|Publication number||US3046994 A|
|Publication date||Jul 31, 1962|
|Filing date||Jul 2, 1959|
|Priority date||Jul 2, 1959|
|Publication number||US 3046994 A, US 3046994A, US-A-3046994, US3046994 A, US3046994A|
|Inventors||Schur Milton O|
|Original Assignee||Olin Mathieson|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (32), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
July 31, 1962 M. o. SCHUR 3,046,994
VENTILATED CIGARETTE Filed July. 2, 1959 INVENTOR.
MILTON O. SCHUR 3,046,994 VENTILATED CIGARETTE Milton 0. Schur, Asheville, N.C., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Filed July 2, 1959, Ser. No. 824,673 1 Claim. (Cl. 131-10) This invention relates generally to cigarettes and more particularly to an improved cigarette having a mouthpiece or fil-ter tip element. This application is a continuation-inpart of copending application Serial Number 448,815 filed August 10, 1954, issued as US. Patent 2,988,088 on June 13, 1961.
It has been proposed heretofore to provide cigarettes with a stub of aborbent paper, cotton or other filtering medium to remove undesired constituents from the tobacco smoke. Such filters reduce the tar and nicotine content of the smoke a substantial extent by mechanically retaining some of the particulates entrained in the smoke. However, such filters generally remove very little of the gaseous constituents of the smoke including acrolein, hydrocyanic acid, carbon monoxide and other objectionable substances. Furthermore, to display effective filtration, it has been necessary that most prior art filters be assembled so that they offer substantially more resistance to the fiow of air and smoke t-herethrough than would a comparable length of conventional cigarette tobacco compressed to the density of the average cigarette. Such filters notice ably increase the drag. or draw on the cigarette when the smoker pulls a normal volume of air and smoke into his mouth during a puff. Consequently, certain heretofore available filter tip cigarettes have not been entirely satisfactory because many smokers object to a cigarette which has a noticeably increased resistance or drag to the flow of smoke therethrough.
It has been proposed, heretofore, to perforate the wrapper of a conventional cigarette not having a filter ti or mouthpiece element in order to decrease the draft resistance of the cigarette but such cigarettes have the disadvantage of imposing too little resistance to the flow of smoke to be acceptable to the average smoker.
For example, U.S. Patent 439,004 to Harris described a cigarette having minute perforations or punctures in its Wrapper distributed substantially throughout its length. Likewise, French Patent 998,557 described a cigarette having a wrapper of porous paper having its initial permeability to air increased by the formation therein of fine perforations. Similarly, Belgian Patent 568,149 describes the reduction of nicotine content in the smoke and also lower resistance to the passage of smoke by the provision of fine perforations in the wrapper. Belgian Patent 570,440 describes the use of porous cigarette wrapper paper which has been finely perforated by electric discharge treatment. In all such cases, however, the ventilation of the cigarette is accomplished, but only with the simultaneous reduction in resistance to the passage of smoke to an extent not acceptable to most smokers.
It is therefore an object of this invention to improve the smoking characteristics of cigarettes having a filter tip. Another object of this invention is to provide a means for reducing the quantity of harmful gaseous components, including acrolein, of the cigarette smoke as well as reducing the particulate constituents thereof before the smoke is delivered to the mouth of the smoker as the cigarette is consumed without impairing the smoking characteristics of the cigarette. Still another object of this invention is to provide a cigarette having a mouthpiece element and a ventilated wrapper which imposes a resistance to gas flow substantially equal to that of a conventional cigarette while furnishing smoke of reduced particulate content. A further object is to provide a filtertipped cigarette having improved taste characteristics. A
more specific object of this invention is to provide a cigarette having a mouthpiece element and a ventilated wrapper which has smoking characteristics comparable to the conventional cigarette and which is capable of delivering smoke which contains less than the normal concentration of gaseous as well as particulate components of cigarette smoke.
The foregoing objects, as well as others, will become apparent from the following description in conjunction with the accompanying drawing, in which- FIGURE 1 is a perspective view partially in section of one embodiment of this invention;
FIGURE 2 is a perspective view partially in section of another embodiment of this invention; and
FIGURE 3 illustrates in a perspective view, partly magnified, a third embodiment of this invention.
Generally speaking, the objects of this invention are attained by combining in a cigarette a filter tip or other mouthpiece element and a means for admitting sulficient air into the cigarette along the tobacco column thereof to dilute the smoke by at least about 20 percent. In accordance with a preferred form of the invention, a series of orifices of predetermined number and size are provided in the wall of the cigarette located in the cigarette wrapper which encloses the tobacco column, together with a filter tip or other mouthpiece element which restores the desired resistance to gas flow. In another form of the invention a cigarette wrapper having a zone of a substantially greater porosity in the region of the filter tip than in the remainder thereof is utilized. For example, the wrapper may be of a composite structure, the portion in the region of the filter tip having a substantially open structure similar to conventional stencil tissue while the remainder of the wrapper is conventional cigarette wrapping paper.
This invention is predicated upon the discovery that the smoke passing into a smokers mouth from a filter tipped cigarette can be attenuated, without detrimentally affecting the taste of the tobacco smoke, so as to compensate for the difference between the resistance of the filter tip to the passage of smoke therethrough and the resistance imposed by a tobacco column of similar length. Indeed, in most instances the taste of the smoke of the filter tipped cigarette is improved. In contradistinction, the reaction of the smoker of an ordinary untipped cigarette is unfavorably affected if the Wrapper is perforated. The size and number of the orifices in the filter tipped cigarette Wall or the porosity of the zone adjacent the filter tip which gives optimum results will vary with the type of filter utilized, but for the best results, insofar as taste and improvement in smoking characteristics such as improvement in draw of the cigarette, is concerned, the porosity can be such as to result in the dilution of the smoke by air to an extent of at least about 20 percent by volume. The invention thus provides a means for greatly reducing the concentration of the various components of the tobacco smoke by combining a means for attenuating or diluting the smoke with air and additionally filtering the smoke to absorb and adsorb constituents therefrom.
The filter tip or stub can be composed of any ab sorbent material with or without adsorbents included therein but it is preferred that one of the more effective absorbent paper filter tips be utilized. Any material capable of adsorbing components from the tobacco smoke or reacting therewith such as, for example, activated charcoal, cuprous chloride, aluminum hydroxide or the like may be utilized. It is preferred, however, to use a combination of the porous zone in the cigarette wrapper provided by this invention and a filter tip of absorbent paper, with or without an adsorbent material such as activated carbon, or a composite filter tip of two or more elements differing in filtration and adsorbing properties. These filters are particularly advantageous for removing both particulate and some gaseous components from 'the tobacco smoke, but it has been found that by combining these filters with a means for attenuating the smoke the quantity ofacrolein and other adsorbable gas components in tobacco smoke can be even further reduced and that this additional reduction is achieved without seriously altering the drag imposed by the cigarette to the flow of smoke and without seriously impairing the taste of the smoke or otherwise deleteriously affecting the smoking characteristics of the cigarette. Indeed, as pointed out elsewhere herein, the taste is improved. Maximum quantities of acrolein are removed if the filter combined with the porous zone in the cigarette wrapper contains particles of activated charcoal. In order that the objectives of this invention are achieved, it is essential that the cigarette have a filter tip or similar restriction at the mouth end thereof which imposes a greater resistance to the flow of smoke therethrough than would a similarly dimensioned column of tobacco of the density ordinarily utilized in cigarettes. For example, the mouthpiece element may consist of tobacco compressed to a density higher than normal.
In the drawing, FIGURE 1 illustrates one embodiment of this invention in which cigarette 1 is composed of wrapper 2 of conventional cigarette paper enclosing tobacco 6 and filter tip 3. Wrapper 2 is also provided along its length with a series of orifices 4, for example, twelve perforations about 0.25 mm. in diameter having a total area such that sufiicient air enters therethroug-h to compensate for the difference between the resistance to the flow of smoke imposed by the filter 3 and the resistance of a comparable length of tobacco 6. Preferably, filter 3 is an effective paper filter which imposes a resistance to the fiow of smoke equivalent to a column of water about 32. millimeters high when the flow through the tip is 17.5 cc. per second. The series of orifices 4 admit sufiicient air into the cigarette to compensate for the difference between this resistance of the filter tip and the resistance imposed by a similar length, for example, 13 millimeters of conventional cigarette tobacco compressed to the density of the average cigarette.
In FIGURE 2, a cigarette 1 contains a column of tobacco 6 and a mouthpiece element 7 of tobacco compressed to a density greater than normal, for example, to about twice the usual density, enclosed in wrapper 2, constituting a firm mouthpiece. In this embodiment, the
.wrapper is of cigarette paper made sufiiciently permeable to air by modifications of the paper manufacturing proc- I as to compensate for the increased resistance of the mouthpiece element.
In the embodiment illustrated in FlGURE 3, cigarette 1, provided with filter 3 and mouthpiece wrapper 5, has been provided with a series of orifices 4 extending through wrapper 2 along about half its length adjacent the filter. In this embodiment the wrapper may be of porous cigarette paper, provided with minute perforations in a zone of increased permeability near the mouthpiece. The lateral entry of air compensates for the resistance imposed by the mouthpiece to the flow of smoke to such an extent that the cigarette can be smoked as easily as the conventional cigarette not having a filter tip.
It is fundamental to this invention that through a choice of predetermined number and size of passageways for the entry of air through the wrapper, the drag required to pull a given volume of air and smoke through the filter tip can be adjusted to be equivalent to the drag required to pull an equal volume of smoke through a conventional cigarette not having a filter tip. This is accomplished by providing the orifices 4 which introduce a second path, in parallel with the path through the rod of tobacco 6, for air to enter the cigarette laterally. Through control of the size and number of orifices or passageways, the resistance to flow in the cigarette 1 is decreased to the extent that the mouthpiece would increase the overall resistance of the cigarette with a conventional non-porous wrapper.
Ordinarily, in practicing this invention, it is preferred that the resistance of the filter tipped cigarette be adjusted within a range such that it does not deviate by more than about 30 percent from the resistance of the conventional cigarette. By way of example of the accomplishments of this invention, if the permeability provided in the wrapper of any one of the embodiments thereof is preselected so that the resistance of the orifices is equal to the average resistance of a rod of tobacco 6 during the smoking of the cigarette, the volume of smoke drawn through the rod of tobacco 6 from the burning zone of the cigarette during a normal puff will average approximately one-half that of the smoke pulled through the conventional cigarette. This alone lowers the concentration and the amount of smoke passing through the cigarette by about one-half that which would pass through an ordinary cigarette. But if the filter retains any of the constituents in the smoke, the amount of the undesired ingredients passing through the filter will be further decreased. For example, if we assume that 30 percent of the particulates in the smoke are retained by the filter, the total reduction in the concentration and amount of particulates passing through the filter would be about 65%.
In the above example, if the average drag on the cigarette is to be normal, the conductance of the filter tip 3 would have to be equal to that of the sum of the average conductance of the tobacco rod 6 and the conductance of the orifices 4. Filter tips in common use with a conductance of this order will retain only about 30% of the particulates in the smoke. Such tips during a normal puff increase the drag on a conventional cigarette during a normal puff by more than about Further, they remove or retail no significant quantities of the constituents of the gas phase of the smoke. In contrast, the cigarette of the present invention, carrying a similar filter tip, but provided with the permeability of the example given above, delivers to the smoker during each normal puff only about as much of the gaseous constituents of the smoke as he would receive from a conventional cigarette without a filter tip. The resistance of the lighted cigarette having the combination of a filter tip and permeable wrapper is equivalent to a column of water about mm. high which is substantially the same resistance as that of the average lighted ordinary commercially available cigarette not having a filter tip.
It is apparent from the foregoing that the cigarette provided by this invention provides a means for attenuating the particulate as well as the gaseous constituents of tobacco smoke and'that moreover this objective is accomplished without materially increasing or decreasing the resistance of the cigarette to the flow of gases therethrough. That is, a cigarette having improved smoking characteristics, insofar as taste and reduction of harmful constituents in the smoke is concerned, is provided without at the same time introducing an undesirable characteristic. Although the resistance of the filter tip at the mouth end of the cigarette will vary over a wide range, depending upon the construction of the filter tip used, it is seldom necessary to use a filter which imposes a resistance to the flow of gases therethrough greater than about 5 times the resistance of a column of cigarette tobacco of equal length and compressed to the same extent as tobacco is compressed in a cigarette. It is preferred that the resistance of the filter tip or restriction be about 25 percent to about percent that of the resistance of the original, untipped, unpcrfora'ted cigarette when first lighted. For best results, it is preferred that the resistance of the filter tipped cigarette to the flow of smoke therethrough not deviate more than about 30 percent from the resistance of typical untipped cigarette.
The resistance imposed by a filter of a given construction has been found to vary only a slight extent from one filter stub to another. It is, therefore, possible to determine by experiment the average resistance imposed by a filter of a particular construction and then to perforate the wrapper while the cigarette is in the testing apparatus until the resistance to the fiow of smoke is reduced to the desired resistance. After the proper size and number of orifices has thus been determined, similar perforations can then be placed in cigarettes as they are manufactured to provide cigarettes embodying this invention. As indicated hereinbefore the desired resistance is substantially equal to that of a commercially available cigarette not having a filter tip or, in other words, in typical cigarettes equivalent to a column of water about 70 mm. high when gas is flowing through the lighted cigarette at the rate of 17 /2 cc. per second.
If it is desired that less of the particulates be filtered out for a given attenuation of the constituents of the gas phase, a less effective filter tip is used on the cigarette of the present invention. By way of example, this can be accomplished without lowering the resistance to flow through the tip if the filter is comprised of crumpled tissue paper prepared from highly beaten pulp. As the retentivity of the stub for particulates approaches zero, and the stub thereby becomes no more than a restriction, the extent of the reduction in concentration of the particulates in the smoke approaches that of the gas phase until, in the limit, they become equal.
It will thus be clear from the above description that the improved cigarette of this invention requires the conjoint use of two features. First, a mouthpiece element is required which imparts a greater resistance to the passage of smoke than a column of cigarette tobacco of normal density, which column is equidimensional with the mouthpiece element. Secondly, the cigarette wrapper must be sufficiently permeable to air so that the overall resistance to gas How will approximate that of a conventional untipped cigarette having a non-porous wrapper. The result is an improved cigarette having normal puffing characteristics but delivering smoke of substantially reduced content of particulate matter and of undesired gaseous irritants.
The mouthpiece element is preferably an effective filter I tip which is capable of further reducing the content in the smoke of particulate and gaseous components. However, the described advantageous attenuation of the smoke by air is accomplished also with the use of a relatively ineffective filter and even with the use of compressed tobacco as the mouthpiece element.
The preferred wrapper element of this invention is a somewhat porous cigarette paper having its permeability to air increased by a mechanical operation. The latter may for example consist of perforating so as to produce the desired number of tiny openings, ranging from 0.01 to 0.25 millimeter in diameter, which are practically invisible at usual reading distance, if not magnified. Porosity through spaced invisible openings may likewise be produced by grooving or embossing the paper against a yielding surface, whereby the permeability of the paper is increased by the formation of invisible pores by loosening or displacing fibers in the paper.
The paper conventionally used for cigarette wrappers is relatively non-porous, being characterized by a porosity index of about 35 to 50 (number of seconds required for the passage of 50 cubic centimeters of air through a circular sample of the paper one inch in diameter at a pressure drop of approximately 4 /2 inches of water). Such paper is of desirable uniform appearance, strength and burning rate, and may readily be rendered permeable to the desired extent by a mechanical operation as referred to above.
Preferably, the wrapper consists of permeable paper made porous by modifications of the paper manufacturing process, principally by a reduced extent of beating and thus of the extent of fibrillation of the cellulosic fibers and by increasing the content of filler, such as calcium carbonate, in the furnish. In this way, satisfactory paper of adequate strength and appearance can readily be made having a porosity index of 20 to 30. Further decrease of the index to the desired value of 10 to 15 (thereby increasing the permeability to air) can then be readily accomplished by a mechanical operation, as by perforating.
Likewise, the paper may be manufactured so as to have a porosity index of about 10 to 15, but is then characterized by decreased strength properties and non-uniform appearance, generally described as of Wild formation. However, such paper may be used to advantage in accordance with this invention when the strength and appearance characteristics mentioned above are of no great significance. Another factor which must be considered in the use of paper so manufactured as to be highly permeable without subsequent mechanicaltreatment is the need for incorporating additives to lower the combustion rate to the desired value.
Extensive tests have shown that the desired attenuation of the smoke by at least 20% of its volume of air, while retaining the overall resistance to the flow of smoke characteristic of a normal untipped cigarette having a non-porous wrapper, is accomplished in a cigarette having a flow-resistive mouthpiece element such as the usual tightly packed filter tip, by providing a paper wrapper having a porosity index less than 15. As stated above, such wrapper may consist of paper having the desired permeability by virtue of modifications in the paper manufacturing process resulting in numerous fine pores and openings distributed throughout the paper. For example, in the embodiment shown in FIG. 2, the wrapper 2 consists of paper having a porosity index of 10 to 15.
In the embodiment shown in FIG. I, the desired permeability is obtained by perforations 4 in ordinary cigarette paper having a porosity index of 35 or greater. Likewise, other mechanical treatments may be applied to the paper to result in the spaced openings required.
Extensive tests have also been carried out to compare the relative effectiveness of various methods of attaining a permeability value within the desired range, as well as of variations in the distribution of the pores or openings. The results of such tests have shown that the desired results are obtained by providing the required permeability or porosity index regardless of method and independently of the distribution of the openings.
Thus, in a number of series of comparative experi ments, essentially the same reduction in particulate content and in contents of gaseous components such as acrolein and carbon monoxide were found in cigarettes provided with a given type of filter-tip and a wrapper characterized by the desired permeability value. This was verified for the following modifications:
(l) Wrapper of paper made to have a porosity index of about 10.
(2) Wrapper of paper made to have a porosity index of about 20, the wrapper being then provided with a sufiicient number of perforations to display the same value of resistance to gas flow per cigarette as in (1).
(3) Wrapper of paper made to have a porosity index of about 40, the wrapper being then provided with perforations uniformly along its length so as to display the same value of resistance to gas fiow per cigarette as in (1).
(4) As in (3), but with perforations in the wrapper limited to the area adjacent the filter tip.
(5) As in (3), but with perforations along opposite sides of the Wrapper, i.e. along the top and the bottom.
The embodiment shown in FIG. 3 illustrates the most highly preferred combination, wherein the required additional openings are provided mechanically, as by perforating, in the portion of the cigarette wrapper adjacent or near the mouthpiece element. As indicated in the drawing, such additional openings are not visible to the naked eye, being less than 0.25 millimeter in diameter,
though readily visible when magnified to times the natural size. The number of such openings provided in the wrapper is such as to compensate for the added resistence to gas flow imposed by the filter tip 3 or other mouthpiece element beyond that of an equal length of tobacco column 6, being sufficient to attenuate the smoke by at least 20% of its volume of air and up to about an equal volume of air.
The provision of openings near the mouthpiece insures a desirable extent of attenuation of the smoke by air throughout the smoking of the cigarette and thus provides optimum conditions for obtaining the desired results, including maximum cooling effect on the smoke. Also, the use of a wrapper made of paper having a porosity index of about 20 or greater is preferred because of excellent strength, appearance, and desired combustion characteristics.
Typical test data which illustrate the difference between the conventional cigarette and those of the present invention are as follows:
Experiment 1 Conventional untipped cigarettes 70 millimeters long by 26 mm. in circumference, weighing on the average 1.00 gram each, and having after being lighted a drag equivalent to a column of water 70 mm. high when the flow of air and smoke through the cigarette is 17.5 cubic centimeters per second, were smoked in a smoking machine which takes a 2 second puff once a minute, each pulf pulling 35 cc. of air and smoke through the cigarette into a smoke collector. After a 47 mm. length of cigarette has been consumed, the cigarettes were discarded. On the average, 9.5 puffs per cigarette were required. The smoke thus collected was carefully dissolved in a solvent consisting of 3 parts of ethyl alcohol and 2 parts of toluol by volume, the solution transferred to a weighing bottle, the solvent evaporated at room temperature, the residue heated overnight at 95 C., and weighed. The residue amounted to 25.6 milligrams per cigarette.
Other cigarettes from the same carton were similarly smoked and the gas phase of the smoke analyzed for acrolein. It was found that on the average a total of 0.025 mgm. of acrolein per cigarette passed into the collector.
ExperimentZ To similar cigarettes were afi'ixed filters comprised of crumpled tissue paper prepared from cellulose fibers the average, 10.1 puffs were now required to consume the same length of tobacco rod as in the previous experiment. Each of the cigarettes was found to deposit on the average 10.8 mgms. of smoke in the smoke collector; the weight of acrolein found passing into the collector averaged 0.018 mgm. per cigarette.
It is thus seen that the orifices pricked through the cigarette wrapper not only reduced the drag of the filtertipped cigarettes from an initial value of 86 mm. down to 70 mm, i.e., to that of the untipped cigarette of Experiment 1, but lowered the particulates passing into the collector 58%, as compared with the untipped cigarette, and the amount of acrolein by 28%.
Experiment 4 In another experiment, the filter was comprised of tissue prepared from highly beaten cellulose fibers. Its resistance to the flow of air and smoke was the same as in Experiment 2. In the present experiment, the filter tip removed only 15% of the particulates from the smoke, and since there were no bypass holes pricked through the wrapper, the quantity of acrolein in the smoke was the same as in the case of an untipped cigarette.
Experiment 5 When, however, cigarettes such as those used in Experiment 4 were provided with the tiny orifices so as to bring the drag back to that that of an untipped cigaronly slightly beaten prior to the formation of the sheet.
The filter was 13 mm. long. To keep the overall length of the filter'tipped cigarette the same as that of the original cigarette, a- 13 mm. length of the tobacco rod was cut off the free end of the cigarette before the filtertipped cigarette was smoked in the smoking machine. Laboratory measurements showed that in order to suck 17.5 cc. of air and smoke per second through the lighted filter-tipped cigarette with an overall length of 70 mm, a drag or suction equivalent to a column of 'water 86 mm. high now had to be applied. As in the case of the untipped cigarettes of Experiment 1, an average of 9.5 pufis were required per cigarette to reduce the length of the cigarette by 47 mm.
The weight of smoke collected average 16.3 mgms. per cigarette. The weight of acrolein found in the smoke passing into the smoke collector average 0.025 mgm.
Thus, the filter tip removed 36% of the particulates and none of the gaseous acrolein.
Experiment 3 Another set of these filter-tipped cigarettes was then prepared, but in this case, 10 tiny holes were pricked through the cigarette Wrapper near the juncture of the filter and the tobacco rod. The size of the holes were such that the drag necessary to pull 17.5 cc. per second of air and smoke through the tip at the start of smoking was equivalent to a column of water 70 mm. high. On
et-te, the weight of particulates passing into the smoke collector was 42% less than in the case of the untipped cigarette, and the weight of acrolein was reduced by 32%.
Experiment 6 In experiment 6, a filter tip of the same resistance as in Experiment 2 was used. It was comprised of paper made from pulp beaten to an intermediate extent and containing 4.7% of activated charcoal. The weight of particulates entering the smoke collector was found to be 21% less than that of the untipped cigarette of Experiment 1; but because of the presence of activated charcoal in the filter tip, the quantity of acrolein in the smoke was less by 26%.
Experiment 7' When the filter tip such as that used in Experiment 6 was provided with tiny orifices in the cigarette wrapper to bring the drag back to that of an untipped cigarette, the weight of particulates passing into the smoke collector. was found to be reduced by 54% as compared with the untipped cigarette, and the weight of acrolein by 48% It is apparent from the foregoing that the extents to .which the particulate phase and the gaseous phase of the smoke can be reduced in concentration and in total amount entering the smokers mouth is controllably variable over a wide range through the selection of various appropriate combinations of mouthpiece resis ces, fi ter capacities, and by-pass orifice resistances.
Although various embodiments have been described in detail in the foregoing for the purpose of illustration many modifications will occur to those skilled in the art and can be made without departing from the scope of the invention as defined by .the appended claim.
What is claimed is:
A cigarette adapted to deliver air-attenuated smoke containing at least one-fifth of its volume of air, comprising a column of tobacco, a wrapper therefor, and a mouthpiece element at one end of said column, said element having a resistance to gas flow substantially greater than that of an equal length of said column, and said wrapper having an initial porosity index of about 20 to 30 and being provided with a plurality of spaced perforations having a diameter of 0.01 to 0.25 millimeter, the
size and number of said spaced openings being such as to impart to said wrapper a porosity index of about 10 to 15 and to the aid cigarette an initial resistance to 10 gas flow substantially equal to that of a normal un- 2,304,009 Muth Dec. 1, 1942 tipped cigarette of equal length having a substantially 2,693,193 Pelletier Nov. 2, 1954 non-porous wrapper. 2,815,761 Shearer Dec. 10, 1957 2,841,153 Pelletier July 1, 1958 References Cited in the file of this patent 5 ,9 3,647 Aghnides Feb. 2, 1960 UNITED STATES PATENTS FOREIGN PATENTS 1,920,708 Moljns Aug. 1, 1933 516,067 Great Britain July 26, 1939
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|U.S. Classification||131/336, 131/342|
|International Classification||A24D1/00, A24D1/02|