Smoking article with dual heat-conducting elements and improved airflow

Abstract

The present invention discloses a smoking article (2), comprising: a combustible heat source (4) having a relative front (6) and a rear (8); an aerosol-forming substrate (10) downstream of the rear (8) of the combustible heat source (4); a first heat-conducting element (36) surrounding the rear (4b) of the combustible heat source (4) and at least the front (10a) of the aerosol-forming substrate (10); a second heat-conducting element (38) surrounding at least a portion of the first heat-conducting element (36), wherein at least a portion of the second heat-conducting element (38) is radially separated from the first heat-conducting element (36); and one or more first air inlets (40) surrounding the periphery of the aerosol-forming substrate (10).

Description

[0001] The present application is a divisional application of the invention patent application entitled “Smoking article with dual heat conduction elements and improved airflow”, with an international application date of August 12, 2014, an international application number of PCT / EP2014 / 067236, and a national application number of 201480033018.X. Technical Field

[0002] The present invention relates to a smoking article comprising a combustible heat source having opposing front and rear faces, an aerosol-forming substrate and a dual heat-conducting element around the smoking article, the combustible heat source having opposing front and rear faces, the aerosol-forming substrate downstream of the rear face of the combustible heat source. Background Art

[0003] A variety of smoking articles in which tobacco is heated rather than burned have been proposed in the art. One purpose of such 'heated' smoking articles is to reduce the harmful smoke components of known types produced by the burning and thermal degradation of tobacco in traditional cigarettes. In a known type of heated smoking article, aerosol is produced by heat transfer from a combustible heat source to an aerosol-forming substrate. The aerosol-forming substrate may be located in, around, or downstream of the combustible heat source. During smoking, volatile compounds are released from the aerosol-forming substrate by heat transfer from the combustible heat source and are entrained in the air drawn by the smoking article. As the released compounds cool, the compounds condense to form an aerosol inhaled by the user. Typically, air is inhaled into such known heated smoking articles by passing through one or more airflow channels provided by the combustible heat source, and heat transfer from the combustible heat source to the aerosol-forming substrate is achieved by forced convection and conduction.

[0004] For example, WO-A2-2009 / 022232 discloses a smoking article comprising a combustible heat source, an aerosol-forming substrate downstream of the combustible heat source, and a heat-conducting element surrounding and contacting a rear portion of the combustible heat source and an adjacent front portion of the aerosol-forming substrate.

[0005] The heat conduction element in the smoking article of WO-A2-2009 / 022232 transfers the heat generated during the combustion of the combustible heat source to the aerosol-forming substrate by conduction. The heat loss generated by conductive heat transfer significantly reduces the temperature of the rear portion of the combustible heat source, so that the temperature of the rear portion remains significantly below its auto-ignition temperature.

[0006] In the smoking article where tobacco is heated instead of burned, the temperature reached in the aerosol-forming substrate has a significant impact on the ability to generate aerosol that is acceptable to the senses. It is usually desirable to maintain the temperature of the aerosol-forming substrate within a certain range in order to optimize the aerosol delivery to the user. In some cases, the radiant heat loss from the outer surface of the heat-conducting element surrounding and contacting the combustible heat source and the aerosol-forming substrate may cause the temperature of the combustible heat source and the aerosol-forming substrate to drop outside the desired range, thus affecting the performance of the smoking article. If the temperature of the aerosol-forming substrate drops too low, for example, it may adversely affect the consistency and amount of the aerosol delivered to the user.

[0007] In some heated smoking articles, in addition to conductive heat transfer via a heat-conducting element, forced convective heat transfer to the aerosol-forming substrate is provided. For example, in some known heated smoking articles, one or more airflow channels are provided through a combustible heat source to provide forced convective heating of the aerosol-forming substrate. In such smoking articles, the aerosol-forming substrate is heated by a combination of conductive heating and forced conductive heating.

[0008] In known heated smoking articles, in which heat transfer from the combustible heat source to the aerosol-forming substrate occurs primarily by forced convection, this forced convection heat transfer, and hence the temperature in the aerosol-forming substrate, can vary considerably depending on the user's puffing action. Consequently, the composition, and hence the sensory properties, of the mainstream aerosol generated by such known heated smoking articles can be disadvantageously highly sensitive to the user's puffing regime.

[0009] In addition, in a known heated smoking article comprising one or more airflow channels along a combustible heat source, during a single puff by a user, direct contact between the air sucked through the one or more airflow channels and the combustible heat source causes the excitation of the combustion of the combustible heat source. A strong single puff state can therefore result in sufficiently high forced conduction heat transfer to cause a peak value of the temperature of the aerosol-forming substrate, thereby unfavorably causing pyrolysis of the aerosol-forming substrate and even potential local combustion. As used herein, the term 'peak' is used to describe a short rise in the temperature of the aerosol-forming substrate. Therefore, the level of undesirable pyrolysis and combustion byproducts in the mainstream aerosol produced by this known heated smoking article may also unfavorably vary significantly depending on the specific single puff state adopted by the user.

[0010] In other heated smoking articles, no airflow channel is provided through the combustible heat source. In such heated smoking articles, the heating of the aerosol-forming substrate is mainly achieved by conductive heat transfer via a heat-conducting element. In a heated smoking article in which the aerosol-forming substrate is heated mainly by conductive heat transfer, the temperature of the aerosol-forming substrate may become more sensitive to changes in the temperature of the heat-conducting element. This means that any cooling of the heat-conducting element due to the radiant heat loss in such heated smoking articles may have a greater impact on aerosol generation compared to a heated smoking article in which the aerosol-forming substrate is also heated by forced convection heat transfer.

[0011] EP-A2-0 336 456 discloses a smoking article comprising a combustible fuel element and a physically separate aerosol-forming means in conductive heat exchange relationship with the fuel element. Figure 2 In the embodiment shown in , the combustible fuel element 24 is connected to the aerosol forming tool 12 by a heat transfer rod 26 and a foil lined paper tube 14, which leads to the mouth end 15 of the smoking article. The aerosol forming tool 12 includes a carbonaceous matrix 28 impregnated with one or more aerosol forming materials. A void space 30 is included between the fuel element 24 and the carbonaceous matrix 28 of the aerosol forming tool 12. A portion of the foil lined tube 14 surrounding the void space 30 includes a plurality of peripheral holes 32, which allow air to enter the void space 30. In this embodiment, the heat transfer rod 26 is inserted into the body of the combustible fuel element 24 and the carbonaceous matrix 28 of the aerosol forming tool 12, and there is no air inlet in the portion of the foil lined tube 14 surrounding the carbonaceous matrix 28 of the aerosol forming tool 12.

[0012] It is known to include additives in the combustible heat source of heated smoking articles in order to improve the ignition and combustion characteristics of the combustible heat source. However, the inclusion of ignition and combustion additives can produce decomposition and reaction products that can disadvantageously enter the air drawn therethrough during use of such known heated smoking articles.

[0013] In order to promote aerosol formation, the aerosol-forming substrate of the heated smoking article generally comprises a polyol such as glycerol or other known aerosol formers. During storage and smoking, such aerosol formers may migrate from the aerosol-forming substrate of the known heated smoking article to its combustible heat source. The migration of the aerosol former to the combustible heat source of the known heated smoking article may disadvantageously lead to the decomposition of the aerosol former, particularly during the smoking of the heated smoking article.

[0014] It would be desirable to provide a heated smoking article comprising a combustible heat source and an aerosol-forming substrate, the combustible heat source having an opposing front and rear face, the aerosol-forming substrate being downstream of the rear face of the combustible heat source, which provides improved smoking performance. In particular, it would be desirable to provide a heated smoking article in which there is improved control of the heating of the aerosol-forming substrate so as to help maintain the temperature of the aerosol-forming substrate within a desired temperature range during smoking. Summary of the invention

[0015] According to the present invention, there is provided a smoking article comprising: a combustible heat source having a relative front and rear; an aerosol-forming substrate downstream of the rear of the combustible heat source; a first heat-conducting element surrounding the rear of the combustible heat source and at least the front of the aerosol-forming substrate; a second heat-conducting element surrounding at least a portion of the first heat-conducting element, wherein at least a portion of the second heat-conducting element is radially separated from the first heat-conducting element; and one or more first air inlets surrounding the periphery of the aerosol-forming substrate.

[0016] As used herein, the terms 'distal', 'upstream' and 'front', and 'proximal', 'downstream' and 'rear' are used to describe the relative position of components or parts of components of a smoking article with respect to the direction in which a user draws on the smoking article during use of the smoking article. The smoking article according to the present invention comprises a proximal end, through which, in use, aerosol leaves the smoking article for delivery to the user. The proximal end of the smoking article may also be referred to as a mouth end, and in use, a user draws on the proximal end of the smoking article in order to inhale the aerosol generated by the smoking article.

[0017] The combustible heat source is located at or near the distal end. The mouth end is downstream of the distal end. The proximal end may also be referred to as the downstream end of the smoking article, and the distal end may also be referred to as the upstream end of the smoking article. Components or parts of components of smoking articles according to the present invention may be described as being upstream or downstream of each other based on their relative positions between the proximal end and the distal end of the smoking article.

[0018] The front face of the combustible heat source is at the upstream end of the combustible heat source. The upstream end of the combustible heat source is the end of the combustible heat source farthest from the proximal end of the smoking article. The rear face of the combustible heat source is at the downstream end of the combustible heat source. The downstream end of the combustible heat source is the end of the combustible heat source closest to the proximal end of the smoking article.

[0019] As used herein, the term 'length' is used to describe the largest dimension in the longitudinal direction of the smoking article. That is, the largest dimension in the direction between the proximal end and the opposite distal end of the smoking article.

[0020] As used herein, the term 'aerosol-forming substrate' is used to describe a substrate that is capable of releasing volatile compounds that can form an aerosol when heated. The aerosol generated from the aerosol-forming substrate of the smoking article according to the invention may be visible or invisible, and may include vapor (e.g., fine particulate matter in a gaseous state that is typically liquid or solid at room temperature) and droplets of gas and condensed vapor.

[0021] The aerosol-forming substrate may take the form of a formed piece or segment confined by a wrapper, the formed piece or segment comprising a material capable of releasing volatile compounds that can form an aerosol when heated. When the aerosol-forming substrate takes the form of such a formed piece or segment, the entire formed piece or segment including the wrapper is regarded as the aerosol-forming substrate.

[0022] As used herein, the term 'air inlet' is used to describe a hole, slit, slot or other aperture through which air can be drawn into the smoking article.

[0023] The first heat-conducting element and the second heat-conducting element comprise a heat-conducting material.

[0024] As used herein, the term “radially separated” is used to indicate that at least a portion of the heat-conductive material of the second heat-conducting element is spaced apart from the heat-conductive material of the first heat-conducting element in a radial direction such that there is no direct contact between at least a portion of the heat-conductive material of the second heat-conducting element and the heat-conductive material of the first heat-conducting element.

[0025] As used herein, the term 'radial' is used to describe a direction perpendicular to the direction between a proximal end and an opposite distal end of the smoking article.

[0026] As used herein, the term 'direct contact' is used to mean contact between two components without any intermediate material such that the surfaces of the components touch each other.

[0027] Smoking articles according to the invention comprise a first heat-conducting element surrounding a rear portion of a combustible heat source and at least a front portion of an aerosol-forming substrate, and a second heat-conducting element surrounding at least a portion of the first heat-conducting element.

[0028] In certain embodiments, the first heat-conducting element may be in direct contact with a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate. In such embodiments, the rear portion of the combustible heat source is surrounded by and in direct contact with the first heat-conducting element, and at least the front portion of the aerosol-forming substrate is surrounded by and in direct contact with the first heat-conducting element. In such embodiments, the first heat-conducting element provides thermal communication between the combustible heat source and the aerosol-forming substrate of a smoking article according to the invention.

[0029] In other embodiments, the first heat-conducting element may be spaced apart in a radial direction from one or both of the rear portion of the combustible heat source and the aerosol-forming substrate such that there is no direct contact between the first heat-conducting element and one or both of the rear portion of the combustible heat source and the aerosol-forming substrate.

[0030] The second heat-conducting element overlies at least a portion of the first heat-conducting element.At one or more locations along the smoking article, there is a radial separation between the first heat-conducting element and the second heat-conducting element.

[0031] Preferably, all or substantially all of the second heat-conducting element is radially separated from the first heat-conducting element so that there is substantially no direct contact between the first heat-conducting element and the second heat-conducting element. This advantageously limits or prevents conductive heat transfer from the first heat-conducting element to the second heat-conducting element.

[0032] Preferably, conductive heat transfer from the first heat-conducting element to the second heat-conducting element is substantially reduced. This advantageously results in the second heat-conducting element being maintained at a lower temperature than the first heat-conducting element. In a preferred embodiment, radiative heat loss from the outer surface of the smoking article is substantially reduced compared to a smoking article that does not include a second heat-conducting element surrounding at least a portion of the first heat-conducting element.

[0033] The second heat-conducting element advantageously reduces heat loss from the first heat-conducting element. The second heat-conducting element comprises a heat-conducting material that increases in temperature during smoking of the smoking article when heat is generated by the combustible heat source. The increase in temperature of the second heat-conducting element reduces the temperature difference between the first heat-conducting element and the overlying component of the smoking article, so that heat loss from the first heat-conducting element can be reduced.

[0034] By reducing heat losses from the first heat-conducting element, the second heat-conducting element advantageously helps to better maintain the temperature of the first heat-conducting element within a desired temperature range. The second heat-conducting element advantageously helps to more effectively use the heat from the combustible heat source to heat the aerosol-forming substrate to a desired temperature range. In a further advantage, the second heat-conducting element helps to maintain the temperature of the aerosol-forming substrate at a higher level. The second heat-conducting element in turn improves the aerosol generation from the aerosol-forming substrate. Advantageously, the second heat-conducting element increases the overall aerosol delivery to the user. In particular, it can be seen that when the aerosol-forming substrate contains nicotine, the nicotine delivery to the user can be significantly improved by including the second heat-conducting element.

[0035] Additionally, it has been found that the inclusion of a second heat-conducting element advantageously extends the puff duration of the smoking article, allowing a user to take a greater number of puffs.

[0036] In certain preferred embodiments, the second heat-conducting element conducts heat from the combustible heat source along the smoking article in the same manner as the first heat-conducting element. In such embodiments, the second heat-conducting element may also improve the efficiency of conductive heat transfer from the combustible heat source to the aerosol-forming substrate, and thereby improve the heating of the aerosol-forming substrate.

[0037] The improvement in conductive heat transfer achieved by including a second heat-conducting element is particularly advantageous for smoking articles in which there is substantially no forced convection heat transfer.

[0038] The radial separation between the first heat-conducting element and the second heat-conducting element is preferably achieved by including one or more intermediate material layers between the first heat-conducting element and the second heat-conducting element. The one or more intermediate material layers may be provided over the entire area in which the second heat-conducting element overlies the first heat-conducting element. Alternatively, the one or more intermediate material layers may be provided only in one or more portions of the area. In some cases, the one or more intermediate material layers may extend beyond one or both of the first heat-conducting element and the second heat-conducting element in one or both of the upstream direction and the downstream direction.

[0039] Preferably, the first heat-conducting element and the second heat-conducting element are radially separated by one or more layers of thermally insulating material. Suitable thermally insulating materials include, but are not limited to, paper, ceramics and metal oxides.

[0040] For example, in a preferred embodiment of the present invention, the first heat-conducting element is covered by a paper wrapper that surrounds the smoking article along at least a portion of its length. In such embodiments, the paper wrapper advantageously provides complete separation of the first heat-conducting element and the second heat-conducting element, so that there is no direct contact between the first heat-conducting element and the second heat-conducting element.

[0041] In some embodiments, the first heat-conducting element and the second heat-conducting element are radially separated by an inner wrapper or an outer wrapper that extends along all or only a portion of the smoking article. In such embodiments, the inner wrapper or the outer wrapper is wrapped around the smoking article on the first heat-conducting element, and the second heat-conducting element is then provided on at least a portion of the inner wrapper or the outer wrapper.

[0042] Preferably, the second heat-conducting element is provided on the exterior of the smoking article such that the second heat-conducting element is visible on the exterior of the smoking article.

[0043] Alternatively, an outer wrapper extending along all or only a portion of the smoking article may be provided over the second heat-conducting element, such that the second heat-conducting element is not visible or is only partially visible on the exterior of the smoking article.

[0044] The provision of the second heat-conducting element on the wrapper of the smoking article can provide the benefit related to the appearance of the smoking article according to the present invention, particularly during and after its smoking. In some cases, when the wrapper is exposed to the heat from the combustible heat source, some discoloration of the wrapper in the area of ​​the combustible heat source can be observed. The wrapper can be discolored in the wrapper around and downstream of the aerosol-forming substrate due to the migration of volatile compounds from the aerosol-forming substrate. In certain embodiments, the second heat-conducting element of the smoking article according to the present invention can be provided on a wrapper, and the wrapper surrounds at least the rear portion of the combustible heat source and at least the front portion of the aerosol-forming substrate, so that the discoloration of the wrapper is hidden and no longer visible or less visible. In certain embodiments, the second heat-conducting element can extend around the entire length of the aerosol-forming substrate. In some preferred embodiments, the second heat-conducting element can extend downstream beyond the aerosol-forming substrate. The initial appearance of the smoking article can therefore be retained during smoking.

[0045] Alternatively or additionally to the one or more layers of insulating material between the first heat-conducting element and the second heat-conducting element, at least a portion of the second heat-conducting element may be radially separated from the first heat-conducting element by an air gap. The air gap may be provided by including one or more spacer elements between the first heat-conducting element and the second heat-conducting element to maintain a defined separation between at least a portion of the second heat-conducting element and the first heat-conducting element. The one or more spacer elements may be, for example, one or more paper strips wrapped radially around the first heat-conducting element.

[0046] Preferably, the first and second heat-conducting elements are radially separated from each other by at least 20 microns, more preferably at least 50 microns. In certain embodiments, the first and second heat-conducting elements are radially separated from each other by at least 75 microns or more, or at least 100 microns or more.

[0047] When one or more layers of thermally insulating material are provided between the first heat-conducting element and the second heat-conducting element as described above, the radial separation of the first heat-conducting element and the second heat-conducting element will be determined by the thickness of the one or more layers of thermally insulating material.

[0048] As described above, the first heat-conducting element of the smoking article according to the present invention is preferably in direct contact with the rear portion of the combustible heat source and at least the front portion of the aerosol-forming substrate. The first heat-conducting element is preferably flame-resistant. In certain embodiments, the first heat-conducting element is oxygen-restrictive. In such embodiments, the first heat-conducting element prevents or resists the passage of oxygen through the first heat-conducting element to the combustible heat source.

[0049] In particularly preferred embodiments, the first heat-conducting element forms a continuous sleeve that closely surrounds a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate.

[0050] In certain embodiments, the first heat-conducting element provides a substantially airtight connection between the combustible heat source and the aerosol-forming substrate. This may advantageously prevent or inhibit combustion gases from the combustible heat source from being easily drawn through its periphery into the aerosol-forming substrate. Such a connection may also advantageously minimise or substantially avoid forced convective heat transfer from the combustible heat source to the aerosol-forming substrate by air drawn along the periphery of the combustible heat source and the aerosol-forming substrate.

[0051] Preferably, the physical integrity of the first heat-conducting element is maintained at temperatures reached by the combustible heat source during ignition and combustion. In embodiments in which the first heat-conducting element provides a substantially airtight connection between the combustible heat source and the aerosol-forming substrate, this advantageously helps maintain the airtight connection during use of the smoking article.

[0052] The first heat-conducting element may comprise any suitable heat-conductive material or combination of materials having suitable thermal conductivity.

[0053] Preferably, the first heat-conducting element comprises one or more heat-conductive materials having an overall thermal conductivity of about 10 Watts per meter Kelvin (W / (m·K)) to about 500 Watts per meter Kelvin (W / (m·K)), more preferably about 15 Watts per meter Kelvin (W / (m·K)) to about 400 Watts per meter Kelvin (W / (m·K)) at 23°C and 50% relative humidity as measured using a modified transient plane heat source (MTPS) method. Suitable heat-conductive materials include, but are not limited to: metal foil wrappers, such as aluminum foil wrappers, steel wrappers, iron foil wrappers, and copper foil wrappers; and metal alloy foil wrappers.

[0054] The first heat-conducting element may be formed of a single layer of heat-conducting material. Alternatively, the first heat-conducting element may be formed of a multi-layer or laminate material comprising at least one layer of heat-conducting material in combination with one or more other heat-conducting layers or non-heat-conducting layers. In such embodiments, the at least one layer of heat-conducting material may comprise any of the heat-conducting materials listed above.

[0055] In certain embodiments, the first heat-conducting element may be formed of a laminate material comprising at least one layer of heat-conductive material and at least one layer of heat-insulating material. In such embodiments, an inner layer of the first heat-conducting element facing the rear portion of the combustible heat source and at least the front portion of the aerosol-forming substrate may be a layer of heat-conductive material, and an outer layer of the first heat-conducting element facing the second heat-conducting element may be a layer of heat-insulating material. In this way, the outer layer of heat-insulating material provides the desired radial separation between the heat-conductive material of the second heat-conducting element and the heat-conductive material of the first heat-conducting element.

[0056] An example of a particularly suitable laminate material for forming the first heat-conducting element is a two-layer laminate comprising an outer layer of paper and an inner layer of aluminium.

[0057] Preferably, the thickness of the first heat-conducting element is about 5 microns to about 50 microns, more preferably about 10 microns to about 30 microns, and most preferably about 20 microns. In certain particularly preferred embodiments, the first heat-conducting element comprises aluminum foil having a thickness of about 20 microns.

[0058] Preferably, the rear portion of the combustible heat source surrounded by the first heat-conducting element is from about 2 mm to about 8 mm in length, more preferably from about 3 mm to about 5 mm in length.

[0059] Preferably, the front portion of the combustible heat source not surrounded by the first heat-conducting element is from about 4 mm to about 15 mm in length, more preferably from about 5 mm to about 8 mm in length.

[0060] In certain embodiments, the entire length of the aerosol-forming substrate may be surrounded by the first heat-conducting element.

[0061] In other embodiments, the first heat-conducting element may surround only a front portion of the aerosol-forming substrate.In such embodiments, the aerosol-forming substrate extends downstream beyond the first heat-conducting element.

[0062] In embodiments in which the first heat-conducting element surrounds only the front portion of the aerosol-forming substrate, the aerosol-forming substrate preferably extends downstream beyond the first heat-conducting element by at least about 3 mm. More preferably, the aerosol-forming substrate extends downstream beyond the first heat-conducting element by about 3 mm to about 10 mm. However, the aerosol-forming substrate may extend downstream beyond the first heat-conducting element by less than 3 mm.

[0063] In such embodiments, the front portion of the aerosol-forming substrate surrounded by the first heat-conducting element is preferably from about 1 mm to about 10 mm in length, more preferably from about 2 mm to about 8 mm in length, most preferably from about 2 mm to about 6 mm in length.

[0064] The second heat-conducting element is provided around at least a portion of the first heat-conducting element.

[0065] The second heat-conducting element may extend around all or part of the circumference of the smoking article.Preferably, the second heat-conducting element forms a continuous sleeve which surrounds at least a part of the first heat-conducting element.

[0066] The second heat-conducting element may comprise any suitable heat-conductive material or combination of materials having suitable thermal conductivity.

[0067] Preferably, the second heat-conducting element comprises one or more heat-conductive materials having an overall thermal conductivity of about 10 Watts per meter Kelvin (W / (m·K)) to about 500 Watts per meter Kelvin (W / (m·K)), more preferably about 15 Watts per meter Kelvin (W / (m·K)) to about 400 Watts per meter Kelvin (W / (m·K)) at 23°C and 50% relative humidity as measured using a modified transient plane heat source (MTPS) method. Suitable heat-conductive materials include, but are not limited to: metal foil wrappers, such as aluminum foil wrappers, steel wrappers, iron foil wrappers, and copper foil wrappers; and metal alloy foil wrappers.

[0068] The first heat-conducting element and the second heat-conducting element may comprise the same or different heat-conducting material or materials.

[0069] In certain preferred embodiments, the first heat-conducting element and the second heat-conducting element comprise the same heat-conducting material. In certain preferred embodiments, the first heat-conducting element and the second heat-conducting element comprise aluminum foil.

[0070] Preferably, the second heat-conducting element comprises one or more heat reflective materials, such as aluminium or steel. In such embodiments, in use, the second heat-conducting element advantageously reflects heat radiation from the first heat-conducting element back to the first heat-conducting element. This also reduces heat losses from the first heat-conducting element, so that the temperature of the first heat-conducting element can be better controlled and the combustible heat source can be maintained at a higher temperature.

[0071] As used herein, the term 'thermal reflective material' refers to a material having a relatively high thermal reflectivity and a relatively low thermal emissivity, such that the material reflects a greater proportion of incident radiation from its surface than it emits. Preferably, the material reflects more than 50% of the incident radiation, more preferably more than 70% of the incident radiation, and most preferably more than 75% of the incident radiation.

[0072] In embodiments in which the second heat-conducting element comprises a heat reflective material, preferably all or substantially all of the second heat-conducting element is radially separated from the first heat-conducting element so as to promote reflection of heat by the second heat-conducting element towards the first heat-conducting element.

[0073] The reflectivity of the second heat-conducting element may be improved by providing the second heat-conducting element with a shiny inner surface, wherein the inner surface is the surface of the second heat-conducting element that faces the outer surface of the first heat-conducting element.

[0074] The second heat-conducting element may be formed of a single layer of heat-conducting material. Alternatively, the second heat-conducting element may be formed of a multi-layer or laminate material comprising at least one layer of heat-conducting material in combination with one or more other heat-conducting layers or non-heat-conducting layers. In such embodiments, the at least one layer of heat-conducting material may comprise any of the heat-conducting materials listed above.

[0075] In certain preferred embodiments, the second heat-conducting element may be formed of a laminate material comprising at least one layer of heat-conductive material and at least one layer of heat-insulating material. In such embodiments, the inner layer of the second heat-conducting element facing the first heat-conducting element may be a layer of heat-insulating material. In this way, the inner layer of heat-insulating material provides the desired radial separation between the heat-conductive material of the second heat-conducting element and the heat-conductive material of the first heat-conducting element.

[0076] In certain preferred embodiments, the second heat-conducting element comprises a single layer of heat-conductive material.

[0077] In certain preferred embodiments, the second heat-conducting element is a laminate comprising a single layer of heat-conductive material and one or more layers of heat-insulating material. In certain particularly preferred embodiments, the second heat-conducting element is a laminate comprising a single layer of heat-conductive material and a single layer of heat-insulating material. Preferably, the second heat-conducting element is a laminate comprising a single outer layer of heat-conductive material and a single inner layer of heat-insulating material.

[0078] An example of a particularly suitable laminate material for forming the second heat-conducting element is a two-layer laminate comprising an outer layer of aluminium and an inner layer of paper.

[0079] The use of a second heat-conducting element comprising a laminate may be further advantageous during the production of smoking articles according to the invention, since the at least one heat-insulating layer may provide additional strength and rigidity. This allows the laminate to be processed more easily, with a reduced risk of collapse or fracture of the at least one heat-conducting layer, which may be relatively thin and fragile.

[0080] The thickness of the second heat-conducting element may be substantially the same as the thickness of the first heat-conducting element.Alternatively, the first heat-conducting element and the second heat-conducting element may have different thicknesses from each other.

[0081] Preferably, the second heat-conducting element has a thickness of about 5 microns to about 100 microns, more preferably about 5 microns to about 80 microns.

[0082] Preferably, the second heat-conducting element comprises one or more layers of heat-conductive material having a thickness of about 2 microns to about 50 microns, more preferably about 4 microns to about 30 microns.

[0083] In certain embodiments, the second heat-conducting element may comprise an aluminum foil having a thickness of about 20 microns.

[0084] In certain preferred embodiments, the second heat-conducting element may comprise a laminate material comprising an outer layer of aluminum and an inner layer of paper having a thickness of about 5 microns to about 6 microns.

[0085] The position and extent of the second heat-conducting element relative to the first heat-conducting element, the combustible heat source and the aerosol-forming substrate may be adjusted in order to control the heating of the aerosol-forming substrate during smoking.

[0086] The second heat-conducting element may be placed around at least a portion of the aerosol-forming substrate.Alternatively or additionally, the second heat-conducting element may be placed around at least a portion of the combustible heat source.

[0087] Preferably, the second heat-conducting element is placed around at least a portion of the aerosol-forming substrate and at least a portion of the combustible heat source, in a similar manner to the first heat-conducting element.

[0088] Depending on the desired performance of the smoking article, the extent of the second heat-conducting element relative to the first heat-conducting element in both the upstream and downstream directions may be adjusted.

[0089] The second heat-conducting element overlies at least a portion of the first heat-conducting element.

[0090] The second heat-conducting element may substantially surround the same combustible heat source and aerosol-forming substrate area as the first heat-conducting element, such that the first heat-conducting element and the heat-conducting element extend along the same length of the smoking article. In such embodiments, the second heat-conducting element preferably overlies directly on and completely covers the first heat-conducting element.

[0091] In alternative embodiments, the second heat-conducting element overlies at least a portion of the first heat-conducting element, but may extend beyond the first heat-conducting element in an upstream direction, or a downstream direction, or both upstream and downstream directions.

[0092] Alternatively or where appropriate additionally, the first heat-conducting element may extend beyond the second heat-conducting element in the upstream direction, or in the downstream direction, or in both the upstream and downstream directions.

[0093] Preferably, the second heat-conducting element does not extend substantially beyond the first heat-conducting element in the upstream direction. The second heat-conducting element may extend in the upstream direction to substantially the same position on the combustible heat source as the first heat-conducting element, such that upstream ends of the first heat-conducting element and the second heat-conducting element are substantially aligned on the combustible heat source. Alternatively, the first heat-conducting element may extend beyond the second heat-conducting element in the upstream direction. Such an arrangement may reduce the temperature of the combustible heat source.

[0094] Preferably, the second heat-conducting element extends in the downstream direction to at least the same position as the first heat-conducting element. The second heat-conducting element may extend in the downstream direction to substantially the same position on the aerosol-forming substrate as the first heat-conducting element, such that downstream ends of the first heat-conducting element and the second heat-conducting element are substantially aligned on the aerosol-forming substrate. Alternatively, the second heat-conducting element may extend in the downstream direction beyond the first heat-conducting element, such that the second heat-conducting element surrounds a larger area of ​​the aerosol-forming substrate than the first heat-conducting element.

[0095] For example, the second heat-conducting element may extend beyond the first heat-conducting element by at least 1 mm in the downstream direction, or by at least 2 mm in the downstream direction.

[0096] In certain preferred embodiments, the second heat-conducting element overlies at least a portion of the first heat-conducting element and surrounds the entire length of the aerosol-forming substrate. In certain embodiments, the second heat-conducting element overlies at least a portion of the first heat-conducting element and extends beyond the aerosol-forming substrate in the downstream direction.

[0097] In other embodiments, the second heat-conducting element overlies at least a portion of the first heat-conducting element, but only surrounds a front portion of the aerosol-forming substrate.In such embodiments, the aerosol-forming substrate extends beyond the second heat-conducting element in the downstream direction.

[0098] It has surprisingly been found that the extent of the second heat-conducting element relative to the first heat-conducting element on the aerosol-forming substrate has a significant effect on the smoking performance of the smoking article.The coverage of the second heat-conducting element on the aerosol-forming substrate can therefore be adjusted to adjust the aerosol delivery profile of the smoking article.

[0099] In particular, it has been found that when the second heat-conducting element overlies at least a portion of the first heat-conducting element and extends beyond the first heat-conducting element in the downstream direction, a more consistent puff-by-puff aerosol delivery is provided during smoking. In particular, it has been found that aerosol delivery during medium puffs is reduced, thereby reducing the intensity of the puff during these puffs so as to make it more consistent in intensity during the initial puff and the final puff. It has also been found that the duration of the puff is also increased.

[0100] When the second heat-conducting element overlies at least a portion of the first heat-conducting element and extends downstream over the aerosol-forming substrate beyond the first heat-conducting element, a larger area of ​​the aerosol-forming substrate is covered by the second heat-conducting element. Heat is therefore dispersed through a larger volume of the aerosol-forming substrate, so that there is less temperature difference between different parts of the aerosol-forming substrate. This results in a decrease in the temperature of the front of the aerosol-forming substrate and an increase in the temperature of the rear of the aerosol-forming substrate. This is believed to be responsible for the observed effect on aerosol delivery between puffs.

[0101] As used herein, the term "puff-to-puff aerosol delivery" refers to the aerosol amount curve delivered to the user during each puff. For the common smoking article of heating, the aerosol delivery curve between puffs takes the form of a bell curve, wherein before reducing again toward the final puff, the aerosol amount delivered to the user increases toward the middle puff. The aerosol delivery between puffs can be adjusted so that the actual aerosol amount delivered to the user in each puff is modified. Alternatively or additionally, the relative delivery amount of the aerosol delivered to the user in each puff changes so that the shape of the aerosol delivery curve between puffs changes.

[0102] Smoking articles according to the invention comprise one or more first air inlets around the periphery of the aerosol-forming substrate.

[0103] It has surprisingly been found that, in combination with a second heat-conducting element, including one or more first air inlets around the periphery of the aerosol-forming substrate advantageously increases the aerosol delivery of the smoking article.

[0104] In use, cool air is drawn into the aerosol-forming substrate of the smoking article through the first air inlet.Air drawn into the aerosol-forming substrate through the first air inlet passes through the smoking article, passes downstream from the aerosol-forming substrate, and exits the smoking article through its proximal end.

[0105] During puffing by a user, the cool air drawn through the one or more first air inlets around the periphery of the aerosol-forming substrate advantageously reduces the temperature of the aerosol-forming substrate of the smoking article according to the invention. This advantageously substantially prevents or prevents peaks in the temperature of the aerosol-forming substrate of the smoking article according to the invention during puffing by a user.

[0106] As used herein, the term 'cold air' is used to describe ambient air that is not appreciably heated by a combustible heat source when puffed upon by a user.

[0107] By preventing or preventing the peak of the temperature of the aerosol-forming substrate, including one or more first air inlets around the periphery of the aerosol-forming substrate advantageously helps to avoid or mitigate the combustion or pyrolysis of the aerosol-forming substrate of the smoking article according to the present invention under intense single-puff puffing. In addition, including one or more first air inlets around the periphery of the aerosol-forming substrate advantageously helps to minimize or mitigate the influence of the user's single-puff puffing state on the composition of the mainstream aerosol of the smoking article according to the present invention.

[0108] The number, shape, size and position of the first air inlet can be properly adjusted to obtain good smoking performance.

[0109] In certain preferred embodiments, the one or more first air inlets are located close to the downstream end of the aerosol-forming substrate.

[0110] In certain embodiments, the aerosol-forming substrate may abut a rear face of the combustible heat source.

[0111] As used herein, the term 'adjacent' is used to describe the aerosol-forming substrate being in direct contact with the rear face of the combustible heat source, or a non-combustible substantially air impermeable barrier coating being provided on the rear face of the combustible heat source.

[0112] In other embodiments, the aerosol-forming substrate may be spaced apart from the rear face of the combustible heat source. That is, there may be a space or gap between the aerosol-forming substrate and the rear face of the combustible heat source.

[0113] In such embodiments, the smoking article according to the invention may further comprise one or more second air inlets between the rear of the combustible heat source and the aerosol-forming substrate. In use, cool air is drawn into the space between the combustible heat source and the aerosol-forming substrate through the second air inlet. The air drawn into the space between the combustible heat source and the aerosol-forming substrate through the second air inlet passes through the smoking article, passes downstream from the space between the combustible heat source and the aerosol-forming substrate, and exits the smoking article through its proximal end.

[0114] During puffing by a user, cool air drawn through one or more second inlets between the rear face of the combustible heat source and the aerosol-forming substrate may also advantageously reduce the temperature of the aerosol-forming substrate of a smoking article according to the invention. This may advantageously substantially prevent or prevent peaks in the temperature of the aerosol-forming substrate of a smoking article according to the invention during puffing by a user.

[0115] Alternatively, or additionally, smoking articles according to the invention may further comprise one or more third air inlets downstream of the aerosol-forming substrate.

[0116] It should be understood that the smoking article according to the present invention may include one or more first air inlets around the periphery of the aerosol-forming substrate and one or more second air inlets between the rear of the combustible heat source and the aerosol-forming substrate, or one or more first air inlets around the periphery of the aerosol-forming substrate and one or more third air inlets downstream of the aerosol-forming substrate, or one or more first air inlets around the periphery of the aerosol-forming substrate and one or more second air inlets between the rear of the combustible heat source and the aerosol-forming substrate, and one or more third air inlets downstream of the aerosol-forming substrate.

[0117] Smoking articles according to the invention may further comprise a non-combustible, substantially air-impermeable first barrier between the rear face of the combustible heat source and the aerosol-forming substrate.

[0118] As used herein, the term 'non-combustible' is used to describe a barrier that is substantially non-combustible at the temperatures reached by the combustible heat source during combustion and ignition of the combustible heat source.

[0119] The first barrier may abut one or both of the rear face of the combustible heat source and the aerosol-forming substrate. Alternatively, the first barrier may be spaced apart from one or both of the rear face of the combustible heat source and the aerosol-forming substrate.

[0120] The first barrier may be bonded or otherwise secured to one or both of the rear face of the combustible heat source and the aerosol-forming substrate.

[0121] In certain preferred embodiments, the first barrier comprises a non-combustible substantially air impermeable first barrier coating provided on the rear face of the combustible heat source. In such embodiments, preferably the first barrier comprises the first barrier coating provided on at least substantially the entire rear face of the combustible heat source. More preferably, the first barrier comprises the first barrier coating provided on the entire rear face of the combustible heat source.

[0122] As used herein, the term 'coating' is used to describe the layer of material covering and bonded to the combustible heat source.

[0123] The first barrier may advantageously limit the temperature to which the aerosol-forming substrate is exposed during ignition and combustion of the combustible heat source, and thus help avoid or mitigate thermal degradation or combustion of the aerosol-forming substrate during use of the smoking article. This is particularly advantageous where the combustible heat source comprises one or more additives to assist in ignition of the combustible heat source.

[0124] The inclusion of a non-combustible substantially air impermeable first barrier between the rear face of the combustible heat source and the aerosol-forming substrate may also advantageously substantially prevent or inhibit migration of components of the aerosol-forming substrate of smoking articles according to the invention to the combustible heat source during storage of the smoking article.

[0125] Alternatively or additionally, including a non-combustible substantially air impermeable first barrier between the rear face of the combustible heat source and the aerosol-forming substrate may advantageously substantially prevent or inhibit migration of components of the aerosol-forming substrate of smoking articles according to the invention to the combustible heat source during use of the smoking article.

[0126] It may be particularly advantageous to include a non-combustible substantially air impermeable first barrier between the rear face of the combustible heat source and the aerosol-forming substrate when the aerosol-forming substrate comprises at least one aerosol former.

[0127] In such embodiments, the inclusion of a non-combustible substantially air-impermeable first barrier between the rear face of the combustible heat source and the aerosol-forming substrate can advantageously prevent or inhibit migration of at least one aerosol-forming agent from the aerosol-forming substrate to the combustible heat source during storage and use of the smoking article. Decomposition of the at least one aerosol-forming agent can therefore advantageously be substantially avoided or reduced during use of the smoking article.

[0128] Depending on the desired features and performance of the smoking article, the first barrier may have a low thermal conductivity or a high thermal conductivity. In certain embodiments, the first barrier is formed of a material having an overall thermal conductivity of about 0.1 Watts per meter Kelvin (W / (m·K)) to about 200 Watts per meter Kelvin (W / (m·K)) at 23°C and 50% relative humidity as measured using a modified transient planar thermal source (MTPS) method.

[0129] The thickness of the first barrier may be appropriately adjusted to obtain good smoking performance. In certain embodiments, the first barrier may have a thickness of about 10 microns to about 500 microns.

[0130] The first barrier may be formed of one or more suitable materials that are substantially thermally stable and non-combustible at the temperatures obtained by the combustible heat source during ignition and combustion. Suitable materials are known in the art and include, but are not limited to, clays (e.g., bentonite and kaolinite), glasses, minerals, ceramic materials, resins, metals, and combinations thereof.

[0131] Preferred materials for forming the first barrier include clay and glass. More preferred materials for forming the first barrier include copper, aluminum, stainless steel, alloys, aluminum oxide (Al 2 O 3 ), resins and mineral glues.

[0132] In certain preferred embodiments, the first barrier comprises a clay coating provided on the rear face of the combustible heat source, the clay coating comprising a 50 / 50 mixture of bentonite and kaolinite. In other preferred embodiments, the first barrier comprises a glass coating, more preferably a sintered glass coating, provided on the rear face of the combustible heat source.

[0133] In certain particularly preferred embodiments, the first barrier comprises an aluminium coating provided on the rear face of the combustible heat source.

[0134] Preferably, the first barrier has a thickness of at least about 10 microns.

[0135] Due to the slight air permeability of clay, in embodiments where the first barrier comprises a clay coating disposed on the rear face of the combustible heat source, the clay coating more preferably has a thickness of at least about 50 microns, most preferably from about 50 microns to about 350 microns.

[0136] In embodiments where the first barrier is formed from a less gas impermeable material or materials (eg, aluminum), the first barrier may be thinner, and generally preferably has a thickness of less than about 100 microns, more preferably about 20 microns.

[0137] In embodiments where the first barrier comprises a glass coating provided on the rear face of the combustible heat source, the glass coating preferably has a thickness of less than about 200 micrometres.

[0138] The thickness of the first barrier may be measured using a microscope, a scanning electron microscope (SEM), or any other suitable measurement method known in the art.

[0139] When the first barrier comprises a first barrier coating disposed on the rear face of the combustible heat source, the first barrier coating may be applied to cover and adhere to the rear face of the combustible heat source by any suitable method known in the art including, but not limited to, spraying, vapor deposition, dipping, material transfer (e.g., brushing or gluing), electrostatic deposition, or any combination thereof.

[0140] For example, the first barrier coating may be made by preforming a barrier member to a size and shape approximating the rear face of the combustible heat source, and applying the barrier member to the rear face of the combustible heat source so as to cover and adhere to at least substantially the entire rear face of the combustible heat source. Alternatively, the first barrier coating may be cut or machined after it is applied to the rear face of the combustible heat source. In a preferred embodiment, aluminium foil is applied to the rear face of the combustible heat source by gluing or pressing aluminium foil to the combustible heat source, and cutting or machining the aluminium foil so that it covers and adheres to at least substantially the entire rear face of the combustible heat source, preferably the entire rear face of the combustible heat source.

[0141] In another preferred embodiment, the first barrier coating is formed by applying a solution or suspension of one or more suitable coating materials to the rear face of the combustible heat source. For example, the first barrier coating may be applied to the rear face of the combustible heat source by dipping the rear face of the combustible heat source into a solution or suspension of one or more suitable coating materials, by brushing or spraying the solution or suspension onto the rear face of the combustible heat source, or by electrostatically depositing a powder or powder mixture of one or more suitable coating materials onto the rear face of the combustible heat source. When the first barrier coating is applied to the rear face of the combustible heat source by electrostatically depositing a powder or powder mixture of one or more suitable coating materials onto the rear face of the combustible heat source, the rear face of the combustible heat source is preferably pre-treated with waterglass prior to electrostatic deposition. Preferably, the first barrier coating is applied by spraying.

[0142] The first barrier coating may be formed by a single application of a solution or suspension of one or more suitable coating materials to the rear face of the combustible heat source. Alternatively, the first barrier coating may be formed by multiple applications of a solution or suspension of one or more suitable coating materials to the rear face of the combustible heat source. For example, the first barrier coating may be formed by one, two, three, four, five, six, seven or eight consecutive applications of a solution or suspension of one or more suitable coating materials to the rear face of the combustible heat source.

[0143] Preferably, the first barrier coating is formed by applying from one to ten applications of a solution or suspension of one or more suitable coating materials to the rear face of the combustible heat source.

[0144] After applying the solution or suspension of one or more coating materials to the rear face of the combustible heat source, the combustible heat source may be dried to form the first barrier coating.

[0145] When the first barrier coating is formed by multiple applications of a solution or suspension of one or more suitable coating materials to the rear face of the combustible heat source, the combustible heat source may require drying between successive applications of the solution or suspension.

[0146] Alternatively or additionally to drying, after applying the solution or suspension of one or more coating materials to the rear face of the combustible heat source, the coating material on the combustible heat source may be sintered to form the first barrier coating. Sintering of the first barrier coating is particularly preferred when the first barrier coating is a glass or ceramic coating. Preferably, the first barrier coating is sintered at a temperature of about 500°C to about 900°C, more preferably at a temperature of about 700°C.

[0147] Smoking articles according to the invention may comprise a non-blind combustible heat source.As used herein, the term 'non-blind' is used to describe a combustible heat source comprising at least one airflow channel extending from a front face of the combustible heat source to a rear face of the combustible heat source.

[0148] As used herein, the term 'airflow channel' is used to describe a channel extending along the length of the combustible heat source through which air may be drawn downstream for inhalation by a user.

[0149] In smoking articles according to the invention comprising a non-blind combustible heat source, heating of the aerosol-forming substrate occurs by conduction and forced convection.

[0150] The one or more air flow channels may include one or more closed air flow channels.

[0151] As used herein, the term 'enclosed' is used to describe an airflow passage extending through the interior of a non-blind combustible heat source and surrounded by the non-blind combustible heat source.

[0152] Alternatively or additionally, the one or more airflow channels may comprise one or more non-enclosed airflow channels. For example, the one or more airflow channels may comprise one or more grooves or other non-enclosed airflow channels extending along the exterior of the non-blind combustible heat source.

[0153] The one or more air flow channels may include one or more enclosed air flow channels or one or more non-enclosed air flow channels or a combination thereof.

[0154] In certain embodiments, smoking articles according to the invention comprise one, two or three airflow channels extending from a front face of the non-blind combustible heat source to a rear face of the non-blind combustible heat source.

[0155] In certain preferred embodiments, smoking articles according to the invention comprise a single airflow channel extending from a front face of the non-blind combustible heat source to a rear face of the non-blind combustible heat source.

[0156] In certain particularly preferred embodiments, smoking articles according to the invention comprise a single substantially central or axial airflow channel extending from a front face of the non-blind combustible heat source to a rear face of the non-blind combustible heat source.

[0157] In such embodiments, the diameter of a single airflow channel is preferably from about 1.5 mm to about 3 mm.

[0158] It will be appreciated that in addition to one or more airflow channels through which air can be drawn for inhalation by a user, smoking articles according to the present invention may comprise a non-blind combustible heat source comprising one or more closed or blocked passages through which air cannot be drawn for inhalation by a user.

[0159] For example, smoking articles according to the present invention may comprise a non-blind combustible heat source comprising one or more airflow channels extending from a front face of the combustible heat source to a rear face of the combustible heat source, and one or more closed passages extending from the front face of the non-blind combustible heat source along only a portion of the length of the combustible heat source.

[0160] The inclusion of one or more closed air passages increases the surface area of ​​the non-blind combustible heat source that is exposed to oxygen from the air and may advantageously facilitate ignition and sustained combustion of the non-blind combustible heat source.

[0161] When a smoking article according to the present invention comprises a non-blind combustible heat source and a non-combustible substantially air-impermeable first barrier between the rear of the combustible heat source and the aerosol-forming substrate, the first barrier should allow air to enter the smoking article through one or more airflow channels to be drawn downstream through the smoking article.

[0162] Alternatively or additionally to a non-combustible, substantially air-impermeable first barrier between the rear of the combustible heat source and the aerosol-forming substrate, a smoking article according to the present invention comprising a non-blind combustible heat source may comprise a non-combustible, substantially air-impermeable second barrier between the non-blind combustible heat source and one or more airflow channels.

[0163] The second barrier may advantageously substantially prevent or inhibit combustion and decomposition products formed during ignition and combustion of the non-blind combustible heat source from entering air drawn into the smoking article according to the invention through the one or more airflow channels as the air being drawn passes through the one or more airflow channels. This is particularly advantageous when the non-blind combustible heat source includes one or more additives to aid ignition or combustion of the non-blind combustible heat source.

[0164] The inclusion of a non-combustible substantially air-impermeable second barrier between the non-blind combustible heat source and the one or more airflow channels may also advantageously substantially prevent or inhibit initiation of combustion of the non-blind combustible heat source during puffing by a user. This may substantially prevent or inhibit peaks in the temperature of the aerosol-forming substrate during puffing by a user.

[0165] By preventing or preventing the initiation of combustion of the non-blind combustible heat source, and thereby preventing or preventing excessive temperature rise in the aerosol-forming substrate, combustion or pyrolysis of the aerosol-forming substrate during intense puffing may be advantageously avoided. In addition, the effect of the user's puffing state on the composition of the mainstream aerosol may advantageously be minimized or mitigated.

[0166] The second barrier may be bonded or otherwise secured to the non-blind combustible heat source.

[0167] In certain preferred embodiments, the second barrier comprises a non-flammable substantially air-impermeable second barrier coating disposed on the inner surface of the one or more airflow channels. In such embodiments, preferably the second barrier comprises a second barrier coating disposed on at least substantially the entire inner surface of the one or more airflow channels. More preferably, the second barrier comprises a second barrier coating disposed on the entire inner surface of the one or more airflow channels.

[0168] In other embodiments, the second barrier coating may be provided by inserting a liner into one or more airflow channels. For example, when the one or more airflow channels include one or more enclosed airflow channels extending through the interior of the non-blind combustible heat source, a non-combustible substantially air impermeable hollow tube may be inserted into each of the one or more airflow channels.

[0169] Depending on the desired features and performance of the smoking article, the second barrier may have a low thermal conductivity or a high thermal conductivity.Preferably, the second barrier has a low thermal conductivity.

[0170] The thickness of the second barrier can be appropriately adjusted to obtain good smoking performance. In certain embodiments, the second barrier can have a thickness of about 30 microns to about 200 microns. In a preferred embodiment, the second barrier has a thickness of about 30 microns to about 100 microns.

[0171] The first barrier may be formed of one or more suitable materials that are substantially thermally stable and non-combustible at the temperatures obtained by the non-blind combustible heat source during ignition and combustion. Suitable materials are known in the art and include, but are not limited to, for example: clays; metal oxides such as iron oxide, aluminum oxide, titanium dioxide, silicon oxide, silicon oxide-alumina, zirconium oxide, and cerium oxide; zeolites; zirconium phosphates; and other ceramic materials or combinations thereof.

[0172] Preferred materials from which the second barrier may be formed include clay, glass, aluminum, iron oxide, and combinations thereof. If desired, a catalytic component, such as a component that promotes the oxidation of carbon monoxide to carbon dioxide, may be incorporated into the second barrier. Suitable catalytic components include, but are not limited to, platinum, palladium, transition metals, and oxides thereof.

[0173] Where the second barrier comprises a second barrier coating disposed on the inner surface of the one or more gas flow channels, the second barrier coating may be applied to the inner surface of the one or more gas flow channels by any suitable method, such as the method described in US-A-5,040,551. For example, the inner surface of the one or more gas flow channels may be sprayed, wetted or coated with a solution or suspension of the second barrier coating. In certain preferred embodiments, the second barrier coating is applied to the inner surface of the one or more gas flow channels by the process described in WO-A2-2009 / 074870 as the combustible heat source is extruded.

[0174] Alternatively, smoking articles according to the invention may comprise a blind combustible heat source.As used herein, the term 'blind' is used to describe a combustible heat source that does not comprise any airflow channels extending from a front face of the combustible heat source to a rear face of the combustible heat source.

[0175] In use, air drawn through a smoking article according to the invention comprising a blind combustible heat source for inhalation by a user does not pass through any airflow passages along the blind combustible heat source. The lack of any airflow passages through the blind combustible heat source advantageously substantially prevents or inhibits the initiation of combustion of the blind combustible carbonaceous heat source during puffing by a user. This substantially prevents or inhibits peaks in the temperature of the aerosol-forming substrate during puffing by a user.

[0176] By preventing or preventing the initiation of combustion of the blind combustible heat source, and thereby preventing or preventing excessive temperature rise in the aerosol-forming substrate, combustion or pyrolysis of the aerosol-forming substrate during intense puffing conditions can be advantageously avoided. In addition, the effect of the user's puffing condition on the composition of the mainstream aerosol can advantageously be minimized or mitigated.

[0177] The inclusion of a blind combustible heat source may also advantageously substantially prevent or inhibit combustion and decomposition products and other materials formed during ignition and combustion of the blind combustible heat source from entering air drawn through it during use of smoking articles according to the invention. This is particularly advantageous when the blind combustible heat source includes one or more additives to assist in the ignition or combustion of the blind combustible heat source.

[0178] In smoking articles according to the invention comprising a blind combustible heat source, heat transfer from the blind combustible heat source to the aerosol-forming substrate occurs primarily by conduction, and heating of the aerosol-forming substrate by forced conduction is minimized or mitigated. This can advantageously help minimize or mitigate the effect of a user's puffing regime on the composition of the mainstream aerosol of smoking articles according to the invention.

[0179] In smoking articles according to the invention comprising a blind combustible heat source, it is particularly important to optimise conductive heat transfer between the combustible heat source and the aerosol-forming substrate. The inclusion of a second heat-conducting element has been found to have a particularly beneficial effect on the smoking performance of smoking articles comprising a blind heat source in which there is little, if any, heating of the aerosol-forming substrate by forced convection.

[0180] It will be appreciated that smoking articles according to the invention may comprise a blind combustible heat source comprising one or more closed or blocked passageways through which air cannot be drawn for inhalation by a user.

[0181] For example, smoking articles according to the invention may comprise a blind combustible heat source comprising one or more closed passageways extending only part way along the length of the blind combustible heat source from a front face of an upstream end of the blind combustible heat source.

[0182] The inclusion of one or more closed air passages increases the surface area of ​​the blind combustible heat source that is exposed to oxygen from the air and may advantageously facilitate ignition and sustained combustion of the blind combustible heat source.

[0183] Preferably, the combustible heat source is a carbonaceous heat source. As used herein, the term 'carbonaceous' is used to describe a combustible heat source that contains carbon. Preferably, the combustible carbonaceous heat source used in smoking articles according to the present invention has a carbon content of at least about 35%, more preferably at least about 40%, most preferably at least about 45%, based on the dry weight of the combustible heat source.

[0184] In some embodiments, the combustible heat source according to the present invention is a combustible carbon-based heat source.As used herein, the term 'carbon-based heat source' is used to describe a heat source consisting primarily of carbon.

[0185] The combustible carbon-based heat source used in the smoking article according to the present invention has a carbon content of at least about 50%. For example, the combustible carbon-based heat source used in the smoking article according to the present invention can have a carbon content of at least about 60%, or at least about 70%, or at least about 80%, based on the dry weight of the combustible carbon-based heat source.

[0186] Smoking articles according to the invention may comprise a combustible carbonaceous heat source formed from one or more suitable carbonaceous materials.

[0187] If desired, one or more binders may be combined with one or more carbonaceous materials. Preferably, one or more binders are organic binders. Suitable known organic binders include, but are not limited to, gums (e.g., guar gum), modified celluloses and cellulose derivatives (e.g., methylcellulose, carboxymethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose), flours, starches, sugars, vegetable oils and combinations thereof.

[0188] In a preferred embodiment, the combustible carbonaceous heat source is formed from a mixture of carbon powder, modified cellulose, flour and sugar.

[0189] Instead of one or more binders or in addition to one or more binders, the combustible heat source used in the smoking article according to the present invention may contain one or more additives to improve the properties of the combustible heat source. Suitable additives include, but are not limited to, additives to promote the consolidation of the combustible heat source (e.g., sintering aids), additives to promote the ignition of the combustible heat source (e.g., oxidizers, such as perchlorates, chlorates, nitrates, peroxides, permanganates, zirconium, and combinations thereof), additives to promote the combustion of the combustible heat source (e.g., potassium and potassium salts, such as potassium citrate), and additives to promote the decomposition of one or more gases produced by the combustion of the combustible heat source (e.g., catalysts, such as CuO, Fe 2 O 3 and Al 2 O 3 ).

[0190] When smoking articles according to the invention comprise a first barrier coating provided on the rear face of the combustible heat source, such additives may be incorporated into the combustible heat source either before or after the first barrier coating is applied to the rear face of the combustible heat source.

[0191] In certain preferred embodiments, the combustible heat source is a combustible carbonaceous heat source comprising carbon and at least one ignition aid.In a preferred embodiment, the combustible heat source is a combustible carbonaceous heat source comprising carbon and at least one ignition aid as described in WO-A1-2012 / 164077.

[0192] As used herein, the term 'ignition aid' is used to refer to a material that releases one or both of energy and oxygen during ignition of a combustible heat source, wherein the rate at which the material releases one or both of energy and oxygen is not limited by the diffusion of ambient oxygen. In other words, the rate at which the material releases one or both of energy and oxygen during ignition of the combustible heat source is largely independent of the rate at which ambient oxygen can reach the material. As used herein, the term 'ignition aid' is also used to refer to an elemental metal that releases energy during ignition of a combustible heat source, wherein the ignition temperature of the elemental metal is below about 500°C and the heat of combustion of the elemental metal is at least about 5 kJ / g.

[0193] As used herein, the term 'ignition aid' does not include alkali metal salts of carboxylic acids (such as alkali metal citrates, alkali metal acetates and alkali metal succinates), alkali metal halide salts (such as alkali metal chloride salts), alkali metal carbonates or alkali metal phosphates, which are believed to modify carbon combustion. Even when the alkali metal combustion salt is present in a large amount relative to the total weight of the combustible heat source, such alkali metal combustion salts do not release sufficient energy during the ignition of the combustible heat source to produce an acceptable aerosol during the early single puff process.

[0194] Examples of suitable oxidizing agents include, but are not limited to, nitrates such as potassium nitrate, calcium nitrate, strontium nitrate, sodium nitrate, barium nitrate, lithium nitrate, aluminum nitrate, and ferric nitrate; nitrites; other organic and inorganic nitro compounds; chlorates such as sodium chlorate and potassium chlorate; perchlorates such as sodium perchlorate; chlorites; bromates such as sodium bromate and potassium bromate; perbromates; bromites; borates such as sodium borate and potassium borate; ferrates such as barium ferrate; ferrates; manganates such as potassium manganate; permanganates such as potassium permanganate; organic peroxides such as benzoyl peroxide and acetone peroxide; inorganic peroxides such as hydrogen peroxide, strontium peroxide, magnesium peroxide, calcium peroxide, barium peroxide, zinc peroxide, and lithium peroxide; superoxides such as potassium superoxide and sodium superoxide; iodates; periodates; iodites; sulfates; sulfites; other sulfoxides; phosphates; phosphinates; phosphites; and phosphanites.

[0195] Although advantageously improving the ignition and combustion properties of a combustible heat source, the inclusion of ignition and combustion additives may result in undesirable decomposition and reaction products during use of the smoking article. For example, the decomposition of nitrates included in a combustible heat source to assist its ignition may result in the formation of nitrogen oxides.

[0196] The inclusion of a non-combustible, substantially air impermeable first barrier between the rear face of the combustible heat source and the aerosol-forming substrate may advantageously substantially prevent or inhibit such decomposition and reaction products from entering air drawn through smoking articles according to the invention.

[0197] When smoking articles according to the present invention include a non-blind combustible heat source, including a non-combustible, substantially air-impermeable second barrier between one or more airflow channels and the non-blind combustible heat source can advantageously substantially prevent or inhibit such decomposition and reaction products from entering the air drawn into the smoking article according to the present invention through the one or more airflow channels as the air drawn through the one or more airflow channels.

[0198] Combustible carbonaceous heat sources for use in smoking articles according to the present invention may be prepared as described in the prior art known to those of ordinary skill in the art.

[0199] The combustible carbonaceous heat source for smoking articles according to the present invention is preferably formed by mixing one or more carbonaceous materials with one or more binders and other additives, if any, and preforming the mixture into a desired shape. The mixture of one or more carbonaceous materials, one or more binders and optional other additives can be preformed into a desired shape using any suitable known ceramic forming method, such as, for example, slip casting, extrusion, injection molding and mold compression molding or pressing. In certain preferred embodiments, the mixture is preformed into a desired shape by pressing or extrusion or a combination thereof.

[0200] Preferably, the mixture of one or more carbonaceous materials, one or more binders and other additives is preformed into an elongated rod. However, it should be understood that the one or more carbonaceous materials, one or more binders and other additives can be preformed into other desired shapes.

[0201] After forming, particularly after extrusion, the elongated rod or other desired shape is preferably dried to reduce its moisture content and then pyrolyzed in a non-oxidizing atmosphere at a temperature sufficient to carbonize the one or more binders, if present, and substantially eliminate any volatiles in the elongated rod or other shape. The elongated rod or other desired shape is preferably pyrolyzed in a nitrogen atmosphere at a temperature of about 700° C. to about 900° C.

[0202] In certain embodiments, at least one metal nitrate is incorporated into the combustible heat source by including at least one metal nitrate precursor in a mixture of one or more carbonaceous materials, one or more binders, and other additives. The at least one metal nitrate precursor is then converted in situ to the at least one metal nitrate by treating the pyrolyzed preformed cylindrical rod or other shape with an aqueous solution of nitric acid. In one embodiment, the combustible heat source includes at least one metal nitrate, the at least one metal nitrate having a thermal decomposition temperature of less than about 600°C, more preferably less than about 400°C. Preferably, the at least one metal nitrate has a decomposition temperature of about 150°C to about 600°C, more preferably about 200°C to about 400°C.

[0203] In a preferred embodiment, exposure of the combustible heat source to a conventional yellow flame igniter or other ignition device should cause the at least one metal nitrate to decompose and release oxygen and energy. This decomposition causes an initial increase in the temperature of the combustible heat source and also aids in ignition of the combustible heat source. After decomposition of the at least one metal nitrate, the combustible heat source preferably continues to burn at a lower temperature.

[0204] Inclusion of at least one metal nitrate advantageously causes ignition of the combustible heat source to be triggered internally, rather than just at a point on its surface. Preferably, the at least one metal nitrate is present in the combustible heat source in an amount of about 20% by dry weight of the combustible heat source to about 50% by dry weight of the combustible heat source.

[0205] In other embodiments, the combustible heat source comprises at least one peroxide or superoxide that actively derivatizes oxygen at a temperature of less than about 600°C, more preferably at a temperature of less than about 400°C.

[0206] Preferably, the at least one peroxide or superoxide actively derivatizes oxygen at a temperature of about 150°C to about 600°C, more preferably at a temperature of about 200°C to about 400°C, and most preferably at a temperature of about 350°C.

[0207] In use, exposure of the combustible heat source to a conventional yellow flame igniter or other ignition device should cause the at least one peroxide or superoxide to decompose and release oxygen. This causes an initial increase in the temperature of the combustible heat source and also assists in ignition of the combustible heat source. After decomposition of the at least one peroxide or superoxide, the combustible heat source preferably continues to burn at a lower temperature.

[0208] The inclusion of at least one peroxide or superoxide advantageously causes ignition of the combustible heat source to be triggered internally, rather than merely at a point on its surface.

[0209] The combustible heat source preferably has a porosity of about 20% to about 80%, more preferably about 20% to 60%. Where the combustible heat source comprises at least one metal nitrate, this advantageously allows oxygen to diffuse into the mass of the combustible heat source at a rate sufficient to sustain combustion as the at least one metal nitrate decomposes and combustion proceeds. Even more preferably, the combustible heat source has a porosity of about 50% to about 70%, more preferably about 50% to about 60%, as measured by, for example, mercury porosimetry or helium pycnometry. The desired porosity can be readily achieved during the production of the combustible heat source using conventional methods and techniques.

[0210] Advantageously, the combustible carbonaceous heat source for use in smoking articles according to the present invention has a carbon content of about 0.6 g / cm 3 About 1g / cm 3 The apparent density of .

[0211] Preferably, the combustible heat source has a mass of from about 300 mg to about 500 mg, more preferably from about 400 mg to about 450 mg.

[0212] Preferably, the combustible heat source has a length of from about 7 mm to about 17 mm, more preferably from about 7 mm to about 15 mm, most preferably from about 7 mm to about 13 mm.

[0213] Preferably, the combustible heat source has a diameter of about 5 mm to about 9 mm, more preferably about 7 mm to about 8 mm.

[0214] Preferably, the combustible heat source has a substantially uniform diameter. However, the combustible heat source may alternatively be tapered so that the diameter of the rear portion of the closed combustible heat source is greater than the diameter of the front portion thereof. Particularly preferred are substantially cylindrical combustible heat sources. The combustible heat source may, for example, be a cylinder or a tapered cylinder having a substantially circular cross-section, or a cylinder or a tapered cylinder having a substantially elliptical cross-section.

[0215] Smoking articles according to the invention preferably comprise an aerosol-forming substrate comprising at least one aerosol former and a material capable of releasing volatile compounds in response to heating. The aerosol former may comprise other additives and ingredients, including but not limited to humectants, flavorings, binders and mixtures thereof.

[0216] Preferably, the aerosol-forming substrate comprises nicotine. More preferably, the aerosol-forming substrate comprises tobacco.

[0217] At least one aerosol former may be any suitable known compound or mixture of compounds, which facilitates the formation of a dense and stable aerosol in use and substantially resists thermal degradation at the operating temperature of the smoking article. Suitable aerosol formers are well known in the art and include, for example, polyols, esters of polyols (monoacetin, diacetin or triacetin), and aliphatic esters of monocarboxylic acids, dicarboxylic acids or polycarboxylic acids (e.g. dimethyl dodecanedioate and dimethyl tetradecanedioate). Preferred aerosol formers for smoking articles according to the present invention are polyols or mixtures thereof, such as triethylene glycol, 1,3-butylene glycol, most preferably glycerol.

[0218] The material capable of emitting volatile compounds in response to heating may be a plant-based filler material. The material capable of emitting volatile compounds in response to heating may be a plant-based homogenous filler material. For example, the aerosol-forming substrate may comprise one or more materials derived from plants including, but not limited to: tobacco; tea leaves, such as green tea; mint; laurel; eucalyptus; basil; sage; verbena; and tarragon.

[0219] Preferably, the material capable of evolving volatile compounds in response to heating may be a tobacco based filler material, most preferably a tobacco based homogenous filler material.

[0220] The aerosol-forming substrate may take the form of a formed piece or segment surrounded by paper or other wrappers, the formed piece or segment comprising a material capable of emitting volatile compounds in response to heating. As described above, when the aerosol-forming substrate takes the form of such a formed piece or segment, the entire formed piece or segment including any wrappers is considered to be an aerosol-forming substrate.

[0221] Preferably, the aerosol-forming substrate has a length of from about 5 mm to about 20 mm, more preferably from about 8 mm to about 12 mm.

[0222] In preferred embodiments, the aerosol-forming substrate comprises a plug of tobacco-based material wrapped in a plug wrap.In particularly preferred embodiments, the aerosol-forming substrate comprises a plug of homogenised tobacco-based material wrapped in a plug wrap.

[0223] Smoking articles according to the invention preferably comprise a mouthpiece downstream of the aerosol-forming substrate.The mouthpiece is located at the proximal end of the smoking article.

[0224] Preferably, the mouthpiece has a low filtration efficiency, more preferably a very low filtration efficiency. The mouthpiece may be a single segment or component mouthpiece. Alternatively, the mouthpiece may be a multi-segment mouthpiece or a multi-component mouthpiece.

[0225] The mouthpiece may include a filter comprising one or more segments comprising suitable known filter materials. Suitable filter materials are known in the art and include, but are not limited to, cellulose acetate and paper. Alternatively or additionally, the mouthpiece may include one or more segments comprising absorbents, adsorbents, flavoring agents, and other aerosol modifiers and additives or combinations thereof.

[0226] Smoking articles according to the invention preferably further comprise a transfer element or spacer element between the aerosol-forming substrate and the mouthpiece.

[0227] The transfer element may abut one or both of the aerosol-forming substrate and the mouthpiece. Alternatively, the transfer element may be spaced apart from one or both of the aerosol-forming substrate and the mouthpiece.

[0228] The inclusion of a transfer element advantageously allows cooling of the aerosol generated by heat transfer from the combustible heat source to the aerosol-forming substrate. The inclusion of a transfer element also advantageously allows the overall length of the smoking article according to the invention to be adjusted to a desired value, for example to a length similar to that of a conventional cigarette, by appropriate choice of the length of the transfer element.

[0229] The transfer element may have a length of about 7 mm to about 50 mm, for example about 10 mm to about 45 mm or about 15 mm to about 30 mm. The transfer element may have other lengths depending on the desired overall length of the smoking article, and the presence and length of other components within the smoking article.

[0230] Preferably, the transfer element comprises at least one open-ended tubular hollow body. In such embodiments, in use, when the inhaled air flows downstream from the aerosol-forming substrate through the smoking article to its proximal end, the air drawn through the smoking article passes through the at least one open-ended tubular hollow body.

[0231] The transfer element may comprise at least one open-ended tubular hollow body formed from one or more suitable materials that are substantially thermally stable at the temperature of the aerosol generated by heat transfer from the combustible heat source to the aerosol-forming substrate. Suitable materials are known in the art and include, but are not limited to, paper, paperboard, plastics such as cellulose acetate, ceramics, and combinations thereof.

[0232] Alternatively or additionally, smoking articles according to the invention may comprise an aerosol-cooling element or heat exchanger between the aerosol-forming substrate and the mouthpiece.The aerosol-cooling element may comprise a plurality of longitudinally extending channels.

[0233] The aerosol-cooling element may comprise a gathered sheet of material selected from metal foil, a polymeric material, and a substantially non-porous paper or paperboard. In certain embodiments, the aerosol-cooling element may comprise a gathered sheet of material selected from polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), cellulose acetate (CA), and aluminum foil.

[0234] In certain preferred embodiments, the aerosol-cooling element may comprise a gathered sheet of biodegradable polymeric material, such as polylactic acid (PLA) or (A commercially available series of starch-based copolyesters) grade.

[0235] Smoking articles according to the invention may comprise one or more aerosol modifying agents downstream of the aerosol-forming substrate.For example, one or more of the mouthpiece, transfer element and aerosol-cooling element of smoking articles according to the invention may comprise one or more aerosol modifying agents.

[0236] Suitable aerosol modifying agents include, but are not limited to: flavoring agents; and chemesthetic agents.

[0237] As used herein, the term 'flavorant' is used to describe any agent which, in use, imparts one or both of taste or aroma to the aerosol generated by the aerosol-forming substrate of a smoking article.

[0238] As used herein, the term 'chemical agent' is used to describe any agent that is sensed in the user's oral cavity or olfactory cavity in addition to or in addition to the perception of taste receptors or olfactory receptor cells during use. The perception of chemical agents is usually through "trigeminal induction", or through the trigeminal nerve, glossopharyngeal nerve, sympathetic nerve or some combination of these nerves. Typically, chemical agents are perceived as hot, spicy, cool or sedative sensations.

[0239] Smoking articles according to the invention may comprise one or more aerosol modifiers downstream of the aerosol-forming substrate, which are both flavoring agents and chemical agents. For example, one or more of the mouthpiece, transfer element and aerosol-cooling element of a smoking article according to the invention may comprise menthol or another flavoring agent that provides a cooling chemical effect.

[0240] Smoking articles according to the invention may be assembled using known methods and machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0241] The present invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

[0242] Figure 1 shows a schematic longitudinal cross-section of a smoking article according to an embodiment of the invention; and

[0243] Figure 2 Shows the Figure 1 Graph of total aerosol former and nicotine delivery for smoking articles according to embodiments of the invention shown in FIG. DETAILED DESCRIPTION

[0244] exist Figure 1 The smoking article 2 according to the first embodiment of the invention shown in Figure 1 comprises a blind combustible heat source 4 having a front face 6 and an opposed rear face 8, an aerosol-forming substrate 10, a transfer element 12, an aerosol-cooling element 14, a spacer element 16 and a mouthpiece 18 in adjacent coaxial alignment. Figure 1 As shown in the figure, the aerosol-forming substrate 10, the transfer element 12, the aerosol-cooling element 14, the spacer element 16 and the mouthpiece 18 and the rear part of the closed combustible heat source 4 are wrapped in an outer wrapper 20 of a sheet material with low air permeability, such as cigarette paper. It should be understood that in other embodiments of the invention (not shown), the outer wrapper 20 may be omitted.

[0245] The blind combustible heat source 4 is a blind carbonaceous combustible heat source and is located at the distal end of the smoking article 2. Figure 1, a non-combustible, substantially air impermeable first barrier 22 in the form of an aluminium foil disc is provided between the rear face 8 of the blind combustible heat source 4 and the aerosol-forming substrate 10. The first barrier 22 is applied to the rear face 8 of the blind combustible heat source 4 by pressing the aluminium foil disc onto the rear face 8 of the blind combustible heat source 4 and abuts the rear face 8 of the combustible carbonaceous heat source 4 and the aerosol-forming substrate 10.

[0246] The aerosol-forming substrate 10 is located immediately downstream of a first barrier 22 applied to the rear face 8 of the blind combustible heat source 4. The aerosol-forming substrate 10 comprises a cylindrical form of homogenised tobacco-based material 24 comprising an aerosol former, such as glycerine, enclosed within a form wrapper 26.

[0247] The transfer element 12 is located immediately downstream of the aerosol-forming substrate 10 and comprises a cylindrical open-ended hollow tube 28 of cellulose acetate.

[0248] Aerosol-cooling element 14 is located immediately downstream of transfer element 12 and comprises a gathered sheet of biodegradable polymer material, such as polylactic acid.

[0249] The spacer element 16 is located immediately downstream of the aerosol-cooling element 14 and comprises a cylindrical open-ended hollow tube 30 of paper or cardboard.

[0250] The mouthpiece 18 is located immediately downstream of the spacer element 16. Figure 1 As shown in , the mouthpiece 18 is located at the proximal end of the smoking article 2 and comprises a cylindrical molding having a suitable filter material 32 wrapped within a filter plug wrapper 34, such as cellulose acetate tow having very low filtration efficiency.

[0251] The smoking article may further comprise a band of filter paper (not shown) surrounding a downstream end portion of the outer wrapper 20 .

[0252] like Figure 1 As shown in , the smoking article 2 also includes a first heat-conducting element 36 of a suitable material, such as aluminium foil, surrounding and directly contacting the rear portion 4b of the blind combustible heat source 4 and the front portion 10a of the aerosol-forming substrate 10. Figure 1 In the smoking article 2 according to the first embodiment of the invention shown in , the aerosol-forming substrate 10 extends downstream beyond the first heat-conducting element 36. That is, the first heat-conducting element 36 does not surround and directly contact the rear portion of the aerosol-forming substrate 10. However, it will be appreciated that in other embodiments of the invention (not shown), the first heat-conducting element 36 may surround and contact the entire length of the aerosol-forming substrate 10.

[0253] like Figure 1As shown in , the smoking article 2 further comprises a second heat-conducting element 38 which surrounds the rear portion of the blind combustible heat source 4, the entire length of the aerosol-forming substrate 10 and the entire length of the transfer element 12. Figure 1 In the smoking article 2 according to the first embodiment of the invention shown in , the second heat-conducting element 34 extends in the upstream direction to substantially the same position on the blind combustible heat source 4 as the first heat-conducting element 36, so that the upstream ends of the first heat-conducting element 36 and the second heat-conducting element 38 are substantially aligned on the blind combustible heat source 4. However, it will be appreciated that in other embodiments of the invention (not shown), the first heat-conducting element 36 may extend beyond the second heat-conducting element 38 in the upstream direction, so that the rear portion 4b of the blind combustible heat source surrounded by the first heat-conducting element 36 is larger than the rear portion of the blind combustible heat source surrounded by the second heat-conducting element 38.

[0254] The second heat-conducting element 38 is a double-layer laminate comprising an inner layer 38a of a heat-insulating material such as paper and an outer layer 38b of a heat-conductive material such as aluminum. Figure 1 As shown in FIG, the outer layers 38b of heat-conductive material of the first heat-conducting element 36 and the second heat-conducting element 38 are radially separated by an inner layer 38a of heat-insulating material of the second heat-conducting element 38, which is located between the outer layers 38b of heat-conductive material of the first heat-conducting element 36 and the second heat-conducting element 38.

[0255] The smoking article 2 according to the first embodiment of the invention comprises one or more first air inlets 40 around the periphery of the aerosol-forming substrate 10 .

[0256] like Figure 1 As shown in FIG. 1 , the first air inlet 40 arranged in an annular manner is provided in the molded piece packaging 26 of the aerosol-forming substrate 10, the inner layer 38a of the heat insulating material of the second heat-conducting element 38 and the outer layer 38b of the heat-conducting material, and the covering outer packaging 20 to receive the cold air (at Figure 1 10) into the aerosol-forming substrate 10. It will be appreciated that in other embodiments of the invention (not shown), in which the first heat-conducting element 36 surrounds and directly contacts the entire length of the aerosol-forming substrate 10, an annularly arranged first air inlet 40 may be provided in the shaped piece wrapper 26 of the aerosol-forming substrate 10, the first heat-conducting element 36, the inner layer 38a of the heat-insulating material and the outer layer 38b of the heat-conducting material of the second heat-conducting element 38, and the covering outer wrapper 20, to admit cool air into the aerosol-forming substrate 10.

[0257] In use, a user lights the blind combustible heat source 4 of the smoking article 2 according to the first embodiment of the invention and then draws on the mouthpiece 18. When the user draws on the mouthpiece 18, the cool air (at Figure 1 The air (indicated by the dashed arrow in the figure) is drawn through the first air inlet 40 into the aerosol-forming substrate 10 of the smoking article 2.

[0258] The front portion 10a of the aerosol-forming substrate 10 is heated by conduction via the rear face 8 of the blind combustible heat source 4 and the first barrier 22 and the first heat-conducting element 36 .

[0259] The aerosol-forming substrate 10 is heated by conduction to release glycerol and other volatile and semi-volatile compounds from the plug of tobacco-based homogenized material 24. The compounds released from the aerosol-forming substrate 10 form an aerosol, which is entrained in the air drawn into the aerosol-forming substrate 10 of the smoking article 2 through the first air inlet 40 as the inhaled air flows through the aerosol-forming substrate 10. The inhaled air and the entrained aerosol (at Figure 1 The inhaled air and entrained aerosol are cooled and condensed. The cooled inhaled air and entrained aerosol are passed downstream through the mouthpiece 18 and delivered to the user through the proximal end of the smoking article 2 according to the first embodiment of the invention. The non-combustible, substantially air-impermeable first barrier 22 on the rear face 8 of the blind combustible heat source 4 separates the blind combustible heat source 4 from air drawn through the smoking article 2 so that, in use, air drawn through the smoking article 2 does not directly contact the blind combustible heat source 4.

[0260] In use, the second heat-conducting element 38 remains heated within the smoking article 2 to help maintain the temperature of the first heat-conducting element 36 during smoking. This in turn helps maintain the temperature of the aerosol-forming substrate 10 to promote continuous and enhanced aerosol delivery. In addition, the second heat-conducting element 38 transfers heat along the aerosol-forming substrate 10 beyond the downstream end of the first heat-conducting element 36 so that the heat is dispersed through a larger volume of the aerosol-forming substrate 10. This helps provide more consistent puff-to-puff aerosol delivery.

[0261] Example AD

[0262] A smoking article according to the first embodiment of the invention having the dimensions shown in Table 1 was assembled, comprising an annular arrangement of first air inlets around the periphery of the aerosol-forming substrate. The smoking article was assembled without an outer wrapper so that the outer layer of the second heat-conducting element was visible on the exterior of the smoking article. Figure 1The arrows labelled A, B, C and D respectively in FIG. 1 show the positions of the annular arrangement of first air inlets around the periphery of the aerosol-forming substrate in the smoking article.

[0263] Comparative Example E

[0264] For comparison purposes, a smoking article not according to the invention having the dimensions shown in Table 1 was assembled. The smoking article not according to the invention differs from the smoking articles according to the invention of Examples AD in that it comprises a third air inlet arranged annularly around the circumference of the cylindrical open-ended cellulose acetate hollow tube of the transfer element, instead of a first air inlet arranged annularly around the circumference of the aerosol-forming substrate. The position of the third air inlet arranged annularly around the circumference of the cylindrical open-ended cellulose acetate hollow tube of the transfer element is determined by Figure 1 The arrow marked E shows.

[0265] When a user draws on the mouthpiece of a smoking article not according to the present invention, cool air is drawn into the cylindrical open-ended cellulose acetate hollow tube of the transfer element of the smoking article through the third air inlet. The drawn air passes upstream through the cellulose acetate of the cylindrical open-ended cellulose acetate hollow tube to the aerosol-forming substrate. The drawn air then passes downstream through the aerosol-forming substrate, the interior of the cylindrical open-ended cellulose acetate hollow tube of the transfer element, the aerosol-cooling element, the spacer element and the mouthpiece, and is delivered to the user through the proximal end of the smoking article.

[0266] Table 1

[0267]

[0268]

[0269] The total glycerine and nicotine delivery was measured for the smoking articles according to the invention of Examples AD and the smoking article not according to the invention of Comparative Example E. The results are shown in Figure 2 and Table 2. To measure total glycerin and nicotine delivery, the smoking article was ignited using a conventional yellow flame lighter and smoked using a smoking machine, under the Health Canada smoking protocol, over 12 puffs with a puff volume of 55 ml, a puff duration of 2 seconds, and a puff interval of 30 seconds. The conditions for smoking and the smoking machine specifications are set forth in ISO Standard 3308 (ISO 3308:2000). The atmosphere for conditioning and testing is set forth under ISO Standard 3402.

[0270] During the smoking run, glycerin and nicotine in the mainstream aerosol are retained on the fiberglass filter (cartridge mat). After the smoking run, glycerin and nicotine are extracted from the fiberglass filter using an alcohol solution. The solution is then assayed using gas chromatography, where glycerin and nicotine are quantified.

[0271] like Figure 2 As shown in Table 2, the inclusion of one or more first air inlets around the periphery of the aerosol-forming substrate increases the total glycerin and nicotine delivery of the smoking articles according to the present invention of Examples AD compared to the smoking article not according to the present invention of Comparison E in which one or more third air inlets are provided downstream of the aerosol-forming substrate.

[0272] Table 2

[0273]

[0274]

[0275] The specific embodiments described above are intended to illustrate the invention. However, other embodiments may be prepared without departing from the spirit and scope of the invention as defined in the claims, and it is to be understood that the specific embodiments described above are not intended to be limiting.

Claims

1. A smoking article, comprising: a combustible heat source having opposing front and rear faces, wherein the combustible heat source is a closed combustible heat source that does not include any airflow passage extending from the front face to the rear face of the combustible heat source; an aerosol-forming substrate located downstream of the rearward portion of the combustible heat source; a non-combustible, air-impermeable barrier disposed between the rear face of the combustible heat source and the aerosol-forming substrate; a mouthpiece located downstream of the aerosol-forming substrate; a transfer element located between the aerosol-forming substrate and the mouthpiece; a first heat-conducting element surrounding a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate; a second heat-conducting element surrounding at least a portion of the first heat-conducting element, wherein at least a portion of the second heat-conducting element is radially separated from the first heat-conducting element, and wherein the second heat-conducting element extends beyond the first heat-conducting element in a downstream direction and overlies an entire length of the aerosol-forming substrate and an entire length of the transfer element; and One or more first air inlets around the periphery of the aerosol-forming substrate.

2. The smoking article according to claim 1, wherein the entirety of the second heat-conducting element is radially separated from the first heat-conducting element.

3. The smoking article of claim 1, wherein the first heat-conducting element and the second heat-conducting element are radially separated by an insulating material.

4. The smoking article according to any one of claims 1 to 3, wherein the first heat-conducting element and the second heat-conducting element are radially separated by at least 50 microns.

5. The smoking article according to any one of claims 1 to 3, wherein the second heat-conducting element overlies at least a portion of the combustible heat source.

6. The smoking article according to any one of claims 1 to 3, further comprising an outer wrapper surrounding the second heat-conducting element.

7. The smoking article according to any one of claims 1 to 3, wherein the second heat-conducting element is disposed on the exterior of the smoking article such that the second heat-conducting element is visible on an outer surface of the smoking article.

8. The smoking article according to any one of claims 1 to 3, wherein the second heat-conducting element is formed from a laminate material comprising one or more layers of heat-conductive material.

9. The smoking article according to any one of claims 1 to 3, wherein the second heat-conducting element comprises one or more layers of heat reflective material.

10. The smoking article of claim 9, wherein the heat reflective material reflects more than 50% of incident radiation.

11. The smoking article according to any one of claims 1 to 3, wherein the second heat-conducting element comprises steel.

12. The smoking article according to any one of claims 1 to 3, wherein the transfer element comprises at least one open-ended tubular hollow body.

13. The smoking article according to any one of claims 1 to 3, wherein the aerosol-forming substrate abuts the rear face of the combustible heat source.

14. The smoking article according to any one of claims 1 to 3, wherein the aerosol-forming substrate is spaced apart from a rear face of the combustible heat source.

15. The smoking article according to claim 14, further comprising one or more second air inlets between the rear face of the combustible heat source and the aerosol-forming substrate.

16. The smoking article according to any one of claims 1 to 3, further comprising one or more aerosol-modifying agents downstream of the aerosol-forming substrate.

17. The smoking article according to any one of claims 1 to 3, wherein the one or more first air inlets are located close to a downstream end of the aerosol-forming substrate.

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