Aerosol delivery system and method of operating the aerosol delivery system

Abstract

An aerosol delivery system includes an inductive heating device and an aerosol-forming article. The aerosol-forming article includes a plurality of aerosol-forming segments and at least two different susceptors. The inductive heating device includes a device housing including a cavity to accommodate at least a portion of the aerosol-forming article including the plurality of aerosol-forming segments, a coil arranged to surround the cavity, an electrical power source, and a power supply electronics connected to the electrical power source and to the coil. The power supply electronics supplies an alternating current to the coil to generate an alternating magnetic field having magnetic field strength and a frequency to, in at least one aerosol-forming segment, generate a thermal power which is greater than the rate of heat loss of this aerosol-forming segment.

Claims

1. An aerosol delivery system comprising: an inductive heating device and an aerosol-forming article, the aerosol-forming article comprising: a plurality of aerosol-forming segments; and at least two different susceptors, the at least two different susceptors having a different hysteresis loop area in a B-H-diagram, with each aerosol-forming segment of the plurality of aerosol-forming segments comprising in the respective aerosol-forming segment at least one susceptor of the at least two different susceptors; wherein the at least two different susceptors are thermally separated from each other by a thermo-insulating wall extending between the at least two different susceptors in an axial direction of the aerosol delivery system; the inductive heating device comprising: a device housing comprising a cavity having an internal surface shaped to accommodate at least a portion of the aerosol-forming article, the portion of the aerosol-forming article comprising at least the plurality of aerosol-forming segments; only one single coil, the single coil being arranged to completely surround a circumference of the cavity, a portion of the cavity completely surrounded by the single coil along the circumference of the cavity being sized and shaped to accommodate at least the portion of the aerosol-forming article comprising the plurality of aerosol-forming segments; an electrical power source; and a power supply electronics connected to the electrical power source and to the single coil, the power supply electronics being configured to supply an alternating current to the single coil to generate in the portion of the cavity completely surrounded by the single coil along the circumference of the cavity an alternating magnetic field having a predetermined magnetic field strength and a predetermined frequency adapted to in at least one aerosol-forming segment of the plurality of aerosol-forming segments of the aerosol-forming article generate a thermal power which is greater than the rate of heat loss of this at least one aerosol-forming segment.

2. The aerosol delivery system according to claim 1, wherein the at least two different susceptors are made of an electrically non-conductive material.

3. The aerosol delivery system according to claim 2, wherein the electrically non-conductive material is a ferrimagnetic ceramic material.

4. The aerosol delivery system according to claim 3, wherein the ferrimagnetic ceramic material is a ferrite.

5. The aerosol delivery system according to claim 1, wherein the power supply electronics is configured to supply the alternating current to the single coil such that the alternating magnetic field having the predetermined magnetic field strength and the predetermined frequency is adapted to in a single aerosol-forming segment of the plurality of aerosol-forming segments generate a thermal power which is greater than the rate of heat loss of the single aerosol-forming segment, and that the alternating magnetic field is further adapted to at the same time generate in each aerosol-forming segment other than the single aerosol-forming segment a thermal power which is smaller than the rate of heat loss of the respective other aerosol-forming segment.

6. The aerosol delivery system according to claim 5, wherein the power supply electronics is configured to supply the alternating current to the single coil such that during a first period of time the alternating magnetic field has a first predetermined magnetic field strength and a first predetermined frequency adapted to in the single aerosol-forming segment generate a thermal power which is greater than the rate of heat loss of the single aerosol-forming segment, and wherein the power supply is further configured to supply the alternating current to the single coil such that during a second period of time subsequent to the first period of time the alternating magnetic field has a second predetermined magnetic field strength and a second predetermined frequency different from the first predetermined magnetic field strength and the first predetermined frequency, the alternating magnetic field having the second predetermined magnetic field strength and the second predetermined frequency being adapted to in a further single aerosol-forming segment different from the single aerosol-forming segment generate a thermal power which is greater than the rate of heat loss of the further single aerosol-forming segment.

7. The aerosol delivery system according to claim 1, wherein the power supply electronics is configured to supply the alternating current to the single coil such that the alternating magnetic field having the predetermined magnetic field strength and the predetermined frequency is adapted to in a first aerosol-forming segment of the plurality of aerosol-forming segments generate a thermal power which is greater than the rate of heat loss of the first aerosol-forming segment, and that the alternating magnetic field having the predetermined magnetic field strength and the predetermined frequency is further adapted to at the same time generate in at least one further aerosol-forming segment different from the first aerosol-forming segment a thermal power which is greater than the rate of heat loss of the at least one further aerosol-forming segment.

8. A method of operating an aerosol delivery system, the method comprising: providing the aerosol delivery system according to claim 1; inserting at least a portion of the aerosol-forming article into the cavity of the device housing such that the plurality of aerosol-forming segments comprising the at least two different susceptors are completely surrounded by the single coil; generating in at least one of the aerosol-forming segments of the plurality of aerosol-forming segments a thermal power which is greater than the rate of heat loss of the at least one aerosol-forming segment with the aid of the power supply electronics supplying an alternating current to the single coil generating in the portion of the cavity completely surrounded by the single coil along the circumference of the cavity an alternating magnetic field having a predetermined magnetic field strength and a predetermined frequency.

9. The method according to claim 8, wherein the step of providing the aerosol delivery system comprises providing an aerosol-forming article in which the at least two different susceptors are made of an electrically non-conductive material.

10. The method according to claim 9, wherein the electrically non-conductive material is a ferrimagnetic ceramic material.

11. The method according to claim 10, wherein the ferrimagnetic ceramic material is a ferrite.

12. The method according to claim 8, wherein the method comprises with the aid of the alternating magnetic field having the predetermined magnetic field strength and the predetermined frequency generating in a single aerosol-forming segment of the plurality of aerosol-forming segments a thermal power which is greater than the rate of heat loss of the single aerosol-forming segment, while at the same time with the aid of the alternating magnetic field having the predetermined magnetic field strength and the predetermined frequency generating in each aerosol-forming segment other than the single aerosol-forming segment a thermal power which is smaller than the rate of heat loss of the respective other aerosol-forming segment.

13. The method according to claim 12, wherein the method comprises during a first period of time with the aid of the alternating magnetic field having a first predetermined magnetic field strength and a first predetermined frequency generating in the single aerosol-forming segment a thermal power which is greater than the rate of heat loss of the single aerosol-forming segment, and during a second period of time subsequent to the first period of time with the aid of the alternating magnetic field having a second predetermined magnetic field strength and a second predetermined frequency generating in a further single aerosol-forming segment a thermal power which is greater than the rate of heat loss of the further single aerosol-forming segment.

14. The method according to claim 8, wherein the method comprises with the alternating magnetic field having the predetermined field strength and the predetermined frequency generating in a first aerosol-forming segment of the plurality of aerosol-forming segments a thermal power which is greater than the rate of heat loss of the first aerosol-forming segment, and with the alternating magnetic field having the predetermined magnetic field strength and the predetermined frequency at the same time generate in at least one further aerosol-forming segment different from the first aerosol-forming segment a thermal power which is greater than the rate of heat loss of the at least one further aerosol-forming segment.

15. The aerosol delivery system according to claim 1, wherein the at least two different susceptors are thermally separated from each other by a thermo-insulating wall.

16. The aerosol delivery system according to claim 1, wherein the at least two different susceptors include a first susceptor and a second susceptor that are configured such that, at the predetermined frequency, only one of the first susceptor and the second susceptor is heated.

17. The aerosol delivery system according to claim 1, wherein the aerosol-forming article, including the at least two different susceptors, is removably insertable into the cavity of the inductive heating device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantageous aspects of the invention become apparent from the following description of embodiments of the invention with the aid of the drawings in which:

(2) FIG. 1 shows a first embodiment of an aerosol delivery system according to the invention;

(3) FIG. 2 shows a second embodiment of an aerosol delivery system according to the invention;

(4) FIG. 3 shows a B-H diagram of a ferrimagnetic susceptor;

(5) FIG. 4 shows diagrams representing the heat generated in the susceptor over the magnetic field strength H of an alternating magnetic field of a coil, and over the alternating current flowing through the said coil to generate the alternating magnetic field;

(6) FIG. 5 shows the thermal power generated in the susceptor over the alternating current flowing through the coil;

(7) FIG. 6 shows the thermal power and heat loss of the aerosol delivery system according to the invention in a first operating mode at low alternating current amplitude and high frequency, and

(8) FIG. 7 shows the thermal power and heat loss of the aerosol delivery system according to the invention in a second operating mode at high alternating current amplitude and low frequency.

DETAILED DESCRIPTION

(9) FIG. 1 shows a first embodiment of an aerosol delivery system according to the invention comprising an inductive heating device 1 and an aerosol-forming article 2 arranged in a cavity 11 of the device housing 10 of the inductive heating device 1. As shown in FIG. 1, the aerosol-forming article 2 may comprise a portion 20 comprising a first aerosol-forming segment 200 and a second aerosol-forming segment 201. Any number of aerosol-forming segments higher than two is generally possible, however, for the sake of simplicity only the first aerosol-forming segment 200 and the second aerosol-forming segment 201 are shown. Also, in the embodiment of the aerosol delivery system shown in FIG. 1 the first aerosol-forming segment 200 and the second aerosol-forming 201 are arranged to form an upper half and lower half of the (aerosol-forming) portion 20 of the aerosol-forming article 2, and the first aerosol-forming segment 200 and the second aerosol-forming segment 201 are thermally separated from each other by a thermo-insulating wall 202 (such as, for example, a thermo-insulating foil) indicated in FIG. 1 by the dashed line. And while the arrangement shown in FIG. 1 is one possible arrangement of the aerosol-forming segments, other arrangements of the aerosol-forming segments are possible. For example, the aerosol-forming segments may be embodied as cylindrical segments which are sequentially arranged one after the other along the longitudinal axis of the aerosol-forming article (with or without thermo-insulating wall arranged between adjacently arranged aerosol-forming segments).

(10) Each of the first aerosol-forming segment 200 and the second aerosol-forming segment 201 may comprise a solid tobacco-laden substrate. In the first aerosol-forming segment 200 there is arranged a first ferrimagnetic susceptor 203, and in the second aerosol-forming segment 201 there is arranged a second ferrimagnetic susceptor 204 different from the first ferrimagnetic susceptor 203. The first and second susceptors may have the shape of a small blade or strip, but may also be present in the form of particles or in any other suitable form. The first and second ferrimagnetic susceptors may be made of a ceramic material such as a ferrite, so that they are electrically non-conductive.

(11) Inductive heating device 1 of the embodiment of the aerosol delivery system shown in FIG. 1 further comprises a helically wound inductor coil L which is arranged to surround cavity 11 to be capable of inducing an alternating magnetic field within cavity 11.

(12) Inductive heating device 1 further comprises an electrical power source 12, which may be a DC power source such as a battery (e.g. a rechargeable battery). A docking port 13 comprising a pin 130 for recharging the battery is also indicated in FIG. 1 by way of example.

(13) Inductive heating device 1 further comprises a power supply electronics 14 connected to the electrical power source 12 (rechargeable battery) on one hand and to coil L on the other hand. Power supply electronics 14 is capable of supplying an alternating current to coil L. The electrical connections to coil L are arranged within device housing 10 and are not shown in FIG. 1 for the sake of simplicity. The power supply electronics 14 may typically comprise a microcontroller unit (not shown in detail) which may control the amplitude and frequency of the alternating current supplied to the coil L.

(14) FIG. 2 shows a further embodiment of the aerosol delivery system according to the invention comprising an inductive heating device 3 and an aerosol-forming article 4. However, FIG. 2 only very schematically shows this further embodiment of the aerosol delivery system, as many components that have been described in connection with the embodiment of FIG. 1 can be present in the embodiment of FIG. 2 as well, so that they need not be described in detail again. An essential difference of the embodiment shown in FIG. 2 vis-a-vis the embodiment shown in FIG. 1 is that the inductive heating device 3 of the embodiment of the aerosol delivery system shown in FIG. 2 comprises a mouthpiece 35 whereas the inductive heating device of the embodiment of FIG. 1 does not comprise such mouthpiece. Inductive heating device 3 comprises a device housing 30 comprising a cavity 31 in which an aerosol-forming article 4 is arranged. The aerosol-forming article 4 of this embodiment comprises only a portion 40 comprising a first aerosol-forming segment 400 and a second aerosol-forming segment 401 separated by a thermo-insulating wall 402 (indicated again by the dashed line), with a first susceptor 403 being arranged in the first aerosol-forming segment 400 and with a second susceptor 404 different from the first susceptor 403 being arranged in the second aerosol-forming segment 401. The inductive heating device 3 of the embodiment of the aerosol delivery system shown in FIG. 2 further comprises the coil L which is again arranged to surround cavity 31 to in operation generate an alternating magnetic field in cavity 31 where the aerosol-forming article is arranged.

(15) With the aid of FIG. 3 through FIG. 7 the operation of the aerosol delivery system according to the invention will now be described.

(16) In FIG. 3 a B-H-diagram of a susceptor made of a ferrimagnetic material such as a ferrite is shown (with B representing the magnetic flux density and H representing the magnetic field strength causing the magnetic flux density B). The graph 5 illustrates the well-known hysteresis loop. The area bounded by the outermost lines 50 of the graph 5 is representative of the maximum hysteresis which can be caused by an alternating magnetic field for this specific susceptor. The smaller inner curve 51 of the graph 5 is representative of the hysteresis caused by an alternating magnetic field having a magnetic field strength which is smaller than the magnetic field strength of the alternating magnetic field that causes the maximum possible hysteresis.

(17) The amount of heat q.sub.h(H) (for example measured in Joule) generated in the susceptor due to hysteresis losses during one cycle of the alternating magnetic field increases as the area 500 or 510, respectively, of the respective hysteresis loop caused by the alternating magnetic field increases (actually, the area 500 represents the maximum area possible and thus is representative of the maximum hysteresis loss possible during once cycle of the alternating magnetic field). In this regard, it is to be mentioned again that due to the susceptor being made of an electrically non-conductive material no eddy currents are generated and, consequently, there is no heat loss caused by eddy currents. However, once saturation occurs (at a magnetic field strength H.sub.sat which does not result in a further increase of the magnetic flux density B) the area of the hysteresis loop is not increased anymore even in case the magnetic field strength would be higher than H.sub.sat. Accordingly, the maximum amount of heat q.sub.max (H) that can be generated in the susceptor during one cycle of the alternating magnetic field cannot increase above q.sub.max (H). This becomes evident from the diagram on the left hand side of FIG. 4 showing the heat q.sub.h over the magnetic field strength H of the alternating magnetic field.

(18) As has been discussed further above, the alternating magnetic field is generated by an alternating current I flowing through the coil L. As the magnetic field strength H of the alternating magnetic field generated by an alternating current I flowing through the coil is directly proportional to that alternating current I, the amount of heat q.sub.h generated in the susceptor during one cycle of the alternating magnetic increases in the same manner, as shown in the diagram q.sub.h over I on the right hand side of FIG. 4.

(19) This means that the thermal power P.sub.S (the total amount of heat generated per unit of time, for example per second) generated in the susceptor increases as the frequency f of the alternating magnetic field (or of the alternating current I flowing through the coil L) increases, as is evident from the diagram in FIG. 5 showing the thermal power P.sub.S over the alternating current I at different frequencies f.sub.1, f.sub.2, f.sub.3, with f.sub.1 being lower than f.sub.2, and with f.sub.2 being lower than f.sub.3 (f.sub.1<f.sub.2<f.sub.3). As mentioned further above, the frequencies f.sub.1, f.sub.2 and f.sub.3 are preferably in the range of 5 MHz to 12 MHz.

(20) On the other hand, at an elevated temperature of the aerosol-forming segment (i.e. at a temperature above the temperature of the ambient) there is heat loss of the aerosol-forming segment to the ambient due to convective and diffusive heat loss. If the rate Q.sub.LOSS of heat loss to the ambient (the amount of heat lost to the ambient per unit of time, for example per second) is greater/higher than the thermal power P.sub.S (the amount of heat generated in the susceptor of the segment per same unit of time, for example per second) caused by the hysteresis losses, then the temperature of the aerosol-forming segment decreases. If the rate Q.sub.LOSS is smaller than the thermal power P.sub.S, the temperature of the aerosol-forming segment increases, the aerosol-forming segment is further heated. And in case the rate Q.sub.LOSS is equal to the thermal power P.sub.S the temperature of the aerosol-forming segment is kept constant and neither increases nor decreases.

(21) A line indicated “P.sub.S=Q.sub.LOSS” where the thermal power P.sub.S and the rate Q.sub.LOSS are equal for the specific susceptor is shown in FIG. 5. Accordingly, at a frequency f.sub.1 no further heating of the aerosol-forming segment is possible (regardless of the amplitude of the alternating current I) as in any event the thermal power P.sub.S is smaller than the rate Q.sub.LOSS of heat loss, whereas at frequencies f.sub.2 and f.sub.3 further heating of the susceptor and the aerosol-forming segment is possible by increasing the amplitude of the alternating current I flowing through the coil L and generating an increased magnetic field strength H of the alternating magnetic field.

(22) In FIG. 6 a first operating mode of the aerosol delivery system according to the invention is shown, in which the alternating magnetic field to which the two different susceptors arranged in the two different aerosol-forming segments (only one type of susceptor being arranged in each of the two aerosol-forming segments) are simultaneously exposed. In this first mode of operation the amplitude of the alternating current I is low while the predetermined frequency f is high. The frequency f is selected such that the condition f.Math.q.sub.max1>Q.sub.LOSS (which means P.sub.S1>Q.sub.LOSS) can be fulfilled. Similar to FIG. 5, the line P.sub.S=Q.sub.LOSS is indicated in the diagram in FIG. 6. Let us assume that the continuous line 600 in FIG. 6 represents the thermal power generated in the first susceptor while the dashed line 601 represents the thermal power generated in the second susceptor. Accordingly, continuous line 600 indicates that the first susceptor exhibits a sharper rise of thermal power but a lower maximum thermal power than the second susceptor (see dashed line 601). Or to say it in other words, the first susceptor has a lower saturation limit of hysteresis heat q.sub.max than the second susceptor but has a higher initial increase rate—increase rate starting at zero—as a function of the amplitude of the alternating current I through the coil L.

(23) Accordingly, in this first mode of operation at the predetermined high frequency f the amplitude of the alternating current I is selected from the range bounded by I.sub.1 and I.sub.2 in FIG. 6. I.sub.1 is selected such that at the predetermined high frequency f the condition Q.sub.LOSS=f.Math.q.sub.max1 is fulfilled. I.sub.2 is selected in a manner such that the condition Q.sub.LOSS=f.Math.q.sub.max2 is fulfilled. If the amplitude I of the alternating current is selected from this range, then the first susceptor (and, accordingly, the first aerosol-forming segment) is heated since for amplitudes I from this range the thermal power P.sub.S1 of the first susceptor according to continuous line 600 is higher than the rate of heat loss Q.sub.LOSS and, accordingly, the first susceptor is heated. At the same time the thermal power P.sub.S2 of the second susceptor according to dashed line 601 is lower than the rate of heat loss Q.sub.LOSS. and therefore the second susceptor (and, accordingly, the second aerosol-forming segment) is not heated but rather the temperature of the second susceptor decreases.

(24) In FIG. 7 a second operating mode of the aerosol delivery system according to the invention is shown, in which the alternating magnetic field to which the two different susceptors arranged in the two different aerosol-forming segments (only one type of susceptor being arranged in each of the two aerosol-forming segments) are simultaneously exposed. In this second mode of operation the amplitude of the alternating current I is high while the predetermined frequency f is low. The frequency f is selected such that the condition f.Math.q.sub.max1<Q.sub.LOSS<f.Math.q.sub.max2 can be fulfilled (which means P.sub.S1<Q.sub.LOSS<P.sub.S2). The line P.sub.S=Q.sub.LOSS is indicated in the diagram in FIG. 7, too. In this mode of operation at the predetermined low frequency f the amplitude of the alternating current I is selected to be higher than I.sub.1. I.sub.1 is selected such that the condition Q.sub.LOSS=f.Math.q.sub.2(I.sub.1) is fulfilled. If the amplitude I of the alternating current is selected to be higher than I.sub.1, then the second susceptor (and, accordingly, the second aerosol-forming segment) is heated since for amplitudes higher than I.sub.1 the thermal power P.sub.S2 of the second susceptor according to dashed line 601 is higher than the rate of heat loss Q.sub.LOSS and, accordingly, the second susceptor is heated. At the same time the thermal power P.sub.S1 of the first susceptor according to continuous line 600 is lower than the rate of heat loss Q.sub.LOSS and therefore the first susceptor (and, accordingly, the first aerosol-forming segment) is not heated but rather the temperature of the first susceptor decreases.

(25) It is thus possible through controlling the amplitude and frequency of the alternating current flowing through the coil to selectively heat only one of the two aerosol-forming segments.

(26) While the invention has been explained with the aid of embodiments shown in the drawings, it is clear to the person skilled in the art that various modifications and changes can be made without departing from the teaching underlying the invention. Only by way of example, it should be mentioned that a different arrangement of the individual segments is possible, and that a higher number of different segments and different susceptors is possible, too. However, many other changes and modification are possible and covered by the teaching underlying the invention, so that the scope of protection is not limited to the embodiments described but rather is defined by the appended claims.