IE53814B1 - Cigarette filter - Google Patents

Description

This invention relates to a filter for cigarettes. In one aspect it relates to a filter with novel ventilating means. In another respect the invention relates to a filter for a cigarette having flow directing grooves formed therein for directing ventilating air to the mouth end of the filter and concurrently delivering diluted smoke through the filter to the mouth end oE the filter.

It is well known in the art to add to cigarettes filters provided with ventilation means to bring ambient air into the filters to dilute the smoke stream passing therethrough. The dilution of the smoke stream reduces the quantity of smoke particulates as well as the gas phase components which are delivered to the smoker’s mouth. A number of means have been proposed and are utilised for introducing ventilating air into the cigarette. For example, the wrapper for the tobacco in a cigarette can be made from a porous material which allows for introduction of air along the entire length of the cigarette where it mixes with the smoke stream passing therethrough, thereby diluting the smoke in the stream. Also the cigarette wrapper may be perforated at selected locations along the length of the cigarette which provides ports in the cigarette through which ventilating air enters. Even further, it is known to perforate the wrapper of the filter on the cigarette to allow ventilating air to enter the filter and dilute the smoke stream. There have also been a number of suggestions for incorporating grooves within the filter of a filter cigarette to facilitate the addition of ventilating air into the smoke stream.

For example, U.S. Patent No. 3,596,663 relates to a tobacco smoke filter provided with a corrugated porous plug wrap surrounding a filter element which is circumscribed by tipping paper having flow-through perforations. The ventilating air enters into the filter element and the grooves through the perforations in the tipping paper and progresses to the smoker's mouth. And, U.S. Patent No. 4,256,122 teaches a filter for a cigarette which includes grooves extending longitudinally along the outer surface of a filter rod circumscribed by a non-porous plug wrap and the rod and wrap are enclosed with ventilating tipping paper so that in use only ventilating air travels down the grooves and only smoke travels through the filter. Other patents which relate to cigarette filters having grooves circumscribing the filter element for the introduction of ventilating air into the cigarette filter include U.S. Patent No. 3,577,995; U.S. Patent No. 3,572,347; U.S. Patent No. 3,490,461; U.S. Patent No. 3,788,330; U.S. Patent No. 3,773,053; U.S. Patent No. 3,752,165; U.S. Patent No. 3,638,661; U.S. . Patent No. 3,608,561; U.S. Patent No. 3 ,910,288 and U.S. Patent No. 4,256,122. The present invention advantageously provides a straight forward arrangement of a filter for a cigarette which in one form achieves essentially normal cigarette pressure drop with low to moderate efficiency filters.

The present invention seeks to provide a cigarette filter for lowering tar predominantly by ventilation while also providing filtration of the tobacco smoke, and also to provide a filter ventilation system for a cigarette utilizing grooves in the filter plug extending from the ventilating air perforations in the tipping paper to the mouth end of the filter.

More particularly the present invention provides a filter for a cigarette comprising: a porous filter rod of generally cylindrical configuration; a wrapper extending longitudinally along said, filter rod from one end thereof to the other end and circumscribing said rod leaving flow-through opposed ends of said filter rod; said wrapper being formed with a plurality of grooves spaced from each other circumferentially of, ana embedded into, said filter rod, said grooves being open at the ncuth end of said filter rod and extending therefrom in a generally longitudinal direction of said filter rod to a closed end for a distance less than the length of said filter rod; the embedded walls of said grooves defined by said wrapper material being impermeable to air and smoke, and the portion of said wrapper between adjacent grooves being impermeable to air, said wrapper upstream of the closed ends of the grooves being permeable to air; and tipping material extending longitudinally of and circumscribing said wrapper filter rod, said tipping material being air permeable, permitting, ventilating air flow therethrough into said grooves, and also per25 mitting air flow therethrough into said filter rod through said permeable portion of said wrapper to co-mingle with and dilute smoke flowing through said filter rod from one end to the other.

These and other features of the present invention will become even more clear upon reference to the following description and in conjunction with the accompanying drawing which illustrates a perspeccive view of a cigarette incorporating a filter construction in accordance with the present invention.

A cigarette filter 110 is shown as comprising a generally cylindrically shaped filter rod 112 and a circumscribing wrapper 114. The wrapper 114 extends longitudinally along the filter rod 112 from one end 116 of the filter rod 112 to the other end 118 thereof so that the filter rod ends 116 and 118 are in mutual flow through relationship.

The filter rod 112 is fabricated of a porous material such as for example, fibrous or foamed cellulose acetate or any other material suitable for filtering cigarette t smoke. A plurality of grooves 120 are formed in the wrapper 114 and embedded into the filter rod 112. Each groove 120 is open at one of its ends 122 to the mouth end 116 of the filter rod 112 and extends therefrom in a generally longitudinal direction of the filter rod 112 for a distance less than the length of the filter rod.

In the filter construction 110 not only are the embedded portions of the wrapper 114 defining the walls of the grooves 120 impermeable to air, but the peripheral areas of the wrapper 114 between the grooves 120 are also impermeable to air. However, portion 123 of the wrapper 114 upstream, relative to the direction of the smoke flow through the filter from the filter end 118 to 116, of the closed ends of the grooves 120 is permeable to air. This construction can be accomplished by, for example, fabricating the wrapper 114 of an air impermeable material such as a closed cell cellulose acetate and forming small apertures in the area of the wrapper upstream of the closed ends of the grooves 120. Alternatively, for example, the wrapper 114 can be fabricated entirely of an air permeable material and only the walls of the grooves and peripheral areas of the wrapper 114 between the grooves treated or coated to render them air impermeable, leaving the portion 123 upstream of the closed ends of the grooves untreated and, therefore, air permeable. One such treatment is to, tor example, apply heat to the wrapper material to heat seal the porous material. Another effective treatment is to coat the embedded portions of the wrapper 114 defining the walls 120 with a chemical such as a water insoluable solution or material, for example ethylcelluiose, or a water-soluable material such as, for example sodium carboxymethylcellulose or methylcellulose which seals the pores.

The filter construction 110 is attached to the tobacco column 24 with a tipping material 26 to form the cigarette . The tipping material is illustrated as being formed with through flow ventilating air perforations 30 and 32. . The perforations 30 in the tipping material 26 communicate with the grooves 120 to provide for ventilating air flow into the grooves; and the perforations 32 overlay the air permeable portion 123 of the wrapper 114 to provide'for ventilating air flow into the filter rod 112. Each of the perforations defines ventilating air flow through area preferably equal to, or larger'than that defined by each of the perforations 32.

When a smoker draws on the mouth end 116 of the filter 110 while smoking the cigarette , ventilating air is simultaneously drawn through the perforations 30 into the grooves 20 and through the perforations 32 into the filter rod 112 through the air permeable areas of the wrapper 114 outside the adjacent grooves. The ventilating air entering the grooves 120 travels directly to the open end 122 of the grooves at the mouth end of the filter rod without mixing with smoke flowing through the filter rod because of the impervious walls of the grooves. The ventilating air entering the filter rod through the perforations 32 mixes with and dilutes the smoke flowing through the filter rod from the tobacco column 24 as it travels to the mouth end of the filter rod.

Claims (7)

CLAIMS:

1. A filter for a cigarette comprising: a porous filter rod of generally cylindrical configuration; a wrapper extending longitudinally along said 5 filter rod from one end thereof to the other end and circumscribing said rod leaving flow-through opposed ends of said filter rod; said wrapper being formed with a plurality of grooves spaced from each other circumferentially of, 10 and embedded into, said filter rod, said grooves being open at the ncuth end of said filter rod and extending therefrom in a generally longitudinal direction of said filter rod to a closed end for a distance less than the length of said filter rod; 15 the embedded walls of said grooves defined by said wrapper material being impermeable to air and smoke, and the portion of said wrapper between adjacent grooves being impermeable to air, said wrapper upstream of the closed ends of the grooves being permeable to 20 air; and, tipping material extending longitudinally of and circumscribing said wrapped filter rod, said tipping material being air permeable, permitting ventilating air flow therethrough into said grooves, and also per25 minting air flow therethrough into said filter rod through said permeable portion of said wrapper to comingle with and dilute smoke flowing through said filter rod from one end to the other.

2. The filter of claim 1, wherein said tipping material 30 permits ventilating air flow into said grooves only near the ends thereof opposite the ends thereof which which are open to the end of said filter rod.

3. The filter of claim 1 or 2, wherein said air permeable tipping paper is made permeable by means of perforations formed through said tipping material at selected locations.

4. The filter of claim 3, wherein said perforations permitting ventilating air flow through said tipping material into said grooves are arranged in a spaced apart circular array about the circumference of said filter rod; and said perforations permitting ventilating air flow through said tipping material into said filter rod are arranged in a spaced apart circular array about the circumference of said filter rod.

5. The filter of claim 3 or 4, wherein each of said perforations permitting ventilation air flow into said grooves defines a ventilating air flow through area at least as large as the ventilating air flow through area defined by each of said perforations permitting ventilation air flow into said filter rod.

6. The filter of any one of claims 1 to 5, wherein the embedded walls of said grooves and the portion of said wrapper between adjacent grooves are rendered impermeable by a heat sealing treatment.

7. The filter of any one of claims l to 5, wherein said embedded walls of said grooves and said portion of said wrapper between adjacent grooves are rendered impermeable by treatment with a pore-sealing chemical. S. A filter according to claim 1, for a cigarette, substantially as hereinbefore described with reference to the accompanying drawing.