AEROSOL-GENERATING DEVICE FOR 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 configured to removably receive the substrate to be heated; an inductive heating arrangement including at least one induction coil configured to generate an alternating magnetic field within the cavity, the coil being arranged around at least a portion of the cavity; and a flux concentrator arranged around at least a portion of the induction coil and configured to distort the alternating magnetic field of the at least one inductive heating arrangement towards the cavity, the flux concentrator including or being made of a flux concentrator foil, and the flux concentrator foil including at least one of a permalloy or a nano-crystalline soft magnetic alloy. An aerosol-generating system including the aerosol-generating device and an aerosol-generating article is also provided.

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 an alternating 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 configured to distort the alternating magnetic field of the at least one inductive heating arrangement towards the cavity, wherein the flux concentrator comprises or is made of a flux concentrator foil, and wherein the flux concentrator foil comprises at least one of a permalloy or a nano-crystalline soft magnetic alloy.

17. The aerosol-generating device according to claim 16, wherein the flux concentrator foil has a thickness in a range between 0.02 mm and 0.25 mm.

18. The aerosol-generating device according to claim 16, wherein the flux concentrator foil has a thickness in a range between 0.1 mm and 0.15 mm.

19. The aerosol-generating device according to claim 16, wherein the flux concentrator foil is wound up, with ends overlapping each other or abutting against each other, so as to form a tubular flux concentrator or a flux concentrator sleeve.

20. The aerosol-generating device according to claim 19, wherein the flux concentrator foil is attached to an inner surface of the device housing in a force-fitting manner due a partial release of an elastic restoring force of the wound-up flux concentrator foil.

21. The aerosol-generating device according to claim 19, wherein the ends overlapping each other or abutting each other are attached to each other.

22. The aerosol-generating device according to claim 16, wherein the flux concentrator foil is a single-layer foil or a multi-layer foil.

23. The aerosol-generating device according to claim 16, wherein the flux concentrator foil further comprises or is made of a material or materials having a relative maximum magnetic permeability of at least 1,000 for frequencies up to 50 kHz and a temperature of 25 degrees Celsius.

24. The aerosol-generating device according to claim 16, wherein the flux concentrator foil further comprises, in particular is made of a material or materials having a relative maximum magnetic permeability of at least 10,000 for frequencies up to 50 kHz and a temperature of 25 degrees Celsius.

25. The aerosol-generating device according to claim 16, wherein the flux concentrator foil further comprises or is made of at least one ferromagnetic or ferrimagnetic material.

26. The aerosol-generating device according to claim 16, wherein the inductive heating arrangement comprises a plurality of induction coils, and wherein the flux concentrator is arranged around at least a portion of one of the induction coils of the plurality of induction coils.

27. The aerosol-generating device according to claim 16, wherein the inductive heating arrangement comprises a plurality of induction coils, and wherein the flux concentrator is arranged around at least a portion of each one of the induction coils of the plurality of induction coils.

28. The aerosol-generating device according to claim 16, further comprising a radial gap between the at least one induction coil and the flux concentrator having a radial extension in a range between 40 micrometers and 400 micrometers.

29. The aerosol-generating device according to claim 16, further comprising a radial gap between the at least one induction coil and the flux concentrator having a radial extension in a range between 100 micrometers and 240 micrometers.

30. The aerosol-generating device according to claim 16, further comprising at least one susceptor element arranged at least partially within the cavity.

31. The aerosol-generating device according to claim 30, wherein the at least one susceptor element is a tubular susceptor or a susceptor sleeve.

32. An aerosol-generating system, comprising: an aerosol-generating device according claim 16; and an aerosol-generating article received or receivable at least partially in a cavity of the aerosol-generating device, wherein the aerosol-generating article comprises an aerosol-forming substrate to be heated.

33. The aerosol-generating system according to claim 32, wherein the aerosol-generating article further comprises at least one susceptor positioned in thermal proximity to or thermal contact with the aerosol-forming substrate such that the at least one susceptor is inductively heatable by the inductive heating arrangement of the aerosol-generating device when the aerosol-generating article is received in the cavity of the aerosol-generating device.

Description

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

[0081] FIG. 1 shows a schematic longitudinal cross-section of an aerosol-generating system in accordance with a first embodiment the present invention;

[0082] FIG. 2 is a detail view of the induction module according to FIG. 1;

[0083] FIG. 3 is a detail view of an induction module according to a second embodiment the present invention;

[0084] FIG. 4 shows a schematic longitudinal cross-section of an aerosol-generating system in accordance with a third embodiment the present invention;

[0085] FIGS. 5-8 show three different arrangements of a flux concentrator foil according to the present invention; and

[0086] FIG. 9 schematically illustrates an exemplary embodiment of a multi-layer flux concentrator foil according to the present invention.

[0087] 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.

[0088] 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 have substantially 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.

[0089] 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.

[0090] 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.

[0091] 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 electromagnetic 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 38 and has a plurality of turns, or windings, extending along its length. The wire 38 may have any suitable cross-sectional shape, such as square, oval, or triangular. In this embodiment, the wire 38 has a circular cross-section. In other embodiments, the wire may have a flat cross-sectional shape.

[0092] The inductive heating arrangement further comprises a susceptor element 60 that is arranged within the receiving cavity 20 such as to experience the electromagnetic 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 such as to allow the susceptor blade to readily penetrate the aerosol-forming substrate 91 within the distal end portion of the article 90.

[0093] 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 an alternating electromagnetic field within 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. Preferably, the high-frequency electromagnetic 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).

[0094] 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.

[0095] 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, the tubular inner support sleeve 32 has an annular protrusions 34 extending around the circumference of the inner support sleeve 32. The protrusions 34 are located at either end of the induction coil 31 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.

[0096] 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 31. The flux concentrator 33 is configured to distort the alternating electromagnetic field generated by the induction coil 31 during use of the device 10 towards the cavity 20. According to the invention, the flux concentrator 33 is made of a flux concentrator foil 35. The flux concentrator foil 35 comprises a material having a high relative magnetic permeability of at least 100, in particular of at least 1000, preferably of at least 10000, even more preferably of at least 50000, most preferably of at least 80000 at frequencies up to 50 kHz and a temperature of 25 degrees Celsius. Due to this, the electromagnetic field produced by the induction coil 31 is attracted to and guided by the flux concentrator 33. Thus, the flux concentrator 33 acts as a magnetic shield. This may reduce undesired heating of or interference with external objects. The electromagnetic field lines within the inner volume defined by the induction module 30 are also distorted by flux concentrator 33 so that the density of the electromagnetic 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.

[0097] In the present embodiment, the flux concentrator foil 35 has a thickness of about 0.1 mm (millimeters). It is a mono-layer foil made of mu-metal. The foil 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.

[0098] As can be further seen in 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.

[0099] FIG. 3 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 139 between the induction coil 131 and the flux concentrator foil 135. In the present embodiment, the gap 139 is filled with a filler material 136, for example, a polyimide, such as poly(4,4′-oxydiphenylene-pyromellitimide), also known as Kapton®, or any other suitable dielectric materials. For example, the induction coil 131 may be wrapped by one or more layers of Kapton tape such as to fill the radial gap 139 between the induction coil 131 and the flux concentrator 133. The gap 139 or the filler material 136, respectively, may have a radial extension in a range between 40 micrometers and 240 micrometers, for example 80 micrometers. Advantageously, the gap 139 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.

[0100] In contrast to the embodiment shown in FIG. 1 and FIG. 2, the susceptor element 160 according to the embodiment shown in FIG. 3 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.

[0101] Apart from that, the embodiment shown in FIG. 3 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.

[0102] FIG. 4 shows a schematic cross-sectional illustration of an aerosol-generating system 1 according a third embodiment 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. 4 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.

[0103] In principle, the flux concentrator foils 35, 135 may be wound up in different ways around the induction coil 33, 133. According to a first embodiment, the flux concentrator foil 35 may be wound up with its free ends 37, 137 abutting against each other as shown in FIG. 5. That is, the longitudinal edges of the flux concentrator foils which extend along the length axis of C of the aerosol-generating device abut against each other.

[0104] According to a second embodiment, the flux concentrator foil 35, 135 may be wound up with free ends 37, 137 overlapping each other as shown in FIG. 6. That is, the longitudinal edges of the flux concentrator foils 35, 135 which extend along the length axis of C of the aerosol-generating device abut against each other.

[0105] In case the flux concentrator foil is wound up, in particular in a single winding, such as to form a tubular flux concentrator or a flux concentrator sleeve, the concentrator foil may be attached to an inner surface of the device housing in a force-fitting manner due a partial release of an elastic restoring force of the wound-up flux concentrator foil. That, the elastic restoring force presses the concentrator foil radially outwards against the inner surface of the device housing. With reference to FIGS. 1, 2, and 4, such a flux concentrator foil may be easily inserted through the opening of the cavity 20 at the proximal end of the aerosol-generating device 10 into the radial slit between the outer surface of the support sleeve 32 and the inner surface of the device housing.

[0106] According to a third embodiment as shown in FIG. 7, the flux concentrator foil 35, 135 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.

[0107] 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.

[0108] The two latter configurations shown in FIG. 7 and FIG. 8 may be advantageously used to generate a multi-layer flux concentrator (foil), wherein each winding corresponds to one layer.

[0109] Instead of using multiple windings of a flux concentrator foil for generating a multi-layer flux concentrator, the flux concentrator foil itself may be a multi-layer flux concentrator foil. FIG. 9 shows an exemplary embodiment of such a multi-layer flux concentrator foil 235 in a cross-sectional view. In this embodiment, the multi-layer flux concentrator foil 235 comprises a substrate layer film 250, such as an adhesive tape and a layer of a ferromagnetic material disposed upon the substrate layer. On top of the substrate layer film 250, the multi-layer flux concentrator foil 235 comprises a layer of a first ferromagnetic material 251. On top of the layer of the first ferromagnetic material 251, the multi-layer flux concentrator foil 235 comprises a multilayer stack 252 comprising a plurality of pairs of layers, each pair comprising a spacing layer 253 and a layer of a second ferromagnetic material 254 disposed upon the spacing layer 253. The layers of the first and second ferromagnetic material 251, 254 may comprise or may be made of a foil. Preferably, each foil comprises or is made of at least one of a permalloy, a Nanoperm® alloy, a Vitroperm® alloy, such as Vitroperm 800, or a Metglas® brazing foil. In principle, the first and the second ferromagnetic material may be the same or may be different from each other The spacing layers 253 may be dielectric layer or a non-electrically conductive material to suppress the eddy current effect. For example, the spacing layers 253 may be comprise or may be made of an acrylic polymer or a ferromagnetic material with relatively lower magnetic permeability.

[0110] In addition, the multi-layer flux concentrator foil 235 comprises a protective layer 255 on top of the multilayer stack 252. The protective layer may comprise or may be made of polymers or ceramics.

[0111] Both, the substrate layer film 250 and the protective layer 255, form the outermost or edge layers of the multi-layer flux concentrator foil 235.

[0112] The layers of ferromagnetic material 253 may each have a thickness of about 16 micrometers to 20 micrometers, for example 18 micrometers.

[0113] The total thickness of the multi-layer flux concentrator foil 235 may be in range between 0.1 millimeters and 0.2 millimeters, for example 0.15 millimeters.