Smoking article including dual heat-conducting elements

Abstract

A smoking article is provided, including a heat source; an aerosol-forming substrate downstream of the heat source; a first heat-conducting element around and in contact with a rear portion of the heat source and an adjacent front portion of the aerosol-forming substrate; and a second heat-conducting element around at least a portion of the first heat-conducting element. At least part of the second heat-conducting element is radially separated from the first heat-conducting element; and, preferably, the first and second heat-conducting elements are separated by an outer paper wrapper.

Claims

1. A smoking article, comprising: a blind combustible heat source in which no longitudinal airflow channels are provided in the heat source, such that air drawn through the smoking article does not pass through any airflow channels along the heat source; an aerosol-forming substrate downstream of the blind combustible heat source; an airflow directing element downstream of the aerosol-forming substrate; at least one air inlet between a downstream end of the aerosol-forming substrate and a downstream end of the airflow directing element; a first heat-conducting element around and in contact with a rear portion of the blind combustible heat source and an adjacent front portion of the aerosol-forming substrate; and a second heat-conducting element around at least a portion of the first heat-conducting element, wherein at least part of the second heat-conducting element is radially separated from the first heat-conducting element.

2. The smoking article according to claim 1, wherein all of the second heat-conducting element is radially separated from the first heat-conducting element such that there is no direct contact between the first and second heat-conducting elements.

3. The smoking article according to claim 1, wherein the first heat-conducting element and the second heat-conducting element are radially separated by at least one layer of a heat-insulating material.

4. The smoking article according to claim 3, wherein the heat-insulating material is a paper wrapper.

5. The smoking article according to claim 1, wherein the second heat-conducting element comprises one or more layers of a heat-reflective material.

6. The smoking article according to claim 1, wherein the second heat-conducting element comprises one or more layers of aluminium.

7. The smoking article according to claim 1, wherein the second heat-conducting element overlies at least a portion of the aerosol-forming substrate and at least a portion of the heat source.

8. The smoking article according to claim 1, wherein the second heat-conducting element has a maximum thickness of 5 microns to 50 microns.

9. The smoking article according to claim 1, wherein the first heat-conducting element and the second heat-conducting element are radially separated by at least 50 microns.

10. The smoking article according to claim 1, further comprising an outer paper wrapper around the second heat-conducting element.

11. The smoking article according to claim 1, wherein the second heat-conducting element is formed of a laminate material comprising one or more layers of a heat-conducting material.

12. The smoking article according to claim 1, wherein the second heat-conducting element extends beyond the first heat-conducting element in a downstream direction.

13. The smoking article according to claim 1, wherein the upstream edges of the first heat-conducting element and the second heat-conducting element are substantially aligned.

14. A method of adjusting the puff-by-puff aerosol delivery of a smoking article during puffing, the method comprising providing a smoking article according to claim 1 and adjusting the amount by which the second heat-conducting element extends beyond the first heat-conducting element in a downstream direction, over the aerosol-forming substrate.

15. The smoking article according to claim 1, wherein the second heat-conducting element includes steel.

16. The smoking article according to claim 1, wherein the airflow directing element comprises an open-ended, substantially air impermeable hollow body, whereby in use air drawn into the smoking article through the at least one air inlet is first drawn upstream along an exterior portion of the open-ended, substantially air impermeable hollow body to the aerosol-forming substrate and then downstream through an interior of the open-ended, substantially air impermeable hollow body.

Description

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

(2) FIG. 1 shows a schematic longitudinal cross-section of a smoking article according to a first embodiment of the invention;

(3) FIG. 2 shows a schematic longitudinal cross-section of a smoking article according to a second embodiment of the invention; and

(4) FIG. 3 shows a schematic longitudinal cross-section of a smoking article according to a third embodiment of the invention.

(5) The smoking article 2 shown in FIG. 1 comprises a combustible carbonaceous heat source 4, an aerosol-forming substrate 6, an elongate expansion chamber 8 and a mouthpiece 10 in abutting coaxial alignment. The combustible carbonaceous heat source 4, aerosol-forming substrate 6, elongate expansion chamber 8 and mouthpiece 10 are overwrapped in an outer wrapper of cigarette paper 12 of low air permeability.

(6) As shown in FIG. 1, a non-combustible, gas-resistant, first barrier coating 14 is provided on substantially the entire rear face of the combustible carbonaceous heat source 4. In an alternative embodiment, a non-combustible, substantially air impermeable first barrier is provided in the form of a disc that abuts the rear face of the combustible carbonaceous heat source 4 and the front face of the aerosol-forming substrate 6.

(7) The combustible carbonaceous heat source 4 is a non-blind heat source and comprises a central airflow channel 16 that extends longitudinally through the combustible carbonaceous heat source 4 and the non-combustible, gas-resistant, first barrier coating 14. A gas-resistant, heat resistant, second barrier coating (not shown) is provided on the inner surface of the central airflow channel 16.

(8) The aerosol-forming substrate 6 is located immediately downstream of the combustible carbonaceous heat source 4 and comprises a cylindrical plug of tobacco material 18 comprising glycerine as aerosol former and circumscribed by filter plug wrap 20.

(9) A first heat-conducting element 22 consisting of a tube of aluminium foil surrounds and is in contact with a rear portion 4b of the combustible carbonaceous heat source 4 and an abutting front portion 6a of the aerosol-forming substrate 6. As shown in FIG. 1, a rear portion of the aerosol-forming substrate 6 is not surrounded by the first heat-conducting element 22.

(10) The elongate expansion chamber 8 is located downstream of the aerosol-forming substrate 6 and comprises a cylindrical open-ended tube of cardboard 24. The mouthpiece 10 of the smoking article 2 is located downstream of the expansion chamber 8 and comprises a cylindrical plug of cellulose acetate tow 26 of very low filtration efficiency circumscribed by filter plug wrap 28. The mouthpiece 10 may be circumscribed by tipping paper (not shown).

(11) A second heat-conducting element 30 consisting of a tube of aluminium foil surrounds and is in contact with the outer wrapper 12. The second heat-conducting element 30 is positioned over the first heat-conducting element 22 and is of the same dimensions as the first heat-conducting element 22. The second heat-conducting element 30 therefore directly overlies the first heat-conducting element 22, with the outer wrapper 12 between them.

(12) In use, the user ignites the combustible carbonaceous heat source 4 and then draws air through the central airflow channel 16 downstream towards the mouthpiece 10. The front portion 6a of the aerosol-forming substrate 6 is heated primarily by conduction through the abutting non-combusting rear portion 4b of the combustible carbonaceous heat source 4 and the first heat-conducting element 22. The drawn air is heated as it passes through the central airflow channel 16 of the combustible carbonaceous heat source 4 and then heats the aerosol-forming substrate 6 by convection. The heating of the aerosol-forming substrate 6 releases volatile and semi-volatile compounds and glycerine from the tobacco material 18, which are entrained in the heated drawn air as it flows through the aerosol-forming substrate 6. The heated air and entrained compounds pass downstream through the expansion chamber 8, cool and condense to form an aerosol that passes through the mouthpiece 10 into the mouth of the user).

(13) The second heat-conducting element 30 retains heat within the smoking article 2 to help maintain the temperature of the first heat-conducting element 22 during smoking. This in turn helps maintain the temperature of the aerosol-forming substrate 6 to facilitate continued and enhanced aerosol delivery.

(14) The smoking article 54 according to the second embodiment of the invention shown in FIG. 2 comprises a combustible carbonaceous heat source 40, an aerosol-forming substrate 6, an airflow directing element 44, an elongate expansion chamber 8 and a mouthpiece 10 in abutting coaxial alignment. The combustible carbonaceous heat source 40, aerosol-forming substrate 6, airflow directing element 44, elongate expansion chamber 8 and mouthpiece 10 are overwrapped in an outer wrapper of cigarette paper 12 of low air permeability.

(15) As shown in FIG. 2, a non-combustible, substantially air impermeable, barrier coating 14 is provided on the entire rear face of the combustible carbonaceous heat source 40 of the smoking article 54. In an alternative embodiment, instead of a coating, a non-combustible, substantially air impermeable barrier is provided in the form of a disc that abuts the rear face of the combustible carbonaceous heat source 40 and the front face of the aerosol-forming substrate 6.

(16) The combustible carbonaceous heat source 40 is a blind heat source and in the smoking article 54 according to the second embodiment, air drawn through the smoking article for inhalation by a user does not pass through any airflow channels along the combustible heat source 40.

(17) The aerosol-forming substrate 6, expansion chamber 8 and mouthpiece 10 are of the same construction and function as described above in relation to the smoking article 2 of the first embodiment shown in FIG. 1.

(18) As in the smoking article 2 of the first embodiment shown in FIG. 1, a first heat-conducting element 22 consisting of a tube of aluminium foil surrounds and is in contact with a rear portion 4b of the combustible carbonaceous heat source 40 and an abutting front portion 6a of the aerosol-forming substrate 6. A second heat-conducting element 30 consisting of a similar tube of aluminium foil is also provided as described above in relation to the smoking article 2 of the first embodiment shown in FIG. 1.

(19) An airflow directing element 44 is located downstream of the aerosol-forming substrate 6 and comprises an open-ended, substantially air impermeable hollow tube 56 made of, for example, cardboard, which is of reduced diameter compared to the aerosol-forming substrate 6. The upstream end of the open-ended hollow tube 56 abuts the aerosol-forming substrate 6. The downstream end of the open-ended hollow tube 56 is surrounded by an annular substantially air impermeable seal 58 of substantially the same diameter as the aerosol-forming substrate 6. The remainder of the open-ended hollow tube is embedded in a cylindrical plug of cellulose acetate tow 60 of substantially the same diameter as the aerosol-forming substrate 6.

(20) The open-ended hollow tube, 56 and cylindrical plug of cellulose acetate tow 60 are circumscribed by an air permeable inner wrapper 50.

(21) As also shown in FIG. 2, a circumferential row of air inlets 52 are provided in the outer wrapper 12 circumscribing the inner wrapper 50.

(22) In use, when a user draws on the mouthpiece 10, cool air is drawn into the smoking article 54 according to the second embodiment of the invention through the air inlets 52. The drawn air passes upstream between the exterior of the open-ended hollow tube 56 and the inner wrapper 50 through the cylindrical plug of cellulose acetate tow 60 to the aerosol-forming substrate 6.

(23) As in the smoking article 2 according to the first embodiment of the invention shown in FIG. 1 and described above, the aerosol-forming substrate 6 is heated by conduction to form an aerosol that is entrained in the drawn air as it flows through the aerosol-forming substrate 6. The drawn air and entrained aerosol pass downstream through the interior of the hollow tube 56 of the airflow directing element 44 to the expansion chamber 8, where they cool and condense. The cooled aerosol then passes downstream through the mouthpiece 10 of the smoking article 54 into the mouth of the user.

(24) The non-combustible, substantially air impermeable, barrier coating 14 provided on the entire rear face of the combustible carbonaceous heat source 40 isolates the combustible carbonaceous heat source 40 from the airflow pathways through the smoking article 54 such that, in use, air drawn through the smoking article 54 along the airflow pathways does not directly contact the combustible carbonaceous heat source 40.

(25) The second heat-conducting element 30 retains heat within the smoking article 54, as described above in relation to the smoking article 2 of the first embodiment shown in FIG. 1.

(26) Smoking articles according to the second embodiment of the invention shown in FIG. 2 were assembled from the components shown below in Table 1.

(27) TABLE-US-00001 TABLE 1 Smoking article Overall length (mm) 84 Diameter (mm) 7.8 Porous carbonaceous heat source Length (mm) 8 Diameter (mm) 7.8 Thickness of first barrier coating (microns) 500 Aerosol-forming substrate Length (mm) 10 Diameter (mm) 7.8 Density (g/cm.sup.3) 0.73 Aerosol former Glycerine Amount of aerosol former 20% by dry wt. of tobacco Airflow directing element Length (mm) 26 Diameter (mm) 7.8 Length of plug of porous material (mm) 24 Diameter of hollow tube (mm) 3.5 Number of air inlets 4-8 Diameter of air inlets (mm) 0.2 Distance of air inlets from upstream 24 end (mm) Expansion chamber Length (mm) 33 Diameter (mm) 7.8 Mouthpiece Length (mm) 7 Diameter (mm) 7.8 Heat-conducting elements Length (mm) 8 Diameter (mm) 7.8 Thickness of aluminium foil (microns) 20 Length of rear portion of combustible 4 carbonaceous heat source (mm) Length of front portion of aerosol-forming 4 substrate (mm) Length of rear portion of aerosol-forming 6 substrate (mm)

(28) The smoking article 60 according to the third embodiment of the invention shown in FIG. 3 is of similar construction to the smoking article 54 according to the second embodiment of the invention shown in FIG. 2. However, the smoking article 60 shown in FIG. 3 differs from the smoking article 54 shown in FIG. 2 in the construction of the airflow directing element 44, as described below. In addition, unlike in the smoking article 54 shown in FIG. 2, the second heat-conducting element 30 of the smoking article 60 extends about 3 mm beyond the first heat-conducting element 22 in a downstream direction. The second heat-conducting element 30 therefore covers a larger proportion of the aerosol-forming substrate 6.

(29) In the third embodiment of the invention, the airflow directing element 44 comprises an axial, open-ended, substantially air impermeable, truncated cone 62, which is positioned centrally within the smoking article 60. The downstream end of the hollow cone 62 is of substantially the same diameter as the aerosol-forming substrate 6 and the upstream end of the hollow cone 62 is of reduced diameter compared to the aerosol-forming substrate 6. The hollow cone 62 may be formed from any suitable air impermeable material including, but not limited to, cardboard, plastic and combinations thereof.

(30) The upstream end of the substantially air impermeable, truncated hollow cone 62 extends into the aerosol-forming substrate 6.

(31) A circumferential row of air inlets 52 is provided in the outer wrapper 12 circumscribing the hollow cone 62, downstream of the aerosol-forming substrate 6.

(32) In use, when a user draws on the mouthpiece 10 of the smoking article 60 according to the third embodiment of the invention, cool air is drawn into the smoking article 60 through the air inlets 52. The cool air passes upstream between the outer wrapper 12 and the exterior of the hollow cone 62 of the airflow directing element 44 into the aerosol-forming substrate 6.

(33) As in the smoking article 54 according to the second embodiment of the invention shown in FIG. 2 and described above, the aerosol-forming substrate 6 is heated by conduction to form an aerosol that is entrained in the drawn air as it flows through the aerosol-forming substrate 6. The drawn air and entrained aerosol pass downstream along through the interior of the hollow cone 62 of the airflow directing element 44 to the expansion chamber 8, where they cool and condense. The cooled aerosol then passes downstream through the mouthpiece 10 of the smoking article 60 into the mouth of the user.

(34) The second heat-conducting element 30 retains heat within the smoking article 54, as described above in relation to the smoking article 2 of the first embodiment shown in FIG. 1. In addition, the second heat-conducting element 30 transfers heat along the aerosol-forming substrate 6, beyond the downstream end of the first heat-conducting element 22. The heat is therefore dispersed through a larger volume of the aerosol-forming substrate 6 and a more consistent puff-by-puff aerosol delivery is provided, as described above.

(35) It has been found that during smoking of the smoking article 60 of the third embodiment shown in FIG. 3, the temperature of the rear portion 4b of the combustible heat source 40 (as measured by a thermocouple provided at approximately 1 mm from the downstream end of the combustible heat source 40) is approximately 50 C. higher than the corresponding temperature in an identical smoking article without the second heat-conducting element 30. It has further been found that the temperature of the front portion of the aerosol-forming substrate 6 (as measured by a thermocouple provided at approximately 2 mm from the upstream end of the aerosol-forming substrate 6) is between 20 C. and 50 C. higher than the corresponding temperature in an identical smoking article without the second heat-conducting element 30.

(36) It has further been found that the smoking duration of the smoking article 60 of the third embodiment of the invention is increased by approximately 1 minute, or 2 puffs, compared to the smoking duration for an identical smoking article without the second heat-conducting element 30.

(37) It has further been found that the smoking article 60 of the third embodiment of the invention delivers approximately 25 percent more nicotine during smoking compared to an identical smoking article without the second heat-conducting element. Similarly, the smoking article 60 has been found to deliver approximately 30 percent more glycerine during smoking compared to an identical smoking article without the second heat-conducting element 30.

(38) Smoking articles according to the third embodiment may be assembled from the individual components described, the parameters of which may be determined by analogy with the information provided in Table 1 for the second embodiment.

(39) The embodiments shown in FIGS. 1 to 3 and described above illustrate but do not limit the invention. Other embodiments of the invention may be made without departing from the spirit and scope thereof, and it is to be understood that the specific embodiments described herein are not limiting.