An aerosol-generating device having a heater and a heat-conducting element

Abstract

There is provided an aerosol-generating device (110). The aerosol-generating device (110) comprises a tubular heat-conducting element (28) comprising a cylindrical inner surface (22) forming a curved plane, wherein the cylindrical inner surface (22) at least partially defines a chamber (16) for receiving at least a portion of an aerosol-generating article so that an aerosol-generating article received within the chamber (16) directly contacts the cylindrical inner surface (22). The aerosol-generating device (110) also comprises a resistive heating element (133) formed separately from the tubular heat-conducting element (28), and an inductor coil (124). The inductor coil (124) extends around at least a portion of the heat-conducting element (28). The aerosol-generating device (110) also comprises a power supply (42) and control circuitry (40). The power supply (42) and the control circuitry (40) are connected to the resistive heating element (133) and configured to provide an electric current to the resistive heating element (133) so that, in use, the resistive heating element (133) heats the tubular heat-conducting element (22). The power supply (42) and the control circuitry (40) are connected to the inductor coil (124) and configured to provide an alternating electric current to the inductor coil (124) such that, in use, the inductor coil (124) generates an alternating magnetic field.

Description

[0001] AN AEROSOL-GENERATING DEVICE HAVING A HEATER AND A HEAT-CONDUCTING ELEMENT

[0002] The present disclosure relates to an aerosol-generating device for receiving an aerosolgenerating article, and an aerosol-generating system comprising the aerosol-generating device.

[0003] It is known to evolve an aerosol from an aerosol-forming substrate of an aerosol-generating article by the application of heat to the substrate, without burning or combustion of the substrate. The aerosol-generating article may be cylindrical, like a cigarette, and the aerosol-forming substrate may comprise tobacco material. It is known to apply heat to such an aerosol-generating article to heat the aerosol-forming substrate of the article using a heat source that is external to the aerosol-generating article.

[0004] However, an external heat source will tend to heat the aerosol-forming substrate unevenly. The aerosol-forming substrate closest to the heat source will be heated more than the aerosolforming substrate in the centre of the aerosol-generating article, further from the heat source.

[0005] It is also known to heat the aerosol-forming substrate of such an article using a heat source located within the interior of the aerosol-forming substrate. In some aerosol-generating systems the internal heat source is heated inductively using an induction coil positioned externally of the aerosol-generating article and a susceptor material located within a central region of the aerosolgenerating article. Internally heating the aerosol-forming substrate avoids heat having to traverse through a wrapper to reach the aerosol-forming substrate. However, internally heating the aerosol-forming substrate also results in the aerosol-forming substrate being heated in a non- uniform manner, with heating of the substrate being greatest at or closest to the internal heat source and reducing with increasing distance away from the internal heat source into the substrate.

[0006] Non-uniform heating of the aerosol-forming substrate can mean that not all of the available volatile material is released from the aerosol-forming substrate. This is because increasing the level of heat applied to the substrate in order to fully extract the volatile material from the aerosolforming substrate when using either external heating or internal heating of the substrate may result in unintended and undesired burning of the substrate close to the heat source, which can give rise to the generation of undesirable compounds and flavours.

[0007] It is therefore desired to provide an aerosol-generating device that facilitates efficient and uniform heating of an aerosol-forming substrate without requiring a complex heating arrangement.

[0008] According to the present disclosure there is provided an aerosol-generating device. The aerosol-generating device may comprise a tubular heat-conducting element. The tubular heat- conducting element may comprise a cylindrical inner surface forming a curved plane. The cylindrical inner surface may at least partially define a chamber for receiving at least a portion of an aerosol-generating article. An aerosol-generating article received within the chamber may directly contact the cylindrical inner surface. The aerosol-generating device may comprise a resistive heating element. The aerosol-generating device may comprise an inductor coil. The inductor coil may extend around at least a portion of the heat-conducting element. The aerosolgenerating device may comprise a power supply and control circuitry. The power supply and control circuitry may be connected to the resistive heating element. The power supply and control circuitry may be configured to provide an electric current to the resistive heating element so that, in use, the resistive heating element heats the tubular heat-conducting element. The power supply and control circuitry may be connected to the inductor coil. The power supply and the control circuitry may be configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field.

[0009] According to the present disclosure there is also provided an aerosol-generating device. The aerosol-generating device comprises a tubular heat-conducting element comprising a cylindrical inner surface forming a curved plane, wherein the cylindrical inner surface at least partially defines a chamber for receiving at least a portion of an aerosol-generating article so that an aerosol-generating article received within the chamber directly contacts the cylindrical inner surface. The aerosol-generating device also comprises a resistive heating element and an inductor coil. The inductor coil extends around at least a portion of the heat-conducting element. The aerosol-generating device also comprises a power supply and control circuitry. The power supply and control circuitry are connected to the resistive heating element and configured to provide an electric current to the resistive heating element so that, in use, the resistive heating element heats the tubular heat-conducting element. The power supply and control circuitry are connected to the inductor coil and configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field.

[0010] As used herein, the term “aerosol-generating device” is used to describe a device that interacts with an aerosol-forming substrate to generate an aerosol. Preferably, the aerosolgenerating device is a smoking device that interacts with an aerosol-forming substrate to generate an aerosol that is directly inhalable into a user’s lungs thorough the user's mouth.

[0011] As used herein, the term “heat-conducting element” is used to describe an element comprising one or more heat-conducting materials having a bulk thermal conductivity of between about 0.1 Watts per metre Kelvin and about 500 Watts per metre Kelvin, preferably between about 1 Watt per metre Kelvin and about 400 Watts per metre Kelvin, at 23 degrees Celsius and a relative humidity of 50 percent as measured using the modified transient plane source (MTPS) method.

[0012] As used herein, the term “curved plane” is used to describe a curved surface that is uniform and free from grooves, channels, and other discontinuities in the curved surface.

[0013] Advantageously, aerosol-generating devices according to the present disclosure comprise both a resistive heating element and an inductor coil. Advantageously, this arrangement may facilitate both internal and external heating of an aerosol-forming substrate of aerosol-generating article received within the chamber. For example, the resistive heating element may be arranged to generate heat around an exterior of the aerosol-generating article, and the inductor coil may inductively heat a susceptor element positioned inside the aerosol-forming substrate. Advantageously, providing both internal and external heating may facilitate uniform heating of the aerosol-forming substrate.

[0014] Advantageously using a separate inductor coil and resistive heating element to provide inductive heating and resistive heating respectively means that the characteristics, shapes and materials of the inductor coil and the resistive heating element may be individually adapted and optimised to more efficiently heat an aerosol-forming substrate. For example, the inductor coil may be optimised for inductive heating and the resistive heating element may be optimised for resistive heating.

[0015] Advantageously, the tubular heat-conducting element may facilitate a uniform heat transfer from the resistive heating element to the aerosol-generating article. Furthermore, the present inventors have recognised that that an inductor coil may exhibit heat losses in the form of resistive heating of the inductor coil when an alternating electric current flows through the inductor coil during use. Advantageously, the heat-conducting element may facilitate the transfer of resistively generated heat from the inductor coil to the aerosol-generating article received within the chamber.

[0016] Advantageously, the uniform surface formed by the curved plane of the cylindrical inner surface of the tubular heat-conducting element may maximise a contact area between the tubular heat-conducting element and an aerosol-generating article, which may maximise the transfer of heat from the tubular heat-conducting element to the aerosol-generating article. This contrasts with other devices having a chamber for receiving an aerosol-generating article, the chamber defining one or more grooves or channels to define airflow channels along an outer surface of the aerosol-generating article.

[0017] The tubular heat-conducting element may be the resistive heating element. Advantageously, providing a single component that functions as both the tubular heat-conducting element and the resistive heater may simplify the design and construction of the aerosolgenerating device. For example, the tubular heat-conducting element may be formed from a resistively heatable material. In examples in which the tubular heat-conducting element is the resistive heating element, preferably the power supply and the control circuitry are configured to provide the electric current to the tubular heat-conducting element so that, in use, the tubular heat-conducting element is resistively heated.

[0018] The resistive heating element may extend around at least a portion of the tubular heat- conducting element. Advantageously, the resistive heating element extending around at least a portion of the tubular heat-conducting element may facilitate the transfer of heat from the resistive heating element to an aerosol-forming substrate by the tubular heat-conducting element. Advantageously, using the tubular heat-conducting element to transfer heat from the resistive heating element to an aerosol-forming substrate may facilitate more uniform heating of the aerosol-forming substrate. The resistive heating element may surround the tubular heat- conducting element.

[0019] The resistive heating element may be arranged in direct contact with the tubular heat- conducting element. Advantageously, in examples in which the resistive heating element is formed separately from the tubular heat-conducting element, direct contact between the resistive heating element and the tubular heat-conducting element may increase or maximise the transfer of heat from the resistive heating element to the tubular heat-conducting element.

[0020] The resistive heating element may directly contact an outer surface of the tubular heat- conducting element. For example, the resistive heating element may be a resistive heating coil extending around at least a portion of the tubular heat-conducting element.

[0021] The resistive heating element may be at least partially embedded within the tubular heat- conducting element. Advantageously, at least partially embedding the resistive heating element within the tubular heat-conducting element may increase or maximise the transfer of heat from the resistive heating element to the tubular heat-conducting element. The resistive heating element may be a resistive heating coil embedded within the tubular heat-conducting element so that the resistive heating coil extends around at least a portion of the chamber.

[0022] The resistive heating element may be a resistive heating coil extending around at least a portion of the tubular heat-conducting element.

[0023] The inductor coil may be arranged in direct contact with an outer surface of the tubular heat-conducting element. Advantageously, direct contact between the inductor coil and the heat- conducting element may increase or maximise the conduction of resistively generated heat from the inductor coil to the heat-conducting element.

[0024] The inductor coil may be spaced apart from the tubular heat-conducting element so that the inductor coil does not directly contact the tubular heat-conducting element. Advantageously, spacing apart the inductor coil from the tubular heat-conducting element may facilitate the formation of an airflow passage between the inductor coil and the tubular heat-conducting element.

[0025] Preferably, the chamber comprises a first end defining an opening for receiving an aerosolgenerating article and a second end opposite the first end. Preferably, the aerosol-generating device comprises a housing defining at least one air inlet and at least one airflow passage extending between the at least one air inlet and the second end of the chamber, wherein the at least one airflow passage is positioned outside of the chamber.

[0026] Advantageously, positioning the at least one airflow passage outside of the chamber facilitates the cylindrical inner surface of the tubular heat-conducting element forming the curved plane that is uniform and free from grooves, channels, and other discontinuities.

[0027] The at least one air inlet may be positioned adjacent the opening. Preferably, the at least one airflow passage extends between the outer surface of the tubular heat-conducting element and an inner surface of the housing. Advantageously, positioning the at least one airflow passage between the outer surface of the tubular heat-conducting element and the inner surface of the housing may facilitate heating of airflow through the at least one airflow passage by resistively generated heat from at least one of the resistive heating element and the inductor coil. Advantageously, heating of the airflow through the at least one airflow passage may pre-heat the airflow before the airflow reaches an aerosol-generating article received within the chamber. At least a portion of the resistive heating element may be positioned within the at least one airflow passage. At least a portion of the inductor coil may be positioned within the at least one airflow passage.

[0028] The chamber may define a longitudinal direction extending between the first end of the chamber and the second end of the chamber. The at least one air inlet may extend through a sidewall of the housing, wherein at least a portion of the at least one airflow passage extends perpendicular to the longitudinal direction. Advantageously, positioning the at least one air inlet on a sidewall of the housing may remove any risk of a user’s lips accidentally obstructing the at least one air inlet during use of the aerosol-generating article.

[0029] The at least one air inlet may comprise a plurality of air inlets. Advantageously, providing a plurality of air inlets may reduce the risk of a user accidentally obstructing all of the air inlets during use of the aerosol-generating device. Preferably, the air inlets are equidistantly spaced apart from each other. Preferably, the air inlets are distributed symmetrically around a portion of the housing. The plurality of air inlets may comprise at least two, three, four, five, six, seven, eight, nine, or ten air inlets. The plurality of air inlets may comprise fewer than twelve, eleven, ten, nine, eight, seven, six, five, four, or three air inlets. Preferably, the at least one airflow passage comprises a plurality of airflow passages. Preferably, the plurality of airflow passages comprises one airflow passage extending from each of the air inlets and towards the second end of the chamber. The airflow passages extending from the air inlets may combine into a single common airflow passage, wherein the single common airflow passage is in fluid communication with the second end of the chamber.

[0030] Preferably, the chamber has a circular cross-sectional shape. Advantageously, a circular cross-sectional shape may increase or maximise a contact area between the tubular heat- conducting element and an aerosol-generating article.

[0031] Preferably, the curved plane defines the circular cross-sectional shape of the chamber.

[0032] Preferably, the tubular heat-conducting element extends in a longitudinal direction, wherein the curved plane extends in a circumferential direction about the longitudinal direction. Preferably, the tubular heat-conducting element is arranged for insertion of an aerosol-generating article into the chamber along the longitudinal direction.

[0033] Preferably, the circular cross-sectional shape of the chamber has a constant diameter in all directions perpendicular to the longitudinal direction. Advantageously, providing the circular cross-sectional shape of the chamber with a constant diameter in all directions perpendicular to the longitudinal direction may increase or maximise a contact area between the tubular heat- conducting element and an aerosol-generating article.

[0034] Preferably, the circular cross-sectional shape of the chamber has a roundness of at least 0.999. As used herein, the term “roundness” of a shape is the ratio of the radius of the inscribed circle to the radius of the circumscribed circle for the shape. Advantageously, providing the circular cross-sectional shape of the chamber with a roundness of at least 0.999 may increase or maximise a contact area between the tubular heat-conducting element and an aerosol-generating article.

[0035] Preferably, the control circuitry and the power supply are configured to provide a direct current to the resistive heating element for resistively heating the resistive heating element.

[0036] The control circuitry may be configured to provide the direct current to the resistive heating element such that the resistive heating element is heated to at least 80 degrees Celsius. Advantageously, heating the resistive heating element to at least 80 degrees Celsius may ensure that the resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The control circuitry may be configured to provide the direct current to the resistive heating element such that the resistive heating element is heated to no more than 210 degrees Celsius. Advantageously, heating the resistive heating element to no more than 210 degrees Celsius may ensure that the resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0037] The control circuitry may be configured to provide the alternating current to the inductor coil and the direct current to the resistive heating element at different times.

[0038] For example, the control circuitry may be configured to provide the alternating current to the inductor coil and then subsequently the direct current to the resistive heating element. The control circuitry may be configured to provide the alternating current to the inductor coil for a first time period. The control circuitry may be configured to provide the direct current to the resistive heating element for a second time period after the first time period. Advantageously, the aerosolforming substrate may be non-uniform, and heating the aerosol-forming substrate via inductive heating then subsequently by resistive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0039] The control circuitry may be configured to provide the direct current to the resistive heating element and then subsequently the alternating current to the inductor coil. The control circuitry may be configured to provide the direct current to the resistive heating element for a first time period. The control circuitry may be configured to provide the alternating current to the inductor coil for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate via resistive heating then subsequently by inductive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0040] The control circuitry may be configured to detect when the user takes a puff on the system. For example, the control circuitry may be coupled to a pressure sensor, the pressure sensor configured to detect a pressure drop when the user takes a puff on the system. The control circuitry may be configured to supply power to the inductor coil or the resistive heating element, or the inductor coil and the resistive heating element, when the pressure sensor detects a pressure drop when the user takes a puff on the system. For example, the control circuitry may be configured to start the first time period in response to the user taking a puff on the system.

[0041] The control circuitry may comprise a user-activatable trigger. For example, the user- activatable trigger may comprise a button or a switch. The control circuitry may be configured to start the first time period in response to the user-activatable trigger being activated.

[0042] The control circuitry may be configured to end the first time period and start the second time period in response to: a predetermined number of puffs on the system being taken; or a predetermined time from a first puff on the system passing; or the user-activatable trigger being activated; or a combination of any one or more of the above.

[0043] The control circuitry may be configured to provide the alternating current to the inductor coil and the direct current to the resistive heating element in an alternating sequence. Advantageously, it may be beneficial to alternate inductive and resistive heating in order to avoid overheating of any part of the aerosol-forming substrate.

[0044] The control circuitry may be configured to provide the alternating current to the inductor coil and the direct current to the resistive heating element simultaneously. Advantageously, in this way a larger amount of heat energy can be transferred to the aerosol-forming substrate to generate a larger volume of aerosol, without either the susceptor or the resistive heating element reaching a temperature at which any part of the aerosol-generating article might combust. This may be particularly beneficial after start-up of the aerosol-generating system or use of the aerosolgenerating system in a cold environment, for example.

[0045] There are many possible ways to combine the inductive heating of the susceptor and the heating of the resistive heating element. For example, the inductive heating of the susceptor may be controlled to follow a particular profile over the course of a usage session and the resistive heating of the resistive heating element may be controlled to follow a different profile over the course of the usage session. The profiles may be chosen to provide consistent aerosol delivery over the course of the usage session as well as providing heating of substantially all of the aerosol-forming substrate. The control circuitry may be configured to adjust the alternating current provided to the inductor coil to maintain the temperature of the susceptor at a target temperature or to follow a target temperature profile.

[0046] The control circuitry may be configured to adjust the direct current provided to the resistive heating element to maintain the temperature of the resistive heating element at a target temperature or to follow a target temperature profile.

[0047] The control circuitry may be configured to alter a magnitude of the alternating current during operation of the device to adjust an amount of heat generated in the susceptor by the inductor coil as a result of the alternating current.

[0048] The control circuitry may be configured to adjust the frequency of the alternating current during operation of the device to adjust an amount of heat generated in the susceptor by the inductor coil as a result of the alternating current.

[0049] The inductor coil may be a helical coil. In examples in which the resistive heating element comprises a resistive heating coil, the resistive heating coil may be a helical coil. The resistive heating coil and the inductor coil may be co-wound. Advantageously, this may result in a spaceefficient arrangement in which the two separate heating systems may both be positioned in direct contact with the outer surface of the tubular heat-conducting element.

[0050] The resistive heating coil may be wound about a winding axis. The inductor coil may be wound about the same winding axis as the resistive heating coil.

[0051] Preferably, at least one of the control circuitry and the heat-conducting element is configured to prevent inductive coupling between the heat-conducting element and the inductor coil during use.

[0052] As used herein, the term “inductively couple” refers to the heating of a material when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the material. The heating may be caused by magnetic hysteresis losses.

[0053] The control circuitry may be configured to provide the alternating electric current in the form of an alternating current having a frequency selected to reduce or prevent inductive coupling between the heat-conducting element and the inductor coil during use. Preferably, the alternating current is provided at a frequency that reduces or prevents inductive coupling between the inductor coil and the heat-conducting element and increases or maximises inductive coupling between the inductor coil and a susceptor element. The frequency at which inductive coupling occurs will vary depending on the materials, physical properties and configuration of the inductor coil, the heat-conducting element and the susceptor element, such as the inductance of the inductor coil and the magnetic permeability of the material or materials from which each of the heat-conducting element and the susceptor element are formed.

[0054] The inductor coil may extend between a first end and a second end. An electrical resistance between the first end and the second end of the inductor coil may be less than 250 milliohms, preferably less than 150 milliohms, preferably still approximately 100 milliohms. A relatively low electrical resistance may ensure that minimal power is dissipated in the inductor coil as heat. This may be particularly advantageous in embodiments in which the aerosol-generating device also comprises a resistive heating coil.

[0055] The resistive heating coil may extend between a first end and a second end. An electrical resistance between the first end and the second end of the resistive heating coil may be between 100 milliohms and 2000 milliohms, preferably between 150 milliohms and 1500 milliohms, and preferably still between 200 milliohms and 1000 milliohms. Advantageously, a relatively high electrical resistance ensures that maximal power is dissipated in the resistive heating coil as heat, as the resistive heating coil may be configured to resistively heat the aerosol-forming substrate.

[0056] Preferably, the electrical resistance of the resistive heating coil is greater than the electrical resistance of the inductor coil. The electrical resistance of the resistive heating coil may be at least 2 times greater than the electrical resistance of the inductor coil. The electrical resistance of the resistive heating coil may be at least 5 times greater than the electrical resistance of the inductor coil. The electrical resistance of the resistive heating coil may be at least 10 times greater than the electrical resistance of the inductor coil.

[0057] The heat-conducting element may be formed from a material that reduces or prevents inductive coupling between the inductor coil and the heat-conducting element.

[0058] The heat-conducting element may be formed from a non-electrically conductive material. The non-electrically conductive material may comprise at least one of a glass, a ceramic, a silicone, a polymeric material, and a composite material comprising two or more non-electrically conductive materials. A suitable ceramic may comprise at least one of alumina, aluminium nitride, and zirconia. Advantageously alumina, aluminium nitride and zirconia have been found to possess suitable thermal properties to ensure that heat is efficiently transferred to the aerosolforming substrate.

[0059] The term “electrically conductive” is used herein to refer to materials having an electrical conductivity of at least 0.8 x 106Siemens per metre. The terms “non-electrically conductive” and “electrically insulating” are used herein to refer to materials having an electrical conductivity of less than 0.8 x 104Siemens per metre.

[0060] The heat-conducting element may be formed from a non-inductively heatable material. The non-inductively heatable material may comprise any of the non-electrically conductive materials described above. The non-inductively heatable material may comprise an electrically conductive material that exhibits poor or no inductive coupling with the inductor coil. The non-inductively heatable material may comprise a metal. The metal may comprise at least one of aluminium and a paramagnetic steel. The paramagnetic steel may comprise an austenitic steel. The heat- conducting element may be formed from a 316 stainless steel.

[0061] The heat-conducting element has a tubular shape. Preferably, the heat-conducting element has a circular cross-sectional shape. The heat-conducting element may have a cylindrical shape having a constant cross-sectional size along a length of the heat-conducting element. The heat- conducting element may have a cylindrical shape, wherein at least a portion of the cylindrical shape has a tapering cross-sectional size. A tapering cross-sectional size may facilitate the insertion of an aerosol-generating article into the heat-conducting element.

[0062] The heat-conducting element may be formed from a cylindrical wall of a heat-conducting material. The cylindrical wall may have a wall thickness extending in a radial direction. Preferably, the cylindrical wall has a number average thickness in the radial direction of at least 0.5 millimetres, or at least 1 millimetre, or at least 1.5 millimetres, or at least 2 millimetres. Preferably, the cylindrical wall has a number average thickness in a radial direction of less than 5 millimetres, or less than 4 millimetres, or less than 3 millimetres, or less than 2 millimetres.

[0063] In examples in which the tubular heat-conducting element is the resistive heating element, the heat-conducting element may comprise an electrically insulating substrate, for example a substantially tubular electrically insulating substrate, and an electrically resistive track on or within the electrically insulating substrate. The control circuitry may be configured to provide an electric current from the power supply to the electrically resistive track in use.

[0064] Suitable electrically insulating materials may include one or more of: glass, ceramic, anodized metal, coated metal, and Polyimide. The ceramic may comprise mica, Alumina or Zirconia.

[0065] Suitable electrically resistive materials may include one or more of: 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 and metals from the platinum group. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminiumtitanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetai® and iron-manganese-aluminium based alloys. The electrically resistive track may comprise a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or filament.

[0066] The heat-conducting element may comprise a polymeric material and at least one of carbon fibres, carbon nanotubes, graphite, a graphite-derived material, and hexagonal boron nitride dispersed within the polymeric material. The polymeric material may be referred to as a polymeric matrix. The at least one of carbon fibres, carbon nanotubes, graphite, a graphite-derived material, and hexagonal boron nitride may be present as filler particles in the polymeric matrix.

[0067] The polymeric material may be or comprise at least one of polyether ether ketone (PEEK) and a liquid crystal polymer (LCP). The heat-conducting element may comprise the polymeric material in an amount of between 22 percent and 33 percent by weight of the heat-conducting element. The graphite-derived material may comprise at least one of expanded graphite and graphite nanoplatelets. The heat-conducting element may comprise the at least one of carbon fibres, carbon nanotubes, graphite, a graphite-derived material, and hexagonal boron nitride in an amount of between 62 percent and 69 percent by weight of the heat-conducting element.

[0068] The heat-conducting element may further comprise at least one additive dispersed within the polymeric material. The at least one additive may comprise carbon black. The heat-conducting element may comprise the at least one additive in an amount of between 5 percent and 9 percent by weight of the heat-conducting element. Advantageously, such an actively heated heat- conducting element may be easier to manufacture compared to other external heaters. In more detail, the inventors have observed that the thermoplastic properties of the polymeric matrix may allow the composite polymer to be tailored to be conveniently malleable, such that it lends itself to precise and controlled shaping. At the same time, by controlling and adjusting the concentration and distribution of the conductive filler particles dispersed within the polymeric matrix, it is advantageously possible to provide an active heat-conducting element capable of generating enough heat by Joule effect to efficiently heat an aerosol-forming substrate of an aerosol-generating article thermally coupled with the heat-conducting element.

[0069] Without wishing to be bound by theory, the inventors have found that by adjusting the formulation of the polymeric matrix and the degree of dispersion of the conductive filler particles within the polymeric matrix, it is possible to control the conductivity and, as a consequence, the amount of heat generated resistively by the heat-conducting element when a voltage is applied to the heat-conducting element. In particular, by adjusting the relative proportion of conductive filler to polymer within the polymer composite, it may be advantageously possible to ensure that a heat-conducting element made of the polymer composite exhibits highly desirable levels of resistivity. Other parameters, such as the length and cross-sectional surface area of the heat- conducting element may also be adjusted to fine-tune the resistive behaviour of the heat- conducting element as a whole.

[0070] Preferably, the chamber comprises an open first end through which at least a portion of an aerosol-generating article may be inserted into the chamber and a closed second end opposite the open first end.

[0071] The aerosol-generating device may comprise at least one protrusion extending into the chamber from the closed second end of the chamber. Advantageously, the at least one protrusion may abut an upstream end of an aerosol-generating article received within the chamber to space the upstream end of the aerosol-generating article apart from the closed end of the chamber. Advantageously, spacing the upstream end of the aerosol-generating article from the closed end of the chamber may facilitate airflow into the aerosol-generating article during use.

[0072] The aerosol-generating device may comprise a housing, wherein the inductor coil, the resistive heating element, the heat-conducting element, the power supply and the control circuitry are positioned within the housing. Preferably, the housing comprises an end wall defining the closed second end of the chamber, wherein the at least one protrusion extends into the chamber from the end wall. Preferably, the at least one protrusion is formed integrally with the end wall.

[0073] Preferably, the at least one protrusion comprises at least three protrusions. Advantageously, providing at least three protrusions may facilitate secure and correct positioning of an aerosol-generating article in the chamber. Preferably, the chamber has a longitudinal axis defining a first direction along which at least a portion of an aerosol-generating article may be inserted into the chamber, wherein the at least three protrusions are equidistantly spaced from each other in a circumferential direction around the longitudinal axis.

[0074] The aerosol-generating device may comprise a susceptor element. Advantageously, providing a susceptor element as part of the aerosol-generating device may eliminate the need to provide each aerosol-generating article with a susceptor element. Advantageously, this may reduce the cost of each aerosol-generating article.

[0075] As used herein, the term “susceptor element” refers to an element comprising a material that is capable of converting the energy of a magnetic field into heat. When a susceptor element is located in an alternating magnetic field, the susceptor is inductively heated. Heating of the susceptor may be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0076] Preferably, the susceptor element is an elongate susceptor element. Preferably, the elongate susceptor element extends into the chamber from the closed second end of the chamber. Preferably, at least a portion of the elongate susceptor element is positioned inside the inductor coil.

[0077] The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to aerosolise an aerosol-forming substrate. Suitable materials for the susceptor element include graphite, molybdenum, silicon carbide, stainless steels, niobium, and aluminium. Preferred susceptor elements comprise a metal or carbon. Preferably, the susceptor element comprises or consists of a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy, such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. A suitable susceptor element may be, or comprise, aluminium. The susceptor element preferably comprises more than about 5 percent, preferably more than about 20 percent, more preferably more than about 50 percent or more than 90 percent of ferromagnetic or paramagnetic materials. Preferred susceptor elements may be heated to a temperature in excess of about 250 degrees Celsius.

[0078] The susceptor element may comprise a non-metallic core with a metal layer disposed on the non-metallic core. For example, the susceptor element may comprise one or more metallic tracks formed on an outer surface of a ceramic core or substrate.

[0079] The susceptor element may have a protective external layer, for example a protective ceramic layer or protective glass layer. The protective external layer may encapsulate the susceptor element. The susceptor element may comprise a protective coating formed by a glass, a ceramic, or an inert metal, formed over a core of susceptor material.

[0080] The susceptor element may have any suitable cross-section. For example, the susceptor element may have a square, oval, rectangular, triangular, pentagonal, hexagonal, or similar cross- sectional shape. The susceptor element may have a planar or flat cross-sectional shape.

[0081] The susceptor element may be solid, hollow, or porous. Preferably, the susceptor element is solid.

[0082] In embodiments in which the susceptor element has a planar or flat cross-sectional shape, preferably the susceptor element has a thickness of between about 1 millimetre and about 8 millimetres, more preferably from about 3 millimetres to about 5 millimetres. The thickness of the susceptor element is measured in a longitudinal direction of the aerosol-generating device. Preferably, the susceptor element has a width or a diameter of between about 3 millimetres and about 12 millimetres, more preferably between about 4 millimetres and about 10 millimetres, more preferably between about 5 millimetres and about 8 millimetres. The width or diameter of the susceptor element is orthogonal to its thickness.

[0083] In embodiments in which the susceptor element is an elongate susceptor element, preferably the elongate susceptor element is in the form of a pin, rod, blade, or plate. Preferably, the elongate susceptor element has a length of between about 5 millimetres and about 15 millimetres, for example between about 6 millimetres and about 12 millimetres, or between about 8 millimetres and about 10 millimetres. The elongate susceptor element preferably has a width of between about 1 millimetre and about 8 millimetres, more preferably from about 3 millimetres to about 5 millimetres. The elongate susceptor element may have a thickness of from about 0.01 millimetres to about 2 millimetres. If the elongate susceptor element has a constant cross-section, for example a circular cross-section, it has a preferable width or diameter of between about 1 millimetre and about 5 millimetres.

[0084] Preferably, the heat-conducting element is formed from a first material and the susceptor element is formed from a second material, wherein the first material is different to the second material. Advantageously, forming the heat-conducting element and the susceptor element from different materials may facilitate reduced or minimised inductive coupling between the inductor coil and the heat-conducting element and increased or maximised inductive coupling between the inductor coil and the susceptor element.

[0085] Preferably, the inductor coil is arranged so that, when an aerosol-generating article is inserted into the chamber, at least part of the aerosol-generating article is received within the inductor coil.

[0086] The inductor coil may be formed from a coiled wire. The wire may comprise an electrically conductive core and a coating on the electrically conductive core. Preferably, the coating is electrically insulating. Advantageously, an electrically insulating coating may prevent electrical short circuit between adjacent windings of the inductor coil. Advantageously, an electrically insulating coating may electrically isolate the inductor coil from the heat-conducting element. The coating may comprise at least one of a polymer, a ceramic, and a glass. The coating may comprise parylene.

[0087] The inductor coil may be formed from any suitable electrically conductive material. Preferably, the inductor coil is formed from a metal or a metal alloy. The inductor coil may be formed from at least one of copper, a copper alloy, a copper-nickel alloy, tungsten, aluminium, an aluminium alloy, and a steel. Suitable steels include stainless steels, such as 316 stainless steels. In embodiments in which the inductor coil comprises an electrically conductive core, the metal or the metal alloy may form the electrically conductive core.

[0088] In examples in which the aerosol-generating device comprises a resistive heating coil, the resistive heating coil may comprise metal. The resistive heating coil may comprise stainless steel. The resistive heating coil may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the resistive heating coil via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating coil.

[0089] The resistive heating coil may be formed from a coiled wire. The wire may comprise an electrically conductive core and a coating on the electrically conductive core. Preferably, the coating is electrically insulating. Advantageously, an electrically insulating coating may prevent electrical short circuit between adjacent windings of the resistive heating coil. Advantageously, an electrically insulating coating may electrically isolate the resistive heating coil from the heat- conducting element. The coating may comprise at least one of a polymer, a ceramic, and a glass. The coating may comprise parylene.

[0090] The inductor coil may comprise a different material to the resistive heating coil. The inductor coil may consist of a different material to the resistive heating coil.

[0091] The power supply may be a DC power supply. In one embodiment, the power supply is a DC power supply having a DC supply voltage in the range of about 2.5 Volts to about 4.5 Volts and a DC supply current in the range of about 1 Amp to about 10 Amps (corresponding to a DC power supply in the range of about 2.5 Watts to about 45 Watts).

[0092] The power supply may be configured to operate at high frequency. As used herein, the term “high frequency oscillating current” means an oscillating current having a frequency of between about 500 kilohertz and about 30 megahertz. The high frequency oscillating current may have a frequency of from about 1 megahertz to about 30 megahertz, preferably from about 1 megahertz to about 10 megahertz and more preferably from about 5 megahertz to about 8 megahertz.

[0093] The aerosol-generating device comprises control circuitry connected to the inductor coil and the power supply. The control circuitry is configured to control the supply of power to the inductor coil from the power supply. The control circuitry may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control. The control circuitry may comprise further electronic components. The control circuitry may be configured to regulate a supply of current to the inductor coil. Current may be supplied to the inductor coil continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff by puff basis. The control circuitry may advantageously comprise DC / AC inverter, which may comprise a Class-D or Class-E power amplifier.

[0094] Preferably, the aerosol-generating device is portable. The aerosol-generating device may have a size comparable to a conventional cigar or cigarette. The aerosol-generating device may have a total length between approximately 30 millimetres and approximately 150 millimetres. The aerosol-generating device may have an external diameter between approximately 5 millimetres and approximately 30 millimetres.

[0095] The aerosol-generating device housing may be elongate. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics that are suitable for food or pharmaceutical applications, for example polypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably, the material is light and non-brittle.

[0096] The housing may comprise a mouthpiece. The mouthpiece may comprise at least one air inlet and at least one air outlet. The mouthpiece may comprise more than one air inlet. One or more of the air inlets may reduce the temperature of the aerosol before it is delivered to a user and may reduce the concentration of the aerosol before it is delivered to a user.

[0097] Alternatively, the mouthpiece may be provided as part of an aerosol-generating article.

[0098] As used herein, the term “mouthpiece” refers to a portion of an aerosol-generating device that is placed into a user’s mouth in order to directly inhale an aerosol generated by the aerosolgenerating device from an aerosol-generating article received in the chamber of the housing.

[0099] The aerosol-generating device may include a user interface to activate the device, for example a button to initiate heating of the device or display to indicate a state of the device or of the aerosol-forming substrate.

[0100] According to the present disclosure there is also provided an aerosol-generating system. The aerosol-generating system comprises an aerosol-generating device according to the present disclosure, in accordance with any of the embodiments described herein. The aerosol-generating system also comprises an aerosol-generating article comprising an aerosol-forming substrate.

[0101] 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.

[0102] As used herein, the term “aerosol-forming substrate” refers to a substrate consisting of or comprising an aerosol-forming material that is capable of releasing volatile compounds upon heating to generate an aerosol. The aerosol-generating article may comprise an article susceptor element. Preferably, the article susceptor element is positioned in direct contact with the aerosol-forming substrate. Preferably, the article susceptor element is an internal susceptor element positioned within the aerosol-forming substrate.

[0103] Preferably, the aerosol-generating article is configured so that at least a portion of the article susceptor element is positioned within the inductor coil when the aerosol-generating article is inserted into the chamber of the aerosol-generating device.

[0104] The article susceptor element may comprise any of the optional or preferred features described above with respect to a susceptor element forming part of the aerosol-generating device.

[0105] Preferably, the heat-conducting element is formed from a first material and the article susceptor element is formed from a second material, wherein the first material is different to the second material. Advantageously, forming the heat-conducting element and the article susceptor element from different materials may facilitate reduced or minimised inductive coupling between the inductor coil and the heat-conducting element and increased or maximised inductive coupling between the inductor coil and the article susceptor element.

[0106] Preferably, the aerosol-forming substrate is a solid aerosol-forming substrate. However, the aerosol-forming substrate may comprise both solid and liquid components. Alternatively, the aerosol-forming substrate may be a liquid aerosol-forming substrate.

[0107] Preferably, the aerosol-forming substrate comprises nicotine. More preferably, the aerosol-forming substrate comprises tobacco. Alternatively or in addition, the aerosol-forming substrate may comprise a non-tobacco containing aerosol-forming material.

[0108] If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosolforming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, strands, strips or sheets containing one or more of: herb leaf, tobacco leaf, tobacco ribs, expanded tobacco and homogenised tobacco.

[0109] Optionally, the solid aerosol-forming substrate may contain tobacco or non-tobacco volatile flavour compounds, which are released upon heating of the solid aerosol-forming substrate. The solid aerosol-forming substrate may also contain one or more capsules that, for example, include additional tobacco volatile flavour compounds or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol-forming substrate.

[0110] Optionally, the solid aerosol-forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may take the form of powder, granules, pellets, shreds, strands, strips or sheets. The solid aerosol-forming substrate may be deposited on the surface of the carrier in the form of, for example, a sheet, foam, gel or slurry. The solid aerosol-forming substrate may be deposited on the entire surface of the carrier, or alternatively, may be deposited in a pattern in order to provide a non-uniform flavour delivery during use. In a preferred embodiment, the aerosol-forming substrate comprises homogenised tobacco material. As used herein, the term “homogenised tobacco material” refers to a material formed by agglomerating particulate tobacco.

[0111] Preferably, the aerosol-forming substrate comprises a gathered sheet of homogenised tobacco material. As used herein, the term “sheet” refers to a laminar element having a width and length substantially greater than the thickness thereof. As used herein, the term “gathered” is used to describe a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosol-generating article. Preferably, the aerosol-forming substrate comprises an aerosol former. As used herein, the term “aerosol former” is used to describe any suitable known compound or mixture of compounds that, in use, facilitates formation of an aerosol and that is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article.

[0112] Suitable aerosol-formers are known in the art and include, but are not limited to: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and, most preferred, glycerine.

[0113] The aerosol-forming substrate may comprise a single aerosol former. Alternatively, the aerosol-forming substrate may comprise a combination of two or more aerosol formers.

[0114] The invention is defined in the claims. However, 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.

[0115] Example 1 : An aerosol-generating device comprising: a tubular heat-conducting element comprising a cylindrical inner surface forming a curved plane, wherein the cylindrical inner surface at least partially defines a chamber for receiving at least a portion of an aerosol-generating article so that an aerosol-generating article received within the chamber directly contacts the cylindrical inner surface; a resistive heating element; an inductor coil extending around at least a portion of the heat-conducting element; and a power supply and control circuitry; wherein the power supply and control circuitry are connected to the resistive heating element and configured to provide an electric current to the resistive heating element so that, in use, the resistive heating element heats the tubular heat-conducting element; and wherein the power supply and control circuitry are connected to the inductor coil and configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field. Example 2: An aerosol-generating device according to Example 1 , wherein the tubular heat-conducting element is the resistive heating element, and wherein the power supply and control circuitry are configured to provide the electric current to the tubular heat-conducting element so that, in use, the tubular heat-conducting element is resistively heated.

[0116] Example s: An aerosol-generating device according to Example 1 , wherein the resistive heating element is arranged in direct contact with the tubular heat-conducting element, optionally wherein the resistive heating element directly contacts an outer surface of the tubular heat-conducting element, optionally wherein the resistive heating element is at least partially embedded within the tubular heat-conducting element.

[0117] Example 4: An aerosol-generating device according to Example 1 or 3, wherein the resistive heating element is a resistive heating coil, and wherein the resistive heating coil extends around at least a portion of the tubular heat-conducting element.

[0118] Example 5: An aerosol-generating device according to any preceding Example, wherein the chamber comprises a first end defining an opening for receiving an aerosolgenerating article and a second end opposite the first end, wherein the aerosol-generating device further comprises a housing defining at least one air inlet and at least one airflow passage extending between the at least one air inlet and the second end of the chamber, and wherein the at least one airflow passage is positioned outside of the chamber.

[0119] Example 6: An aerosol-generating device according to Example 5, wherein the at least one air inlet is positioned adjacent the opening, and wherein the at least one airflow passage extends between the outer surface of the tubular heat-conducting element and an inner surface of the housing.

[0120] Example 7: An aerosol-generating device according to Example 5, wherein the chamber defines a longitudinal direction extending between the first end and the second end, wherein the at least one air inlet extends through a sidewall of the housing, and wherein at least a portion of the at least one airflow passage extends perpendicular to the longitudinal direction.

[0121] Example 8: An aerosol-generating device according to any preceding Example, wherein the curved plane defines a circular cross-sectional shape of the chamber.

[0122] Example 9: An aerosol-generating device according to any preceding Example, wherein the tubular heat-conducting element extends in a longitudinal direction, and wherein the curved plane extends in a circumferential direction about the longitudinal direction.

[0123] Example 10: An aerosol-generating device according to Examples 8 and 9, wherein the circular cross-sectional shape of the chamber has a constant diameter in all directions perpendicular to the longitudinal direction.

[0124] Example 11 : An aerosol-generating device according to Example 8, 9 or 10, wherein the circular cross-sectional shape of the chamber has a roundness of at least 0.999. Example 12: An aerosol-generating device according to any preceding Example, wherein the heat-conducting element is formed from at least one of a non-electrically conductive material and a non-inductively heatable material.

[0125] Example 13: An aerosol-generating device according to any preceding Example, wherein the heat-conducting element comprises at least one of a polymeric material, a ceramic, and a metal, optionally wherein the heat-conducting element comprises at least one of an alumina ceramic and a zirconia ceramic.

[0126] Example 14: An aerosol-generating device according to any preceding Example, wherein the heat-conducting element comprises at least one of aluminium and a paramagnetic steel, optionally wherein the paramagnetic steel comprises an austenitic steel.

[0127] Example 15: An aerosol-generating device according to any preceding Example, further comprising a susceptor element, optionally wherein the heat-conducting element is formed from a first material, wherein the susceptor element is formed from a second material, and wherein the first material is different to the second material.

[0128] Example 16: An aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to provide the alternating electric current in the form of an alternating current having a frequency selected to prevent inductive coupling between the heat-conducting element and the inductor coil during use.

[0129] Example 17: An aerosol-generating device according to any preceding Example, wherein the heat-conducting element comprises a polymeric material and at least one of carbon fibres, carbon nanotubes, graphite, a graphite-derived material, and hexagonal boron nitride dispersed within the polymeric material.

[0130] Example 18: An aerosol-generating device according to Example 17, wherein the polymeric material comprises at least one of polyether ether ketone (PEEK) and a liquid crystal polymer (LCP).

[0131] Example 19: An aerosol-generating device according to Example 17 or 18, wherein the heat-conducting element comprises the polymeric material in an amount of between 22 percent and 33 percent by weight of the heat-conducting element.

[0132] Example 20: An aerosol-generating device according to Example 17, 18 or 19, wherein the graphite-derived material comprises at least one of expanded graphite and graphite nanoplatelets.

[0133] Example 21 : An aerosol-generating device according to any of Examples 17 to 20, wherein the heat-conducting element comprises the at least one of carbon fibres, carbon nanotubes, graphite, a graphite-derived material, and hexagonal boron nitride in an amount of between 62 percent and 69 percent by weight of the heat-conducting element.

[0134] Example 22: An aerosol-generating device according to any of Examples 17 to 21 , wherein the heat-conducting element further comprises at least one additive dispersed within the polymeric material. Example 23: An aerosol-generating device according to Example 22, wherein the at least one additive comprises carbon black.

[0135] Example 24: An aerosol-generating device according to Example 22 or 23 wherein the heat-conducting element comprises the at least one additive in an amount of between 5 percent and 9 percent by weight of the heat-conducting element.

[0136] Example 25: An aerosol-generating device according to any preceding Example, wherein the power supply and the control circuitry are connected to the heat-conducting element and configured to provide an electric current to the heat-conducting element during use to resistively heat the heat-conducting element.

[0137] Example 26: An aerosol-generating device according to any preceding Example, wherein the chamber comprises an open first end through which at least a portion of an aerosolgenerating article may be inserted into the chamber and a closed second end opposite the open first end.

[0138] Example 27: An aerosol-generating device according to Example 26, further comprising at least one protrusion extending into the chamber from the closed second end of the chamber.

[0139] Example 28: An aerosol-generating device according to Example 27, wherein the at least one protrusion comprises at least three protrusions.

[0140] Example 29: An aerosol-generating device according to Example 28, wherein the chamber has a longitudinal axis defining a first direction along which at least a portion of an aerosol-generating article may be inserted into the chamber, and wherein the at least three protrusions are equidistantly spaced from each other in a circumferential direction around the longitudinal axis.

[0141] Example 30: An aerosol-generating device according to any preceding Example, further comprising a housing, wherein the inductor coil, the heat-conducting element, the power supply and the control circuitry are positioned within the housing.

[0142] Example 31 : An aerosol-generating device according to the combination of Example 30 with any of Examples 26 to 29, wherein the housing comprises an end wall defining the closed second end of the chamber, and wherein the at least one protrusion extends into the chamber from the end wall.

[0143] Example 32: An aerosol-generating device according to Example 31 , wherein the at least one protrusion is formed integrally with the end wall.

[0144] Example 33: An aerosol-generating device according to any of Examples 26 to 32, further comprising an elongate susceptor element extending into the chamber from the closed second end of the chamber.

[0145] Example 34: An aerosol-generating device according to Example 33, wherein at least a portion of the elongate susceptor element is positioned inside the inductor coil.

[0146] Example 35: An aerosol-generating system comprising: an aerosol-generating device according to any preceding Example; and an aerosol-generating article comprising an aerosol-forming substrate.

[0147] Example 36: An aerosol-generating system according to Example 35, wherein the aerosol-generating article is configured so that at least a portion of the aerosol-forming substrate is positioned within the heat-conducting element when the aerosol-generating article is inserted into the chamber.

[0148] Example 37: An aerosol-generating system according to Example 35 or 36, wherein the aerosol-generating article further comprises an article susceptor element.

[0149] Example 38: An aerosol-generating system according to Example 37, wherein the aerosol-generating article is configured so that at least a portion of the article susceptor element is positioned within the inductor coil when the aerosol-generating article is inserted into the chamber.

[0150] Example 39: An aerosol-generating system according to Example 37 or 38, wherein the heat-conducting element is formed from a first material, wherein the article susceptor element is formed from a second material, and wherein the first material is different to the second material.

[0151] The invention is further described, by way of example only, with reference to the accompanying drawings in which:

[0152] Figure 1 shows a side cross-sectional view of an aerosol-generating device according to a first embodiment of the present invention;

[0153] Figure 2 shows an axial cross-sectional view of the aerosol-generating device of Figure 1 along line 1-1 ;

[0154] Figure 3 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figure 1 ;

[0155] Figure 4 shows a perspective view of a heat conducting element and coil arrangement for an aerosol-generating device according to a second embodiment of the present invention;

[0156] Figure 5 shows a side cross-sectional view of an aerosol-generating device comprising the heat conducting element and coil arrangement of Figure 4;

[0157] Figure 6 shows a partial side cross-sectional view of an aerosol-generating device according to a third embodiment of the present invention;

[0158] Figure 7 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figure 6;

[0159] Figure 8 shows a partial side cross-sectional view of an aerosol-generating device according to a fourth embodiment of the present invention; and

[0160] Figure 9 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figure 8.

[0161] Figures 1 and 2 show an aerosol-generating device 10 in accordance with a first embodiment of the present invention. The aerosol-generating device 10 comprises a housing 12 partially defining a chamber 16 for receiving a portion of an aerosol-generating article. The chamber 16 comprises a first end 18 through which an aerosol-generating article may be inserted into the chamber 16 and a second end 20 opposite the first end 18.

[0162] The aerosol-generating device 10 also comprises a heat-conducting element 28 comprising an outer surface 21 and an inner surface 23. The inner surface 23 has a cylindrical shape and is free from grooves, channels, and other discontinuities. Therefore, the inner surface 23 is smooth and forms a curved plane at least partially defining a cylindrical wall 22 of the chamber 16 that extends between the first end 18 and the second end 20. The heat-conducting element 28 is arranged so that an aerosol-generating article is received within the heat-conducting element 28 and in direct contact with the cylindrical inner surface 23 of the heat-conducting element 28 when the aerosol-generating article is inserted into the chamber 16.

[0163] An inductor coil 24 comprising a plurality of windings 26 extends around an outer surface of the heat-conducting element 28. The inductor coil 24 and the heat-conducting element 28 are arranged concentrically about a central axis 36 of the aerosol-generating device 10.

[0164] As shown in Figure 1 , the housing 12 defines a plurality of air inlets 25 extending through an outer surface of the housing 12 and an airflow passage 27 extending from each air inlet 25. The plurality of airflow passages 27 combine into a single common airflow passage 30 in fluid communication with the second end 20 of the chamber 16. In the embodiment shown in Figure 1 , the housing 12 defines two air inlets 25 and two airflow passages 27 positioned on opposite sides of the housing 12. The skilled person will appreciate that the housing 12 may define more or fewer air inlets 25 and airflow passages 27 and the arrangement of the air inlets 25 and the airflow passages 27 around the housing 12 may be varied.

[0165] The housing 12 also defines a plurality of protrusions 38 extending into the chamber 16 from the second end 20 of the chamber 16. As will be further described below, the plurality of protrusions 38 function to maintain a gap between an end of an aerosol-generating article and the second end 20 of the chamber 16 when the aerosol-generating article is fully inserted into the chamber 16. In the embodiment shown in Figures 1 and 2, the housing 12 defines three protrusions 38 spaced equidistantly about the central axis 36 of the aerosol-generating device 10. The skilled person will appreciate that the housing 12 may define more or fewer protrusions 38 and the arrangement of the protrusions 38 at the closed end 20 of the chamber 16 may be varied.

[0166] The aerosol-generating device 10 also comprises control circuitry 40 and a power supply 42 connected to the inductor coil 24. The control circuitry 40 is configured to provide an alternating electric current from the power supply 42 to the inductor coil 24 to generate an alternating magnetic field. The control circuitry 40 is also configured to provide a direct electric current from the power supply 42 to the heat-conducting element 28. In this way, the heat-conducting element 28 functions as a resistive heating element.

[0167] Figure 3 shows a cross-sectional view of an aerosol-generating system 100 comprising the aerosol-generating device 10 of Figure 1 and an aerosol-generating article 102. The aerosol-generating article 102 comprises an aerosol-forming substrate 104 in the form of a tobacco plug, a first hollow acetate tube 106, a second hollow acetate tube 108, a mouthpiece 110, and an outer wrapper 112. The aerosol-generating article 102 also comprises a susceptor element 114 arranged within the aerosol-forming substrate 104. During use, a portion of the aerosol-generating article 102 is inserted into the chamber 16 so that the aerosol-forming substrate 104 and the susceptor element 114 are positioned inside the heat-conducting element 28 and the inductor coil 24. The control circuitry 40 provides an alternating electric current from the power supply 42 to the inductor coil 24 to generate an alternating magnetic field that inductively heats the susceptor element 114, which heats the aerosol-forming substrate 104 to generate an aerosol. Additionally, heat generated in the inductor coil 24 itself by resistive losses in the inductor coil 24 may be conducted from the inductor coil 24 to the aerosol-forming substrate 104 by the heat-conducting element 28. The control circuitry 40 also provides a direct electric current from the power supply 42 to the heat-conducting element 28 to resistively heat the heat- conducting element 28. Advantageously, the direct contact between the cylindrical inner surface 23 of the heat-conducting element 28 and the aerosol-generating article 102 facilitates the transfer of the resistively generated heat from the heat-conducting element 28 to the aerosol-generating article 102. Advantageously, the smooth, curved plane formed by the cylindrical inner surface 23 of the heat conducting element 28 maximises a contact area between the heat-conducting element 23 and the aerosol-generating article 102, which increases or maximises the transfer of heat from the heat-conducting element 23 to the aerosol-generating article 102. Advantageously, the external heating provided by the resistively heated heat-conducting element 23 and the internal heating provided by the inductively heated susceptor element 114 may provide a uniform heating of the aerosol-forming substrate 104.

[0168] Airflow through the aerosol-generating system 100 during use is illustrated by the dashed lines 116 in Figure 3. When a user draws on the mouthpiece 110 of the aerosol-generating article 102, a negative pressure is generated in the chamber 16. The negative pressure draws air into the aerosol-generating device 10 through the air inlets 25. The air entering the air inlets 25 flows along the airflow passages 27 and into the common airflow passage 30 where it reaches the second end 20 of the chamber 16. The air entering the second end 20 of the chamber 16 then enters the aerosol-generating article 102 through the aerosol-forming substrate 104. Airflow into the aerosol-generating article 102 is facilitated by the gap maintained between the upstream end of the aerosol-generating article 102 and the second end 20 of the chamber 16 by the plurality of protrusions 38. As the airflow passes through the aerosol-forming substrate 104, aerosol generated by heating of the aerosol-forming substrate 104 is entrained in the airflow. The aerosol then flows along the length of the aerosol-generating article 102 and through the mouthpiece 110 to the user.

[0169] Figure 4 shows a perspective view of a heat conducting element and coil arrangement for an aerosol-generating device according to a second embodiment of the present invention. Figure 5 shows a cross-sectional view of an aerosol-generating device 110 comprising the heat conducting element and coil arrangement of Figure 4. The embodiment of Figures 4 and 5 shares features with the embodiment of Figures 1 to 3 and like reference numerals are used to designate like parts.

[0170] The embodiment of Figure 4 comprises the same tubular heat-conducting element 28 as the embodiment of Figure 1 and an inductor coil 124 comprising a plurality of windings 126 extending around the outer surface 21 of the heat-conducting element 28 so that the plurality of windings 126 are in direct contact with the outer surface 21 of the heat-conducting element 28. The arrangement of Figure 4 also comprises a resistive heating coil 133 having a plurality of windings 135 extending around the outer surface 21 of the heat-conducting element 28 so that the plurality of windings 135 are in direct contact with the outer surface 21 of the heat-conducting element 28. The resistive heating coil 133 is co-wound with the inductor coil 124 around the outer surface 12 of the heat-conducting element 28. During use, the control circuitry 40 provides an alternating electric current from the power supply 42 to the inductor coil 124 to generate an alternating magnetic field that inductively heats a susceptor element of an aerosol-generating article, which may provide internal heating of an aerosol-forming substrate. For example, the aerosol-generating device 100 of Figure 5 may be used with the aerosol-generating article 102 of Figure 3. During use, the control circuitry 40 also provides a direct electric current from the power supply 42 to the resistive heating coil 133 to resistively heat the resistive heating coil 133. The heat generated by the resistive heating coil 133 is conducted through the tubular heat-conducting element 28 to the aerosol-generating article to provide external heating of the aerosol-forming substrate.

[0171] Figure 6 shows a partial cross-sectional view of a variation of the aerosol-generating device 110 of Figure 5. The embodiment of Figure 6 shares features with the embodiments of Figures 1 and 5 and like reference numerals are used to designate like parts.

[0172] The embodiment of Figure 6 comprises the same tubular heat-conducting element 28 and inductor coil 24 as the embodiment of Figure 1 , and the same resistive heating coil 133 as the embodiment of Figure 5. The embodiment of Figure 6 has an alternative airflow arrangement defined by the housing 212. Specifically, the housing 212 defines a plurality of air inlets 225 extending through an inner surface of the chamber 16 and an airflow passage 227 extending from each air inlet 225. The airflow passages 227 extend outside of the chamber 16 so that airflow through the airflow passages 227 flows between the inductor coil 24 and the resistive heating coil 133. Advantageously, heat generated by resistive heating of the inductor coil 24 and the resistive heating coil 133 during use may provide pre-heating of the airflow through the airflow passages 227. The plurality of airflow passages 227 combine into a single common airflow passage 30 in fluid communication with the second end 20 of the chamber 16. In the embodiment shown in Figure 6, the housing 212 defines two air inlets 225 and two airflow passages 227 positioned on opposite sides of the chamber 16. The skilled person will appreciate that the housing 212 may define more or fewer air inlets 225 and airflow passages 227 and the arrangement of the air inlets 225 and the airflow passages 227 around the chamber 16 may be varied.

[0173] Figure 7 shows a cross-sectional view of an aerosol-generating system 300 comprising the aerosol-generating device 210 of Figure 6 and an aerosol-generating article 302. The aerosolgenerating article 302 is similar to the aerosol-generating article 102 described with reference to Figure 3 and like reference numerals designate like parts. The aerosol-generating article 302 differs by the addition of a front plug 315 of cellulose acetate positioned upstream of the aerosolforming substrate 104.

[0174] Airflow through the aerosol-generating system 300 during use is illustrated by the dashed lines 316 in Figure 7. When a user draws on the mouthpiece 110 of the aerosol-generating article 302, a negative pressure is generated in the chamber 16. The negative pressure draws air into the aerosol-generating device 210 through the air inlets 225. In this regard, the housing 212 is spaced apart from the aerosol-generating article 302 at the first end 18 of the chamber 16 to allow air to enter the air inlets 225. The air entering the air inlets 225 flows along the airflow passages 227 outside of the chamber 16 and into the common airflow passage 30 where it reaches the second end 20 of the chamber 16. The air entering the second end 20 of the chamber 16 then enters the aerosol-generating article 302 through the front plug 315. Airflow into the aerosolgenerating article 302 is facilitated by the gap maintained between the upstream end of the aerosol-generating article 302 and the second end 20 of the chamber 16 by the plurality of protrusions 38. As the airflow passes through the aerosol-forming substrate 104, aerosol generated by heating of the aerosol-forming substrate 104 is entrained in the airflow. The aerosol then flows along the length of the aerosol-generating article 302 and through the mouthpiece 110 to the user.

[0175] Figure 8 shows a partial cross-sectional view of an alternative arrangement of the aerosolgenerating device of Figure 6. In this regard, the aerosol-generating device 410 of Figure 8 is similar to the aerosol-generating device 210 of Figure 6 and like parts are designated with like reference numerals.

[0176] The aerosol-generating device 410 of Figure 8 differs by the addition of an elongate susceptor element 411 extending into the chamber 16 from the second end 20 of the chamber 16. When an aerosol-generating article is inserted into the chamber 16, the elongate susceptor element 411 is received within an aerosol-forming substrate of the aerosol-generating article. During use, the control circuitry 40 provides an alternating electric current from the power supply 42 to the inductor coil 24 to generate an alternating magnetic field that inductively heats the elongate susceptor element 411 to heat the aerosol-forming substrate.

[0177] To accommodate the susceptor element 411 , the aerosol-generating device 410 does not include a common airflow passage at the second end 20 of the chamber 16. Instead, each of the airflow passages 427 flows through a sidewall 429 of the chamber 16 to deliver airflow into the chamber 16 upstream of the second end 20. Figure 9 shows a cross-sectional view of an aerosol-generating system 500 comprising the aerosol-generating device 410 of Figure 8 and an aerosol-generating article 502. The aerosolgenerating article 502 is similar to the aerosol-generating article 302 described with reference to Figure 7 and like reference numerals designate like parts. The aerosol-generating article 502 differs by the lack of a susceptor element within the aerosol-forming substrate 104.

[0178] Airflow through the aerosol-generating system 500 during use is illustrated by the dashed lines 516 in Figure 9. When a user draws on the mouthpiece 110 of the aerosol-generating article 502, a negative pressure is generated in the chamber 16. The negative pressure draws air into the aerosol-generating device 410 through the air inlets 225. In this regard, the housing 212 is spaced apart from the aerosol-generating article 502 at the first end 18 of the chamber 16 to allow air to enter the air inlets 225. The air entering the air inlets 225 flows along the airflow passages 227 outside of the chamber 16 and the enters the chamber 16 upstream of the tubular heat- conducting element 28 and downstream of the second end 20 of the chamber 16. The air entering the chamber 16 from the airflow passages 227 then enters the aerosol-generating article 502 by flowing through the outer wrapper 112 and into the front plug 315. Airflow through the outer wrapper 112 may be facilitated by providing the outer wrapper 112 with a region of increased porosity extending around at least one of the front plug 315 and the aerosol-forming substrate 104. As the airflow passes through the aerosol-forming substrate 104, aerosol generated by heating of the aerosol-forming substrate 104 is entrained in the airflow. The aerosol then flows along the length of the aerosol-generating article 502 and through the mouthpiece 110 to the user.

[0179] The skilled person will appreciate that the elongate susceptor element 411 may be combined with the other embodiments of Figures 1 to 7. For example, the aerosol-generating device 210 of Figure 6 could be modified to include a plurality of elongate susceptor elements arranged around the common airflow passage 30. Alternatively, the aerosol-generating device 210 of Figure 6 could be modified to include a single elongate susceptor element and to substitute the common airflow passage 30 with a plurality of openings in the second end 20 of the chamber 16, wherein the plurality of openings is arranged around the single elongate susceptor element and each airflow passage 27 delivers airflow to the second end 20 of the chamber 16 through one of the openings. Similar modifications could be made to the aerosol-generating device 10 of Figure 1 to accommodate a single elongate susceptor element or a plurality of elongate susceptor elements. Furthermore, an aerosol-generating device comprising one or more elongate susceptor elements extending into the chamber 16 may also comprise the coil arrangement Figure 4.

Claims

Claims1. An aerosol-generating device comprising: a tubular heat-conducting element comprising a cylindrical inner surface forming a curved plane, wherein the cylindrical inner surface at least partially defines a chamber for receiving at least a portion of an aerosol-generating article so that an aerosol-generating article received within the chamber directly contacts the cylindrical inner surface; a resistive heating element formed separately from the tubular heat-conducting element; an inductor coil extending around at least a portion of the heat-conducting element; and a power supply and control circuitry; wherein the power supply and the control circuitry are connected to the resistive heating element and configured to provide an electric current to the resistive heating element so that, in use, the resistive heating element heats the tubular heat-conducting element; and wherein the power supply and the control circuitry are connected to the inductor coil and configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field.

2. An aerosol-generating device according to claim 1 , wherein the resistive heating element extends around at least a portion of the tubular heat-conducting element.

3. An aerosol-generating device according to claim 1 , wherein the resistive heating element is arranged in direct contact with the tubular heat-conducting element, optionally wherein the resistive heating element directly contacts an outer surface of the tubular heat-conducting element, optionally wherein the resistive heating element is at least partially embedded within the tubular heat-conducting element.

4. An aerosol-generating device according to claim 1 , 2 or 3, wherein the resistive heating element is a resistive heating coil, and wherein the resistive heating coil extends around at least a portion of the tubular heat-conducting element.

5. An aerosol-generating device according to any preceding claim, wherein the chamber comprises a first end defining an opening for receiving an aerosol-generating article and a second end opposite the first end, wherein the aerosol-generating device further comprises a housing defining at least one air inlet and at least one airflow passage extending between the at least one air inlet and the second end of the chamber, and wherein the at least one airflow passage is positioned outside of the chamber.

6. An aerosol-generating device according to claim 5, wherein the at least one air inlet is positioned adjacent the opening, and wherein the at least one airflow passage extends between the outer surface of the tubular heat-conducting element and an inner surface of the housing.

7. An aerosol-generating device according to claim 5, wherein the chamber defines a longitudinal direction extending between the first end and the second end, wherein the at least one air inlet extends through a sidewall of the housing, and wherein at least a portion of the at least one airflow passage extends perpendicular to the longitudinal direction.

8. An aerosol-generating device according to any preceding claim, wherein the curved plane defines a circular cross-sectional shape of the chamber.

9. An aerosol-generating device according to any preceding claim, wherein the tubular heat- conducting element extends in a longitudinal direction, and wherein the curved plane extends in a circumferential direction about the longitudinal direction.

10. An aerosol-generating device according to claims 8 and 9, wherein the circular cross- sectional shape of the chamber has a constant diameter in all directions perpendicular to the longitudinal direction.

11. An aerosol-generating device according to any preceding claim, wherein the heat- conducting element is formed from at least one of a non-electrically conductive material and a non-inductively heatable material.

12. An aerosol-generating device according to any preceding claim, wherein the heat- conducting element comprises at least one of a polymeric material, a ceramic, and a metal, optionally wherein the heat-conducting element comprises at least one of an alumina ceramic and a zirconia ceramic.

13. An aerosol-generating device according to any preceding claim, wherein the heat- conducting element comprises at least one of aluminium and a paramagnetic steel, optionally wherein the paramagnetic steel comprises an austenitic steel.

14. An aerosol-generating device according to any preceding claim, further comprising a susceptor element, optionally wherein the heat-conducting element is formed from a first material, wherein the susceptor element is formed from a second material, and wherein the first material is different to the second material.

15. An aerosol-generating system comprising: an aerosol-generating device according to any preceding claim; and an aerosol-generating article comprising an aerosol-forming substrate.

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