Tobacco – Smoke separator or treater – Plural diverse elements
Reexamination Certificate
1998-06-10
2001-03-27
Derrington, James (Department: 1731)
Tobacco
Smoke separator or treater
Plural diverse elements
C131S331000, C131S336000, C131S340000, C131S341000, C131S345000
Reexamination Certificate
active
06206007
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cigarette with a dual-structure filter and, more particularly, to a cigarette with a dual-structure filter, having a high draw resistance and exhibiting a decreased CO/tar ratio in main stream smoke.
With recent changes in the taste of smokers, low-nicotine, low-tar cigarettes are being desired. Accordingly, a plurality of air holes (ventilation holes or vents) are formed in a so-called tip paper for connecting a tobacco rod and a filter along the circumferential direction of the filter. When a smoker inhales smoke, air flows into the filter through these holes to increase the air inflow rate (also called the filter ventilation rate) from the tip paper. When the air inflow rate increases, the air amount in main stream smoke increases, and the concentrations of nicotine and tar relatively decrease.
When the air inflow rate is increased, however, the suction resistance (product air-permeation resistance) of a cigarette product lowers. This lowers the draw resistance during smoking, so the original taste of the product cannot be maintained any longer.
Presently commercially available cigarettes with filters generally have a tar amount of 1 to 15 mg/cigarette and a CO/tar ratio (i.e., the weight ratio of carbon monoxide (CO) to tar contained in the main stream smoke) of 1 or more. Cigarettes having a CO/tar ratio of as high as 1.5 are also marketed. Recently, cigarettes having a CO/tar ratio of less than 1 are being desired.
One method of decreasing the CO/tar ratio is to use a filter having a low tar-filtering efficiency and at the same time increase the filter air-permeability. When a filter having a low tar-filtering efficiency is used, the tar amount in the main stream smoke increases to decrease the CO/tar ratio. When the filter air-permeability is increased, the combustion amount of a cigarette reduces to reduce the tar amount, but the CO/tar ratio does not change substantially. Therefore, the combination of the two can decrease the CO/tar ratio while maintaining the tar amount in the main stream smoke at a predetermined value.
Unfortunately, the just-described method also lowers the product air-permeation resistance of a cigarette.
Particularly, cigarettes having filter ventilation (i.e., having means, such as ventilation holes formed in a tip paper, for flowing air from the circumferential surface of a filter) are said to require a product air-permeation resistance of 90 to 130 mmH
2
O in order to maintain a good taste. However, the product air-permeation resistance of cigarettes whose CO/tar ratio is decreased by the above method does not reach 90 mmH
2
O. This deteriorates the taste of the cigarettes.
As another method of decreasing the CO/tar ratio, Jpn. Pat. Appln. KOKAI Publication No. 62-175162 has disclosed a filter using a special material such as a plastic film, e.g., a polyethylene film, as a filter element. Also, Jpn. Pat. Appln. KOKOKU Publication No. 4-16151 has proposed a filter having a special material and a special structure, such as a filter having a plastic tubular inside member whose tip is crimped. These filters can lower the CO/tar ratio. However, the use of the special materials and structures increases the manufacturing cost and makes the filters difficult to manufacture.
BRIEF SUMMARY OF THE INVENTION
It is, therefore, a first object of the present invention to provide a cigarette with a filter, which can present nicotine and tar at reduced concentrations in the main stream smoke and yet exhibit a high draw resistance, without using any special material or structure.
It is a second object of the present invention to provide a cigarette with a filter, having a CO/tar ratio of less than 1 and still having a satisfactory product air-permeation resistance.
According to the present invention, there is provided a cigarette with a dual-structure filter, comprising a dual-structure filter having a first filter element and a second filter element located downstream of the first filter element; a tobacco rod arranged upstream of the filter; and a tip paper covering a downstream end portion of the tobacco rod and a substantially entire circumferential surface of the filter and having an air inflow means including at least one row of a plurality of holes (ventilation holes) formed in a circumferential direction of the filter, wherein an air-permeation resistance per unit length of the second filter element is at least twice an air-permeation resistance per unit length of the first filter element, and an air inflow rate from the tip paper is 20% or more.
In the present invention, the air inflow rate is preferably 35% or more, and more preferably 60 to 85%.
Further, in the present invention, the air-permeation resistance per unit length of the second filter element is preferably 2 to 7 times the air-permeation resistance per unit length of the first filter element.
Furthermore, in the present invention, the air inflow means preferably has an opening position in a region corresponding to the first filter element, and more preferably, in a range of 4 mm from an upstream end to 10 mm from a downstream end of the filter.
In the present invention, a CO/tar ratio of less than 1 and a product air-permeation resistance of 90 to 130 mmH
2
O can be achieved more assuredly when the air-permeation resistance per unit length of the second filter element is 2.5 to 10 times the air-permeation resistance per unit length of the first filter element, the air inflow rate from the tip paper is 20 to 85%, and the air inflow means has an opening position in a range of 4 mm from an upstream end to 10 mm from a downstream end of the filter. In this case, it is more preferable that the air-permeation resistance per unit length of the second filter element be 3 to 7 times the air-permeation resistance per unit length of the first filter element and/or the air inflow rate from the tip paper be 30 to 85%.
In the present invention, the filter may have a length of 15 to 40 mm and a circumference of 20 to 27 mm as in the case of usual cigarettes.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinbefore.
REFERENCES:
patent: 5360023 (1994-11-01), Blakely
patent: 5549125 (1996-08-01), White
patent: 5839449 (1998-11-01), Banerjee et al.
Hasebe Hayato
Kaneki Kazuyo
Tanaka Shinichiro
Yoshida Takaichi
Birch & Stewart Kolasch & Birch, LLP
Derrington James
Japan Tobacco Inc.
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