GB2105171A - Plugwrap - Google Patents

Abstract

This invention provides a strip of cigarette filter plugwrap material having a regular array of apertures therein which are so shaped and so overlap in staggered rows perpendicular to the longitudinal axis of the strip and staggered columns parallel to the said axis that the total length of void transversed by any two lines extending the maximum width of the strip perpendicular to the said axis is the same. <IMAGE>

Description

SPECIFICATION Plugwrap The present invention relates to a cigarette filter plugwrap and to cigarette filters provided with such plugwrap. According to the invention a strip of cigarette filter plugwrap material has a regular array of apertures therein which are so shaped and so overlap in staggered rows perpendicular to its longitudinal axis and staggered columns parallel to the said axis that the total length of void traversed by any two lines extending the maximum width of the strip perpendicular to the said axis is the same.

The invention also provides a cigarette filter comprising a core wrapped in a plugwrap having a regular array of apertures so shaped and overlapping in staggered rows and columns extending respectively circumferentially and longitudinally of the filter that the resistance provided by unit length of the plugwrap to flow of air therethrough into the fore is constant over the length of the filter.

The invention also provides a filtered cigarette having a filter as defined above attached to a wrapped tobacco rod by a smoke-permeable and /or perforate tipping overwrap.

The laterally outermost apertures of the array at alternate ends of adjacent rows, will usually correspond to a portion only of the width of the more inboard apertures, but apart from this the apertures of the plugwrap generally each have an axis of symmetry parallel to the said axis of the strip; they are suitably of hexagonal shape (and part hexagonal in the case of said outermost apertures) and disposed over the plugwrap in a nesting arrangement so that an apex of one hexagonal aperture overlaps precisely with apices ofadjacentapertures in the next row. The maximum aperture lenth (paralleltothe said axis) will be constant in a row but may vary from row to row.

In filtered cigarettes according to the invention, the tipping overwrap preferably has perforations which are smail in comparison to the size of the plugwrap apertures; forexamplethetipping overwrap perfora tions are suitably of .01-0.5 mm diameter with the hexagonal plugwrap holes being about 2.5 mm wide; the aperture length is not critical.

The material of which the plugwrap is constructed is preferably itself smoke-impermeable, so that the air permeability ofthe plugwrap is provided solely by the apertures or perforations therethrough.

In one embodiment of a cigarette filter and filtered cigarette according to the invention, the core around which the plugwrap is secured is a composite of two or more plugs of different filtering characteristics in which adjacent plugs may abut end to end or be spaced longitudinallyto leave a cavitytherebetween.

Thus one plug of the composite core may be of rela tively high pressure drop and another relatively low pressure drop. Where such high and low pressure drop plugs of the core abut end to end, the perforations in the tipping overwrap are preferably disposed around the low pressure drop plug. Where filter plugs of a composite core are spaced apart, the perforations in the tipping overwrap are preferably disposed around the gap between them.

In other embodiments, the core enwrapped by the plugwrap may be a composite of a plug and a tubular member; here again the two components of the composite core may abut end to end or may be spaced apart. In the latter case, the perforations in the tipping overwrap are preferably around the space between plug and tubular member; in the former case, the tubular member is preferably of airpermeable material with the perforations in the tipping overwrap being around this tubular member and/or around the junction between the plug and tubular member.

In the above embodiments employing a composite core, one core element (usually the higher pressure drop element) can be of impermeable or very low permeability material provided with internal and/or external channels for the longitudinal passage of smoke therethrough and/or therepast - e.g. it could be externally fluted and/or have a central bore for this purpose.

The invention is illustrated, by way of example only, in the accompanying drawings, in which like reference numerals indicate like parts and in which: Figure lisa plan view of a strip of plugwrap according to the invention; Figure 2 illustrates similarly a modification of the Figure 1 plugwrap; and Figures 3, 4 and 5 are longitudinal sectional views of cigarette filters according to the invention incorporated in filtered cigarettes according to the invention.

The plugwrap of Figure 1 comprises a 27 mm wide web 2 of air-impermeable material -e.g. plastics such as polyethylene, or air-impermeable paper-pro- vided with a regular array of overlapping apertures 4 arranged in staggered rows and columns. The apertures 4 are of symmetrical hexagonal shape, apart from the part-hexagonal ones 5 at the ends of alternate rows, and nest with one another uniformly in the manner indicated. In one such plugwrap according to the invention each hexagonal aperture 4 has sides A 2.2 mm long, sides B 2 mm long, an included angle between sides B of 64", with lateral spacings D between apertures of a row being 3 mm and the plain edge strips 7 being of equal width.With the illustrated arrangement of apertures, any line extending the maximum plugwrap width perpendicular to the longitudinal axis of the plugwrap traverses the same length of void, so that the air-permeability of the plugwrap is constant overthe whole of its length. The Figure 2 plugwrap is the same except that the aperture apices are rounded for ease of manufacture, and that it has no plain edging strips - or only one (not shown).

In Figures 3 to 5, a plugwrap 6 as illustrated in Figure 1 or 2 is shown wrapped around a filter core 8, the plugwrap in turn being enwrapped in a perforate tipping material 10 which is a tipping overwrap connecting the filter to a wrapped tobacco rod 9.

In Figure 3, the core8 is made up of a high pressure drop plug 12 spaced from a low pressure drop plug 14 by a cavity 16, the perforations 18 in the tipping overwrap being disposed in a circumferential ring around the cavity.

Figure 4shows another embodiment in which high and low pressure drop plugs 12 and 14 constituting the core 8 abut end to end, the perforations 18 in the tipping overwrap extending in a circumferential ring around the low pressure drop plug.

In Figure 5, the core 8 of the filter is made up of a high pressure drop plug 12 and a tubular member 22 of smoke-permeable material, the perforations 18 in the tipping overwrap being disposed in a circumferential ring around the tubular member. Ina modification of the Figure 5 embodiment, the high pressure drop plug and the tubular member may be spaced longitudinally, with the tipping overwrap perforations being disposed in a ring about the gap between the two.

In each of Figures 3 to 5, the high pressure drop plug 12 is of filtering material and is of circular section conforming to that of plugwrap 6. Plug 12 could instead have one or more external longitudinal grooves to provide one or more smoke passages between itself and the plugwrap (e.g. it could be externally fluted longitudinally), and in these cases it could be offiltering or ofsmoke-impermeable material. Indeed any high pressure drop generating element may be employed for plug 12.

In the described embodiments, the plugwrap 6 is secured around the core by means of a lapped and stuck seam; the latter is achieved more easily and reliably when the plugwrap is ofthetype illustrated in Figure 1, with plain edge strips 7.

Whilstthe plugwrap 6 has been described above as used in ventilated filters, it can in fact be used on all manner of filter cores in filters which may be ventilated or not. A plugwrap according to the invention could also be used as a tipping overwrap joining to a wrapped tobacco rod a filter having a perforate or air-permeable wrapper.

The array of apertures will usually extend across the full width of the plugwrap according to the invention, apart from any plain edging strip facilitating formation of a lapped seam, but this is not essential.

The apertures will usually occupy a substantial proportion of the overall plugwrap area, e.g. 25 or 50% or more.

In ventilated filters according to the invention employing longitudinally spaced or abutting relatively high and relatively low pressure drop elements in the core, the former may be positioned downstream of the latter- e.g. in Figu res 3 to 5 the core plugs may be reversed, with plug 12 to the buccal end. Such filters can give good CO reduction in the delivered smoke (for the given degree of air dilution concerned) without undue reduction in the delivery of taste components.

Claims (12)

1. Astrip of cigarette filter plugwrap material having a regular array of apertures therein which are so shaped and so overlap in staggered rows perpendiculartothe longitudinal axis ofthe strip, and staggered columns parallel to the said axis that the total length ofvoidtraversed by any two lines extending the max- imum width ofthe strip perpendiculartothe said axis is the same.

2. A cigarette filter comprising a core wrapped in a plugwrap having a regular array of apertures so shaped and overlapping in staggered rows and columns extending respectively circumferentially and longitudinallyofthefilterthatthe resistance provided by unit length of the plugwrap to flow of air therethrough into the core is constant over the length of the filter.

3. A filter according to claim 2 wherein the core comprises a composite of at least two longitudinally abutting elements.

4. A filter according to claim 2 wherein the core comprises a composite of at least two longitudinally spaced elements.

5. Afilter cigarette comprising afilter according to claim 2,3 or 4 attached to a wrapped tobacco rod by a smoke-permeable and/or perforate tipping overwrap.

6. A filter cigarette comprising a filter according to claim 3 or 4 attached to a wrapped tobacco rod by a smoke-permeable and/or perforate tipping overwrap, said elements comprising an upstream element of relatively high pressure drop and a downstream element of relatively low pressure drop and the tipping overwrap providnig for entry of external ventilating air into the filter downstream of said upstream element.

7. A ventilated filter according to claim 3 or 4 whose core has a relatively high pressure drop element downstream of a relatively low pressure drop element.

8. An article according to any preceding claim wherein the plugwrap apertures are hexagons or part hexagons having axes parallel to the columns and disposed with apices nesting.

9. An article according to any preceding claim wherein the material of the plugwrap is airimpermeable.

10. Cigarette filter plugwrap substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.

11. A filter substantially as hereinbefore described with reference to Figure 3 or Figure 4 or Figure 5 of the accompanying drawings.

12. A filter cigarette substantially as herein before described with reference to Figure 3 or Figure 4 or Figure 5 of the accompanying drawings.