GB2127669A - Improvements relating to smoking article filters - Google Patents

Abstract

In a method of modifying tobacco-smoke filter rod, a rod of tobacco-smoke filter material comprising fibrous filter material wrapped in a wrapper of thermoplastic film material and a heated forming means are moved relatively to and in contact with each other to cause a portion or portions of said film wrapper to be removed. Also with a filter element comprising fibrous tobacco-smoke filtration material wrapped in a wrapper of thermoplastic film material, a portion or portions of said film wrapper are removed by moving said filter element and a heated forming element relatively to and in contact with each other. Smoking articles comprising such wrapped rods of filter element attached to tobacco rods are also described. Removal of a portion or portions of film-material wrapper exposes either said filtration material or a further wrapper intermediate said film- material wrapper and said filtration material. Filtration material exposed by said removal of a portion or portions of film material may not be sealed by the action of the heat of the forming means. <IMAGE>

Description

SPECIFICATION Improvements relating to smoking article filters This invention relates to filters for smoking articles, cigarettes for example.

It is common in present day filter-tipped cigarettes for the filter to comprise a filter element of fibrous filtration material, cellulose acetate for example, wrapped in air-permeable plugwrap paper and for a low permeability tipping serving to interattach the filter element and the cigarette rod to be provided with a zone of ventilation perforations. When, during the smoking of a cigarette possessing these features, ventilation air is drawn into the filter element through the ventilation perforations in the tipping, the air encounters the plugwrap before the air enters the body of filtration material. The plugwrap not only presents a degree of resistance to air flow, albeit a comparatively small one, but it also acts to restrict a free distribution of the ventilation air entering the filtration material.

It is an object of the present invention to make possible a more direct and better distributed flow of ventilation air into wrapped filter elements.

The present invention provides a method of modifying tobacco-smoke filter rod, wherein a tobacco-smoke filter rod comprising fibrous filtration material wrapped in a wrapper of thermoplastic film material and heated forming means are moved relatively to each other and in contact with each other to cause a portion or portions of the film wrapper to be removed. This method may be utilised in primary production of filter rod or in the course of treatment thereof.

The present invention also provides a filter element comprising fibrous filtration material wrapped in a wrapper of thermoplastic film material, a portion or portions of said film wrapper having been removed by moving said element and heated forming means relatively to each other and in contact with each other.

The present invention further provides a smoking article, a cigarette for example, comprising a wrapped rod of smoking material, a filter element and a tipping serving to interattach said rod and said filter element, said filter element comprising fibrous filtration material wrapped in a wrapper of thermoplastic film material, a portion or portions of which film wrapper having been removed by moving said element and heated forming means relatively to each other and in contact with each other, the said removal of said portion or portions of film wrapper providing ventilation-air distribution space or spaces bounded by said tipping, which permits ingress of ventilation air into said space or spaces.

The removal of the portion or portions of film wrapper may expose either the underlying filtration material or a further wrapper intermediate the film wrapper and the filtration material.

The present invention is based on the discovery that by moving filter rod of fibrous filtration material, of which the wrapper or the outermost wrapper is formed not of paper but of thermoplastic film, in contact with a heated former of suitable depth, a portion or portions of the wrapper may thereby be removed. If the underlying filtration material is exposed by the removal of the film wrapper, the exposed filtration material is not sealed by the contact of the rod with the heated forming means. Moreover, the edges of the remaining portions of the film wrapper which bound the areas previously occupied by the removed portion or portions are sharp. Indeed the product of the process is much akin to that which would have resulted from cutting out the portion or portions of the wrapper using a sharp blade.

The thermoplastic film wrapper is suitably of a cellulose acetate film material, although other thermoplastic film materials, such as polyethylene, PVC, polypropylene and polyester, will occur to those skilled in the art. The film wrapper may be composed of a blend or laminate of more than one thermoplastic material. The thickness of the film wrapper is conveniently 0.1 to 0.5 mm.

The film wrapper may be seam sealed using a conventional plugwrap sealant or a suitable solvent. Thus if the wrapper is of cellulose acetate, use may be made as solvent of seam-sealant ethyl acetate, acetone or triacetin.

Fibrous filtration material underlying the thermoplastic film wrapper may, for example, be cellulose acetate, polypropylene or polyethylene.

Advantageously a plurality of portions of the thermoplastic film wrapper removed by contact with a heated forming means extend along the filter rod or element such that in a smoking article in accordance with the invention, ventilation air enters the ventilation-air distribution spaces at a first location, flows through the spaces, and enters the body of filtration material at a second location spaced longitudinally of the filter element from the first location.

Conveniently in carrying out the inventive method a filter rod and heated forming means are moved relatively of each other in an arcuate path, in a direction transverse the longitudinal axis of the rod, although a straight path of relative movement would also be appropriate.

In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 shows parts of a filter tipped cigarette in axial section, Figure 2 shows an exterior view of the filter element of the cigarette of Figure 1, Figures 3-6 show respective filter elements each of which could be substituted for the filter element of the cigarette of Figure 1; and Figure 7 shows a mouth-end view of the filter of Figure 5.

The filter tipped cigarette of Figure 1 comprises a cigarette rod 1, of tobacco filler 2 wrapped in a cigarette paper wrap 3, a filter element 4, of fibrous cellulose acetate filtration material 5 wrapped in transparent cellulose acetate film plugwrap 6, and a paper tipping wrapper 7 serving to interattach the cigarette rod 1 and the filter element 4.

Prior to being incorporated in the cigarette of Figure 1 the filter element 4 formed part of a filter rod of a length equivalent to, for example, six unit elements. The rod was rolled in contact with a heated former (not shown) of such configuration as to effect removal of an annular strip of the plugwrap 6, without causing sealing, or any significant sealing, of the thus exposed filtration material 5. The space initially occupied by the removed strip of plugwrap provides a ventilationair distribution space in the form of an annular groove 8. The tipping wrapper 7 is provided with a ring of ventilation perforations 9 which communicate with the groove 8.Thus ventilation air entering the groove 8, during smoking of the cigarette, is distributed over the total area of the underlying filtration material 5 bounding the groove 8 and enters the element 4 unimpeded by an intermediate layer of plugwrap.

A form of filter element 1 0 alternative to the element 4 of Figures 1 and 2 is shown in Figure 3.

The filter element 10 comprises a thermoplastic film material plugwrap 11 which has been rolled in contact with a heated former (not shown) to produce an annular groove 12 the base 13 of which is constituted by the peripheral surface of a body of fibrous filtration material enwrapped by the plugwrap 11. Extending along the element 10 from the downstream side of the groove 12 to locations short of the mouth end of the element 10, the right-hand end viewing Figure 3, are a number of further grooves 14. The grooves are equiangularly spaced about the element 10 and extend parallel to the axis of the element 10.

When the filter element 10 is attached to a cigarette rod by tipping having ventilation perforations in communication with the annular grooves 12, and the resultant cigarette is smoked, ventilation air enters the grooves 14 and enters the interior of the element 10 over an extended peripheral area thereof. A proportion of the ventilation air will travel along the full length of each of the grooves 14 before entering the body of fibrous filtration material within the plugwrap 11.

As will be appreciated by those skilled in the cigarette filter art, the widths of the grooves will be dimensioned taking pressure drop considerations into account.

The grooves 14 of the elements 10 may be formed simultaneously with the annular groove 12, using an appropriately shaped heated former, or in a separate step using a separate heated former. The removal of portions of plugwrap 11 to form the grooves 12 and 14 does not result in any sealing, or any significant sealing of the surface fibres of the body of filtration material.

Filter element 1 5 of Figure 4 is similar to that of Figure 3 excepting that, instead of there being a series of straight grooves running from an annular groove, from an annular groove 1 6 there are two series of grooves 17, 18 which follow the helical paths of opposite hand. Although the formation of the grooves 17, 1 8 by the thermal removal of thermoplastic film plugwrap results in the production of small isolated triangular and diamond portions of the remaining plugwrap, these portions are firmly secured to the underlying body of filtration material because the margins of these portions become thermally bonded to the filtration material during the thermal formation of the grooves 17, 1 8.

An apparatus of a type which could be utilised for the purpose of removing portions of thermoplastic film plugwrap is described in United Kingdom Patent Specification No. 1 ,507,765.

Filter element 19 of Figure 5 comprises a thermoplastic film wrapper 20, fibrous filtration material 21, and a further wrapper 22 intermediate the wrapper 20 and the filtration material 21. A six times unit length filter rod from which the element 1 9 was cut was rolled in contact with a heated former of such configuration as to remove portions from wrapper 20 to provide an annular groove 23 and extending therefrom, a number of Y-form grooves 24, only one of which is shown. The grooves 23 and 24 are not so deep as to extend through the wrapper 22. The wrapper 22 is provided with a ring of ventilation perforations 25 at a distance along the element 1 9 such that they are disposed at a right-hand end region, as viewing Figure 5, of the Y-form grooves 24.The size and spacing of the perforations 25 is such that at least one perforation communicates with each of the two divergent limbs of each of the grooves 24.

When the filter element 1 9 is attached to a cigarette rod by tipping having ventilation perforations in communication with the annular groove 23, ventilation air can flow from the groove 23 along the grooves 24 and then into the body of filtration material 21 through the ventilation perforations 25.

The wrapper 22 may be of conventional paper plugwrap material but is suitably of a paper containing thermoplastic fibres or is a thermoplastic film material. The wrapper 22 may be of low or substantially zero air permeability.

Filter element 26 of Figure 6 comprises a thermoplastic film wrapper 27 which has heat formed in it an annular groove 28 and, extending from the groove 28, a number of grooves 29. The configuration of the grooves 28, 29 is similar to that of the grooves 12, 14 of the filter element 10 of Figure 3. However, whereas the bases of the grooves 12, 14 are constituted by the peripheral surface of a body of fibrous filtration material, the bases of the grooves 28, 29 of the element 26 are constituted by a further wrapper 30. Before the film wrapper 27 was applied over the wrapper 30 in the manufacture of the element 26, a strip of the wrapper 30 was removed to provide an annular groove 31. The base of the groove 31 is constituted by the peripheral surface of a body of fibrous filtration material enwrapped by the wrapper 30. In the completed element 26 the exposed portion of the filtration material intersects end zones of the grooves 29 in the wrapper 27.

When the filter element 26 is attached to a cigarette rod by tipping having ventilation perforations in communication with the annular groove 28, ventilation air can flow from the groove 28 along the grooves 29 into the annular groove 31, from which last mentioned groove the air passes into the body of filtration material.

The wrapper 30 is preferably of low or substantially zero air permeability. Whether the wrapper 30 is of conventional paper plugwrap material or is of a thermoplastic nature, the annular strip thereof removed to provide the groove 31 may be removed by contact with a heated former prior to the application of the wrapper 27 over the wrapper 30.

Claims (7)

1. A method of modifying tobacco-smoke filter rod, wherein a rod of tobacco-smoke filter material comprising fibrous filter material wrapped in a wrapper of thermoplastic film material and a heated forming means are moved relatively to and in contact with each other to cause a portion or portions of said film wrapper to be removed.

2. A filter element comprising fibrous tobaccosmoke filtration material wrapped in a wrapper of thermoplastic film material, a portion or portions of said film wrapper having been removed by moving said filter element and a heated forming element relatively to and in contact with each other.

3. A smoking article comprising a wrapped rod of smoking material, a filter element comprising fibrous smoke filtration material wrapped in a wrapper of thermoplastic film material and a tipping wrapper serving to interattach said rod and filter element, a portion or portions of said filmmaterial wrapper having been removed by moving said element and a heated forming means relatively to and in contact with each other to provide a ventilation-air distribution space or spaces bounded by said tipping wrapper which permits ingress of ventilation air into said space or spaces.

4. A smoking article according to claim 3, wherein removal of said portion or portions of film-material wrapper exposes either said filtration material or further wrapper intermediate said filmmaterial wrapper and said filtration material.

5. A filter element or smoking article according to one of the preceding claims, wherein filtration material exposed by said removal of a portion or portions of film material is not sealed by the action of heat of the forming means.

6. A method of producing or modifying tobacco-smoke filter rod substantially as hereinbefore described with reference to the accompanying drawings.

7. A filter element or smoking article produced substantially as hereinbefore described.