Patent ID: 12201137

DETAILED DESCRIPTION

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.

In schematicFIG.1an exemplary embodiment of an aerosol-delivery system according to the invention is generally designated with reference numeral100. The aerosol-delivery system100comprises an inductive heating device2and an aerosol-forming substrate1associated therewith. The inductive heating device2may comprise an elongated tubular housing20having an accumulator chamber21for accommodating an accumulator22or a battery, and a heating chamber23. The heating chamber23may be provided with an inductive heating source, which, as shown in the depicted exemplary embodiment, may be constituted by an induction coil31which is electrically connected with an electronic circuitry32. The electronic circuitry32may e.g. be provided on a printed circuit board33which delimits an axial extension of the heating chamber23. The electric power required for the inductive heating is provided by the accumulator22or the battery which is accommodated in the accumulator chamber21and which is electrically connected with the electronic circuitry32. The heating chamber23has an internal cross-section such that the aerosol-forming substrate1may be releasably held therein and may easily be removed and replaced with another aerosol-forming substrate1when desired.

The aerosol-forming substrate1may be of a generally cylindrical shape and may be enclosed by a tubular casing15, such as, e.g., an overwrap. The tubular casing15, such as, e.g. the overwrap, may help to stabilize the shape of the aerosol-forming substrate1and to prevent an accidental loss of the contents of the aerosol-forming substrate1. As shown in the exemplary embodiment of the aerosol-delivery system100according to the invention, the aerosol-forming substrate1may be connected to a mouthpiece16, which with the aerosol-forming substrate1inserted into the heating chamber23at least partly protrudes from the heating chamber23. The mouthpiece16may comprise a filter plug17filter plug, which may be selected in accordance with the composition of the aerosol-forming substrate1. The aerosol-forming substrate1and the mouthpiece16may be assembled to form a structural entity. Every time a new aerosol-forming substrate1is to be used in combination with the inductive heating device2, the user is automatically provided with a new mouthpiece16, which might be appreciated from a hygienic point of view.

As shown inFIG.1the induction coil31may be arranged in a peripheral region of the heating chamber23, in vicinity of the housing20of the inductive heating device2. The windings of the induction coil31enclose a free space of the heating chamber23which is capable to accommodate the aerosol-forming substrate1. The aerosol-forming substrate1may be inserted into this free space of the heating chamber23from an open end of the tubular housing20of the inductive heating device2until it reaches a stop, which may be provided inside the heating chamber23. The stop may be constituted by at least one lug protruding from an inside wall of the tubular housing20, or it may be constituted by the printed circuit board33, which delimits the heating chamber23axially, as it is shown in the exemplary embodiment depicted inFIG.1. The inserted aerosol-forming substrate1may be releasably held within the heating chamber23e.g. by an annular sealing gasket26, which may be provided in vicinity of the open end of the tubular housing20.

The aerosol-forming substrate1and the optional mouthpiece16with the optional filter plug17are pervious to air. The inductive heating device2may comprise a number of vents24, which may be distributed along the tubular housing20. Air passages34which may be provided in the printed circuit board33enable airflow from the vents24to the aerosol-forming substrate1. It should be noted, that in alternative embodiments of the inductive heating device2the printed circuit board33may be omitted such that air from the vents24in the tubular housing20may reach the aerosol-forming substrate1practically unimpeded. The inductive heating device2may be equipped with an air flow sensor (not shown inFIG.1) for activation of the electronic circuitry32and the induction coil31when incoming air is detected. The air flow sensor may e.g. be provided in vicinity of one of the vents24or of one of the air passages34of the printed circuit board33. Thus, a user may suck at the mouthpiece16, in order to initiate the inductive heating of the aerosol-forming substrate1Upon heating an aerosol, which is released by the solid material comprised in the aerosol-forming substrate1, may be inhaled together with air which is sucked through the aerosol-forming substrate1.

FIG.2schematically shows a first embodiment of an aerosol-forming substrate which is generally designated with reference numeral1. The aerosol-forming substrate1may comprise a generally tubular casing15, such as, e.g., an overwrap. The tubular casing15may be made of a material which does not noticeably impede an electromagnetic field reaching the contents of the aerosol-forming substrate1. E.g. the tubular casing15may 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 substrate1comprises a solid material10which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate1and at least a first susceptor material11for heating the aerosol-forming substrate1. The first susceptor material11has a first Curie-temperature and is arranged in thermal proximity of the solid material10. 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 aerosol-forming substrate1further comprises at least a second susceptor material12having a second Curie-temperature which too is arranged in thermal proximity of the solid material. The first Curie-temperature of the first susceptor material11is lower than the second Curie-temperature of the second susceptor material12. The second Curie-temperature of the second susceptor material12defines a maximum heating temperature of the first and second susceptor materials11,12.

By having at least first and second susceptor materials11,12with specific first and second Curie-temperatures distinct from one another, the prerequisite for a more efficient and controlled inductive heating of the aerosol-forming substrate1and thus of a more efficient production of an aerosol is provided. The first and second susceptor materials11,12, each having its specific first or second Curie-temperature, may be activated separately. This may be achieved, e.g., with different frequencies of an alternating induction current and/or with different frequencies of an magnetic field causing the inductive heating of the first and second susceptor materials11,12. This allows for a more efficient distribution of the first and second susceptor materials11,12within the aerosol-forming substrate1, in order to achieve a customized depletion thereof. Thus, if, e.g., it is desired to have an increased heat deposition into peripheral regions of the aerosol-forming substrate1, the second susceptor material12having the higher second Curie-temperature, may be arranged preferably in the peripheral regions of the aerosol-forming substrate1, while the first susceptor material11may be arranged preferentially in a central region of the aerosol-forming substrate1. It is to be noted that if is deemed appropriate, the arrangement of the first and second susceptor materials11,12of the aerosol-forming substrate1can also be inverted; thus, the first susceptor material11being arranged in the peripheral regions while the second susceptor material12may e.g. be arranged in a central portion of the aerosol-forming substrate1. The aerosol-forming substrate1in accordance with the invention allows for a customized composition thereof in accordance with specific requirements. An overheating of the aerosol-forming substrate1may be prevented by selecting the second susceptor material12, which has the higher second Curie-temperature such, that it defines a maximum heating temperature of the first and second susceptor materials11,12. When the second susceptor material12has reached its second Curie-temperature, its magnetic properties change from a ferromagnetic phase to a paramagnetic phase. As a consequence hysteresis losses of the second susceptor material12disappear. During the inductive heating of the aerosol-forming substrate1this phase-change may be detected on-line and the heating process may be stopped automatically. Thus, an overheating of the aerosol-forming substrate1may be avoided. After the inductive heating has been stopped the second susceptor material12cools down until it reaches a temperature which is lower than its second Curie-temperature, at which it regains its ferromagnetic properties again and its hysteresis losses reappear. This phase-change may be detected on-line and the inductive heating may be activated again. Thus, the inductive heating of the aerosol-forming substrate1corresponds to a repeated activation and deactivation of the inductive heating device. The first susceptor material11is of no further concern for this overheating prevention, because its first Curie-temperature is already lower than the second Curie-temperature of the second susceptor material12.

The first and second susceptor materials11,12, both, may be optimized with regard to heat loss and thus heating efficiency. Thus, the first and second susceptor materials11,12should 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 and second susceptor materials11,12should also have relatively low electrical resistivities in order to increase Joule heat dissipation and thus heat loss.

The second Curie-temperature of the second susceptor material12may be selected such that upon being inductively heated an overall average temperature of the aerosol-forming substrate1does not exceed 240° C. The overall average temperature of the aerosol-forming substrate1here 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 substrate1the second Curie-temperature of the second susceptor material12may be selected such that is does not exceed 370° C., in order to avoid a local overheating of the aerosol-forming substrate1comprising the solid material10which is capable of releasing volatile compounds that can form an aerosol.

The afore-described basic composition of the aerosol-forming substrate1of the exemplary embodiment ofFIG.2is common to all further embodiments of the aerosol-forming substrate1which will be described hereinafter.

As shown inFIG.2the aerosol-forming substrate1comprises first and second susceptor materials11,12, which, both, may be of particulate configuration. The first and second susceptor materials11,12preferably have an equivalent spherical diameter of 10 μm-100 μm 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 materials11,12may be distributed throughout the aerosol-forming substrate1as required and they may be securely retained within aerosol-forming substrate1. The particulate susceptor materials11,12may be distributed throughout the solid material10about homogeneously, as shown in the exemplary embodiment of the aerosol-forming substrate1according toFIG.2.

FIG.3shows another embodiment of an aerosol-forming substrate1which again is generally designated with reference numeral1. The aerosol-forming substrate1may be of a generally cylindrical shape and may be enclosed by a tubular casing15, such as, e.g., an overwrap. The aerosol-forming substrate comprises solid material10which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate1and at least first and second susceptor materials11,12. The first and second susceptor materials11,12, both, may be of particulate configuration again, preferably having an equivalent spherical diameter of 10 μm-100 μm. The particulate first and second susceptor materials11,12may have a distribution gradient e.g. from a central axis of the aerosol-forming substrate1to the periphery thereof, or, as shown inFIG.3, the particulate first susceptor material11may be concentrated along a central of the aerosol-forming substrate1, while the particulate second susceptor material12may be distributed in peripheral regions of the aerosol-forming substrate1with local concentration peaks, or vice versa.

InFIG.4a further embodiment of an aerosol-forming substrate is shown, which again bears reference numeral1. The aerosol-forming substrate1may be of a generally cylindrical shape and may be enclosed by a tubular casing15, such as, e.g., an overwrap. The aerosol-forming substrate1comprises a solid material10which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate1and at least first and second susceptor materials11,12. The first susceptor material11may be of a filament configuration. The first susceptor material of filament configuration may have different lengths and diameters and may be distributed throughout the solid material. As exemplarily shown inFIG.4the first susceptor material11of filament configuration may be of a wire-like shape and may extend about axially through a longitudinal extension of the aerosol-forming substrate1. The second susceptor material12may be of particulate configuration and may be distributed throughout the solid material10with local concentration peaks. Alternatively the second susceptor material may also be homogeneously distributed throughout the solid material10. It should be noted though, that as need may be, the geometrical configuration of the first and second susceptor materials11,12may be interchanged. Thus, the second susceptor material12may be of filament configuration and the first susceptor material11may be of particulate configuration.

InFIG.5yet another exemplary embodiment of an aerosol-forming substrate is shown, which again is generally designated with reference numeral1. The aerosol-forming substrate1may again be of a generally cylindrical shape and may be enclosed by a tubular casing15, such as, e.g., an overwrap. The aerosol-forming substrate comprises solid material10which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate1and at least first and second susceptor materials11,12. The first susceptor material11may be of a mesh-like configuration which may be arranged inside of the aerosol-forming substrate1or, alternatively, may at least partially form an encasement for the solid material10. 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 material12may be of particulate configuration and may be distributed throughout the solid material10. Again it should be noted, that, as need may be, the geometrical configuration of the first and second susceptor materials11,12may be interchanged. Thus, the second susceptor material12may be of a mesh-like configuration and the first susceptor material11may be of particulate configuration.

InFIG.6still another exemplary embodiment of an aerosol-forming substrate is shown, which again is generally designated with reference numeral1. The aerosol-forming substrate1may again be of a generally cylindrical shape and may be enclosed by a tubular casing15, such as, e.g., an overwrap. The aerosol-forming substrate comprises solid material10which is capable of releasing volatile compounds that can form an aerosol upon heating of the aerosol-forming substrate1and at least first and second susceptor materials11,12. The first and second susceptor materials11,12may be assembled to form a mesh-like structural entity. The mesh-like structural entity may, e.g., extend axially within the aerosol-forming substrate1. Alternatively the mesh-like structural entity of first and second susceptor materials11,12may at least partially form an encasement for the solid material10. 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 mesh-like structural entity may be composed of horizontally extending filaments of first susceptor material11and of vertically extending filaments of second susceptor material12, or vice versa.

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.