# US 4,393,885 A · Cigarette filter

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- Number: US 4,393,885 A
- Document ID: US4393885A
- Status: Granted
- Kind: A
- Application number: 06/303,756
- Filed: 1981-09-21
- Granted: 1983-07-19
- Earliest claimed: 1981-09-21
- Assignees: Brown & Williamson Tobacco Corporation
- Inventors: Donald A. Silberstein
- Web page: https://patentgrep.com/patent/US4393885A

## CPC

- A24D 3/04: Tobacco smoke filters characterised by their shape or structure
- A24D: CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES OF CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES

## Abstract

A filter for a cigarette has a porous filter rod with a channel extending longitudinally through the filter rod. The end of the channel at the tobacco column of the cigarette is closed by a smoke impervious wall having an orifice therein of a smaller cross-sectional area than the cross-sectional area of the channel to provide flow communication between the tobacco column and the channel. The filter rod can be circumscribed with an air pervious tipping material.

## Claims

### Claim 1

A filter for a cigarette, comprising:
a first longitudinally extending cylindrical chamber;
a second longitudinally extending cylindrical chamber disposed within the first chamber with a spacing between the outer wall of the second chamber and the inner wall of the first chamber, the wall of the second chamber being air impervious;
transversely disposed smoke impervious partition means disposed at the end of the chambers interfacing with a tobacco column of the cigarette; and,
means defining at least one orifice through said smoke impervious partition means for providing direct flow communication between the tobacco column of the cigarette and the interior of said second chamber whereby no smoke comes in contact with the exterior of said second chamber, the at least one orifice having a smaller cross-sectional area than the cross-sectional area of the second chamber, said first and second chambers being of substantially the same length with their ends being transversely aligned.

### Claim 2 (depends on 1)

The filter of claim 1, wherein said second chamber is defined by a hollow tube fabricated of gas impervious material.

### Claim 3 (depends on 1)

The filter of claim 1, wherein said second chamber and said orifice are coaxially disposed.

### Claim 4 (depends on 1)

The filter of claim 1 including a porous filter rod in the annulus defined by the spacing between the walls of the first and second chamber.

### Claim 5 (depends on 4)

The filter of claim 4, further comprising an air impervious tipping paper circumscribing said porous filter rod defining said first chamber.

### Claim 6 (depends on 4)

The filter of claim 4, further comprising an air pervious tipping paper circumscribing said porous filter rod defining said first chamber.

### Claim 7 (depends on 1)

The filter of claim 1, further comprising means adding surface area of said second chamber for collecting particulate matter from the tobacco smoke flowing through said channel means.

### Claim 8 (depends on 7)

The filter of claim 7, wherein said means adding surface area comprises a plurality of projections extending into said second chamber.