Smoking article including flow restrictor in hollow tube

Abstract

There is provided a smoking article comprising a filter. The filter comprises a hollow tube having an inner surface. The filter further comprises a flow restrictor disposed in the hollow tube, and adapted to divert at least a portion of the flow of mainstream smoke between an outer surface of the restrictor and the inner surface of the hollow tube. Furthermore, the filter comprises a retaining element disposed downstream of the flow restrictor, the retaining element having one or more openings. Each of the openings of the retaining element has at least one cross-sectional dimension that is smaller than the smallest cross-sectional dimension of the flow restrictor to prevent the flow restrictor from moving downstream of the retaining element. The flow restrictor is substantially spherical, at least one cross-sectional dimension of the one or more openings of the retaining element being smaller than the diameter of the flow restrictor.

Claims

1. A smoking article comprising: a hollow tube having an inner surface; a flow restrictor disposed in the hollow tube, and adapted to divert the flow of mainstream smoke between an outer surface of the restrictor and the inner surface of the hollow tube; and a retaining element disposed downstream of the flow restrictor, the retaining element having one or more openings; wherein each of the one or more openings of the retaining element has at least one cross-sectional dimension that is smaller than the largest cross-sectional dimension of the flow restrictor to prevent the flow restrictor from moving downstream of the retaining element; and wherein the flow restrictor is substantially spherical, at least one cross-sectional dimension of the one or more openings of the retaining element being smaller than the diameter of the spherical flow restrictor.

2. A smoking article according to claim 1, wherein the transverse cross-sectional area of the flow restrictor is smaller than the transverse cross-sectional area of the hollow tube and larger than the transverse cross-sectional area of the opening.

3. A smoking article according to claim 2, wherein the flow restrictor is adapted to generate a RTD between approximately 150 mm H.sub.2O (about 1470 Pa) and approximately 500 mm H.sub.2O (about 4900 Pa).

4. A smoking article according to claim 2, wherein the retaining element is integral with the hollow tube.

5. A smoking article according to claim 2, wherein the retaining element is provided as a disc or plug comprising a porous material.

6. A smoking article according to claim 2, wherein the flow restrictor comprises one or more air flow grooves on its outer surface.

7. A smoking article according to claim 1, wherein the flow restrictor is adapted to generate a RTD between approximately 150 mm H.sub.2O (about 1470 Pa) and approximately 500 mm H.sub.2O (about 4900 Pa).

8. A smoking article according to claim 7, wherein the retaining element is adapted to generate a RTD between approximately 1 mm H.sub.2O (about 10 Pa) and approximately 20 mm H.sub.2O (about 200 Pa).

9. A smoking article according to claim 1, wherein the retaining element is adapted to generate a RTD between approximately 1 mm H.sub.2O (about 10 Pa) and approximately 20 mm H.sub.2O (about 200 Pa).

10. A smoking article according to claim 1, wherein the cross-sectional area available for the mainstream smoke flowing around the flow restrictor is from about 0.71 square mm to about 1.13 square mm.

11. A smoking article according to claim 1, wherein the cross-sectional area available for the mainstream smoke flowing around the flow restrictor is from about 0.80 square mm to about 1.03 square mm.

12. A smoking article according to claim 1, wherein the retaining element is integral with the hollow tube.

13. A smoking article according to claim 12, wherein the retaining element comprises at least a portion extending from a lateral wall of the hollow tube and partly obstructing the downstream mouth of the hollow tube.

14. A smoking article according to claim 1, wherein the retaining element comprises at least a portion extending from a lateral wall of the hollow tube and partly obstructing the downstream mouth of the hollow tube.

15. A smoking article according to claim 1, wherein the retaining element comprises a tubular segment disposed downstream of the hollow tube, the inner diameter of the tubular segment being smaller than the inner diameter of the hollow tube.

16. A smoking article according to claim 1, wherein the retaining element is provided as a disc or plug comprising a porous material.

17. A smoking article according to claim 1, wherein the flow restrictor comprises one or more air flow grooves on its outer surface.

18. A smoking article according to claim 1, wherein the flow restrictor has a compressive yield strength greater than about 8.0 kPa.

19. A smoking article according to claim 1, wherein the flow restrictor has a compressive strength at a deformation of 10 percent greater than about 50.0 kPa.

20. A filter for a smoking article, the filter comprising: a hollow tube having an inner surface; a flow restrictor disposed in the hollow tube, and adapted to divert the flow of mainstream smoke between an outer surface of the restrictor and the inner surface of the hollow tube; and a retaining element disposed downstream of the flow restrictor, the retaining element having one or more openings; wherein each of the one or more openings of the retaining element has at least one cross-sectional dimension that is smaller than the largest cross-sectional dimension of the flow restrictor to prevent the flow restrictor from moving downstream of the retaining element.

Description

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

(2) FIG. 1 is a perspective view of a smoking article according to one embodiment of the invention;

(3) FIG. 2 is a cross-sectional view of a filter according to a first embodiment of the invention;

(4) FIG. 3 is a cross-sectional view of a filter according to a second embodiment of the invention.

(5) FIG. 1 is a perspective view of a smoking article 100 according to one embodiment of the invention. The smoking article 100 includes a generally cylindrical tobacco rod 101 and a generally cylindrical filter 103. The tobacco rod 101 and filter 103 are axially aligned in an end-to-end relationship, preferably abutting one another. The tobacco rod includes an outer wrapper 105 circumscribing the smoking material. The outer wrapper 105 may be a porous wrapping material or. paper wrapper. The tobacco is preferably a shredded tobacco or. tobacco cut filter. The tobacco rod 101 has an upstream, lit end 107 and a downstream end 109. The filter 103 has an upstream end 111 and a downstream, mouth end 113. The upstream end 111 of the filter 103 is adjacent the downstream end 109 of the tobacco rod 101.

(6) The filter component 103 is attached to the tobacco rod 101 by tipping material 115 which circumscribes the entire length of the filter 103 and an adjacent region of the tobacco rod 101. The tipping material 115 is shown partially removed from the smoking article in FIG. 1, for clarity. The tipping material 115 is typically a paper like product. However, any suitable material can be used. In this embodiment, the tipping material 115 includes a circumferential row of perforations 117 aligned with the filter 103. The perforations are provided for ventilation of the mainstream smoke.

(7) In this specification, the upstream and downstream relative positions between smoking article components are described in relation to the direction of mainstream smoke as it is drawn from the tobacco rod 101 and through the filter 103.

(8) FIG. 2 is a cross-sectional view of a filter 103 according to a first embodiment of the invention. The filter 103 may be used in the smoking article of FIG. 1. In FIG. 2, the filter 103 comprises a hollow tube 201. The hollow tube 201 has an outer diameter 202 and an inner diameter 203. The filter 103 further comprises a flow restrictor 204. The flow restrictor 204 is substantially spherical, with a diameter 205. The flow restrictor 204 is disposed in the hollow tube 201.

(9) Diameter 205 of the flow restrictor 204 is slightly larger than inner diameter 203 of the hollow tube 201, so the flow restrictor 204 causes the wall of the hollow tube 201 to distort slightly and the flow restrictor 204 is maintained wedged inside the hollow tube 201 by friction.

(10) The flow restrictor 204 has grooves 206 formed in its periphery and defining respective passageways 207 permeable to air and smoke between the wall of the hollow tube 201 and the flow restrictor 204. As shown schematically by the arrows, air drawn through the filter 103 during use of the smoking article is forced to flow around the flow restrictor 204 and through a reduced cross section substantially defined by the passageways 207.

(11) The filter further comprises a retaining element 208 disposed immediately downstream of the hollow tube 201. The retaining element 208 comprises a pair of opposite pins projecting radially from the periphery of the hollow tube 201 and having a length such as to prevent the flow restrictor 204 to roll out of the hollow tube 201. In more detail, the radially inner ends of the two pins are separated by a distance 209 smaller than the diameter 205 of the flow restrictor 204.

(12) FIG. 3 is a cross-sectional view of a filter 103 according to a second embodiment of the invention. The filter 103 may be used in the smoking article of FIG. 1. In FIG. 3, the filter 103 comprises a hollow tube 201. The hollow tube 201 has an outer diameter 202 and an inner diameter 203. The filter 103 further comprises a flow restrictor 204. The flow restrictor 204 is substantially spherical, with a diameter 205. The flow restrictor 204 is loosely arranged inside the hollow tube 201.

(13) Diameter 205 of the flow restrictor 204 is slightly smaller than inner diameter 203 of the hollow tube 201, so the flow restrictor 204 is free to move (for example, to roll) inside the hollow tube 201.

(14) The flow restrictor 204 has a substantially smooth outer surface. As shown schematically by the arrows, air drawn through the filter 103 during use of the smoking article is forced to flow around the flow restrictor 204 and through a reduced cross section substantially defined between the outer surface of the flow restrictor 204 and the lateral wall of the hollow tube 201.

(15) The filter further comprises a retaining element 208 disposed immediately downstream of the hollow tube 201. The retaining element 208 comprises a tubular segment made of a non-porous material and defining an opening having a square shape, that is a shape other than the shape of the cross section of the flow restrictor 204. In more detail, the side of the square-shaped opening of the tubular segment has a length 209 that is smaller than the diameter 205 of the flow restrictor 204. Thus, even when smoke is drawn from the downstream end of the filter 103, the flow restrictor 204 cannot plug the opening of the tubular segment 208.

(16) Neither filter 103, 103 in FIGS. 2 and 3 include additional filter elements upstream or downstream of the hollow tube. However, it will be appreciated that an additional element may be included, for example upstream of the hollow tube, so as to prevent the flow restrictor 103, 103 from contacting the tobacco rod 101 and accidentally being burnt during use of the smoking article by a consumer. For example, a porous plug element may be disposed immediately upstream of the hollow tube 201.

(17) The invention will be further described with reference to the following example.

EXAMPLE 1

(18) In accordance with the measurement procedure outlined above, the generated RTD has been assessed for a smooth-surfaced spherical flow restrictor having a diameter of 8.00 mm loosely disposed within smooth-surfaced hollow tubes having different internal diameters. The results are given in the following table.

(19) TABLE-US-00001 Hollow tube Available cross-sectional RTD diameter [mm] area [square mm] [mm H.sub.2O] 8.05 0.630 608 8.06 0.757 462 8.07 0.883 290 8.09 1.137 158