GB2135865A

GB2135865A - Tobacco smoke filter

Info

Publication number: GB2135865A
Application number: GB08305936A
Authority: GB
Inventors: Ernest Brian Hayes
Original assignee: Filtrona PLC
Current assignee: Essentra PLC
Priority date: 1983-03-03
Filing date: 1983-03-03
Publication date: 1984-09-12
Also published as: GB8305936D0

Abstract

A tobacco smoke filter comprising [i] an upstream section (13) comprising a tubular member (4) of low or zero air- and smoke-permeability around a central lower pressure drop smoke path (2); [ii] longitudinally contiguous therewith a downstream section (15) comprising an outer tubular portion (8) providing a low pressure drop path for ventilating air separated from a central smoke path (6); and [iii] a wrapper 10 around the upstream (13) and downstream (15) sections providing for the lateral ingress of external ventilating air therethrough into the said low pressure drop air path (8); one or both of the central smoke paths (2, 6) being effective to filter smoke passing therealong and the arrangement being such that at least the majority of the smoke stream passes along the central path (6) of the downstream section (15) and at least the majority of ventilating air passes along the low pressure drop path (8) of the down-stream section (13). <IMAGE>

Description

SPECIFICATION Tobacco smoke filter The present invention relates to tobacco smoke filters and provides such a filter comprising (i) an upstream section comprising a tubular member of low or zero air- and smoke-permeability around a central lower pressure drop smoke path; (ii) longitu dinally contiguous therewith a downstream section comprising an outer tubular portion providing a low pressure drop path for ventilating air separated (e.g.

by a sleeve, preferably an air-impermeable sleeve) from a central smoke path; and (iii) a wrapper around the upstream and downstream sections providing for the lateral ingress of external ventilat ing air therethrough into the said low pressure drop air path; one or both of the central smoke paths being effective to filter smoke passing therealong and the arrangement being such that at least the majority of the smoke stream passes along the central path of the downstream section and at least the majority of ventilating air passes along the low pressure drop path of the downstream section.

Preferably the sleeve is impermeable to air. Preferably all or substantially all of the smoke stream passes along the central path of the downstream section and all or substantially all of the ventilating air passes along the low pressure drop path of the downstream section.

The upstream section (i) may take a variety of forms; thus its central lower pressure drop smoke path may be an open unimpeded central channel surrounded by the tubular member, or it may be at least partly occupied - e.g. by a permeable smokefiltering plug extending fully or partly the length of the tubular member.The downstream section (ii) can also take a variety of forms; thus, subject to the proviso that one or both of the said central smoke paths is effective to filter smoke passing therealong, the central smoke path of the downstream section may be an open unimpeded central channel surrounded by the low pressure drop ventilating air path (e.g. surrounded by the mentioned sleeve) or it may be at least partly occupied, e.g. by a smoke filtering plug extending at least partly the length of the downstream section; the low pressure drop ventilating air path of the downstream section may be fully or partially filled by air permeable material extending at least partially the length of the section, or it could be an essentially open space provided and maintained by spacing means (e.g. a longitudinally corrugated permeable or impermeable wrap) disposed between the wrapper and the central smoke path (or sleeve). The wrapper may be a tipping overwrap joining the filter to a tobacco column in a filter cigarette, or it may be a wrapper which joins the upstream and downstream sections of the filter without extending beyond the upstream filter end; in the latter case, the wrapped filter might be incorporated in a filter cigarette by ring tipping or by a full tipping overwrap providing for ventilation into the outer tubular portion of the downstream filter section.

In use of the filter according to the invention, the ventilating air enters the outer tubular portion of the downstream filter section and flows therealong to the buccal end of the filter whilst smoke passes along the said central smoke path, the mixing of smoke and ventilating air within the filter being prevented or discouraged. To this end, the tubular member of the upstream filter section is preferably of equal or greater radial thickness than the outer tubular portion of the downstream section, blocking off the upstream end of the outer tubular portion of the downstream section.

The single Figure of the acompanying drawing is a schematic longitudinal sectional view to illustrate a variety of filters and filter cigarettes according to the invention. The single Figure shows a wrapped tobacco rod 16 joined by a full tipping overwrap 12 to a filter 11 having an upstream section 13 and a downstream section 15 joined by an air-permeable plugwrap 10. Upstream filter section 13 has an outer tubular member 4 of low or zero air- and smoke permeability around a central lower pressure drop smoke path 2. Downstream filter section 15 has an outer tubular portion 8 separated by sleeve 17 from a central smoke path 6. The tipping overwrap 12 has a circumferential ring of perforations 14 which provide in use for the ingress of external ventilating air through plugwrap 10 and into and then along the outer tubular portion 8 to the buccal end of the filter.

Variations of the illustrated arrangement are possible; thus when the tipping overwrap 12 is of inherently air-permeable material it need not have the perforations 14, and when tipping overwrap 12 is of inherently air-permeable material the plugwrap 10 (whether or not of inherently air-permeable material) could itself have perforations in register with the outer tubular portion 8 of downstream filter section 15. Although there will normally be a plugwrap 10 forming part of the filter 11 and longitudinally co-extensive with sections 13 and 15, it would be possible for it to be omitted, with sections 13 and 15 then being joined together and to wrapped tobacco rod 16by the tipping overwrap 12whichwould beof inherently air-permeable material and/or provided with perforations 14 in register with outer tubular portion 8 of filter section 15.When there is a piugwrap 10 forming part of filter 11 and joining sections 13 and 15 together (the plugwrap 10 being of inherently air-permeable material and/or having perforations in register with tubular portion 8), then the full tipping overwrap 12 could be dispensed with, the filter 11 being joined to wrapped tobacco rod 16 instead by ring tipping. Whatever the arrangement, there should be lateral ingress of external ventilating air only into the outer tubular portion 8 of downstream filter section 15; thus, where the wrapper or wrappers around tubular member 4 of upstream filter section 13 would otherwise provideforventilation into member 4 the latter should be sufficiently impermeable to prevent this.

The tubular member 4 of zero or low airpermeability is preferably of the same or (as shown) greater annular thickness than tubular portion 8 so as to block the upstream end of tubular portion 8 and hence prevent the passage of ventilating air from tubular portion 8 into the upstream filter section 13.

The central lower pressure drop smoke path 2 of upstream filter section 13 may be a void or may be a full- or part-length smoke filtering core of section 13.

Likewise the central smoke path 6 of downstream filter section 15 may be a void or a full- or part-length smoke filtering core, with the proviso that at least one of 2 and 6 provides a filtering effect on the smoke passing therethrough.

Outer tubular portion 8 of downstream filter section 15 could be a tubular member of smoke filtering material, and this might for example have peripheral grooves extending to the buccal end for receiving and transmitting ventilating air.

Where central smoke path 6 provides a smoke filtering core, and/or tubular portion 8 is a body of air-permeable material, the sleeve 17 may be omitted, but it is preferably present to ensure substantial separation of the ventilating air passing along portion 8 from the smoke passing along path 6.

When sleeve 17 is present (whether path 6 is a void or a smoke filtering body) it may be surrounded by spacing means (e.g. a longitudinally corrugated wrapper) spacing sleeve 17 from the ventilating outer wrapper and providing therebetween one or more channels for the longitudinal passage of ventilating air to the buccal end of the filter; indeed, sleeve 17 could itself be a corrugated tubular member surrounding path 6 and providing between itself and the ventilating wrapper channels for the passage of ventilating airto the buccal end of the filter.

The portions 8 and 6 (and 17 when present) of the downstream filter portion 15 may be as the corresponding items of the filters described and illustrated in our U.K. Patent Application No. 8210074; or as the corresponding items of those filters described and illustrated in our U.K. Patent Application No.

8219239 (Serial No. 2102271.A) in which peripheral ventilation air flow to the buccal end is substantially separated from central smoke flow.

Claims

1. A tobacco smoke filter comprising (i) an upstream section comprising a tubular member of low or zero air- and smoke-permeability around a central lower pressure drop smoke path; (ii) longitudinally contiguous therewith a downstream section comprising an outer tubular portion providing a low pressure drop path for ventilating air separated from a central smoke path; and (iii) a wrapper around the upstream and downstream sections providing for the lateral ingress of external ventilating air therethrough into the said low pressure drop air path; one or both of the central smoke paths being effective to filter smoke passing therealong and the arrangement being such that at least the majority of the smoke stream passes along the central path of the downstream section and at least the majority of ventilating air passes along the low pressure drop path of the downstream section.

2. A filter according to claim 1 wherein all or substantially all of the smoke stream passes along the central path of the downstream section and all or substantially all of the ventilating air passes along the low pressure drop path of the downstream section.

3. Afilter according to claim 1 wherein the central smoke path and low pressure drop path of the downstream section are separated by an airimpermeable sleeve.

4. A filter according to any preceding claim wherein the central lower pressure drop smoke path of the upstream section is an open unimpeded central channel surrounded by the tubular member.

5. Afilter according to any of claims 1 to 3 wherein the central lower pressure drop smoke path of the upstream section is at least partially occupied.

6. A filter according to claim 5 wherein the central lower pressure drop smoke path of the upstream section is effective to filter smoke passing therealong and the central smoke path of the downstream section is an open unimpeded central channel.

7. A filter according to any of claims 1 to 5 wherein the central smoke path of the downstream section is at least partially occupied.

8. A filter according to any preceding claim wherein the low pressure drop ventilating air path of the downstream section is fully or partially filled by air permeable material extending at least partially the length of the section.

9. A filter according to any of claims 1 to 7 wherein the low pressure drop ventilating air path of the downstream section is an essentially open space having spacing means disposed between the wrapper and the radially inner wall of the ventilating air path.

10. A filter according to any preceding claim wherein the wrapper joins the upstream and downstream sections without extending beyond the upstream filter end.

11. A filter according to any of claims 1 to 9 wherein the wrapper is a tipping overwrap joining the filter to a tobacco column in a filter cigarette.

12. A filter cigarette incorporating a filter accord ingto any of claims 1 to 10.

13. A tobacco smoke filter substantially as hereinbefore described with reference to the accompanying drawing.