Smoking article with dual heat-conducting elements and improved airflow

Abstract

A smoking article is provided, including a combustible heat source having opposed front and rear faces; an aerosol-forming substrate downstream of the rear face; a first heat-conducting element circumscribing a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate; 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; and one or more first air inlets around a periphery of the aerosol-forming substrate.

Claims

1. A smoking article, comprising: a combustible heat source having opposed front and rear faces, wherein the combustible heat source is a blind combustible heat source; an aerosol-forming substrate downstream of the rear face of the combustible heat source; a non-combustible substantially air impermeable barrier disposed between the rear face of the combustible heat source and the aerosol-forming substrate; a mouthpiece downstream of the aerosol-forming substrate; a transfer element between the aerosol-forming substrate and the mouthpiece; a first heat-conducting element circumscribing a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate; a second heat-conducting element overlying 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, 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-generating substrate and an entire length of the transfer element; and one or more first air inlets around a periphery of the aerosol-forming substrate and being configured to draw air therethrough into the aerosol-forming substrate in a radial direction.

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.

3. The smoking article according to claim 1, wherein the first heat-conducting element and the second heat-conducting element are radially separated by a heat-insulative material.

4. 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.

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

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

7. The smoking article according to claim 1, wherein the second heat-conducting element is disposed at an outside of the smoking article, such that the second-heat conducting element is visible on an external surface of the smoking article.

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

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

10. The smoking article according to claim 9, wherein the heat-reflective material is configured to reflect more than 50% of incident radiation.

11. The smoking article according to claim 1, further comprising one or more second air inlets between the rear face of the combustible heat source and the aerosol-forming substrate.

12. The smoking article according to claim 1, further comprising one or more aerosol modifying agents downstream of the aerosol-forming substrate.

13. The smoking article according to claim 1, wherein the second heat-conducting element extends beyond the first heat-conducting element in a downstream direction and radially surrounds the transfer element.

14. A smoking article, comprising: a combustible heat source having opposed front and rear faces, wherein the combustible heat source is a blind combustible heat source; an aerosol-forming substrate downstream of the rear face of the combustible heat source; a non-combustible substantially air impermeable barrier disposed between the rear face of the combustible heat source and the aerosol-forming substrate; a mouthpiece downstream of the aerosol-forming substrate; a transfer element between the aerosol-forming substrate and the mouthpiece; a first heat-conducting element circumscribing a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate; a second heat-conducting element overlying 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, 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-generating substrate and an entire length of the transfer element; and one or more first air inlets around a periphery of the aerosol-forming substrate, wherein the first heat-conducting element and the second heat-conducting element are radially separated by at least 20 microns.

15. A smoking article, comprising: a combustible heat source having opposed front and rear faces, wherein the combustible heat source is a blind combustible heat source; an aerosol-forming substrate downstream of the rear face of the combustible heat source; a non-combustible substantially air impermeable barrier disposed between the rear face of the combustible heat source and the aerosol-forming substrate; a mouthpiece downstream of the aerosol-forming substrate; a transfer element between the aerosol-forming substrate and the mouthpiece; a first heat-conducting element circumscribing a rear portion of the combustible heat source and at least a front portion of the aerosol-forming substrate; a second heat-conducting element overlying 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, 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-generating substrate and an entire length of the transfer element; and one or more first air inlets around a periphery of the aerosol-forming substrate, wherein the first heat-conducting element and the second heat-conducting element are radially separated by a heat-insulative material.

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

17. The smoking article according to claim 1, wherein the one or more first air inlets are located proximate to the downstream end of the aerosol-forming substrate.

18. The smoking article according to claim 1, wherein the transfer element comprises at least one open-ended tubular 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 an embodiment of the invention; and

(3) FIG. 2 shows a graph of total aerosol-former and nicotine deliveries for smoking articles according to the embodiment of the invention shown in FIG. 1.

(4) The smoking article 2 according to the first embodiment of the invention shown in FIG. 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 abutting coaxial alignment. As shown in FIG. 1, the aerosol-forming substrate 10, transfer element 12, aerosol-cooling element 14, spacer element 16 and mouthpiece 18 and a rear portion of the blind combustible heat source 4 are wrapped in an outer wrapper 20 of sheet material such as, for example, cigarette paper, of low air permeability. It will be appreciated that in other embodiments of the invention (not shown), the outer wrapper 20 may be omitted.

(5) 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. As shown in FIG. 1, a non-combustible substantially air impermeable first barrier 22 in the form of a disc of aluminium foil 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 disc of aluminium foil 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.

(6) The aerosol-forming substrate 10 is located immediately downstream of the first barrier 22 applied to the rear face 8 of the blind combustible heat source 4. The aerosol-forming substrate 10 comprises a cylindrical plug of homogenised tobacco-based material 24 including an aerosol former such as, for example, glycerine, wrapped in plug wrap 26.

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

(8) The aerosol-cooling element 14 is located immediately downstream of the transfer element 12 and comprises a gathered sheet of biodegradable polymeric material such as, for example, polylactic acid.

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

(10) The mouthpiece 18 is located immediately downstream of the spacer element 16. As shown in FIG. 1, the mouthpiece 18 is located at the proximal end of the smoking article 2 and comprises a cylindrical plug of suitable filtration material 32 such as, for example, cellulose acetate tow of very low filtration efficiency, wrapped in filter plug wrap 34.

(11) The smoking article may further comprise a band of tipping paper (not shown) circumscribing a downstream end portion of the outer wrapper 20.

(12) As shown in FIG. 1, the smoking article 2 further comprises a first heat-conducting element 36 of suitable material such as, for example, aluminium foil, around and in direct contact with a rear portion 4b of the blind combustible heat source 4 and a front portion 10a of the aerosol-forming substrate 10. In the smoking article 2 according to the first embodiment of the invention shown in FIG. 1, the aerosol-forming substrate 10 extends downstream beyond the first heat-conducting element 36. That is, the first heat-conducting element 36 is not around and in direct contact with a 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 be around and in contact with the entire length of the aerosol-forming substrate 10.

(13) As shown in FIG. 1, the smoking article 2 also further comprises a second heat-conducting element 38 around a 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. In the smoking article 2 according to the first embodiment of the invention shown in FIG. 1, the second heat-conducting element 34 extends to approximately the same position on the blind combustible heat source 4 as the first heat-conducting element 36 in the upstream direction, such that the upstream ends of the first heat-conducting element 36 and the second heat-conducting element 38 are substantially aligned over 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, such that the rear portion 4b of the blind combustible heat source circumscribed by the first heat-conducting element 36 is larger than the rear portion of the blind combustible heat source circumscribed by the second heat-conducting element 38.

(14) The second heat-conducting element 38 is a double layer laminate material comprising an inner layer 38a of heat-insulative material such as, for example, paper and an outer layer 38b of heat-conductive material, such as, for example, aluminium. As shown in FIG. 1, the first heat-conducting element 36 and the outer layer 38b of heat-conductive material of the second heat-conducting element 38 are radially separated by the inner layer 38a of heat-insulative material of the second heat-conducting element 38, which is located between the first heat-conducting element 36 and the outer layer 38b of heat-conductive material of the second heat-conducting element 38.

(15) 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.

(16) As shown in FIG. 1, a circumferential arrangement of first air inlets 40 is provided in the plug wrap 26 of the aerosol-forming substrate 10, the inner layer 38a of heat-insulative material and the outer layer 38b of heat-conductive material of the second heat conducting element 38, and the overlying outer wrapper 20 to admit cool air (shown by dotted arrows in FIG. 1) 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 is around and in direct contact with the entire length of the aerosol-forming substrate 10, a circumferential arrangement of first air inlets 40 may be provided in the plug wrap 26 of the aerosol-forming substrate 10, the first heat-conducting element 36, the inner layer 38a of heat-insulative material and the outer layer 38b of heat-conductive material of the second heat conducting element 38, and the overlying outer wrapper 20 to admit cool air into the aerosol-forming substrate 10.

(17) In use, a user ignites 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 a user draws on the mouthpiece 18, cool air (shown by dotted arrows in FIG. 1) is drawn into the aerosol-forming substrate 10 of the smoking article 2 through the first air inlets 40.

(18) The front portion 10a of the aerosol-forming substrate 10 is heated by conduction through the rear face 8 of the blind combustible heat source 4 and the first barrier 22 and the first heat-conducting element 36.

(19) The heating of the aerosol-forming substrate 10 by conduction releases glycerine and other volatile and semi-volatile compounds from the plug of homogenised tobacco-based material 24. The compounds released from the aerosol-forming substrate 10 form an aerosol that is entrained in the air drawn into the aerosol-forming substrate 10 of the smoking article 2 through the first air inlets 40 as it flows through the aerosol-forming substrate 10. The drawn air and entrained aerosol (shown by dashed arrows in FIGS. 1a) and 2) pass downstream through the interior of the cylindrical open-ended hollow cellulose acetate tube 28 of the transfer element 12, the aerosol-cooling element 14 and the spacer element 16, where they cool and condense. The cooled drawn air and entrained aerosol pass downstream through the mouthpiece 18 and are 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 isolates the blind combustible heat source 4 from air drawn through the smoking article 2 such that, in use, air drawn through the smoking article 2 does not come into direct contact with the blind combustible heat source 4.

(20) In use, the second heat-conducting element 38 retains heat 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 facilitate continued 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 heat is dispersed through a larger volume of the aerosol-forming substrate 10. This helps to provide a more consistent puff-by-puff aerosol delivery.

EXAMPLES A-D

(21) Smoking articles according to the first embodiment of the invention comprising a circumferential arrangement of first air inlets around the periphery of the aerosol-forming substrate are assembled having the dimensions shown in Table 1. The smoking articles are assembled without an outer wrapper, such that the outer layer of the second heat-conducting element is visible on the exterior of the smoking articles. The location of the circumferential arrangement of first air inlets around the periphery of the aerosol-forming substrate in the smoking articles is shown by the arrows labelled A, B, C and D, respectively, in FIG. 1.

COMPARATIVE EXAMPLE E

(22) For the purposes of comparison, a smoking article not according to the invention is assembled having the dimensions shown in Table 1. The smoking article not according to the invention differs from the smoking articles according to the invention of Examples A-D in that it comprises a circumferential arrangement of third air inlets around the periphery of the cylindrical open-ended hollow cellulose acetate tube of the transfer element, rather than a circumferential arrangement of first air inlets around the periphery of the aerosol-forming substrate. The location of the circumferential arrangement of third air inlets around the periphery of the cylindrical open-ended hollow cellulose acetate tube of the transfer element is shown by the arrow labelled E in FIG. 1.

(23) When a user draws on the mouthpiece of the smoking article not according to the invention, cool air is drawn into the cylindrical open-ended hollow cellulose acetate tube of the transfer element of the smoking article through the third air inlets. The drawn air passes upstream through the cellulose acetate of the cylindrical open-ended hollow cellulose acetate tube to the aerosol-forming substrate. The drawn air then passes downstream through the aerosol-forming substrate, the interior of the cylindrical open-ended hollow cellulose acetate 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.

(24) TABLE-US-00001 TABLE 1 Example A B C D E Overall length (mm) 79 Diameter (mm) 8 Blind combustible heat source Length (mm) 9 Diameter (mm) 7.78 Thickness of first barrier (microns) 20 Aerosol-forming substrate Length (mm) 8 Diameter (mm) 7.8 Density (g/cm.sup.3) 0.54 Amount of aerosol former (glycerine) 20 (% dry weight basis) Transfer element Length (mm) 26 External diameter (mm) 7.85 Internal diameter (mm) 4 Cooling element Length (mm) 12 Spacer element Length (mm) 12 Mouthpiece Length (mm) 12 Diameter (mm) 7.95 Heat-conducting elements Length of first heat-conducting element 5 (mm) Thickness of first heat-conducting element 20 (μm) Distance of first heat-conducting element 6 from front face of blind combustible heat source (mm) Length of second heat-conducting element 37 (mm) Thickness of second heat-conducting element 6 (μm) Distance of second heat-conducting element 6 from front face of blind combustible heat source (mm) First air inlets Distance from front face of blind combustible 12 14 15 16 — heat source (mm) Distance from upstream end of aerosol-forming 3 5 6 7 — substrate combustible heat source (mm) Third air inlets Distance from front face of blind combustible — — — — 22 heat source (mm) Distance from upstream end of hollow cellulose — — — — 5 acetate tube (mm)

(25) The total glycerine and nicotine deliveries of the smoking articles according to the invention of Examples A-D and the smoking article not according to the invention of Comparative Example E are measured. The results are shown in FIG. 2 and Table 2. To measure the total glycerine and nicotine deliveries, the smoking articles are ignited using a conventional yellow flame lighter and smoked under a Health Canada smoking regime over 12 puffs with a puff volume of 55 ml, puff duration of 2 seconds and a puff interval of 30 seconds using a smoking machine. Conditions for smoking and smoking machine specifications are set out in ISO Standard 3308 (ISO 3308:2000). The atmosphere for conditioning and testing is set out in ISO Standard 3402.

(26) During the smoking run, glycerine and nicotine in the mainstream aerosol are trapped on a fiberglass filter disc (Cambridge Pad). After the smoking run, glycerine and nicotine are extracted from the fiberglass filter disc using an alcohol solution. The solution is then assayed, with glycerine and nicotine being quantified, using a Gas Chromatography method.

(27) As shown in FIG. 2 and Table 2, inclusion of one or more first air lets around the periphery of the aerosol-forming substrate increases the total glycerine and nicotine deliveries of the smoking articles according to the invention of Examples A-D compared to the smoking article not according to the invention of Comparative E in which one or more third air inlets are provided downstream of the aerosol-forming substrate.

(28) TABLE-US-00002 TABLE 2 Delivery/mg Example (i) Glycerine (ii) Nicotine A 5.76 1.17 B 5.48 1.25 C 5.75 1.29 D 5.71 1.36 E 2.78 1.00

(29) The specific embodiments described above are intended to illustrate the invention. However, other embodiments may be made 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.