptor strip 69 experience the magnetic field of the induction coil 31.

[0234] FIGS. 12-15 exemplarily illustrate some steps of the method according to the present invention that is used for manufacturing a multi-layer flux concentrator foil of an aerosol-generating device according to the present invention. As described further above, the method comprises—inter alia—the step of cracking the one or more magnetic layers of the multi-layer flux concentrator foil into a plurality of fragments by applying an external force to the flux concentrator foil transvers to the foil plane. This may be accomplished by passing the flux concentrator foil through at least one pair of counter-rotating rollers 710, 720 which are pressed against each other such that the foil passing therethrough is squeezed between the two rollers 710, 720. As shown in FIG. 12 and FIG. 13, at least one of the rollers 710 comprises a plurality of protrusions 711 on its outer surface each of which locally applies a force to the flux concentrator foil transvers to the foil plane. In FIG. 12, each one of the upper roller 710 and the lower roller 720 comprises a plurality of protrusions 711, 721 in order to enhance the cracking effect. Preferably, the plurality of protrusions 711, 721 on both rollers 710, 720 may be formed as complementary protrusions. For example, in operation, the protrusions 711 of the upper roller 710 may fit in between the protrusions 721 of the lower roller 720. In contrast, as shown in FIG. 13, it is also possible that only one of the rollers 710 comprises a plurality of protrusions 711, whereas the respective other roller 720 comprises a smooth outer surface acting as a counter surface for the protrusions 711. It is to be noted that for reasons of simplicity FIG. 12 and FIG. 13 only show four rows of prosecutions 711, 721 on the respective rollers 710, 720. However, the rollers preferably have more than four rows of prosecutions equally distributed around the circumference of the respective roller.

[0235] The method further comprises the step of pulling the flux concentrator foil 35 under a tensile force parallel to the foil plane over at least one edge 730. This is shown in FIG. 14, in which arrow 731 indicates the tensile force. This step causes the fragments to be cracked in even smaller fragments and—most importantly—to be pulled apart such as to be further separated from each other. Advantageously, this results in an enhanced reduction of the AC resistance of the magnetic layer and, thus, in an enhanced reduction of the eddy current losses in the magnetic layer of the flux concentrator foil. Preferably, the least one edge 730 comprises a rounding radius of at most 0.3 millimeter, in particular at most 0.2 millimeter, preferably, at most 0.15 millimeter. Pulling the foil 35 over the edge 730 may occur under an angle 732 in a range between 60 degrees and 120 degrees, for example 80 degrees as shown in FIG. 14. The tensile force 731 used for pulling the foil 35 over the edge 730 may be in a range between 20 N and 60 N, in particular between 25 N and 40 N, for example 30 N.

[0236] In addition, the method may comprise pulling the flux concentrator foil under a tensile force 741 parallel to the foil plane over a sequence of rollers 740 in order to bend the flux concentrator foil 35 as shown in FIG. 15. Advantageously, this step may cause the fragments to be cracked in even smaller fragments, thus resulting in an enhanced reduction of the AC resistance of the magnetic layer. This step may be performed prior to pulling the flux concentrator foil over the at least one edge.

[0237] FIG. 16 shows (not to scale) another example of a multi-layer flux concentrator foil according to the present invention, which comprises a plurality of magnetic layers. From bottom to top, the multi-layer flux concentrator foil according to FIG. 16 comprises the following layers: [0238] an adhesive (non-PET) first support layer 340, [0239] a first magnetic layer 350 comprising or made of the soft magnetic alloy, [0240] an adhesive (non-PET) intermediate support layer 360, [0241] a second magnetic layer comprising or made of the soft magnetic alloy 370, and [0242] an adhesive (PET-based) second support layer 380.

[0243] As has been described in more detail above, the multi-layer flux concentrator foil may be sealed to prevent fragments from laterally escaping from the foil. For this, a sealing adhesive tape 330, 390 may be arranged on one or each side of the (unsealed) flux concentrator foil according to FIG. 16. Such a sealed multi-layer flux concentrator foil is shown in FIG. 17. As can be seen there, the adhesive sealing tape 330, 390 has a width extension in a direction transverse to opposite edges of the unsealed flux concentrator foil which is larger than a width extension of the unsealed flux concentrator foil in the same direction, that is, in a direction transverse to opposite edges of the unsealed flux concentrator foil. As a result, the sealing adhesive tape 330, 390 on each side of the unsealed flux concentrator foil comprises laterally protruding wings 335, 395, which may get into adhesive contact with each other such as to seal the edges of the (unsealed) flux concentrator. Accordingly, the specific example of the sealed multi-layer flux concentrator foil according to FIG. 17 comprises the following layers (from bottom to top): [0244] a first PET-based adhesive film 331 (first adhesive sealing tape 330), [0245] an adhesive (non-PET) first support layer 340, [0246] a first magnetic layer 350 comprising or made of the soft magnetic alloy, [0247] an adhesive (non-PET) intermediate support layer 360, [0248] a second magnetic layer comprising or made of the soft magnetic alloy 370, [0249] an adhesive (PET-based) second support layer 380, and [0250] a second PET-based adhesive film 391 (second adhesive sealing tape 390).

[0251] The first and second PET-based adhesive films 331, 391 may have a thickness of 2-5 micrometer, in particular 3 micrometer. The adhesive (non-PET-based) first and second support layer 340, 360 and the adhesive (PET-based) third support 380 layer may have a thickness in a range between 2 micrometer and 10 micrometer, in particular in range between 2 micrometer and 5 micrometer, for example, 3 micrometer. The first and second magnetic layers 350, 370 may have a thickness in range between 15 micrometer and 25 micrometer, in particular in range between 18 micrometer and 23 micrometer, for example, 21 micrometer.

[0252] Instead of the first and second PET-based adhesive films 331, 991, the first and second sealing tape 330, 390 may also comprise a first and second three-layer adhesive sealing laminate, each of comprises a (PEN- or PI-based) film sandwiched between a first adhesive layer and a second adhesive layer (not shown in FIG. 17).

[0253] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A±5 percent A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.