Aerosol Generating System

Abstract

An aerosol generating system comprises an aerosol generating substrate, an inductor for generating a primary electromagnetic field, a primary susceptor configured to be inductively heated by the primary electromagnetic field and to solely heat the aerosol generating substrate, and a secondary susceptor configured to solely generate a secondary electromagnetic field. The secondary electromagnetic field is generated under the influence of the primary electromagnetic field and acts in opposition to the primary electromagnetic field.

Claims

1. An aerosol generating system, comprising: an aerosol generating substrate; an inductor for generating a primary electromagnetic field; a primary susceptor configured to be inductively heated by the primary electromagnetic field and to solely heat the aerosol generating substrate; a secondary susceptor configured to solely generate a secondary electromagnetic field acting in opposition to the primary electromagnetic field, wherein the secondary electromagnetic field is generated under the influence of the primary electromagnetic field.

2. An aerosol generating system according to claim 1, wherein the aerosol generating system comprises a housing defining a device boundary and the secondary electromagnetic field is configured to attenuate the primary electromagnetic field to produce a net field boundary which lies at least partly within the device boundary.

3. An aerosol generating system according to claim 1, wherein the secondary susceptor has a lower electrical resistivity than the primary susceptor.

4. An aerosol generating system according to claim 1, further comprising an electromagnetic shield positioned between the inductor and the secondary susceptor, the electromagnetic shield comprising a ferrimagnetic, non-electrically conductive material.

5. An aerosol generating system according to claim 1, wherein the inductor comprises a helical induction coil and the primary susceptor is arranged inside the helical induction coil.

6. An aerosol generating system according to claim 5, wherein the secondary susceptor comprises at least one susceptor disc positioned at an axial end of the helical induction coil.

7. An aerosol generating system according to claim 5, wherein the secondary susceptor comprises a susceptor mesh which surrounds at least part of the helical induction coil.

8. An aerosol generating system according to claim 1, wherein the secondary susceptor at least partially encloses the inductor, the primary susceptor and the aerosol generating substrate, and wherein the secondary susceptor comprises a cup-shaped susceptor element or a pair of cup-shaped susceptor elements.

9. An aerosol generating system according to claim 1, wherein the primary susceptor and the aerosol generating substrate are integrated into a planar body having main surfaces, and wherein the inductor comprises a pair of coil plates arranged on opposite sides of the planar body and each having a first surface which faces a corresponding main surface of the planar body.

10. An aerosol generating system according to claim 9, wherein each of the coil plates has a second surface opposite the first surface, and wherein the secondary susceptor comprises a pair of susceptor plates each of which is positioned adjacent to the second surface of a respective coil plate.

11. An aerosol generating system according to claim 10, further comprising an electromagnetic shield positioned between the inductor and the secondary susceptor, the electromagnetic shield comprising a ferrimagnetic, non-electrically conductive material, wherein the electromagnetic shield comprises a pair of electromagnetic shield members, and wherein one of said electromagnetic shield members is positioned between each of the coil plates and the adjacent susceptor plate.

12. An aerosol generating system according to claim 11, wherein each of the electromagnetic shield members comprises a ferrite slab.

13. An aerosol generating system according to claim 11, further comprising an air-gap layer positioned between each of the coil plates and the adjacent electromagnetic shield member.

14. An aerosol generating system according to claim 13, wherein each of the air-gap layers includes a thermally insulating material.

15. An aerosol generating system according to claim 9, wherein the secondary susceptor acts as an electrical conductor, and wherein the aerosol generating system comprises a self-oscillating circuit formed by the inductor and the secondary susceptor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a diagrammatic view of a first example of an aerosol generating system;

[0040] FIGS. 2a to 2c are diagrammatic views of part of the aerosol generating system of FIG. 1 illustrating the attenuation of a primary electromagnetic field by a secondary electromagnetic field, and in which the orientation and size of the triangular symbols are intended to denote respectively the direction and strength of the electromagnetic field;

[0041] FIG. 3 is a diagrammatic view of a second example of an aerosol generating system; and

[0042] FIG. 4 is a diagrammatic view of part of a third example of an aerosol generating system.

DETAILED DESCRIPTION OF EMBODIMENTS

[0043] Embodiments of the present disclosure will now be described by way of example only and with reference to the accompanying drawings.

[0044] Referring initially to FIG. 1, there is shown diagrammatically a first example of an aerosol generating system 1. The aerosol generating system 1 comprises a first example of an aerosol generating device 10 and an aerosol generating article 24. The aerosol generating device 10 has a proximal end 12 and a distal end 14 and comprises a device housing 16 which includes a power source 18 and a controller 20 which may be configured to operate at high frequency. The power source 18 typically comprises one or more batteries which could, for example, be inductively rechargeable.

[0045] The aerosol generating device 10 is generally cylindrical and comprises a generally cylindrical cavity 22, for example in the form of a heating compartment, at the proximal end 12 of the aerosol generating device 10. The cylindrical cavity 22 is arranged to receive a correspondingly shaped generally cylindrical aerosol generating article 24 containing an aerosol generating substrate 26 and a primary inductively heatable susceptor 28, for example in the form of first susceptor discs 28a formed of aluminium. The aerosol generating article 24 can comprise a non-metallic and air-permeable outer shell 24a to contain the aerosol generating substrate 26 and first susceptor discs 28a and to allow air to flow through the aerosol generating article 24. The aerosol generating article 24 is a disposable article which may, for example, contain tobacco as the aerosol generating substrate 26.

[0046] The aerosol generating device 10 comprises an inductor 29 in the form of a helical induction coil 30 which has a circular cross-section and which extends around the cylindrical cavity 22. In other non-illustrated embodiments, the helical induction coil may have a non-circular cross-section, for example elliptical, square or rectangular. The induction coil 30 can be energised by the power source 18 and controller 20. The controller 20 includes, amongst other electronic components, an inverter which is arranged to convert a direct current from the power source 18 into an alternating high-frequency current for the induction coil 30.

[0047] The aerosol generating device 10 includes one or more air inlets 32 in the device housing 16 which allow ambient air to flow into the cylindrical cavity 22. The aerosol generating device 10 also includes a mouthpiece 34 having an air outlet 36. The mouthpiece 34 is removably mounted on the device housing 16 at the proximal end 12 to allow access to the cylindrical cavity 22 for the purposes of inserting or removing an aerosol generating article 24.

[0048] As will be understood by one of ordinary skill in the art, when the induction coil 30 is energised during use of the aerosol generating system 1, an alternating and time-varying primary electromagnetic field 42 is produced as denoted schematically in FIG. 2a by the triangular symbols. The primary electromagnetic field 42 couples with the primary susceptor 28 and generates eddy currents and/or magnetic hysteresis losses in the first susceptor discs 28a causing them to heat up. As shown diagrammatically in FIG. 2a, the primary electromagnetic field 42 has a field boundary 90 that lies outside the boundary 92 of the aerosol generating device 10, for example as defined by the exterior of the device housing 16.

[0049] The first susceptor discs 28a can be in direct or indirect contact with the aerosol generating substrate 26, such that when the first susceptor discs 28a are inductively heated by the primary electromagnetic field 42 generated by the induction coil 30, heat is transferred from the first susceptor discs 28a to the aerosol generating substrate 26, for example by conduction, radiation and convection, to heat the aerosol generating substrate 26 without burning and thereby generate a vapour. The vaporisation of the aerosol generating substrate 26 is facilitated by the addition of air from the surrounding environment through the air inlets 32. The vapour generated by heating the aerosol generating substrate 26 exits the cylindrical cavity 22 through the air outlet 36 where it cools and condenses to form an aerosol that can be inhaled by a user of the device 10 through the mouthpiece 34. The flow of air through the cylindrical cavity 22, i.e. from the air inlets 32, through the cavity 22 and out of the air outlet 36 in the mouthpiece 34, can be aided by negative pressure created by a user drawing air from the air outlet 36 side of the device 10.

[0050] In addition to the primary susceptor 28 (i.e. the first susceptor discs 28a in the illustrated example), the aerosol generating system 1, and more particularly the aerosol generating device 10, includes a secondary susceptor 40. In the illustrated example, the secondary susceptor 40 comprises a pair of second susceptor discs 40a positioned at opposite axial ends of the helical induction coil 30. The second susceptor discs 40a may be ring-shaped as shown in FIG. 1. It may be advantageous to form the second susceptor discs 40a from a material (e.g. copper) which has a lower electrical resistivity than the material (e.g. aluminium) from which the first susceptor discs 28a are formed.

[0051] The second susceptor discs 40a are configured to generate a secondary electromagnetic field 44 as shown diagrammatically in FIG. 2b by the triangular symbols, under the influence of the primary electromagnetic field 42 generated by the induction coil 30. More particularly, the primary electromagnetic field 42 is absorbed by the second susceptor discs 40a, inducing an electrical current flow in the second susceptor discs 40a which generates a secondary electromagnetic field 44 that acts in opposition (e.g. by 180 degrees as shown in FIG. 2b) to the primary electromagnetic field 42. By acting in opposition to the primary electromagnetic field 42, the secondary electromagnetic field 44 attenuates the primary electromagnetic field 42 such that the resultant net electromagnetic field 46, shown schematically in FIG. 2c by the triangular symbols, has a net field boundary 94 that lies at least partly within the device boundary 92 of the aerosol generating device 10. As a result, the exposure of a user of the aerosol generating system 1 to the electromagnetic field can be reduced when compared to an aerosol generating device which does not employ a secondary susceptor 40.

[0052] Referring now to FIG. 3, there is shown a second example of an aerosol generating system 2 which is similar to the first example of the aerosol generating system 1 described above with reference to FIGS. 1 and 2 and in which corresponding components are identified using the same reference numerals.

[0053] The aerosol generating system 2 comprises a second example of an aerosol generating device 50 which is similar to the first example of the aerosol generating device 10 described above, and also comprises an aerosol generating article 24 as described above.

[0054] The aerosol generating device 50 includes a secondary susceptor 40 in the form of a susceptor mesh 52, for example formed of copper. The susceptor mesh 52 at least partially surrounds the helical induction coil 30. In the illustrated example, the susceptor mesh 52 comprises a substantially cylindrical mesh portion 54 and a substantially circular mesh portion 56 provided at an axial end of the induction coil 30.

[0055] The susceptor mesh 52 is configured to generate a secondary electromagnetic field 44, under the influence of the primary electromagnetic field 42 generated by the induction coil 30. More particularly, the primary electromagnetic field 42 is absorbed by the susceptor mesh 52, inducing an electrical current flow in the susceptor mesh 52 which generates a secondary electromagnetic field 44 that acts in opposition to the primary electromagnetic field 42. The secondary electromagnetic field 44 attenuates the primary electromagnetic field 42 as described above in connection with FIG. 1, such that the resultant net electromagnetic field 46 has a net field boundary 94 that lies at least partly within the device boundary 92 of the aerosol generating device 50.

[0056] The aerosol generating device 50 can also include an electromagnetic shield 60 which can be positioned between the induction coil 30 and the susceptor mesh 52. The electromagnetic shield 60 is typically formed of a ferrimagnetic, non-electrically conductive material such as ferrite. In the example shown in FIG. 3, the electromagnetic shield 60 comprises a substantially cylindrical shield portion 62, for example in the form of a substantially cylindrical sleeve, which is positioned radially outwardly of the induction coil 30 so as to extend circumferentially around the induction coil 30. The electromagnetic shield 60 also comprises a first circular shield portion 64, provided at an axial end of the induction coil 30. The electromagnetic shield 60 can also comprise a second circular shield portion 66, which can be provided at a second axial end of the induction coil 30.

[0057] Referring now to FIG. 4, there is shown part of a third example of an aerosol generating system 3 which is similar to the first and second examples of the aerosol generating system 1, 2 described above with reference to FIGS. 1 to 3, and in which corresponding components are identified using the same reference numerals.

[0058] The aerosol generating system 3 comprises a third example of an aerosol generating device 70 which shares some similarities with the first and second examples of the aerosol generating device 10, 50 described above and only part of which is shown in FIG. 4. In the aerosol generating device 70, the inductor 29 comprises a pair of coil plates 72 arranged on opposite sides of a cavity 74 adapted to receive a plate-shaped aerosol generating article 76. The plate-shaped aerosol generating article 76 comprises a planar body 77 having main surfaces 78 and includes an aerosol generating substrate 26 and a primary susceptor 28, for example a planar susceptor positioned between two layers of aerosol generating material.

[0059] Each coil plate 72 includes a spirally wound planar coil 80 and can be formed as a multilayer printed circuit board in which each planar coil 80 is formed as a copper track. Each coil plate 72 has a first surface 72a which faces a corresponding main surface 78 of the planar body 77. In some embodiments, the first surface 72a may be coated with a thermally conductive material, for example so that heat losses from the planar coils 80 can reach the aerosol generating substrate 26 to contribute to the heating thereof. The planar coils 80 (flat coils in the illustrated example) are arranged to generate a primary electromagnetic field 42 in the same manner as the helical induction coil 30 described above. Each planar coil 80 includes a first electrode 80a which is connected to the power source 18 and controller 20. Each planar coil 80 also includes a second electrode 80b and the second electrodes 80b can be connected by a center tap (not shown in FIG. 4) which is conventional in the art and does not require further explanation.

[0060] The aerosol generating device 70 includes a secondary susceptor 40 in the form of a pair of susceptor plates 82, with each susceptor plate 82 being positioned adjacent to a second surface 72b of a respective coil plate 72. The susceptor plates 82 are configured to generate a secondary electromagnetic field 44, under the influence of the primary electromagnetic field 42 generated by the coil plates 72. More particularly, the primary electromagnetic field 42 is absorbed by the susceptor plates 82, inducing an electrical current flow in the susceptor plates 82 which generates a secondary electromagnetic field 44 that acts in opposition to the primary electromagnetic field 42 generated by the coil plates 72. The secondary electromagnetic field 44 attenuates the primary electromagnetic field 42 as described above in connection with FIGS. 1 to 3, such that the resultant net electromagnetic field 46 has a net field boundary 94 that lies at least partly within the boundary 92 of the aerosol generating device 70.

[0061] The aerosol generating device 70 can also include substantially planar electromagnetic shield members 84, one of which is positioned between each coil plate 72 and the adjacent susceptor plate 82. Each electromagnetic shield member 84 is typically formed of a ferrimagnetic, non-electrically conductive material and in the illustrated example each electromagnetic shield member 84 comprises a ferrite slab. Each electromagnetic shield member 84 can be spaced from the adjacent coil plate 72 by an air-gap layer 86, and the air-gap layer 86 can include a thermally insulating material such as a ceramic or foam glass to prevent unwanted heat transfer within the aerosol generating device 70, for example from the coil plates 72 to other component parts of the aerosol generating device 70.

[0062] Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the above-described exemplary embodiments.

[0063] Any combination of the above-described features in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0064] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.