EP4322778A1

EP4322778A1 - Inductively coupled heater

Info

Publication number: EP4322778A1
Application number: EP22721063.0A
Authority: EP
Inventors: Angelo D'ONOFRIO; Benjamin Luke MAZUR; Archer Guy Clift ROWBERRY
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2021-04-12
Filing date: 2022-04-07
Publication date: 2024-02-21
Also published as: CN117082990A; JP2024517386A; WO2022218791A1; KR20230157403A; BR112023016609A2; IL307254A

Abstract

The invention relates to an aerosol-generating device comprising a main body (10) and a mouthpiece (20). The main body comprises a primary coil (12) and a power supply (14). The mouthpiece comprises a secondary coil (22), a heating chamber (26) for receiving an aerosol-forming substrate (28), and a resistive heating element (24) arranged at least partly around the heating chamber. The mouthpiece is detachably connectable to the main body. The aerosol generating device is configured such that the primary coil and the secondary coil are inductively coupled when the mouthpiece is connected to the main body. The invention further relates to an aerosol-generating system comprising the aerosol-generating device and an aerosol-generating article, and to a method for forming an aerosol in an aerosol-generating device.

Description

INDUCTIVELY COUPLED HEATER

The present disclosure relates to an aerosol-generating device. The present disclosure further relates to an aerosol-generating system comprising an aerosol-generating device and an aerosol-generating article. The present disclosure further relates to a method for forming an aerosol in an aerosol-generating device.

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 non- conducting 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.

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. The aerosol-generating device may comprise a main body comprising a primary coil and a power supply. The aerosol-generating device may comprise a mouthpiece comprising a secondary coil and a heating element, preferably a resistive heating element. The mouthpiece may be detachably connectable to the main body. The aerosol-generating device may be configured such that the primary coil and the secondary coil are inductively coupled when the mouthpiece is connected to the main body.

According to an embodiment of the invention there is provided an aerosol-generating device comprising a main body. The main body comprises a primary coil and a power supply. The aerosol-generating device further comprises a mouthpiece. The mouthpiece comprises a secondary coil and a resistive heating element. The mouthpiece is detachably connectable to the main body. The aerosol-generating device is configured such that the primary coil and the secondary coil are inductively coupled when the mouthpiece is connected to the main body.

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 ‘Φ_active ’ equals the flux in the passive coil ‘Φ_passive’. This is shown in equation (1 ): Φ_active = Φ_passive (1 )

The magnetic field strength ‘ B’ in the active coil is given in equation (2):

(2)

‘μ ₀’ is the magnetic constant, ‘l’ is the electric current, ‘N’ is the number of turns of the coil, and ‘l’ is the length of the coil. The magnetic flux in the active coil can then be written using

‘Φ_active = 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’:

(3)

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:

(4)

Then it can be stated simply that the induced emf ‘ε’ in the passive coil is equal to:

(5)

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. 2, 3, 4, and 5.

Exemplary dimensions of the two coils are a radius ‘R’ of a turn of 5 millimeters of the active coil, a radius of a turn of 4 millimeters of the passive coil arranged coaxially within the active coil, 15 windings ‘N’ for each coil, and a length ‘l’ of 10 millimeters of both coils. Using these dimensions, and further assuming a linear efficiency factor ‘η’ of 0.85, the relationship between the emf in the passive coil and the rate of change of the active current can be calculated:

Using equation (7) 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 4 watts. With a typical peak-to-peak current of, for example, about 6 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 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:

(8)

The device will have to compensate for the leakage inductance losses in the passive side. Using equation (8), is calculated to be close to 6·10⁷ 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 50% at the desired operating power of 4 watts.

(9)

If a parallel compensatory inductor ‘L_comp’ were to be introduced across the load, it could be calibrated to cancel the effects of the leakage inductance. Adding a 200 nanohenry inductor, the efficiency in the passive side of the coil at the 4 watts operating point is about 96%. The system frequency does need to be higher in order to reach the same transferred power, with the simple circuit operating at 20 kHz and the compensated circuit at 57 kHz. It may thus be desirable to construct the device with a compensatory inductor on 200 nanohenry and operate it at a 57 kHz 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 4 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 0.05 millimeter and 3 millimeters, preferably between 0.1 millimeter and 1 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 5 and 25 windings, preferably between 10 and 20 windings, more preferably between 13 and 17 windings, most preferably 15 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 5 windings, or by less than 4 windings, or by less than 3 windings, or by less than 2 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 5 and 25 windings, preferably between 10 and 20 windings, more preferably between 13 and 17 windings, most preferably 15 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 1 and 30 millimeters, preferably between 5 and 20 millimeters, more preferably between 8 and 12 millimeters, most preferably about 10 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 1 and 30 millimeters, preferably between 5 and 20 millimeters, more preferably between 8 and 12 millimeters, most preferably about 10 millimeters.

Either one of the primary coil and the secondary coil may have a diameter of a winding of between 1 and 30 millimeters, preferably between 5 and 15 millimeters, more preferably between 8 and 10 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 10 millimeters and the diameter of a winding of the secondary coil may be about 8 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 10 millimeters, the diameter of a winding of the secondary coil is about 8 millimeters, and the primary coil and the secondary coil each have 15 windings and each have a length in a direction perpendicular to the diameter of a winding of about 10 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 10 millimeters and the diameter of a winding of the primary coil may be about 8 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 10 millimeters, the diameter of a winding of the primary coil is about 8 millimeters, and the primary coil and the secondary coil each have 15 windings and each have a length in a direction perpendicular to the diameter of a winding of about 10 millimeters.

The aerosol-generating device may be configured to operate the primary coil with an alternating current at an operating frequency of between 1 kHz and 50 kHz, preferably between 10 kHz and 30 kHz, more preferably between 15 kHz and 25 kHz, most preferably about 20 kHz. 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 10 to 5000 nanohenry inductor, preferably 100 to 300 nanohenry inductor, more preferably a 200 nanohenry inductor.

The aerosol-generating device may comprise a 200 nanohenry compensatory inductor and may be configured to operate the primary coil at an alternating current with an operating frequency of between 1 kHz and 100 kHz, preferably between 47 kHz and 67 kHz, more preferably between 55 kHz and 60 kHz, most preferably about 57 kHz.

The power supply may provide a peak-to-peak AC of about 6 amperes and the aerosol- generating device may be configured to supply about 4 Watts to the resistive heating element.

The mouthpiece may comprise a heating chamber for receiving an aerosol-forming substrate. The resistive heating element may be 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 230 °C to about 400 °C, preferably from about 250 °C to about 350 °C.

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, comprising the aerosol- generating device as described herein and an aerosol-forming substrate. The aerosol-forming substrate may be part of an aerosol-generating article. The aerosol-forming substrate, or the aerosol-generating article, may be configured to be at least partly inserted into a heating chamber of the aerosol-generating device.

The aerosol-forming substrate may be any kind of aerosol-forming substrate as described herein. The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosol-forming substrate comprises one or both of cast leaf and reconstituted tobacco. The aerosol-forming substrate comprises 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. The method comprises generating an alternating electric current in a primary coil being housed within a main body of the aerosol-generating device. The method comprises inducing, by an alternating field produced by the alternating current in the primary coil, an electric current in a secondary coil being inductively coupled to the primary coil and being housed within a mouthpiece of the aerosol-generating device, the mouthpiece being detachably connected to the main body. The method comprises resistively heating, by means of the electric current induced in the secondary coil, a resistive heating element in wired connection to the secondary coil. The method comprises generating an aerosol from an aerosol-forming substrate in thermal contact with the resistive heating element.

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. The aerosol-forming substrate may be solid or liquid or may comprise both solid and liquid components. 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 70 percent of plant material, more preferably at least 90 percent of plant material by weight on a dry weight basis. Preferably, the aerosol-forming substrate comprises less than 95 percent of plant material by weight on a dry weight basis, such as from 90 to 95 percent of plant material by weight on a dry weight basis.

Preferably, the aerosol-forming substrate comprises at least 5 percent of aerosol former, more preferably at least 10 percent of aerosol former by weight on a dry weight basis. Preferably, the aerosol-forming substrate comprises less than 30 percent of aerosol former by weight on a dry weight basis, such as from 5 to 30 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 5% and 30% 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. 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, US-A-5,724,998 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 25 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 1 atmosphere. The melting temperature is preferably higher than the gelation temperature. Preferably the melting temperature of the gel is above 50 degrees Celsius, or 60 degrees Celsius, or 70 degrees Celsius, and more preferably above 80 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 0.5 and 5% by weight (and more preferably between 0.8 and1% by weight) agar. The gel may further comprise between 0.1 and 2% by weight nicotine. The gel may further comprise between 30% and 90% by weight (and more preferably between 70 and 90% 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 0.5 and 5% by weight Gellan gum. The gel may further comprise between 0.1 and 2% by weight nicotine. The gel may further comprise between 30% and 99.4% by weight glycerine. A remainder of the gel may comprise water and any flavourings.

In one embodiment, the gel comprises 2% by weight nicotine, 70% by weight glycerol, 27% by weight water and 1 % by weight agar. In another embodiment, the gel comprises 65% by weight glycerol, 20% by weight water, 14.3% by weight tobacco and 0.7% 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. Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example A: An aerosol-generating device comprising, a main body comprising a primary coil and a power supply; and a mouthpiece comprising a secondary coil and a resistive heating element; wherein the mouthpiece is detachably connectable to the main body; and wherein the device is configured such that the primary coil and the secondary coil are inductively coupled when the mouthpiece is connected to the main body.

Example B: The aerosol-generating device according to Example A, wherein the primary coil and the power supply form part of a primary wired circuit housed within the main body, and wherein the secondary coil and the resistive heating element form part of a secondary wired circuit housed within the mouthpiece.

Example C: The aerosol-generating device according to Example A or Example B, wherein the primary coil is in wired connection to the power supply, and wherein the secondary coil is in wired connection to the resistive heating element.

Example D: The aerosol-generating device according to any of the preceding examples, wherein only the main body comprises a power supply.

Example E: The aerosol-generating device according to any of the preceding examples, wherein there is no wired connection between the main body and the mouthpiece.

Example F: The aerosol-generating device according to any of the preceding examples, wherein the mouthpiece comprises a heating chamber for receiving an aerosol- forming substrate.

Example G: The aerosol-generating device according to Example F, wherein the resistive heating element is arranged at least partly around the heating chamber.

Example FI: The aerosol-generating device according to Example F or Example G, wherein the primary coil and the secondary coil are arranged at a distal end of the heating chamber with respect to a longitudinal axis of the device.

Example I: The aerosol-generating device according to any of the preceding examples, wherein the primary coil and the secondary coil are arranged coaxially when the mouthpiece is connected to the main body.

Example J: The aerosol-generating device according to Example I, wherein the primary coil and the secondary coil are arranged coaxially around a longitudinal central axis of the device when the mouthpiece is connected to the main body. Example K: The aerosol-generating device according to any of the preceding examples, wherein the secondary coil is arranged at least partly around the primary coil when the mouthpiece is connected to the main body.

Example L: The aerosol-generating device according to any of the preceding examples, wherein the device is 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.

Example M: The aerosol-generating device according to Example L, wherein the device is 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.

Example N: The aerosol-generating device according to any of the preceding examples, wherein the device is configured to supply an alternating current induced in the secondary coil to the resistive heating element.

Example O: The aerosol-generating device according to Example N, wherein the mouthpiece comprises a rectifier arranged in electric connection between the secondary coil and the resistive heating element to supply direct current to the resistive heating element.

Example P: The aerosol-generating device according to any of the preceding examples, wherein the primary coil and the secondary coil are helical coils, preferably, wherein both coils have the same number of turns.

Example Q: The aerosol-generating device according to any of the preceding examples, comprising a temperature sensor.

Example R: The aerosol-generating device according to Example Q, wherein the temperature sensor comprises a thermocouple.

Example S: The aerosol-generating device according to Example Q or Example R, wherein the primary coil is arranged coaxially around the temperature sensor.

Example T: The aerosol-generating device according to any of Example Q to Example S, wherein the temperature sensor is located at a proximal end of the primary coil with respect to a longitudinal axis of the device.

Example U: The aerosol-generating device according to any of the preceding examples, comprising one or both of a half-bridge driver and a half-bridge.

Example V: The aerosol-generating device according to any of the preceding examples, comprising a LC filter.

Example W: The aerosol-generating device according to any of the preceding examples, wherein the aerosol-generating device is a hand-held device.

Example X: The aerosol-generating device according to any of the preceding examples, wherein the aerosol-generating device is a heat-not-burn device. Example Y: An aerosol-generating system, comprising the aerosol-generating device according to any of the preceding examples and an aerosol-generating article comprising the aerosol-forming substrate, wherein the aerosol-generating article is configured to be at least partly inserted into a heating chamber of the aerosol-generating device.

Example Z: The aerosol-generating system according to Example Y, wherein the aerosol-forming substrate is a solid aerosol-forming substrate.

Example ZA: The aerosol-generating system according to Example Z, wherein the aerosol-forming substrate comprises one or both of cast leaf and reconstituted tobacco.

Example ZB: A method for forming an aerosol in an aerosol-generating device, comprising steps of generating an alternating electric current in a primary coil being housed within a main body of the aerosol-generating device; inducing, by an alternating field produced by the alternating current in the primary coil, an electric current in a secondary coil being inductively coupled to the primary coil and being housed within a mouthpiece of the aerosol-generating device, the mouthpiece being detachably connected to the main body; resistively heating, by means of the electric current induced in the secondary coil, a resistive heating element in wired connection to the secondary coil; and generating an aerosol from an aerosol-forming substrate in thermal contact with the resistive heating element.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows an aerosol-generating device in disassembled configuration;

Fig. 2 shows an aerosol-generating device in assembled configuration;

Fig. 3 shows an aerosol-generating device in disassembled configuration;

Fig. 4 shows the aerosol-generating device in assembled configuration; and

Fig. 5 shows a diagram of an electric circuit.

Figures 1 and 2 show cross-sections of an aerosol-generating device in side view. The aerosol-generating device of Figures 1 and 2 is oriented such that the mouth-end side of the device is at the right-hand side of the Figures.

Figure 1 shows the aerosol-generating device in a disassembled configuration. The aerosol-generating device comprises a main body 10. The main body 10 comprises a primary coil 12 and a power supply 14. The main body 10 further comprises a temperature sensor 16. The main body 10 further comprises control electronics 18 in wired connection to both of the primary coil 12, the power supply14, and the temperature sensor 16. The control electronics 18 controls operation of the aerosol-generating device.

The primary coil 12 is arranged coaxially around the temperature sensor 16. The temperature sensor 16 is located at a proximal end of the primary coil 12 with respect to a longitudinal axis of the aerosol-generating device.

The aerosol-generating device further comprises a mouthpiece 20. The mouthpiece 20 comprises a secondary coil 22 and a resistive heating element 24. The resistive heating element 24 comprise electrically conductive tracks on a flexible insulating substrate. The electrically conductive tracks are in wired connection to the secondary coil 22. The mouthpiece 20 further comprises a heating chamber 26. The resistive heating element 24 coaxially surrounds the heating chamber 26. The heating chamber 26 is configured to receive a cylindrical aerosol-generating article 28 comprising an aerosol-forming substrate.

The mouthpiece 20 is detachably connectable to the main body 10. In Fig. 1 , the detached configuration is shown. In this configuration, the primary coil 12 and the secondary coil 22 are not inductively coupled.

Fig. 2 shows the aerosol-generating device of Fig. 1 in an assembled configuration. In Fig. 2, the mouthpiece 20 is connected to the main body 10. In this configuration, the secondary coil 22 coaxially surrounds the primary coil 12 such that the primary coil 12 and the secondary coil 22 are inductively coupled. The primary coil 12 and the secondary coil 22 are arranged at a distal end of the heating chamber 26 with respect to a longitudinal axis of the aerosol- generating device. As shown in Fig. 2, the primary coil 12 and the secondary coil 22 are arranged coaxially around a longitudinal central axis of the aerosol-generating device when the mouthpiece 10 is connected to the main body 20.

During use, the power supply 14 provides electric power to the primary coil 12 under control of the control electronics 18. Electric power is thus transferred from the primary coil 12 to the secondary coil 22 via inductive coupling. The electric power transferred from the primary coil 12 to the secondary coil 22 via inductive coupling is supplied from the secondary coil 22 to the resistive heating element 24 by a wired connection and is used to heat the resistive heating element 24. The resistive heating element 24 heats the aerosol-generating article 28 located within the heating chamber 26.

The control electronics 18 may be configured to supply an alternating current to the primary coil 12. An alternating current may be induced in the secondary coil 22. The mouthpiece 20 may comprise a rectifier arranged in electric connection between the secondary coil 22 and the resistive heating element 24 to supply direct current to the resistive heating element 24.

Figures 3 and 4 show cross-sections of an aerosol-generating device in side view. The aerosol-generating device of Figures 3 and 4 is oriented such that the mouth-end side of the device is at the right-hand side of the Figures. Figure 3 shows the aerosol-generating device in a disassembled configuration. Fig. 4 shows the aerosol-generating device of Fig. 3 in an assembled configuration. In the embodiment of Figs. 3 and 4, the same reference numerals are used for likewise features as in the embodiment of Figs. 1 and 2.

In difference to the embodiment of Figs. 1 and 2, each of the primary coil 12 and the secondary coil 22 of the embodiment of Figs. 3 and 4 is designed with an intrinsic resistance required for resistive heating. Both the primary coil 12 and the secondary coil 22 are thereby configured to perform an additional resistive heating function in addition to the inductive coupling function. The aerosol-generating article 28 comprises a recess for insertion of the primary coil 12 and the temperature sensor 16 into the recess. The primary coil 12 transfers electric power to the secondary coil 22 by means of inductive coupling. Additionally, the primary coil 12 functions as a resistive heating element to internally heat the aerosol-generating article 28 when the primary coil 12 is inserted into the recess of the aerosol-generating article 28 as shown in Fig. 4.

The secondary coil 22 receives electric power from the primary coil 12 by means of inductive coupling. Additionally, the secondary coil 22 functions as a resistive heating element to externally heat the aerosol-generating article 28 when the aerosol-generating article 28 is inserted into the heating chamber 24 as shown in Fig. 4.

Fig. 5 shows a diagram of an electric circuit of an aerosol-generating device. There is no wired connection between the main body 10 and the mouthpiece 20. Only the main body 10 comprises a power supply 14. The mouthpiece 20 does not comprise a power supply.

The primary coil 12 is in wired connection to the power supply 14. The primary coil 12 and the power supply 14 form part of a primary wired circuit housed within the main body 10. The secondary coil 22 and the resistive heating element 24 form part of a secondary wired circuit housed within the mouthpiece 20. During use, electric power is transferred from the primary coil 12 to the secondary coil 22 via inductive coupling of the primary coil 12 and the secondary coil 22. The electric power transferred to the secondary coil 22 via inductive coupling is used for heating the resistive heating element 24.

The resistive heating element 24 may be an additional component in wired connection to the secondary coil 22, for example electrically conductive tracks on a flexible insulating substrate wrapped around the heating chamber 26 as shown in the embodiment of Figs. 1 and 2. Alternatively, the secondary coil 22 itself may function as a resistive heating element as shown in the embodiment of Figs. 3 and 4.

Optionally, an additional resistor 30 may be comprised in the main body 10. If present, the resistor 30 may represent the intrinsic resistance of the primary coil 12 which may function as a resistive heating element as shown in the embodiment of Figs. 3 and 4. Alternatively, the resistor 30 may be an additional component in wired connection to the primary coil 12, for example, an additional resistive heating element.

Claims

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

2. The aerosol-generating device according to claim 1 , wherein there is no wired connection between the main body and the mouthpiece.

3. The aerosol-generating device according to any of the preceding claims, wherein the primary coil and the secondary coil are arranged at a distal end of the heating chamber with respect to a longitudinal axis of the device.

4. The aerosol-generating device according to any of the preceding claims, wherein the primary coil and the secondary coil are arranged coaxially around a longitudinal central axis of the device when the mouthpiece is connected to the main body.

5. The aerosol-generating device according to any of the preceding claims, wherein the secondary coil is arranged at least partly around the primary coil when the mouthpiece is connected to the main body.

6. The aerosol-generating device according to any of the preceding claims, wherein the device is 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.

7. The aerosol-generating device according to claim 6, wherein the device is 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.

8. The aerosol-generating device according to any of the preceding claims, wherein the device is configured to supply an alternating current induced in the secondary coil to the resistive heating element.

9. The aerosol-generating device according to claim 8, wherein the mouthpiece comprises a rectifier arranged in electric connection between the secondary coil and the resistive heating element to supply direct current to the resistive heating element.

10. The aerosol-generating device according to any of the preceding claims, wherein the primary coil and the secondary coil are helical coils, preferably, wherein both coils have the same number of turns.

11. The aerosol-generating device according to any of the preceding claims, wherein the aerosol-generating device is a heat-not-burn device.

12. An aerosol-generating system, comprising the aerosol-generating device according to any of the preceding claims and an aerosol-generating article comprising the aerosol-forming substrate, wherein the aerosol-generating article is configured to be at least partly inserted into a heating chamber of the aerosol-generating device.

13. The aerosol-generating system according to claim 12, wherein the aerosol- forming substrate is a solid aerosol-forming substrate.

14. A method for forming an aerosol in an aerosol-generating device, comprising steps of generating an alternating electric current in a primary coil being housed within a main body of the aerosol-generating device; inducing, by an alternating field produced by the alternating current in the primary coil, an electric current in a secondary coil being inductively coupled to the primary coil and being housed within a mouthpiece of the aerosol-generating device, the mouthpiece being detachably connected to the main body and the mouthpiece comprising a heating chamber for receiving an aerosol-forming substrate; resistively heating, by means of the electric current induced in the secondary coil, a resistive heating element in wired connection to the secondary coil, wherein the resistive heating element is arranged at least partly around the heating chamber; and generating an aerosol from an aerosol-forming substrate in thermal contact with the resistive heating element.