Ventilating sheath for smoking article

Abstract

A sheath for a smoking article, such as a filter cigarette, including an exterior sheath (5) that provides a ventilation structure which has a reduced possibility of occlusion, and which also prevents a reduction in filter efficacy when the strength of the draw on the smoking article by the consumer is increased, for example in order to overcome the effects of dilution of the smoke flow with ambient air. The sheath may be manufactured as an independent entity and then fitted to prefabricated smoking articles, or alternatively may be constructed as an integral part of the smoking article.

Claims

1. A smoking article sheath for use with a ventilated smoking article comprising a tipping wrapper, the sheath comprising: a substantially gas impermeable cylindrical tube; a section of longitudinal fins on the internal surface of the tube configured to fit to the smoking article a tipping wrapper and provide channels for drawing ambient air between the sheath and the outer surface of the tipping wrapper of the smoking article, wherein the fins extend along part of the length of the tube; and, an annular section with an internal diameter sized to contact an outer surface of the tipping wrapper of the smoking article when the sheath is in place.

2. A sheath is claimed in claim 1, wherein the fins extend sufficiently inwards to define an inner diameter dimensioned to engage with the outer periphery of the smoking article.

3. A sheath is claimed in claim 1, wherein the fins extend sufficiently inwards to grip a smoking article within the sheath with an interference fit.

4. A sheath is claimed in claim 1, in which the annular section is non-airpermeable.

5. A smoking article sheath, comprising: a flexible sealing flap that seals a gap between the inner surface of the sheath and the outer surface of the smoking article, wherein the gap is formed by the sheath surrounding at least a portion of the smoking article when the sheath is in place, wherein the sheath thus provides two routes for ambient air to be drawn by the user, the first route being through the gap formed between the sheath and the smoking article, and the second route including flow through the smoking article, the flap being moveable between a position in which it seals the gap and a position in which the gap is at least partially open to allow air flow along the first route, and wherein the second route is permanently open.

6. The smoking article comprising a sheath as claimed in claim 5, a rod of smokable material, and a filter.

7. The sheath according to claim 1, comprising a gas impermeable cylindrical tube.

8. The sheath according to claim 1, fitted to a smoking article comprising the tipping wrapper.

9. The sheath according to claim 1, wherein the smoking article is a cigarette.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a fuller understanding of the invention, reference is made to the accompanying drawings which illustrate an embodiment thereof given by way of example, in which:

(2) FIG. 1 shows a schematic side elevation view of the sheath with smoking article in situ.

(3) FIG. 2a shows an axial elevation of the mouth proximal end of an individual sheath, with smoking article in situ, according to the embodiment of FIG. 1.

(4) FIG. 2b shows a cross sectional axial elevation of the distal (rod of smokable material) end of an individual sheath, with smoking article in situ, according to the embodiment of FIG. 1.

(5) FIG. 3a shows a diagram of the sheath of FIG. 1, with smoking article in situ indicating the path of the gaseous smoke flow and ambient air within the smoking article and sheath under conditions of a normal strength of draw.

(6) FIG. 3b shows the diagram as FIG. 3a indicating the path of the gaseous smoke flow and ambient air within the smoking article and sheath upon a high strength of draw.

(7) It should be noted that none of the figures are to scale.

DETAILED DESCRIPTION

(8) Referring to FIG. 1, a substantially gas impermeable tube 5 is fitted to the mouth end of a filter cigarette that comprises a filter 6 and a tobacco rod 17, so as to surround the filter.

(9) The length of the sheath 5 is dictated by a number of factors. It should be long enough to reduce the likelihood of the air inlet being occluded either by the consumer's fingers or lips. However, the sheath should not be so long that it comes into contact with the burning part of the smoking article during normal consumption. When the sheath is for use in conjunction with a cigarette having a filter section, it is desirable for the sheath to surround at least a portion of the filter section and may be of approximately the same length as the filter section or the tipping paper. In some specific examples, the sheath is between 10 and 45 mm in length, preferably between 15 and 35 mm, or approximately 25 mm in length.

(10) The sheath shown in FIG. 1 is internally divided into three sections, a distal section 1 (situated at the end of the sheath furthest from the mouth of the consumer and closest to the rod of smokable material when the sheath is attached to a smoking article), a central section 2, and a proximal section 3 (situated at the mouth end when the sheath is attached to a smoking article).

(11) The body of the sheath is composed of paper or card but can be made of other materials such as plastics or a natural material such as rubber, tobacco leaf, reconstituted tobacco leaf or other sheet material.

(12) The smoking article may be a cigarette, cigarillo, cigar, or other smoking article. In some embodiments, the sheath is for use with slim cigarettes which have a circumference of between 16 mm and 18 mm. According to these embodiments the sheath may provide the consumer of the slim cigarette with the satisfying feel of smoking a wider cigarette, as a result of its diameter being greater than that of the slim cigarette.

(13) The diameter of the sheath is also dictated by a number of factors. It should be wide enough to be able to surround the smoking article with which it is to be used. The internal diameter of the sheath may vary along its length, but it must be such that the sheath may be attached to the smoking article. Ideally, a gap is formed between the internal surface of at least part of the sheath and the smoking article. This gap should be large enough to allow the flow of ambient air, but should also be small enough to afford some degree of control over the air being drawn into and flowing through the sheath. The size of the gap should also be such that the sheath has sufficient structural integrity that it does not collapse when the consumer grips the sheath with his or her lips and/or fingers. The sheath diameter should also feel comfortable to the consumer, optionally with there being little or no detectable difference between the sensation of consuming a smoking article with or without a sheath.

(14) The distal section 1 of the sheath shown in FIG. 1 is designed to create an opening 13 around the smoking article when the sheath is attached and thus provide an inlet for ambient air to become drawn into the sheath. This opening is formed due to the internal diameter 18 of the distal section of the sheath being greater than the diameter 15 of the smoking article 7, as shown in FIG. 2b. The opening may, for example, be between 0.1 mm and 5 mm in width, preferably between 0.2 mm and 1.5 mm, or approximately 1.2 mm in width. In the embodiment shown in FIG. 1, the internal surface of the distal section of the sheath is characterised by a longitudinal series of fins 4, which protrude towards the diametric centre of the distal section. The length 23 of these protuberances is such that they contact the surface of the smoking article 7, as shown in FIG. 2b, thereby providing support for the sheath and ensuring that the opening is maintained. The protuberances may extend along any part of the length of the sheath that is desired; they may extend greater than half of the length of the sheath, or may be shorter, leaving an open annular passage around the smoking article. The number of the protuberances included may be varied and will affect the ease with which air may be drawn through the sheath and the structural strength of the sheath. In one embodiment, the distal section 1 of the sheath has between 1 and 20 protuberances, such as fins, and preferably between 6 and 12.

(15) In an alternative embodiment, the fins may be replaced by a series of grooves or channels in the internal surface of the sheath.

(16) The presence of this gap at the distal end minimises the possibility of a consumer occluding the ventilation structures of the smoking article. Firstly, the location at which ambient air enters the smoking article is away from the mouth end of the smoking article and hence away from the likely position of the fingers or mouth of the consumer. Secondly, the ventilation structure is difficult to occlude due to its being in an axial orientation compared to, for example, perforations on the surface of the sheath.

(17) According to the embodiment shown in FIG. 1, ambient air which is drawn into the sheath via the distal section is able to penetrate the associated smoking article. This may be achieved by the smoking article possessing a suitable means of ventilation. In the embodiment shown in FIG. 1, the smoking article is ventilated by means of gas permeable tipping paper 12 which allows ambient air drawn through the sheath to enter the smoking article. In alternative embodiments, the filter tipping paper of the smoking article is ventilated by means of a series of perforations, or via other suitable means.

(18) The proximal section 3 of the sheath shown in FIG. 1 also creates a gap 13, formed as a result of the internal diameter 18 of the proximal section being greater than the diameter of the smoking article 7 (FIG. 2a).

(19) This proximal section 3 is configured so that ambient air that is passing through the sheath can be prevented from passing directly into the mouth through the annular gap 13 by means of a pressure sensitive valve which, in the embodiment shown in FIG. 1, comprises an annular sectioned, flexible flap 9 attached to the interior of the sheath. Under conditions of low pressure differential across the valve 9, the valve remains shut and in order to maintain a gas-impermeable barrier, the inner edge 10 of the circular seal makes a substantially air-tight contact with the surface of the smoking article thus completely closing the gap 13. However, the flap can open in response to an increased pressure differential to allow gas flow to the mouth through the gap 13, as explained below.

(20) The route taken by ambient air 20 under conditions of a normal strength of draw in the embodiment of FIG. 1 is illustrated in FIG. 3a. Accordingly, ambient air 20 enters the sheath via the distal section 1 and is thus able to pass along the gap 13 between the sheath 5 and the smoking article 7. The tipping paper 12 of the smoking article is porous and ambient air 20 is drawn into the smoking article as it travels through the sheath from the distal end of the sheath to the circular seal 9 which will be in the sealed or closed position. The gaseous smoke flow 19 which is travelling through the smoking article is thus diluted inside the smoking article prior to inhalation.

(21) In some embodiments, the smoking article is provided with perforations which allow the ambient air travelling through the sheath to penetrate the smoking article. Such perforations may be used, optionally in conjunction with a porous tipping paper, to control and direct the flow of ambient air into the smoking article.

(22) The route taken by ambient air 20 under conditions of a higher strength of draw in the embodiment of FIG. 1 is illustrated in FIG. 3b. The valve 9 is opened as a result of the increased rate of air flow resulting from the stronger draw by the consumer, thereby allowing ambient air to pass through the proximal section of the sheath and into the mouth of the consumer without entering the smoking article.

(23) According to some embodiments, the valve is arranged so that the proportion of ambient air passing through the valve versus that entering the smoking article increases in proportion with the strength of draw. In other embodiments, the valve is essentially in either an open or closed position. The air flow rate is affected by the strength of the draw on the smoking article and sheath by the consumer. The draw creates pressure drop and when this pressure drop value exceeds a given threshold, the valve opens. In some embodiments the valve opens at pressure drop values above 10 cm/WG. Optionally the pressure drop value at which the valve opens is 15 cm/WG, 20 cm/WG, 25 cm/WG, 30 cm/WG, 35 cm/WG, 40 cm/WG.

(24) As illustrated in FIG. 3b, ambient air 21 is drawn into the sheath via the distal section 1 and passes through the gap 13 between the sheath 5 and the smoking article 7. In this scenario, however, due to the high strength of the draw by the consumer, the valve 9 is open and the ambient air 21 is able to continue through the proximal section of the sheath. This route through the sheath provides less resistance than the route through the smoking article and hence a higher proportion of the ambient air entering the sheath passes directly into the mouth, bypassing the smoking article entirely.

(25) An important advantage of the sheath described herein is that it both inhibits the occlusion of ventilation structures of the smoking article, and prevents excessive levels of combustion products from being inhaled as a result of the consumer increasing the strength of draw to overcome the effects of dilution of the gaseous smoke flow. As shown in FIG. 3b, increased strength of draw will simply result in the increased intake of ambient air. As a result, the smoke 22 inhaled as a proportion of the total volume will not be increased to the same extent as with a conventionally ventilated filter, and may in fact be reduced. In a conventional smoking article, the rate at which the smoke travels through the smoking article will be increased as the strength of draw is increased. This can have a detrimental effect on the efficacy of any filtration that the smoke undergoes. However, the addition of a sheath as described herein means that the rate at which the smoke travels through the smoking article will be largely unaffected by the strength of draw, leading to better filtration being observed at high draw strengths.

(26) In some embodiments the valve 9 comprises a plurality of sealing rings composed of a flexible material such as rubber. In other embodiments the valve comprises a sealing ring made up of several individual sections. The valve may also comprise a fine fibrous material such as a band of hair filaments, or the valve may comprise a series of one-way micro valves. In some embodiments the valve comprises more than one material, and may comprise a combination of two or more of the above valve arrangements.

(27) In some embodiments, the proximal section of the sheath includes one or more perforations situated further from the mouth end of the sheath than the valve. This permits the entry of a greater amount of air into the sheath, and this air is able to bypass the distal and central sections to immediately increase the pressure on the valve. In these embodiments the gaseous smoke flow from the smoking article is subject to a greater air dilution, particularly in the case of strong draws.

(28) The embodiment shown in FIG. 1 includes a central section 2, the function of which is to attach the sheath to the smoking article. This is achieved by means of the internal diameter of the central section being substantially equivalent to the diameter 15 of the smoking article 7. A tight binding may be achieved between the central section 2 of the sheath and the smoking article, to prevent their relative movement during the consumption of the smoking article. In the embodiment shown in FIG. 1, an adhesive is applied to the internal surface of the central section to permanently bind the sheath and smoking article. In alternative embodiments, other suitable methods of attachment are utilised to bind the sheath and smoking article.

(29) The central section 2 may be composed of a gas permeable material 11, in order to allow the ambient air to flow from the distal section to the proximal section of the sheath. Air is also able to pass from the porous material 11 of the central section into the filter tip of the smoking article 7. The precise nature of the gas permeable material may be chosen in order to provide different levels of gas permeability, thereby controlling the air flow through the sheath. A less porous material will encourage more of the ambient air to flow into the smoking article even when the route through the sheath is otherwise open. Thus, the porosity of this material will control the amount of ambient air entering the proximal section of the sheath and thus the mouth.

(30) In some embodiments the central section is composed of solid, impermeable material in which air passages are created.

(31) In some embodiments the sheath comprises a distal section and a proximal section with no central section. In these embodiments, the sheath may be held in place by an interference fit between the fins of the distal section and the smoking article. The longitudinal length of the fins and the number and circumferential arrangement of the fins can be selected to provide an adequate gripping function. If the fins are configured to be resilient, with a radial extent such as to provide a central space with a diameter slightly less than that of the diameter of the smoking article, the interference fit may be improved, with the fins deformed slightly as they hold the smoking article. Further, the fins need not be straight in the longitudinal direction, or aligned parallel with the longitudinal direction. Instead, they may be curved, or angled, or have some other non-linear shape, or be aligned at an angle or along a helix, which may be found to provide a more secure interference fit. Alternatively, if the inner ends of the fins have a sufficient surface area, the smoking article can be held inside the sheath by gluing to the fins.

(32) In other embodiments, the sheath comprises the central and proximal sections but lacks the distal section. Accordingly, ambient air is drawn into the sheath via the air permeable material of the central section. The central section may be air permeable, or alternatively, in the case that vent holes are provided in the outer wall of the sheath, the central section may comprise material that is impermeable.

(33) In some embodiments, the sheath comprises the distal and central sections 1 and 2, but does not have a proximal section. Clearly in this embodiment, the sheath functions to protect the ventilation means of the smoking article engaged within the sheath. In some of these embodiments the sheath is intended for retro-fit use, and may be reused repeatedly. Accordingly, the sheath of these embodiments may be retailed with smoking article in situ or may be retailed independently of the smoking article to enhance the ventilation and minimise the occlusion of standard smoking articles.

(34) A ventilating sheath according to the present invention may be used with tobacco rod-based smoking articles with a range of ventilation arrangements. Smoking articles having a conventional filter unit with one or more rings or zones of ventilation holes in the tipping paper have been discussed above. The shielding offered by the sheath allows the ventilation holes to be distributed over a wider area than is conventionally possible. A wide distribution of holes is likely to suffer at least partial blocking by the smoker in the absence of a ventilating sheath, thus reducing the ventilation below the intended level. The present invention offers the opportunity to use many more ventilation holes, or a conventional amount of holes distributed over a larger area, thus opening up a wider range of ventilation configurations that is currently feasible. The benefit is not limited to ventilation provided by rings or zones or holes, either. The tipping paper itself may be much more porous than conventional tipping paper. For a conventional design of filter-tipped smoking article, the tipping paper is substantially non-porous to make it robust enough to withstand finger and mouth contact during smoking. Hence, holes in the tipping paper are employed to provide ventilation. If a ventilating sheath is used instead, the finger and mouth contact is with the sheath rather than the tipping paper. This allows a porous tipping paper to be used, whereby air can enter the filter directly through the tipping paper. This offers different ventilation effects than can be achieved by ventilation holes alone, and also removes the need to make the ventilation holes. Also, a combination of ventilation holes and porous tipping paper may be used. Further, the ventilating sheath may be used with a non-filter-tipped smoking article that has ventilation means at or neat its mouth end, such as ventilation holes in the paper wrapper of the tobacco rod, or a porous paper wrapper at the mouth end. In summary, any smoking article having an air-permeable wrapper at its mouth end, whether the wrapper is related to a filter unit or not, may be used with a ventilating sheath according to the invention.

(35) In some embodiments the sheath is added during the manufacture of the smoking article. The sheath may be manufactured with the smoking article as a single article or the sheath and smoking article may be manufactured independently and joined in a final manufacturing step.

(36) The sheath may be manufactured by adhering the internal components to one side of a piece of flat material and then wrapping the material to form a substantially cylindrical shape. Alternatively, the sheath may be manufactured by pre-fabricating the material around a former. The sheath may be manufactured in discrete units, or longer sections comprising many sheath units may be produced and subsequently cleaved.

(37) In other embodiments, the sheath is attached to the smoking article by the consumer.