WO2015155289A1

WO2015155289A1 - Aerosol-generating device with helix-shaped heater

Info

Publication number: WO2015155289A1
Application number: PCT/EP2015/057725
Authority: WO
Inventors: Michel Thorens
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2014-04-10
Filing date: 2015-04-09
Publication date: 2015-10-15
Anticipated expiration: 2016-10-10

Abstract

An aerosol-generating device(200)for heating an aerosol-forming substrate(40,140) comprises a helix-shaped heater(10,110). The heater has a substantially longitudinal axis (15)extending between a first end(11),for penetrating the aerosol-forming substrate,and a second end(12),coupled to the aerosol-generating device. The heater is coupled to the aerosol-generating device at a freely-rotating joint(20,120)such that the heater can freely rotate around its longitudinal axis. The heater can be engaged with an aerosol-forming substrate by a linear motion of the aerosol-forming substrate relative to the heater.

Description

AEROSOL-GENERATING DEVICE WITH HELIX-SHAPED HEATER

The present specification relates to an aerosol-generating device for heating an aerosol-forming substrate, the aerosol-generating device comprising a helix-shaped heater.

Aerosol-generating 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 aerosol-generating articles is to reduce known harmful smoke constituents produced by the combustion and pyrolytic degradation of tobacco in conventional cigarettes. Typically in such heated aerosol-generating articles, an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol- forming substrate. During consumption of the aerosol-generating article, volatile compounds are released from the aerosol-forming substrate by heat transfer from the heat source and these compounds are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol that is inhaled by a consumer.

A number of prior art documents disclose aerosol-generating devices for consuming or smoking heated aerosol-generating articles. Such devices include, for example, heated aerosol-generating devices and electrically heated aerosol-generating devices. One advantage of such devices is that they significantly reduce sidestream smoke, while permitting the consumer to selectively suspend and reinitiate smoking.

Direct contact between a heating element and an aerosol-forming substrate may provide an efficient means for heating the aerosol-forming substrate to form an inhalable aerosol. In such a configuration, heat from a heater may be conveyed almost instantaneously to at least a portion of the aerosol-forming substrate when the heater is operated or actuated, and this may facilitate the rapid generation of an aerosol.

WO 2013/131763 discloses an apparatus configured to heat smokable material to volatilise at least one component of the smokable material. The apparatus includes an energy source, a heater and a heating chamber configured to receive smokable material. In one embodiment the apparatus comprises a spirally-shaped heat conducting element configured to screw into the smokable material.

The present specification provides an aerosol-generating device for heating an aerosol-forming substrate, a method of using an aerosol-generating device, and an aerosol-generating system comprising an aerosol-generating device and an aerosol- generating article.

Thus, the present specification may provide an aerosol-generating device for heating an aerosol-forming substrate comprising a heater for heating the aerosol-forming substrate. The heater has a substantially longitudinal axis extending between a first end for penetrating the aerosol-forming substrate and a second end coupled to the aerosol- generating device. The heater is coupled to the aerosol-generating device at a freely- rotating joint such that the heater can freely rotate about its longitudinal axis. At least a portion of the heater is helical or helix-shaped. At least a portion of the heater that is insertable into the aerosol-forming substrate is helical or helix-shaped.

As used herein, "helix-shaped" means at least a portion of the heater is helical. Other terms such as helicoidal and corkscrew-shaped are considered to fall within the term helix-shaped. Thus, a portion of the heater may be in the form of a wire that is twisted or formed into a helix, or a surface that is twisted or formed into a helicoid or thread.

Substantially the entire heater between its first end and its second end may be helix-shaped. Alternatively, only a portion of the length of the heater extending between its first end and its second end may be helix-shaped. The heater is shaped such that it can screw into an aerosol-forming substrate.

Preferably the heater can be inserted into an aerosol-forming substrate by moving it in a substantially linear motion along the longitudinal access of the heater relative to the aerosol-forming substrate. Preferably the shape of the heater is such that engagement between the heater and the aerosol-forming substrate causes the heater to rotate about its longitudinal access as the heater is inserted into the aerosol-forming substrate. Thus, relative linear movement between the aerosol-generating device and an aerosol-forming substrate allows the heater of the aerosol-generating device to screw into the aerosol- forming substrate. This can occur due to frictional engagement between the heater and the aerosol-forming substrate, and due to the freely-rotating joint that allows the heater to freely rotate around its longitudinal access.

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 aerosol-generating 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. In preferred embodiments, the aerosol-forming substrate is contained in an aerosol- generating article, for example a rod-shaped aerosol-generating article such as a heated aerosol-generating article or heated cigarette. The aerosol-generating article is of suitable size and shape to engage with the aerosol-generating device so as to bring the aerosol- forming substrate into contact with the heater.

An aerosol-forming substrate may comprise nicotine. An aerosol-forming substrate may comprise tobacco, for example may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol- forming substrate upon heating. In preferred embodiments an aerosol-forming substrate may comprise homogenised tobacco material, for example cast leaf tobacco.

As used herein, homogenised tobacco material refers to material formed by agglomerating particulate tobacco. Homogenised tobacco may be in the form of a sheet. Homogenised tobacco material may have an aerosol-former content of greater than 5% on a dry weight basis. Homogenised tobacco material may alternatively have an aerosol former content of between 5% and 30% by weight on a dry weight basis. Sheets of homogenised tobacco material may be formed by agglomerating particulate tobacco obtained by grinding or otherwise comminuting one or both of tobacco leaf lamina and tobacco leaf stems. Alternatively, or in addition, sheets of homogenised tobacco material may comprise one or more of tobacco dust, tobacco fines and other particulate tobacco byproducts formed during, for example, the treating, handling and shipping of tobacco. Sheets of homogenised tobacco material may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco; alternatively, or in addition, sheets of homogenised tobacco material may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and non-aqueous solvents and combinations thereof. In a particularly preferred embodiment, the aerosol-forming substrate comprises a gathered crimpled sheet of homogenised tobacco material. As used herein, the term 'crimped sheet' denotes a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, when the aerosol-generating article has been assembled, the substantially parallel ridges or corrugations extend along or parallel to the longitudinal axis of the aerosol-generating article. This advantageously facilitates gathering of the crimped sheet of homogenised tobacco material to form the aerosol-forming substrate. However, it will be appreciated that crimped sheets of homogenised tobacco material for inclusion in the aerosol-generating article may alternatively or in addition have a plurality of substantially parallel ridges or corrugations that are disposed at an acute or obtuse angle to the longitudinal axis of the aerosol-generating article when the aerosol-generating article has been assembled. In certain embodiments, the aerosol-forming substrate may comprise a gathered sheet of homogenised tobacco material that is substantially evenly textured over substantially its entire surface. For example, the aerosol-forming substrate may comprise a gathered crimped sheet of homogenised tobacco material comprising a plurality of substantially parallel ridges or corrugations that are substantially evenly spaced-apart across the width of the sheet.

In preferred embodiments, the aerosol-forming substrate is contained in an aerosol- generating article, for example a rod-shaped aerosol-generating article such as a cigarette. The aerosol-generating 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 aerosol-generating article may have a total length between approximately 30 mm and approximately 100 mm, for example between 35 mm and 55 mm, or between 40 mm and 50 mm, or about 45 mm. The aerosol-generating article may have an external diameter between approximately 5 mm and approximately 12 mm, for example between 6 mm and 8 mm or about 7 mm.

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

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.

In one embodiment, an aerosol-generating article for consumption by the aerosol- generating device has a total length of between 42 mm and 48 mm, for example approximately 45 mm. The aerosol-generating article may have an external diameter of between 6 mm and 8 mm, for example approximately 7 mm. Further, the aerosol-forming substrate may have a length of between 8 mm and 14 mm, for example approximately 10 mm or approximately 12 mm. Further, the diameter of the aerosol-forming substrate may be between approximately 5 mm and approximately 12 mm. The aerosol-generating article may comprise an outer paper wrapper. Further, the aerosol-generating article may comprise a separation between the aerosol-forming substrate and the filter plug. The separation may be approximately 18 mm, but may be in the range of approximately 5 mm to approximately 25 mm.

One advantage of a heater which is, at least in part, shaped as a helix is that it contacts an aerosol-forming substrate over a helical contact path rather than a linear contact path. Thus, there is greater contact between the heater and the aerosol-forming substrate over the length of an aerosol-forming substrate than would be the case if the heater was linear. Furthermore, a heater which is, at least in part, shaped as a helix has a greater radial distribution within an aerosol-forming substrate compared with a linear heater. Thus, heat exchange between the heater and an aerosol-forming substrate may be improved by using a heater at least in part shaped as a helix. Furthermore, the distribution of heat within an aerosol-forming substrate may be improved by use of a heater that is, at least in part, shaped as a helix.

The temperature of the heater may be raised to an operating temperature by any suitable method. For example, the temperature may be raised by conduction caused by contact with another heat source. The temperature may be 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 located on or within the heater. In one embodiment of a heater comprising a resistive track, the track may have a resistance between 0.5 and 5 ohms.

The heater may have a heater element comprising a rigid electrically insulating substrate with an electrically conductive track or wire disposed on its surface. A current may be passed through the track or wire to heat the heating element and the aerosol- forming substrate.

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

It is preferable that the aerosol-generating device further comprises electronic circuitry arranged to control the supply of current to the heater to control the temperature of the heater. The aerosol-generating device may also comprise means for sensing the temperature of the heating element. Preferably the heater is capable of heating an aerosol- forming substrate to a temperature of between 80 degrees centigrade and 375 degrees centigrade, for example between 100 degrees centigrade and 350 degrees centigrade.

A potential disadvantage of using a heater that is shaped as a helix, is the need to screw the heater into the aerosol-forming substrate. Some users may dislike the need to rotate an aerosol-forming substrate, for example an aerosol-generating article comprising an aerosol-forming substrate, onto a heater of an aerosol-generating device so that it may be heated. Some users may find it fiddly or difficult to do this, and the rotations required to screw the heater into the aerosol-forming substrate may result in damage to the aerosol- forming substrate, or the aerosol-generating article comprising the aerosol-forming substrate. Furthermore, after consumption of the aerosol-forming substrate, the user would need to unscrew the heater from the aerosol-forming substrate. It would be desirable to be able to obtain the benefits of using a heater at least part shaped as a helix without the requirement that a user rotates the heater relative to the aerosol-forming substrate in order to couple and decouple the heater from the aerosol-forming substrate.

The advantage of coupling the helix-shaped heater to the aerosol-generating device by means of a freely-rotating joint is that a relative linear motion between an aerosol- forming substrate and a heater allows a user to couple and decouple the heater from the aerosol-forming substrate. On penetration into the aerosol-forming substrate, friction between the heater and the aerosol-forming substrate, and the helical shape of the heater, produces a rotational force. Assuming that the aerosol-forming substrate is restrained from rotational motion as it is being held by a user, this rotational force causes the heater to rotate around its longitudinal access. As the heater penetrates more deeply into the aerosol-forming substrate, the heater rotates and screws, or worms, its way into the aerosol-forming substrate.

In preferred embodiments the aerosol-generating device may be an electric aerosol-generating device in which the heater is an electric heater. The aerosol-generating device may further comprise a power supply in electric communication with the heater for supplying energy to heat the aerosol-forming substrate. The power supply may be any suitable power supply, for example a DC voltage source. In one embodiment, the power supply is a Lithium-ion battery. Alternatively, the power supply may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium-Cobalt, a Lithium-Iron-Phosphate or a Lithium-Polymer battery.

It may be preferred that the power supply is electrically coupled to the heater through the freely-rotating joint. For example, the freely-rotating joint may comprise concentric electrical contacts to supply electric power to the heater.

The freely-rotating joint may be a rotating electrical interface such as a slip ring, otherwise known as a collector ring, rotary electrical contact, or electrical slip ring.

The pitch of the helix may vary between the first end of the heater and the second end of the heater. For example, the pitch of the helix towards the first end of the heater may be greater than the pitch of the helix further towards the second end of the heater.

The span of the helix may be different towards the first end of the heater compared to the second end of the heater. For example, the span of the helix may be lesser towards the first end of the heater and greater towards the second end of the heater.

The heater preferably comprises a helix-shaped heating element. A cross-section of the heater element may be circular, elliptic, oval, or substantially flat in shape. The heating element may be helicoidal in shape.

Advantageously the aerosol-generating device may comprise a substrate-receiving cavity for receiving the aerosol-forming substrate. The heater may then be disposed within the substrate-receiving cavity to penetrate the aerosol-forming substrate when the aerosol- forming substrate is received within the substrate-receiving cavity.

A method may be provided of using an aerosol-generating device, the aerosol- generating device having a helix-shaped heater. For example, a method of using any aerosol-generating device described herein may be provided. With reference to the aerosol-generating device described above, the method may comprise the steps of bringing an aerosol-forming substrate into proximity to the first end of the heater, inserting the heater into the aerosol-forming substrate, by relative movement of the second end of the heater towards the aerosol-forming substrate, supplying energy to the heater to heat the aerosol-forming substrate and form an inhalable aerosol, and removing the heater from the aerosol-forming substrate by relative movement of the second end of the heater away from the aerosol-forming substrate. Frictional engagement between the heater and the aerosol-forming substrate causes the heater to rotate in a first direction on inserting the heater into the aerosol-forming substrate and to rotate in a second direction on withdrawing the heater from the aerosol-forming substrate.

Advantageously, frictional engagement between the heater and the aerosol-forming substrate may cause the heater to be wiped as it is removed from the aerosol-forming substrate. This may provide the advantage that particles of the aerosol-forming substrate, and residues of an aerosol generated from the aerosol-forming substrate, may be wiped from the heater as it is removed from the aerosol-forming substrate due to the frictional engagement between the heater and the aerosol-forming substrate.

An aerosol-generated system may be provided, the system comprising an aerosol- generating device as described anywhere herein and a heated aerosol-generating article comprising an aerosol-forming substrate. Preferably, the heated aerosol-generating article is in the form of a rod comprising a plurality of elements, including the aerosol-forming substrate, assembled within a wrapper. Particularly preferably, the aerosol-forming substrate is itself in the form of a rod comprising a gathered sheet of aerosol-forming material, such as a gathered sheet of homogenised tobacco material. Specific embodiments of the invention will now be described with reference to the

Figures, in which;

Figure 1 illustrates a helix-shaped heater mounted to a freely-rotating joint for use in an aerosol-generating device;

Figure 2 illustrates the heater and freely-rotating joint of Figure 1 when about to commence engage with an aerosol-forming substrate within a substrate-receiving cavity of an aerosol-generating device; Figure 3 is a schematic illustration of an aerosol-generating article comprising an aerosol-forming substrate in engagement with a helix-shaped heater of an aerosol- generating device;

Figure 4 is a schematic illustration of a helix showing its pitch and span;

Figure 5 is a geometrical representation of a helicoid;

Figure 6 is a geometric representation of a helicoidal section.

Figure 1 illustrates a heater 10 for an aerosol-generating device mounted on a freely-rotating joint 20. The heater has a first end 1 1 terminating in a sharpened point for insertion into an aerosol-forming substrate, and a second end 12 mounted on the freely- rotating joint 20. A substantial portion of the heater 10 comprises a heating element 13 in the shape of a helix. The heater 10 may be coupled to an aerosol-generating device by means of the freely-rotating joint 20, such that the heater 10 can rotate around its longitudinal access 15. The helix defined by the heater 10 spirals around the longitudinal access of the heater 15.

Figure 2 illustrates a section of an aerosol-generating device showing a heater 10 as described in relation to Figure 1 mounted on a freely-rotating joint 20. The heater is disposed within a substrate-receiving cavity 30 defined by longitudinally extending walls 31 of the aerosol-generating device. The substrate-receiving cavity 30 has a substantially longitudinal access that is coincident with the longitudinal access of the heater 15. In use, an aerosol-generating substrate 40 is inserted into the substrate-receiving cavity 30 and brought into proximity with the first end 1 1 of the heater 10. Relative movement of the aerosol-forming substrate 40 towards the second end 12 of the heater 10 causes the first end of the heater 1 1 to penetrate the aerosol-forming substrate 40. Due to the helical shape of the heater, a rotational force is formed on the heater causing it to rotate around its longitudinal access 15. As the aerosol-forming substrate 40 is linearly pushed towards the second end 12 of the heater, the heater rotates about its longitudinal axis and screws or worms its way into the aerosol-forming substrate.

Figure 3 is a schematic illustration showing an aerosol-generating article 150, which comprises an aerosol-forming substrate 140, in operational engagement with a heater 1 10 within a substrate-receiving cavity 130 of an aerosol-generating device 200. The aerosol- generating article 150 is a heated aerosol-generating article comprising a mouthpiece filter 151 , an aerosol cooling element formed from a gathered sheet of polylactic acid 152, a spacer element 153 formed by a tube of cellulose acetate, and an aerosol-forming substrate 140 formed from a crimped and gathered sheet of homogenised tobacco material. The mouthpiece filter 151 , aerosol cooling element 152, spacer element 153, and aerosol-forming substrate 140 are assembled within a cigarette paper 155.

As described in relation to Figure 1 , the heater 1 10 is mounted at a freely-rotating joint 120. Electrical contacts 180 supply electrical power to a resistance heating track (not shown) on the surface of the heater 1 10.

The heating contacts on the freely-rotating joint may advantageously be concentric electrical contacts as illustrated in Figure 2. In other words, the electrical contacts may comprise a positive (or negative) electrical contact 81 disposed centrally on the freely- rotating joint, and a negative (or positive) electrical contact 82 disposed radially outside the central electrical contact 81 .

In use, electrical energy is supplied to the heater 10,1 10 to heat the aerosol-forming substrate 40,140 and form an inhalable aerosol. A user then may inhale the inhalable aerosol, for example by drawing through the mouthpiece filter 151 of an aerosol-generating article as illustrated in Figure 3.

Once the aerosol-forming substrate has been consumed, a linear movement away from the heater 10,1 10 will cause the heater to rotate in the opposite direction to that in which it rotated on penetrating the aerosol-forming substrate. The heater 10,1 10 then worms its way out of the consumed aerosol-forming substrate. Contact between the aerosol-forming substrate and the helix-shaped heater causes surfaces of the heater to be wiped clean of debris and residue that may have contaminated the heater 1 10.

The heater 10 may have a heating element in which the pitch is varied along the length of the heater. For example, the pitch of the helix may be greater towards the first end 1 1 of the heater than towards the second end 12 of the heater. Figure 4 illustrates a helix and shows the portion of the helix referred to as the span (A).

The heater may be defined by a helix having a span that varies between the first end 1 1 and the second end 12 of the heater. The portion of a helix defined as the span is illustrated on Figure 4 (B).

For the purposes of this specification, geometric shapes formed from helices such as helicoids are included in the definition of helix. Figure's 5 and 6 illustrate helicoidal surfaces that may be used to define a heater for an aerosol-generating device.

Claims

10 CLAIMS

1 . An aerosol-generating device (200) for heating an aerosol-forming substrate (40,140), the aerosol-generating device comprising:

a heater (10,1 10) having a substantially longitudinal axis (15) extending between a first end (1 1 ) for penetrating the aerosol-forming substrate and a second end (12) coupled to the aerosol-generating device, in which the heater (10, 1 10) is coupled to the aerosol- generating device at a freely-rotating joint (20, 120) such that the heater can freely rotate around its longitudinal axis, and in which at least a portion of the heater (13) is helix- shaped.

2. An aerosol-generating device according to claim 1 in which the heater is an electric heater, the aerosol-generating device further comprising a power supply in electric communication with the heater.

3. An aerosol-generating device according to claim 2 in which the power supply is electrically coupled to the heater through the freely-rotating joint.

4. An aerosol-generating device according to any preceding claim in which the freely- rotating joint is a slip ring.

5. An aerosol-generating device according to any preceding claim in which the pitch of the helix (A) towards the first end of the heater is different to the pitch of the helix towards the second end of the heater.

6. An aerosol-generating device according to any preceding claim in which the span of the helix (B) towards the first end of the heater is different to the span of the helix towards the second end of the heater.

7. An aerosol-generating device according to any preceding claim in which the heater comprises a helix-shaped heater element, a cross-section of the heater element being round, elliptic, oval, or substantially flat in shape.

8. An aerosol-generating device according to any preceding claim in which the heater is disposed within a substrate-receiving cavity (30,130) of the aerosol-generating device.

9. An aerosol-generating device according to any preceding claim in which

engagement between the heater and an aerosol-forming substrate causes the heater to rotate about its longitudinal axis when the heater is inserted into the aerosol-forming substrate.

10. A method of using an aerosol-generating device (200) according to any of claims 1 to 9 comprising the steps of,

bringing an aerosol-forming substrate (40,140) into proximity to the first end (1 1 ) of the heater (10,1 10),

inserting the heater into the aerosol-forming substrate by relative movement of the second 1 1 end (12) of the heater towards the aerosol-forming substrate, frictional engagement between the heater and the aerosol-forming substrate causing the heater to rotate in a first direction about its longitudinal axis (15),

supplying energy to the heater to heat the aerosol-forming substrate and form an inhalable aerosol, and

removing the heater from the aerosol-forming substrate by relative movement of the second end of the heater away from the aerosol-forming substrate, frictional engagement between the heater and the aerosol-forming substrate causing the heater to rotate in a second direction about its longitudinal axis.

1 1 . A method according to claim 10 in which the frictional engagement between the heater and the aerosol-forming substrate wipes the heater as it is removed from the aerosol-forming substrate.

12. An aerosol-generating system comprising an aerosol-generating device according to any of claims 1 to 9 and a heated aerosol-generating article (150) comprising an aerosol- forming substrate (140).

13. An aerosol-generating system according to claim 12 in which the heated aerosol- generating article is in the form of a rod comprising a plurality of elements assembled within a wrapper, one of the plurality of elements being the aerosol-forming substrate.

14. An aerosol-generating system according to claim 13 in which the aerosol-forming substrate is a rod comprising a gathered sheet of aerosol-forming material.

15. An aerosol-generating system according to claim 14 in which the aerosol-forming substrate is a rod comprising a gathered sheet of homogenised tobacco material.