Aerosol-generating system comprising internal and external heater

Abstract

An aerosol-generating system (100)(250) comprises an aerosol-generating article (102)(252), an aerosol-generating device (10)(200)(300)(400) and an internal heater (114)(214). The aerosol-generating article (102)(252) comprises: an aerosol-generating section (104) comprising an aerosol-generating substrate comprising at least 5 percent by weight of non-tobacco botanical material, on a dry weight basis. The aerosol-generating device (10)(200)(300)(400) comprises: a chamber (16) for receiving at least a portion of the aerosol-generating section (104) of the aerosol-generating article (102)(252); an external heater (28)(333) extending around at least a portion of the chamber (16); and control circuitry (40). The internal heater (114)(214) is arranged inside at least part of the aerosol-generating section (104) when the aerosol-generating article (102)(252) is received within the chamber. The control circuitry (40) is configured to heat the internal heater (114)(214) and the external heater (28)(333) during a heating cycle comprising a first phase and a second phase subsequent to the first phase. The control circuitry (40) is configured to heat the internal heater (114)(214) to a temperature greater than a temperature of the external heater (28)(333) during the first phase, and to heat the external heater (28)(333) to a temperature greater than a temperature of the internal heater (114)(214) during the second phase. The control circuitry (40) is configured to, during the first phase, heat the external heater (28)(222) to or maintain the external heater at a temperature above 50 degrees Celsius. The control circuitry (40) is configured to heat at least one of the internal heater (114)(214) and the external heater (28)(333) to a maximum temperature of no more than 350 degrees Celsius during the heating cycle.

Description

[0001] P / 91045.W001

[0002] -1-

[0003] AEROSOL-GENERATING SYSTEM COMPRISING INTERNAL AND EXTERNAL HEATER

[0004] The present disclosure relates to an aerosol-generating system comprising an aerosolgenerating article, an external heater, and an internal heater.

[0005] A typical aerosol-generating system comprises an aerosol-generating device and an aerosol-generating article comprising an aerosol-generating substrate. In use, the aerosolgenerating device is arranged to heat a heating element that is positioned near, or in contact with, the aerosol-generating substrate which causes the aerosol-generating substrate to heat up and release volatile compounds. These volatile compounds are then entrained in air that is drawn through the aerosol-generating article. As the volatile compounds cool, they condense to form an aerosol that can be inhaled by a consumer.

[0006] Some known aerosol-generating devices comprise an external heater for heating the aerosol-generating substrate from outside the aerosol-generating substrate. However, using an external heater to heat an inner portion of the aerosol-generating substrate sufficiently to form an aerosol may require heating the external heater to a sufficiently high temperature that there is a risk of the external heater overheating or burning the outer portion of the aerosol-generating substrate close to the external heater. Therefore, the use of an external heater typically leads to an inner portion of the aerosol-generating substrate, furthest from the external heater during use, not being heated to a sufficiently high temperature to form an aerosol. This means that the inner portion of the aerosol-generating substrate is typically wasted.

[0007] Some known aerosol-generating devices comprise an internal heater for heating the aerosol-generating substrate from within the aerosol-generating substrate. However, using an internal heater to heat an outer portion of the aerosol-generating substrate sufficiently to form an aerosol may require heating the internal heater to a sufficiently high temperature that there is a risk of the internal heater overheating or burning an inner portion of the aerosol-generating substrate close to the internal heater. Therefore, the use of an internal heater typically leads to an outer portion of the aerosol-generating substrate, furthest from the internal heater during use, not being heated to a sufficiently high temperature to form an aerosol. This means that the outer portion of the aerosol-generating substrate is typically wasted.

[0008] In some known aerosol-generating articles for use with aerosol-generating devices comprising an internal heater, the aerosol-generating substrate comprises a tobacco-containing substrate, such as a gathered sheet of homogenised tobacco material. Some articles of this type may further comprise a flavourant that is delivered to the consumer during use of the article to provide a different sensory experience, for example, to enhance the flavour of the aerosol. A flavourant can be used to deliver a gustatory sensation (taste), an olfactory sensation (smell), or both a gustatory and an olfactory sensation to the consumer inhaling the aerosol. There can be difficulties involved in generating flavours from an aerosol-generating substrate which is heated rather than combusted. For example, the relatively high temperatures that are required in order to release a desired amount of nicotine from a homogenised tobacco material, as described above, may not be optimal for the flavour profile of certain flavourants. Flavourants commonly contain flavour compounds that have a relatively high volatility and heat sensitivity and the heating of such compounds to relatively high temperatures may result in loss of their pleasing flavour, as well as the potential generation of undesirable flavour characteristics and harmful or potentially harmful compounds (HPHCs).

[0009] It is an aim of the present invention to provide an aerosol-generating system that provides improved heating of an aerosol-generating substrate. It is a further aim of the present invention to provide an aerosol-generating system that provides improved flavour delivery from an aerosolgenerating substrate.

[0010] According to the present disclosure there is provided an aerosol-generating system comprising an aerosol-generating article, an aerosol-generating device, and an internal heater. The aerosol-generating article may comprise an aerosol-generating section comprising an aerosol-generating substrate. The aerosol-generating device may comprise a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article. The aerosol-generating device may comprise an external heater extending around at least a portion of the chamber. The aerosol-generating device may comprise control circuitry. The internal heater may be arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber.

[0011] According to the present disclosure there is provided an aerosol-generating system comprising an aerosol-generating article, an aerosol-generating device, and an internal heater. The aerosol-generating article comprises an aerosol-generating section comprising an aerosolgenerating substrate. The aerosol-generating device comprises a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article. The aerosolgenerating device comprises an external heater extending around at least a portion of the chamber. The aerosol-generating device comprises control circuitry. The internal heater is arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber.

[0012] According to the present disclosure, there is provided an aerosol-generating system. The aerosol-generating system may comprise an aerosol-generating article comprising an aerosolgenerating section. The aerosol-generating section may comprise an aerosol-generating substrate. The aerosol-generating substrate may comprise at least 5 percent by weight of nontobacco botanical material, on a dry weight basis. The aerosol-generating system may further comprise an aerosol-generating device. The aerosol-generating device may comprise a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article. The aerosol-generating device may comprise an external heater extending around at least a portion of the chamber. The aerosol-generating device may comprise control circuitry. The aerosol-generating system may further comprise an internal heater arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber. The control circuitry may be configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during a heating cycle.

[0013] According to the present invention there is provided an aerosol-generating system comprising an aerosol-generating article, an aerosol-generating device and an internal heater. The aerosol-generating article comprises: an aerosol-generating section comprising an aerosolgenerating substrate, wherein the aerosol-generating substrate comprises at least 5 percent by weight of non-tobacco botanical material, on a dry weight basis. The aerosol-generating device comprises: a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry. The internal heater is arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber. The control circuitry is configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during a heating cycle.

[0014] According to the present invention there is further provided an aerosol-generating system comprising an aerosol-generating article, an aerosol-generating device and an internal heater. The aerosol-generating article comprises: an aerosol-generating section comprising an aerosolgenerating substrate, wherein the aerosol-generating substrate comprises at least 5 percent by weight of non-tobacco botanical material, on a dry weight basis. The aerosol-generating device comprises: a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry. The internal heater is arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber. The control circuitry is configured to heat the internal heater to a maximum internal heater temperature during a heating cycle and the control circuitry is configured to heat the external heater to a maximum external heater temperature during the heating cycle, wherein the internal heater reaches the maximum internal heater temperature at a different time to the external heater reaching the maximum external heater temperature during the heating cycle.

[0015] According to the present invention there is further provided an aerosol-generating system comprising an aerosol-generating article, an aerosol-generating device and an internal heater. The aerosol-generating article comprises: an aerosol-generating section comprising an aerosolgenerating substrate, wherein the aerosol-generating substrate comprises at least 5 percent by weight of non-tobacco botanical material, on a dry weight basis. The aerosol-generating device comprises: a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry. The internal heater is arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber. The chamber defines a longitudinal direction along which the aerosol-generating article may be inserted into the chamber, wherein the external heater has a length extending in the longitudinal direction, wherein the internal heater has a length extending in the longitudinal direction, and wherein a ratio of the length of the internal heater to the length of the external heater is between 0.2 and 5.

[0016] According to the present invention there is further provided an aerosol-generating system comprising an aerosol-generating article, an aerosol-generating device and an internal heater. The aerosol-generating article comprises: an aerosol-generating section comprising an aerosolgenerating substrate, wherein the aerosol-generating substrate comprises at least 5 percent by weight of non-tobacco botanical material, on a dry weight basis. The aerosol-generating device comprises: a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry. The internal heater is arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber. The control circuitry is configured to determine when a user takes puff on the aerosol-generating system.

[0017] According to the present invention there is further provided an aerosol-generating system comprising: an aerosol-generating article, an aerosol-generating device and an internal heater. The aerosol-generating article comprises: an aerosol-generating section comprising an aerosolgenerating substrate, wherein the aerosol-generating substrate comprises at least 5 percent by weight of non-tobacco botanical material, on a dry weight basis. The aerosol-generating device comprises: a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry. The internal heater is arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber. The control circuitry is configured to heat the internal heater and the external heater during a heating cycle comprising a first phase and a second phase subsequent to the first phase. The control circuitry is configured to heat the internal heater to a temperature greater than a temperature of the external heater during the first phase, and to heat the external heater to a temperature greater than a temperature of the internal heater during the second phase. The control circuitry is configured to, during the first phase, heat the external heater to or maintain the external heater at a temperature above 50 degrees Celsius. The control circuitry is configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during the heating cycle.

[0018] As used herein, “aerosol-generating system” typically refers to the combination of an aerosol-generating device with an aerosol-generating substrate, where the aerosol-generating substrate is comprised in an aerosol-generating article. In an aerosol-generating system, the aerosol-generating substrate and the aerosol-generating device cooperate to generate an aerosol.

[0019] As used herein, the term “aerosol-generating article” is used to describe an article comprising an aerosol-generating substrate that is heated to generate an inhalable aerosol for delivery to a user.

[0020] As used herein, the term “aerosol-generating substrate” is used to describe a substrate comprising aerosol-generating material that is capable of releasing upon heating volatile compounds that can form an aerosol.

[0021] As used herein, the term “aerosol” is used to describe a dispersion of solid particles, or liquid droplets, or a combination of solid particles and liquid droplets, in a gas. The aerosol may be visible or invisible. The aerosol may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles, or liquid droplets, or a combination of solid particles and liquid droplets.

[0022] As used herein, the term “aerosol-generating device” is used to describe a device that interacts with the aerosol-generating substrate of an aerosol-generating article to generate an aerosol.

[0023] The aerosol-generating article has a proximal end through which, in use, an aerosol exits the aerosol-generating article for delivery to a user. The proximal end of the aerosol-generating article may also be referred to as the downstream end or mouth end of the aerosol-generating article. In use, a user draws directly or indirectly on the proximal end of the aerosol-generating article in order to inhale an aerosol generated by the aerosol-generating article.

[0024] The aerosol-generating article has a distal end. The distal end is opposite the proximal end. The distal end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article.

[0025] Components of the aerosol-generating article may be described as being upstream or downstream of one another based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article.

[0026] As used herein, the term “longitudinal” is used to describe the direction between the upstream end and the downstream end of the aerosol-generating article. In use, air is drawn through the aerosol-generating article in the longitudinal direction.

[0027] As used herein, the term “length” is used to describe the maximum dimension of the aerosolgenerating article or a component of the aerosol-generating article in the longitudinal direction.

[0028] As used herein, the term “transverse” is used to describe the direction perpendicular to the longitudinal direction. Unless otherwise stated, references to the “cross-section” of the aerosolgenerating article or a component of the aerosol-generating article refer to the transverse crosssection.

[0029] As used herein the term “width” is used to describe the maximum dimension of the aerosolgenerating article or a component of the aerosol-generating article in the transverse direction. Where the aerosol-generating article has a substantially circular cross-section, the width of the aerosol-generating article corresponds to the diameter of the aerosol-generating article. Where a component of the aerosol-generating article has a substantially circular cross-section, the width of the component of the aerosol-generating article corresponds to the diameter of the component of the aerosol-generating article.

[0030] As used herein, the term “thickness” is used to describe the maximum dimension of the aerosol-generating article or a component of the aerosol-generating article in a direction perpendicular to both the longitudinal direction and the transverse direction.

[0031] As used herein, the term “elongate” is used to describe a component or element having a length that is greater than the width and the thickness thereof. For example, the length of an elongate component or element may be at least twice the width thereof. An elongate component or element may have a width that is greater than the thickness thereof. For example, an elongate element may have a substantially rectangular cross-section or a substantially elliptical or oval circular cross-section. An elongate component or element may have a width that is substantially the same as the thickness thereof. For example, an elongate element may have a substantially square cross-section or a substantially circular cross-section.

[0032] As used herein, the term "hollow tubular element" is used to describe a generally cylindrical element having a lumen or cavity along a longitudinal axis thereof. The hollow tubular element may have a substantially circular, oval or elliptical cross-section. The lumen may have a substantially circular, oval or elliptical cross-section. In particular, the term "hollow tubular element" is used to describe an element defining at least one airflow conduit establishing an uninterrupted fluid communication between an upstream end of the hollow tubular element and a downstream end of the hollow tubular element.

[0033] In the context of the present invention, a hollow tubular element provides an unrestricted flow channel. This means that the hollow tubular element provides a negligible level of resistance to draw (RTD). As used herein, the term “negligible level of resistance to draw (RTD)” is used to describe a resistance to draw (RTD) of less than 1 mm H2O per 10 millimetres of length of the hollow tubular element, less than 0.4 mm H2O per 10 millimetres of length of the hollow tubular element, or less than 0.1 mm H2O per 10 millimetres of length of the hollow tubular element. The flow channel should therefore be free from any components that would obstruct the flow of air in a longitudinal direction. The flow channel may be substantially empty.

[0034] As used herein, the term “ventilation level” describes a volume ratio of the airflow admitted into the aerosol-generating article via the ventilation zone (ventilation airflow) and the total airflow leaving the downstream end of the aerosol-generating article. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to a user.

[0035] Unless otherwise stated, percentages by weight of components of the aerosol-generating substrate recited herein are based on the dry weight of the aerosol-generating substrate. Unless otherwise stated, percentages by weight of components of the tobacco material recited herein are based on the dry weight of the tobacco material.

[0036] Unless otherwise stated, averages values recited herein are arithmetic means.

[0037] Unless otherwise stated, the resistance to draw (RTD) of the aerosol-generating article or a component of the aerosol-generating article is measured in accordance with ISO 6565-2015 at a volumetric flow rate of 17.5 millilitres per second at the proximal end of the aerosol-generating article or the component thereof at a temperature of 22 degrees Celsius, a pressure of 101 kPa (760 Torr) and a relative humidity of 60%.

[0038] As used herein, the resistance to draw (RTD) per unit length of the aerosol-generating article or a component of the aerosol-generating article is equal to the resistance to draw (RTD) of the aerosol-generating article divided by the length of the aerosol-generating article or the resistance to draw (RTD) of the component divided by the length of the component, respectively.

[0039] The aerosol-generating system of the present invention provides an aerosol-generating article having an aerosol-generating substrate comprising non-tobacco botanical material.

[0040] In the aerosol-generating system of the present invention, the use of a lower temperature is particularly effective for heating the aerosol-generating substrate which includes non-tobacco botanical material. It is common for aerosol-generating substrates of aerosol-generating articles to be heated in aerosol-generating devices to relatively high temperatures, above 350 degrees Celsius. However, such temperatures may not be optimal for the flavour profile of non-tobacco botanical materials, which are both volatile and heat sensitive. When liquid flavourants are extracted from non-tobacco botanical materials, for example, by distillation, flavour compounds are often extracted as essential oils at temperature of between 60 degrees Celsius to 100 degrees Celsius, with certain flavour compounds extracted at even lower temperatures due to their high volatility and heat sensitivity. Heating non-tobacco botanical materials to temperatures such as 350 degrees Celsius may result in loss of their pleasing flavour, undesirable flavour characteristics and the formation of harmful and potentially harmful compounds (HPHCs).

[0041] As described above, the aerosol-generating systems of the invention are provided with a dual heater arrangement which enables lower temperatures to be used to heat the aerosolgenerating substrate whilst still providing a desirable amount of aerosol. According to the invention, the control circuitry of the aerosol-generating device is configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during a heating cycle. The lower temperatures are particularly suited for aerosol-generating substrate including non-tobacco botanical material. At lower temperatures, the pleasing flavours of the non-tobacco botanical material can be more effectively preserved and undesirable flavour characteristics can be minimised or eliminated. Furthermore, the formation of HPHCs from the aerosol-generating substrate can advantageously be reduced or eliminated.

[0042] In certain embodiments of the present invention, non-tobacco botanical materials can be selected for the aerosol-generating substrate which provide the desired physical properties for the aerosol-generating substrate but which have low or minimal impact on the sensorial properties of the aerosol generated from the material. The non-tobacco botanical materials therefore provide a relatively neutral or inert base material which can advantageously be combined with an active agent such as nicotine, as well as optional flavourants. In this way, the delivery of the active agent and optional flavourant can be more readily controlled compared to alternative aerosol-generating substrates in which the active agent and optional flavourants are generated from the plant materials themselves.

[0043] In some embodiments, the aerosol-generating substrates can advantageously be formed with a reduced (or zero) level of tobacco particles, which means that the levels of undesirable tobacco compounds in the aerosol are reduced whilst still maintaining an acceptable delivery of nicotine or other active agent.

[0044] The aerosol-generating articles of aerosol-generating systems according to the present invention include an aerosol-generating substrate which comprises non-tobacco botanical plant material.

[0045] The non-tobacco botanical material in the aerosol-generating substrate may be selected from rooibos, tea including black tea, apple fibre, rosehip seed, lemon balm stem, peppermint stem, chamomile, verbena, elderflower, oat herb, parsley stem, geranium, lime, kaffir lime, lemon myrtle, ambrette seed, tolu balsam, passion berry, timur berry, coffee and combinations thereof. In particularly preferred embodiments of the present invention, the non-tobacco botanical material comprises rooibos.

[0046] A non-tobacco botanical material or blend of non-tobacco botanical materials may be selected depending on the desired flavour. For example, non-tobacco botanical materials such as geranium, ambrette seed, tolu balsam, elderflower and chamomile may be selected to provide floral flavour notes. Non-tobacco botanical materials such as lime, kaffir lime and lemon myrtle may be selected to provide citrus flavour notes.

[0047] According to the invention, the aerosol-generating substrate comprises at least 5 percent by weight of the non-tobacco botanical material, on a dry weight basis. Preferably, the aerosolgenerating substrate comprises at least 15 percent by weight of the non-tobacco botanical material, more preferably at least 25 percent by weight of the non-tobacco botanical material, more preferably at least 40 percent by weight of the non-tobacco botanical material, more preferably at least 50 percent by weight of the non-tobacco botanical material, on a dry weight basis.

[0048] The aerosol-generating substrate preferably comprises less than or equal to 80 percent by weight of the non-tobacco botanical material, on a dry weight basis, more preferably less than or equal to 75 percent by weight of the non-tobacco botanical material, more preferably less than or equal to 70 percent by weight of the non-tobacco botanical material, more preferably less than or equal to 65 percent by weight of the non-tobacco botanical material, on a dry weight basis. For example, the aerosol-generating substrate may comprise between 5 percent by weight and 80 percent by weight of the non-tobacco botanical material, or between 5 percent by weight and 75 percent by weight of the non-tobacco botanical material, or between 5 percent by weight and 70 percent by weight of the non-tobacco botanical material, or between 5 percent by weight and 65 percent by weight of the non-tobacco botanical material, on a dry weight basis.

[0049] For example, the aerosol-generating substrate may comprise between 15 percent by weight and 80 percent by weight of the non-tobacco botanical material, or between 15 percent by weight and 75 percent by weight of the non-tobacco botanical material, or between 15 percent by weight and 70 percent by weight of the non-tobacco botanical material, or between 15 percent by weight and 65 percent by weight of the non-tobacco botanical material, on a dry weight basis.

[0050] For example, the aerosol-generating substrate may comprise between 25 percent by weight and 80 percent by weight of the non-tobacco botanical material, or between 25 percent by weight and 75 percent by weight of the non-tobacco botanical material, or between 25 percent by weight and 70 percent by weight of the non-tobacco botanical material, or between 25 percent by weight and 65 percent by weight of the non-tobacco botanical material, on a dry weight basis.

[0051] For example, the aerosol-generating substrate may comprise between 40 percent by weight and 80 percent by weight of the non-tobacco botanical material, or between 40 percent by weight and 75 percent by weight of the non-tobacco botanical material, or between 40 percent by weight and 70 percent by weight of the non-tobacco botanical material, or between 40 percent by weight and 65 percent by weight of the non-tobacco botanical material, on a dry weight basis.

[0052] For example, the aerosol-generating substrate may comprise between 50 percent by weight and 80 percent by weight of the non-tobacco botanical material, or between 50 percent by weight and 75 percent by weight of the non-tobacco botanical material, or between 50 percent by weight and 70 percent by weight of the non-tobacco botanical material, or between 50 percent by weight and 65 percent by weight of the non-tobacco botanical material, on a dry weight basis.

[0053] The aerosol-generating substrate may optionally comprise tobacco material in addition to the non-tobacco botanical material. However, preferably the level of tobacco particles is relatively low. The aerosol-generating substrate may comprise less than or equal to 20 percent by weight of tobacco material, or less than or equal to 10 percent by weight of tobacco material, or less than of equal to 5 percent by weight of tobacco material, or less than or equal to 2 percent by weight of tobacco material, or less than or equal to 1 percent by weight of tobacco material, on a dry weight basis.

[0054] In some preferred embodiments of the present invention, the aerosol-generating substrate is substantially free from tobacco, or free from tobacco.

[0055] The aerosol-generating substrate may further comprise one or more aerosol formers. Suitable aerosol formers for inclusion in the homogenised plant material are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, propylene glycol, 1 ,3-butanediol and glycerol; 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. Preferably, the aerosol former comprises one or more of glycerol and propylene glycol. The aerosol former may consist of glycerol or propylene glycol or of a combination of glycerol and propylene glycol.

[0056] Preferably, the aerosol-generating substrate has an aerosol former content of at least 10 percent by weight on a dry weight basis. More preferably, the aerosol-generating substrate has an aerosol former content of at least 12 percent by weight, more preferably at least 15 percent by weight, on a dry weight basis.

[0057] The aerosol-generating substrate preferably has an aerosol former content of less than or equal to 35 percent by weight on a dry weight basis. More preferably, the aerosol-generating substrate has an aerosol former content of less than or equal to 30 percent by weight, more preferably less than or equal to 25 percent by weight, more preferably less than or equal to 20 percent by weight, on a dry weight basis.

[0058] For example, the aerosol former content of the aerosol-generating substrate may be between 10 percent and 35 percent by weight, or between 12 percent and 35 percent by weight, or between 15 percent and 35 percent by weight.

[0059] For example, the aerosol former content of the aerosol-generating substrate may be between 10 percent and 30 percent by weight, or between 12 percent and 30 percent by weight, or between 15 percent and 30 percent by weight.

[0060] For example, the aerosol former content of the aerosol-generating substrate may be between 10 percent and 25 percent by weight, or between 12 percent and 25 percent by weight, or between 15 percent and 25 percent by weight.

[0061] For example, the aerosol former content of the aerosol-generating substrate may be between 10 percent and 20 percent by weight, or between 12 percent and 20 percent by weight, or between 15 percent and 20 percent by weight.

[0062] Preferably, the aerosol-generating substrate comprises glycerol as an aerosol former. For example, the aerosol-generating substrate may comprise between 10 percent and 35 percent by weight of glycerol, or between 12 percent and 30 percent by weight of glycerol, or between 15 percent and 25 percent by weight of glycerol, or between 15 percent and 20 percent by weight of glycerol, on a dry weight basis.

[0063] The aerosol-generating substrate may further comprise one or more active agents. Preferably, the aerosol-generating substrate further comprises exogenous nicotine.

[0064] As used herein with reference to the invention, the term “nicotine” is used to describe nicotine, a nicotine base or a nicotine salt. In embodiments in which the aerosol-generating substrate comprises a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

[0065] As used herein with reference to the invention, the term “exogenous” refers to any nicotine incorporated into the aerosol-generating substrate which is provided extrinsically from the tobacco material present in the aerosol-generating substrate. The exogenous nicotine is therefore a separate and distinct source of nicotine to the nicotine provided intrinsically within any tobacco material that is present.

[0066] The exogenous nicotine may be in the form of natural nicotine, or synthetic nicotine, or a combination of natural nicotine and synthetic nicotine.

[0067] The aerosol-generating substrate may have a total exogenous nicotine content of at least 0.5 percent by weight, at least 1 percent by weight, at least 1 .5 percent by weight, or at least 2 percent by weight, on a dry weight basis.

[0068] The aerosol-generating substrate may have a total exogenous nicotine content of less than or equal to 10 percent by weight, less than or equal to 8 percent by weight, less than or equal to 6 percent by weight, or less than or equal to 4 percent by weight, on a dry weight basis.

[0069] The aerosol-generating substrate may have a total exogenous nicotine content of between 0.5 percent by weight and 10 percent by weight, between 0.5 percent by weight and 8 percent by weight, between 0.5 percent by weight and 6 percent by weight, or between 0.5 percent by weight and 4 percent by weight, on a dry weight basis.

[0070] The aerosol-generating substrate may have a total exogenous nicotine content of between

[0071] 1 percent by weight and 10 percent by weight, between 1 percent by weight and 8 percent by weight, between 1 percent by weight and 6 percent by weight, or between 1 percent by weight and 4 percent by weight, on a dry weight basis.

[0072] The aerosol-generating substrate may have a total exogenous nicotine content of between 1 .5 percent by weight and 10 percent by weight, between 1.5 percent by weight and 8 percent by weight, between 1.5 percent by weight and 6 percent by weight, or between 1 .5 percent by weight and 4 percent by weight.

[0073] The aerosol-generating substrate may have a total exogenous nicotine content of between

[0074] 2 percent by weight and 10 percent by weight, between 2 percent by weight and 8 percent by weight, between 2 percent by weight and 6 percent by weight, or between 2 percent by weight and 4 percent by weight.

[0075] Alternatively or in addition, the aerosol-generating substrate may further comprise one or more flavourants. Suitable flavourants would be known to the skilled person. The one or more flavourants may comprise one or more of: one or more essential oils such as eugenol, peppermint oil and spearmint oil; one or both of menthol and eugenol; one or both of anethole and linalool.

[0076] The aerosol-generating substrate may have a flavourant content of at least 0.5 percent by weight, preferably at least 1 percent by weight, more preferably at least 2 percent by weight, on a dry weight basis.

[0077] The aerosol-generating substrate may have a flavourant content of less than or equal to 10 percent by weight, preferably less than or equal to 8 percent by weight, more preferably less than or equal to 5 percent by weight, on a dry weight basis. For example, the aerosol-generating substrate may have a flavourant content of between 0.5 percent and 10 percent by weight, or between 1 percent and 8 percent by weight, or between 2 percent and 5 percent by weight, on a dry weight basis.

[0078] The non-tobacco botanical material may be a particulate non-tobacco botanical material, a shredded non-tobacco botanical material or a homogenised non-tobacco botanical material.

[0079] In certain preferred embodiments of the invention, the aerosol-generating substrate comprises a plurality of beads or granules comprising non-tobacco botanical particles.

[0080] As used herein, the term “granule” refers to a discrete, solid particle formed of the aerosolgenerating substrate as defined above. The granule may have a regular or irregular shape.

[0081] As used herein, the term “bead” refers to a discrete, solid particle formed of the aerosolgenerating substrate as defined above and which has a rounded, typically spherical, form.

[0082] The beads or granules of aerosol-generating substrate preferably comprise non-tobacco botanical particles, aerosol former and exogenous binder. The beads or granules of aerosolgenerating substrate may optionally further comprise tobacco particles.

[0083] The aerosol former may be incorporated into the beads or granules at the levels defined above.

[0084] The inclusion of binder helps to agglomerate the non-tobacco botanical particles. The term “exogenous binder” refers to binder material that is added to the aerosol-generating substrate as a distinct component from any binder that is intrinsically present in the non-tobacco botanical particles.

[0085] Suitable exogenous binders for inclusion in the aerosol-generating substrate as described herein are known in the art and include, but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins; and combinations thereof. Preferably, the binder comprises guar gum, carboxymethyl cellulose (CMC) or a combination thereof.

[0086] Preferably, the beads or granules of aerosol-generating substrate comprise at least 0.5 percent by weight of exogenous binder, more preferably at least 0.7 percent by weight of exogenous binder, more preferably at least 0 / 8 percent by weight of exogenous binder, on a dry weight basis.

[0087] Preferably, the beads or granules of aerosol-generating substrate comprise less than or equal to 4 percent by weight of exogenous binder, more preferably less than or equal to 3 percent by weight of exogenous binder, more preferably less than or equal to 2 percent by weight of exogenous binder, on a dry weight basis.

[0088] Preferably, the beads or granules of aerosol-generating substrate further comprise exogenous nicotine. The exogenous nicotine may be incorporated at the levels defined above. The non-tobacco botanical particles in the beads or granules of aerosol-generating substrate may have an average particle size of at least 25 microns. Preferably, the non-tobacco botanical particles have an average particle size of at least 30 microns, more preferably at least 35 microns, more preferably at least 40 microns.

[0089] The non-tobacco botanical particles may have an average size of less than or equal to 250 microns. Preferably, the non-tobacco botanical particles have an average size of less than or equal to 200 microns, more preferably less than or equal to 180 microns, more preferably less than or equal to 160 microns, more preferably less than or equal to 140 microns.

[0090] The non-tobacco botanical particles may have a D90 value of less than or equal to 300 microns. This expression means that 90 percent of non-tobacco botanical particles in the aerosolgenerating substrate have a size of less than or equal to 300 microns. For a population of particles, the D90 value may be determined by analysing the particle size distribution. In more detail, looking at a particle size distribution curve, the D90 value can be determined by identifying the point on the curve below which 90 percent of the particles fall.

[0091] Preferably, the non-tobacco botanical particles have a D90 value of less than or equal to 275 microns. More preferably, the non-tobacco botanical particles have a D90 value of less than or equal to 250 microns. Even more preferably, the non-tobacco botanical particles have a D90 value of less than or equal to 200 microns.

[0092] The non-tobacco botanical particles may have a D90 value of at least 35 microns. Preferably, the plant particles have a D90 value of at least 40 microns. More preferably, the non- tobacco botanical particles have a D90 value of at least 45 microns. Even more preferably, the non-tobacco botanical particles have a D90 value of at least 50 microns.

[0093] The particle size distribution may be determined by laser diffraction. For example, the particle size distribution may be determined by laser diffraction using a Malvern Mastersizer 3000 laser diffraction particle size analyser in accordance with the manufacturer’s instructions.

[0094] Where the aerosol-generating substrate comprises plant particles from two or more different plants, the plant particles from each plant may have a different average size and particle size distribution to the plant particles from the other plant or plants. For example, where the aerosolgenerating substrate comprises tobacco particles and non-tobacco botanical particles, the D90 value of the non-tobacco particles may be higher than the D90 value of the tobacco particles.

[0095] The total weight of the plurality of beads or granules in each aerosol-generating article may be between 50 milligrams and 350 milligrams, or between 100 milligrams and 300 milligrams, or between 125 milligrams and 250 milligrams, or between 150 milligrams and 200 milligrams.

[0096] The bulk density of the plurality of beads or granules in the aerosol-generating article may be between 200 milligrams per cubic centimetre and 500 milligrams per cubic centimetre, or between 225 milligrams per cubic centimetre and 475 milligrams per cubic centimetre, or between 250 milligrams per cubic centimetre and 450 milligrams per cubic centimetre. The bulk density of the plurality of beads or granules is defined as the total weight of the plurality of beads or granules, divided by the volume of the space occupied by the plurality of beads or granules.

[0097] The mean diameter of the plurality of beads or granules may be between 0.5 millimetres and 10 millimetres, or between 0.5 millimetres and 8 millimetres, or between 0.5 millimetres and 6 millimetres, or between 0.5 millimetres and 4 millimetres, or between 0.5 millimetres and 2.5 millimetres, or between 0.75 millimetres and 10 millimetres, or between 0.75 millimetres and 8 millimetres, or between 0.75 millimetres and 6 millimetres, or between 0.75 millimetres and 4 millimetres, or between 0.75 millimetres and 2.5 millimetres, or between 1 millimetres and 10 millimetres, or between 1 millimetres and 8 millimetres, or between 1 millimetres and 6 millimetres, or between 1 millimetres and 4 millimetres, or between 1 millimetres and 2.5 millimetres, or between 1.5 millimetres and 10 millimetres, or between 1.5 millimetres and 8 millimetres, or between 1.5 millimetres and 6 millimetres, or between 1.5 millimetres and 4 millimetres or between 1.5 millimetres and 2.5 millimetres.

[0098] The mean diameter of the plurality of beads or granules is defined as the sum of the diameters of the plurality of beads or granules, divided by the total number of beads or granules. For the avoidance of doubt, as used herein with reference to the present invention, the term ‘diameter’ is used to describe the maximum dimension of a bead or granule. For beads having a substantially circular cross-section or a substantially spherical shape, the term diameter refers to the diameter of the circular cross-section or the diameter of the sphere respectively. However, where the beads or granules have a shape which is not substantially spherical, the term ‘diameter’ is used to refer to the maximum dimension of the bead or granule.

[0099] The beads or granules forming the aerosol-generating substrate may have any suitable shape. Where the aerosol-generating substrate is in the form of a plurality of granules, the granules may have a regular shape, such as cylindrical, or an irregular shape. The granules may be the same shape as each other, or the plurality of granules may alternatively comprise granules of different shapes.

[0100] In alternative embodiments of the present invention, the aerosol-generating substrate comprises a shredded non-tobacco botanical material. Optionally, the aerosol-generating substrate further comprises a shredded tobacco material.

[0101] As used herein, the term “shredded” describes a non-tobacco botanical material that is in the form of a plurality of shreds or strips. The individual strips or strands are typically elongate in form, with a length that is greater than the width and thickness.

[0102] In such embodiments, the aerosol-generating substrate is preferably in the form of cut filler. As used herein, the term “cut filler” is used to describe to a blend of shredded plant material, including the shredded non-tobacco botanical material and any shredded tobacco material. The cut width of the shredded non-tobacco botanical material may be between 0.3 millimetres and 2 millimetres, or between 0.4 millimetres and 1.75 millimetres, or between 0.5 millimetres and 1.5 millimetres, or between 0.6 millimetres and 1 millimetre.

[0103] The aerosol-generating substrate preferably comprises a shredded non-tobacco botanical material and an aerosol former. Preferably, the aerosol-generating substrate further comprises exogenous nicotine. The aerosol former and exogenous nicotine may be provided at the levels as defined above.

[0104] Preferably, the aerosol-generating substrate comprises a shredded non-tobacco botanical material loaded with exogenous nicotine. Particularly preferably, the aerosol-generating substrate comprises shredded rooibos loaded with nicotine. As set out above, the shredded non-tobacco botanical material provides an optimal carrier material for nicotine, which has the desired physical properties and generates only a very subtle or neutral flavour upon heating.

[0105] The bulk density of the aerosol-generating substrate comprising shredded non-tobacco botanical material may correspond to between 100 milligrams per cubic centimetre and 1000 milligrams per cubic centimetre, or between 200 milligrams per cubic centimetre and 900 milligrams per cubic centimetre, or between 300 milligrams per cubic centimetre and 800 milligrams per cubic centimetre, or between 400 milligrams per cubic centimetre and 700 milligrams per cubic centimetre or between 500 milligrams per cubic centimetre and 700 milligrams per cubic centimetre.

[0106] The bulk density of the aerosol-generating substrate is defined as the total weight of the aerosol-generating substrate divided by the volume of space occupied by the aerosol-generating substrate.

[0107] In alternative embodiments of the present invention, the aerosol-generating substrate comprises homogenised plant material comprising particles of non-tobacco botanical material. Optionally, the homogenised plant material may further comprise particles of tobacco material.

[0108] As used herein with reference to the invention, the term “homogenised plant material” denotes a material formed by agglomerating particulate plant material.

[0109] The homogenised plant material preferably further comprises one or more aerosol formers. The aerosol former may be provided at the levels as defined above.

[0110] Preferably, the homogenised plant material further comprises exogenous nicotine. The exogenous nicotine may be provided at the levels defined above.

[0111] Preferably, the homogenised plant material further comprises exogenous binder. Suitable exogenous binders are set out above in relation to the embodiments comprising beads and granules.

[0112] Preferably, the homogenised plant material comprises at least 2.5 percent by weight of exogenous binder, more preferably at least 3 percent by weight of exogenous binder, on a dry weight basis. Preferably, the homogenised plant material comprises less than or equal to 10 percent by weight of exogenous binder, more preferably less than or equal to 7.5 percent by weight of exogenous binder, more preferably less than or equal to 5 percent by weight of exogenous binder, on a dry weight basis.

[0113] For example, the homogenised plant material may comprise between 2 percent by weight and 10 percent by weight of exogenous binder, or between 2.5 percent by weight and 7.5 percent by weight of exogenous binder, or between 3 percent by weight and 5 percent by weight of exogenous binder, on a dry weight basis.

[0114] The homogenised plant material may comprise at least 2 percent by weight of additional fibres, on a dry weight basis. The inclusion of additional fibres helps to optimise the mechanical properties of the homogenised plant material, for example, to improve the tensile strength. The term “additional fibres” refers to exogenous fibres that are added to the homogenised plant material as a distinct component from any fibres that are intrinsically present in the non-tobacco plant particles or tobacco particles (where present).

[0115] Suitable exogenous fibres for inclusion in the homogenised plant material are known in the art and include but are not limited to: cellulose fibres; soft-wood fibres; hard-wood fibres; jute fibres and combinations thereof. Preferably, the additional fibres comprise cellulose fibres.

[0116] Prior to inclusion in the homogenised plant material, fibres may be treated by suitable processes known in the art including, but not limited to: mechanical pulping; refining; chemical pulping; bleaching; sulfate pulping; and combinations thereof. A fibre typically has a length greater than its width.

[0117] Suitable fibres typically have lengths of greater than 400 micrometres and less than or equal to 4 mm, preferably within the range of 0.7 mm to 4 mm.

[0118] Preferably, the homogenised plant material comprises at least 3 percent by weight of additional fibres, more preferably at least 4 percent by weight of additional fibres, on a dry weight basis.

[0119] Preferably, the homogenised plant material comprises less than or equal to 10 percent by weight of additional fibres, more preferably less than or equal to 8 percent by weight of additional fibres, more preferably less than or equal to 6 percent by weight of additional fibres, on a dry weight basis.

[0120] For example, the homogenised plant material may comprise between 2 percent by weight and 10 percent by weight of additional fibres, or between 3 percent by weight and 8 percent by weight of additional fibres, or between 4 percent by weight and 6 percent by weight of additional fibres, on a dry weight basis.

[0121] The non-tobacco botanical particles in the homogenised plant material preferably have a D90 value of at least 30 microns, more preferably at least 40 microns, more preferably at least 50 microns, more preferably at least 60 microns. Preferably, the non-tobacco botanical particles in the homogenised plant material have a D90 values of less than or equal to 150 microns, more preferably less than or equal to 120 microns, more preferably less than or equal to 100 microns, more preferably less than or equal to 80 microns.

[0122] For example, the non-tobacco botanical particles in the homogenised plant material may have a D90 values of between 30 microns and 150 microns, or between 40 microns and 120 microns, or between 50 microns and 100 microns, or between 60 microns and 80 microns.

[0123] Preferably, the aerosol-generating substrate is in the form of one or more sheets of homogenised plant material.

[0124] The one or more sheets as described herein may each have an average thickness of between 100 microns and 600 microns, preferably between 150 microns and 500 microns, preferably between 200 microns and 400 microns, and most preferably between 250 microns and 350 microns.

[0125] The one or more sheets as described herein may each individually have a grammage of between 100 grams per square metre and 300 grams per square metre, or between 150 grams per square meter metre and 250 grams per square metre, or between 150 grams per square meter and 200 grams per square metre.

[0126] The one or more sheets as described herein may each individually have a density of from 0.3 grams per cubic centimetre to 1 .3 grams per cubic centimetre, preferably from 0.4 grams per cubic centimetre to 1 .0 grams per cubic centimetre and more preferably from 0.5 grams per cubic centimetre to 0.9 grams per cubic centimetre.

[0127] The homogenised plant material may be produced by various processes including paper making, casting, dough reconstitution, extrusion or any other suitable process.

[0128] Some processes such as casting and paper making are more suitable for producing homogenised plant material in sheet form. The term “cast leaf” is used herein to refer to a product made by a casting process that is based on casting a slurry comprising non-tobacco plant particles (for example, the non-tobacco plant particles), aerosol former (for example, glycerol) and any other components of the homogenised plant material onto a supportive surface, such as a belt conveyor, drying the slurry and removing the dried sheet from the supportive surface. An example of the casting or cast leaf process is described in, for example, US-A-5,724,998 for making cast leaf tobacco. In a cast leaf process, particulate plant materials are produced by pulverizing, grinding, or comminuting parts of the plant.

[0129] Preferably, the homogenised plant material is produced by casting, that is to say, it may be in the form of cast leaf.

[0130] In a particularly preferred embodiment, the aerosol-generating substrate comprises at least 50 percent by weight of non-tobacco botanical material, on a dry weight basis, exogenous nicotine and one or more aerosol formers. As described above, the aerosol-generating articles of aerosol-generating systems according to the present invention comprises an aerosol-generating section comprising the aerosol-generating substrate defined above. Preferably, the aerosol-generating section comprises a rod of the aerosol-generating substrate. The rod of aerosol-generating substrate is preferably circumscribed by a wrapper.

[0131] The aerosol-generating section may further comprise an internal susceptor element within the aerosol-generating substrate. The internal susceptor element corresponds to the internal heater of the aerosol-generating system and it is arranged to heat the aerosol-generating substrate during use.

[0132] The internal susceptor element is preferably an elongate susceptor element which extends longitudinally through the aerosol-generating section. The length of the elongate susceptor element may be substantially the same as the length of the aerosol-generating section. The length of the elongate susceptor element may be less than the length of the aerosolgenerating section.

[0133] The internal susceptor element is described in more detail below.

[0134] As described above, the inclusion of non-tobacco botanical material in the aerosolgenerating substrate makes them particularly suitable for heating at a relatively low temperature, to optimise the release of flavours from the non-tobacco botanical material. Preferably, the internal heater and external heater of the aerosol-generating system are configured to heat the aerosol-generating substrate to a maximum temperature of 300 degrees Celsius, or a maximum temperature of 250 degrees Celsius, or a maximum temperature of 210 degrees Celsius.

[0135] The aerosol-generating section may have a length of less than or equal to 20 millimetres, less than or equal to 18 millimetres, less than or equal to 15 millimetres, less than or equal to 14 millimetres, or less or equal to than 13 millimetres.

[0136] The aerosol-generating section may have a length of at least 6 millimetres, at least 8 millimetres or at least 10 millimetres.

[0137] For example, the aerosol-generating section has a length of between 6 millimetres and 20 millimetres, or between 6 millimetres and 18 millimetres, or between 6 millimetres and 15 millimetres, or between 6 millimetres and 14 millimetres, or between 6 millimetres and 13 millimetres, or between 8 millimetres and 20 millimetres, or between 8 millimetres and 18 millimetres, or between 8 millimetres and 15 millimetres, or between 8 millimetres and 14 millimetres, or between 8 millimetres and 13 millimetres, or between 10 millimetres and 20 millimetres, or between 10 millimetres and 18 millimetres, or between 10 millimetres and 15 millimetres, or between 10 millimetres and 14 millimetres, or between 10 millimetres and 13 millimetres.

[0138] A ratio of the length of the aerosol-generating section to the length of the aerosolgenerating article may be less than 0.4, less than 0.35, or less than 0.3. A ratio of the length of the aerosol-generating section to the length of the aerosol-generating article may be at least 0.15, at least 0.2, at least 0.25, or at least 0.3.

[0139] For example, the ratio of the length of the aerosol-generating section to the length of the aerosol-generating article may be between 0.15 and 0.4, or between 0.2 and 0.35, or between 0.25 and 0.3, or between 0.3 and 0.4.

[0140] The aerosol-generating section preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article.

[0141] The “external diameter of the aerosol-generating section” may be calculated as the average of a plurality of measurements of the diameter of the aerosol-generating section taken at different locations along the length of the aerosol-generating section.

[0142] The aerosol-generating section may have an external diameter of at least 5 millimetres, at least 6 millimetres, or at least 7 millimetres.

[0143] The aerosol-generating section may have an external diameter of less than or equal to 12 millimetres, less than or equal to 10 millimetres, or less than or equal to 8 millimetres.

[0144] For example, the aerosol-generating section may have an external diameter from about 5 millimetres to 12 millimetres, or from 6 millimetres to 12 millimetres, or from about 7 millimetres to 12 millimetres, or from 5 millimetres to 12 millimetres, or from 6 millimetres to 10 millimetres, or from 7 millimetres to 10 millimetres, or from 5 millimetres to 8 millimetres, or from 6 millimetres to 8 millimetres, or from 7 millimetres to 8 millimetres.

[0145] Foe example, the aerosol-generating section may have an external diameter of less than about 7.5 millimetres. By way of example, the aerosol-generating section may an external diameter of about 7.2 millimetres.

[0146] The aerosol-generating article may have any desired shape. For example, the aerosolgenerating article may be substantially cylindrical.

[0147] The aerosol-generating article may have any desired transverse cross-section. For example, the aerosol-generating article may have a substantially circular, oval or elliptical transverse cross-section.

[0148] The aerosol-generating article may have any desired length. For example, the aerosolgenerating article may have a length of between 30 millimetres and 70 millimetres, between 35 millimetres and 65 millimetres, or between 40 millimetres and 60 millimetres.

[0149] The aerosol-generating article may have any desired width. For example, the aerosolgenerating article may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres.

[0150] The aerosol-generating article may include one or more additional components.

[0151] The aerosol-generating article of aerosol-generating systems according to the invention may further comprise an upstream section located upstream of the aerosol-generating section. The upstream section may comprise one or more upstream elements.

[0152] The upstream section may be adjacent to the aerosol-generating section. The upstream section may be located immediately upstream of the aerosol-generating section.

[0153] The upstream section may abut the aerosol-generating section.

[0154] The upstream section may be connected to the aerosol-generating section by means of a wrapper. The upstream section may be connected to the aerosol-generating section by means of a paper wrapper.

[0155] An upstream end of the aerosol-generating article may be defined by an upstream end of the upstream section.

[0156] The upstream section may have a length of at least 2 millimetres, at least 3 millimetres, or at least 4 millimetres.

[0157] The upstream section may have a length of less than or equal to 10 millimetres, less than or equal to 8 millimetres, or less than or equal to 6 millimetres.

[0158] For example, the upstream section may have a length of between 2 millimetres and 10 millimetres, between 3 millimetres and 8 millimetres, or between 4 millimetres and 6 millimetres.

[0159] For example, the upstream element may have a length of 5 millimetres.

[0160] The upstream section may be substantially cylindrical.

[0161] The upstream section may have a substantially circular, oval or elliptical transverse crosssection.

[0162] The upstream section may have an external diameter that is substantially the same as an external diameter of the aerosol-generating article.

[0163] The upstream section may have an external diameter of at least 5 millimetres, at least 6 millimetres, or at least 7 millimetres.

[0164] The upstream section may have an external diameter of less than or equal to 12 millimetres, less than or equal to 10 millimetres, or less than or equal to 8 millimetres.

[0165] For example, the upstream section may have an external diameter of between 5 millimetres and 12 millimetres, between 6 millimetres and 10 millimetres, or between 7 millimetres and 8 millimetres.

[0166] For example, the upstream section may have an external diameter of 7 millimetres or 7.1 millimetres.

[0167] The RTD of the upstream section may be at least 0 millimetres H2O, at least 0.1 millimetres H2O, at least 0.25 millimetres H2O, or at least 0.5 millimetres H2O.

[0168] The RTD of the upstream section may be less than or equal to 30 millimetres H2O, less than or equal to 20 millimetres H2O, less than or equal to 10 millimetres H2O, less than or equal to 5 millimetres H2O, or less than or equal to 2 millimetres H2O.

[0169] For example, the RTD of the upstream section may be between 0 millimetres H2O and 30 millimetres H2O, between 0.1 millimetres H2O and 20 millimetres H2O, between 0.25 millimetres H2O and 10 millimetres H2O, between 0.5 millimetres H2O and 5 millimetres H2O, or between 0.5 millimetres H2O and 2 millimetres H2O. The upstream section may have an RTD of less than or equal to 2 millimetres H2O per millimetre of length, less than or equal to 1.5 millimetres H2O per millimetre length, less than or equal to 1 millimetre H2O per millimetre of length, less than or equal to 0.5 millimetres H2O per millimetre of length, less than or equal to 0.3 millimetres H2O per millimetre of length, or less than or equal to 0.2 millimetres H2O per millimetre of length.

[0170] The combined RTD of the upstream section and the aerosol-generating section may be less than or equal to 30 millimetres H2O, less than or equal to 20 millimetres H2O, less than or equal to 15 millimetres H2O, less than or equal to 12 millimetres H2O, or less than or equal to 10 millimetres H2O.

[0171] Preferably, the upstream section comprises an upstream element.

[0172] The upstream element may be made of any suitable material or combination of materials for use in an aerosol-generating article. Examples of suitable materials include: ceramic materials; polymeric materials; filter materials; paper materials; and combinations thereof.

[0173] The upstream element may comprise a non-tubular segment of cellulose acetate tow. For example, the upstream element may comprise a cellulose acetate plug.

[0174] The upstream element may be a hollow cellulose acetate tube.

[0175] The upstream element may be a hollow cardboard tube.

[0176] The upstream element may be formed of a heat resistant material. For example, the upstream element may be formed of a material that resists temperatures of up to 350 degrees Celsius.

[0177] The upstream element may be circumscribed by a wrapper. The upstream element may be circumscribed by a paper wrapper. For example, the upstream element may be circumscribed by a plug wrap.

[0178] The upstream section may comprise a plurality of upstream elements.

[0179] The upstream section may comprise a combination of two or more upstream elements, which may have the same or a different form to each other.

[0180] The aerosol-generating article may comprise a downstream section located downstream of the aerosol-generating section.

[0181] The downstream section may be adjacent to the aerosol-generating section.

[0182] The downstream section may be located immediately downstream of the aerosolgenerating section.

[0183] The downstream section may abut the aerosol-generating section.

[0184] The downstream section may be connected to the aerosol-generating section by means of a wrapper. The downstream section may be connected to the aerosol-generating section by means of a paper wrapper.

[0185] A downstream end of the aerosol-generating article may be defined by a downstream end of the downstream section. The length of the downstream section may be at least 15 millimetres, at least 20 millimetres, at least 25 millimetres, or at least 30 millimetres.

[0186] The length of the downstream section may be less than or equal to 50 millimetres, less than or equal to 45 millimetres, less than 40 millimetres, or less than 35 millimetres.

[0187] For example, the downstream section may have a length of between 15 millimetres and 50 millimetres, between 20 millimetres and 45 millimetres, between 25 millimetres and 40 millimetres or between 30 millimetres and 35 millimetres.

[0188] The downstream section may be substantially cylindrical.

[0189] The downstream section may have a substantially circular, oval or elliptical transverse cross-section.

[0190] The downstream section may have an external diameter that is substantially the same as an external diameter of the aerosol-generating article.

[0191] The downstream section may have an external diameter of at least 5 millimetres, at least

[0192] 6 millimetres, or at least 7 millimetres.

[0193] The downstream section may have an external diameter of less than or equal to 12 millimetres, less than or equal to 10 millimetres, or less than or equal to 8 millimetres.

[0194] For example, the downstream section may have an external diameter of between 5 millimetres and 12 millimetres, between 6 millimetres and 10 millimetres, or between

[0195] 7 millimetres and 8 millimetres.

[0196] For example, the downstream section may have an external diameter of 7 millimetres or 7.1 millimetres.

[0197] The RTD of the downstream section may be at least 0 millimetres H2O, at least 1 millimetre H2O, at least 2 millimetres H2O, or at least 3 millimetres H2O.

[0198] The RTD of the downstream section may be less than or equal to 20 millimetres H2O, less than or equal to 15 millimetres H2O, less than or equal to 12 millimetres H2O, or less than or equal to 10 millimetres H2O.

[0199] For example, the RTD of the downstream section may be between 0 millimetres H2O and 20 millimetres H2O, between 1 millimetres H2O and 15 millimetres H2O, between 2 millimetres H2O and 12 millimetres H2O, or between 3 millimetres H2O and 10 millimetres H2O.

[0200] For example, the RTD of the downstream section may be 8 millimetres H2O.

[0201] The downstream section may comprise one or more of: a support element, an aerosolcooling element and a mouthpiece element.

[0202] The downstream section may comprise a support element located between the aerosolgenerating section and the downstream end of the aerosol-generating article.

[0203] The support element may be located immediately downstream of the aerosol-generating section.

[0204] An upstream end of the support element may abut the aerosol-generating section. The support element may have a length of at least 5 millimetres, at least 8 millimetres, or at least 10 millimetres.

[0205] The support element may have a length of less than or equal to 30 millimetres, less than or equal to 25 millimetres, or less than or equal to 22 millimetres.

[0206] For example, the support element may have a length of between 5 millimetres and 30 millimetres, or between 8 millimetres and 25 millimetres, or between 10 millimetres and 22 millimetres.

[0207] The support element may be substantially cylindrical.

[0208] The support element may have a substantially circular, oval or elliptical transverse crosssection.

[0209] The support element may have an external diameter that is substantially the same as an external diameter of the downstream section.

[0210] The support element may comprise a hollow tubular element. For example, the support element may comprise a hollow cellulose acetate tube. The hollow tubular element may define a longitudinal cavity providing an unrestricted flow channel.

[0211] The downstream section may comprise a mouthpiece element.

[0212] The downstream section may comprise a mouthpiece element.

[0213] The mouthpiece element may define a downstream end of the downstream section of the aerosol-generating article.

[0214] The mouthpiece element may extend to a downstream end of the aerosol-generating article.

[0215] The mouthpiece element may comprise a plug of porous material. For example, the mouthpiece element may comprise a cellulose acetate plug.

[0216] The mouthpiece element may comprise a mouth end cavity.

[0217] The mouth end cavity may be defined by a hollow tubular element provided at the downstream end of the mouthpiece element.

[0218] The mouth end cavity may be defined by a wrapper.

[0219] The mouthpiece element may have any desired shape. For example, the mouthpiece element may be substantially cylindrical.

[0220] The mouthpiece element may have any desired transverse cross-section. For example, the mouthpiece element may have a substantially circular, oval or elliptical transverse cross-section.

[0221] The length of the mouthpiece element may be at least 5 millimetres, at least 6 millimetres, or at least 7 millimetres.

[0222] The length of the mouthpiece element may less than or equal to 15 millimetres, less than or equal 12 millimetres, or less than or equal 10 millimetres.

[0223] For example, length of the mouthpiece element may be between 5 millimetres and 15 millimetres, or between 6 millimetres and 12 millimetres, or between 7 millimetres and 10 millimetres. The mouthpiece element may have an external diameter that is substantially the same as an external diameter of the downstream section.

[0224] The mouthpiece element may comprise a flavourant. For example, the mouthpiece element may comprise one or more capsules, beads or granules of a flavourant, or one or more flavour loaded threads or filaments.

[0225] The mouthpiece element may be circumscribed by wrapper. The mouthpiece element may be circumscribed by a paper wrapper. For example, the mouthpiece element may be circumscribed by a plug wrap.

[0226] The mouthpiece element may be unventilated such that air does not enter the aerosolgenerating article along the mouthpiece element.

[0227] The mouthpiece element may be connected to one or more of the upstream components of the aerosol-generating article by means of a tipping wrapper.

[0228] The downstream section may comprise an aerosol-cooling element located between the aerosol-generating section and the downstream end of the aerosol-generating article.

[0229] Where the aerosol-generating article comprises a mouthpiece element, the aerosol-cooling element may be located immediately upstream of the mouthpiece element.

[0230] Where the aerosol-generating article comprises a support element, the aerosol-cooling element may be located immediately downstream of the support element.

[0231] The aerosol-cooling element may comprise a hollow tubular element.

[0232] The hollow tubular element may define a longitudinal cavity providing an unrestricted flow channel.

[0233] The aerosol-cooling element may not substantially contribute to the overall resistance to draw (RTD) of the aerosol-generating article.

[0234] The resistance to draw (RTD) of the aerosol-cooling element may be less than or equal to 15 millimetres H2O, less than or equal to 12 millimetres H2O, less than or equal to 10 millimetres H2O, less than or equal to 8 millimetres H2O, or less than or equal to 5 millimetres H2O.

[0235] The resistance to draw (RTD) of the aerosol-cooling element may be 0 millimetres H2O.

[0236] The aerosol-cooling element may be a hollow cellulose acetate tube.

[0237] The aerosol-cooling element may be a hollow cardboard tube.

[0238] The aerosol-cooling element may have any desired shape. For example, the mouthpiece element may be substantially cylindrical.

[0239] The aerosol-cooling element may have any desired transverse cross-section. For example, the aerosol-cooling element may have a substantially circular, oval or elliptical transverse crosssection.

[0240] The aerosol-cooling element may have a length of at least 5 millimetres, at least 8 millimetres, or at least 10 millimetres.

[0241] The aerosol-cooling element may have a length of less than or equal to 30 millimetres, less than or equal to 25 millimetres, or less than or equal to 22 millimetres. For example, the aerosol-cooling element may have a length of between 5 millimetres and 30 millimetres, or between 8 millimetres and 25 millimetres, or between 10 millimetres and 22 millimetres.

[0242] Where the downstream section comprises a support element and an aerosol-cooling element, the aerosol-cooling element may have a length of less than or equal to 20 millimetres, less than or equal to 15 millimetres, less than or equal to 12 millimetres, or less than or equal to 10 millimetres.

[0243] For example, where the downstream section comprises a support element and an aerosolcooling element, the aerosol-cooling element may have a length of between 5 millimetres and 20 millimetres, or between 5 millimetres and 15 millimetres, or between 5 millimetres and 12 millimetres, or , or between 5 millimetres and 10 millimetres.

[0244] Where the downstream section comprises a support element and an aerosol-cooling element, the support element may have a length of less than or equal to 20 millimetres, less than or equal to 15 millimetres, less than or equal to 12 millimetres, or less than or equal to 10 millimetres.

[0245] For example, where the downstream section comprises a support element and an aerosolcooling element, the support element may have a length of between 5 millimetres and 20 millimetres, or between 5 millimetres and 15 millimetres, or between 5 millimetres and 12 millimetres, or , or between 5 millimetres and 10 millimetres.

[0246] The mouthpiece element may have an external diameter that is substantially the same as an external diameter of the downstream section.

[0247] The aerosol-cooling element may have an external diameter that is substantially the same as the external diameter of the aerosol-generating article.

[0248] The aerosol-generating section and any other components of the aerosol-generating article may be assembled within one or more wrappers to form the aerosol-generating article. For example, the aerosol-generating section and any other components of the aerosol-generating article may be assembled within one or more wrappers to form an elongate rod.

[0249] Suitable wrappers for use in aerosol-generating articles are known in the art and include, but are not limited to: cigarette papers; filter plug wraps; tipping papers; metallised papers; metal foils; and metal foil-paper laminates.

[0250] The aerosol-generating article may comprise a ventilation zone located between the aerosol-generating section and the downstream end of the aerosol-generating article.

[0251] Where the aerosol-generating article comprises an aerosol-cooling element, the aerosolcooling element may comprise a ventilation zone. Where the aerosol-cooling element is a hollow tubular element, the ventilation zone may extend through the peripheral wall of the hollow tubular element.

[0252] The ventilation zone typically comprises a plurality of perforations extending through the peripheral wall of the hollow tubular element. The ventilation zone may comprise at least one circumferential row of perforations. In some embodiments, the ventilation zone comprises two circumferential rows of perforations. For example, the perforations may be formed online during manufacturing of the aerosol-generating article. Each circumferential row of perforations may comprise from 8 to 30 perforations.

[0253] An aerosol-generating article of the aerosol-generating system of the present invention may have a ventilation level of at least 25 percent.

[0254] The term “ventilation level” is used throughout the present specification to denote a volume ratio between of the airflow admitted into the aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to the consumer.

[0255] The aerosol-generating article may have a ventilation level of at least 10 percent, at least 20 percent, at least 30 percent, or at least 40 percent.

[0256] The aerosol-generating article may have a ventilation level of less than or equal to 90 percent, less than or equal to 80 percent, less than or equal to 70 percent, or less than or equal to 60 percent.

[0257] For example, the aerosol-generating article may have a ventilation level between 10 percent and 90 percent, or between 20 percent and 80 percent, or between 30 percent and 70 percent, or between 40 percent and 60 percent.

[0258] An aerosol-generating article of the aerosol-generating system according to the invention may be assembled using known methods and machinery.

[0259] As described above, the aerosol-generating device of aerosol-generating systems according to the present invention comprises a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry.

[0260] The control circuitry may be configured to heat the internal heater to a temperature greater than a temperature of the external heater during a first phase, wherein the control circuitry is configured to heat the external heater to a temperature greater than a temperature of the internal heater during a second phase after the first phase. Advantageously, heating the internal heater to a greater temperature during the first phase and heating the external heater to a greater temperature during the second phase may facilitate generation of aerosol from the aerosolgenerating substrate over a longer period of time. For example, aerosol may be generated predominantly from an inner portion of the aerosol-generating substrate during the first phase and aerosol may be predominantly generated from an outer portion of the aerosol-generating substrate during the second phase.

[0261] The control circuitry may be configured to heat the internal heater to a maximum temperature. The control circuitry may be configured to heat the external heater to a maximum temperature. As used herein, the maximum temperature of a heater refers to the peak temperature reached at any location on the surface of the heater, at any time during a heating cycle. In other words, the maximum temperature of a heater is the maximum temperature reached at a location on the surface of the heater at any point during a heating cycle, relative to the temperatures reached at other locations on the surface of the heater during a heating cycle. As used herein, the maximum temperature of a heater does not refer to a peak average temperature reached across the surface of the heater during a heating cycle.

[0262] The maximum temperature of a heater may be determined in any suitable way and by any suitable means. For example, the maximum temperature of a heater may be determined by initially determining a hot-spot location on the surface of the heater, and subsequently determining the maximum temperature reached at the hot-spot location during a heating cycle. As used herein, the hot-spot location refers to the location on the surface of the heater that reaches the highest temperatures during a heating cycle. The determination of the hot-spot location on the surface of the heater may be performed using a non-contact infrared sensor to map relative temperatures reached at locations across the surface of the heater during a heating cycle, and to identify the location at which the highest temperatures are reached. The subsequent determination of the maximum temperature reached at the hot-spot location may be performed using a thermocouple positioned on the surface of the heater at the hot-spot location to measure the temperatures reached at the hot-spot location during a heating cycle, and to identify the peak temperature reached at the hot-spot location.

[0263] The control circuitry may be configured to heat the internal heater to a maximum temperature of at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius during the first phase.

[0264] The control circuitry may be configured to heat the internal heater to a maximum temperature of no more than 420 degrees Celsius, no more than 400 degrees Celsius, no more than 375 degrees Celsius, no more than 350 degrees Celsius, no more than 325 degrees Celsius, or no more than 300 degrees Celsius during the first phase.

[0265] The control circuitry may be configured to heat the internal heater to a maximum temperature of between 100 and 420 degrees Celsius, or between 150 and 420 degrees Celsius, or between 100 and 400 degrees Celsius, or between 150 and 400 degrees Celsius, or between 150 and 350 degrees Celsius, or between 150 and 300 degrees Celsius during the first phase.

[0266] The control circuitry may be configured to heat the external heater to a maximum temperature of at least 30 degrees Celsius, at least 35 degrees Celsius, at least 40 degrees Celsius, at least 45 degrees Celsius, or at least 50 degrees Celsius during the first phase.

[0267] The control circuitry may be configured to heat the external heater to a maximum temperature of no more than 150 degrees Celsius, no more than 140 degrees Celsius, no more than 130 degrees Celsius, no more than 120 degrees Celsius, no more than 110 degrees Celsius, or no more than 100 degrees Celsius during the first phase. The control circuitry may be configured to heat the external heater to a maximum temperature of between 30 and 150 degrees Celsius, or between 35 and 140 degrees Celsius, or between 40 and 130 degrees Celsius, or between 45 and 120 degrees Celsius, or between 50 and 110 degrees Celsius, or between 50 and 100 degrees Celsius during the first phase.

[0268] The control circuitry may be configured to supply no power to the external heater during the first phase.

[0269] The control circuitry may be configured to heat the internal heater to a maximum temperature of at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius during the second phase.

[0270] The control circuitry may be configured to heat the internal heater to a maximum temperature of no more than 420 degrees Celsius, no more than 400 degrees Celsius, no more than 375 degrees Celsius, no more than 350 degrees Celsius, no more than 325 degrees Celsius, or no more than 300 degrees Celsius during the second phase.

[0271] The control circuitry may be configured to heat the internal heater to a maximum temperature of between 100 and 420 degrees Celsius, or between 150 and 420 degrees Celsius, or between 100 and 400 degrees Celsius, or between 150 and 400 degrees Celsius, or between 150 and 350 degrees Celsius, or between 150 and 300 degrees Celsius during the second phase.

[0272] The control circuitry may be configured to heat the external heater to a maximum temperature of at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius during the second phase.

[0273] The control circuitry may be configured to heat the external heater to a maximum temperature of no more than 400 degrees Celsius, no more than 375 degrees Celsius, no more than 350 degrees Celsius, no more than 325 degrees Celsius, or no more than 300 degrees Celsius during the second phase.

[0274] The control circuitry may be configured to heat the external heater to a maximum temperature of between 100 and 400 degrees Celsius, or between 150 and 400 degrees Celsius, or between 150 and 350 degrees Celsius, or between 150 and 300 degrees Celsius during the second phase.

[0275] The term “heating cycle” is used herein to refer to the heating of the aerosol-generating article by the aerosol-generating device starting from power being first supplied to at least one of the internal heater and the external heater and finishing when power supplied to both heaters has been terminated. A single heating cycle may also be referred to as a “single usage session” or a “single user experience”.

[0276] The control circuitry may be configured to heat the internal heater to an internal heater temperature during a heating cycle, wherein the control circuitry is configured to heat the external heater to an external heater temperature during the heating cycle, and wherein the control circuitry is configured to change a difference between the internal heater temperature and the external heater temperature during the heating cycle. Advantageously, changing a difference between the internal heater temperature and the external heater temperature during a heating cycle may facilitate reducing a time between the start of the heating cycle and generation of aerosol from the aerosol-generating substrate, and providing a relatively consistent delivery of aerosol during the heating cycle. For example, the difference between the internal heater temperature and the external heater temperature may be relatively large at the start of the heating cycle as a result of a high initial internal heater temperature to provide a rapid start of aerosol generation. Once aerosol generation has started, the internal heater temperature may be reduced and the external heater temperature may be increased to provide more even heating of the aerosol-generating substrate during the remainder of the heating cycle.

[0277] The control circuitry may be configured to increase a difference between the internal heater temperature and the external heater temperature during the heating cycle. The control circuitry may be configured to decrease a difference between the internal heater temperature and the external heater temperature during the heating cycle.

[0278] The control circuitry may be configured to increase or maintain a difference between the internal heater temperature and the external heater temperature during a first phase of the heating cycle and configured to decrease a difference between the internal heater temperature and the external heater temperature during a second phase of the heating cycle subsequent to the first phase.

[0279] The control circuitry may be configured to heat at least one of the internal heater and the external heater so that an average difference between the internal heater temperature and the external heater temperature during the first phase is at least 50 degrees Celsius, at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, at least 300 degrees Celsius, or at least 350 degrees Celsius.

[0280] The control circuitry may be configured to heat at least one of the internal heater and the external heater so that an average difference between the internal heater temperature and the external heater temperature during the first phase is between 100 degrees Celsius and 350 degrees Celsius, or between 150 degrees Celsius and 300 degrees Celsius, or between 100 degrees Celsius and 300 degrees Celsius.

[0281] The control circuitry may be configured to heat at least one of the internal heater and the external heater so that an average difference between the internal heater temperature and the external heater temperature during the second phase is no more than 200 degrees Celsius, no more than 150 degrees Celsius, no more than 100 degrees Celsius, no more than 50 degrees Celsius, no more than 25 degrees Celsius, or no more than 20 degrees Celsius.

[0282] The control circuitry may be configured to heat at least one of the internal heater and the external heater so that an average difference between the internal heater temperature and the external heater temperature during the second phase is between zero degrees Celsius and 150 degrees Celsius, or between zero degrees Celsius and 100 degrees Celsius, or between 20 degrees Celsius and 150 degrees Celsius, or between 20 degrees Celsius and 100 degrees Celsius.

[0283] The control circuitry may be configured to heat the internal heater and the external heater during a heating cycle, wherein the control circuitry is configured to start heating of the internal heater before starting heating of the external heater during the heating cycle. Advantageously, starting heating of the internal heater before heating of the external heat may facilitate reducing a time between the start of the heating cycle and generation of aerosol from the aerosolgenerating substrate. For example, the internal heater may be heated to a high initial temperature to provide a rapid start of aerosol generation. Once aerosol generation has started, the internal heater temperature may be reduced and heating of the external heater may be started to provide more even heating of the aerosol-generating substrate during the remainder of the heating cycle.

[0284] The control circuitry may be configured to start heating of the external heater after a predetermined time period has elapsed since starting heating of the internal heater. The control circuitry may be configured to start heating of the external heater after a predetermined number of puffs on the aerosol-generating system since starting heating of the internal heater. The control circuitry may be configured to start heating of the external heater after a predetermined time period has elapsed or after a predetermined number of puffs, whichever occurs first.

[0285] The predetermined time period may be at least 5 seconds, at least 10 seconds, at least 20 seconds, at least 30 seconds, at least 60 seconds, at least 90 seconds, at least 120 seconds, at least 180 seconds, or at least 240 seconds.

[0286] The predetermined time period may be no more than 300 seconds, no more than 240 seconds, no more than 180 seconds, no more than 120 seconds, no more than 90 seconds, no more than 60 seconds, or no more than 30 seconds.

[0287] The predetermined time period may be between 5 seconds and 240 seconds, or between 10 seconds and 180 seconds, or between 20 seconds and 120 seconds, or between 30 seconds and 120 seconds.

[0288] The predetermined time period may be at least 5 percent, at least 10 percent, at least 20 percent, at least 25 percent, at least 30 percent, at least 35 percent, at least 40 percent, or at least 45 percent of a total duration of the heating cycle.

[0289] The predetermined time period may be no more than 50 percent, no more than 45 percent, no more than 40 percent, no more than 35 percent, no more than 30 percent, no more than 25 percent, or no more than 20 percent of a total duration of the heating cycle.

[0290] The predetermined time period may be between 5 percent and 50 percent, or between 10 percent and 45 percent, or between 5 percent and 45 percent, or between 10 percent and 40 percent, or between 5 percent and 40 percent of a total duration of the heating cycle.

[0291] The predetermined number of puffs may be at least one puff, at least two puffs, at least three puffs, at least four puffs, or at least five puffs. The predetermined number of puffs may be no more than ten puffs, no more than nine puffs, no more than eight puffs, no more than seven puffs, no more than six puffs, or no more than five puffs.

[0292] The control circuitry may be configured to heat the internal heater to a maximum internal heater temperature, wherein the control circuitry is configured to heat the external heater to a maximum external heater temperature, and wherein the maximum external heater temperature is less than the maximum internal heater temperature. Advantageously, heating the internal heater to a greater maximum temperature than the external heater may facilitate more even heating of the aerosol-generating substrate. For example, heat generated by the internal heater may heat an inner portion of the aerosol-generating substrate to a desired temperature while only providing partial heating of an outer portion of the aerosol-generating substrate. Therefore, heating the external heater to a lower maximum temperature than the internal heater may provide sufficient additional heating of the outer portion of the aerosol-generating substrate without resulting in excessive heating of the internal portion of the aerosol-generating substrate.

[0293] The difference between the maximum internal heater temperature and the maximum external heater temperature may be at least 50 degrees Celsius, at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius.

[0294] The difference between the maximum internal heater temperature and the maximum external heater temperature may be no more than 350 degrees Celsius, no more than 300 degrees Celsius, no more than 250 degrees Celsius, no more than 200 degrees Celsius, no more than 150 degrees Celsius, or no more than 100 degrees Celsius.

[0295] The difference between the maximum internal heater temperature and the maximum external heater temperature may be between 50 degrees Celsius and 300 degrees Celsius, or between 50 degrees Celsius and 250 degrees Celsius, or between 50 degrees Celsius and 200 degrees Celsius, or between 50 degrees Celsius and 150 degrees Celsius, or between 100 degrees Celsius and 250 degrees Celsius, or between 100 degrees Celsius and 200 degree Celsius, or between 100 degrees Celsius and 150 degrees Celsius.

[0296] The maximum internal heater temperature may be at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius.

[0297] The maximum internal heater temperature may be no more than 420 degrees Celsius, no more than 400 degrees Celsius, no more than 375 degrees Celsius, no more than 350 degrees Celsius, no more than 325 degrees Celsius, or no more than 300 degrees Celsius.

[0298] The maximum internal heater temperature may be between 100 and 420 degrees Celsius, or between 150 and 420 degrees Celsius, or between 100 and 400 degrees Celsius, or between 150 and 400 degrees Celsius, or between 150 and 350 degrees Celsius, or between 150 and 300 degrees Celsius. The maximum external heater temperature may be at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius.

[0299] The maximum external heater temperature may be no more than 400 degrees Celsius, no more than 375 degrees Celsius, no more than 350 degrees Celsius, no more than 325 degrees Celsius, or no more than 300 degrees Celsius.

[0300] The maximum external heater temperature may be between 100 and 400 degrees Celsius, or between 150 and 400 degrees Celsius, or between 150 and 350 degrees Celsius, or between 150 and 300 degrees Celsius.

[0301] The control circuitry may be configured to heat the internal heater to a maximum internal heater temperature during a heating cycle, wherein the control circuitry is configured to heat the external heater to a maximum external heater temperature during the heating cycle, and wherein the internal heater reaches the maximum internal heater temperature at a different time to the external heater reaching the maximum external heater temperature during the heating cycle. Advantageously, heating the internal heater to a maximum internal heater temperature at a different time to heating the external heater to a maximum external heater temperature may facilitate the generation of aerosol from different portions of an aerosol-generating substrate at different times. Advantageously, this may facilitate the generation of aerosol over a longer time period.

[0302] The control circuitry may be configured to heat the internal heater and the external heater so that the internal heater reaches the maximum internal heater temperature a predetermined time period after the external heater reaches the maximum external heater temperature.

[0303] Preferably, the control circuitry is configured to heat the internal heater and the external heater so that the external heater reaches the maximum external heater temperature a predetermined time period after the internal heater reaches the maximum internal heater temperature.

[0304] The predetermined time period may be at least 5 seconds, at least 10 seconds, at least 20 seconds, at least 30 seconds, at least 60 seconds, at least 90 seconds, at least 120 seconds, at least 180 seconds, or at least 240 seconds.

[0305] The predetermined time period may be no more than 300 seconds, no more than 240 seconds, no more than 180 seconds, no more than 120 seconds, no more than 90 seconds, no more than 60 seconds, or no more than 30 seconds.

[0306] The predetermined time period may be between 5 seconds and 240 seconds, or between 10 seconds and 180 seconds, or between 20 seconds and 120 seconds, or between 30 seconds and 120 seconds.

[0307] The predetermined time period may be at least 5 percent, at least 10 percent, at least 20 percent, at least 25 percent, at least 30 percent, at least 35 percent, at least 40 percent, or at least 45 percent of a total duration of the heating cycle. The predetermined time period may be no more than 50 percent, no more than 45 percent, no more than 40 percent, no more than 35 percent, no more than 30 percent, no more than 25 percent, or no more than 20 percent of a total duration of the heating cycle.

[0308] The predetermined time period may be between 5 percent and 50 percent, or between 10 percent and 45 percent, or between 5 percent and 45 percent, or between 10 percent and 40 percent, or between 5 percent and 40 percent of a total duration of the heating cycle.

[0309] The chamber may define a longitudinal direction along which the aerosol-generating article may be inserted into the chamber, wherein the external heater has a length extending in the longitudinal direction, wherein the internal heater has a length extending in the longitudinal direction, and wherein a ratio of the length of the internal heater to the length of the external heater is between 0.2 and 5. Advantageously, a combination of an internal heater and an external heater having a ratio of lengths within this range may facilitate uniform heating of an aerosol-generating substrate of the aerosol-generating section in both the longitudinal direction and a width or radial direction perpendicular to the longitudinal direction.

[0310] The ratio of the length of the internal heater to the length of the external heater may be between 0.2 and 4, or between 0.2 and 3, or between 0.2 and 2, or between 0.3 and 1 .9, or between 0.4 and 1.9, or between 0.5 and 1.9, or between 0.6 and 1.8, or between 0.7 and 1 .7, or between 0.8 and 1 .6, or between 0.9 and 1.5, or between 1 and 1 .4, or between 1 .1 and 1 .3.

[0311] The control circuitry may be configured to determine when a user takes puff on the aerosolgenerating system. Advantageously, determining when a user takes a puff on the aerosolgenerating system may facilitate control of the aerosol-generating device by the control circuitry.

[0312] The control circuitry may be configured to control heating of at least one of the internal heater and the external heater based on the control circuitry determining that a user is taking a puff or has taken one or more puffs on the aerosol-generating system. For example, in embodiments and examples in which the control circuitry is configured to heat the internal heater and the external heater during a heating cycle, the progression of the heating cycle may be determined based on a cumulative number of puffs during the heating cycle. For example, the control circuitry may be configured so that the heating cycle lasts for a predetermined number of puffs. In embodiments and examples in which the heating cycle comprises a first phase and a second phase, the control circuitry may be configured so that one or both of the first phase and the second phase lasts for a predetermined number of puffs.

[0313] The aerosol-generating device may comprise a puff sensor, wherein the control circuitry is configured to determine when a user takes a puff on the aerosol-generating system based on information received from the puff sensor. The puff sensor may comprise a pressure sensor or a flow sensor. The puff sensor may comprise a temperature sensor, such as a thermistor. The puff sensor may comprise a negative temperature coefficient (NTC) thermistor. The puff sensor may comprise a positive temperature coefficient (PTC) thermistor. The control circuitry may be configured to determine when a user takes a puff on the aerosol-generating system based on a temperature of at least one of the internal heater and the external heater. For example, a drop in temperature of at least one of the internal heater and the external heater may occur as a result of increased airflow through the aerosol-generating system when a user takes a puff.

[0314] The control circuitry may be configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during a heating cycle. Advantageously, this may reduce the risk of overheating or burning at least one aerosolgenerating substrate in the aerosol-generating section of the aerosol-generating article.

[0315] The control circuitry may be configured to heat the internal heater to a maximum temperature of no more than 420 degrees Celsius during a heating cycle and configured to heat the external heater to a maximum temperature of no more than 350 degrees during a heating cycle.

[0316] The control circuitry may be configured to heat the internal heater to a maximum temperature of no more than 420 degrees Celsius during a heating cycle. The maximum temperature of the internal heater during a heating cycle may be no more than 410 degrees Celsius, no more than 400 degrees Celsius, no more than 390 degrees Celsius, no more than 380 degrees Celsius, no more than 370 degrees Celsius, no more than 360 degrees Celsius, no more than 350 degrees Celsius, no more than 340 degrees Celsius, no more than 330 degrees Celsius, no more than 325 degrees Celsius, no more than 320 degrees Celsius, no more than 315 degrees Celsius, no more than 310 degrees Celsius, no more than 305 degrees Celsius, or no more than 300 degrees Celsius.

[0317] The maximum temperature of the internal heater during a heating cycle may be at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius.

[0318] The maximum temperature of the internal heater during a heating cycle may be between 100 and 420 degrees Celsius, or between 150 and 420 degrees Celsius, or between 100 and 400 degrees Celsius, or between 150 and 400 degrees Celsius, or between 100 and 380 degrees Celsius, or between 150 and 380 degrees Celsius, or between 100 and 350 degrees Celsius, or between 150 and 350 degrees Celsius, or between 100 and 325 degrees Celsius, or between 150 and 325 degrees Celsius, or between 100 and 300 degrees Celsius, or between 150 and 300 degrees Celsius.

[0319] The control circuitry may be configured to heat the external heater to a maximum temperature of no more than 350 degrees Celsius during a heating cycle. The maximum temperature of the external heater during a heating cycle may be no more than 340 degrees Celsius, no more than 330 degrees Celsius, no more than 325 degrees Celsius, no more than 320 degrees Celsius, no more than 315 degrees Celsius, no more than 310 degrees Celsius, no more than 305 degrees Celsius, or no more than 300 degrees Celsius. The maximum temperature of the external heater during a heating cycle may be at least 100 degrees Celsius, at least 150 degrees Celsius, at least 200 degrees Celsius, at least 250 degrees Celsius, or at least 300 degrees Celsius.

[0320] The maximum temperature of the external heater during a heating cycle may be between 100 and 350 degrees Celsius, or between 150 and 350 degrees Celsius, or between 100 and 325 degrees Celsius, or between 150 and 325 degrees Celsius, or between 100 and 300 degrees Celsius, or between 150 and 300 degrees Celsius.

[0321] In some embodiments, during a heating cycle, the temperature at a point on a surface of the internal heater may spike above a preferred heating temperature for a brief period of time without negatively affecting aerosol generation, provided that the duration of the spike in temperature is sufficiently small. During a heating cycle, the temperature at any point on the surface of the internal heater may be above 400 degrees Celsius for a period of no longer than 2 seconds, or 1.5 seconds, or 1 second, or 0.5 seconds. During a heating cycle, the temperature at any point on the surface of the internal heater may be above 375 degrees Celsius for a period of no longer than 2 seconds, or 1.5 seconds, or 1 second, or 0.5 seconds. During a heating cycle, the temperature at any point on the surface of the internal heater may be above 350 degrees Celsius for a period of no longer than 2 seconds, or 1.5 seconds, or 1 second, or 0.5 seconds.

[0322] In some embodiments, during a heating cycle, the temperature at a point on a surface of the external heater may spike above a preferred heating temperature for a brief period of time without negatively affecting aerosol generation, provided that the duration of the spike in temperature is sufficiently small. During a heating cycle, the temperature at any point on the surface of the external heater may be above 350 degrees Celsius for a period of no longer than 2 seconds, or 1.5 seconds, or 1 second, or 0.5 seconds.

[0323] The control circuitry may be configured to heat the internal heater and the external heater during a heating cycle. The heating cycle may comprise a first phase and a second phase subsequent to the first phase.

[0324] The control circuitry may be configured to heat only the internal heater during the first phase. Preferably, the control circuitry is configured to heat both the internal heater and the external heart during the first phase.

[0325] The control circuitry may be configured to heat only the external heater during the second phase. Preferably, the control circuitry is configured to heat both the internal heater and the external heater during the second phase.

[0326] The control circuitry may be configured to heat one or both of the internal heater and the external heater during the first phase to increase a temperature of the internal heater during the first phase or to maintain a temperature of the internal heater above ambient temperature during the first phase. The control circuitry may be configured to heat the external heater during the second phase to increase a temperature of the external heater during the second phase. Advantageously, during the first phase, the temperature of the internal heater may increase. This may result in the internal heater heating an inner portion of the aerosol-generating substrate to generate an aerosol during the first phase. As the first phase progresses, the internal heater may heat more aerosol-generating substrate further from the internal heater as heat propagates outwardly from the internal heater. As explained in more detail later, the temperature of the internal heater may be increased as the first phase progresses to aid this. However, if the internal heater is heated to a too high temperature, there is a risk of overheating and burning the aerosolgenerating substrate close to the internal heater. Therefore, advantageously, after the first phase, during the second phase, the temperature of the internal heater may not be increased further, and the temperature of the external heater may increase. This may result in the external heater heating an outer portion of the aerosol-generating substrate to generate an aerosol during the second phase. As the second phase progresses, the external heater may heat more aerosolgenerating substrate further from the external heater as heat propagates inwardly from the external heater. As explained in more detail later, the temperature of the external heater may be increased as the second phase progresses to aid this. Therefore, the inner portion of the aerosolgenerating substrate may be significantly depleted during the first phase, and the outer portion of the aerosol-generating substrate may be significantly depleted during the second phase. This may advantageously result in substantially all of the aerosol-generating substrate being depleted so that there is less wasted aerosol-generating substrate, and a reduction in the risk of overheating and burning the aerosol-generating substrate.

[0327] It may be advantageous to increase the temperature of the internal heater during the first phase and to increase the temperature of the external heater during the second phase, rather than the other way round. This is because it may be possible to generate an aerosol more quickly using the internal heater than the external heater. This may be because the internal heater is more likely to be in more intimate thermal contact with the aerosol-generating substrate than the external heater. Therefore, this may advantageously reduce a minimum time needed for the system to first generate an aerosol.

[0328] The heating cycle may comprise a pre-heating phase. Preferably, the pre-heating phase occurs before the first phase. Preferably, the pre-heating phase occurs at the start of the heating cycle.

[0329] Preferably, the control circuitry is configured to heat one or both of the internal heater and the external heater during the pre-heating phase to increase a temperature of the internal heater to at least an internal heater minimum pre-heating temperature.

[0330] The heating cycle may comprise a cooling phase. Preferably, the cooling phase occurs after the pre-heating phase. Preferably, the cooling phase occurs immediately after the preheating phase. Preferably, the cooling phase occurs between the pre-heating phase and the first phase. Preferably, the control circuitry is configured to reduce heating of one or both of the internal heater and the external heater during the cooling phase to decrease a temperature of the internal heater to a temperature lower than the internal heater minimum pre-heating temperature. The control circuitry may be configured to heat one or both of the internal heater and the external heater during the first phase subsequent to the cooling phase to increase a temperature of one or both of the internal heater and the external heater.

[0331] Advantageously, the pre-heating phase may reduce a time needed for aerosol generation after a user first activates the system. Advantageously, the cooling phase may reduce a risk of a heater overheating, or the aerosol-generating substrate burning, or too much aerosol-generating substrate being heated to generate aerosol during the first few puffs during the heating cycle thereby leaving too little unused aerosol-generating substrate for generating aerosol for later puffs during the heating cycle. Advantageously, the first phase may allow more of the aerosolgenerating substrate to be depleted. For example, where the first phase involves one or both of the internal and external heaters gradually increasing in temperature over a plurality of puffs, as the first phase progresses, more of the aerosol-generating substrate may be heated to a sufficient temperature to generate an aerosol. Therefore, advantageously, the pre-heating phase, the cooling phase and the first phase together may facilitate a short time to a first puff without sacrificing user experience towards the end of the heating cycle because the aerosol-generating substrate is already too depleted or the remainder of the aerosol-generating substrate is not heated sufficiently to be depleted. Advantageously, the pre-heating phase, the cooling phase and the first phase may work together synergistically to facilitate more consistent aerosol generation from start to finish of a heating cycle compared with prior art aerosol-generating systems. In particular, increasing a temperature of the internal heater during the pre-heating phase may allow heating of the aerosol-generating substrate sufficiently quickly to allow generation of a substantial quantity of aerosol during an early portion of the heating cycle. Then, decreasing a temperature of the internal heater during the cooling phase may allow continued generation of sufficient aerosol while preventing the generation of too much aerosol during an intermediate portion of the usage session. Then, increasing a temperature of a heater during the first phase may allow sufficient aerosol generation during a later portion of the usage session at a time when much of the aerosol-generating substrate has already been heated to generate an aerosol.

[0332] Optionally, a temperature of the internal heater for at least a portion of the pre-heating phase, for example the internal heater minimum pre-heating temperature, is one or more of: at least 100, 200, or 300 degrees Celsius; and no more than 500 or 400 degrees Celsius. Optionally, a temperature of the internal heater for at least a portion of the pre-heating phase, for example the internal heater minimum pre-heating temperature, is between 200 and 500, or between 200 and 400, or between 300 and 400, preferably around 350 degrees Celsius. Optionally, a temperature of the external heater for at least a portion of the pre-heating phase, for example the external heater minimum pre-heating temperature, is one or more of: at least 100 or 200 degrees Celsius; and no more than 500 or 400 or 300 degrees Celsius. Optionally, a temperature of the external heater for at least a portion of the pre-heating phase, for example the external heater minimum pre-heating temperature, is between 100 and 500, or between 100 and 400, or between 100 and 300, or between 200 and 500, or between 200 and 400, or between 200 and 300, preferably around 240 degrees Celsius. Advantageously, such temperatures may provide an optimal compromise between quick initial heating and a risk of burning the aerosol-generating substrate.

[0333] Optionally, a temperature of the external heater is, for at least a portion of one or two or all of the pre-heating phase and the first phase and the second phase, at least 210 degrees Celsius.

[0334] Optionally, the pre-heating phase lasts for at least 5, 10, 20, or 30 seconds. Optionally, the pre-heating phase lasts for no more than 60, 45, or 30 seconds. Optionally, the pre-heating phase lasts for between 5 and 60, or between 5 and 45 seconds. Advantageously, this may allow sufficient pre-heating of the internal heater without taking so long as to frustrate a user.

[0335] The control circuitry may be configured to, at a beginning of the pre-heating phase, heat the internal heater to a temperature above 100 or 150 degrees Celsius before heating the external heater to a temperature of at least 50 or 90 degrees Celsius.

[0336] Optionally, during the cooling phase, a temperature of the internal heater decreases, for example from at least the internal heater minimum pre-heating temperature. Optionally, during the cooling phase, a temperature of the internal heater decreases by at least 10, 20, 50 or 100 degrees Celsius. Optionally, during the cooling phase, a temperature of the internal heater decreases to a temperature less than 300 or 250 degrees Celsius. Optionally, during the cooling phase, a temperature of the internal heater decreases to a temperature of at least 150 or 200 degrees Celsius.

[0337] Optionally, during the cooling phase, a temperature of the external heater decreases, for example from at least the external heater minimum pre-heating temperature. Optionally, during the cooling phase, a temperature of the external heater decreases by at least 10, 20, 50 or 100 degrees Celsius. Optionally, during the cooling phase, a temperature of the external heater decreases to a temperature less than 300 or 250 degrees Celsius. Optionally, during the cooling phase, a temperature of the external heater decreases to a temperature of at least 100, 150 or 200 degrees Celsius.

[0338] A fall in temperature of the internal heater over the cooling phase may be greater than a fall in temperature of the external heater over the cooling phase. This may be at least partly because the internal heater may be at a higher temperature than the external heater at one or both of the end of the pre-heating phase and the start of the cooling phase.

[0339] Advantageously, the cooling phase may reduce a risk of a heater overheating, or aerosolgenerating substrate burning, or too much aerosol-generating substrate being heated to generate aerosol during the first few puffs of the usage session thereby leaving too little unused aerosolgenerating substrate for generating aerosol for later puffs of the usage session. Optionally, for at least a portion of the cooling phase, for example for an initial portion of the cooling phase, no power is supplied to the internal heater. Optionally, for at least a portion of the cooling phase, for example for an initial portion of the cooling phase, no power is supplied to the external heater. Advantageously, this may allow the fastest rate of cooling and thus ensure that the early puffs do not deplete too much aerosol.

[0340] Optionally, the cooling phase lasts for at least 60, 90, 120, 150, or 180 seconds. Optionally, the cooling phase lasts for no more than 360, 300, 270, or 240 seconds. Optionally, the cooling phase lasts for between 60 and 360, or between 60 and 300, or between 90 and 270 seconds. Optionally, the cooling phase lasts for a duration of at least one puff, optionally at least 2, 3, or 5 puffs. Optionally, the cooling phase lasts for no more than 10 or 8 or 6 puffs. Optionally, the cooling phase lasts for between 1 and 10, or between 1 and 8, or between 2 and 8, or between 2 and 8, or between 2 and 6 puffs. Advantageously, such lengths of time may allow optimal cooling of one or both of the internal heater and the external heater. This may ensure that enough, but not too much, aerosol-generating substrate is heated to generate an aerosol during the early puffs of the usage session. This may also ensure that there is enough non-depleted aerosol-generating substrate for heating to generate an aerosol during the later puffs.

[0341] The control circuitry may be configured to, during the first phase, heat the internal heater to or maintain the internal heater at a temperature above 100 or 150 degrees Celsius. The control circuitry may be configured to, during the first phase, heat the internal heater to or maintain the internal heater at a temperature below 400 or 300 degrees Celsius. The temperature of the internal heater during the first phase may not exceed 300 or 400 degrees Celsius. The control circuitry may be configured to, during the first phase, heat the internal heater to or maintain the internal heater at a temperature between 100 and 400 degrees Celsius or between 150 and 300 degrees Celsius.

[0342] The control circuitry may be configured to, during the first phase, heat the external heater to or maintain the external heater at a temperature below 150 or 100 degrees Celsius. The temperature of the external heater during the first phase may not exceed 100 or 150 degrees Celsius. The control circuitry may be configured to, during the first phase, heat the external heater to or maintain the external heater at a temperature above 30 or 50 degrees Celsius. The control circuitry may be configured to, during the first phase, heat the external heater to or maintain the external heater at a temperature between 30 and 150 or between 50 and 100 degrees Celsius.

[0343] Optionally, no power is supplied to the external heater during the first phase. Optionally, the external heater is not heated above 100 degrees Celsius during the first phase. Advantageously, this may save power while the internal heater is being used to heat the aerosol-generating substrate to generate aerosol during the first phase.

[0344] Optionally, the first phase lasts for at least 60, 90, 120, 150, or 180 seconds. Optionally, the first phase lasts for no more than 360, 300, 270, or 240 seconds. Optionally, the first phase lasts for between 60 and 360, or between 60 and 300, or between 90 and 270 seconds. Optionally, the first phase lasts for a duration of at least one puff, optionally at least 2, 3, or 5 puffs. Optionally, the first phase lasts for no more than 10 or 8 puffs. Optionally, the first phase lasts for between 1 and 10, or between 1 and 8, or between 2 and 8, or between 3 and 8 puffs. Advantageously, such lengths of time may allow significant depletion of the aerosol-generating substrate.

[0345] Optionally, the control circuitry is configured so that a temperature of the internal heater is held constant, or decreases, for example monotonically or continuously decreases, for at least a portion of the second phase.

[0346] Optionally, the control circuitry is configured so that a temperature of the external heater increases, for example monotonically or continuously increases, for at least a portion of the second phase until a maximum external heater temperature is reached.

[0347] Optionally, a temperature of the external heater is held constant or increases during the second phase. Optionally, a temperature of the external heater at an end of the second phase is greater than a temperature of the external heater at a start of the second phase. Optionally, an average temperature of the external heater over a first portion, for example first half, of the second phase is less than, greater than or equal to an average temperature of the external heater over a subsequent second portion, for example subsequent second half, of the second phase. Optionally, a temperature of the external heater increases substantially monotonically, for example continuously, for at least a portion of the second phase. Advantageously, increasing a temperature of the external heater as the second phase progresses may allow the external heater to gradually heat more of the aerosol-generating substrate further from the external heater sufficiently to generate an aerosol as the second phase progresses.

[0348] The control circuitry may be configured to heat the external heater to a higher temperature during the second phase than during the first phase. Optionally, a peak temperature of the external heater during the second phase is greater, for example at least 20, 50, or 100 degrees Celsius greater, than a peak temperature of the external heater during the first phase. Optionally, an average temperature of the external heater during the second phase is greater, for example at least 20, 50, or 100 degrees Celsius greater, than an average temperature of the external heater during the first phase. Advantageously, greater heating of the external heater during the second phase compared with the first phase may allow an outer portion of the aerosol-generating substrate to be significantly depleted during the second phase. This may result in less waste of the outer portion of the aerosol-generating substrate.

[0349] Optionally, a temperature of the external heater at an end of the second phase is greater, for example at least 20, 50, or 100 degrees Celsius greater, than a temperature of the external heater at a start of the second phase. Advantageously, heating of the external heater more as the second phase progresses may allow the external heater to heat more aerosol-generating substrate further from the external heater as the second phase progresses. This may advantageously allow initial formation of aerosol from an outermost portion of the aerosolgenerating substrate, followed by formation of aerosol from gradually more inwardly located portions of the aerosol-generating substrate. This may result in less waste of the outer portion of the aerosol-generating substrate.

[0350] Optionally, an average temperature difference between the internal heater and the external heater at a start of the second phase is greater than 20, 50 or 100 degrees Celsius. Optionally, an average temperature difference between the internal heater and the external heater at an end of the second phase is less than 20, 50 or 100 degrees Celsius. Advantageously, by heating the external heater during the second phase to reach a similar temperature to the internal heater, the outer portion of the aerosol-generating substrate may be heated sufficiently to generate an aerosol.

[0351] The control circuitry may be configured to, during the second phase, maintain a temperature of the internal heater above 100 or 150 degrees Celsius. The control circuitry may be configured to, during the second phase, maintain a temperature of the internal heater below 400 or 300 degrees Celsius. The temperature of the internal heater during the second phase may not exceed 300 or 400 degrees Celsius. The control circuitry may be configured to, during the second phase, maintain a temperature of the internal heater between 100 and 400 or between 150 and 300 degrees Celsius.

[0352] The control circuitry may be configured to, during the second phase, heat the external heater to or maintain the external heater at a temperature greater than 100 or 150 degrees Celsius. The control circuitry may be configured to, during the second phase, heat the external heater to or maintain the external heater at a temperature no more than 300 or 400 degrees Celsius. The temperature of the external heater during the second phase may not exceed 300 or 400 degrees Celsius. The control circuitry may be configured to, during the second phase, heat the external heater to or maintain the external heater at a temperature between 100 and 400 or between 150 and 300 degrees Celsius. The control circuitry may be configured to, during the second phase, after heating the external heater to a temperature of between 100 and 400 or between 150 and 300 degrees Celsius, maintain the external heater at a temperature between 100 and 400 or between 150 and 300 degrees Celsius.

[0353] Preferably, the control circuitry is configured to stop heating both the internal heater and the external heater at an end of the second phase.

[0354] Optionally, the second phase lasts for at least 60, 90, 120, 150, or 180 seconds. Optionally, the second phase lasts for no more than 360, 300, 270, or 240 seconds. Optionally, the second phase lasts for between 60 and 360, or between 60 and 300, or between 90 and 270 seconds. Optionally, the second phase lasts for a duration of at least one puff, optionally at least 2, 3, or 5 puffs. Optionally, the second phase lasts for no more than 10 or 8 puffs. Optionally, the second phase lasts for between 1 and 10, or between 1 and 8, or between 2 and 8, or between 3 and 8 puffs. Advantageously, such lengths of time may allow significant depletion of the aerosolgenerating substrate. The control circuitry may be configured to adjust heating of one or both of the internal heater and the external heater as a function of one or more of a puff count over a heating cycle, a time elapsed since commencement of a heating cycle, and detection of a puff in a heating cycle.

[0355] The external heater may at least partially surround or define the chamber for receiving the aerosol-generating article. The external heater may have a coil or helical shape. The external heater may be substantially tubular in shape.

[0356] The external heater may be a resistive heater.

[0357] The external resistive heater may comprise a resistive heating element. The resistive heating element may comprise an electrically insulating substrate, for example a substantially tubular electrically insulating substrate, and an electrically conductive track on the electrically insulating substrate. The control circuitry may be configured to pass an electrical current through the electrically conductive track in use to resistively heat the electrically conductive track.

[0358] As used herein, the term “electrically insulating” may refer to a material having an electrical conductivity of less than 0.8x104Siemens per metre in at least one direction, for example in all directions, at room temperature (20 degrees Celsius) and a relative humidity of 50%.

[0359] As used herein, the term “electrically conductive” may refer to a material having an electrical conductivity of at least 0.8x106Siemens per metre in at least one direction, for example in all directions, at room temperature (20 degrees Celsius) and a relative humidity of 50%.

[0360] 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.

[0361] Suitable electrically conductive 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.

[0362] Where the external heater is an electrically resistive heater, the external heater may comprise or be formed from one or both of a substantially magnetically transparent material and a non-inductively heatable material. This may be particularly advantageous where the system also comprises an inductor coil, as further described herein. The external heater may comprise an external susceptor element extending around at least a portion of the chamber and an inductor coil. 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 to inductively heat the external susceptor element.

[0363] As used herein, the term “susceptor” refers to an element comprising a material that is capable of converting the energy of a magnetic field into heat. When a susceptor is located in an alternating magnetic field, the susceptor is 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.

[0364] The external susceptor element may have a tubular shape. The external susceptor element may at least partially define the chamber for receiving the aerosol-generating article. The inductor coil may extend around an exterior surface of the external susceptor element. The inductor coil may directly contact an exterior surface of the external susceptor element.

[0365] The external susceptor element may comprise or consist of one or more susceptor materials. Suitable susceptor materials may include but are not limited to: carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminium, nickel, nickel-containing compounds, titanium, and composites of metallic materials. Suitable susceptor materials may comprise a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy, such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. A susceptor material may comprise more than 5 percent, preferably more than 20 percent, more preferably more than 50 percent or more than 90 percent of ferromagnetic or paramagnetic materials. Preferred susceptor materials may comprise a metal, metal alloy or carbon.

[0366] The aerosol-generating device may comprise the internal heater.

[0367] The internal heater may be arranged to be at least partially received within the aerosolgenerating section when the aerosol-generating article is received within the chamber.

[0368] The internal heater may extend from a base or a closed end of the chamber. The internal heater may extend into the chamber, for example towards an open end of the chamber. The internal heater may be shaped as a pin, blade, or rod for penetrating the aerosol-generating section of the aerosol-generating article when the article is inserted into the chamber.

[0369] The internal heater may be a resistive heater.

[0370] The internal resistive heater may comprise a resistive heating element. The resistive heating element may comprise an electrically insulating substrate, for example a substantially tubular electrically insulating substrate, and an electrically conductive track on the electrically insulating substrate. The control circuitry may be configured to pass an electrical current through the electrically conductive track in use to resistively heat the electrically conductive track. 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.

[0371] Suitable electrically conductive 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.

[0372] The internal heater may comprise an internal susceptor element arranged to be at least partially received within the aerosol-generating section of the aerosol-generating article when the aerosol-generating article is received within the chamber.

[0373] The internal susceptor element may form part of the aerosol-generating article, as described above. The internal susceptor element may be arranged within the aerosol-generating section of the aerosol-generating article. The internal susceptor element may be arranged in direct contact with the aerosol-generating substrate of the aerosol-generating section. The internal susceptor element may be embedded within the aerosol-generating substrate .

[0374] The internal susceptor element may form part of the aerosol-generating device. The internal susceptor element may be arranged for insertion into the aerosol-generating section of the aerosol-generating article when the article is inserted into the chamber.

[0375] The aerosol-generating device may comprise an inductor coil, wherein the control circuitry is configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field to inductively heat the internal susceptor element. In embodiments in which the external heater comprises an external susceptor element, preferably, the inductor coil may be a single inductor coiled arranged to inductively heat both the external susceptor element and the internal susceptor element. Alternatively, the aerosolgenerating device may comprise a first inductor coil arranged to inductively heat the external susceptor element and a second inductor coil arranged to inductively heat the internal susceptor element.

[0376] The internal susceptor element may comprise or consist of one or more susceptor materials. Suitable susceptor materials may include but are not limited to: carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminium, nickel, nickel-containing compounds, titanium, and composites of metallic materials. Suitable susceptor materials may comprise a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy, such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. A susceptor material may comprise more than 5 percent, preferably more than 20 percent, more preferably more than 50 percent or more than 90 percent of ferromagnetic or paramagnetic materials. Preferred susceptor materials may comprise a metal, metal alloy or carbon.

[0377] In embodiments in which the aerosol-generating device comprises an inductor coil, the inductor coil may form the external resistive heater. The control circuitry may be configured to provide an alternating electric current to the inductor coil to generating an alternating magnetic field to inductively heat one or more susceptor elements, and the control circuitry may be configured to provide a direct electric current to the inductor coil to resistively heat the inductor coil. For example, the control circuitry may be configured to switch between providing the alternating current and the direct current to the inductor coil. The internal heater may comprise an internal susceptor element, wherein during use the inductor coil inductively heats the internal susceptor element and the inductor coil is resistively heated as the external heater. When the control circuitry is configured to simultaneously heat the external heater and the internal heater, the control circuitry may be configured to rapidly switch back and forth between providing the alternating current to the inductor coil and providing the direct current to the inductor coil.

[0378] In a first example, the aerosol-generating device comprises an external resistive heater and an inductor coil, and the internal heater comprises an internal susceptor element.

[0379] In a second example, the aerosol-generating device comprises an inductor coil, wherein the control circuitry is configured to supply an alternating electric current to the inductor coil for generating an alternating magnetic field, wherein the control circuitry is configured to supply a direct electric current to the inductor coil to operate the inductive coil as an external resistive heater, and wherein the internal heater comprises an internal susceptor element.

[0380] In a third example, the external heater is an external resistive heater, wherein the aerosolgenerating device comprises the internal heater, and wherein the internal heater is an internal resistive heater.

[0381] The aerosol-generating device may comprise at least one power supply. References herein to “a power supply” or “the power supply” should be considered references to the at least one power supply. References herein to a supply of power may refer to a supply of power from the power supply. Controlling a supply of power to the internal heater or to the external heater may comprise or be controlling a supply of power, for example controlling one or both of current and voltage, from the at least one power supply to the internal heater or to the external heater. References herein to increasing or decreasing a temperature of the internal heater may be a result of controlling a supply of power to one or both of the internal heater and the external heater. References herein to increasing or decreasing a temperature of the external heater may be a result of controlling a supply of power to the external heater. In embodiments in which at least one of the internal heater and the external heater comprises a susceptor element, references to heating the internal heater or the external heater comprise controlling a supply of power to an inductor coil to heat the susceptor element.

[0382] In examples and embodiments in which a heater comprises a susceptor element and the aerosol-generating device comprises an inductor coil for inductively heating the susceptor element, a supply of power to the inductor coil may be increased to increase a temperature of the susceptor element. Similarly, a supply of power to the inductor coil may be decreased to decrease a temperature of the susceptor element.

[0383] The power supply may be or comprise a battery. The battery may be rechargeable. The battery may be a Lithium-based battery, for example a Lithium-Cobalt, a Lithium-lron-Phosphate, a Lithium Titanate or a Lithium-Polymer battery, or a Nickel-metal hydride or Nickel cadmium battery. The power supply may be another form of charge storage device such as a capacitor. The power supply may have sufficient capacity to allow for the continuous generation of aerosol for a period of at least six minutes, corresponding to the typical time taken to smoke a conventional cigarette.

[0384] In embodiments in which the aerosol-generating device comprises a power supply, the control circuitry is configured to control a supply of power to from the power supply to at least one of the external heater, the internal heater, and an inductor coil. The control circuitry may comprise a microprocessor, which may be a programmable microprocessor, a microcontrol circuitry, 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 at least one of the external heater, the internal heater, and an inductor coil. Current may be supplied to at least one of the external heater, the internal heater, and an 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 a DC / AC inverter, which may comprise a Class-D or Class-E power amplifier.

[0385] The aerosol-generating device may comprise a heat-conducting element, also referred to herein as a thermally conductive bridging element.

[0386] As used herein, the term “thermally conductive” may refer to a material having a thermal conductivity of at least 5, 10, 20, 50, or 100 Watts per metre-Kelvin in at least one direction, for example in all directions, at room temperature (20 degrees Celsius) and a relative humidity of 50%.

[0387] The thermally conductive bridging element may be positioned between the external heater and the chamber. The thermally conductive bridging element may be in contact with the external heater.

[0388] The thermally conductive bridging element may be configured to contact an exterior surface of the aerosol-generating article when the aerosol-generating article is received in the chamber. The thermally conductive bridging element may at least partially define the chamber. In use, heat may be transferred from the thermally conductive bridging element to the article. The thermally conductive bridging element may advantageously facilitate more uniform heating of the aerosolgenerating substrate.

[0389] In embodiments in which the aerosol-generating device comprises an inductor coil in addition to the external heater, the inductor coil may extend around at least a portion of the thermally conductive bridging element. The inductor coil may be in contact with an outer surface of the thermally conductive bridging element.

[0390] The thermally conductive bridging element may be the external heater. The control circuitry may be configured to supply a direct current to the thermally conductive bridging element to resistively heat the thermally conductive bridging element.

[0391] The thermally conductive bridging element may be formed from a non-electrically conductive material. The thermally conductive bridging element may be formed from a substantially non-inductively heatable material. The thermally conductive bridging element may comprise at least one of a polymeric material and a metal. The thermally conductive bridging element 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. The heat conducting element may be formed from 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.

[0392] Preferably, the aerosol-generating device is configured to determine or estimate a temperature of one or both of the internal heater and the external heater. In this context, determining a temperature of a component may refer to determining a temperature at one or more locations of the component. The aerosol-generating device may comprise at least one temperature-sensing means for this purpose. The temperature-sensing means may be or comprise one or more dedicated temperature sensors. Alternatively, or in addition, the control circuitry may be configured to determine a temperature of a heater, for example a resistive heater, by measuring or calculating its electrical resistance. In this case, the control circuitry may be considered to comprise the temperature-sensing means. This electrical resistance may be calculated by dividing a potential difference V across the heater by a current I flowing through the heater. Then, a resistance-temperature dataset may be used to determine the temperature of the heater. Advantageously, precisely controlling the temperatures of the internal heater and the external heater may facilitate precise control of a temperature of the aerosol-generating substrate. Advantageously, this may facilitate more precise control of a quantity and composition of an aerosol formed during use.

[0393] The aerosol-generating system, for example the aerosol-generating device, may comprise an air inlet. The aerosol-generating system, for example the aerosol-generating article, may comprise an air outlet. The aerosol-generating system may comprise an air flow path. The air flow path may connect the air inlet and the air outlet. In use, for example in response to a puff on the aerosol-generating article, air may flow through the air inlet and then through the article and then through the air outlet. After flowing through the air outlet, the air may flow into a mouth of a user.

[0394] 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.

[0395] Preferably, the aerosol-generating device comprises a housing. The housing of the device 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.

[0396] 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.

[0397] Example 1 : An aerosol-generating system comprising: an aerosol-generating article comprising: an aerosol-generating section comprising an aerosol-generating substrate; an aerosol-generating device comprising: a chamber for receiving at least a portion of the aerosol-generating section of the aerosolgenerating article; an external heater extending around at least a portion of the chamber; and control circuitry; and an internal heater arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber.

[0398] Example 2: An aerosol-generating system according to Example 1 , wherein the control circuitry is configured to heat the internal heater to a temperature greater than a temperature of the external heater during a first phase, and wherein the control circuitry is configured to heat the external heater to a temperature greater than a temperature of the internal heater during a second phase after the first phase.

[0399] Example 3: An aerosol-generating system according to Example 1 or 2, wherein the control circuitry is configured to heat the internal heater to an internal heater temperature during a heating cycle, wherein the control circuitry is configured to heat the external heater to an external heater temperature during the heating cycle, and wherein the control circuitry is configured to change a difference between the internal heater temperature and the external heater temperature during the heating cycle.

[0400] Example 4: An aerosol-generating system according to any preceding Example, wherein the control circuitry is configured to heat the internal heater and the external heater during a heating cycle, and wherein the control circuitry is configured to start heating of the internal heater before starting heating of the external heater during the heating cycle.

[0401] Example 5: An aerosol-generating system according to any preceding Example, wherein the control circuitry is configured to heat the internal heater to a maximum internal heater temperature, wherein the control circuitry is configured to heat the external heater to a maximum external heater temperature, and wherein the maximum external heater temperature is less than the maximum internal heater temperature.

[0402] Example 6: An aerosol-generating system according to any preceding Example wherein the control circuitry is configured to heat the internal heater to a maximum internal heater temperature during a heating cycle, wherein the control circuitry is configured to heat the external heater to a maximum external heater temperature during the heating cycle, and wherein the internal heater reaches the maximum internal heater temperature at a different time to the external heater reaching the maximum external heater temperature during the heating cycle.

[0403] Example 7: An aerosol-generating system according to any preceding Example, wherein the chamber defines a longitudinal direction along which the aerosol-generating article may be inserted into the chamber, wherein the external heater has a length extending in the longitudinal direction, wherein the internal heater has a length extending in the longitudinal direction, and wherein a ratio of the length of the internal heater to the length of the external heater is between 0.2 and 5.

[0404] Example 8: An aerosol-generating system according to Example 7, wherein the ratio of the length of the internal heater to the length of the external heater may be between 0.2 and 4, or between 0.2 and 3, or between 0.2 and 2, or between 0.3 and 1.9, between 0.4 and 1.9, or between 0.6 and 1.8, or between 0.7 and 1.7, or between 0.8 and 1.6, or between 0.9 and 1.5, or between 1.0 and 1.4, or between 1.1 and 1.3.

[0405] Example 9: An aerosol-generating system according to any preceding Example, wherein the control circuitry is configured to determine when a user takes puff on the aerosol-generating system.

[0406] Example 10: An aerosol-generating system according to Example 9, wherein the control circuitry is configured to control heating of at least one of the internal heater and the external heater based on the control circuitry determining that a user is taking a puff or has taken one or more puffs on the aerosol-generating system.

[0407] Example 11 : An aerosol-generating system according to any preceding Example, wherein the control circuitry is configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during a heating cycle.

[0408] Example 12: An aerosol-generating system according to Example 11 , wherein the control circuitry is configured to heat the internal heater to a maximum temperature of no more than 420 degrees Celsius during a heating cycle and configured to heat the external heater to a maximum temperature of no more than 350 degrees during a heating cycle.

[0409] Example 13: An aerosol-generating system according to any preceding Example, wherein the external heater comprises a resistive heating element.

[0410] Example 14: An aerosol-generating system according to any preceding Example, wherein the external heater comprises an external susceptor element extending around at least a portion of the chamber and an inductor coil, wherein the control circuitry is configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field to inductively heat the external susceptor element.

[0411] Example 15: An aerosol-generating system according to any preceding Example, wherein the aerosol-generating device comprises the internal heater.

[0412] Example 16: An aerosol-generating system according to Example 15, wherein the internal heater comprises a resistive heating element arranged to be at least partially received within the aerosol-generating substrate when the aerosol-generating article is received within the chamber.

[0413] Example 17: An aerosol-generating system according to Example 15, wherein the internal heater comprises an internal susceptor element arranged to be at least partially received within the aerosol-generating section when the aerosol-generating article is received within the chamber, wherein the aerosol-generating device comprises an inductor coil, and wherein the control circuitry is configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field to inductively heat the internal susceptor element.

[0414] Example 18: An aerosol-generating system according to any of Examples 1 to 14, wherein the aerosol-generating article comprises the internal heater, wherein the internal heater comprises an internal susceptor element positioned within the aerosol-generating section, wherein the aerosol-generating device comprises an inductor coil, and wherein the control circuitry is configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field to inductively heat the internal susceptor element. Example 19: An aerosol-generating system according to any preceding Example, wherein the aerosol-generating substrate comprises at least 5 percent by weight of nontobacco botanical material, on a dry weight basis.

[0415] Example 20: An aerosol-generating system according to Example 19, wherein the aerosol-generating substrate comprises at least 15 percent by weight of non-tobacco botanical material, on a dry weight basis.

[0416] Example 21 : An aerosol-generating system according to Example 19 or 20, wherein the non-tobacco botanical material in the aerosol-generating substrate is selected from rooibos, tea including black tea, apple fibre, rosehip seed, lemon balm stem, peppermint stem, chamomile, verbena, elderflower, oat herb, parsley stem, geranium, lime, kaffir lime, lemon myrtle ambrette seed, tolu balsam, passion berry, timur berry, coffee and combinations thereof.

[0417] Example 22: An aerosol-generating system according to any of Examples 19 to 21 , wherein the aerosol-generating substrate further comprises exogenous nicotine.

[0418] Example 23: An aerosol-generating system according to any of Examples 19 to 22, wherein the aerosol-generating substrate comprises: at least 50 percent by weight of non-tobacco botanical material, on a dry weight basis; one or more aerosol formers; and exogenous nicotine.

[0419] Example 24: An aerosol-generating system according to any of Examples 19 to 23, wherein the aerosol-generating substrate is substantially free from tobacco.

[0420] Examples will now be further described with reference to the drawings of the accompanying Figures in which:

[0421] Figure 1 shows a side cross-sectional view of an aerosol-generating device according to a first embodiment of the present invention;

[0422] Figure 2 shows an axial cross-sectional view of the aerosol-generating device of Figure 1 along line 1-1 ;

[0423] Figure 3 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figure 1 ;

[0424] Figure 4 shows a side cross-sectional view of an aerosol-generating device according to a second embodiment of the present invention;

[0425] Figure 5 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figure 4;

[0426] Figure 6 shows a side cross-sectional view of an aerosol-generating device according to a third embodiment of the present invention;

[0427] Figure 7 shows a side cross-sectional view of an aerosol-generating device according to a fourth embodiment of the present invention; Figure 8 illustrates temperature profiles over time for the internal and external heaters of an aerosol-generating system according to an embodiment of the present invention;

[0428] Figure 9 illustrates temperature profiles over time for the internal and external heaters of an aerosol-generating system according to another embodiment of the present invention;

[0429] Figure 10 illustrates temperature profiles over time for the internal and external heaters of an aerosol-generating system according to another embodiment of the present invention;

[0430] Figure 11 shows a side cross-sectional view of an aerosol-generating article suitable for use in the aerosol-generating system of Figure 3; and

[0431] Figure 12 shows a side cross-sectional view of an aerosol-generating article suitable for use in the aerosol-generating system of Figure 5.

[0432] 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.

[0433] 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.

[0434] 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.

[0435] 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.

[0436] 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.

[0437] 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 resistively heated external heater 29.

[0438] The control circuitry 40 is also configured to determine when a user is puffing on an aerosol-generating system comprising the aerosol-generating device 10. In this example, the aerosol-generating device 40 comprises a puff sensor (not shown), wherein the control circuitry 40 is configured to determine when a user is puffing on the aerosol-generating system based on information received from the puff sensor.

[0439] 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.

[0440] The aerosol-generating article 102 comprises an aerosol-generating section 104 comprising at least one aerosol-generating substrate, a downstream section 106 downstream of the aerosol-generating section 104, and an upstream section 108 upstream of the aerosolgenerating section 104. The aerosol-generating article 102 also comprises an internal heater in the form of a susceptor element 114 arranged within the aerosol-generating section 104. During use, a portion of the aerosol-generating article 102 is inserted into the chamber 16 so that the aerosol-generating section 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 an inner portion of the at least one aerosol-generating substrate in the aerosol-generating section 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 an outer portion of the at least one aerosol-generating substrate in the aerosol-generating section 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 28 and the aerosol-generating article 102, which increases or maximises the transfer of heat from the heat-conducting element 28 to the aerosol-generating article 102. Advantageously, the external heating provided by the resistively heated heat-conducting element 28 and the internal heating provided by the inductively heated susceptor element 114 may facilitate aerosol generation across both the inner and outer portions of the at least one aerosol-generating substrate in the aerosol-generating section 104.

[0441] Airflow through the aerosol-generating system 100 during use is illustrated by the dashed lines 116 in Figure 3. When a user draws on a downstream end 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 an upstream end of the aerosol-generating article 102. 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 aerosolgenerating section 104, aerosol generated by heating of the at least one aerosol-generating substrate is entrained in the airflow. The aerosol then flows along the length of the aerosolgenerating article 102 and through the downstream end of the aerosol-generating article 102 to the user.

[0442] Figure 4 shows a schematic cross-sectional view of an aerosol-generating device 200 in accordance with a second embodiment of the present invention. The aerosol-generating device 200 is similar to the aerosol-generating device 10 of Figure 1 and like reference numerals are used to designate like parts.

[0443] The aerosol-generating device 200 differs from the aerosol-generating device 10 by the addition of an internal heater in the form of an internal susceptor element 214 extending into the chamber 16 from the closed second end 20 of the chamber 16. The aerosol-generating device 200 may be used with aerosol-generating articles that do not include an internal susceptor element 114 as described with reference to Figure 3.

[0444] Figure 5 shows a cross-sectional view of an aerosol-generating system 250 comprising the aerosol-generating device 200 of Figure 4 and an aerosol-generating article 252.

[0445] The aerosol-generating article 252 comprises an aerosol-generating section 254 comprising at least one aerosol-generating substrate, and a downstream section 106 downstream of the aerosol-generating section 254. During use, the aerosol-generating section 254 of the aerosol-generating article 252 is inserted into the chamber 16 so that the aerosol-generating section 254 is positioned inside the heat-conducting element 28 and the inductor coil 24, and the susceptor element 214 is received within the aerosol-generating section 254. 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 214, which heats an inner portion of the at least one aerosol-generating substrate in the aerosol-generating section 254 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 an outer portion of the at least one aerosol-generating substrate in the aerosol-generating section 254 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 252 facilitates the transfer of the resistively generated heat from the heat-conducting element 28 to the aerosol-generating article 252. 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 28 and the aerosol-generating article 252, which increases or maximises the transfer of heat from the heat-conducting element 28 to the aerosol-generating article 252. Advantageously, the external heating provided by the resistively heated heat-conducting element 28 and the internal heating provided by the inductively heated susceptor element 214 may facilitate aerosol generation across both the inner and outer portions of the at least one aerosol-generating substrate in the aerosol-generating section 254.

[0446] Airflow through the aerosol-generating system 250 during use is illustrated by the dashed lines 116 in Figure 5. When a user draws on a downstream end of the aerosol-generating article 252, a negative pressure is generated in the chamber 16. The negative pressure draws air into the aerosol-generating device 200 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 252 through an upstream end of the aerosol-generating article 252. Airflow into the aerosol-generating article 252 is facilitated by the gap maintained between the upstream end of the aerosol-generating article 252 and the second end 20 of the chamber 16 by the plurality of protrusions 38. As the airflow passes through the aerosolgenerating section 254, aerosol generated by heating of the at least one aerosol-generating substrate is entrained in the airflow. The aerosol then flows along the length of the aerosolgenerating article 252 and through the downstream end of the aerosol-generating article 252 to the user.

[0447] Figure 6 shows a schematic cross-sectional view of an aerosol-generating device 300 in accordance with a third embodiment of the present invention. The aerosol-generating device 300 is similar to the aerosol-generating device 10 of Figure 1 and like reference numerals are used to designate like parts.

[0448] The aerosol-generating device 300 of Figure 6 comprises the same tubular heat- conducting element 28 as the aerosol-generating device 10 of Figure 1. The aerosol-generating device 300 also comprises 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 contact with the outer surface 21 of the heat-conducting element 28. The aerosolgenerating device 300 also comprises an external heater in the form of 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 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 an internal heater in the form of a susceptor element of an aerosol-generating article to provide internal heating of the aerosolgenerating article. For example, the aerosol-generating device 300 of Figure 6 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-generating article.

[0449] Figure 7 shows a schematic cross-sectional view of an aerosol-generating device 400 in accordance with a fourth embodiment of the present invention. The aerosol-generating device 400 is similar to the aerosol-generating device 300 of Figure 5 and like reference numerals are used to designate like parts.

[0450] The aerosol-generating device 400 differs from the aerosol-generating device 300 by the addition of an internal heater in the form of an internal susceptor element 214 extending into the chamber 16 from the closed second end 20 of the chamber 16. The aerosol-generating device 400 may be used with aerosol-generating articles that do not include an internal susceptor element 114 as described with reference to Figure 3. For example, the aerosol-generating device 400 of Figure 7 may be used with the aerosol-generating article 252 of Figure 5. When an aerosolgenerating article is inserted into the chamber 16, the internal susceptor element 214 is inserted into the aerosol-generating section 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 324 to generate an alternating magnetic field that inductively heats the susceptor element 214. Otherwise, the operation of the aerosol-generating device 400 is the same as the operation of the aerosol-generating device 300 described with reference to Figure 6.

[0451] Figure 8 illustrates a first example of a heating profile for a heating cycle of an aerosolgenerating system according to the present invention. For example, the heating profile of Figure 8 may be used with any of the aerosol-generating devices described with reference to Figures 1 to 7 and may be implemented by the control circuitry 40. Figure 8 shows how temperature T, specifically a temperature Tjnof the internal heater and a temperature Texof the external heater, varies over time t.

[0452] Prior to time to, the control circuitry does not heat the internal or external heaters, and therefore the temperatures of the internal heater and the external heater Tin, Tex are both stable at room temperature To.

[0453] At time to, a pre-heating phase, which is part of the first phase in this embodiment, begins. In other, similar embodiments, the pre-heating phase could be considered separate to the first phase, in which case the first phase could be considered to begin at the end of the pre-heating phase at time tx. At time to, the temperature of the internal heater is rapidly increased to a preheating phase temperature of around 380 degrees Celsius. Neither the internal heater nor external heater exceed the pre-heating phase temperature during the first phase or the second phase. At time tx, the pre-heating phase ends. Because the pre-heating phase is relatively short at around 30 seconds and the aerosol-generating substrate takes time to warm up to form an aerosol, and because the user has not yet begun puffing on the system, very little or substantially no aerosol is formed during the pre-heating phase. At the end of the pre-heating phase, the device may alert a user that the system is ready for puffing, for example using an audible, visual or haptic alert.

[0454] At time tx, the power supplied to the internal heater is reduced so that the internal heater is allowed to cool from the pre-heating phase temperature. This cooling phase is maintained from time txto time ta. Over this time, which may last around one minute, the internal heater is held at around 300 degrees Celsius and internal heater heats the an inner portion of the at least one aerosol-generating substrate to form an aerosol or a vapour which cools and condenses to form an aerosol.

[0455] At time ta, the temperature of the internal heater is increased to and maintained around 320 degrees Celsius. Over this time, which may last around one minute, heat propagates outwardly from the internal heater and slightly more of the inner portion of the at least one aerosolgenerating substrate is heated sufficiently to form an aerosol or a vapour which cools and condenses in an airflow to form an aerosol, compared with the time between txand ta.

[0456] At time tb, the temperature of the internal heater is increased to and maintained around 340 degrees Celsius. Over this time, which may last around one minute, heat propagates outwardly from the internal heater and slightly more of the inner portion of the at least one aerosolgenerating substrate is heated sufficiently to form an aerosol or a vapour which cools and condenses in an airflow to form an aerosol, compared with the time between taand tb.

[0457] By time ti , at the end of the first phase, most of the inner portion of the at least one aerosolgenerating substrate has been heated to a sufficient temperature to form an aerosol and so is depleted. Most of an outer portion of the at least one aerosol-generating substrate has not been heated to a sufficient temperature to form an aerosol and so is not depleted. At time ti , the first phase ends and the second phase begins. At time ti , a power supply to the internal heater is reduced so that the temperature Tjnof the internal heater gradually falls over the course of the second phase from time ti to time t2.

[0458] Also at time ti , the external heater is heated so that the temperature of the external heater Texincreases over the second phase from time ti to time t2, reaching a final temperature of around 320 degrees Celsius at time t2. Over the second phase, which may last around 3 minutes, heat propagates inwardly from the external heater. As the second phase progresses, slightly more of the outer portion of the at least one aerosol-generating substrate is heated sufficiently to form an aerosol or a vapour which cools and condenses in an airflow to form an aerosol.

[0459] By time t2, at the end of the second phase, most of the outer portion of the at least one aerosol-generating substrate has been heated to a sufficient temperature to form an aerosol so is depleted. Therefore, with the inner and outer portions of the at least one aerosol-generating substrate depleted, the substrate is substantially entirely depleted. By time t2, at the end of the second phase, the temperature of the external heater Texis within 50 degrees Celsius of, and slightly less than, the temperature of the internal heater Tjn.

[0460] Figure 9 illustrates a second example of a heating profile for a heating cycle of an aerosolgenerating system according to the present invention. For example, the heating profile of Figure 9 may be used with any of the aerosol-generating devices described with reference to Figures 1 to 7 and may be implemented by the control circuitry 40. Figure 9 shows how temperature T, specifically a temperature Tjnof the internal heater and a temperature Texof the external heater, varies over time t, including over a pre-heating phase between times to and tx, a first phase between times txand ti, and a second phase between times ti and t2.

[0461] Prior to time to, no power is supplied to the internal and external heaters and the temperatures of the internal heater and the external heater Tin, Texare both stable at room temperature To.

[0462] At time to, a pre-heating phase, which is part of the first phase in this embodiment, begins. In other, similar embodiments, the pre-heating phase could be considered separate to the first phase, in which case the first phase could be considered to begin at the end of the pre-heating phase at time tx. At time to, the temperature of the internal heater is rapidly increased to a preheating phase temperature of around 380 degrees Celsius. Neither the internal heater nor external heater exceed the pre-heating phase temperature during the first phase or the second phase. At time tx, the pre-heating phase ends. Because the pre-heating phase is relatively short at around 30 seconds and the aerosol-generating substrate takes time to warm up to form an aerosol, and because the user has not yet begun puffing on the system, very little or substantially no aerosol is formed during the pre-heating phase. At the end of the pre-heating phase, the device may alert a user that the system is ready for puffing, for example using an audible, visual or haptic alert. At time tx, the power supplied to the internal heater is reduced so that the internal heater is cooled to and maintained at around 300 degrees Celsius from time txto time ti, which may last around five minutes.

[0463] Also at time tx, the beginning of the first phase, power is supplied to the external heater to begin heating the external heater to increase the temperature Texof the external heater. The power supplied to the external heater is increased in a stepwise manner to increase the temperature Texof the external heater in a stepwise manner. The stepwise increases in the temperature Texof the external heater occur at times ta, tb, tc, and td. The temperature Texof the external heater is around 100 degrees Celsius between time txand time ta, around 160 degrees Celsius between time taand time tb, around 220 degrees Celsius between time tb and time tc, around 280 degrees Celsius between time tcand time td, and around 340 degrees Celsius between time td and time t2. Each of these time periods lasts around one minute. In this example, the second phase may be considered to start, for example, at time h between times taand tb.

[0464] Therefore, in this example, the temperature of the internal heater is held roughly constant across the first and second phases, and the temperature of the external heater is increased stepwise in 5 steps across the first and second phases.

[0465] During the first and second phases, the user may puff on the article of the system, resulting in an airflow as described earlier, and inhale the aerosol formed.

[0466] During the first phase, the internal heater heats an inner portion of the at least one aerosolgenerating substrate to form an aerosol. As the first phase progresses, heat propagates outwardly from the internal heater to heat more of the inner portion of the at least one aerosol-generating substrate, but an outer portion of the at least one aerosol-generating substrate is not sufficiently heated to form a substantial quantity of aerosol. By time ti , at the end of the first phase, most of the inner portion of the at least one aerosol-generating substrate has been heated to a sufficient temperature to form an aerosol and so is depleted.

[0467] During the second phase, the external heater is at a reasonably high temperature. The external heater, together with some heat that has propagated outwardly from the internal heater, heats the outer portion of the at least one aerosol-generating substrate to form an aerosol. As the second phase progresses, the external heater temperature increases step-wise so as to make heat propagate further inwardly from the external heater to heat more of the at least one aerosolgenerating substrate to form an aerosol. By time t2, at the end of the second phase, most of the outer portion of the at least one aerosol-generating substrate has been heated to a sufficient temperature to form an aerosol and so is depleted. Therefore, with the inner and outer portions of the at least one aerosol-generating substrate depleted, the substrate is substantially entirely depleted at the end of the second phase.

[0468] Figure 10 illustrates a third example of a heating profile for a heating cycle of an aerosolgenerating system according to the present invention. For example, the heating profile of Figure 10 may be used with any of the aerosol-generating devices described with reference to Figures 1 to 7 and may be implemented by the control circuitry 40. Figure 10 shows how temperature T, specifically a temperature Tjnof the internal heater and a temperature Texof the external heater, varies over time t, including over a first phase between times to and ti, and a second phase between times h and t2. There is no pre-heating phase.

[0469] At time to the internal heater is rapidly heated to an operating temperature, which is then maintained for the remainder of the first phase and the second phase. In this example, the operating temperature of the internal heater is around 320 degrees Celsius.

[0470] During the second phase between times h and t2, the temperature of the external heater is rapidly increased from room temperature To to around 200 degrees Celsius, and then linearly increased to around 300 degrees Celsius at time t2.

[0471] Figure 11 shows a schematic cross-sectional view of an aerosol-generating article 102 in accordance with a first embodiment of the present invention for use in the aerosol-generating system 100 of Figure 3. As shown in Figure 11 , the aerosol-generating article 102 has an upstream end 510 and a downstream end 520.

[0472] The aerosol-generating article 102 comprises an aerosol-generating section 104, a downstream section 106, and an upstream section 108. The aerosol-generating article 102 is substantially cylindrical and has a total length of 45 millimetres and an external diameter of 7.2 millimetres.

[0473] The aerosol-generating section 104 has a length of 12 millimetres and an external diameter of 7.2 millimetres.

[0474] The aerosol-generating article 102 also comprises an internal heater in the form of a susceptor element 114 arranged within the aerosol-generating section 104. The susceptor element 114 is arranged longitudinally within the aerosol-generating section 104. As shown in Figure 11 , the susceptor element 114 is positioned centrally within the aerosol-generating section and extends along the longitudinal axis of the aerosol-generating section 104.

[0475] The susceptor element 114 extends from an upstream end of the aerosol-generating section 104 to a downstream end of the aerosol-generating section 104. That is, the susceptor element 114 extends along the entire length of the aerosol-generating section 104. The length of the susceptor element 114 is substantially the same as the length of the aerosol-generating section 104. The susceptor element 114 has a length of 12 millimetres, a width of 5 millimetres and a thickness of 60 micrometres.

[0476] The upstream section 108 is located upstream of the aerosol-generating section 104. The upstream section 108 comprises an upstream element 522. The upstream element 522 is located immediately upstream of the aerosol-generating section 104. The upstream end of the upstream element 522 corresponds to the upstream end 510 of the aerosol-generating article 102. The downstream end of the upstream element 522 abuts the upstream end of the aerosol-generating section 104. The upstream element 522 has a length of 5 millimetres and an external diameter of 7.2 millimetres. The upstream element 522 is a cylindrical segment of cellulose acetate circumscribed by a wrapper (not shown). The RTD of the upstream element 522 is 30 millimetres H2O.

[0477] The downstream section 106 is located downstream of the aerosol-generating section 104. The downstream end of the downstream section 106 corresponds to the downstream end 520 of the aerosol-generating article 102.

[0478] The downstream section 106 comprises a support element 524, an aerosol-cooling element 526, and a mouthpiece element 528.

[0479] The support element 524 is located immediately downstream of the aerosol-generating section 104. The upstream end of the support element 524 abuts the downstream end of the aerosol-generating section 104. The support element 524 has a length of 8 millimetres.

[0480] As shown in Figure 11 , the support element 524 comprises a first hollow tubular element 530. The first hollow tubular element 530 is a hollow cellulose acetate tube. The first hollow tubular element 530 has an internal diameter of 3.25 millimetres and an external diameter of 7.2 millimetres. The first hollow tubular element 530 defines an internal cavity 532 that extends from the upstream end of the first hollow tubular element 530 to the downstream end of the first hollow tubular element 530. The internal cavity 532 is substantially empty. In use, airflow through the internal cavity 532 defined by the first hollow tubular element 530 is substantially unrestricted. The first hollow tubular element 530 does not substantially contribute to the overall RTD of the aerosol-generating article 102. The RTD of the support element 524 is 0 millimetres H2O.

[0481] The aerosol-cooling element 526 is located immediately downstream of the support element 524. The upstream end of the aerosol-cooling element 526 abuts the downstream end of the support element 524. The aerosol-cooling element 526 has a length of 8 millimetres.

[0482] As shown in Figure 11 , the aerosol-cooling element 526 comprises a second hollow tubular element 534. The second hollow tubular element 534 is a hollow cellulose acetate tube. The second hollow tubular element 534 has an internal diameter of 5 millimetres and an external diameter of 7.2 millimetres. The second hollow tubular element 534 defines an internal cavity 536 that extends from the upstream end of the second hollow tubular element 534 to the downstream end of the second hollow tubular element 534. The internal cavity 536 is substantially empty. In use, airflow through the internal cavity 536 defined by the second hollow tubular element 534 is substantially unrestricted. The second hollow tubular element 534 does not substantially contribute to the overall RTD of the aerosol-generating article 102. The RTD of the aerosol-cooling element 526 is 0 millimetres H2O.

[0483] The support element 524 and the aerosol-cooling element 526 together define an intermediate hollow section 540 of the aerosol-generating article 102.

[0484] As shown by the dashed vertical line in Figure 11 , the aerosol-generating article 102 comprises a ventilation zone 550 at a location along the downstream section 106. The distance between the ventilation zone 550 and the downstream end of the downstream section 106 is 18 millimetres. The distance between the ventilation zone 550 and the upstream end of the aerosolgenerating section 104 is 22 millimetres. The distance between the ventilation zone 550 and the upstream end 510 of the aerosol-generating article 102 is 27 millimetres. As shown in Figure 11 , the ventilation zone 550 is at a location along the aerosol-cooling element 526. The ventilation zone 550 comprises a circumferential row of perforations. The perforations extend through the peripheral wall of the second hollow tubular element 534. The ventilation zone 550 is provided 2 millimetres from the upstream end of the second hollow tubular element 534. In use, the perforations allow air flow from the exterior of the aerosol-generating article 102 into the internal cavity 536 defined by the second hollow tubular element 534.

[0485] The mouthpiece element 528 is located immediately downstream of the aerosol-cooling element 526. The upstream end of the mouthpiece element 528 abuts the downstream end of the aerosol-cooling element 526. The downstream end of the mouthpiece element 528 corresponds to the downstream end 520 of the aerosol-generating article 102. The mouthpiece element 528 has a length of 12 millimetres and an external diameter of 7.2 millimetres. The mouthpiece element 528 is a cylindrical segment of low-density, cellulose acetate tow circumscribed by a wrapper (not shown).

[0486] The aerosol-generating section 104 comprises an aerosol-generating substrate comprising a sheet of homogenised plant material. The homogenised plant material is in the form of a cast sheet comprising 60 percent by weight of non-tobacco botanical particles (such as black tea particles), 25 percent by weight of glycerol as aerosol former, 1.5 percent by weight of exogenous nicotine, 3.5 percent by weight of carboxymethyl cellulose binder and 6 percent by weight of cellulose fibres. All weights are expressed on a dry weight basis.

[0487] In use, the aerosol-generating substrate in the aerosol-generating section 104 is heated as described above in relation to Figures 1 to 3. Upon activation of heating, the user draws on the mouthpiece element 542 of the aerosol-generating article 102. When a user draws on the mouthpiece element 542, air is drawn into the aerosol-generating article 102 through the upstream end 548. The drawn air passes through the upstream element 546 to the aerosolgenerating section 104. Heating of the aerosol-generating substrate in the aerosol-generating section 104 releases volatile and semi-volatile compounds, which form an aerosol that is entrained in the drawn air as it flows through the aerosol-generating section 104. The drawn air and entrained aerosol pass through the intermediate hollow section 550 of the aerosol-generating article 102, where they cool and condense. The cooled aerosol then passes through the mouthpiece element 542 of the aerosol-generating article 102 and into the mouth of the user.

[0488] Figure 12 shows a schematic cross-sectional view of an aerosol-generating article 252 in accordance with a second embodiment of the present invention for use in the aerosol-generating system 250 of Figure 5. As shown in Figure 12, the aerosol-generating article 252 has an upstream end 610 and a downstream end 620. The aerosol-generating article 252 comprises an aerosol-generating section 254 and a downstream section 106. In alternative embodiments, an upstream section may additionally be provided upstream of the aerosol-generating section 254. The aerosol-generating article 102 is substantially cylindrical and has a total length of 45 millimetres and an external diameter of 7.2 millimetres.

[0489] The aerosol-generating section 104 has a length of 14 millimetres and an external diameter of 7.2 millimetres. The upstream end of the aerosol-generating section 254 corresponds to the upstream end 610 of the aerosol-generating article 252.

[0490] The downstream section 106 is located downstream of the aerosol-generating section 254. The downstream end of the downstream section 106 corresponds to the downstream end 620 of the aerosol-generating article 252.

[0491] The downstream section 106 comprises an aerosol-cooling element 624 and a mouthpiece element 628.

[0492] The aerosol-cooling element 624 is located immediately downstream of the aerosolgenerating section 254. The upstream end of the aerosol-cooling element 624 abuts the downstream end of the aerosol-generating section 254. The aerosol-cooling element 624 has a length of 24 millimetres.

[0493] As shown in Figure 12, the aerosol-cooling element 624 comprises a hollow tubular element 630. The hollow tubular element 630 is a hollow cardboard tube. The hollow tubular element 630 has an internal diameter of 6.7 millimetres and an external diameter of 7.2 millimetres The hollow tubular element 630 defines an internal cavity 632 that extends from the upstream end of the hollow tubular element 630 to the downstream end of the hollow tubular element 630. The internal cavity 632 is substantially empty. In use, airflow through the internal cavity 632 defined by the hollow tubular element 630 is substantially unrestricted. The hollow tubular element 630 does not substantially contribute to the overall RTD of the aerosol-generating article 252. The RTD of the aerosol-cooling element 624 is 0 millimetres H2O.

[0494] As shown by the dashed vertical line in Figure 12, the aerosol-generating article 252 comprises a ventilation zone 650 at a location along the downstream section 106. The distance between the ventilation zone 650 and the downstream end of the downstream section 106 is 18 millimetres. The distance between the ventilation zone 650 and the upstream end of the aerosolgenerating section 254 is 27 millimetres. As shown in Figure 12, the ventilation zone 550 is at a location along the aerosol-cooling element 624. The ventilation zone 650 comprises a circumferential row of perforations. The perforations extend through the peripheral wall of the hollow tubular element 630. The ventilation zone 650 is provided 13 millimetres from the upstream end of the hollow tubular element 630. In use, the perforations allow air flow from the exterior of the aerosol-generating article 252 into the internal cavity 632 defined by the hollow tubular element 630. The mouthpiece element 628 is located immediately downstream of the aerosol-cooling element 624. The upstream end of the mouthpiece element 628 abuts the downstream end of the aerosol-cooling element 624. The downstream end of the mouthpiece element 628 corresponds to the downstream end 620 of the aerosol-generating article 252. The mouthpiece element 628 has a length of 7 millimetres and an external diameter of 7.2 millimetres. The mouthpiece element 628 is a cylindrical segment of low-density, cellulose acetate tow circumscribed by a wrapper (not shown). The RTD of the mouthpiece element 628 is 8 millimetres H2O.

[0495] The aerosol-generating section 104 comprises an aerosol-generating substrate in the form of cut filler comprising shredded rooibos material, loaded with glycerol as aerosol former and exogenous nicotine. The cut filler has a glycerol content of 5 percent by weight on a dry weight basis and an exogenous nicotine content of 1.5 percent by weight on a dry weight basis.

[0496] In use, the aerosol-generating substrate in the aerosol-generating section 104 is heated as described above in relation to Figures 4 and 5. Upon activation of heating, the user draws on the mouthpiece element 642 of the aerosol-generating article 252. When a user draws on the mouthpiece element 642, air is drawn into the aerosol-generating article 252 through the upstream end 648. The drawn air passes through the aerosol-generating section 104. Heating of the aerosol-generating substrate in the aerosol-generating section 104 releases volatile and semi-volatile compounds, which form an aerosol that is entrained in the drawn air as it flows through the aerosol-generating section 104. The drawn air and entrained aerosol pass through the aerosol-cooling element 624 of the aerosol-generating article 252, where they cool and condense. The cooled aerosol then passes through the mouthpiece element 642 of the aerosolgenerating article 252 and into the mouth of the user.

[0497] The specific embodiments and examples described above illustrate, but do not limit, the invention. It is to be understood that other embodiments of the invention may be made and the specific embodiments and examples described herein are not exhaustive.

[0498] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

CLAIMS1. An aerosol-generating system comprising: an aerosol-generating article comprising: an aerosol-generating section comprising an aerosol-generating substrate, wherein the aerosol-generating substrate comprises at least 5 percent by weight of nontobacco botanical material, on a dry weight basis; an aerosol-generating device comprising: a chamber for receiving at least a portion of the aerosol-generating section of the aerosol-generating article; an external heater extending around at least a portion of the chamber; and control circuitry; and an internal heater arranged inside at least part of the aerosol-generating section when the aerosol-generating article is received within the chamber; wherein the control circuitry is configured to heat the internal heater and the external heater during a heating cycle comprising a first phase and a second phase subsequent to the first phase, wherein the control circuitry is configured to heat the internal heater to a temperature greater than a temperature of the external heater during the first phase, and wherein the control circuitry is configured to heat the external heater to a temperature greater than a temperature of the internal heater during the second phase, wherein the control circuitry is configured to, during the first phase, heat the external heater to or maintain the external heater at a temperature above 50 degrees Celsius, and wherein the control circuitry is configured to heat at least one of the internal heater and the external heater to a maximum temperature of no more than 350 degrees Celsius during the heating cycle.

2. An aerosol-generating system according to claim 1 , wherein the non-tobacco botanical material in the aerosol-generating substrate is selected from rooibos, tea including black tea, apple fibre, rosehip seed, lemon balm stem, peppermint stem, chamomile, verbena, elderflower, oat herb, parsley stem, geranium, lime, kaffir lime, lemon myrtle ambrette seed, tolu balsam, passion berry, timur berry, coffee and combinations thereof.

3. An aerosol-generating system according to claim 1 or 2, wherein the aerosol-generating substrate comprises at least 30 percent by weight of non-tobacco botanical material, on a dry weight basis.

4. An aerosol-generating system according to any preceding claim, wherein the aerosolgenerating substrate is substantially free from tobacco.

5. An aerosol-generating system according to any preceding claim, wherein the aerosolgenerating substrate comprises: at least 50 percent by weight of non-tobacco botanical material, on a dry weight basis; exogenous nicotine; and one or more aerosol formers.

6. An aerosol-generating system according to any preceding claim, wherein the control circuitry is configured to heat the external heater to an external heater temperature during the heating cycle, and wherein the control circuitry is configured to change a difference between the internal heater temperature and the external heater temperature during the heating cycle.

7. An aerosol-generating system according to any preceding claim, wherein the control circuitry is configured to start heating of the internal heater before starting heating of the external heater during the heating cycle.

8. An aerosol-generating system according to any preceding claim, wherein the control circuitry is configured to heat the internal heater to a maximum internal heater temperature, wherein the control circuitry is configured to heat the external heater to a maximum external heater temperature, and wherein the maximum external heater temperature is less than the maximum internal heater temperature.

9. An aerosol-generating system according to any preceding claim, wherein the control circuitry is configured to heat the internal heater to a maximum internal heater temperature during the heating cycle, wherein the control circuitry is configured to heat the external heater to a maximum external heater temperature during the heating cycle, and wherein the internal heater reaches the maximum internal heater temperature at a different time to the external heater reaching the maximum external heater temperature during the heating cycle.

10. An aerosol-generating system according to any preceding claim, wherein the chamber defines a longitudinal direction along which the aerosol-generating article may be inserted into the chamber, wherein the external heater has a length extending in the longitudinal direction, wherein the internal heater has a length extending in the longitudinal direction, and wherein a ratio of the length of the internal heater to the length of the external heater is between 0.2 and 5.

11. An aerosol-generating system according to claim 10, wherein the ratio of the length of the internal heater to the length of the external heater may be between 0.2 and 4, between 0.2 and 3, between 0.2 and 2, between 0.3 and 1.9, between 0.4 and 1.9, between 0.5 and 1.9, between 0.6 and 1.8, between 0.7 and 1.7, between 0.8 and 1.6, between 0.9 and 1.5, or between 1.1 and 1.4, or between 1.1 and 1.3.

12. An aerosol-generating system according to any preceding claim, wherein the control circuitry is configured to determine when a user takes puff on the aerosol-generating system.

13. An aerosol-generating system according to any preceding claim, wherein the controller is configured to heat the internal heater to a maximum temperature of no more than 420 degrees Celsius during the heating cycle and configured to heat the external heater to a maximum temperature of no more than 350 degrees during the heating cycle.

14. An aerosol-generating system according to any preceding claim, wherein the aerosolgenerating article comprises the internal heater, wherein the internal heater comprising an internal susceptor element positioned within the aerosol-generating section, wherein the aerosolgenerating device comprises an inductor coil, and wherein the control circuitry is configured to provide an alternating electric current to the inductor coil such that, in use, the inductor coil generates an alternating magnetic field to inductively heat the internal susceptor element.

15. An aerosol-generating system according to any preceding claim, wherein the temperature of the external heater is increased in a stepwise manner across the first phase and the second phase.

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