AEROSOL-FORMING SUBSTRATE AND AEROSOL-DELIVERY SYSTEM

Abstract

There is described an aerosol-forming substrate for use in combination with an inductive heating device. The aerosol-forming substrate comprises a solid material which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate and at least a first susceptor material for heating the aerosol-forming substrate. The at least first susceptor material is arranged in thermal proximity of the solid material. The aerosol-forming substrate further comprises at least a second susceptor material which has a second Curie-temperature which is lower than a first Curie-temperature of the first susceptor material. The second Curie-temperature of the second susceptor material corresponds to a predefined maximum heating temperature of the first susceptor material. There is also described an aerosol-delivery system.

Claims

1-15. (canceled)

16. A method for heating an aerosol-forming substrate to a predefined maximum temperature, the method comprising: providing first and second susceptor materials each in thermal proximity to the aerosol forming substrate; inductively heating, by activating an inductive heating device, the first susceptor material such that the first susceptor material heats the aerosol-forming substrate to form an aerosol; detecting a first phase-change of the second susceptor material during the inductive heating, the first phase-change occurring at the predefined maximum temperature; and responsive to detecting the first phase-change of the second susceptor material, stopping the inductive heating by deactivating the inductive heating device.

17. The method of claim 16, further comprising, subsequent to stopping the inductive heating: allowing the second susceptor material to cool, a second phase-change of the second susceptor material occurring during the cooling; detecting the second phase-change of the second susceptor material during the cooling; and responsive to detecting the second phase-change of the second susceptor material, activating the inductive heating device.

18. The method of claim 17, wherein the second phase-change comprises the second susceptor material reversibly changing from a paramagnetic phase to a ferromagnetic phase.

19. The method of claim 16, wherein the first phase-change comprises the second susceptor material reversibly changing from a ferromagnetic phase to a paramagnetic phase.

20. The method of claim 16, wherein the first and second susceptor materials have different geometrical configurations than one another.

21. The method of claim 20, wherein one of the first and second susceptor materials distributed within the aerosol-forming substrate.

22. The method of claim 21, wherein the other of the first and second susceptor materials is located outside of the aerosol-forming substrate.

23. The method of claim 16, wherein at least one of the first and second susceptor materials is particulate.

24. The method of claim 16, wherein a concentration by weight of the second susceptor material is lower than a concentration by weight of the first susceptor material.

25. A system for heating an aerosol-forming substrate to a predefined maximum temperature, the device comprising: an aerosol-forming article comprising the aerosol-forming substrate and first and second susceptor materials each in thermal proximity to the aerosol-forming substrate; a cavity configured to receive the aerosol-forming article; an inductive heating device; and circuitry configured to: activate the inductive heating device so as to inductively heat the first susceptor material such that the first susceptor material heats the aerosol-forming substrate to form an aerosol; detect a first phase-change of the second susceptor material during the inductive heating, the first phase-change occurring at the predefined maximum temperature; and responsive to detecting the first phase-change of the second susceptor material, deactivate the inductive heating device to stop inductively heating the first susceptor material.

26. The system of claim 25, the circuitry further being configured to, subsequent to stopping the inductive heating: allow the second susceptor material to cool, a second phase-change of the second susceptor material occurring during the cooling; detect the second phase-change of the second susceptor material during the cooling; and responsive to detecting the second phase-change of the second susceptor material, activate the inductive heating device.

27. The system of claim 26, wherein the second phase-change comprises the second susceptor material reversibly changing from a paramagnetic phase to a ferromagnetic phase.

28. The system of claim 25, wherein the first phase-change comprises the second susceptor material reversibly changing from a ferromagnetic phase to a paramagnetic phase.

29. The system of claim 25, wherein the first and second susceptor materials have different geometrical configurations than one another.

30. The system of claim 29, wherein one of the first and second susceptor materials is distributed within the aerosol-forming substrate.

31. The system of claim 30, wherein the other of the first and second susceptor materials is located outside of the aerosol-forming substrate.

32. The system of claim 25, wherein at least one of the first and second susceptor materials is particulate.

33. The system of claim 25, wherein a concentration by weight of the second susceptor material is lower than a concentration by weight of the first susceptor material.

34. An aerosol-generating article, comprising: an aerosol-forming substrate; a first susceptor material in thermal proximity of the aerosol-forming substrate and having a first Curie temperature; and a second susceptor material in thermal proximity of the aerosol-forming substrate and having a second Curie temperature that is lower than the first Curie temperature, wherein the first and second susceptor materials have different geometrical configurations than one another.

35. The aerosol-generating article of claim 34, wherein one of the first and second susceptor materials is distributed within the aerosol-forming substrate.

36. The aerosol-generating article of claim 35, wherein the other of the first and second susceptor materials is located outside of the aerosol-forming substrate.

Description

[0023] The afore-described embodiments of the aerosol-forming substrate and of the aerosol-delivery system will become more apparent from the following detailed description, reference being made to the accompanying schematic drawings which are not to scale, in which:

[0024] FIG. 1 is a schematic drawing of an aerosol-delivery system comprising an inductive heating device and an aerosol-forming substrate inserted into a heating chamber;

[0025] FIG. 2 shows a first embodiment of an aerosol-forming substrate with first and second susceptor materials of particulate configuration;

[0026] FIG. 3 shows a second embodiment of an aerosol-forming substrate with a particulate second susceptor material combined with a first susceptor material of filament configuration;

[0027] FIG. 4 shows another embodiment of an aerosol-forming substrate, in which first and second susceptor materials of particulate configuration have been assembled to form a unitary structure; and

[0028] FIG. 5 shows a further embodiment of an aerosol-forming substrate with a second susceptor material of particulate material combined with a first susceptor material of mesh-like configuration.

[0029] Inductive heating is a known phenomenon described by Faraday's law of induction and Ohm's law. More specifically, Faraday's law of induction states that if the magnetic induction in a conductor is changing, a changing electric field is produced in the conductor. Since this electric field is produced in a conductor, a current, known as an eddy current, will flow in the conductor according to Ohm's law. The eddy current will generate heat proportional to the current density and the conductor resistivity. A conductor which is capable of being inductively heated is known as a susceptor material. The present invention employs an inductive heating device equipped with an inductive heating source, such as, e.g., an induction coil, which is capable of generating an alternating electromagnetic field from an AC source such as an LC circuit. Heat generating eddy currents are produced in the susceptor material which is in thermal proximity to a solid material which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate and which is comprised in an aerosol-forming substrate. The term solid as used herein encompasses solid materials, semi-solid materials, and even liquid components, which may be provided on a carrier material. The primary heat transfer mechanisms from the susceptor material to the solid material are conduction, radiation and possibly convection.

[0030] In schematic FIG. 1 an exemplary embodiment of an aerosol-delivery system according to the invention is generally designated with reference numeral 100. The aerosol-delivery system 100 comprises an inductive heating device 2 and an aerosol-forming substrate 1 associated therewith. The inductive heating device 2 may comprise an elongated tubular housing 20 having an accumulator chamber 21 for accommodating an accumulator 22 or a battery, and a heating chamber 23. The heating chamber 23 may be provided with an inductive heating source, which, as shown in the depicted exemplary embodiment, may be constituted by an induction coil 31 which is electrically connected with an electronic circuitry 32. The electronic circuitry 32 may e.g. be provided on a printed circuit board 33 which delimits an axial extension of the heating chamber 23. The electric power required for the inductive heating is provided by the accumulator 22 or the battery which is accommodated in the accumulator chamber 21 and which is electrically connected with the electronic circuitry 32. The heating chamber 23 has an internal cross-section such that the aerosol-forming substrate 1 may be releasably held therein and may easily be removed and replaced with another aerosol-forming substrate 1 when desired.

[0031] The aerosol-forming substrate 1 may be of a generally cylindrical shape and may be enclosed by a tubular casing 15, such as, e.g., an overwrap. The tubular casing 15, such as, e.g. the overwrap, may help to stabilize the shape of the aerosol-forming substrate 1 and to prevent an accidental loss of the contents of the aerosol-forming substrate 1. As shown in the exemplary embodiment of the aerosol-delivery system 100 according to the invention, the aerosol-forming substrate 1 may be connected to a mouthpiece 16, which with the aerosol-forming substrate 1 inserted into the heating chamber 23 at least partly protrudes from the heating chamber 23. The mouthpiece 16 may comprise a filter plug 17 filter plug, which may be selected in accordance with the composition of the aerosol-forming substrate 1. The aerosol-forming substrate 1 and the mouthpiece 16 may be assembled to form a structural entity. Every time a new aerosol-forming substrate 1 is to be used in combination with the inductive heating device 2, the user is automatically provided with a new mouthpiece 16, which might be appreciated from a hygienic point of view.

[0032] As shown in FIG. 1 the induction coil 31 may be arranged in a peripheral region of the heating chamber 23, in vicinity of the housing 20 of the inductive heating device 2. The windings of the induction coil 31 enclose a free space of the heating chamber 23 which is capable to accommodate the aerosol-forming substrate 1. The aerosol-forming substrate 1 may be inserted into this free space of the heating chamber 23 from an open end of the tubular housing 20 of the inductive heating device 2 until it reaches a stop, which may be provided inside the heating chamber 23. The stop may be constituted by at least one lug protruding from an inside wall of the tubular housing 20, or it may be constituted by the printed circuit board 33, which delimits the heating chamber 23 axially, as it is shown in the exemplary embodiment depicted in FIG. 1. The inserted aerosol-forming substrate 1 may be releasably held within the heating chamber 23 e.g. by an annular sealing gasket 26, which may be provided in vicinity of the open end of the tubular housing 20.

[0033] The aerosol-forming substrate 1 and the optional mouthpiece 16 with the optional filter plug 17 are pervious to air. The inductive heating device 2 may comprise a number of vents 24, which may be distributed along the tubular housing 20. Air passages 34 which may be provided in the printed circuit board 33 enable airflow from the vents 24 to the aerosol-forming substrate 1. It should be noted, that in alternative embodiments of the inductive heating device 2 the printed circuit board 33 may be omitted such that air from the vents 24 in the tubular housing 20 may reach the aerosol-forming substrate 1 practically unimpeded. The inductive heating device 2 may be equipped with an air flow sensor (not shown in FIG. 1) for activation of the electronic circuitry 32 and the induction coil 31 when incoming air is detected. The air flow sensor may e.g. be provided in vicinity of one of the vents 24 or of one of the air passages 34 of the printed circuit board 33. Thus, a user may suck at the mouthpiece 16, in order to initiate the induction heating of the aerosol-forming substrate 1 Upon heating an aerosol, which is released by the solid material comprised in the aerosol-forming substrate 1, may be inhaled together with air which is sucked through the aerosol-forming substrate 1.

[0034] FIG. 2 schematically shows a first embodiment of an aerosol-forming substrate which is generally designated with reference numeral 1. The aerosol-forming substrate 1 may comprise a generally tubular casing 15, such as, e.g., an overwrap. The tubular casing 15 may be made of a material which does not noticeably impede an electromagnetic field reaching the contents of the aerosol-forming substrate 1. E.g. the tubular casing 15 may be a paper overwrap. Paper has a high magnetic permeability and in an alternating electromagnetic field is not heated by eddy currents. The aerosol-forming substrate 1 comprises a solid material 10 which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate 1 and at least a first susceptor material 11 for heating the aerosol-forming substrate 1. In addition to the first susceptor material 11 the aerosol-forming substrate 1 further comprises at least a second susceptor material 12. The second susceptor material 12 has a second Curie-temperature which is lower than a first Curie-temperature of the first susceptor material 11. Thus, upon inductive heating of the aerosol-forming substrate 1 the second susceptor material 12 will reach its specific second Curie temperature first. At the second Curie-temperature the second susceptor material 12 reversibly changes from a ferromagnetic phase to a paramagnetic phase. During the inductive heating of the aerosol-forming substrate 1 this phase-change of the second susceptor material 12 may be detected on-line and the inductive heating may be stopped automatically. Thus, the second Curie-temperature of the second susceptor material 12 corresponds to a predefined maximum heating temperature of the first susceptor material 11. After the inductive heating has been stopped the second susceptor material 12 cools down until it reaches a temperature lower than its second Curie-temperature at which it regains its ferromagnetic properties again. This phase-change may be detected on-line and the inductive heating may be activated again. Thus, the inductive heating of the aerosol-forming substrate 1 corresponds to a repeated activation and deactivation of the inductive heating device. The temperature control is accomplished contactless. Besides the electronic circuitry which may already be integrated in the inductive heating device there is no need for any additional circuitry and electronics.

[0035] By providing at least first and second susceptor materials 11, 12 having first and second Curie-temperatures distinct from one another, the heating of the aerosol-forming substrate 1 and the temperature control of the inductive heating may be separated. The first susceptor material 11 may be optimized with regard to heat loss and thus heating efficiency. Thus, the first susceptor material 11 should have a low magnetic reluctance and a correspondingly high relative permeability to optimize surface eddy currents generated by an alternating electromagnetic field of a given strength. The first susceptor material 11 should also have a relatively low electrical resistivity in order to increase Joule heat dissipation and thus heat loss. The second susceptor material 12 may be optimized in respect of temperature control. The second susceptor material 12 need not have any pronounced heating characteristic. Wth regard to the induction heating though, it is the second Curie temperature of the second susceptor material 12, which corresponds to the predefined maximum heating temperature of the first susceptor material 11.

[0036] The second Curie-temperature of the second susceptor material 12 may be selected such that upon being inductively heated an overall average temperature of the aerosol-forming substrate 1 does not exceed 240? C. The overall average temperature of the aerosol-forming substrate 1 here is defined as the arithmetic mean of a number of temperature measurements in central regions and in peripheral regions of the aerosol-forming substrate. In another embodiment of the aerosol-forming substrate 1 the second Curie-temperature of the second susceptor material 12 may be selected such that is does not exceed 370? C., in order to avoid a local overheating of the aerosol-forming substrate 1 comprising the solid material 10 which is capable of releasing volatile compounds that can form an aerosol.

[0037] The afore-described basic composition of the aerosol-forming substrate 1 of the exemplary embodiment of FIG. 2 is common to all further embodiments of the aerosol-forming substrate 1 which will be described hereinafter.

[0038] As shown in FIG. 2 the first and second susceptor materials 11, 12 may be of particulate configuration. The first and second susceptor materials 11, 12 preferably have an equivalent spherical diameter of 10 ?m-100 ?m and are distributed throughout the aerosol-forming substrate. The equivalent spherical diameter is used in combination with particles of irregular shape and is defined as the diameter of a sphere of equivalent volume. At the selected sizes the particulate first and second susceptor materials 11, 12 may be distributed throughout the aerosol-forming substrate 1 as required and they may be securely retained within aerosol-forming substrate 1. The particulate susceptor materials 11, 12 may be distributed throughout the solid material 10 about homogeneously, as shown in the exemplary embodiment of the aerosol-forming substrate 1 according to FIG. 2. Alternatively, they may have a distribution gradient e.g. from a central axis of the aerosol-forming substrate 1 to the periphery thereof, or they may be distributed throughout the aerosol-forming substrate 1 with local concentration peaks.

[0039] In FIG. 3 another embodiment of an aerosol-forming substrate is shown, which again bears reference numeral 1. The aerosol-forming substrate 1 may be of a generally cylindrical shape and may be enclosed by a tubular casing 15, such as, e.g., an overwrap. The aerosol-forming substrate comprises solid material 10 which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate 1 and at least first and second susceptor materials 11, 12. The first susceptor material 11 which is responsible for heating the aerosol-forming substrate 1 may be of a filament configuration. The first susceptor material of filament configuration may have different lengths and diameters and may be distributed more or less homogeneously throughout the solid material. As exemplarily shown in FIG. 3 the first susceptor material 11 of filament configuration may be of a wire-like shape and may extend about axially through a longitudinal extension of the aerosol-forming substrate 1. The second susceptor material 12 may be of particulate configuration and may be distributed throughout the solid material 10. It should be noted though, that as need may be, the geometrical configuration of the first and second susceptor materials 11, 12 may be interchanged. Thus, the second susceptor material 12 may be of filament configuration and the first susceptor material 11 may be of particulate configuration.

[0040] In FIG. 4 yet another exemplary embodiment of an aerosol-forming substrate is shown, which again is generally designated with reference numeral 1. The aerosol-forming substrate 1 may again be of a generally cylindrical shape and may be enclosed by a tubular casing 15, such as, e.g., an overwrap. The aerosol-forming substrate comprises solid material 10 which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate 1 and at least first and second susceptor materials 11, 12. The first and second susceptor materials 11, 12 may be of particulate configuration and may be assembled to form a unitary structure. In this context the expression assembled to form a unitary structure may include an agglomeration of the particulate first and second susceptor materials 11, 12 to granules of regular or irregular shape, having equivalent spherical diameters larger than those of the particulate first and second susceptor materials, respectively. It may also include a more or less homogeneous mixing of the particulate first and second susceptor materials 11, 12 and compressing and optionally sintering of the compressed particle mixture to form a filament or wire structure, which may extend about axially through a longitudinal extension of the aerosol-forming substrate 1, as is shown in FIG. 4.

[0041] In FIG. 5 a further exemplary embodiment of an aerosol-forming substrate is again designated generally with reference numeral 1. The aerosol-forming substrate 1 may again be of a generally cylindrical shape and may be enclosed by a tubular casing 15, such as, e.g., an overwrap. The aerosol-forming substrate comprises solid material 10 which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate 1 and at least first and second susceptor materials 11, 12. The first susceptor material 11 may be of a mesh-like configuration which may be arranged inside of the aerosol-forming substrate 1 or, alternatively, may at least partially form an encasement for the solid material 10. The term mesh-like configuration includes layers having discontinuities therethrough. For example the layer may be a screen, a mesh, a grating or a perforated foil. The second susceptor material 12 may be of particulate configuration and may be distributed throughout the solid material 10. Again it should be noted, that, as need may be, the geometrical configuration of the first and second susceptor materials 11, 12 may be interchanged. Thus, the second susceptor material 12 may be of a mesh-like configuration and the first susceptor material 11 may be of particulate configuration.

[0042] In yet another embodiment of the aerosol-forming substrate the first and second susceptor materials 11, 12 may be assembled to form a mesh-like structural entity. The mesh-like structural entity may, e.g., extend axially within the aerosol-forming substrate. Alternatively the mesh-like structural entity of first and second susceptor materials 11, 12 may at least partially form an encasement for the solid material. The term mesh-like structure designates all structures which may be assembled from the first and second susceptor materials and have discontinuities therethrough, including screens, meshes, gratings or a perforated foil. The afore-described embodiment of the aerosol-forming substrate is not shown in a separate drawing, because it basically corresponds to that of FIG. 5. The mesh-like structural entity is composed of horizontal filaments of first susceptor material 11 and of vertical filaments of second susceptor material 12, or vice versa. In such an embodiment of the aerosol-forming material there usually would be no separate particulate second susceptor material 12.

[0043] While different embodiments of the invention have been described with reference to the accompanying drawings, the invention is not limited to these embodiments. Various changes and modifications are conceivable without departing from the overall teaching of the present invention. Therefore, the scope of protection is defined by the appended claims.