INDUCTIVE HEATING ARRANGEMENT WITH SEGMENTED INDUCTIVE HEATING ELEMENT

Abstract

An inductive heating element for an aerosol-generating system is provided, the inductive heating element including: a first susceptor, the first susceptor being a tubular susceptor defining an inner cavity configured to receive an aerosol-forming substrate; a second susceptor, the second susceptor being a tubular susceptor defining an inner cavity configured to receive aerosol-forming substrate; and a separation between the first susceptor and the second susceptor, the separation thermally insulating the first susceptor from the second susceptor. An inductive heating arrangement, an aerosol-generating device, and an aerosol-generating system are also provided.

Claims

1.-16. (canceled)

17. An inductive heating element for an aerosol-generating system, the inductive heating element comprising: a first susceptor, the first susceptor being a tubular susceptor defining an inner cavity configured to receive an aerosol-forming substrate; a second susceptor, the second susceptor being a tubular susceptor defining an inner cavity configured to receive aerosol-forming substrate; and a separation between the first susceptor and the second susceptor, the separation thermally insulating the first susceptor from the second susceptor.

18. The inductive heating element according to claim 17, further comprising an intermediate element disposed between the first susceptor and the second susceptor, the intermediate element comprising a thermally insulative material configured to thermally insulate the first susceptor from the second susceptor.

19. The inductive heating element according to claim 18, wherein the intermediate element comprises an electrically insulative material configured to electrically insulate the first susceptor from the second susceptor.

20. The inductive heating element according to claim 18, wherein the intermediate element is a tubular intermediate element defining an inner cavity.

21. The inductive heating element according to claim 18, wherein the intermediate element is secured to an end of the first susceptor.

22. The inductive heating element according to claim 21, wherein the intermediate element is secured to an end of the second susceptor

23. The inductive heating element according to claim 17, wherein the first susceptor comprises a tubular support body formed from a thermally insulative material and a susceptor layer on an inner surface of the tubular support body, and wherein the second susceptor comprises a tubular support body formed from a thermally insulative material and a susceptor layer on an inner surface of the tubular support body.

24. An inductive heating arrangement, comprising: an inductive heating element according to claim 17; a first inductor coil; and a second inductor coil, wherein the first inductor coil is arranged relative to the inductive heating element such that a varying electric current supplied to the first inductor coil generates a varying magnetic field that heats the first susceptor of the inductive heating element, and wherein the second inductor coil is arranged relative to the inductive heating element such that a varying electric current supplied to the second inductor coil generates a varying magnetic field that heats the second susceptor of the inductive heating element.

25. The inductive heating arrangement according to claim 24, wherein the first inductor coil is a tubular coil having an inner cavity, the first susceptor being arranged within the inner cavity of the first inductor coil, and wherein the second inductor coil is a tubular coil having an inner cavity, the second susceptor being arranged within the inner cavity of the second inductor coil.

26. The inductive heating arrangement according to claim 25, further comprising a flux concentrator disposed around the first inductor coil and the second inductor coil, the flux concentrator being configured to distort the varying magnetic field generated by the first inductor coil towards the first susceptor and to distort the varying magnetic field generated by the second inductor coil towards the second susceptor.

27. The inductive heating arrangement according to claim 26, wherein a portion of the flux concentrator extends into the intermediate element between the first susceptor and the second susceptor.

28. The inductive heating arrangement according to claim 25, further comprising: a first flux concentrator disposed around the first inductor coil, the first flux concentrator being configured to distort the varying magnetic field generated by the first inductor coil towards the first susceptor; and a second flux concentrator disposed around the second inductor coil, the second flux concentrator being configured to distort the varying magnetic field generated by the second inductor coil towards the second susceptor.

29. The inductive heating arrangement according to claim 28, wherein at least one of: a portion of the first flux concentrator extends into the intermediate element between the first susceptor and the second susceptor, and a portion of the second flux concentrator extends into the intermediate element between the first susceptor and the second susceptor.

30. An aerosol-generating device, comprising an inductive heating arrangement according to claim 24.

31. An aerosol-generating device, comprising: a device housing defining a device cavity configured to receive an aerosol-forming substrate; an inductive heating arrangement including: an inductive heating element comprising: a first susceptor disposed around a first portion of the device cavity, a second susceptor disposed around a second portion of the device cavity, and a separation between the first susceptor and the second susceptor, the separations thermally insulating the first susceptor from the second susceptor; a first inductor coil disposed around at least a portion of the first susceptor and the first portion of the device cavity; and a second inductor coil disposed around at least a portion of the second susceptor and the second portion of the device cavity; and a power supply connected to the inductive heating arrangement and configured to provide a varying electric current to the first inductor coil and the second inductor coil, wherein: when the varying electric current is supplied to the first inductor coil, the first inductor coil generates a varying magnetic field that heats the first susceptor, and when the varying electric current is supplied to the second inductor coil, the second inductor coil generates a varying magnetic field that heats the second susceptor.

32. An aerosol-generating system, comprising: an aerosol-generating article comprising: a first aerosol-forming substrate, and a second aerosol-forming substrate; and an aerosol-generating device as claimed in claim 31, wherein when the aerosol-generating article is received in the device cavity, at least a portion of the first aerosol-forming substrate is received in the first portion of the device cavity and at least a portion of the second aerosol-forming substrate is received in the second portion of the device cavity.

Description

[0132] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0133] FIG. 1 shows a schematic illustration of an inductive heating element according to an embodiment of this disclosure arranged between a pair of inductor coils;

[0134] FIG. 2 shows a schematic illustration of an inductive heating element according to an embodiment of this disclosure arranged between a pair of inductor coils;

[0135] FIG. 3 shows an exploded perspective view of an inductive heating element according to an embodiment of this disclosure;

[0136] FIG. 4 shows a perspective view of the inductive heating element of FIG. 3;

[0137] FIG. 5 shows a cross-sectional view of an aerosol-generating system according to an embodiment of the present invention, the aerosol-generating system comprising an aerosol-generating article, and an aerosol-generating device having an inductive heating arrangement;

[0138] FIG. 6 a cross-sectional view of the proximal end of the aerosol-generating device of FIG. 5;

[0139] FIG. 7 shows a cross-sectional view of the aerosol-generating system of FIG. 5, with the aerosol-generating article received in the aerosol-generating device; and

[0140] FIG. 8 shows a cross-sectional view of a modular inductive heating arrangement according to an embodiment of the present disclosure, the inductive heating arrangement comprising two stacked inductive heating units, each inductive heating unit comprising a susceptor having thermally insulative and electrically insulative intermediate elements arranged at both ends, an inductor coil, a flux concentrator and a housing.

[0141] FIG. 1 shows a schematic illustration of an inductive heating element 10 according to an embodiment of this disclosure. The inductive heating element 10 is an elongate, tubular element, having a circular transverse cross-section. The inductive heating element 10 comprises a first susceptor 12, a second susceptor 14, and a separation 15 between the first susceptor 12 and the second susceptor 14. The first susceptor 12 and the second susceptor 14 are each elongate, tubular elements having a circular transverse cross-section. The first susceptor 12 and the second susceptor 14 are coaxially aligned, end-to-end, along a longitudinal axis A-A.

[0142] The inductive heating element 10 comprises a cylindrical cavity 20, open at both ends, defined by an inner surfaces of the first susceptor 12 and the second susceptor 14. The cavity 20 is configured to receive a portion of a cylindrical aerosol-generating article (not shown), comprising an aerosol-forming substrate, such that an outer surface of the aerosol-generating article may be heated by the first susceptor and the second susceptor, thereby heating the aerosol-forming substrate.

[0143] The cavity 20 comprises three portions, a first portion 22 at a first end, defined by an inner surface of the tubular first susceptor 12, a second portion 24 at a second end, opposite the first end, defined by an inner surface of the tubular second susceptor 14, and an intermediate portion 26, bounded by the separation 15 between the first susceptor 12 and the second susceptor 14. The first susceptor 12 is arranged to heat a first portion of an aerosol-generating article received in the first portion 22 of the cavity 20, and the second susceptor 14 is arranged to heat a second portion of an aerosol-generating article received in the second portion 24 of the cavity 20.

[0144] A first inductor coil 32 is disposed around the first susceptor 12, and extends substantially the length of the first susceptor 12. As such, the first susceptor 12 is circumscribed by the first inductor coil 32 substantially along its length. When a varying electric current is supplied to the first inductor coil 32, the first inductor coil 32 generates a varying magnetic field that is concentrated in the first portion 22 of the cavity 20. Such a varying magnetic field generated by the first inductor coil 32 induces eddy currents in the first susceptor 12, causing the first susceptor 12 to be heated.

[0145] A second inductor coil 34 is disposed around the second susceptor 14, and extends substantially the length of the second susceptor 14. As such, the second susceptor 14 is circumscribed by the second inductor coil 34 substantially along its length. When a varying electric current is supplied to the second inductor coil 34, the second inductor coil 34 generates a varying magnetic field that is concentrated in the second portion 24 of the cavity 20. Such a varying magnetic field generated by the second inductor coil 34 induces eddy currents in the second susceptor 14, causing the second susceptor 14 to be heated.

[0146] The separation 15 between the first susceptor 12 and the second susceptor 14 provides a space between the first susceptor 12 and the second susceptor 14 that is not heated by induction when exposed to a varying magnetic field generated by either the first inductor coil 32 or the second inductor coil 34. Furthermore, the separation 15 thermally insulates the second susceptor 14 from the first susceptor 12, such that there is a reduced rate of heat transfer between the first susceptor 12 and the second susceptor 14, compared to an inductive heating element in which the first susceptor and the second susceptor are arranged adjacent each other, in direct thermal contact. As a result, providing the separation 15 between the first susceptor 12 and the second susceptor 14 enables selective heating of the first portion 22 of the cavity 20 by the first susceptor 12 with minimal heating of the second portion 24 of the cavity 20, and enables selective heating of the second portion 24 of the cavity 20 by the second susceptor 14 with minimal heating of the first portion 22 of the cavity 20.

[0147] The first susceptor 12 and the second susceptor 14 may be heated simultaneously by simultaneously supplying a varying electric current to the first inductor coil 32 and the second inductor coil 34. Alternatively, the first susceptor 12 and the second susceptor 14 may be heated independently or alternately by supplying a varying electric current to the first inductor coil 32 without supplying a current to the second inductor coil 34, and by subsequently supplying a varying electric current to the second inductor coil 34 without supplying a current to the first inductor coil 32. It is also envisaged that a varying electric current may be supplied to the first inductor coil 32 and the second inductor coil 34 in a sequence.

[0148] FIG. 2 shows a schematic illustration of an inductive heating element according to another embodiment of this disclosure. The inductive heating element shown in FIG. 2 is substantially identical to the inductive heating element shown in FIG. 1, and like reference numerals are used to describe like features.

[0149] The inductive heating element 10 of FIG. 2 is an elongate, tubular element, having a circular transverse cross-section. The inductive heating element 10 comprises a first susceptor 12, a second susceptor 14. The difference between the inductive heating element 10 of FIG. 1 and the inductive heating element 10 of FIG. 2 is that the inductive heating element 10 of FIG. 2 comprises an intermediate element 16 disposed between the first susceptor 12 and the second susceptor 14. In the embodiment of FIG. 2, there is still a separation between the first susceptor 12 and the second susceptor 14, however, the separation is filled by the intermediate element 16. In this embodiment, the intermediate element 16 is secured to an end of the first susceptor 12 and is also secured to an end of the second susceptor 14. Securing the intermediate element 16 to an end of the first susceptor 12, and securing the intermediate element 16 to an end of the second susceptor 14, indirectly connects the first susceptor 12 to the second susceptor 14. Advantageously, indirectly securing the first susceptor 12 to the second susceptor 14 enables the inductive heating element to form a unitary structure.

[0150] The intermediate element 16 comprises a thermally insulative material. The thermally insulative material is also electrically insulative. In this embodiment, the intermediate element 16 is formed from a polymeric material, such as PEEK. As such, the intermediate element 16 between the first susceptor 12 and the second susceptor 14 provides a space between the first susceptor 12 and the second susceptor 14 that is not heated by induction when exposed to a varying magnetic field generated by either the first inductor coil 32 or the second inductor coil 34. Furthermore, the intermediate element 16 thermally insulates the second susceptor 14 from the first susceptor 12, such that there is a reduced rate of heat transfer between the first susceptor 12 and the second susceptor 14, compared to an inductive heating element in which the first susceptor and the second susceptor are arranged adjacent each other, in direct thermal contact. The intermediate element 16 may also further reduce the rate of heat transfer between the first susceptor 12 and the second susceptor 14 compared to the separation 15 of the inductive heating element 10 of FIG. 1. As a result, providing the intermediate element 16 between the first susceptor 12 and the second susceptor 14 enables selective heating of the first portion 22 of the cavity 20 by the first susceptor 12 with minimal heating of the second portion 24 of the cavity 20, and enables selective heating of the second portion 24 of the cavity 20 by the second susceptor 14 with minimal heating of the first portion 22 of the cavity 20.

[0151] FIGS. 3 to 7 show schematic illustrations of an aerosol-generating system according to an embodiment of the present disclosure. The aerosol-generating system comprises an aerosol-generating device 100 and an aerosol-generating article 200. The aerosol-generating device 100 comprises an inductive heating arrangement 110 according to the present disclosure. The inductive heating arrangement 110 comprises an inductive heating element 120 according to the present disclosure.

[0152] FIGS. 3 and 4 show schematic illustrations of the inductive heating element 120. The inductive heating element 120 comprises: a first susceptor 122, a second susceptor 124, a third susceptor 126, a first intermediate element 128 and a second intermediate element 130. The first intermediate element 128 is disposed between the first susceptor 122 and the second susceptor 124. The second intermediate element 130 is disposed between the second susceptor 124 and the third susceptor 126.

[0153] In this embodiment, each of the first susceptor 122, the second susceptor 124 and the third susceptor 126 are identical. Each susceptor 122, 124, 126 is an elongate tubular susceptor, defining an inner cavity. Each susceptor, and its corresponding inner cavity, are substantially cylindrical, having a circular transverse cross-section that is constant along the length of the susceptor. The inner cavity of the first susceptor 122 defines a first region 134. The inner cavity of the second susceptor 124 defines a second region 136. The inner cavity of the third susceptor defines a third region 138.

[0154] Similarly, the first intermediate element 128 and the second intermediate element 130 are identical. The intermediate elements 128, 130 are tubular, defining an inner cavity. Each intermediate element 128, 130 is substantially cylindrical, having a circular transverse cross-section that is constant along the length of the intermediate element. The outer diameter of the intermediate elements 128, 130 is identical to the outer diameter of the susceptors 122, 124, 126, such that the outer surface of the intermediate elements 128, 130 may be aligned flush with the outer surface of the susceptors 122, 124, 126. The inner diameter of the intermediate elements 128, 130 is also identical to the inner diameter of the susceptors 122, 124, 126, such that the inner surface of the intermediate elements 128, 138 may be aligned flush with the inner surface of the susceptors 122, 124, 126.

[0155] The first susceptor 122, the first intermediate element 128, the second susceptor 124, the second intermediate element 130 and the third susceptor 126 are arranged end-to-end, and coaxially aligned on an axis B-B. In this arrangement, the susceptors 122, 124, 126 and the intermediate elements 128, 130 form a tubular, elongate, cylindrical structure. This structure forms the inductive heating element 120 in accordance with an embodiment of the present disclosure.

[0156] The elongate tubular inductive heating element 120 comprises an inner cavity 140. The inductive heating element cavity 140 is defined by the inner cavities of the susceptors 122, 124, 126 and the inner cavities of the intermediate elements 128, 130. The inductive heating element cavity 140 is configured to receive an aerosol-generating segment of the aerosol-generating article 200, as described in more detail below.

[0157] The intermediate elements 128, 130 are formed from an electrically insulative and thermally insulative material. As such, the susceptors 122, 124, 126 are substantially electrically and thermally insulated from each other. The material of the intermediate elements 128, 130 is also substantially impermeable to gas. In this embodiment, the tubular inductive heating element 120 is substantially impermeable to gas from an outer surface to an inner surface defining the inductive heating element cavity 140.

[0158] FIGS. 5, 6 and 7 show schematic cross-sections of the aerosol-generating device 100 and the aerosol-generating article 200.

[0159] The aerosol-generating device 100 comprises a substantially cylindrical device housing 102, with a shape and size similar to a conventional cigar. The device housing 102 defines a device cavity 104 at a proximal end. The device cavity 104 is substantially cylindrical, open at a proximal end, and substantially closed at a distal end, opposite the proximal end. The device cavity 104 is configured to receive the aerosol-generating segment 210 of the aerosol-generating article 200. Accordingly, the length and diameter of the device cavity 104 are substantially similar to the length and diameter of the aerosol-generating segment 210 of the aerosol-generating article 200.

[0160] The aerosol-generating device 100 further comprises a power supply 106, in the form of a rechargeable nickel—cadmium battery, a controller 108 in the form of a printed circuit board including a microprocessor, an electrical connector 109, and the inductive heating arrangement 110. The power supply 106, controller 108 and inductive heating arrangement 110 are all housed within the device housing 102. The inductive heating arrangement 110 of the aerosol-generating device 100 is arranged at the proximal end of the device 100, and is generally disposed around the device cavity 104. The electrical connector 109 is arranged at a distal end of the device housing 109, opposite the device cavity 104.

[0161] The controller 108 is configured to control the supply of power from the power supply 106 to the inductive heating arrangement 110. The controller 108 further comprises a DC/AC inverter, including a Class-D power amplifier, and is configured to supply a varying current to the inductive heating arrangement 110. The controller 108 is also configured to control recharging of the power supply 106 from the electrical connector 109. In addition, the controller 108 comprises a puff sensor (not shown) configured to sense when a user is drawing on an aerosol-generating article received in the device cavity 104.

[0162] The inductive heating arrangement 110 comprises three inductive heating units, including a first inductive heating unit 112, a second inductive heating unit 114 and a third inductive heating unit 116. The first inductive heating unit 112, second inductive heating unit 114 and third inductive heating unit 116 are substantially identical.

[0163] The first inductive heating unit 112 comprises a cylindrical, tubular first inductor coil 150, a cylindrical, tubular first flux concentrator 152 disposed about the first inductor coil 150 and a cylindrical, tubular first inductor unit housing 154 disposed about the first flux concentrator 152.

[0164] The second inductive heating unit 114 comprises a cylindrical, tubular second inductor coil 160, a cylindrical, tubular second flux concentrator 162 disposed about the second inductor coil 160 and a cylindrical, tubular second inductor unit housing 164 disposed about the second flux concentrator 162.

[0165] The third inductive heating unit 116 comprises a cylindrical, tubular third inductor coil 170, a cylindrical, tubular third flux concentrator 172 disposed about the third inductor coil 170 and a cylindrical, tubular third inductor unit housing 174 disposed about the third flux concentrator 172.

[0166] Accordingly, each inductive heating unit 112, 114, 116 forms a substantially tubular unit with a circular transverse cross-section. In each inductive heating unit 112, 114, 116, the flux concentrator extends over the proximal and distal ends of the inductor coil, such that the inductor coil is arranged within an annular cavity of the flux concentrator. Similarly, each inductive heating unit housing extends over the proximal and distal ends of the flux concentrator, such that the flux concentrator and inductor coil are arranged within an annular cavity of the inductive heating unit housing. This arrangement enables the flux concentrator to concentrate the magnetic field generated by the inductor coil in the inner cavity of the inductor coil. This arrangement also enables the inductor unit housing to retain the flux concentrator and inductor coil within the inductor unit housing.

[0167] The inductive heating arrangement 110 further comprises the inductive heating element 120. The inductive heating element 120 is disposed about the inner surface of the device cavity 104. In this embodiment, the device housing 102 defines an inner surface of the device cavity 104. However, it is envisaged that in some embodiments the inner surface of the device cavity is defined by the inner surface of the inductive heating element 120.

[0168] The inductive heating units 112, 114, 116 are disposed about the inductive heating element 120, such that the inductive heating element 120 and the inductive heating units 112, 114, 116 are concentrically arranged about the device cavity 104. The first inductive heating unit 112 is disposed about the first susceptor 122, at a distal end of the device cavity 104. The second inductive heating unit 114 is disposed about the second susceptor 124, at a central portion of the device cavity 104. The third inductive heating unit 116 is disposed about the third susceptor 126, at a proximal end of the device cavity 104. It is envisaged that in some embodiments the flux concentrators may also extend into the intermediate elements of the inductive heating element, in order to further distort the magnetic fields generated by the inductor coils towards the susceptors.

[0169] The first inductor coil 150 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying electric current to the first inductor coil 150. When a varying electric current is supplied to the first inductor coil 150, the first inductor coil 150 generates a varying magnetic field, which heats the first susceptor 122 by induction.

[0170] The second inductor coil 160 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying electric current to the second inductor coil 160. When a varying electric current is supplied to the second inductor coil 160, the second inductor coil 160 generates a varying magnetic field, which heats the second susceptor 124 by induction.

[0171] The first inductor coil 170 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying electric current to the third inductor coil 170. When a varying electric current is supplied to the third inductor coil 170, the third inductor coil 170 generates a varying magnetic field, which heats the third susceptor 126 by induction.

[0172] The device housing 102 also defines an air inlet 180 in close proximity to the distal end of the device cavity 106. The air inlet 180 is configured to enable ambient air to be drawn into the device housing 102. An airflow pathway 181 is defined through the device, between the air inlet 180 and an air outlet in the distal end of the device cavity 104, to enable air to be drawn from the air inlet 180 into the device cavity 104.

[0173] The aerosol-generating article 200 is generally in the form of a cylindrical rod, having a diameter similar to the inner diameter of the device cavity 104. The aerosol-generating article 200 comprises a cylindrical cellulose acetate filter plug 204 and a cylindrical aerosol-generating segment 210 wrapped together by an outer wrapper 220 of cigarette paper.

[0174] The filter plug 204 is arranged at a proximal end of the aerosol-generating article 200, and forms the mouthpiece of the aerosol-generating system on which a user draws to receive aerosol generated by the system.

[0175] The aerosol-generating segment 210 is arranged at a distal end of the aerosol-generating article 200, and has a length substantially equal to the length of the device cavity 104. The aerosol-generating segment 210 comprises a plurality of aerosol-forming substrates, including: a first aerosol-forming substrate 212 at a distal end of the aerosol-generating article 200, a second aerosol-forming substrate 214 adjacent the first aerosol-forming substrate 212, and a third aerosol-forming substrate 216 at a proximal end of the aerosol-generating segment 210, adjacent the second aerosol-forming substrate 216. It will be appreciated that in some embodiments two or more of the aerosol-forming substrates may be formed from the same materials. However, in this embodiment each of the aerosol-forming substrates 212, 214, 216 is different. The first aerosol-forming substrate 212 comprises a gathered and crimped sheet of homogenised tobacco material, without additional flavourings. The second aerosol-forming substrate 214 comprises a gathered and crimped sheet of homogenised tobacco material including a flavouring in the form of menthol. The third aerosol-forming substrate comprises a flavouring in the form of menthol, and does not comprise tobacco material or any other source of nicotine. Each of the aerosol-forming substrates 212, 214, 216 also comprises further components, such as one or more aerosol formers and water, such that heating the aerosol-forming substrate generates an aerosol with desirable organoleptic properties.

[0176] The proximal end of the first aerosol-forming substrate 212 is exposed, as it is not covered by the outer wrapper 220. In this embodiment, air is able to be drawn into the aerosol-generating segment 210 via the proximal end of the first aerosol-forming substrate 212, at the proximal end of the article 200.

[0177] In this embodiment, the first aerosol-forming substrate 212, the second aerosol-forming substrate 214 and the third aerosol-forming substrate 216 are arranged end-to-end. However, it is envisaged that in other embodiments, a separation may be provided between the first aerosol-forming substrate and the second aerosol-forming substrate, and a separation may be provided between the second aerosol-forming substrate and the third aerosol-forming substrate.

[0178] As shown in FIG. 7, when the aerosol-generating segment 210 of the aerosol-generating article 200 is received in the device cavity 104, the length of the first aerosol-forming substrate 212 is such that the first aerosol-forming substrate 212 extends from the distal end of the device cavity 104, through the first region 134 of the first susceptor 122, and to the first intermediate member 128. The length of the second aerosol-forming substrate 214 is such that the second aerosol-forming substrate 214 extends from the first intermediate member 128, through the second region 136 of the second susceptor 124, and to the second intermediate member 130. The length of the third aerosol-forming substrate 216 is such that the third aerosol-forming substrate 216 extends from the second intermediate member 130 to the proximal end of the device cavity 104.

[0179] In use, when an aerosol-generating article 200 is received in the device cavity 104, a user may draw on the proximal end of the aerosol-generating article 200 to inhale aerosol generated by the aerosol-generating system. When a user draws on the proximal end of the aerosol-generating article 200, air is drawn into the device housing 102 at the air inlet 180, and is drawn along the airflow pathway 181, into the device cavity 104. The air is drawn into the aerosol-generating article 200 at the proximal end of the first aerosol-forming substrate 212 through the outlet in the distal end of the device cavity 104.

[0180] In this embodiment, the controller 108 of the aerosol-generating device 100 is configured to supply power to the inductor coils of the inductive heating arrangement 110 in a predetermined sequence. The predetermined sequence comprises supplying a varying electric current to the first inductor coil 150 during a first draw from the user, subsequently supplying a varying electric current to the second inductor coil 160 during a second draw from the user, after the first draw has finished, and subsequently supplying a varying electric current to the third inductor coil 170 during a third draw from the user, after the second draw has finished. On the fourth draw, the sequence starts again at the first inductor coil 150. This sequence results in heating of the first aerosol-forming substrate 212 on a first puff, heating of the second aerosol-forming substrate 214 on a second puff, and heating of the third aerosol-forming substrate 216 on a third puff. Since the aerosol forming substrates 212, 214, 216 of the article 100 are all different, this sequence results in a different experience for a user on each puff on the aerosol-generating system.

[0181] It will be appreciated that the controller 108 may be configured to supply power to the inductor coils in a different sequence, or simultaneously, depending on the desired delivery of aerosol to the user. In some embodiments, the aerosol-generating device may be controllable by the user to change the sequence.

[0182] FIG. 8 shows an inductive heating arrangement according to another embodiment of the present invention. The inductive heating arrangement 300 comprises two modular inductive heating units, a first inductive heating unit 310 and a second inductive heating unit 360. The modular inductive heating units 310, 360 are identical, independent units that are individually removable and replaceable in the inductive heating arrangement 300. Providing such modular inductive heating units enables an inductive heating arrangement to be relatively inexpensive and straightforward to manufacture. This is because it may be easier to standardise manufacturing of separate, modular inductive heating units, rather than an entire inductive heating arrangement. Providing such modular inductive heating units may also enable an inductive heating assembly to be easily customisable.

[0183] The first inductive heating unit 310 generally comprises a tubular first susceptor 312, a tubular first inductor coil 314, a tubular first flux concentrator 316 and a tubular first inductive heating unit housing 318.

[0184] The first susceptor 312 comprises a tubular support body 320, formed from an electrically insulative and thermally insulative material, such as alumina, and a susceptor layer 322 on an inner surface of the tubular support body 320. Intermediate elements 324 are provided at each end of the tubular support body 320, overlapping the ends of the susceptor layer 322. The intermediate elements 324 are also formed from an electrically insulative and thermally insulative material, such as alumina.

[0185] The first inductor coil 314 is disposed around the outer surface of the first susceptor 312, and extends substantially the length of the first susceptor 312. Each end 326 of the first inductor coil 312 extends through the first flux concentrator 316 and housing 318, to an outer surface of the first inductive heating unit 310, such that the first inductor coil 314 may be connected to a power supply and supplied with a varying current.

[0186] The first flux concentrator 316 is disposed around the outer surface of the tubular first inductor coil 314, and extends over the ends of the first inductor coil 314 and the first susceptor 312, but not beyond the inner surface of the first susceptor 312. The intermediate elements 324 are disposed between the first susceptor 312 and the first flux concentrator 316, and electrically insulate the susceptor layer of the first susceptor 312 from the first flux concentrator 316.

[0187] The first inductive heating unit housing 318 extends around the outer surface of the first flux concentrator 316, over the ends of the flux concentrator 316, and over the inner surface of the first flux concentrator 316. The first inductive heating unit housing 318 also extends over the intermediate elements 324 of the first susceptor 312, such that the first susceptor 312, first inductor coil 314 and first flux concentrator 316 are held together. In this way, the first susceptor 312, first inductor coil 314, first flux concentrator 316 and first inductive heating unit housing 318 form a tubular unit, having an inner cavity that is able to receive aerosol-forming substrate. The first inductive heating unit housing 318 is formed from an electrically insulative and thermally insulative material. In this embodiment, the first inductive unit housing 318 is formed from a polymer, such as PEEK, that is injection moulded over the first susceptor 312, first inductor coil 314 and first flux concentrator 316.

[0188] The second inductive heating unit 360 generally comprises a tubular second susceptor 362, a tubular second inductor coil 364, a tubular second flux concentrator 366 and a tubular second inductive heating unit housing 368.

[0189] The second susceptor 362 comprises a tubular support body 370, formed from an electrically insulative and thermally insulative material, such as PEEK, and a susceptor layer 372 on an inner surface of the tubular support body 370. Intermediate elements 374 are provided at each end of the tubular support body 370, overlapping the ends of the susceptor layer 372. The intermediate elements 374 are also formed from an electrically insulative and thermally insulative material, which in this embodiment is a ceramic material, such as zirconium dioxide (ZrO2).

[0190] The second inductor coil 364 is disposed around the outer surface of the second susceptor 362, and extends substantially the length of the second susceptor 362. Each end 376 of the second inductor coil 362 extends through the second flux concentrator 366 and housing 368, to an outer surface of the second inductive heating unit 360, such that the second inductor coil 364 may be connected to a power supply and supplied with a varying current.

[0191] The second flux concentrator 366 is disposed around the outer surface of the tubular second inductor coil 364, and extends over the ends of the second inductor coil 364 and the second susceptor 362, but not beyond the inner surface of the second susceptor 362. The intermediate elements 374 are disposed between the second susceptor 362 and the second flux concentrator 366, and electrically insulate the susceptor layer of the second susceptor 362 from the second flux concentrator 366.

[0192] The second inductive heating unit housing 368 extends around the outer surface of the second flux concentrator 366, over the ends of the flux concentrator 366, and over the inner surface of the second flux concentrator 366. The second inductive heating unit housing 368 also extends over the intermediate elements 374 of the second susceptor 362, such that the second susceptor 362, second inductor coil 364 and second flux concentrator 366 are held together. In this way, the second susceptor 362, second inductor coil 364, second flux concentrator 366 and second inductive heating unit housing 368 form a tubular unit, having an inner cavity that is able to receive aerosol-forming substrate. The second inductive heating unit housing 368 is formed from an electrically insulative and thermally insulative material. In this embodiment, the second inductive unit housing 368 is formed from a polymer, such as PEEK, that is injection moulded over the second susceptor 362, second inductor coil 364 and second flux concentrator 366.

[0193] The second inductive heating unit 360 is stacked on top of the first inductive heating unit 310 to form the inductive heating arrangement 300. The inductive heating arrangement 300 generally forms a tubular unit defining an inner cavity 380 for receiving aerosol-forming substrate.

[0194] When the second inductive heating unit 360 is stacked on top of the first inductive heating unit 310, there is a separation between the first susceptor 312 and the second susceptor 362. The separation comprises an intermediate element 324, 374 from each of the first and second inductive heating units 310, 360, and end portions of the flux concentrator 316, 366 and inductive heating unit housing 318, 368 from each of the first and second inductive heating units 310, 360. Such a separation provides effective thermal insulation and electrical insulation between the susceptor layer 322 of the first susceptor 312 and the susceptor layer 372 of the second susceptor 362.

[0195] It will be appreciated that the embodiments described above are specific examples only, and other embodiments are envisaged in accordance with this disclosure.