Patent Description:
Smoking articles in which an aerosol-forming substrate, such as a tobacco containing substrate, is heated rather than combusted are known in the art. The aim of such heated smoking articles is to reduce known harmful smoke constituents produced by the combustion and pyrolytic degradation of tobacco in conventional cigarettes. Typically in such heated smoking articles, an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-forming substrate or material, which may be located within, around or downstream of the heat source. During smoking, volatile compounds are released from the aerosol-forming substrate by heat transfer from the heat source and entrained in air drawn through the smoking article. As the released compounds cool, they condense to form an aerosol that is inhaled by the consumer.

A number of prior art documents disclose aerosol-generating devices for consuming or smoking heated smoking articles. Such devices include, for example, heated smoking systems and electrically heated smoking systems. One advantage of these systems is that they significantly reduce sidestream smoke, while permitting the smoker to selectively suspend and reinitiate smoking. An example of a heated smoking system is disclosed in <CIT>, which includes in one embodiment a flavour-generating medium in contact with a heater. When the medium is exhausted, both it and the heater are replaced. An aerosol-generating device where a smoking article can be replaced without the need to remove the heating element is desirable.

Typically, smoking articles for use with aerosol-generating devices comprise an aerosol-forming substrate that is assembled, often with other elements or components, in the form of a rod. Typically, such a rod is configured in shape and size to be inserted into an aerosol-generating device that comprises a heating element for heating the aerosol-forming substrate.

Other aerosol-generating devices, such as the electrical lighter disclosed in <CIT>, use a sleeve, e.g., ceramic or metal, surrounds the heater fixture, and a resistive heating element is in thermal proximity with the sleeve. In conjunction with the sleeve-type heater, a cleaning element is optionally inserted into the cigarette receptacle of the electrical lighter or placed at the exit thereof to absorb, attract and/or catalytically break down the thermally liberated condensates. In such systems, the cigarette heater fixture may be defined by blades that concentrically surround an inserted cigarette.

Another aerosol-generating device is described in <CIT>, wherein the heating element includes heating blades and a secondary can. The heating blades are activated by a control circuitry which controls which blades are heated, how hot and how long they are heated. The heated blades ignite cigarette, which produces smoke and condensates. The secondary can (also referred to as a "secondary heater") surrounds the heating blades. The secondary can acts to direct air flow, keep the outer housing from getting hot, and trap the condensates from attaching to other areas of the heating element and smoking device. The secondary can will accumulate a large portion of condensates released during the use of the smoking device since it is arranged radially outward from the heating blades and in the path of condensates that are produced. Therefore, cleaning the condensates from the secondary can may be necessary to allow the smoking device to function as designed. Thus, the secondary can may be cleaned by inductive heating.

In contrast to such systems, direct contact between a heating element, for example an electrically actuated heating element, and the aerosol-forming substrate may provide an efficient means for heating the aerosol-forming substrate to form an inhalable aerosol. In such a device configuration, heat from a heating element may be conveyed almost instantaneously to at least a portion of the aerosol-forming substrate when the heating element is actuated, and this may facilitate the rapid generation of an aerosol. Furthermore, the overall heating energy required to generate an aerosol may be lower than would be the case in a system where the aerosol-forming substrate does not directly contact a heating element and initial heating of the substrate occurs by convection or radiation. Where a heating element is in direct contact with an aerosol-forming substrate, the initial heating of portions of the substrate that are in contact with the heating element will be effected by conduction.

As used herein, an 'aerosol-generating device' relates to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-forming substrate may be part of an aerosol-generating article, for example part of a smoking article. An aerosol-generating device may comprise one or more components used to supply energy from a power supply to an aerosol-forming substrate to generate an aerosol.

An aerosol-generating device may be described as a heated aerosol-generating device, which is an aerosol-generating device comprising a heater. The heater is preferably used to heat an aerosol-forming substrate of an aerosol-generating article to generate an aerosol.

An aerosol-generating device may be an electrically heated aerosol-generating device, which is an aerosol-generating device comprising a heater that is operated by electrical power to heat an aerosol-forming substrate of an aerosol-generating article to generate an aerosol. An aerosol-generating device may be a gas-heated aerosol-generating device. An aerosol-generating device may be a smoking device that interacts with an aerosol-forming substrate of an aerosol-generating article to generate an aerosol that is directly inhalable into a user's lungs thorough the user's mouth.

As used herein, the term 'aerosol-forming substrate' relates to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may be adsorbed, coated, impregnated or otherwise loaded onto a carrier or support. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article.

An aerosol-forming substrate may be solid or liquid and 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.

As used herein, the terms 'aerosol-generating article' and 'smoking article' refer to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be a smoking article that generates an aerosol that is directly inhalable into a user's lungs through the user's mouth. An aerosol-generating article may be disposable.

Preferably an aerosol-generating article is a heated aerosol-generating article, which is an aerosol-generating article comprising an aerosol-forming substrate that is intended to be heated rather than combusted in order to release volatile compounds that can form an aerosol. The aerosol formed by heating the aerosol-forming substrate may contain fewer known harmful constituents than would be produced by combustion or pyrolytic degradation of the aerosol-forming substrate. An aerosol-generating article may be, or may comprise, a tobacco stick.

The present invention provides in claim <NUM> a method of using an aerosol-generating device; furthermore, claim <NUM> defines an aerosol-generating device and claim <NUM> defines an aerosol-generating system.

Various embodiments are set out in this specification.

Thus, in one aspect the present specification may provide a method of using an aerosol-generating device that has a reusable heating element for heating an aerosol-forming substrate. The method comprises the steps of bringing the heating element into direct contact with the aerosol-forming substrate and raising the temperature of the heating element to a first temperature to heat the aerosol-forming substrate such that an aerosol is formed. The method then provides the steps of removing or withdrawing the heating element from contact with the aerosol-forming substrate and raising the temperature of the heating element to a second temperature sufficient to thermally liberate organic materials deposited on the heating element. The second temperature is a higher temperature than the first temperature. The thermal liberation may occur by a pyrolysis or carbonisation reaction.

The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, 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. Alternatively, 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.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, spaghettis, strips or sheets containing one or more of: herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, processed tobacco, homogenised tobacco, extruded tobacco and expanded tobacco. The solid aerosol-forming substrate may be in loose form, or may be provided in a suitable container or cartridge. For example, the aerosol-forming material of the substrate may be contained within a paper or wrap and have the form of a plug. Where an aerosol-forming substrate is in the form of a plug, the entire plug including any wrapping paper is considered to be the aerosol-forming substrate.

Optionally, the solid aerosol-forming substrate may contain additional tobacco or non-tobacco volatile flavour compounds, to be released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules that, for example, include the additional tobacco or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol-forming substrate.

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, spaghettis, 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 preferred embodiments, the aerosol-forming substrate is contained in a smoking article, for example a rod-shaped smoking article such as a cigarette. The smoking article is preferably of suitable size and shape to engage with the aerosol-generating device so as to bring the aerosol-forming substrate into contact with the heating element of the device. For example, the smoking article may have a total length between approximately <NUM> and approximately <NUM>. The smoking article may have an external diameter between approximately <NUM> and approximately <NUM>.

The terms upstream and downstream may be used to describe relative positions of elements or components of the smoking article. For simplicity, the terms "upstream" and "downstream" as used herein refer to a relative position along the rod of the smoking article with reference to the direction in which the aerosol is drawn through the rod.

The heating element may conveniently be shaped as a needle, pin, rod, or blade that may be inserted into a smoking article in order to contact the aerosol-forming substrate. The aerosol-generating device may comprise more than one heating element and in the following description reference to a heating element means one or more heating elements.

The temperature of the heating element can be raised to both the first temperature and to the second temperature. The temperature may be raised by any suitable method. For example, the temperature may be raised by conduction caused by contact with another heat source. In accordance with the present invention, the temperature is raised by inductive heating caused by a fluctuating electromagnetic field. The temperature may be raised by resistive heating caused by passing an electric current through a conductive wire or resistive track. In one embodiment, the track may have a resistance between <NUM> and <NUM> ohms.

Preferably the heating element comprises a rigid electrically insulating substrate with an electrically conductive track or wire disposed on its surface. Preferably the size and shape of the electrically insulating substrate allow it to be inserted directly into an aerosol-forming substrate. If the electrically insulating substrate is not sufficiently rigid, the heating element may comprise a further reinforcement means. A current may be passed through the track or wire to heat the heating element and the aerosol-forming substrate.

It is preferable that the aerosol-generating device further comprises electronic circuitry arranged to control the supply of current to the heating element to control the temperature. The aerosol-generating device may also comprise means for sensing the temperature of the heating element. This may enable the electronic circuitry or control circuitry to raise the temperature of the heating element to both the first temperature and the second temperature. It is preferred that the first temperature is a temperature high enough to cause the evolution of volatile compounds from the aerosol-forming substrate and, thus, the formation of an aerosol. It is preferred that the first temperature is not high enough to burn the aerosol-forming substrate.

Preferably the first temperature is lower than about <NUM> degrees centigrade. For example the first temperature may be between <NUM> degrees centigrade and <NUM> degrees centigrade, for example between <NUM> degrees centigrade and <NUM> degrees centigrade. The length of time that the heating element is held at the first temperature may be fixed. For example, the first temperature may be maintained for a period of greater than <NUM> seconds, for example between <NUM> seconds and <NUM> seconds. The length of time that the heating element is held at the first temperature may be a variable. For example, the aerosol-generating device may comprise a sensor that determines when a user is drawing on the smoking article and the time may be controlled by the length of time that the user draws on the smoking article.

During a period in which the heating element is in contact with the aerosol-forming substrate, the heating element undergoes a thermal cycle during which it is heated to the first temperature and then cooled. The heating element is preferably cooler than the first temperature when it is removed from contact with the aerosol-forming substrate. During contact, particles of the aerosol-forming substrate may adhere to a surface of the heating element. Furthermore, volatile compounds and aerosol evolved by the heat from the heating element may become deposited on a surface of the heating element. Particles and compounds adhered to and deposited on the heating element may prevent the heating element from functioning in an optimal manner. These particles and compounds may also break down during use of the aerosol-generating device and impart unpleasant or bitter flavours to a user. For these reasons it is desirable to clean the heating element periodically.

It is preferred that the second temperature is a temperature high enough to thermally liberate organic compounds that are in contact with the heating element. The organic compounds may be any particles or compounds adhered to or deposited on a surface of the heating element during a period of contact between the heating element and a substrate.

Thermal liberation of organic compounds may occur by pyrolysis. Pyrolysis is a process in which chemical compounds decompose due to the action of heat. Organic compounds generally pyrolyse to form organic vapours and liquids, which in the present specification may migrate away from the heating element leaving it in a cleaned state.

It is preferred that organic materials deposited on the heating element are thermally liberated by raising the temperature of the heating element to about <NUM> degrees centigrade or greater. For example, the temperature may be raised to greater than <NUM> degrees centigrade or greater than <NUM> degrees centigrade. The temperature may be raised to higher temperatures such as greater than <NUM> degrees centigrade or greater than <NUM> degrees centigrade.

It is preferable that the heating element is held at the second temperature for a period of time to effect thermal liberation of organic compounds. For example, the heating element may be held at the second temperature for more than <NUM> seconds. Preferably, the heating element is held at the second temperature for a period of between <NUM> seconds and <NUM> seconds, for example between <NUM> seconds and <NUM> seconds.

Smoking articles for use with aerosol-generating devices comprise an amount of an aerosol-forming substrate. The aerosol-forming substrate may be consumed entirely during a single thermal cycle of the heating element. In one such an embodiment, the heater will be constantly on and the temperature will be regulated by the amount of energy provided to the heating element during operation. This may be the case, for example, if the heating element is maintained at the first temperature for the duration of the consumption of the smoking article. Alternatively, the heating element is repeatedly pulsed through thermal cycles to the first temperature and back. These pulses may occur simultaneously with periods when a user is drawing on the smoking article. A portion of aerosol is generated each time the temperature reaches the first temperature and aerosol generation ceases each time the heating element cools again. When no further aerosol is generated the smoking article has been consumed. Thus, there may be more than <NUM> or more than <NUM> or more than <NUM> thermal cycles in which the heating element is raised to the first temperature and then cooled before the smoking article is consumed.

A user may remove a consumed smoking article and replace it with a fresh, unconsumed, smoking article without performing the step of raising the temperature of the heating element to the second temperature. In other words, the user may consume more than one article before performing a cleaning step to thermally liberate organic materials from the heating element.

Thus, the temperature of the heating element may be raised to the first temperature a plurality of times before the step of raising the heating element to the second temperature is carried out.

The step of raising the temperature of the heating element to the second temperature to thermally liberate organic materials adhered to or deposited on the heating element may be termed a cleaning step.

The cleaning step may be actuated manually by a user. For example, a user may decide that the heating element needs to be cleaned and actuate a cleaning cycle in which the heating element is raised to the second temperature for a predetermined period of time. Actuation may be effected by pressing a button on the aerosol-generating device. Preferably, the cleaning cycle is terminated automatically after a predetermined or pre-programmed thermal cycle.

The aerosol-generating device may comprise a sensing means to determine whether or not a smoking article is engaged with the aerosol-generating device. If a smoking article is engaged, preferably the aerosol-generating means comprises control means, for example control software that acts to prevent the heating element being heated to the second temperature, thereby preventing the cleaning cycle from being actuated while a smoking article is engaged with the aerosol-generating device.

The cleaning step may be actuated automatically. For example, the aerosol-generating device may comprise means for detecting when the heating element is removed from contact with the aerosol-forming substrate, for example when a smoking article is removed from the device. When such an event is detected the heating element may automatically be cycled through a cleaning regime in which the heating element is heated to the second temperature for a period of time.

Control means associated with the aerosol-generating device may record the number of smoking articles consumed by a user and automatically trigger a cleaning cycle after a predetermined number of smoking articles have been consumed.

In some embodiments, an aerosol-generating device may comprise a battery to provide energy for heating the heating element. It may be advantageous if the aerosol-generating device is associated with a docking station for re-charging the battery and for other functions. It may be advantageous that a cleaning cycle is triggered when the aerosol-generating device is docked in a docking station. The docking station may be able to supply more power to the heating element than the aerosol-generating device, and the second temperature may, therefore, be higher. A higher second temperature may result in a more efficient or faster cleaning process.

In one aspect the specification may provide an aerosol-generating device comprising a heating element coupled to a controller. The controller is programmed to actuate the heating element through a first thermal cycle in which the temperature of the heating element is raised to a first temperature lower than about <NUM> degrees centigrade in order to produce an average temperature of <NUM> degrees centigrade over the heating element surface and a maximum temperature anywhere on the surface, i.e., a maximum localized temperature, of <NUM> degrees centigrade. This allows an aerosol to be formed from an aerosol-forming substrate disposed in proximity to the heating element without burning the aerosol-forming substrate. The controller is further programmed to actuate the heating element through a second thermal cycle in which the temperature of the heating element is raised to a second temperature higher than about <NUM> degrees centigrade in order to thermally liberate organic material deposited on the heating element.

Preferably the first temperature is greater than <NUM> degrees centigrade. For example the first temperature may be between <NUM> degrees centigrade and <NUM> degrees centigrade, or between <NUM> degrees centigrade and <NUM> degrees centigrade.

The aerosol-generating device may be any device for performing a method described above. For example, the aerosol-generating device may be any device comprising a controller programmed to perform a method described above or defined in the claims.

The controller may be housed by the aerosol-generating device. Alternatively the controller may be housed within a docking station that is couplable to the aerosol-generating device and thereby to the heating element of the aerosol-generating device.

In one aspect the specification may provide a kit comprising an aerosol-generating device suitable for receiving a smoking article and comprising a heating element, the kit further comprising instructions to clean the heating element by thermally liberating organic material adhered to or deposited on the heating element. The instructions may describe how to thermally liberate organic material, for example by heating. The instructions may describe how a user should activate an automatic cleaning cycle programmed into the aerosol-generating device.

A kit may comprise a docking station that is couplable to the aerosol-generating device. The instructions may describe how a user should activate an automatic cleaning cycle programmed into the docking station.

A kit may further comprise one or more smoking articles. A kit may include instructions to carry out any method described above or defined in the claims.

Features described in relation to one aspect of the specification may also be applicable to other embodiments discussed herein.

Exemplary embodiments will now be described with reference to the figures, in which;.

<FIG> illustrates a portion of an aerosol-generating device <NUM> according to a first embodiment. The aerosol-generating device <NUM> is engaged with a smoking article <NUM> for consumption of the smoking article <NUM> by a user.

The smoking article <NUM> comprises four elements, an aerosol-forming substrate <NUM>, a hollow tube <NUM>, a transfer section <NUM>, and a mouthpiece filter <NUM>. These four elements are arranged sequentially and in coaxial alignment and are assembled by a cigarette paper <NUM> to form a rod <NUM>. The rod has a mouth-end <NUM>, which a user inserts into his or her mouth during use, and a distal end <NUM> located at the opposite end of the rod to the mouth end <NUM>. Elements located between the mouth-end <NUM> and the distal end <NUM> can be described as being upstream of the mouth-end or, alternatively, downstream of the distal end.

When assembled, the rod <NUM> is <NUM> millimetres long and has a diameter of <NUM> millimetres.

The aerosol-forming substrate <NUM> is located upstream of the hollow tube <NUM> and extends to the distal end <NUM> of the rod <NUM>. The aerosol-forming substrate comprises a bundle of crimped cast-leaf tobacco wrapped in a filter paper (not shown) to form a plug. The cast-leaf tobacco includes additives, including glycerine as an aerosol-forming additive.

The hollow tube <NUM> is located immediately downstream of the aerosol-forming substrate <NUM> and is formed from a tube of cellulose acetate. The tube <NUM> defines an aperture having a diameter of <NUM> millimetre. One function of the hollow tube <NUM> is to locate the aerosol-forming substrate <NUM> towards the distal end <NUM> of the rod <NUM> so that it can be contacted with a heating element. The hollow tube <NUM> acts to prevent the aerosol-forming substrate <NUM> from being forced along the rod towards the mouth-end <NUM> when a heating element is inserted into the aerosol-forming substrate <NUM>.

The transfer section <NUM> comprises a thin-walled tube of <NUM> millimetres in length. The transfer section <NUM> allows volatile substances released from the aerosol-forming substrate <NUM> to pass along the rod <NUM> towards the mouth end <NUM>. The volatile substances may cool within the transfer section to form an aerosol.

The mouthpiece filter <NUM> is a conventional mouthpiece filter formed from cellulose acetate, and having a length of <NUM> millimetres.

The four elements identified above are assembled by being tightly wrapped within a cigarette paper <NUM>. The paper in this specific embodiment is a standard cigarette paper having standard properties or classification. The paper in this specific embodiment is a conventional cigarette paper. For example, the paper may be a porous material with a non-isotropic structure comprising cellulose fibers (crisscross s of fibers, interlinked by H-bonds), fillers and combustion agents. The filler agent may be CaCO3 and the burning agents can be one or more of the following: K/Na citrate, Na acetate, MAP (mono-ammonium phosphate), DSP (disodium phosphate). The final composition per squared meter may be approximately <NUM> fiber + <NUM> Calcium carbonate, + <NUM> burning additive. The porosity of the paper may be between <NUM> to <NUM> coresta. The interface between the paper and each of the elements locates the elements and defines the rod <NUM> of the smoking article <NUM>.

The interface between the paper and each of the elements locates the elements and defines the rod <NUM> of the smoking article <NUM>. Although the specific embodiment described above and illustrated in <FIG> has five elements assembled in a cigarette paper, it will now be clear to one of ordinary skill in the art that a smoking article according to the embodiments discussed here may have additional elements and these elements may be assembled in an alternative cigarette wrapper or equivalent. Likewise, a smoking article may have fewer elements. Moreover, if will now be apparent to one of ordinary skill in the art that various dimensions for the elements discussed in relation to the various embodiments discussed here are merely exemplary, and that suitable, alternative dimensions for the various elements may be chosen without deviating from the spirit of the embodiments discussed herein.

The aerosol-generating device <NUM> comprises a sheath <NUM> for receiving the smoking article <NUM> for consumption. A heating element <NUM> is located within the sheath <NUM> and positioned to engage with the distal end <NUM> of the smoking article. The heating element <NUM> is shaped in the form of a blade terminating in a point <NUM>.

As the smoking article <NUM> is pushed into the sheath <NUM> the point <NUM> of the heating element <NUM> engages with the aerosol-forming substrate <NUM>. By applying a force to the smoking article, the heating element <NUM> penetrates into the aerosol-forming substrate <NUM>. Once properly located, further penetration is prevented as the distal end <NUM> of the smoking article <NUM> abuts an end wall <NUM> of the sheath <NUM>, which acts as a stop.

When the smoking article <NUM> is properly engaged with the aerosol-generating device <NUM>, the heating element <NUM> has been inserted into the aerosol-forming substrate <NUM>.

<FIG> illustrates a heating element <NUM> as comprised in the aerosol-generating device <NUM> of <FIG> in greater detail. The heating element <NUM> is substantially blade-shaped. That is, the heating element has a length that in use extends along the longitudinal axis of a smoking article engaged with the heating element, a width and a thickness. The width is greater than the thickness. The heating element <NUM> terminates in a point or spike <NUM> for penetrating a smoking article <NUM>. The heating element comprises an electrically insulating substrate <NUM>, which defines the shape of the heating element <NUM>. The electrically insulating material may be, for example, alumina (Al<NUM>O<NUM>), stabilized zirconia (ZrO<NUM>). It will now be apparent to one of ordinary skill in the art that the electrically insulating material may be any suitable electrically insulating material and that many ceramic materials are suitable for use as the electrically insulating substrate.

Tracks <NUM> of an electrically conductive material are plated on a surface of the insulating substrate <NUM>. The tracks <NUM> are formed from a thin layer of platinum. Any suitable conductive material may be used for the tracks, and the list of suitable materials includes many metals, including gold, that are well known to the skilled person. One end of the tracks <NUM> is coupled to a power supply by a first contact <NUM>, and the other end of the tracks <NUM> is coupled to a power supply by a second contact <NUM>. When a current is passed through the tracks <NUM>, resistive heating occurs. This heats the entire heating element <NUM> and the surrounding environment. When a current passing through the tracks <NUM> of the heating element <NUM> is switched off, there is no resistive heating and the temperature of the heating element <NUM> is swiftly lowered.

Heater element <NUM> also includes collar <NUM>. The collar <NUM> may be formed of a suitable material that allows for conduction of electricity, so long as the design of the collar <NUM> is also selected to minimize resistive heating. In one embodiment, when the tracks <NUM> are formed of platinum or a platinum alloy, the collar <NUM> may be formed of gold or silver, or an alloy including either. Because of the difference in the electrical resistivity of the collar <NUM> material, less heat is generated over the collar area and the collar <NUM> sees a lower average temperature than the portion of heater element <NUM> including tracks <NUM>. In another embodiment, the collar <NUM> may be formed of an insulating material, such as a ceramic or other appropriate insulator.

Collar <NUM> provides a cold zone as compared to the average surface temperature of the portion of heater element <NUM> that includes tracks <NUM>. For example, the average temperature of the cold zone may be greater than <NUM> degrees centigrade cooler than the average surface temperature of the portion of heater element <NUM> including the tracks <NUM> during operation. Including the collar <NUM> may provide a number of benefits including that it reduces the temperature seen by any on-board electronics. In addition, collar <NUM> protects against the melting or degradation of various portions of device <NUM>, when materials such as plastic are used in the device. The collar also reduces condensation at the distal end of the device because such aerosol is cooled as it passes over the collar <NUM>. This reduction of condensation seen by electronics (not show) and contacts <NUM> and <NUM> included in the device <NUM> helps protect such elements.

The aerosol-generating device <NUM> comprises a power supply and electronics (not shown) that allow the heating element <NUM> to be actuated. Such actuation may be manually operated or may occur automatically in response to a user drawing on the smoking article. When the heating element is actuated, the aerosol-forming substrate is warmed and volatile substances are generated or evolved. As a user draws on the mouth end of the smoking article <NUM>, air is drawn into the smoking article and the volatile substances condense to form an inhalable aerosol. This aerosol passes through the mouth-end <NUM> of the smoking article and into the user's mouth.

In a specific embodiment (schematically illustrated in <FIG>) an aerosol-generating device comprises a processor or controller <NUM> coupled to a heating element <NUM> to control heating of the heating element. The controller <NUM> is programmed to actuate the heating element through a first thermal cycle in which the temperature of the heating element is raised to a first temperature of <NUM> degrees centigrade. This allows the formation of an aerosol from an aerosol-forming substrate disposed in proximity to the heating element. The controller is further programmed to actuate the heating element through a second thermal cycle in which the temperature of the heating element is raised to a second temperature of <NUM> degrees centigrade for a period of <NUM> seconds. This allows organic material deposited on the heating element to decompose or pyrolyse.

A specific embodiment of a method of using an aerosol-generating device will now be described with reference to <FIG> and <FIG> is a flow diagram setting out the steps carried out in an embodiment of the inventive method.

Step <NUM> - (Reference numeral <NUM> in <FIG>): A heating element <NUM> of an aerosol-generating device <NUM> is brought into contact with an aerosol-forming substrate <NUM> contained within a smoking article <NUM>. In order to achieve this, the smoking article <NUM> is inserted into a sheath <NUM> of the aerosol-generating device <NUM>. A heating element <NUM> is located within the sheath <NUM>, and projects from a bottom surface <NUM> of the sheath <NUM> such that it may be inserted into any smoking article that is received in the sheath. As the smoking article <NUM> is slid into the sheath <NUM>, a tip or point <NUM> of the heating element <NUM> contacts a distal end <NUM> of the smoking article. Further movement of the smoking article towards the bottom end <NUM> of the sheath causes the heating element <NUM> to penetrate into an aerosol-forming substrate located at the distal end <NUM> of the smoking article <NUM>. Once the smoking article has been fully inserted into the sheath, the distal end <NUM> of the smoking article abuts the bottom surface <NUM> of the sheath <NUM> and the heating element has reached maximum penetration.

Step <NUM>: (Reference numeral <NUM>) As the user draws or puffs on a mouth end <NUM> of the smoking article <NUM>, sensors in the aerosol-generating device <NUM> may detect this event. In the event of detecting a user puffing or drawing, a controller <NUM> sends instructions that activate the heating element to heat to a first temperature. A current is passed through conductive tracks <NUM> disposed on the heating element, which results in resistive heating of the heating element. The first temperature is <NUM> degrees centigrade, which is sufficient to liberate volatile compounds from the aerosol-forming substrate <NUM>. These volatile compounds condense to form an inhalable aerosol, which is drawn through the smoking article and into a user's mouth. Alternatively, a continuous heating may be used during operation of device <NUM> and detection of a user puffing or drawing may be used to trigger heating to compensate for any temperature drop of heater element <NUM> during the user puffing or drawing.

Step <NUM>: (Reference numeral <NUM>) When the user stops drawing or ends his puff on the mouth end <NUM> of the smoking article <NUM>, sensors in the aerosol-generating device detect this event. The controller <NUM> sends instructions to switch off the current passing through the heating element <NUM>. This stops the resistive heating of the tracks <NUM>, and the temperature of the heating element is swiftly lowered. As the temperature is lowered, aerosol stops being generated. Alternatively, during the continuous heating discussed above, the controller <NUM> may instead simply reduce the amount of energy seen during the user puffing or drawing, based on a desired set point temperature.

If the aerosol-forming substrate <NUM> still contains volatile compounds, the user may take another puff on the smoking article <NUM> and repeat step <NUM> (indicated by arrow <NUM> in <FIG>). Steps <NUM> and <NUM> may be repeated as often as necessary to consume the smoking article.

Step <NUM>: (Reference numeral <NUM>) When the user has finished with the smoking article <NUM>, for example when no more aerosol is generated on heating the aerosol-forming substrate <NUM>, the smoking article <NUM> is removed from the sheath <NUM> of the aerosol-generating apparatus <NUM>. This means that the heating element <NUM> is removed from contact with the aerosol-forming substrate <NUM>. Almost inevitably, the heating element <NUM> will have become soiled with some deposits or residues derived from the aerosol-forming substrate <NUM>. Such deposits may impair performance of the heating element. For example, deposits on the heating element may inhibit thermal transfer between the heating element and the aerosol-forming substrate. Deposits on a heating element may also inhibit temperature sensing when the heating element is utilized to sense temperature. Deposits on a heating element may also generate bitter compounds on repeated heating, which may impair the flavour of aerosols generated when consuming subsequent smoking articles.

If a user feels that the deposits on the heating element are at a sufficiently low level, he may decide to consume a further smoking article. In this case, steps <NUM> to <NUM> may be repeated. This is indicated by the arrow <NUM> in <FIG>.

Step <NUM>: (Reference numeral <NUM>) If a user believes that the heating element is in need of cleaning, he then presses a button (not shown) on the aerosol-generating device <NUM> that causes the controller to activate a cleaning cycle. During the heating cycle, current is passed through the tracks <NUM> of the heating element <NUM> to raise the temperature of the heating element to a second temperature. This second temperature is <NUM> degrees centigrade, a temperature at which deposits on the heating element can thermally degrade or pyrolyse. The heating element <NUM> is held at a temperature of <NUM> degrees centigrade for a period of <NUM> seconds to thermally liberate the organic compounds deposited on the heating element <NUM>.

<FIG> illustrates a portion of an aerosol-generating device. This figure illustrates a heating element <NUM> after use of the device to consume a smoking article. That is, <FIG> illustrates a heating element <NUM> of an aerosol-generating device after step <NUM> of the method described above. It can be seen that the heating element <NUM> is coated in organic deposits, which appear to be black in <FIG>.

<FIG> illustrates the same heating element as illustrated in <FIG> after the performance of a cleaning cycle as described by step <NUM> above. That is, the heating element <NUM> of <FIG> has been heated to a temperature of <NUM> degrees centigrade and held at that temperature for a period of <NUM> seconds. It can be seen that the black deposits visible in <FIG> have been removed and the heating element has been cleaned. In <FIG>, the heating element now has a shiny appearance where the organic deposits have been removed.

After cleaning, the aerosol-generating device is ready for use. Steps <NUM> to <NUM> may be repeated. This is indicated by the arrow <NUM> in <FIG>.

In the embodiment of a method described above, the step of heating the heating element to a first temperature to produce an aerosol occurred when the device detected a user taking a puff. In other embodiments, a user may manually activate the heating element to produce an aerosol.

In the embodiment of a method described above, the step of initiating a cleaning cycle was manually activated. In other embodiments, a cleaning cycle may be automatically triggered every time a smoking article is removed from the aerosol-generating device.

The aerosol-generating device <NUM> may be used in conjunction with a docking station (not illustrated). A docking station may be used, for example, to recharge batteries used to power the aerosol-generating device. <FIG> illustrates an embodiment of a method that may be used when the aerosol-generating device coupled to a docking station.

Steps <NUM> to <NUM> are the same as described above in relation to <FIG>. <FIG> uses the same reference numerals for steps that are the same as previously described.

Step <NUM>: (Reference numeral <NUM>) The aerosol-generating device <NUM> is coupled to a docking station (not shown) for receiving the device.

Step <NUM>: (Reference numeral <NUM>) When the aerosol-generating device <NUM> is detected, a controller activates a cleaning cycle. During the heating cycle, current is passed through tracks <NUM> of the heating element <NUM> to raise the temperature of the heating element to a second temperature. This second temperature is <NUM> degrees centigrade, a temperature at which deposits on the heating element can thermally degrade or pyrolyse. The heating element <NUM> is held at a temperature of <NUM> degrees centigrade for a period of <NUM> seconds to thermally liberate the organic compounds deposited on the heating element <NUM>. In one embodiment, the controller may be triggered from a signal from the docking station indicating that the device has not been cleaned after a predetermined number of uses, e.g., the user has contacted the heating element <NUM> with <NUM> or more times without performing a cleaning cycle. The controller <NUM> may then force the user to perform a cleaning cycle. For example, the user may be prohibited from activating heater element <NUM> unless a cleaning cycle is first performed. Controller <NUM> itself may contain instructions for locking the device <NUM> or the docking station may maintain information regarding use and provide the locking and unlocking instructions to the controller <NUM>.

Claim 1:
A method of using an aerosol-generating device (<NUM>) having a reusable heating element (<NUM>), the method comprising the steps of:
bringing the heating element (<NUM>) into proximity to an aerosol-forming substrate (<NUM>),
raising the temperature of the heating element (<NUM>) to a first temperature to heat the aerosol-forming substrate (<NUM>) sufficiently for an aerosol to be formed,
removing the heating element (<NUM>) from proximity to the aerosol-forming substrate (<NUM>), and
raising the temperature of the heating element (<NUM>) to a second temperature, higher than the first temperature, to thermally liberate organic materials adhered to or deposited on the heating element (<NUM>),
wherein the temperature of the heating element (<NUM>) is raised by inductive heating.