WO2024003194A1

WO2024003194A1 - Aerosol-generating article comprising a perforated hollow tubular substrate element

Info

Publication number: WO2024003194A1
Application number: PCT/EP2023/067740
Authority: WO
Inventors: Gennaro CAMPITELLI
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2022-06-30
Filing date: 2023-06-28
Publication date: 2024-01-04
Anticipated expiration: 2024-12-30
Also published as: KR20250026844A; EP4547047A1; JP2025520590A; CN119317369A; US20250295163A1

Abstract

An aerosol-generating article (10) comprising: a rod of aerosol-generating substrate (12) and a downstream section(14) provided downstream of the rod of aerosol-generating substrate (12), wherein the rod of aerosol-generating substrate (12) comprises: a hollow tubular substrate element (40) formed of homogenised tobacco material and defining a longitudinal cavity (44) providing an unrestricted flow channel through the hollow tubular substrate element (40); an outer wrapper (60) circumscribing the hollow tubular substrate element (40) and arranged such that an empty space (90) is defined between at least a part of the external surface of the hollow tubular substrate element (40) and the outer wrapper; wherein the hollow tubular substrate element (40) comprises a plurality of perforations (46) providing fluid communication between the longitudinal cavity (44) of the hollow tubular substrate element (40) and the empty space (90) between at least a part of the external surface of the hollow tubular substrate element (40) and the outer wrapper (60), wherein the plurality of perforations (46) of the hollow tubular substrate element (40) is formed through a peripheral wall of the hollow tubular substrate element (40), and wherein the outer wrapper (60) comprises a plurality of perforations (66) overlying the hollow tubular substrate element (40).

Description

AEROSOL-GENERATING ARTICLE COMPRISING A PERFORATED HOLLOW TUBULAR SUBSTRATE ELEMENT

The present invention relates to an aerosol-generating article comprising a rod of aerosolgenerating substrate that is adapted to produce an inhalable aerosol upon heating.

Aerosol-generating articles in which an aerosol-generating substrate, such as a tobaccocontaining substrate, is heated rather than combusted, are known in the art. Typically, in such heated smoking articles an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

A number of prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosolgenerating devices in which an aerosol is generated by the transfer of heat from one or more electrical heater elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article. For example, electrically heated aerosol-generating devices have been proposed that comprise an internal heater blade which is adapted to be inserted into the aerosol-generating substrate. Use of an aerosol-generating article in combination with an external heating system is also known. For example, WO-A-2020/1 15151 describes the provision of an external heating element arranged around the periphery of the aerosol-generating article when the aerosol-generating article is received in a cavity of the aerosol-generating device. As an alternative, inductively heatable aerosol-generating articles comprising an aerosol-generating substrate and a susceptor arranged within the aerosol-generating substrate have been proposed by WO-A-2015/176898.

In general, it can be difficult to provide efficient heating of an aerosol-generating substrate throughout the whole rod of the substrate. The portions of the substrate closest to the heating element will inevitably be heated most effectively whilst the imperfect transfer of heat through the substrate will mean that portions of the substrate furthest from the heating element may not be effectively heated. The generation of aerosol from these portions of the substrate that are not effectively heated is therefore not optimal and in some cases, parts of the substrate may not reach a sufficiently high temperature during use for an aerosol to be generated at all. For example, where an external heating element is used to heat a rod of aerosol-generating substrate, as described above, the central portion of the rod of aerosol-generating substrate is unlikely to generate as much aerosol as the outer portions of the rod and in some cases, may not generate any aerosol. Overall, the generation of aerosol from the aerosol-generating rod is therefore likely to be inefficient, with potential waste of a portion of the aerosol-generating substrate.

In addition, aerosol is generally not immediately generated by the aerosol-generating substrate upon activation of a heating element. This is because there is a pre-heating time after activation of a heating element during which the aerosol-generating substrate is heated to a temperature required for aerosol generation. As such, there may be a relatively long duration between activation of a heating element and generation of a seasonally acceptable aerosol for inhalation by a user.

It would therefore be desirable to provide an aerosol-generating article having an aerosolgenerating substrate that is adapted to provide more efficient aerosolisation of the aerosolgenerating substrate and that reduces waste of the substrate materials, such as tobacco. It would also be desirable to provide such an aerosol-generating article that can achieve a relatively short pre-heating time so that a seasonally acceptable aerosol can be delivered to a user shortly after initiation of heating of the aerosol-generating substrate. It would also be desirable to provide such an aerosol-generating article that can provide optimised delivery of aerosol from the aerosolgenerating substrate. It would be particularly desirable to provide such an aerosol-generating article with a relatively simple design so that it can be manufactured in a cost effective way and incorporated into existing product designs. It would be further desirable to provide such an article that can be readily adapted so that it can be heated in a variety of types of heating device, including inductive and resistive heating devices.

The present disclosure relates to an aerosol-generating article. The aerosol-generating article may comprise a rod of aerosol-generating substrate. The aerosol-generating article may comprise a downstream section provided downstream of the rod of aerosol-generating substrate. The rod of aerosol-generating substrate may comprise a hollow tubular substrate element. The hollow tubular substrate element may be formed of homogenised tobacco material. The hollow tubular substrate element may define a longitudinal cavity providing an unrestricted flow channel through the hollow tubular substrate element. The aerosol-generating substrate may comprise an outer wrapper circumscribing the hollow tubular substrate element. The outer wrapper may be arranged such that an empty space is defined between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper. The hollow tubular substrate element may comprise a plurality of perforations. The plurality of perforations may provide fluid communication between the longitudinal cavity of the hollow tubular substrate element and the empty space between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper.

According to the present invention there is provided an aerosol-generating article comprising: a rod of aerosol-generating substrate and a downstream section provided downstream of the rod of aerosol-generating substrate, wherein the rod of aerosol-generating substrate comprises: a hollow tubular substrate element formed of homogenised tobacco material and defining a longitudinal cavity providing an unrestricted flow channel through the hollow tubular substrate element; an outer wrapper circumscribing the hollow tubular substrate element and arranged such that an empty space is defined between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper; wherein the hollow tubular substrate element comprises a plurality of perforations providing fluid communication between the longitudinal cavity of the hollow tubular substrate element and the empty space between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper.

As used herein with reference to the present invention, 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.

As used herein with reference to the present invention, 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 generate an aerosol.

As used herein with reference to the present invention, 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.

As used herein with reference to the present invention, the term “rod” is used to denote a generally cylindrical element having a substantially circular, oval or elliptical cross-section.

Aerosol-generating articles according to the present invention have a downstream end through which, in use, an aerosol exits the aerosol-generating article for delivery to a user. The downstream end of the aerosol-generating article may also be referred to as the proximal end or mouth end of the aerosol-generating article. In use, a user draws directly or indirectly on the downstream end of the aerosol-generating article to inhale an aerosol generated by the aerosolgenerating article.

Aerosol-generating articles according to the present invention have an upstream end. The upstream end is opposite the downstream end. The upstream end of the aerosol-generating article may also be referred to as the distal end of the aerosol-generating article.

Components of aerosol-generating articles according to the present invention may be described as being upstream or downstream of one another based on their relative positions between the upstream end of the aerosol-generating article and the downstream end of the aerosol-generating article.

As used herein with reference to the present invention, the term “longitudinal” refers to the direction between the upstream end and the opposed downstream end of the aerosol-generating article. As used herein with reference to the present invention, the term “transverse” is used to describe the direction perpendicular to the longitudinal direction.

As used herein with reference to the present invention, the term “cross-section” is used to refer to the transverse cross-section of the aerosol-generating article or component thereof unless stated otherwise.

As used herein with reference to the present invention, the terms “hollow tubular element” and “hollow tubular substrate element” denote a generally elongate element defining a lumen or airflow passage along a longitudinal axis thereof. In particular, the term "tubular" is used with reference to a tubular element having a substantially cylindrical cross-section and defining at least one airflow conduit establishing an uninterrupted fluid communication between an upstream end of the tubular element and a downstream end of the tubular element. However, it will be understood that alternative geometries (for example, alternative cross-sectional shapes) of the tubular element may be possible. The hollow tubular element may be an individual, discrete element of the aerosol-generating article which has a defined length and thickness.

As used herein with reference to the present invention, the term “homogenised tobacco material” encompasses any material formed by the agglomeration of tobacco particles. The homogenised tobacco material may be produced by casting, extrusion, paper making processes or any other suitable processes known in the art.

As used herein with reference to the present invention, the term “tobacco particles” describes particles of any plant member of the genus Nicotiana. The term “tobacco particles” encompasses ground or powdered tobacco leaf lamina, ground or powdered tobacco leaf stems, tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco. Preferably, the tobacco particles are substantially all derived from tobacco leaf lamina. By contrast, isolated nicotine and nicotine salts are compounds derived from tobacco but are not considered tobacco particles for purposes of the present invention.

As described above, the present invention provides a hollow tubular substrate element and an outer wrapper circumscribing the hollow tubular substrate element and arranged such that an empty space is defined between at least part of the external surface of the hollow tubular substrate element and the outer wrapper. As such, the empty space is located externally of the hollow tubular substrate element.

The provision of a hollow tubular substrate element defining a longitudinal cavity, an empty space located externally of the hollow tubular substrate element, and a plurality of perforations through the wall of the hollow tubular substrate element providing fluid communication between the longitudinal cavity and the empty space may advantageously enable aerosol to be generated and released from both the internal surface and the external surface of the hollow tubular substrate element. Aerosol released from the external surface of the hollow tubular substrate element into the empty space may be drawn into the longitudinal cavity of the hollow tubular substrate element through the plurality of perforations as the consumer draws on the aerosolgenerating article. This may advantageously increase the quantity of aerosol generated from the aerosol-generating substrate per puff. This may also enable a seasonally acceptable aerosol to be generated more quickly upon starting heating of the aerosol-generating substrate. As such, this may reduce a pre-heating time of the aerosol-generating article. In particular, where the aerosol-generating substrate is heated with external heating means, a seasonally acceptable aerosol may be generated more quickly due to the proximity of the external surface of the hollow tubular substrate element to the external heating means.

In addition, the provision of a plurality of perforations providing fluid communication between the longitudinal cavity and the empty space may advantageously increase a level of turbulence in the longitudinal cavity of the hollow tubular substrate element, for example, when the consumer draws on the aerosol-generating substrate. This may enhance mixing of air and aerosol-forming components that are released from the hollow tubular substrate element, thereby improving aerosol generation.

The provision of a substrate element in a tubular form may also advantageously enable the amount of tobacco material in the aerosol-generating substrate to be optimised so that aerosol can be efficiently generated from the aerosol-generating substrate upon heating. The tubular form also removes a central portion of homogenised tobacco material that would potentially not be heated as effectively as an outer portion, in particular, in an aerosol-generating device comprising external heating means. Overall, the amount of tobacco material can therefore be significantly reduced compared to conventional solid plugs of homogenised tobacco material and tobacco waste can be reduced. For example, it has been found that the amount of tobacco material used in the hollow tubular substrate element of aerosol-generating articles according to the present invention can be reduced by up to 40 percent compared to the amount of tobacco material used in the solid plug of substrate in a conventional aerosol-generating article, whilst retaining a similar delivery of aerosol to the consumer.

The amount of tobacco material provided in the substrate may be readily adapted through controlling the parameters of the hollow tubular substrate element, such as the density of a peripheral wall of the hollow tubular substrate element and the wall thickness. In this way, it may be possible to adapt the hollow tubular substrate element so that it matches the heating zone of an associated aerosol-generating device. The proportion of the aerosol-generating substrate that can be heated to the necessary temperature for aerosol generation may therefore be maximised so that the generation of aerosol from the aerosol-generating substrate may be optimised.

The hollow tubular substrate element has a relatively simple structure that may be produced in a straightforward and cost effective way, using existing apparatus. The hollow tubular substrate element can then be incorporated into aerosol-generating articles with other components, using known assembly methods and apparatus. As described above, the hollow tubular substrate element is formed of homogenised tobacco material. Preferably, the hollow tubular substrate element is formed of one or more layers of homogenised tobacco material, such as cast leaf.

Preferably, the hollow tubular substrate element is formed of 2 or more overlapping layers of homogenised tobacco material, more preferably 3 or more overlapping layers of homogenised tobacco material.

The hollow tubular substrate element is preferably formed of up to 10 overlapping layers of homogenised tobacco material, more preferably up to 5 overlapping layers of homogenised tobacco material. For example, the hollow tubular substrate element may be formed of between about 2 and about 10 overlapping layers of homogenised tobacco material, or between about 3 and about 5 overlapping layers of homogenised tobacco material.

Preferably, the plurality of overlapping layers of homogenised tobacco material are directly overlying each other so that adjacent layers are in direct contact with each other, without intermediate layers.

The multi-layered arrangement of the layers may provide a relatively dense structure which has sufficient structural rigidity to provide the aerosol-generating substrate in an aerosolgenerating article without the need for any additional support, such as carrier layers or internal support members within the longitudinal cavity.

Preferably the layers of homogenised tobacco material are in sheet form. As used herein with reference to the present invention, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof.

The hollow tubular substrate element may have a length of at least about 5 millimetres, or at least about 7 millimetres, or at least about 10 millimetres.

The hollow tubular substrate element may have a length of up to about 30 millimetres, up to about 25 millimetres, or up to about 20 millimetres.

For example, the hollow tubular substrate element may have a length of between about 5 millimetres and about 30 millimetres, or between about 7 millimetres and about 25 millimetres, or between about 10 millimetres and about 20 millimetres.

Preferably, the hollow tubular substrate element has a length of about 12 millimetres.

As discussed above, the length of the hollow tubular substrate element may advantageously be matched to the longitudinal dimensions of the heating element in the corresponding aerosol-generating device which will be used to heat the aerosol-generating article. In this way, as much as possible of the aerosol-generating substrate can be heated during use, in order to optimise the amount of aerosol that can be generated and reduce the amount of tobacco waste.

Preferably, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is at least about 0.1. More preferably, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is at least about 0.15. More preferably, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is at least about 0.2.

Preferably, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is up to about 0.6. More preferably, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is up to about 0.55. More preferably, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is up to about 0.5.

For example, the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article may be between about 0.1 and about 0.6, more preferably between about 0.15 and about 0.55, more preferably between about 0.2 and about 0.5.

Preferably, the hollow tubular substrate element has an external diameter less than an external diameter of the aerosol-generating article.

Preferably, the hollow tubular substrate element may have an external diameter of at least about 5 millimetres, or at least about 5.5 millimetres, or at least 6 millimetres.

Preferably, the hollow tubular substrate element may have an external diameter of up to about 9 millimetres, or up to about 8 millimetres, or up to about 7.5 millimetres.

For example, the hollow tubular substrate element may have an external diameter of between about 5 millimetres and about 9 millimetres, or between about 5.5 millimetres and 8 millimetres, or between about 6 millimetres and 7.5 millimetres.

Preferably, the external diameter of the hollow tubular substrate element is substantially constant along the length of the hollow tubular substrate. As an alternative, different portions of the hollow tubular substrate element may have different external diameters.

As used herein with reference to the present invention, the term “external diameter” refers to the maximum diameter of the aerosol-generating article or component thereof, in the transverse direction of the aerosol-generating article, at a position along the length of the aerosol-generating article or component thereof. Where a range or value for an external diameter of the aerosolgenerating article or component thereof is described herein, the external diameter of the aerosolgenerating article or component thereof along the entire length of the aerosol-generating article or component thereof may fall within the same range or have the same value. In other words, where a range or value for an external diameter of the aerosol-generating article or component thereof is described herein, the external diameter of the aerosol-generating article or component thereof at all positions along the length of the aerosol-generating article or component thereof may fall within the same range or have the same value.

The external diameter of the hollow tubular substrate element does not include the width of any other component of the aerosol-generating substrate located externally of the hollow tubular substrate element. The hollow tubular substrate element has a peripheral wall which defines the longitudinal cavity. A wall thickness of the hollow tubular substrate element may be selected based on a desired amount of tobacco material within the hollow tubular substrate. A wall thickness of the hollow tubular substrate element may also be selected such that the hollow tubular substrate element has a sufficiently high rigidity that it can be self-supporting. A wall thickness of the hollow tubular substrate may also be selected such that the longitudinal cavity has a cross-sectional area that provides the hollow tubular substrate element with a desired resistance to draw (RTD).

The hollow tubular substrate element may have a wall thickness that is at least about 4 percent of an external diameter of the hollow tubular substrate element, or at least about 5 percent of an external diameter of the hollow tubular substrate element, or at least about 6 percent of an external diameter of the hollow tubular substrate element.

The hollow tubular substrate element may have a wall thickness that is up to about 40 percent of an external diameter of the hollow tubular substrate element, or up to about 30 percent of an external diameter of the hollow tubular substrate element, or up to about 20 percent of an external diameter of the hollow tubular substrate element.

For example, the hollow tubular substrate element may have a wall thickness that is between about 4 percent and about 40 percent of an external diameter of the hollow tubular substrate element, or between about 5 percent and about 30 percent of an external diameter of the hollow tubular substrate element, or between about 6 percent and about 20 percent of an external diameter of the hollow tubular substrate element.

Preferably, the hollow tubular substrate element has a wall thickness of about 7 percent of an external diameter of the hollow tubular substrate element.

The hollow tubular substrate element may have a wall thickness of at least about 0.3 millimetres, or at least about 0.35 millimetres, or at least about 0.4 millimetres.

The hollow tubular substrate element may have a wall thickness of up to about 3 millimetres, or up to about 2 millimetres, or up to about 1 millimetre.

For example, the hollow tubular substrate element may have a wall thickness of between about 0.3 millimetres and about 3 millimetres, or between about 0.35 millimetres and about 2 millimetres, or between about 0.4 millimetres and about 1 millimetre.

The hollow tubular substrate element may have a wall thickness of about 0.5 millimetres.

As described above, the longitudinal cavity provides an unrestricted flow channel through the hollow tubular substrate element. This means that the hollow tubular substrate element provides a negligible level of resistance to draw (RTD). The term “negligible level of RTD” is used to describe an RTD of less than 1 mm H₂O per 10 millimetres of length of the hollow tubular substrate element, preferably less than 0.4 mm H₂O per 10 millimetres of length of the hollow tubular substrate element, more preferably less than 0.1 mm H₂O per 10 millimetres of length of the hollow tubular substrate element. The longitudinal cavity should therefore be free from any components that would obstruct the flow of air in a longitudinal direction. Preferably, the longitudinal cavity is substantially empty. More preferably, the longitudinal cavity is empty.

The longitudinal cavity may also be referred to as a longitudinal airflow channel.

The longitudinal cavity extends between the ends of the hollow tubular substrate element and is preferably open at both the upstream and downstream ends. The open upstream end may provide the main air inlet for drawing air through the aerosol-generating article when the consumer puffs on the article. The longitudinal cavity may therefore provide the main passageway for the flow of air and aerosol through the article.

The diameter of the longitudinal cavity corresponds to the internal diameter of the hollow tubular substrate element.

The longitudinal cavity may have a diameter of at least about 1 millimetre, or at least about

2 millimetres, or at least about 3 millimetres.

The longitudinal cavity may have a diameter of up to about 8 millimetres, or up to about 7 millimetres, or up to about 6.5 millimetres.

For example, the longitudinal cavity may have a diameter of between about 1 millimetre and about 8 millimetres, or between about 2 millimetres and about 7 millimetres, or between about

3 millimetres and about 6.5 millimetres.

The longitudinal cavity may have a diameter of about 6 millimetres.

The diameter of the longitudinal cavity may be selected so that the volume of the cavity is sufficiently large that it provides a desired level of airflow, whilst also retaining a sufficient wall thickness. This is necessary so that there is a sufficient amount of tobacco material provided within the hollow tubular substrate element and so that the hollow tubular substrate element has a sufficiently high rigidity that it can be self-supporting.

Preferably, the longitudinal cavity has a substantially constant cross-sectional shape and size along the length of the hollow tubular substrate. However, one or both of the cross-sectional shape and size of the longitudinal cavity may vary along the length of the hollow tubular substrate element.

Preferably, the longitudinal cavity has a transverse cross-section that is substantially circular. Alternatively, the longitudinal cavity may have a transverse cross-section that is substantially oval.

The longitudinal cavity may have a constant diameter along the length of the hollow tubular substrate element. However, the diameter of the longitudinal cavity may vary along the length of the hollow tubular substrate element.

As discussed above, the hollow tubular substrate element comprises a plurality of perforations providing fluid communication between the longitudinal cavity of the hollow tubular substrate element and the empty space between at least part of the external surface of the hollow tubular substrate element and the outer wrapper. The plurality of perforations are formed through the peripheral wall of the hollow tubular substrate element. The provision of the plurality of perforations may enable aerosol generated from outer portions of the hollow tubular substrate element and released into the empty space to be drawn into the longitudinal cavity of the hollow tubular substrate element as the consumer draws through the aerosol-generating article. The provision of the plurality of perforations may increase a level of turbulence in the longitudinal cavity of the hollow tubular substrate element. This may enhance mixing of air and aerosolforming components that are released from the hollow tubular substrate element, thereby improving aerosol generation.

Preferably, the plurality of perforations are arranged in one or more rows extending circumferentially around the hollow tubular substrate element. In other words, the hollow tubular substrate element preferably comprises one or more rows of perforations extending circumferentially around the hollow tubular substrate element.

The hollow tubular substrate element may comprise at least two rows of perforations extending circumferentially around the hollow tubular substrate element.

The hollow tubular substrate element may comprise up to five rows of perforations extending circumferentially around the hollow tubular substrate element.

The circumferential rows of perforations may follow various patterns. For example, the circumferential row of perforations may be arranged circularly or helically around the hollow tubular substrate element.

Preferably, each circumferential row of perforations comprises between 8 and 30 perforations.

The plurality of perforations may be formed using suitable known methods such as online during manufacturing of the aerosol-generating article.

The plurality of perforations may comprise at least one perforation having a maximum dimension of at least 200 micrometres, or at least 300 micrometres, or at least about 400 micrometres, or at least about 500 micrometres.

Where the perforation is substantially circular, the maximum dimension of the perforation is the diameter of the perforation. The plurality of perforations may comprise at least one perforation having a maximum dimension of up to about 1 millimetre, or up to about 900 micrometres, or up to about 800 micrometres, or up to about 700 micrometres.

The plurality of perforations may comprise at least one perforation having a maximum dimension of between about 200 micrometres and about 1 millimetre, or between about 200 micrometres and about 900 micrometres, or between about 200 micrometres and 800 micrometres, or between about 200 micrometres and about 700 micrometres.

The plurality of perforations may comprise at least one perforation having a maximum dimension of between about 300 micrometres and about 1 millimetre, or between about 300 micrometres and about 900 micrometres, or between about 300 micrometres and 800 micrometres, or between about 300 micrometres and about 700 micrometres.

The plurality of perforations may comprise at least one perforation having a maximum dimension of between about 400 micrometres and about 1 millimetre, or between about 400 micrometres and about 900 micrometres, or between about 400 micrometres and 800 micrometres, or between about 400 micrometres and about 700 micrometres.

The plurality of perforations may comprise at least one perforation having a maximum dimension of between about 500 micrometres and about 1 millimetre, or between about 500 micrometres and about 900 micrometres, or between about 500 micrometres and 800 micrometres, or between about 500 micrometres and about 700 micrometres.

Each of the plurality of perforations may have a maximum dimension of at least 200 micrometres, at least 300 micrometres, at least 400 micrometres, or at least 500 micrometres.

Each of the plurality of perforations may have a maximum dimension of up to about 1 millimetre, or up to about 900 micrometres, or up to about 800 micrometres, or up to about 700 micrometres.

Each of the plurality of perforations may have a maximum dimension of between about 200 micrometres and about 1 millimetre, or between about 200 micrometres and about 900 micrometres, or between about 200 micrometres and 800 micrometres, or between about 200 micrometres and about 700 micrometres.

Each of the plurality of perforations may have a maximum dimension of between about 300 micrometres and about 1 millimetre, or between about 300 micrometres and about 900 micrometres, or between about 300 micrometres and 800 micrometres, or between about 300 micrometres and about 700 micrometres.

Each of the plurality of perforations may have a maximum dimension of between about 400 micrometres and about 1 millimetre, or between about 400 micrometres and about 900 micrometres, or between about 400 micrometres and 800 micrometres, or between about 400 micrometres and about 700 micrometres.

Each of the plurality of perforations may have a maximum dimension of between about 500 micrometres and about 1 millimetre, or between about 500 micrometres and about 900 micrometres, or between about 500 micrometres and 800 micrometres, or between about 500 micrometres and about 700 micrometres.

The plurality of perforations may comprise at least one perforation having an opening area of at least about 0.01 millimetres squared, or at least about 0.03 millimetres square, or at least about 0.05 millimetres squared, or at least about 0.07 millimetres squared.

The plurality of perforations may comprise at least one perforation having an opening area of no more than 1 millimetre squared, or no more than 0.8 millimetres squared, or no more than 0.5 millimetres squared, or no more than 0.3 millimetres squared, or no more than 0.1 millimetres squared.

The plurality of perforations may comprise at least one perforation having an opening area of between about 0.01 millimetres squared and about 1 millimetre squared, or between about 0.01 millimetres squared and about 0.8 millimetres squared, or between about 0.01 millimetres squared and about 0.5 millimetres squared, or between about 0.01 millimetres squared and about 0.3 millimetres squared, or between about 0.01 millimetres squared and about 0.1 millimetres squared.

The plurality of perforations may comprise at least one perforation having an opening area of between about 0.03 millimetres squared and about 1 millimetre squared, or between about 0.03 millimetres squared and about 0.8 millimetres squared, or between about 0.03 millimetres squared and about 0.5 millimetres squared, or between about 0.03 millimetres squared and about 0.3 millimetres squared, or between about 0.03 millimetres squared and about 0.1 millimetres squared.

The plurality of perforations may comprise at least one perforation having an opening area of between about 0.05 millimetres squared and about 1 millimetre squared, or between about 0.05 millimetres squared and about 0.8 millimetres squared, or between about 0.05 millimetres squared and about 0.5 millimetres squared, or between about 0.05 millimetres squared and about 0.3 millimetres squared, or between about 0.05 millimetres squared and about 0.1 millimetres squared.

The plurality of perforations may comprise at least one perforation having an opening area of between about 0.07 millimetres squared and about 1 millimetre squared, or between about 0.07 millimetres squared and about 0.8 millimetres squared, or between about 0.07 millimetres squared and about 0.5 millimetres squared, or between about 0.07 millimetres squared and about 0.3 millimetres squared, or between about 0.07 millimetres squared and about 0.1 millimetres squared.

Each of the plurality of perforations may have an opening area of at least about 0.01 millimetres squared, or at least about 0.03 millimetres square, or at least about 0.05 millimetres squared, or at least about 0.07 millimetres squared.

Each of the plurality of perforations may have an opening area of no more than 1 millimetre squared, or no more than 0.8 millimetres squared, or no more than 0.5 millimetres squared, or no more than 0.3 millimetres squared, or no more than 0.1 millimetres squared.

Each of the plurality of perforations may have an opening area of between about 0.01 millimetres squared and about 1 millimetre squared, or between about 0.01 millimetres squared and about 0.8 millimetres squared, or between about 0.01 millimetres squared and about 0.5 millimetres squared, or between about 0.01 millimetres squared and about 0.3 millimetres squared, or between about 0.01 millimetres squared and about 0.1 millimetres squared. Each of the plurality of perforations may have an opening area of between about 0.03 millimetres squared and about 1 millimetre squared, or between about 0.03 millimetres squared and about 0.8 millimetres squared, or between about 0.03 millimetres squared and about 0.5 millimetres squared, or between about 0.03 millimetres squared and about 0.3 millimetres squared, or between about 0.03 millimetres squared and about 0.1 millimetres squared.

Each of the plurality of perforations may have an opening area of between about 0.05 millimetres squared and about 1 millimetre squared, or between about 0.05 millimetres squared and about 0.8 millimetres squared, or between about 0.05 millimetres squared and about 0.5 millimetres squared, or between about 0.05 millimetres squared and about 0.3 millimetres squared, or between about 0.05 millimetres squared and about 0.1 millimetres squared.

Each of the plurality of perforations may have an opening area of between about 0.07 millimetres squared and about 1 millimetre squared, or between about 0.07 millimetres squared and about 0.8 millimetres squared, or between about 0.07 millimetres squared and about 0.5 millimetres squared, or between about 0.07 millimetres squared and about 0.3 millimetres squared, or between about 0.07 millimetres squared and about 0.1 millimetres squared.

The plurality of perforations may have a total opening area of at least about 0.05 millimetres squared, or at least about 0.2 millimetres squared, or at least about 0.35 millimetres squared, or at least about 0.5 millimetres squared.

The plurality of perforations may have a total opening area of up to about 30 millimetres squared, or up to about 25 millimetres squared, or up to about 15 millimetres squared, or up to about 10 millimetres squared, or up to about 5 millimetres squared.

The plurality of perforations may have a total opening area of between about 0.05 millimetres squared and about 30 millimetres squared, or between about 0.05 millimetres squared and about 25 millimetres squared, or between about 0.05 millimetres squared and about 15 millimetres squared, or between about 0.05 millimetres squared and about 10 millimetres squared, or between about 0.05 millimetres squared and about 5 millimetres squared.

The plurality of perforations may have a total opening area of between about 0.05 millimetres squared and about 30 millimetres squared, or between about 0.05 millimetres squared and about 25 millimetres squared, or between about 0.05 millimetres squared and about 15 millimetres squared, or between about 0.05 millimetres squared and about 10 millimetres squared, or between about 0.05 millimetres squared and about 5 millimetres squared. The plurality of perforations may have a total opening area of between about 0.05 millimetres squared and about 30 millimetres squared, or between about 0.05 millimetres squared and about 25 millimetres squared, or between about 0.05 millimetres squared and about 15 millimetres squared, or between about 0.05 millimetres squared and about 10 millimetres squared, or between about 0.05 millimetres squared and about 5 millimetres squared.

Preferably, both the shape and the size of each of the plurality of perforations are the same. This may advantageously simplify manufacturing of the plurality of perforations.

The plurality of perforations may be substantially circular in shape. The plurality of perforations may be rectangular or square in shape.

The hollow tubular substrate element may have a ventilation level of at least about 5 percent, or at least about 10 percent, or at least about 15 percent.

The hollow tubular substrate element may have a ventilation level of up to about 60 percent, or up to about 45 percent, or up to about 30 percent.

As used herein with reference to the present invention, the term “ventilation level” is used to describe a volume ratio between airflow admitted into the hollow tubular substrate element via perforations through the wall of the hollow tubular substrate element and the sum of the airflow into the hollow tubular substrate element via the upstream end of the hollow tubular substrate element and the airflow into the hollow tubular substrate element via perforations through the wall of the hollow tubular substrate element. A greater ventilation level may mean a higher proportion of aerosol from the empty space is drawn into the hollow cavity.

The rod of aerosol-generating substrate may comprise one or more protrusions extending across the empty space between the external surface of the hollow tubular substrate element and the outer wrapper. The one or more protrusions preferably extend from the external surface of the hollow tubular substrate element to the internal surface of the outer wrapper. As such, a width of the one or more protrusions is about the same as a width of the empty space as measured in the radial direction. The width of the one or more protrusions is not taken into account when measuring the external diameter of the hollow tubular substrate element.

As used herein with reference to the present invention, the term “radial” is used to describe a direction identified by a line extending in a plane perpendicular to the central longitudinal axis of the aerosol-generating article and passing through the point at which the central longitudinal axis intersects the perpendicular plane. Thus, as used herein with reference to the present invention, the term “radial direction” refers to a direction perpendicular to the central longitudinal axis and is used, for example, when describing an aerosol-generating article having a substantially cylindrical shape.

The outer wrapper may be wrapped around the one or more protrusions to help to anchor the hollow tubular substrate element in place and retain the empty space between the hollow tubular substrate element and the outer wrapper. The one or more protrusions may be integral with the hollow tubular substrate element.

The one or more protrusions may be non-integral with the hollow tubular substrate element. That is, the one or more protrusions may be physically distinct from the hollow tubular substrate element. The one or more protrusions may be adhered or otherwise attached directly or indirectly to the external surface of the hollow tubular substrate element.

The one or more protrusions may be integral with the outer wrapper. The one or more protrusions may be formed by a fold or a crease in the outer wrapper. The one or more protrusions may be formed by crimping the outer wrapper.

The one or more protrusions may be non-integral with the outer wrapper. For example, the one or more protrusions may be adhered or otherwise attached directly or indirectly to the internal surface of the outer wrapper.

The one or more protrusions may be formed of homogenised tobacco material. The one or more protrusions may be formed of the same material as the hollow tubular substrate element. Aerosol may advantageously be generated and released from such protrusions into the empty space. This may further reduce the preheating time of the aerosol-generating article.

The one or more protrusions may be formed of a different material from the hollow tubular substrate element.

The one or more protrusions may extend the entire length of the hollow tubular substrate element. Alternatively, the one or more protrusions may not extend the entire length of the hollow tubular substrate element. The one or more protrusions may extend a portion of the length of the hollow tubular substrate element.

The one or more protrusions may be in the form of one or more discs. The discs may be inserted onto the hollow tubular substrate element. The discs may have an external diameter about the same as an external diameter of the aerosol-generating article. The discs may have an internal diameter about the same as the external diameter of the hollow tubular substrate element. The one or more discs may be arranged such that it does not substantially hinder or prevent aerosol in the empty space from being drawn into the longitudinal cavity of the hollow tubular substrate element through the plurality of perforations of the hollow tubular substrate element.

The one or more protrusions may be arranged so that the empty space is non-continuous. That is, the empty space may comprise a plurality of channels defined by the one or more protrusions. The plurality of channels of the empty space may be arranged substantially longitudinally along aerosol-generating substrate. For example, the empty space may comprise a plurality of longitudinal channels defined by two or more protrusions extending the entire length of the hollow tubular substrate element.

Where the aerosol-generating substrate comprises a plurality of protrusions, the plurality of protrusions may be about equally spaced around the hollow tubular substrate element. The empty space may be an annular empty space.

The empty space may have an annular cross-section.

The empty space may be annular along the entire length of the hollow tubular substrate element. That is, the empty space may have an annular cross-section along the entire length of the hollow tubular substrate element.

The aerosol-generating substrate may comprise an upstream element adjacent to the upstream end of the hollow tubular substrate element. By providing an upstream element, the hollow tubular substrate element may be more protected than a hollow tubular substrate element without an upstream element upstream of the hollow tubular substrate element. The upstream element may also help to define the empty space between the hollow tubular substrate element and the outer wrapper. The upstream element may be sized and positioned such that the empty space does not extend to the upstream end of the aerosol-generating article or the aerosolgenerating substrate.

The upstream element may abut the upstream end of the hollow tubular substrate element. The upstream element may be affixed to the hollow tubular substrate element.

The upstream element may be at the upstream end of the aerosol-generating substrate. The upstream element may be at the upstream end of the aerosol-generating article.

The outer wrapper may circumscribe the hollow tubular substrate element and at least part of the upstream element. The outer wrapper may circumscribe the entire length of the upstream element.

The upstream element may be an upstream plug element. For example, the upstream element may be a plug of cellulose acetate tow.

Preferably, an external diameter of the upstream element is about the same as an external diameter of the aerosol-generating substrate. Preferably, an external diameter of the upstream element is about the same as an external diameter of the aerosol-generating article.

The external diameter of the upstream element may be at least about 5 millimetres, or at least about 5.5 millimetres, or at least about 6 millimetres.

The external diameter of the upstream element may be up to about 10 millimetres, or up to about 9 millimetres, or up to about 8 millimetres.

For example, the external diameter of the upstream element may be between about 5 millimetres and about 10 millimetres, or between about 5.5 millimetres and about 9 millimetres, or between about 6 millimetres and about 8 millimetres.

An external diameter of the upstream element may be greater than an external diameter of at least a part of the hollow tubular substrate element. This may be such that the empty space is defined between the external surface of the hollow tubular substrate element and the outer wrapper circumscribing the hollow tubular substrate element and at least part of the upstream element. Preferably, an external diameter of at least a part of the hollow tubular substrate element is at least about 0.1 millimetres less than an external diameter of the upstream element, or at least about 0.2 millimetres less than an external diameter of the upstream element.

Preferably, an external diameter of at least a part of the hollow tubular substrate element is up to about 6 millimetres less than an external diameter of the upstream element, up to about 4.5 millimetres less than an external diameter of the upstream element, or up to 3 millimetres less than an external diameter of the upstream element.

For example, an external diameter of at least a part of the hollow tubular substrate element may be between about 0.1 millimetres and about 6 millimetres less than an external diameter of the upstream element, or between about 0.2 millimetres and about 3 millimetres less than an external diameter of the upstream element.

The external diameter of at least a part of the hollow tubular substrate element may be about 0.2 millimetres less than an external diameter of the upstream element.

The difference in the external diameter of the hollow tubular substrate element and the external diameter of the upstream element may define the size of the empty space. In particular, the difference in the external diameter of the hollow tubular substrate element and the external diameter of the upstream element may be equal to twice the separation across the empty space between the external surface of the hollow tubular substrate element and the outer wrapper. As such, the difference in the external diameter of the hollow tubular substrate element and the external diameter of the upstream element may be selected based on a desired size of the empty space.

The upstream element may have a length of at least about 2 millimetres, or at least about 3 millimetres, or at least about 5 millimetres.

The upstream element may have a length of up to about 15 millimetres, or up to about 12 millimetres, or up to about 10 millimetres.

For example, the upstream element may have a length of between about 2 millimetres and about 15 millimetres, or between about 3 millimetres and about 12 millimetres, or between about 5 millimetres and about 10 millimetres.

The upstream element may have a length of about 5 millimetres.

The length of the upstream element may be selected based on the position of an external heating element in a corresponding aerosol-generating device to align the hollow tubular substrate element with the external heating element when the aerosol-generating article is fully inserted into the aerosol-generating device.

The aerosol-generating substrate may comprise a downstream element adjacent to the downstream end of the hollow tubular substrate element. The downstream element may abut the downstream end of the hollow tubular substrate element. The downstream element may be affixed to the hollow tubular substrate element. The downstream element may be at the downstream end of the aerosol-generating substrate. The downstream element may abut the downstream section of the aerosol-generating article.

The outer wrapper may circumscribe the hollow tubular substrate element and at least part of the downstream element. The outer wrapper may circumscribe the entire length of the downstream element.

The properties of the upstream element discussed above may be equally applied to the downstream element. For example, at least one of the shape, size and material of the upstream element discussed above may be applied to the downstream element. The downstream element may be identical to the upstream element.

The downstream element may be a downstream plug element. For example, the downstream element may be a plug of cellulose acetate tow.

Preferably, an external diameter of the downstream element is about the same as an external diameter of the aerosol-generating substrate. Preferably, an external diameter of the downstream element is about the same as an external diameter of the aerosol-generating article. Preferably, an external diameter of the downstream element is about the same as an external diameter of the upstream element. More preferably, an external diameter of the downstream element is about the same as an external diameter of the upstream element and an external diameter of the aerosol-generating article. This may help to ensure that the external diameter of the aerosol-generating article is substantially constant along the length of the aerosol-generating article.

The external diameter of the downstream element may be at least about 5 millimetres, or at least about 5.5 millimetres, or at least about 6 millimetres.

The external diameter of the downstream element may be up to about 10 millimetres, or up to about 9 millimetres, or up to about 8 millimetres.

For example, the external diameter of the downstream element may be between about 5 millimetres and about 10 millimetres, or between about 5.5 millimetres and about 9 millimetres, or between about 6 millimetres and about 8 millimetres.

An external diameter of the downstream element may be greater than an external diameter of at least a part of the hollow tubular substrate element. This may be such that the empty space is defined between the external surface of the hollow tubular substrate element and the outer wrapper circumscribing the hollow tubular substrate element and at least part of the downstream element.

Preferably, an external diameter of at least a part of the hollow tubular substrate element is at least about 0.1 millimetres less than an external diameter of the downstream element, or at least about 0.2 millimetres less than an external diameter of the downstream element. Preferably, an external diameter of at least a part of the hollow tubular substrate element is up to about 6 millimetres less than an external diameter of the downstream element, up to about 4.5 millimetres less than an external diameter of the downstream element, or up to 3 millimetres less than an external diameter of the downstream element.

For example, an external diameter of at least a part of the hollow tubular substrate element may be between about 0.1 millimetres and about 6 millimetres less than an external diameter of the downstream element, or between about 0.2 millimetres and about 3 millimetres less than an external diameter of the downstream element.

The external diameter of at least a part of the hollow tubular substrate element may be about 0.2 millimetres less than an external diameter of the downstream element.

The difference in the external diameter of the hollow tubular substrate element and the external diameter of the downstream element may define the size of the empty space. In particular, the difference in the external diameter of the hollow tubular substrate element and the external diameter of the downstream element may be equal to twice the separation across the empty space between the external surface of the hollow tubular substrate element and the outer wrapper. As such, the difference in the external diameter of the hollow tubular substrate element and the external diameter of the downstream element may be selected based on a desired size of the empty space.

The downstream element may have a length of at least about 2 millimetres, or at least about 3 millimetres, or at least about 5 millimetres.

The downstream element may have a length of up to about 15 millimetres, or up to about 12 millimetres, or up to about 10 millimetres.

For example, the downstream element may have a length of between about 2 millimetres and about 15 millimetres, or between about 3 millimetres and about 12 millimetres, or between about 5 millimetres and about 10 millimetres.

The downstream element may have a length of about 5 millimetres.

The central longitudinal axis of the hollow tubular substrate element is preferably aligned with the central longitudinal axis of other elements of the aerosol-generating article, for example other components of the aerosol-generating substrate and components of the downstream section. For example, the central longitudinal axis of the hollow tubular substrate element is preferably aligned with the central longitudinal axis of both the upstream element and the downstream element. The central longitudinal axis of the hollow tubular substrate element is preferably aligned with the central longitudinal axis of the aerosol-generating article.

Where the hollow tubular substrate element is in an abutting arrangement with both the upstream element and the downstream element, the hollow tubular substrate element may be supported between the upstream element and the downstream element. The outer wrapper may be wrapped tightly around to one or both of the upstream element and the downstream element to retain the upstream element, the hollow tubular substrate element and the downstream element in position.

The outer wrapper may be unattached to the hollow tubular substrate element.

The outer wrapper may be affixed to one or both of the upstream element and the downstream element.

The upstream element, the hollow tubular substrate element and the downstream element may be affixed to each other. This may also help to retain the upstream element, the hollow tubular substrate element and the downstream element in position.

Within the empty space, the external surface of the hollow tubular substrate element and the outer wrapper may be separated by at least about 0.05 millimetres in a radial direction, or by at least about 0.1 millimetres in a radial direction.

Within the empty space, the external surface of the hollow tubular substrate element and the outer wrapper may be separated by up to about 3 millimetres in a radial direction, up to about 2.25 millimetres in a radial direction, or up to about 1 .5 millimetres in a radial direction.

For example, within the empty space, the external surface of the hollow tubular substrate element and the outer wrapper may be separated by between about 0.05 millimetres and about 3 millimetres in a radial direction, or between about 0.1 millimetres and about 1 .5 millimetres in a radial direction.

Within the empty space, the external surface of the hollow tubular substrate element and the outer wrapper may be separated by about 0.1 millimetres in a radial direction.

As described above, the outer wrapper may circumscribe the hollow tubular substrate element and at least a part of both the upstream element and the downstream element to define the empty space between the outer wrapper and the hollow tubular substrate element. In other words, the empty space may be defined by the external surface of the hollow tubular substrate element, the portion of the outer wrapper circumscribing the hollow tubular substrate element, the downstream end face of the upstream element, and the upstream end face of the downstream element. As such, the provision of both the upstream element and the downstream element may provide an effective way of creating the empty space without the need for additional elements.

Preferably, the outer wrapper has sufficient structural rigidity so that the empty space can be retained between the outer wrapper and the hollow tubular substrate element. For example, the outer wrapper may have sufficient structural rigidity so that the outer wrapper does not collapse at the hollow tubular substrate element during handling or storage of the aerosolgenerating article. However, some flexibility in the outer wrapper may be desirable so that the outer wrapper may be drawn towards the external surface of the hollow tubular substrate element when the consumer draws air through the aerosol-generating article. This may help to force aerosol in the empty space into the longitudinal cavity. The basis weight of the outer wrapper may be selected such that the outer wrapper has the desired balance between structural rigidity and flexibility.

The outer wrapper may have a basis weight of at least about 15 grams per square metre, or at least about 20 grams per square metre, or at least about 25 grams per square metre.

The outer wrapper may have a basis weight of up to about 100 grams per square metre, or up to about 90 grams per square metre, or up to about 80 grams per square metre, or up to 50 grams per square metre.

In some embodiments, the outer wrapper is preferably stiff, for example, the outer wrapper may have a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 1 10 gsm.

The outer wrapper may comprise a plurality of perforations overlying the hollow tubular substrate element. This may enable air to be drawn into the empty space, which may increase a level of turbulence in the empty space.

Any wrapper circumscribing the hollow tubular substrate element may comprise a plurality of perforations substantially aligned with a plurality of perforations of the outer wrapper.

Preferably, the plurality of perforations of the outer wrapper is arranged in one or more circumferential rows. That is, the outer wrapper may comprise one or more circumferential rows of perforations.

The outer wrapper may comprise at least two circumferential rows of perforations.

The outer wrapper may comprise up to five circumferential rows of perforations.

The circumferential rows of perforations may follow various patterns. For example, the circumferential rows of perforations may be arranged circularly or helically around the hollow tubular substrate element.

The properties of the plurality of perforations of the hollow tubular substrate element discussed above may be equally applied to the plurality of perforations of the outer wrapper. For example, the outer wrapper may have the same number of rows of perforations and perforations per row as the hollow tubular substrate element.

The plurality of perforations of the outer wrapper may comprise at least one perforation having a maximum dimension of at least 200 micrometres, or at least 300 micrometres, or at least about 400 micrometres, or at least about 500 micrometres.

Where the perforation of the outer wrapper is substantially circular, the maximum dimension of the perforation is the diameter of the perforation. The plurality of perforations of the outer wrapper may comprise at least one perforation having a maximum dimension of up to about 1 millimetre, or up to about 900 micrometres, or up to about 800 micrometres, or up to about 700 micrometres. Each of the plurality of perforations of the outer wrapper may have a maximum dimension of at least 200 micrometres, at least 300 micrometres, at least 400 micrometres, or at least 500 micrometres.

Each of the plurality of perforations of the outer wrapper may have a maximum dimension of up to about 1 millimetre, or up to about 900 micrometres, or up to about 800 micrometres, or up to about 700 micrometres.

The plurality of perforations of the outer wrapper may comprise at least one perforation having an opening area of at least about 0.01 millimetres squared, or at least about 0.03 millimetres square, or at least about 0.05 millimetres squared, or at least about 0.07 millimetres squared.

The plurality of perforations of the outer wrapper may comprise at least one perforation having an opening area of no more than 1 millimetre squared, or no more than 0.8 millimetres squared, or no more than 0.5 millimetres squared, or no more than 0.3 millimetres squared, or no more than 0.1 millimetres squared.

Each of the plurality of perforations of the outer wrapper may have an opening area of at least about 0.01 millimetres squared, or at least about 0.03 millimetres square, or at least about 0.05 millimetres squared, or at least about 0.07 millimetres squared.

Each of the plurality of perforations of the outer wrapper may have an opening area of no more than 1 millimetre squared, or no more than 0.8 millimetres squared, or no more than 0.5 millimetres squared, or no more than 0.3 millimetres squared, or no more than 0.1 millimetres squared.

The plurality of perforations of the outer wrapper may have a total opening area of at least about 0.05 millimetres squared, or at least about 0.2 millimetres squared, or at least about 0.35 millimetres squared, or at least about 0.5 millimetres squared.

The plurality of perforations of the outer wrapper may have a total opening area of up to about 30 millimetres squared, or up to about 25 millimetres squared, or up to about 15 millimetres squared, or up to about 10 millimetres squared, or up to about 5 millimetres squared.

The plurality of perforations of the outer wrapper may overlie the empty space.

Preferably, the plurality of perforations of the outer wrapper overlie the plurality of perforations of the hollow tubular substrate element. That is, preferably, the plurality of perforations of the outer wrapper are substantially aligned with the plurality of perforations of the hollow tubular substrate element. This may be so that the aerosol-generating article has a desired RTD. This may also simplify manufacturing of the aerosol-generating article since the plurality of perforations of the outer wrapper and the plurality of perforations of the hollow tubular substrate element may be formed simultaneously after circumscribing the hollow tubular substrate element with the outer wrapper. The plurality of perforations may be formed using suitable known methods such as online during manufacturing of the aerosol-generating article.

Preferably, the outer wrapper is non-porous so that airflow into the aerosol-generating article may be controlled. For example, a non-porous outer wrapper may prevent air from entering the upstream element and the downstream element through the outer wrapper.

The rod of aerosol-generating substrate may comprise one or more susceptor elements located in contact with the hollow tubular substrate element, for inductive heating of the homogenised tobacco material during use.

As used herein, the term 'susceptor element' refers to an element comprising a material that is capable of converting electromagnetic energy into heat. When a susceptor element is located in an alternating electromagnetic field, the susceptor is heated. Heating of the susceptor element 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.

Preferably, the rod of aerosol-generating substrate comprises one or more susceptor elements on a surface of the hollow tubular substrate element. The hollow tubular substrate element may comprise one or more susceptor elements on the internal surface of the hollow tubular substrate element. Alternatively or in addition, the rod of aerosol-generating substrate may comprise one or more susceptor elements on the external surface of the hollow tubular substrate element.

The one or more susceptor elements may be located away from the plurality of perforations of the hollow tubular substrate element so that air and aerosol may flow from the empty space to the hollow cavity through the plurality of perforations of the hollow tubular substrate element.

The one or more susceptor elements may comprise a plurality of perforations. Preferably, the plurality of perforations of the one or more susceptor elements are arranged to substantially coincide with the plurality of perforations of the hollow tubular substrate element. That is, preferably the plurality of perforations of the one or more susceptor elements are substantially aligned with the plurality of perforations of the hollow tubular substrate element. This may be so that air and aerosol may flow from the empty space to the hollow cavity through the plurality of perforations of the hollow tubular substrate element and through the plurality of perforations of the one or more susceptor elements. For example, the one or more susceptor elements may be in the form of one or more perforated sheets.

The one or more susceptor elements may be embedded within the wall of the hollow tubular substrate element.

The susceptor element may comprise any suitable material. The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to release volatile compounds from the aerosol-generating substrate. Suitable materials for the elongate susceptor element include graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminium, nickel, nickel containing compounds, titanium, and composites of metallic materials. Some susceptor elements comprise a metal or carbon. Advantageously the susceptor element may comprise or consist of a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy, such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. A suitable susceptor element may be, or comprise, aluminium. The susceptor element preferably comprises more than about 5 percent, preferably more than about 20 percent, more preferably more than about 50 percent or more than about 90 percent of ferromagnetic or paramagnetic materials. Some elongate susceptor elements may be heated to a temperature in excess of about 250 degrees Celsius.

The aerosol-generating substrate may have a length of at least about 10 millimetres, at least about 12 millimetres, or at least about 15 millimetres.

The aerosol-generating substrate may have a length of up to about 40 millimetres, up to about 37 millimetres, or up to about 35 millimetres.

For example, the aerosol-generating substrate may have a length of between about 10 millimetres and about 40 millimetres, or between about 12 millimetres and about 37 millimetres, or between about 15 millimetres and about 35 millimetres.

The aerosol-generating substrate may have a length greater than the length of the hollow tubular substrate element.

As defined above, in the aerosol-generating articles of the present invention, the aerosolgenerating substrate comprising the hollow tubular substrate element is combined with a downstream section, located downstream of the aerosol-generating substrate. The downstream section is preferably located immediately downstream of the aerosol-generating substrate. The downstream section of the aerosol-generating article preferably extends between the aerosolgenerating substrate and the downstream end of the aerosol-generating article. The downstream section may comprise one or more elements, each of which will be described in more detail within the present disclosure.

Preferably, the downstream section comprises at least one hollow tubular element. The hollow tubular element may be adjacent to the downstream end of the rod of aerosol-generating substrate. The hollow tubular element may be provided immediately downstream of the aerosolgenerating substrate. In other words, the hollow tubular element may abut a downstream end of the aerosol-generating substrate. This arrangement may optimise flow of the aerosol from the longitudinal airflow channel of the hollow tubular substrate element into the downstream section and through the aerosol-generating article.

Preferably, the downstream section of the aerosol-generating article comprises a single hollow tubular element. In other words, the downstream section of the aerosol-generating article may comprise only one hollow tubular element. The hollow tubular element of the downstream section may also be referred to as a hollow tubular downstream element.

In the context of the present invention, the hollow tubular element of the downstream section provides an unrestricted flow channel through the airflow passage. This means that the hollow tubular element provides a negligible level of resistance to draw (RTD), as defined above. The airflow passage should therefore be free from any components that would obstruct the flow of air in a longitudinal direction. Preferably, the airflow passage is substantially empty.

The hollow tubular element of the downstream section provides an empty cavity downstream of the aerosol-generating substrate, which may enhance cooling and nucleation of aerosol particles generated by the aerosol-generating substrate. The hollow tubular element of the downstream section therefore may function as an aerosol-cooling element.

The length of the hollow tubular element may be at least about 12 mm. The length of the hollow tubular element may be at least about 15 mm. The length of the hollow tubular element may be at least about 20 mm.

The length of the hollow tubular element of the downstream section may be less than or equal to about 50 mm. The length of the hollow tubular element may be less than or equal to about 45 mm. The length of the hollow tubular element may be less than or equal to about 40 mm.

For example, the length of the hollow tubular element of the downstream section may be between about 12 mm and 50 mm. The length of the hollow tubular element may be between about 15 mm and 45 mm. The length of the hollow tubular element may be between about 20 mm and 40 mm. The length of the hollow tubular element may be about 30 mm.

A relatively long hollow tubular element provides and defines a relatively long internal cavity within the downstream section of the aerosol-generating article. Providing a relatively long cavity may maximise the nucleation benefits described above, thereby improving aerosol formation and cooling.

The ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be less than or equal to about 1.25. Preferably, a ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be less than or equal to about 1 . More preferably, a ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be less than or equal to about 0.75.

The ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be at least about 0.2. Preferably, a ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be at least about 0.25. More preferably, a ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be at least about 0.3.

For example, the ratio between the length of the hollow tubular substrate element and the length of the hollow tubular element of the downstream section may be between about 0.2 and about 1 .25, or between about 0.25 and about 1 , or between about 0.3 and about 0.75.

The ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be less than or equal to about 1 . Preferably, the ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be less than or equal to about 0.90. More preferably, the ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be less than or equal to about 0.85.

The ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be at least about 0.35. Preferably, the ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be at least about 0.45. More preferably, the ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be at least about 0.50.

For example, the ratio between the length of the hollow tubular element of the downstream section and the total length of the downstream section may be between about 0.35 and about 1 , or between about 0.45 and about 0.9, or between about 0.5 and about 0.85.

The ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be less than or equal to about 0.80. Preferably, the ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be less than or equal to about 0.70. More preferably, the ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be less than or equal to about 0.60.

The ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be at least about 0.25. Preferably, the ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be at least about 0.30. More preferably, the ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be at least about 0.40.

For example, the ratio between the length of the hollow tubular element of the downstream section and the overall length of the aerosol-generating article may be between about 0.25 and about 0.8, or between about 0.3 and about 0.7, or between about 0.4 and about 0.6. The wall thickness of the hollow tubular element of the downstream section may be at least about 100 micrometres. The wall thickness of the hollow tubular element of the downstream section may be at least about 150 micrometres. The wall thickness of the hollow tubular element of the downstream section may be at least about 200 micrometres, preferably at least about 250 micrometres and even more preferably at least about 500 micrometres (or 0.5 mm).

The wall thickness of the hollow tubular element of the downstream section may be less than or equal to about 2 millimetres, preferably less than or equal to about 1.5 millimetres and even more preferably less than or equal to about 1.25 mm. The wall thickness of the hollow tubular element of the downstream section may be less than or equal to about 1 millimetre. The wall thickness of the hollow tubular element of the downstream section may be less than or equal to about 500 micrometres.

The wall thickness of the hollow tubular element of the downstream section may between about 100 micrometres and about 2 millimetres, preferably between about 150 micrometres and about 1.5 millimetres, even more preferably between about 200 micrometres and about 1.25 millimetres.

Keeping the wall thickness of the hollow tubular segment of the downstream section relatively low ensures that the overall internal volume of the hollow tubular element - which is made available for the aerosol to begin the nucleation process as soon as the aerosol components leave the aerosol-generating substrate - and the cross-sectional surface area of the cavity of the hollow tubular element are effectively maximised, whilst at the same time ensuring that the hollow tubular element has the necessary structural strength to prevent a collapse of the aerosol-generating article as well as to provide some support to the rod of aerosol-generating substrate, and that the RTD of the hollow tubular element is minimised. Greater values of cross- sectional surface area of the cavity of the hollow tubular element are understood to be associated with a reduced speed of the aerosol stream travelling along the aerosol-generating article, which is also expected to favour aerosol nucleation. Further, it would appear that by utilising a hollow tubular element having a relatively low thickness, it is possible to substantially prevent diffusion of ventilation air prior to its contacting and mixing with the stream of aerosol, which is also understood to further favour nucleation phenomena. In practice, by providing a more controllably localised cooling of the stream of volatilised species, it may be possible to enhance the effect of cooling on the formation of new aerosol particles.

The hollow tubular element of the downstream section preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating substrate and to the external diameter of the aerosol-generating article. The hollow tubular element of the downstream section preferably has an external diameter that is greater than the external diameter of the hollow tubular substrate element of the aerosol-generating substrate. The hollow tubular element may have an external diameter of between 5 millimetres and 10 millimetres, for example of between 5.5 millimetres and 9 millimetres or of between 6 millimetres and 8 millimetres.

The hollow tubular element of the downstream section may have a constant internal diameter along a length of the hollow tubular element. However, the internal diameter of the hollow tubular element may vary along the length of the hollow tubular element.

The hollow tubular element of the downstream section may have an internal diameter of at least about 2 millimetres. For example, the hollow tubular element may have an internal diameter of at least about 2.5 millimetres, at least about 3 millimetres, or at least about 3.5 millimetres. The provision of a hollow tubular element having an internal diameter as set out above may advantageously provide sufficient rigidity and strength to the hollow tubular element.

The hollow tubular element of the downstream section may have an internal diameter of no more than about 10 millimetres. For example, the hollow tubular element may have an internal diameter of no more than about 9 millimetres, no more than about 8 millimetres, or no more than about 7.5 millimetres. The provision of a hollow tubular element having an internal diameter as set out above may advantageously reduce the resistance to draw of the hollow tubular segment.

For example, the hollow tubular element of the downstream section may have an internal diameter of between about 2 millimetres and about 10 millimetres, between about 2.5 millimetres and about 9 millimetres, between about 3 millimetres and about 8 millimetres, or between about 3.5 millimetres and about 7.5 millimetres.

The ratio of the internal diameter of the hollow tubular substrate element to the internal diameter of the hollow tubular element of the downstream section is preferably between about 0.8 and about 1 .2, more preferably between about 0.9 and about 1.1 , most preferably about 1 .

Particularly preferably, the internal diameter of the hollow tubular substrate element is substantially equal to the internal diameter of the hollow tubular element of the downstream section.

The central longitudinal axis of the hollow tubular substrate element of the aerosolgenerating substrate may preferably be aligned with the central longitudinal axis of the hollow tubular element of the downstream section. For example, where the internal diameter of the hollow tubular substrate element is substantially equal to the internal diameter of the hollow tubular element of the downstream section, the central longitudinal axis of the hollow tubular substrate element may be aligned with the central longitudinal axis of the hollow tubular substrate element of the downstream section so that the cavity of the hollow tubular substrate element and the cavity of the hollow tubular element of the downstream section may be substantially aligned.

The hollow tubular element of the downstream section may comprise a paper-based material. The hollow tubular element may comprise at least one layer of paper. The paper may be very rigid paper. The paper may be crimped paper, such as crimped heat resistant paper or crimped parchment paper.

Preferably, the hollow tubular element may comprise cardboard. The hollow tubular element may be a cardboard tube. The hollow tubular element may be formed from cardboard. Advantageously, cardboard is a cost-effective material that provides a balance between being deformable in order to provide ease of insertion of the aerosol-generating article into an aerosolgenerating device and being sufficiently stiff to provide suitable engagement of the article with the interior of the device. A cardboard tube may therefore provide suitable resistance to deformation or compression during use.

The hollow tubular element of the downstream section may be a paper tube. The hollow tubular element may be a tube formed from spirally wound paper. The hollow tubular element may be formed from a plurality of layers of the paper. The paper may have a basis weight of at least about 50 grams per square meter, at least about 60 grams per square meter, at least about 70 grams per square meter, or at least about 90 grams per square meter.

The hollow tubular element of the downstream section may comprise a polymeric material. For example, the hollow tubular element may comprise a polymeric film. The polymeric film may comprise a cellulosic film. The hollow tubular segment may comprise low density polyethylene (LDPE) or polyhydroxyalkanoate (PHA) fibres. The hollow tube may comprise cellulose acetate tow.

Where the hollow tubular element comprises cellulose acetate tow, the cellulose acetate tow may have a denier per filament of between about 2 and about 4 and a total denier of between about 25 and about 40.

The hollow tubular element may be at the upstream end of the downstream section. The hollow tubular element may abut the downstream end of the aerosol-generating substrate. The hollow tubular element may abut the downstream end of the hollow tubular substrate element.

The outer wrapper of the aerosol-generating substrate may also circumscribe at a least part of the downstream section of the aerosol-generating article. For example, the outer wrapper of the aerosol-generating substrate may also circumscribe at least a part of a hollow tubular element of the downstream section.

The aerosol-generating article according to the present invention may comprise a ventilation zone at a location along the downstream section. In more detail, where the downstream section comprises a hollow tubular element, the ventilation zone may be provided at a location along the hollow tubular element.

As such, a ventilated cavity is provided downstream of the rod of aerosol-generating substrate. This may provide particularly efficient cooling of the aerosol and promote enhanced nucleation of aerosol particles. The ventilation zone may typically comprise a plurality of perforations through the peripheral wall of the hollow tubular element. The plurality of perforations of the ventilation zone may also be through any wrapper circumscribing the hollow tubular element. Preferably, the ventilation zone comprises at least one circumferential row of perforations. The ventilation zone may comprise two circumferential rows of perforations. For example, the perforations may be formed online during manufacturing of the aerosol-generating article. Preferably, each circumferential row of perforations comprises from 8 to 30 perforations.

The downstream section may further comprise a mouthpiece element. The mouthpiece element may be located at the downstream end of the aerosol-generating article. The mouthpiece element is preferably located downstream of the hollow tubular element of the downstream section, which is described above. The mouthpiece element may extend between the hollow tubular element of the downstream section and the downstream end of the aerosol-generating article.

The provision of a mouthpiece element at the downstream end of the aerosol-generating articles according to the present invention may provide an appealing appearance and mouthfeel to the consumer.

The mouthpiece element may be a mouthpiece filter element. The mouthpiece element may comprise at least one mouthpiece filter segment formed of a fibrous filtration material. Parameters or characteristics described in relation to the mouthpiece element as a whole may equally be applied to a mouthpiece filter segment of the mouthpiece element.

The fibrous filtration material may be for filtering the aerosol that is generated from the aerosol-generating substrate. Suitable fibrous filtration materials would be known to the skilled person. Particularly preferably, the at least one mouthpiece filter segment comprises a cellulose acetate filter segment formed of cellulose acetate tow.

The mouthpiece element may consist of a single mouthpiece filter segment. The mouthpiece element may include two or more mouthpiece filter segments axially aligned in an abutting end to end relationship with each other.

The downstream section may comprise a mouth end cavity at the downstream end, downstream of the mouthpiece element as described above. The mouth end cavity may be defined by a further hollow tubular element provided at the downstream end of the mouthpiece element. The mouth end cavity may be defined by an outer wrapper of the aerosol-generating article, wherein the outer wrapper extends in a downstream direction from (or past) the mouthpiece element. For example, the mouth end cavity may be defined by a tipping wrapper extending downstream past the mouthpiece element.

The mouthpiece element may optionally comprise a flavourant, which may be provided in any suitable form. 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. Preferably, the mouthpiece element, or mouthpiece filter segment thereof, has a low particulate filtration efficiency.

Preferably, the mouthpiece element is circumscribed by a plug wrap. Preferably, the mouthpiece element is unventilated such that air does not enter the aerosol-generating article along the mouthpiece element.

The mouthpiece element preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article. The diameter of a mouthpiece element (or mouthpiece filter segment) may be substantially the same as the external diameter of the hollow tubular element. As mentioned in the present disclosure, the external diameter of the hollow tubular element may be about 7.2 mm, plus or minus 10 percent.

The diameter of the mouthpiece element may be between about 5 mm and about 10 mm. The diameter of the mouthpiece element may be between about 5.5 mm and about 9 mm. The diameter of the mouthpiece element may be between about 6 mm and about 8 mm. The diameter of the mouthpiece element may be about 7.2 mm, plus or minus 10 percent. The diameter of the mouthpiece element may be about 7.25 mm, plus or minus 10 percent.

Unless otherwise specified, the resistance to draw (RTD) of a component or the aerosolgenerating article is measured in accordance with ISO 6565-2015. The RTD refers to the pressure required to force air through the full length of a component. The terms “pressure drop” or “draw resistance” of a component or article may also refer to the “resistance to draw”.

The resistance to draw (RTD) of the downstream section may be at least about 0 mm H₂O. The RTD of the downstream section may be at least about 3 mm H₂O. The RTD of the downstream section may be at least about 6 mm H₂O.

The RTD of the downstream section may be no greater than about 12 mm H₂O. The RTD of the downstream section may be no greater than about 1 1 mm H₂O. The RTD of the downstream section may be no greater than about 10 mm H₂O.

The resistance to draw of the downstream section may be greater than or equal to about 0 mm H₂O and less than about 12 mm H₂O. Preferably, the resistance to draw of the downstream section may be greater than or equal to about 3 mm H₂O and less than about 12 mm H₂O. The resistance to draw of the downstream section may be greater than or equal to about 0 mm H₂O and less than about 11 mm H₂O. Even more preferably, the resistance to draw of the downstream section may be greater than or equal to about 3 mm H₂O and less than about 11 mm H₂O. Even more preferably, the resistance to draw of the downstream section may be greater than or equal to about 6 mm H₂O and less than about 10 mm H₂O. Preferably, the resistance to draw of the downstream section may be about 8 mm H₂O.

The resistance to draw (RTD) characteristics of the downstream section may be wholly or mostly attributed to the RTD characteristics of the mouthpiece element of the downstream section. In other words, the RTD of the mouthpiece element of the downstream section may wholly define the RTD of the downstream section.

The resistance to draw (RTD) of the mouthpiece element may be at least about 0 mm H₂O. The RTD of the mouthpiece element may be at least about 3 mm H₂O. The RTD of the mouthpiece element may be at least about 6 mm H₂O.

The RTD of the mouthpiece element may be no greater than about 12 mm H₂O. The RTD of the mouthpiece element may be no greater than about 1 1 mm H₂O. The RTD of the mouthpiece element may be no greater than about 10 mm H₂O.

The resistance to draw of the mouthpiece element may be greater than or equal to about 0 mm H₂O and less than about 12 mm H₂O. Preferably, the resistance to draw of the mouthpiece element may be greater than or equal to about 3 mm H₂O and less than about 12 mm H₂O. The resistance to draw of the mouthpiece element may be greater than or equal to about 0 mm H₂O and less than about 11 mm H₂O. Even more preferably, the resistance to draw of the mouthpiece element may be greater than or equal to about 3 mm H₂O and less than about 11 mm H₂O. Even more preferably, the resistance to draw of the mouthpiece element may be greater than or equal to about 6 mm H₂O and less than about 10 mm H₂O. Preferably, the resistance to draw of the mouthpiece element may be about 8 mm H₂O.

As mentioned above, the mouthpiece element, or mouthpiece filter segment, may be formed of a fibrous material. The mouthpiece element may be formed of a porous material. The mouthpiece element may be formed of a biodegradable material. The mouthpiece element may be formed of a cellulose material, such as cellulose acetate. For example, a mouthpiece element may be formed from a bundle of cellulose acetate fibres having a denier per filament between about 10 and about 15. For example, a mouthpiece element formed from relatively low density cellulose acetate tow, such as cellulose acetate tow comprising fibres of about 12 denier per filament.

The mouthpiece element may be formed of a polylactic acid based material. The mouthpiece element may be formed of a bioplastic material, preferably a starch-based bioplastic material. The mouthpiece element may be made by injection moulding or by extrusion. Bioplastic-based materials are advantageous because they are able to provide mouthpiece element structures which are simple and cheap to manufacture with a particular and complex cross-sectional profile, which may comprise a plurality of relatively large air flow channels extending through the mouthpiece element material, that provides suitable RTD characteristics.

The mouthpiece element may be formed from a sheet of suitable material that has been crimped, pleated, gathered, woven or folded into an element that defines a plurality of longitudinally extending channels. Such sheet of suitable material may be formed of paper, cardboard, a polymer, such as polylactic acid, or any other cellulose-based, paper-based material or bioplastic-based material. A cross-sectional profile of such a mouthpiece element may show the channels as being randomly oriented.

The mouthpiece element may be formed in any other suitable manner. For example, the mouthpiece element may be formed from a bundle of longitudinally extending tubes. The longitudinally extending tubes may be formed from polylactic acid. The mouthpiece element may be formed by extrusion, moulding, lamination, injection, or shredding of a suitable material. Thus, it is preferred that there is a low-pressure drop (or RTD) from an upstream end of the mouthpiece element to a downstream end of the mouthpiece element.

The length of the mouthpiece element may be at least about 1 .5 mm. The length of the mouthpiece element may be at least about 2 mm. The length of the mouthpiece element may equal to or less than about 7 mm. The length of the mouthpiece element may be equal to or less than about 4 mm. For example, the length of the mouthpiece element may be between about 1 .5 mm and about 7 mm. The length of the mouthpiece element may be between about 2 millimetres and about 4 millimetres.

The ratio between the length of the mouthpiece element and the length of the downstream section may be less than or equal to about 0.35. Preferably, the ratio between the length of the mouthpiece element and the length of the downstream section may be less than or equal to about 0.30. More preferably, the ratio between a length of the mouthpiece element and the length of the downstream section may be less than or equal to about 0.25.

The ratio between the length of the mouthpiece element and the length of the downstream section may be at least about 0.03. Preferably, the ratio between a length of the mouthpiece element and the length of the downstream section may be at least about 0.05. More preferably, the ratio between the length of the mouthpiece element and the length of the downstream section may be at least about 0.1 .

For example, the ratio between the length of the mouthpiece element and the length of the downstream section is from about 0.03 to about 0.35, preferably from about 0.05 to about 0.30, more preferably from about 0.1 to about 0.25.

The ratio between the length of the mouthpiece element and the overall length of the aerosol-generating article may be less than or equal to about 0.20. Preferably, the ratio between the length of the mouthpiece element and the overall length of the aerosol-generating article may be less than or equal to about 0.15. More preferably, the ratio between a length of the mouthpiece element and the overall length of the aerosol-generating article may be less than or equal to about 0.1.

The ratio between the length of the mouthpiece element and the overall length of the aerosol-generating article may be at least about 0.01 . Preferably, the ratio between the length of the mouthpiece element and the overall length of the aerosol-generating article may be at least about 0.02. More preferably, the ratio between the length of the mouthpiece element and the overall length of the aerosol-generating article may be at least about 0.05.

For example, the ratio between the length of the mouthpiece element and the overall length of the aerosol-generating article is from about 0.01 to about 0.2, preferably from about 0.02 to about 0.15, more preferably from about 0.05 to about 0.1 .

Where the downstream section comprises a hollow tubular element and a mouthpiece element, a ratio of the length of the hollow tubular element to the length of the mouthpiece element may be at least about 1.5. In other words, the length of the hollow tubular element may be at least about 150% of the length of the mouthpiece element. The ratio of the length of the hollow tubular element to the length of the mouthpiece element may be at least about 5. The ratio of the length of the hollow tubular element to the length of the mouthpiece element may be at least about 7.5.

The ratio of the length of the hollow tubular element to the length of the mouthpiece element may be equal to or less than about 20. The ratio of the length of the hollow tubular element to the length of the mouthpiece element may be equal to or less than about 15. The ratio of the length of the hollow tubular element to the length of the mouthpiece element may be equal to or less than about 12.5.

For example, the ratio of the length of the hollow tubular element to the length of the mouthpiece element may be between about 1 .5 and about 20, or between about 5 and about 15, or between about 7.5 and about 10.

The overall length of the downstream section is preferably at least about 15 millimetres, more preferably at least about 20 millimetres, more preferably at least about 25 millimetres.

The overall length of the downstream section is preferably less than about 50 millimetres, more preferably less than about 45 millimetres, more preferably less than about 40 millimetres.

For example, the downstream section may have an overall length of between about 20 millimetres and about 50 millimetres, more preferably between about 25 millimetres and about 45 millimetres, more preferably between about 30 millimetres and about 40 millimetres.

The ratio between the total length of the downstream section and an overall length of the aerosol-generating article may be less than or equal to about 0.80. Preferably, the ratio between the length of the downstream section and an overall length of the aerosol-generating article may be less than or equal to about 0.75. More preferably, the ratio between the length of the downstream section and the overall length of the aerosol-generating article may be less than or equal to about 0.70. Even more preferably, the ratio between the length of the downstream section and the overall length of the aerosol-generating article may be less than or equal to about 0.65.

The ratio between the length of the downstream section and the overall length of the aerosol-generating article may be at least about 0.30. Preferably, the ratio between the length of the downstream section and the overall length of the aerosol-generating article may be at least about 0.40. More preferably, the ratio between a length of the downstream section and the overall length of the aerosol-generating article may be at least about 0.50. Even more preferably, the ratio between a length of the downstream section and the overall length of the aerosol-generating article may be at least about 0.60.

Preferably, an overall length of an aerosol-generating article in accordance with the invention is at least about 35 millimetres. More preferably, an overall length of an aerosolgenerating article in accordance with the invention is at least about 40 millimetres. Even more preferably, an overall length of an aerosol-generating article in accordance with the invention is at least about 45 millimetres. Even more preferably, an overall length of an aerosol-generating article in accordance with the invention is at least about 50 millimetres.

An overall length of an aerosol-generating article in accordance with the invention is preferably less than or equal to 1 10 millimetres. More preferably, an overall length of an aerosolgenerating article in accordance with the invention is preferably less than or equal to 100 millimetres. Even more preferably, an overall length of an aerosol-generating article in accordance with the invention is preferably less than or equal to 75 millimetres. Even more preferably, an overall length of an aerosol-generating article in accordance with the invention is preferably less than or equal to 70 millimetres.

For example, the overall length of the aerosol-generating article may be between about 35 millimetres and about 1 10 millimetres, or between about 40 millimetres and about 100 millimetres, or between about 45 millimetres and about 75 millimetres, or between about 50 millimetres and about 70 millimetres.

The aerosol-generating article preferably has an external diameter of at least about 5 millimetres. Preferably, the aerosol-generating article has an external diameter of at least 5.5 millimetres. More preferably, the aerosol-generating article has an external diameter of at least 6 millimetres.

Preferably, the aerosol-generating article has an external diameter of less than or equal to about 10 millimetres. More preferably, the aerosol-generating article has an external diameter of less than or equal to about 9 millimetres. Even more preferably, the aerosol-generating article has an external diameter of less than or equal to about 8 millimetres.

For example, the aerosol-generating article may have an external diameter of between about 5 millimetres and about 10 millimetres, or between about 5.5 millimetres and about 9 millimetres, or between about 6 millimetres and about 8 millimetres.

The external diameter of the aerosol-generating article may be substantially constant over the whole length of the article. As an alternative, different portions of the aerosol-generating article may have different external diameters. One or more of the components of the aerosol-generating article may be individually circumscribed by their own wrapper.

Preferably, the aerosol-generating substrate and the downstream section are combined together with a wrapper, such as a tipping wrapper.

Preferably, the components of the aerosol-generating article according to the present invention are made from biodegradable materials.

Preferably, the aerosol-generating articles according to the present invention as described herein are adapted for use in electrically-operated aerosol-generating systems in which the aerosol-generating substrate of the heated aerosol-generating article is heated by an electrical heat source.

The heating element of such aerosol-generating devices may be of any suitable form to conduct heat. The heating of the aerosol-generating substrate may be achieved internally, externally or both. The heating element may be a heater blade or pin adapted to be inserted into the aerosol-generating substrate so that the substrate is heated from inside. The heating element may preferably partially or completely surround the substrate and externally heat the substrate circumferentially from the outside.

The aerosol-generating system may be an electrically-operated aerosol generating system comprising an inductive heating device. Inductive heating devices typically comprise an induction source that is configured to be coupled to a susceptor, which may be provided externally to the aerosol-generating substrate or internally within the aerosol-generating substrate, as described above. The induction source generates an alternating electromagnetic field that induces magnetization or eddy currents in the susceptor. The susceptor may be heated as a result of hysteresis losses or induced eddy currents which heat the susceptor through ohmic or resistive heating.

Electrically operated aerosol-generating systems comprising an inductive heating device may also comprise the aerosol-generating article having the aerosol-generating substrate and a susceptor in thermal proximity to the aerosol-generating substrate. Typically, the susceptor is in direct contact with the aerosol-generating substrate and heat is transferred from the susceptor to the aerosol-generating substrate primarily by conduction. Examples of electrically operated aerosol-generating systems having inductive heating devices and aerosol-generating articles having susceptors are described in W0-A1 -95/27411 and W0-A1 -2015/177255.

The electrically operated aerosol-generating system may in some cases comprise an aerosol-generating article as defined above, a source of aerosol former and a means to vaporise the aerosol former, preferably a heating element. The source of aerosol former can be a reservoir, which can be refillable or replaceable, that resides on the aerosol generating device. While the reservoir is physically separate from the aerosol generating article, the vapour that is generated is directed through the aerosol-generating article. The vapour makes contact with the aerosol- generating substrate which releases volatile compounds, such as nicotine and flavorants in the particulate plant material, to form an aerosol. Optionally, to aid volatilization of compounds in the aerosol-generating substrate, the aerosol-generating system may further comprise a heating element to heat the aerosol-generating substrate, preferably in a co-ordinated manner with the aerosol former. However, the heating element used to heat the aerosol generating article may be separate from the heater that heats the aerosol former.

As described above, the hollow tubular substrate element of aerosol-generating articles according to the present invention can advantageously be adapted such that the length substantially matches the longitudinal dimensions of the heating element of the aerosolgenerating system which is intended to be used to heat the aerosol-generating article. This may ensure that the hollow tubular substrate element is heated along substantially its full length, so that the generation of aerosol from the aerosol-generating substrate can be maximised.

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, or embodiment, or aspect described herein.

EX1 : An aerosol-generating article comprising a rod of aerosol-generating substrate and a downstream section provided downstream of the rod of aerosol-generating substrate, wherein the rod of aerosol-generating substrate comprises a hollow tubular substrate element formed of homogenised tobacco material and an outer wrapper circumscribing the hollow tubular substrate element.

EX2: An aerosol-generating article according to EX1 , wherein the outer wrapper is arranged such that an empty space is defined between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper.

EX3: An aerosol-generating article according to EX2, wherein the hollow tubular substrate element comprises a plurality of perforations providing fluid communication between the longitudinal cavity of the hollow tubular substrate element and the outer wrapper.

EX4: An aerosol-generating article according to any one of EX1 to EX3, wherein the hollow tubular substrate element is formed of 2 or more overlapping layers of homogenised tobacco material.

EX5: An aerosol-generating article according to any one of EX1 to EX4, wherein the hollow tubular substrate element is formed of up to 10 overlapping layers of homogenised tobacco material.

EX6: An aerosol-generating article according to any one of EX1 to EX5, wherein the hollow tubular substrate element has a length of at least about 5 millimetres.

EX7: An aerosol-generating article according to any one of EX1 to EX6, wherein the hollow tubular substrate element has a length of up to about 30 millimetres. EX8: An aerosol-generating article according to any one of EX1 to EX7, wherein the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is at least about 0.1 .

EX9: An aerosol-generating article according to any one of EX1 to EX8, wherein the ratio of the length of the hollow tubular substrate element to the overall length of the aerosol-generating article is up to about 0.6.

EX10: An aerosol-generating article according to any one of EX1 to EX9, wherein the hollow tubular substrate element has an external diameter less than an external diameter of the aerosol-generating article.

EX1 1 : An aerosol-generating article according to any one of EX1 to EX10, wherein the hollow tubular substrate element has an external diameter of at least about 5 millimetres.

EX12: An aerosol-generating article according to any one of EX1 to EX1 1 , wherein the hollow tubular substrate element has an external diameter of up to about 9 millimetres.

EX13: An aerosol-generating article according to any one of EX1 to EX12, wherein the hollow tubular substrate element has a wall thickness that is at least about 4 percent of an external diameter of the hollow tubular substrate element.

EX14: An aerosol-generating article according to any one of EX1 to EX13, wherein the hollow tubular substrate element has a wall thickness that is up to about 40 percent of an external diameter of the hollow tubular substrate element.

EX15: An aerosol-generating article according to any one of EX1 to EX14, wherein the hollow tubular substrate element has a wall thickness of at least about 0.3 millimetres.

EX16: An aerosol-generating article according to any one of EX1 to EX15, wherein the hollow tubular substrate element has a wall thickness of up to about 3 millimetres.

EX17: An aerosol-generating article according to any one of EX1 to EX16, wherein the longitudinal cavity has a diameter of at least about 1 millimetre.

EX18: An aerosol-generating article according to any one of EX1 to EX17, wherein the longitudinal cavity has a diameter of up to about 8 millimetres.

EX19: An aerosol-generating article according to any one of EX3 to EX18, wherein the hollow tubular substrate element comprises one or more rows of perforations extending circumferentially around the hollow tubular substrate element.

EX20: An aerosol-generating article according to any one of EX3 to EX19, wherein the hollow tubular substrate element comprises at least two rows of perforations extending circumferentially around the hollow tubular substrate element.

EX21 : An aerosol-generating article according to any one of EX3 to EX20, wherein the hollow tubular substrate element comprises up to five rows of perforations extending circumferentially around the hollow tubular substrate element. EX22: An aerosol-generating article according to any one of EX19 to EX21 , wherein the circumferential rows of perforations are arranged circularly or helically around the hollow tubular substrate element.

EX23: An aerosol-generating article according to any one of EX20 to EX22, wherein each circumferential row of perforations comprises between 8 and 30 perforations.

EX24: An aerosol-generating article according to any one of EX3 to EX23, wherein the plurality of perforations comprise at least one perforation having a maximum dimension of at least about 200 micrometres or wherein each of the plurality of perforations have a maximum dimension of at least about 200 micrometres .

EX25: An aerosol-generating article according to any one of EX3 to EX24, wherein the plurality of perforations comprise at least one perforation having a maximum dimension of up to about 1 millimetre or wherein each of the plurality of perforations have a maximum dimension of up to about 1 millimetre.

EX26: An aerosol-generating article according to any one of EX3 to EX25, wherein the plurality of perforations comprise at least one perforation having an opening area of at least about 0.01 millimetres squared or wherein each of the plurality of perforations have an opening area of at least about 0.01 millimetres squared.

EX27: An aerosol-generating article according to any one of EX3 to EX26, wherein the plurality of perforations comprise at least one perforation having an opening area of no more than 1 millimetre squared or wherein each of the plurality of perforations have an opening area of no more than 1 millimetre squared.

EX28: An aerosol-generating article according to any one of EX3 to EX27, wherein the plurality of perforations have a total opening area of at least about 0.05 millimetres squared.

EX29: An aerosol-generating article according to any one of EX3 to EX28, wherein the plurality of perforations have a total opening area of up to about 30 millimetres squared.

EX30: An aerosol-generating article according to any one of EX3 to EX29, wherein the hollow tubular substrate element has a ventilation level of at least about 5 percent.

EX31 : An aerosol-generating article according to any one of EX3 to EX30, wherein the hollow tubular substrate element has a ventilation level of up to about 60 percent.

EX32: An aerosol-generating article according to any one of EX3 to EX31 , wherein the rod of aerosol-generating substrate comprises one or more susceptor elements located in contact with the hollow tubular substrate element.

EX33: An aerosol-generating article according to any one of EX1 to EX33, wherein the outer wrapper and the hollow tubular substrate element are unattached.

EX34: An aerosol-generating article according to any one of EX2 to EX33, wherein the rod of aerosol-generating substrate comprises one or more protrusions extending across the empty space between the external surface of the hollow tubular substrate element and the outer wrapper.

EX35: An aerosol-generating article according to EX33 or EX34 wherein the one or more protrusions are integral with the hollow tubular substrate element.

EX36: An aerosol-generating article according to any one of EX33 to Ex35, wherein the one or more protrusions are non-integral with the hollow tubular substrate element.

EX37: An aerosol-generating article according to EX33, EX34 or EX36 wherein the one or more protrusions are integral the outer wrapper.

EX38: An aerosol-generating article according to any one of EX33 to EX36 wherein the one or more protrusions are non-integral with the outer wrapper.

EX39: An aerosol-generating article according to any one of EX33 to EX36 and EX38 wherein the one or more protrusions are formed of homogenised tobacco material.

EX40: An aerosol-generating article according to any one of EX33 to EX39 wherein the one or more protrusions are arranged so that the empty space is non-continuous.

EX41 : An aerosol-generating article according to any one of EX1 to EX40, wherein the rod of aerosol-generating substrate comprises an upstream element adjacent to the upstream end of the hollow tubular substrate element.

EX42: An aerosol-generating article according to EX41 , wherein the upstream element abuts the upstream end of the hollow tubular substrate element.

EX43: An aerosol-generating article according to EX41 or EX42, wherein the outer wrapper circumscribes the hollow tubular substrate element and at least part of the upstream element.

EX44: An aerosol-generating article according to any one of EX41 to EX43, wherein the upstream element is an upstream plug element.

EX45: An aerosol-generating article according to any one of EX41 to EX44, wherein the external diameter of the upstream element is about the same as an external diameter of the aerosol-generating article.

EX46: An aerosol-generating article according to any one of EX41 to EX45, wherein the external diameter of the upstream element is greater than an external diameter of the hollow tubular substrate element.

EX47: An aerosol-generating article according to any one of EX41 to EX46, wherein an external diameter of at least a part of the hollow tubular substrate element is at least about 0.1 millimetres less than an external diameter of the upstream element.

EX48: An aerosol-generating article according to any one of EX41 to EX47, wherein the external diameter of at least a part of the hollow tubular substrate element is at least about 6 millimetres less than an external diameter of the upstream element. EX49: An aerosol-generating article according to any one of EX41 to EX48, wherein the upstream element has a length of between about 2 millimetres and about 15 millimetres.

EX50: An aerosol-generating article according to any one of EX1 to EX49, wherein the rod of aerosol-generating substrate comprises a downstream element adjacent to the downstream end of the hollow tubular substrate element.

EX51 : An aerosol-generating article according to EX50, wherein the downstream element abuts the downstream end of the hollow tubular substrate element.

EX52: An aerosol-generating article according to EX50 or EX51 , wherein the outer wrapper circumscribes the hollow tubular substrate element and at least part of the downstream element.

EX53: An aerosol-generating article according to any one of EX50 to EX52, wherein the downstream element is a downstream plug element.

EX54: An aerosol-generating article according to any one of EX50 to EX53, wherein the external diameter of the downstream element is about the same as an external diameter of the upstream element and an external diameter of the aerosol-generating article.

EX55: An aerosol-generating article according to any one of EX50 to EX54, wherein the external diameter of the downstream element is greater than an external diameter of the hollow tubular substrate element.

EX56: An aerosol-generating article according to any one of EX50 to EX55, wherein the downstream element has a length of between about 2 millimetres and about 15 millimetres.

EX57: An aerosol-generating article according to any one of EX1 to EX56, wherein within the empty space, the external surface of the hollow tubular substrate element and the outer wrapper is separated by at least about 0.05 millimetres in a radial direction.

EX58: An aerosol-generating article according to any one of EX1 to EX57, wherein within the empty space, the external surface of the hollow tubular substrate element and the outer wrapper is separated by up to about 3 millimetres in a radial direction.

EX59: An aerosol-generating article according to any one of EX1 to EX58, wherein the outer wrapper has a basis weight of between about 15 grams per square metre and about 100 grams per square metre.

EX60: An aerosol-generating article according to any one of EX1 to EX59, wherein the outer wrapper has a basis weight of at least about 80 grams per square metre.

EX61 : An aerosol-generating article according to any one of EX1 to EX60, wherein the outer wrapper comprises a plurality of perforations overlying the hollow tubular substrate element.

EX62: An aerosol-generating article according to EX61 wherein the plurality of perforations of the outer wrapper overlies the plurality of perforations of the hollow tubular substrate element. EX63: An aerosol-generating article according to any one of EX1 to EX62, wherein the aerosol-generating substrate has a length between about 10 millimetres and about 40 millimetres.

EX64: An aerosol-generating article according to any one of EX1 to EX63 wherein the downstream section comprises at least one hollow tubular element.

EX65: An aerosol-generating article according to EX64, wherein a ratio of the internal diameter of the hollow tubular substrate element to an internal diameter of the hollow tubular element of the downstream section is between about 0.8 and 1 .2.

EX66: An aerosol-generating article according to any one of EX1 to EX65 wherein the downstream section comprises a mouthpiece element.

EX67: An aerosol-generating article according to any to EX66, wherein the mouthpiece element comprises at least one segment of fibrous filtration material.

EX68: An aerosol-generating article according to any one of EX1 to EX67, wherein the downstream section comprises a mouth end cavity at the downstream end.

EX69: An aerosol-generating article according to any one of EX1 to EX68, wherein the downstream section has an overall length between about 15 millimetres and about 50 millimetres.

EX70: An aerosol-generating article according to any one of EX1 to EX69, wherein the aerosol-generating article has an overall length of between about 35 millimetres and about 1 10 millimetres.

EX71 : An aerosol-generating article according to any one of EX1 to EX70, wherein the outer wrapper comprises a plurality of perforations overlying the empty space.

EX72: An aerosol-generating article according to any one of EX1 to EX71 , wherein the empty space has an annular cross-section.

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

Figure 1 shows a schematic side-sectional view of an aerosol-generating article in accordance with a first embodiment of the present invention;

Figure 2 shows a schematic side sectional view of part of an aerosol-generating substrate comprising an aerosol-generating article in accordance with a second embodiment of the present invention and an aerosol-generating device.

The aerosol-generating article 10 shown in Figure 1 comprises a rod of aerosol-generating substrate 12 and a downstream section 14 provided downstream of the rod of aerosol-generating substrate 12. The aerosol-generating article 10 extends from an upstream or distal end 16 - which coincides with an upstream end of the aerosol-generating substrate 12 - to a downstream or mouth end 18, which coincides with a downstream end of the downstream section 14. The downstream section 14 comprises a hollow tubular element 20 and a mouthpiece element 50.

The aerosol-generating article 10 has an overall length of about 55 millimetres and an outer diameter of about 7.2 millimetres. The aerosol-generating substrate 12 comprises a hollow tubular substrate element 40 formed of homogenised tobacco material. The hollow tubular substrate element has a peripheral wall 42 which defines a longitudinal cavity 44 providing an unrestricted flow channel through the hollow tubular substrate element 40. The upstream end of the longitudinal cavity 44 provides an air inlet through which air can be drawn into the aerosol-generating article 10 during use. The hollow tubular substrate element 40 has a length of about 12 millimetres.

The aerosol-generating substrate also comprises an upstream plug element 70 of cellulose acetate tow abutting an upstream end of the hollow tubular substrate element 40 and a downstream plug element 80 of cellulose acetate tow abutting a downstream end of the hollow tubular substrate element 40. The upstream plug element 70 and the downstream plug element 80 each has a length of about 5 millimetres. The external diameter of the upstream plug element 70 is about the same as the external diameter of the downstream plug element 80 and about the same as the external diameter of the aerosol-generating article 10. The external diameter of the hollow tubular substrate element 40 is less than the external diameter of both the upstream plug element 70 and the downstream plug element 80.

The aerosol-generating substrate also comprises an outer wrapper 60 circumscribing the hollow tubular substate element 40, the upstream plug element 70 and the downstream plug element 80. The outer wrapper 60 is arranged such than an empty space 90 is defined between the external surface of the hollow tubular substrate element and the outer wrapper 60.

The hollow tubular substrate element 40 comprises two circumferential rows of perforations 46 providing fluid communication between the longitudinal cavity 44 of the hollow tubular substrate element 40 and the empty space 90 between the external surface of the hollow tubular substrate element 40 and the outer wrapper 60. The perforations 46 are provided through the peripheral wall 42 of the hollow tubular substrate element 40.

The outer wrapper 60 also comprises two rows of perforations 66 overlying the rows of perforations 46 in the hollow tubular substrate element 40.

The hollow tubular substrate element 40 does not substantially contribute to the overall RTD of the aerosol-generating article. The RTD of the hollow tubular substrate element 40 is therefore about 0 mm H₂O.

The hollow tubular element 20 of the downstream section 14 is located immediately downstream of the hollow tubular substrate element 40, the hollow tubular element 20 being in longitudinal alignment with the aerosol-generating substrate 12. The upstream end of the hollow tubular element 20 abuts the downstream end of the hollow tubular substrate element 40.

The hollow tubular element 20 is provided in the form of a hollow cylindrical tube made of cellulose acetate tow. The hollow tubular element 20 defines an internal cavity 22 that extends all the way from an upstream end of the hollow tubular element 20 to a downstream end of the hollow tubular element 20. The internal cavity 22 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 22. The hollow tubular element 20 does not substantially contribute to the overall RTD of the aerosol-generating article 10. The RTD of the hollow tubular element 20 is therefore about 0 mm H₂O.

As shown in Figure 1 , the internal diameter of the hollow tubular element 20 of the downstream section 14 is substantially the same as the internal diameter of the hollow tubular substrate element 40.

The mouthpiece element 50 extends from the downstream end of the hollow tubular element 20 to the downstream or mouth end 18 of the aerosol-generating article 10. The mouthpiece element 50 comprises a low-density, cellulose acetate filter segment. The mouthpiece element 50 may be individually wrapped by a plug wrap (not shown).

The article 10 comprises a tipping wrapper 52 circumscribing the hollow tubular element 20 and the mouthpiece element 50. The tipping wrapper 52 additionally overlies an upstream portion of the downstream plug element 80 in order to join the aerosol-generating substrate 12 and the downstream section 14.

The aerosol-generating article 10 is particularly suitable for use with an aerosol-generating device comprising external heating means, which heats the aerosol-generating substrate 12 externally. During use, the aerosol-generating article 10 is therefore preferably inserted into the heating cavity of an aerosol-generating device with the external surface of the hollow tubular substrate element 40 proximate the heating element or elements within the heating cavity. The heating of the hollow tubular substrate element 40 produces an aerosol from the homogenised tobacco material, which is released from both the internal surface of the hollow tubular substrate element 40 directly into the longitudinal cavity 44 of the hollow tubular substrate element 40 and from the external surface of the hollow tubular substrate element 40 into the empty space 90 defined between the outer wrapper 60 and the external surface of the hollow tubular substrate element 40. When a consumer draws on the aerosol-generating article 10, aerosol released into the empty space 90 is drawn into the longitudinal cavity 44 of the hollow tubular substrate element 40, together with air that is entering the empty space 90 through the plurality of perforations 66 in the outer wrapper 60, through the plurality of perforations 46 in the hollow tubular substrate element 40. Air also enters the longitudinal cavity 44 of the hollow tubular substrate element 40 at the upstream end, as the consumer draws on the article 10. The combined air and aerosol are drawn through the aerosol-generating article 10 and delivered to the consumer from the downstream end 18 of the aerosol-generating article 10.

Figure 2 illustrates part of an aerosol-generating system 100 comprising an aerosolgenerating device 102 and an aerosol-generating article 110 according to a second embodiment of the invention. The aerosol-generating article 1 10 is similar to that shown in Figure 1 and described above, with a similar arrangement of components. However, the aerosol-generating substrate additionally comprises a plurality of protrusions 140 extending across the empty space 90 between the external surface of the hollow tubular substrate element 140 and the outer wrapper 160. The outer wrapper 160 wraps around the plurality of protrusions 148 to help to hold the hollow tubular substrate element 140 in pace and retain the empty space 90 between the hollow tubular substrate element 140 and the outer wrapper 160. The plurality of protrusions 148 are physically distinct from the hollow tubular substrate element 140 and are attached directly to the external surface of the hollow tubular substrate element 140.

As shown in Figure 2, the aerosol-generating device 102 comprises a longitudinal heating cavity 104 for receiving the aerosol-generating article 1 10. The heating cavity 104 has a closed, distal end and an open, mouth end. Air flow inlets 106 are provided at the distal end of the cavity so that air can be drawn through the aerosol-generating article 110 during use. The heating cavity 104 comprises an external heating element 108 for resistively heating the aerosol-generating substrate of the aerosol-generating article 110 during use.

The aerosol-generating device 102 further comprises a power source (not shown) and a controller (not shown) to controllably heat the aerosol-generating article 1 10 during use, when the aerosol-generating article 1 10 is received within the device 102.

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

Claims

CLAIMS:

1. An aerosol-generating article comprising: a rod of aerosol-generating substrate and a downstream section provided downstream of the rod of aerosol-generating substrate, wherein the rod of aerosol-generating substrate comprises: a hollow tubular substrate element formed of homogenised tobacco material and defining a longitudinal cavity providing an unrestricted flow channel through the hollow tubular substrate element; an outer wrapper circumscribing the hollow tubular substrate element and arranged such that an empty space is defined between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper; wherein the hollow tubular substrate element comprises a plurality of perforations providing fluid communication between the longitudinal cavity of the hollow tubular substrate element and the empty space between at least a part of the external surface of the hollow tubular substrate element and the outer wrapper, wherein the plurality of perforations of the hollow tubular substrate element is formed through a peripheral wall of the hollow tubular substrate element, and wherein the outer wrapper comprises a plurality of perforations overlying the hollow tubular substrate element.

2. An aerosol-generating article according to claim 1 , wherein the hollow tubular substrate element comprises at least two rows of perforations extending circumferentially around the hollow tubular substrate element.

3. An aerosol-generating article according to claim 1 or 2, wherein each of the plurality of perforations of the hollow tubular substrate element has an opening area of at least about 0.01 millimetres squared.

4. An aerosol-generating article according to any preceding claim, wherein the hollow tubular substrate element has a wall thickness that is between about 5 percent and about 40 percent of the external diameter of the hollow tubular substrate element.

5. An aerosol-generating article according to any preceding claim, wherein within the empty space the external surface of the hollow tubular substrate element and the outer wrapper are separated by at least about 0.1 millimetres in a radial direction.

6. An aerosol-generating article according to any preceding claim, wherein the outer wrapper and the hollow tubular substrate element are unattached.

7. An aerosol-generating article according to any preceding claim, wherein the plurality of perforations of the outer wrapper overlies the perforations in the hollow tubular substrate element.

8. An aerosol-generating article according to any preceding claim, wherein the rod of aerosol-generating substrate further comprises an upstream plug element adjacent to the upstream end of the hollow tubular substrate element, wherein the outer wrapper circumscribes the hollow tubular substrate element and at least a part of the upstream element.

9. An aerosol-generating article according to claim 8, wherein at least a part of the hollow tubular substrate element has an external diameter that is at least about 0.2 millimetres less than the external diameter of the upstream plug element.

10. An aerosol-generating article according to claim 8 or 9, wherein the rod of aerosolgenerating substrate further comprises a downstream plug element adjacent to the downstream end of the hollow tubular substrate element and having the same external diameter as the upstream plug element.

11. An aerosol-generating article according to any preceding claim, wherein the rod of aerosol-generating substrate comprises one or more protrusions extending across the empty space between the external surface of the hollow tubular substrate element and the outer wrapper.

12. An aerosol-generating article according to any preceding claim, wherein the outer wrapper has a basis weight of at least about 80 grams per square metre.

13. An aerosol-generating article according to any preceding claim, wherein the hollow tubular substrate element is formed of two or more overlapping sheets of homogenised tobacco material.

14. An aerosol-generating article according to any preceding claim, wherein the downstream section comprises at least one hollow tubular element adjacent to the downstream end of the rod of aerosol-generating substrate.

15. An aerosol-generating article according to any preceding claim, wherein the downstream section comprises at least one mouthpiece filter element.