Patent Description:
It is known to provide an aerosol-generating device for generating an inhalable vapor. Such devices may heat an aerosol-forming substrate contained in an aerosol-generating article without burning the aerosol-forming substrate. The aerosol-generating article may have a shape suitable for insertion of the aerosol-generating article into a heating chamber of the aerosol-generating device. For example, the aerosol-generating article may have a rod shape. A heating element may be arranged in or around the heating chamber for heating the aerosol-forming substrate once the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device.

It is known to provide modular aerosol-generating devices comprising two or more sub-units being detachably mounted to one another. Electric connectors may be provided to electrically connect a power source within one sub-unit to an electric consumer in another sub-unit in the assembled state.

Electric connectors often comprise sensible connecting surfaces, for example metallic surfaces, which are brought into intimate physical contact to establish the electric connection. Processes like surface oxidation, or deposition of liquids or solid particulates, may lead to a reduction in conductance of the metallic surface. This may adversely affect the electric connection.

These effects may be particularly severe in an aerosol-generating system, where an aerosol-forming substrate is heated but not burnt. Heat and moisture generated during aerosolization may promote surface oxidation of a connecting surface. Particulates of the aerosol-forming substrate may be inadvertently deposited on a connecting surface.

Electric connectors often comprise material transitions between conducting and nonconducting materials, for example a metallic surface adjacent to a plastic surface. Material transitions may be accompanied by gaps or surface corrugations. Moisture may inadvertently enter an interior of the device through a gap. Particulate matter may inadvertently adhere at surface corrugations.

Electric connectors often require a precise alignment of opposing conducting surfaces of the parts to be connected.

<CIT> relates to a cartomizer of an electronic vaping device including a heater circuit which is located adjacent an air passage thereof. The heater circuit includes an electrically resistive heater in electrical communication with a secondary coil. A wick extends across the air passage. The wick is configured to draw pre-vapor formulation from a reservoir toward the heater. The heater is configured to heat the pre-vapor formulation to a temperature sufficient to vaporize the pre-vapor formulation and form a vapor. The cartomizer is connectable to a power supply component which includes a power source in electrical communication with a primary coil. The power supply component is configured to induce sufficient voltage in the secondary coil of the heater circuit such that the secondary coil is configured to heat the heater and vaporize the pre-vapor formulation when the primary coil is powered by the power source.

<CIT> discloses an electronic cigarette comprising an electric heating device for heating tobacco.

It would be desirable to provide a modular aerosol-generating device with durable electric connectors. It would be desirable to provide a modular aerosol-generating device with a stably functioning electric connection between sub-units. It would be desirable to provide a modular aerosol-generating device which allows attaching and detaching of sub-units in an easy-to-operate manner. It would be desirable to provide a modular aerosol-generating device which is easy to clean.

According to an embodiment of the invention there is provided an aerosol-generating device as defined in claim <NUM>.

By means of the inductive coupling of the primary coil in the main body and the secondary coil in the mouthpiece electric connectors with sensible connecting surfaces, for example metallic surfaces, for connecting the mouthpiece and to the main body may be avoided. By means of the inductive coupling of the primary coil in the main body and the secondary coil in the mouthpiece, a modular aerosol-generating device with durable electric connectors may be provided. The modular aerosol-generating device may allow a stably functioning electric connection between sub-units. For example, the primary coil may be embedded within a plastic housing of the main body and the secondary coil may be embedded within a plastic housing of the mouthpiece such that no open metallic connector sides are required.

A need for cleaning of open metallic connector sides may be avoided by the inductive coupling. The modular aerosol-generating device may be easy to clean. The inductive coupling of the modular aerosol-generating device may allow attaching and detaching of sub-units in an easy-to-operate manner. For example, it may not be necessary to precisely align respective metallic electric connectors of the main body and the mouthpiece.

Electric power may be inductively transferred from the primary coil to the secondary coil. Thus, the primary coil may be an active coil and the secondary coil may be a passive coil of the inductive system.

The power transfer by inductive coupling is based on the physical principle of mutual inductance. The system of an active helical coil and a passive helical coil could be considered as effectively two air-cored solenoids. The magnetic flux induced in the active coil will induce an equal and opposite electromotive force (emf)' 'ε' in the passive coil.

In an embodiment, the active coil entirely coaxially surrounds the passive coil, both coils have the same number of turns and the same length in a direction perpendicular to a diameter of a turn. If it is further assumed that there is no flux leakage, and the two coils are perfectly magnetically coupled, then, it can be deduced that the flux in the active coil 'Φactive' equals the flux in the passive coil 'Φpassive'. This is shown in equation (<NUM>): <MAT>.

The magnetic field strength 'B' in the active coil is given in equation (<NUM>): <MAT>.

'µ<NUM>' is the magnetic constant, 'I' is the electric current, 'N' is the number of turns of the coil, and 'I' is the length of the coil. The magnetic flux in the active coil can then be written using 'Φactive = B · A '. 'A' is the cross-sectional area of the coil in a direction perpendicular to its length. Assuming a circular cross-section and a radius of a turn 'R': <MAT>.

The mutual inductance 'M' is the linked inductance in the two coils. As a result of the perfect magnetic linkage, it is then possible to describe the inductance passing through the passive coil as: <MAT>.

Then it can be stated simply that the induced emf 'ε' in the passive coil is equal to: <MAT>.

Evidently this is an ideal model and there will be losses in the system, the induced emf will be less than calculated. Losses can be approximated with a linear efficiency factor 'η'. Hence, the final equation for the induced voltage in the passive coil can be written by combining equations. <NUM>, <NUM>, <NUM>, and <NUM>.

Exemplary dimensions of the two coils are a radius 'R' of a turn of <NUM> millimeters of the active coil, a radius of a turn of <NUM> millimeters of the passive coil arranged coaxially within the active coil, <NUM> windings 'N' for each coil, and a length 'I' of <NUM> millimeters of both coils. Using these dimensions, and further assuming a linear efficiency factor 'η' of <NUM>, the relationship between the emf in the passive coil and the rate of change of the active current can be calculated: <MAT>.

Using equation (<NUM>) it is now possible to explore the circuit requirements of the system.

It is evident from the order of magnitude of 'M' that a high frequency is required in order to induce an emf capable of powering the heater at a typical value of, for example, about <NUM> watts. With a typical peak-to-peak current of, for example, about <NUM> amperes in the active circuit, it is possible to build the governing equations of the circuit and plot the power transfer in the passive side against the frequency of the system. The leakage inductance ' <MAT>' of the passive side can be calculated using the coupling constant 'η' which is a component of the passive inductance which is not linked to the active side: <MAT>.

The device will have to compensate for the leakage inductance losses in the passive side. Using equation (<NUM>), ' <MAT>' is calculated to be close to <NUM>·<NUM>-<NUM> henry. Having a simple basis circuit in of the passive side comprising the passive coil and a load resistor, the losses in the passive side of the circuit are approximately <NUM>% at the desired operating power of <NUM> watts.

If a parallel compensatory inductor 'Lcomp' were to be introduced across the load, it could be calibrated to cancel the effects of the leakage inductance. Adding a <NUM> nanohenry inductor, the efficiency in the passive side of the coil at the <NUM> watts operating point is about <NUM>%. The system frequency does need to be higher in order to reach the same transferred power, with the simple circuit operating at <NUM> and the compensated circuit at <NUM>. It may thus be desirable to construct the device with a compensatory inductor on <NUM> nanohenry and operate it at a <NUM> frequency.

The primary coil may be in wired connection to the power supply. The secondary coil may be in wired connection to the resistive heating element. The primary coil and the power supply may form part of a primary wired circuit housed within the main body. The secondary coil and the resistive heating element may form part of a secondary wired circuit housed within the mouthpiece. Electric power may be inductively transferred from the primary wired circuit to the secondary wired circuit.

In some embodiments, only the main body comprises a power supply. In other words, in some embodiments, the mouthpiece does not comprise a power supply.

In some embodiments, there are no wired connections between the main body and the mouthpiece. In other words, in some embodiments, the sole electric connection between the main body and the mouthpiece is established via the inductive coupling of the primary coil and the secondary coil.

The aerosol-generating device may be configured such that electric power transferred from the primary coil to the secondary coil via inductive coupling is used to heat the resistive heating element.

The aerosol-generating device may be configured such that the electric power used for heating the resistive heating element is supplied from the secondary coil to the resistive heating element by a wired connection.

Preferably, the aerosol-generating device comprises a power supply configured to supply power to the heating element. The power supply preferably comprises a power source. Preferably, the power source is a battery, such as a lithium ion battery. As an alternative, the power source may be another form of charge storage device such as a capacitor. The power source may require recharging. For example, the power source may have sufficient capacity to allow for the continuous generation of aerosol for a period of around six minutes or for a period that is a multiple of six minutes. In another example, the power source may have sufficient capacity to allow for a predetermined number of puffs or discrete activations of the heater assembly.

The power supply may comprise control electronics. The control electronics may comprise a microcontroller. The microcontroller is preferably a programmable microcontroller. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the primary coil. Power may be supplied to the primary coil continuously following activation of the system or may be supplied intermittently, such as on a puff-by-puff basis. The power may be supplied to the primary coil in the form of pulses of electric current.

The aerosol-generating device may be configured to supply an alternating current (AC) to the primary coil.

The control electronics may comprise a DC/AC converter to convert direct current (DC) provided by the power source into AC to be supplied to the primary coil. The control electronics may comprise a DC/AC converter comprising two transistors in a half-bridge configuration. The control electronics may comprise a DC/AC converter comprising a full bridge configuration with <NUM> transistors operating in pairs. A full bridge configuration may advantageously allow for stronger amplification of the power from the power supply going into the DC/AC converter. This may allow using a smaller battery with a lower voltage. The DC/AC converter may comprise a LC filter.

The aerosol-generating may comprise one or both of a half-bridge driver and a half-bridge. The aerosol-generating may comprise a LC filter. The aerosol-generating may comprise a half-bridge driver and a half-bridge and a LC filter.

The aerosol-generating device may be configured to induce an alternating current in the secondary coil.

The aerosol-generating device may be configured to supply AC induced in the secondary coil to the resistive heating element.

The mouthpiece may comprise a rectifier. The mouthpiece may comprise a rectifier arranged in electric connection between the secondary coil and the resistive heating element to supply direct current to the resistive heating element. The rectifier may be connected in series between the secondary coil and the resistive heating element.

The primary coil and the secondary coil may be made of the same material. The primary coil and the secondary coil may be made of different materials. Suitable materials for one or both the primary coil and the secondary coil may be those metals and alloys commonly known to the skilled person to be used for inductor coils. Exemplary materials are copper or steel.

The thickness of the coiled wire of the primary coil and the secondary coil may be the same or may be different. The thickness of the coiled wire may be between <NUM> millimeter and <NUM> millimeters, preferably between <NUM> millimeter and <NUM> millimeter.

The primary coil and the secondary coil may be helical coils. One or both of the primary coil and the secondary coil may have a plurality of windings. Either one of the primary coil and the secondary coil may have between <NUM> and <NUM> windings, preferably between <NUM> and <NUM> windings, more preferably between <NUM> and <NUM> windings, most preferably <NUM> windings. The primary coil and the secondary coil may have a different number of windings. In some embodiments, the number of windings of the primary coil differs from the number of windings of the secondary coil by less than <NUM> windings, or by less than <NUM> windings, or by less than <NUM> windings, or by less than <NUM> windings. The primary coil and the secondary coil may have the same number of windings. The primary coil and the secondary coil may have the same number of windings and may have between <NUM> and <NUM> windings, preferably between <NUM> and <NUM> windings, more preferably between <NUM> and <NUM> windings, most preferably <NUM> windings.

Either one of the primary coil and the secondary coil may have a length in a direction perpendicular to the diameter of a winding of between <NUM> and <NUM> millimeters, preferably between <NUM> and <NUM> millimeters, more preferably between <NUM> and <NUM> millimeters, most preferably about <NUM> millimeters. The primary coil and the secondary coil may have different lengths. The primary coil and the secondary coil may have the same lengths in a direction perpendicular to the diameter of a winding. The primary coil and the secondary coil may have the same length in a direction perpendicular to the diameter of a winding and the length may be between <NUM> and <NUM> millimeters, preferably between <NUM> and <NUM> millimeters, more preferably between <NUM> and <NUM> millimeters, most preferably about <NUM> millimeters.

Either one of the primary coil and the secondary coil may have a diameter of a winding of between <NUM> and <NUM> millimeters, preferably between <NUM> and <NUM> millimeters, more preferably between <NUM> and <NUM> millimeters.

The primary coil and the secondary coil may have different diameters of a winding. The primary coil may be arranged coaxially around the secondary coil when the mouthpiece is connected to the main body and the diameter of a winding of the primary coil may be about <NUM> millimeters and the diameter of a winding of the secondary coil may be about <NUM> millimeters. In some embodiments, the primary coil is arranged coaxially around the secondary coil when the mouthpiece is connected to the main body, the diameter of a winding of the primary coil is about <NUM> millimeters, the diameter of a winding of the secondary coil is about <NUM> millimeters, and the primary coil and the secondary coil each have <NUM> windings and each have a length in a direction perpendicular to the diameter of a winding of about <NUM> millimeters.

The secondary coil may be arranged coaxially around the primary coil when the mouthpiece is connected to the main body and the diameter of a winding of the secondary coil may be about <NUM> millimeters and the diameter of a winding of the primary coil may be about <NUM> millimeters. In some embodiments, the secondary coil is be arranged coaxially around the primary coil when the mouthpiece is connected to the main body, the diameter of a winding of the secondary coil is about <NUM> millimeters, the diameter of a winding of the primary coil is about <NUM> millimeters, and the primary coil and the secondary coil each have <NUM> windings and each have a length in a direction perpendicular to the diameter of a winding of about <NUM> millimeters.

The aerosol-generating device may be configured to operate the primary coil with an alternating current at an operating frequency of between <NUM> and <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>, most preferably about <NUM>.

The aerosol-generating device may comprise a parallel compensatory inductor. The compensatory inductor may be calibrated to cancel effects of leakage inductance. This may advantageously help to compensate leakage inductive losses in the passive side. The compensatory inductor may be a <NUM> to <NUM> nanohenry inductor, preferably <NUM> to <NUM> nanohenry inductor, more preferably a <NUM> nanohenry inductor.

The aerosol-generating device may comprise a <NUM> nanohenry compensatory inductor and may be configured to operate the primary coil at an alternating current with an operating frequency of between <NUM> and <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>, most preferably about <NUM>.

The power supply may provide a peak-to-peak AC of about <NUM> amperes and the aerosol-generating device may be configured to supply about <NUM> Watts to the resistive heating element.

The mouthpiece comprises a heating chamber for receiving an aerosol-forming substrate. The resistive heating element is arranged at least partly around the heating chamber. The primary coil and the secondary coil may be arranged close to a distal end of the heating chamber with respect to a longitudinal axis of the device. The primary coil and the secondary coil may be arranged at a distal end of the heating chamber with respect to a longitudinal axis of the device.

The primary coil and the secondary coil may be helical coils. The primary coil and the secondary coil may be arranged coaxially when the mouthpiece is connected to the main body. Thereby, one of the primary coil and the secondary coil may be inserted into the respective other coil in any rotational position with respect to axis of insertion when attaching the main unit to the mouthpiece. This may additionally allow attaching and detaching of sub-units in an easy-to-operate manner.

The primary coil and the secondary coil may be arranged coaxially around a longitudinal central axis of the device when the mouthpiece is connected to the main body. The primary coil may be arranged coaxially around the secondary coil when the mouthpiece is connected to the main body. The secondary coil may be arranged coaxially around the primary coil when the mouthpiece is connected to the main body.

The secondary coil may be arranged at least partly around the primary coil when the mouthpiece is connected to the main body. The secondary coil may be arranged entirely around the primary coil when the mouthpiece is connected to the main body. This may improve efficient inductive power transfer from the primary coil to the secondary coil. The secondary coil may be arranged entirely around the primary coil when the mouthpiece is connected to the main body and both coils may have substantially the same length in perpendicular to the diameter of a winding. This may additionally improve efficient inductive power transfer from the primary coil to the secondary coil.

The primary coil may be arranged at least partly around the secondary coil when the mouthpiece is connected to the main body. The primary coil may be arranged entirely around the secondary coil when the mouthpiece is connected to the main body. This may improve efficient inductive power transfer from the primary coil to the secondary coil. The primary coil may be arranged entirely around the secondary coil when the mouthpiece is connected to the main body and both coils may have substantially the same length in perpendicular to the diameter of a winding. This may additionally improve efficient inductive power transfer from the primary coil to the secondary coil.

The aerosol-generating device may comprise a temperature sensor. The temperature sensor may be operably coupled to control electronics of the aerosol-generating device to control the temperature of the one or more heating elements. The temperature sensor may be positioned in any suitable location. For example, the temperature sensor may be configured to monitor the temperature of the aerosol-forming substrate being heated. The sensor may transmit signals regarding the sensed temperature to the control electronics, which may adjust power or frequency supplied to the primary coil to achieve a suitable temperature at the sensor. The temperature sensor may comprise a thermocouple.

The temperature sensor may be comprised in the main body. The primary coil may be arranged coaxially around the temperature sensor. The temperature sensor may be located close to a proximal end of the primary coil with respect to a longitudinal axis of the device. The temperature sensor may be located at a proximal end of the primary coil with respect to a longitudinal axis of the device.

In some embodiments, the aerosol-forming substrate is heated to a temperature in a range from about <NUM> to about <NUM>, preferably from about <NUM> to about <NUM>.

The aerosol-generating device may be a hand-held device.

The aerosol-generating device may be a heat-not-burn device. A heat-not-burn device heats the aerosol-forming substrate without combusting it. A heat-not-burn device heats the aerosol-forming substrate to temperatures below its combustion temperature.

The mouthpiece may be detachably connectable to the main body by means of a tight fit connection, a magnetic connection, a screw connection, or a bayonet lock.

The invention further relates to an aerosol-generating system as defined in claim <NUM>. The aerosol-forming substrate may comprise one or both of cast leaf and reconstituted tobacco. The aerosol-forming substrate may comprise a gel.

The invention further relates to a mouthpiece as described herein for use with a main body as described herein. The invention further relates to a main body as described herein for use with a mouthpiece as described herein.

The invention further relates to a method for forming an aerosol in an aerosol-generating device as defined in claim <NUM>.

The aerosol-generating device may comprise one or more heating elements. One or both of the primary coil and the secondary coil may function as a resistive heating element in addition to their function as an active coil or a passive coil in the inductive system. The functioning of a coil as a resistive heating element may be determined by the intrinsic electric resistance of a coil. For example, a greater intrinsic resistance of a coil may lead to more heat generated in the coil.

The secondary coil and the resistive heating element provided in the mouthpiece may be one and the same component. In such embodiments, the secondary coil is configured such that, by its intrinsic resistance, it functions as a resistive heating element when electric power is inductively transferred from the primary coil to the secondary coil.

The resistive heating element provided in the mouthpiece may be an additional component in wired connection to the secondary coil.

The resistive heating element may be formed from one or more resistive heating tracks. The resistive heating tracks may be provided on a flexible substrate. The resistive heating tracks may be printed on the flexible substrate, for example using metallic inks. The resistive heating tracks may act as an electrically resistive heater. The flexible substrate may be electrically insulating. The flexible substrate may be a flexible dielectric substrate. The flexible substrate may comprise polyimide. An example of a suitable material is a polyimide film, such as Kapton®.

In all of the aspects of the disclosure, the heating element may comprise an electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required.

As described, in any of the aspects of the disclosure, the heating element may be part of an aerosol-generating device. The aerosol-generating device may comprise an internal heating element or an external heating element, or both internal and external heating elements, where "internal" and "external" refer to the aerosol-forming substrate. An internal heating element may take any suitable form. For example, an internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heating element may be one or more heating needles or rods that run through the center of the aerosol-forming substrate. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or a heating plate. Optionally, the internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as ceramic material, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heating elements during operation.

An external heating element may take any suitable form. For example, an external heating element may take the form of one or more flexible heating foils on a dielectric substrate, such as polyimide. The flexible heating foils can be shaped to conform to the perimeter of the substrate receiving cavity. Alternatively, an external heating element may take the form of a metallic grid or grids, a flexible printed circuit board, a molded interconnect device (MID), ceramic heater, flexible carbon fibre heater or may be formed using a coating technique, such as plasma vapour deposition, on a suitable shaped substrate. An external heating element may also be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating materials. An external heating element formed in this manner may be used to both heat and monitor the temperature of the external heating element during operation.

The heating element advantageously heats the aerosol-forming substrate by means of conduction. The heating element may be at least partially in contact with the substrate, or the carrier on which the substrate is deposited. Alternatively, the heat from either an internal or external heating element may be conducted to the substrate by means of a heat conductive element.

During operation, the aerosol-forming substrate may be completely contained within the aerosol-generating device. In that case, a user may puff on a mouthpiece of the aerosol-generating device. Alternatively, during operation a smoking article containing the aerosol-forming substrate may be partially contained within the aerosol-generating device. In that case, the user may puff directly on the smoking article.

As used herein, the term 'aerosol-forming substrate' refers to a substrate capable of releasing volatile compounds that can form an aerosol. The volatile compounds may be released by heating or combusting the aerosol-forming substrate. As an alternative to heating or combustion, in some cases, volatile compounds may be released by a chemical reaction or by a mechanical stimulus, such as ultrasound. An aerosol-forming substrate may be part of an aerosol-generating article.

Preferably, the aerosol-forming substrate comprises plant material and an aerosol former. Preferably, the plant material is a plant material comprising an alkaloid, more preferably a plant material comprising nicotine, and more preferably a tobacco-containing material.

Preferably, the aerosol-forming substrate comprises at least <NUM> percent of plant material, more preferably at least <NUM> percent of plant material by weight on a dry weight basis. Preferably, the aerosol-forming substrate comprises less than <NUM> percent of plant material by weight on a dry weight basis, such as from <NUM> to <NUM> percent of plant material by weight on a dry weight basis.

Preferably, the aerosol-forming substrate comprises at least <NUM> percent of aerosol former, more preferably at least <NUM> percent of aerosol former by weight on a dry weight basis. Preferably, the aerosol-forming substrate comprises less than <NUM> percent of aerosol former by weight on a dry weight basis, such as from <NUM> to <NUM> percent of aerosol former by weight on a dry weight basis.

In some particularly preferred embodiments, the aerosol-forming substrate comprises plant material and an aerosol former, wherein the substrate has an aerosol former content of between <NUM>% and <NUM>% by weight on a dry weight basis. The plant material is preferably a plant material comprising an alkaloid, more preferably a plant material comprising nicotine, and more preferably a tobacco-containing material. Alkaloids are a class of naturally occurring nitrogen-containing organic compounds. Alkaloids are found mostly in plants, but are also found in bacteria, fungi and animals. Examples of alkaloids include, but are not limited to, caffeine, nicotine, theobromine, atropine and tubocurarine. A preferred alkaloid is nicotine, which may be found in tobacco.

An aerosol-forming substrate may comprise nicotine. An aerosol-forming substrate may comprise tobacco, for example may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. In preferred embodiments an aerosol-forming substrate may comprise homogenised tobacco material, for example cast leaf tobacco. According to the invention, the aerosol-forming substrate is solid, wherein the aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former. Examples of suitable aerosol formers are glycerine and propylene glycol.

The term "cast leaf" is used herein to refer to a sheet product made by a casting process that is based on casting a slurry comprising plant particles (for example, clove particles, or tobacco particles and clove particles in a mixture) and a binder (for example, guar gum) onto a supportive surface, such as a belt conveyor, drying the slurry and removing the dried sheet from the supportive surface. An example of the casting or cast leaf process is described in, for example, <CIT> for making cast leaf tobacco. In a cast leaf process, particulate plant materials are mixed with a liquid component, typically water, to form a slurry. Other added components in the slurry may include fibres, a binder and an aerosol former. The particulate plant materials may be agglomerated in the presence of the binder. The slurry is cast onto a supportive surface and dried to form a sheet of homogenised plant material.

As used herein, the term 'aerosol-generating article' refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. An aerosol-generating article may be disposable.

As used herein, the term 'aerosol-generating device' refers to a device that interacts with an aerosol-forming substrate to generate an aerosol. An aerosol-generating device may interact with one or both of an aerosol-generating article comprising an aerosol-forming substrate, and a cartridge comprising an aerosol-forming substrate. In some examples, the aerosol-generating device may heat the aerosol-forming substrate to facilitate release of volatile compounds from the substrate. An electrically operated aerosol-generating device may comprise an atomiser, such as an electric heater, to heat the aerosol-forming substrate to form an aerosol.

As used herein, the term 'aerosol-generating system' refers to the combination of an aerosol-generating device with an aerosol-forming substrate. When the aerosol-forming substrate forms part of an aerosol-generating article, the aerosol-generating system refers to the combination of the aerosol-generating device with the aerosol-generating article. In the aerosol-generating system, the aerosol-forming substrate and the aerosol-generating device cooperate to generate an aerosol.

The aerosol-forming substrate may comprise a gel. The gel may be tobacco-free. The gel may comprise nicotine or a tobacco product or another target compound for delivery to a user. The nicotine may be included in the gel with an aerosol-former. Additional tobacco or non-tobacco volatile flavour compounds, to be released upon heating, may be comprised.

The gel may be immobilized at room temperature. "Immobilized" in this context means that the gel has a stable size and shape and does not flow. Room temperature in this context means <NUM> degrees Celsius. The gel may comprise an aerosol-former as described herein.

The gel may comprise a gelling agent. Preferably, the gel comprises agar or agarose or sodium alginate. The gel may comprise Gellan gum. The gel may comprise a mixture of materials. The gel may comprise water.

The gel may comprise a thermoreversible gel. This means that the gel will become fluid when heated to a melting temperature and will set into a gel again at a gelation temperature. The gelation temperature is preferably at or above room temperature and atmospheric pressure. Atmospheric pressure means a pressure of <NUM> atmosphere. The melting temperature is preferably higher than the gelation temperature. Preferably the melting temperature of the gel is above <NUM> degrees Celsius, or <NUM> degrees Celsius, or <NUM> degrees Celsius, and more preferably above <NUM> degrees Celsius. The melting temperature in this context means the temperature at which the gel is no longer immobilized and begins to flow.

The gel may be provided as a single block or may be provided as a plurality of gel elements, for example beads or capsules.

When agar is used as the gelling agent, the gel preferably comprises between <NUM> and <NUM>% by weight (and more preferably between <NUM> and1% by weight) agar. The gel may further comprise between <NUM> and <NUM>% by weight nicotine. The gel may further comprise between <NUM>% and <NUM>% by weight (and more preferably between <NUM> and <NUM>% by weight) glycerin. A remainder of the gel may comprise water and any flavourings.

When Gellan gum is used as the gelling agent, the gel preferably comprises between <NUM> and <NUM>% by weight Gellan gum. The gel may further comprise between <NUM> and <NUM>% by weight nicotine. The gel may further comprise between <NUM>% and <NUM>% by weight glycerine. A remainder of the gel may comprise water and any flavourings.

In one embodiment, the gel comprises <NUM>% by weight nicotine, <NUM>% by weight glycerol, <NUM>% by weight water and <NUM> % by weight agar. In another embodiment, the gel comprises <NUM>% by weight glycerol, <NUM>% by weight water, <NUM>% by weight tobacco and <NUM>% by weight agar.

As used herein, the term 'longitudinal' is used to describe the direction along the main axis of the aerosol-generating device, and the term 'transverse' is used to describe the direction perpendicular to the longitudinal direction.

In certain embodiments, the longitudinal axis of the heating chamber is parallel with the longitudinal axis of the aerosol-generating device. For example, where the open end of the chamber is positioned at the proximal end of the aerosol-generating device. In other embodiments, the longitudinal axis of the heating chamber is at an angle to the longitudinal axis of the aerosol-generating device, for example transverse to the longitudinal axis of the aerosol-generating device. For example, where the open end of the heating chamber is positioned along one side of the aerosol-generating device such that an aerosol-generating article may be inserted into the heating chamber in direction which is perpendicular to the longitudinal axis of the aerosol-generating device.

As used herein, the term 'proximal' refers to a user end, or mouth end of the aerosol-generating-device, and the term 'distal' refers to the end opposite to the proximal end. When referring to the heating chamber or the inductor coil, the term 'proximal' refers to the region closest to the open end of the heating chamber and the term 'distal' refers to the region closest to the closed end. The ends of the aerosol-generating device or the heating chamber may also be referred to in relation to the direction in which air flows through the aerosol-generating device. The proximal end may be referred to as the 'downstream' end and the distal end referred to as the 'upstream' end.

As used herein, the term 'length' refers to the major dimension in a longitudinal direction of the heating chamber, of an aerosol-generating device, of an aerosol-generating article, or of a component of the aerosol-generating device, or of the aerosol-generating article.

As used herein, the term 'width' refers to the major dimension in a transverse direction, of the heating chamber, of an aerosol-generating device, of an aerosol-generating article, or of a component of the aerosol-generating device, or of the aerosol-generating article, at a particular location along its length. The term 'thickness' refers to the dimension in a transverse direction perpendicular to the width.

<FIG> and <FIG> show cross-sections of an aerosol-generating device in side view. The aerosol-generating device of <FIG> and <FIG> is oriented such that the mouth-end side of the device is at the right-hand side of the Figures.

<FIG> shows the aerosol-generating device in a disassembled configuration. The aerosol-generating device comprises a main body <NUM>. The main body <NUM> comprises a primary coil <NUM> and a power supply <NUM>. The main body <NUM> further comprises a temperature sensor <NUM>. The main body <NUM> further comprises control electronics <NUM> in wired connection to both of the primary coil <NUM>, the power supply14, and the temperature sensor <NUM>. The control electronics <NUM> controls operation of the aerosol-generating device.

The primary coil <NUM> is arranged coaxially around the temperature sensor <NUM>. The temperature sensor <NUM> is located at a proximal end of the primary coil <NUM> with respect to a longitudinal axis of the aerosol-generating device.

The aerosol-generating device further comprises a mouthpiece <NUM>. The mouthpiece <NUM> comprises a secondary coil <NUM> and a resistive heating element <NUM>. The resistive heating element <NUM> comprise electrically conductive tracks on a flexible insulating substrate. The electrically conductive tracks are in wired connection to the secondary coil <NUM>. The mouthpiece <NUM> further comprises a heating chamber <NUM>. The resistive heating element <NUM> coaxially surrounds the heating chamber <NUM>. The heating chamber <NUM> is configured to receive a cylindrical aerosol-generating article <NUM> comprising an aerosol-forming substrate.

The mouthpiece <NUM> is detachably connectable to the main body <NUM>. In <FIG>, the detached configuration is shown. In this configuration, the primary coil <NUM> and the secondary coil <NUM> are not inductively coupled.

<FIG> shows the aerosol-generating device of <FIG> in an assembled configuration. In <FIG>, the mouthpiece <NUM> is connected to the main body <NUM>. In this configuration, the secondary coil <NUM> coaxially surrounds the primary coil <NUM> such that the primary coil <NUM> and the secondary coil <NUM> are inductively coupled. The primary coil <NUM> and the secondary coil <NUM> are arranged at a distal end of the heating chamber <NUM> with respect to a longitudinal axis of the aerosol-generating device. As shown in <FIG>, the primary coil <NUM> and the secondary coil <NUM> are arranged coaxially around a longitudinal central axis of the aerosol-generating device when the mouthpiece <NUM> is connected to the main body <NUM>.

During use, the power supply <NUM> provides electric power to the primary coil <NUM> under control of the control electronics <NUM>. Electric power is thus transferred from the primary coil <NUM> to the secondary coil <NUM> via inductive coupling. The electric power transferred from the primary coil <NUM> to the secondary coil <NUM> via inductive coupling is supplied from the secondary coil <NUM> to the resistive heating element <NUM> by a wired connection and is used to heat the resistive heating element <NUM>. The resistive heating element <NUM> heats the aerosol-generating article <NUM> located within the heating chamber <NUM>.

The control electronics <NUM> may be configured to supply an alternating current to the primary coil <NUM>. An alternating current may be induced in the secondary coil <NUM>. The mouthpiece <NUM> may comprise a rectifier arranged in electric connection between the secondary coil <NUM> and the resistive heating element <NUM> to supply direct current to the resistive heating element <NUM>.

<FIG> and <FIG> show cross-sections of an aerosol-generating device in side view. The aerosol-generating device of <FIG> and <FIG> is oriented such that the mouth-end side of the device is at the right-hand side of the Figures. <FIG> shows the aerosol-generating device in a disassembled configuration. <FIG> shows the aerosol-generating device of <FIG> in an assembled configuration. In the embodiment of <FIG> and <FIG>, the same reference numerals are used for likewise features as in the embodiment of <FIG> and <FIG>.

In difference to the embodiment of <FIG> and <FIG>, each of the primary coil <NUM> and the secondary coil <NUM> of the embodiment of <FIG> and <FIG> is designed with an intrinsic resistance required for resistive heating. Both the primary coil <NUM> and the secondary coil <NUM> are thereby configured to perform an additional resistive heating function in addition to the inductive coupling function. The aerosol-generating article <NUM> comprises a recess for insertion of the primary coil <NUM> and the temperature sensor <NUM> into the recess. The primary coil <NUM> transfers electric power to the secondary coil <NUM> by means of inductive coupling. Additionally, the primary coil <NUM> functions as a resistive heating element to internally heat the aerosol-generating article <NUM> when the primary coil <NUM> is inserted into the recess of the aerosol-generating article <NUM> as shown in <FIG>.

The secondary coil <NUM> receives electric power from the primary coil <NUM> by means of inductive coupling. Additionally, the secondary coil <NUM> functions as a resistive heating element to externally heat the aerosol-generating article <NUM> when the aerosol-generating article <NUM> is inserted into the heating chamber <NUM> as shown in <FIG>.

<FIG> shows a diagram of an electric circuit of an aerosol-generating device. There is no wired connection between the main body <NUM> and the mouthpiece <NUM>. Only the main body <NUM> comprises a power supply <NUM>. The mouthpiece <NUM> does not comprise a power supply.

The primary coil <NUM> is in wired connection to the power supply <NUM>. The primary coil <NUM> and the power supply <NUM> form part of a primary wired circuit housed within the main body <NUM>. The secondary coil <NUM> and the resistive heating element <NUM> form part of a secondary wired circuit housed within the mouthpiece <NUM>. During use, electric power is transferred from the primary coil <NUM> to the secondary coil <NUM> via inductive coupling of the primary coil <NUM> and the secondary coil <NUM>. The electric power transferred to the secondary coil <NUM> via inductive coupling is used for heating the resistive heating element <NUM>.

The resistive heating element <NUM> may be an additional component in wired connection to the secondary coil <NUM>, for example electrically conductive tracks on a flexible insulating substrate wrapped around the heating chamber <NUM> as shown in the embodiment of <FIG> and <FIG>. Alternatively, the secondary coil <NUM> itself may function as a resistive heating element as shown in the embodiment of <FIG> and <FIG>.

Claim 1:
An aerosol-generating device comprising,
a main body (<NUM>) comprising a primary coil (<NUM>) and a power supply (<NUM>); and
a mouthpiece (<NUM>) comprising
a secondary coil (<NUM>),
a resistive heating element (<NUM>), and
a heating chamber (<NUM>) for receiving a solid aerosol-forming substrate,
wherein the resistive heating element (<NUM>) is arranged at least partly around the heating chamber (<NUM>);
wherein the mouthpiece (<NUM>) is detachably connectable to the main body (<NUM>); and
wherein the device is configured such that the primary coil (<NUM>) and the secondary coil (<NUM>) are inductively coupled when the mouthpiece (<NUM>) is connected to the main body (<NUM>).