GB2101466A

GB2101466A - Tobacco smoke filter

Info

Publication number: GB2101466A
Application number: GB08120813A
Authority: GB
Inventors: Stanley William Byrne
Original assignee: Filtrona PLC
Current assignee: Essentra PLC
Priority date: 1981-07-06
Filing date: 1981-07-06
Publication date: 1983-01-19

Abstract

This invention provides a filter having longitudinally spaced end faces and comprising a filtering core having longitudinally spaced core elements (2), and a plugwrap (6) around the core, the plugwrap where it surrounds said space (4) between core elements having at least one aperture (8) therethrough via which said space is in direct communication with the external air. <IMAGE>

Description

SPECIFICATION Tobacco smoke filter The present invention relates to tobacco smoke filters and provides such a filter having longitudinally spaced end faces and comprising a filtering core having longitudinally spaced core elements, and a plugwrap around the core, the plugwrap where it surrounds said space between core elements having at least one aperture therethrough via which said space is in direct communication with the external air.

The invention also provides a filtered cigarette comprising such a filter attached to a wrapped tobacco rod by a tipping overwrap providing in use for the passage of external ventilating air through the overwrap and said aperture or apertures into said space.

The plugwrap around the space between ccre elements could be provided with a single large aperture or a ring of circumferentially spaced large apertures, the or each such aperture for example extending half or even the whole length of the space between the core elements. Such apertures might be circular or square, or could be elongate with a major axis extending longitudinally of the filter. In these cases the tipping overwrap of a filtered cigarette according to the invention suitably has ventilation perforations therethrough at least some of which are in register with a plugwrap aperture.

Filters according to the invention are suitably made by continuously advancing longitudinally a strip of the said plugwrap having said apertures spaced longitudinally therealong, continuously depositing longitudinally spaced core elements on the advancing plugwrap with said apertures in the spaces between core elements, continuously enwrapping the plugwrap around the core elements to form a continuous rod, and severing this rod laterally through core elements to form finite rod lengths.These initially produced lengths are usually of multiple (e.g. sextuple) length compared to that of the eventual individual filter; these multiple length rods are subsequently cut into double lengths, each of which is joined at opposite ends to respective wrapped tobacco rods by the tipping overwrap, the resulting composite then being cut through its centre to provide two filtered cigarettes according to the invention.

Adjacent core elements of the filter according to the invention may be the same or different and can be of any of a variety of materials and forms suitable for use in tobacco smoke filters. Adjacent spaced core elements may for example be of different pressure drop and in this case, in a filtered cigarette according to the invention, the higher pressure drop element may be towards to the tobacco rod with the lower pressure drop element towards the buccal end. The core elements can for example be selected from unwrapped bodies of bonded filamentary tow (e.g.

cellulose acetate) or staple fibre, wrapped tow or staple fibre bodies, etc. One of a pair of spaced core elements may be tubular and/or externally grooved longitudinally to provide for by-pass of smoke therethrough or therearound. In the latter cases, the said one core element need not be of filtering material, but could instead be smokeimpermeable.

The invention is illustrated, by way of example, in the accompanying drawings, in which: Figure 1 is a fragmentary perspective view of a sextuple length filter rod according to the invention; Figure 2 is a similar view of an individual cigarette filter according to the invention; and Figure 3 is a longitudinal sectional view of a filtered cigarette according to the invention.

The rod illustrated in Fig. 1 consists of spaced plugs 2 of smoke filtering material separated longitudinally by empty spaces 4, the plugs 2 being held in rod form by a plugwrap 6 secured conventionally by a lapped and stuck seam, plugwrap 6 having large apertures 8 therethrough where it surrounds the spaces 4. In this embodiment, there is one aperture 8 for each space 4, but a number of apertures 8 could be disposed circumferentially around each space 4.

The Fig. 1 rod is cut from a continuously produced rod and then cut transversely through plugs 2 into double lengths which are employed in the formation of filtered cigarettes as previously described. The individual filter lengths obtained from the continuous rod and employed in filtered cigarettes will usually have just two plugs 2 separated by a space 4; these plugs in the eventual individual filter lengths will of course be shorter than those in the original continuous rod; frequently, in the continuous rod, adjacent plugs will be of the same length and uniformly spaced, and will be transversely severed centrally to yield symmetrical individual filter lengths in which the plugs are each half the length of those in the original continuous rod, but it is of course possible for adjacent plugs in the continuous rod and/or in the eventual individual filters to be of different lengths.

An individual filter according to the invention is shown in Fig. 2. This is of essentially the same structure as one cut from the Fig. 1 rod except that the plugwrap 6 has a series of elongate apertures 8 around each space 4.

Figure 3 illustrates a filtered cigarette in which a filter of the type shown in Fig. 2 is attached to a wrapped tobacco rod 10 by a tipping overwrap 12 which is of air-impermeable material having a circumferential ring of perforations 14, at least some of perforations 1 4 and apertures 8 being in register.In this particular embodiment the plug 2 adjacent to the tobacco rod is of relatively high pressure drop whilst the other plug 2 is of relatively low pressure drop; the difference in pressure drop between adjacent plugs can be due to their being of different materials and/or structure and/or to their being of different lengths; the higher pressure drop plug need not be of filtering material, but could for example be a body of smoke-impermeable material having one or more external longitudinal grooves and/or internal passages for the passage of smoke therepassed or therethrough. Such filters are cut from continuously produced rods of the type discussed in connection with Figs. 1 and 2 where adjacent plugs differ.

Other shapes and arrangements of aperture(s) 8 are of course possible which allow for the achievement of air-flow communication between space 4 and the ventilation perforations of a tipping overwrap without registration problems.

Claims

1. A filter having longitudinally spaced end faces and comprising a filtering core having longitudinally spaced core elements, and a plugwrap around the core, the plugwrap where it surrounds said space between core elements having at least one aperture therethrough via which said space is in direct communication with the external air.

2. A filter according to claim 1 having a plurality of apertures through the plugwrap around each space.

3. A filter according to claim 1 or 2 wherein adjacent core elements differ.

4. A filtered cigarette comprising a filter according to any of claims 1 to 3 attached to a wrapped tobacco rod by a tipping overwrap providing in use for the passage of external ventilating air through the overwrap and said aperture or apertures into said space.

5. A tobacco smoke filter substantially as hereinbefore described with reference to Fig. 1 or 2 or 3 of the accompanying drawings.

6. A filtered cigarette substantially as hereinbefore described with reference to Fig. 3 of the accompanying drawings.