US3394707A - Cigarette filter and method of manufacture - Google Patents

Description

July 30, 1968 c. A. ELLIS 3,394,707

CIGARETTE FILTER AND METHOD OF MANUFACTURE Filed Oct. 8, 1964 37 7 INVENTOR.

CHARLES A. ELLIS United States Patent 3,394,707 CIGARETTE FILTER AND METHOD OF MANUFACTURE Charles A. Ellis, Point Road, Marion, Mass. 02738 Filed Oct. 8, 1964, Ser. No. 402,422 Claims. (Cl. 131-105) ABSTRACT OF THE DISCLOSURE An improvement in cigarette filter consisting of die formed cup shaped elements, the bottoms multiplyperforated by narrow tapered slots, the sides shaped to provide controlled nesting and peripheral sealing in a rod like assembly of elements adapted to handling for machine assembly in cigarettes.

This invention relates to improvements in filter devices for filter-tip cigarettes in which the filter is an integral portion of the cigarette, and has particular reference to the use of interlocking cup shaped elements for improvement of the filtering action for removal of tars and vapors from the raw cigarette smoke.

One object of this invention is to provide means for elimination of heavy tars and vapors before they reach the surface active filter element in order that the latter may trap the lighter and move volatile combustion products in a more effective manner.

Another object is to provide in a filter system a section of reduced area of such a shape as to promote a high degree of turbulence in the smoke stream passing therethrough whereby changes in vapor velocity will aid in condensation of vaporized materials.

Another object is to provide means for minimizing the pressure drop along a filamentary type of filter in order that channeling effects due to non-uniformity of sectional resistance may be reduced to a minimum and maximum filter surface exposure attained.

Still another object is to provide for the incorporation of such metallic elements in the cigarette in a manner adapted to the automated mass production methods of the cigarette industry.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a sectional view of a filter-tip cigarette taken along its longitudinal axis, embodying one form of the invention;

FIG. 2 is a longitudinal sectional view of a single cup element;

FIG. 3 is an elevation view of the cup element of FIG. 2 as seen looking toward the bottom of the cup from the outside;

FIG. 4 is an enlarged fragmentary view of a portion of the base of a cup illustrating a detail of a number of preferred types of perforation;

FIG. 5 shows a continuous length of interlocking cup elements assembled for ease of handling in automatic cigarette making machines;

FIG. 6 illustrates the manner of separation of the element of FIG. 1 from the continuous stick form of FIG. 5.

FIG. 7 shows a longitudinal section of an assembly of three interlocking cup elements as prepared for unit loading in cigarette making machines.

At the present time much attention is being given to improving the filter efficiency of filter-tip cigarettes, particularly since the public health report associating high rates of lung cancer with heavy cigarette smoking habits. While no claim is made that the subject invention will in any way affect lung cancer rate it can be unequivocal- See ly stated that the combination of the multiple interlocking cup element of this invention with any of the presently used filamentary surface active filters does remarkably improve their filtering capacity.

The improvement in filter action is brought about primarily by a combination of a number of different effects. The interlocking die formed metallic cup elements of themselves serve to trap and contain tars and large amounts of moisture condensed from the combustion products. This effects a two-fold improvement in action of the filamentary filter element; mass fiow through the filter is reduced and removal of water and tar leaves the filter free to trap volatile hydrocarbons. Another effect is limitation of total mass flow through the perforations to a critical amount. This means that excessive drawing of air through the cigarette is prevented and as a result the maximum burning temperature is considerably reduced. High burning temperatures are known to produce more injurious combustion products than those produced at lower temperature. Still another effect is the reduction in pressure drop along the length of the filamentary filter element with the result that nonuniformity of filamentary packing is less critical as to channeling potential and more uniform exposure of the filter surface results.

Referring more particularly to the drawings in which like characters of reference designate like parts throughout the several views; in FIG. 1, 1' generally indicates a filter-tip cigarette embodying this invention. A tobacco column 10 is enclosed in a paper wapper 13. Attached at one end of the wrapper is a tubular mouthpiece 12 of moisture resistant paper or other suitable material. Enclosed within the tubular mouthpiece adjacent the tobacco column is a multiple interlocking cup filter assembly generally indicated at 3' together with a filamentary type of filter element 11 at the outer extremity thereof. The assembly 3 is comprised of a number of interlocking cup elements, the sides of the cups preferably of stepped form with shoulder at 17 and so proportioned that the outer surface of small diameter 15 is a tight fit in the inner surface of large diameter 14 of another cup. With good size control it has been found unnecessary to use cementing material between these surfaces but cementing may be required where such control is inadequate to provide a secure fit. The outer surface of the large diameter portion of the cups is preferably adhered to the tube material as it is rolled so as to provide a positive seal around the periphery of the cups. Each cup bottom 16 is perforated in a completely random pattern by a number of perforations 18. It is important that the total area of such perforations be of the order of from one to three percent of the tobacco column cross section. It is also important that the perforations be very small in one dimension. Expressed in another way it is important that the ratio of hole edge length to hole area be maximized. In a circle this ratio is at a minimum, in an infinitely narrow simple slit it is at a maximum. In our application the slit edge is effective as a weir for the combusted gases and, to the extent of gas exposure, acts as a high conductive cooling means for reducing gas temperature to aid in condensation. However, the requirement for motion to produce valve action, as explained more fully below, provides a practical limit to the ratio beyond which some benefits of the multi-functional aspects of these perforations would be sacrificed. various form of such perforations are clearly illustrated in FIG. 4. The Y-shaped perforation 18 has three such tabs, the cross-shaped perforation 19 has four tabs and the H-shaped perforation 20 has two tabs. These tabs are slightly flexible and project outwardly from the bottom surface of the cups. 'In their assembled position within a cigarette the tabs point up-stream of the air flow during use. If the airstream is normal, that due to the normal average smoker, the resistance to flow is not enough to significantly load these tabs to cause bending. If the air stream is excessive, such as that due to impulsive inhalation, the resistance to fiow being somewhat higher will cause bending of the tabs and actual reduction of air flow. The purpose here is to limit the air stream to give a degree of control to the temperature of combustion of the tobacco. The impulsive inhaler not only takes a great deal of smoke into his lungs normally but much of it is from high temperature combustion products. Another reason for having the perforations in the form shown is that the actual openings have the shape of a tapered slot. This form of perforation produces very pronounced turbulence on the exit side of the sealing wall, much more than from a regular or round hole for example, with significant pressure changes in short time periods which are conducive to good separation of the moisture and heavy hydrocarbons. A further reason for selecting this form of perforation is the very long edge compared with area so that the intimate contact with the combustion products results in a maximum cooling effect upon the gas and vapor passing through, the wide tabs serving as highly conductive pathways for the dissipation of absorbed heat away from the openings.

In order to promote the condensation of the heavy components by the metallic element the greatest pressure drop should be across that element since the pressure changes through the element will determine the turbulence in the smoke stream as it passes through the slots. Physical nonuniformity of packing in the filamentary portion produces hole effects which modify the exposure to surface action inversely with the degree of openness of the holes at constant pressure. However at greater pressure drop from end to end of the filaments the mass flow through the low resistance holes increases faster than the pressure change and the result is less filter exposure. Thus it is highly desirable to proportion the filter resistances with these principles in mind. High resistance metallic and low resistance filamentary portions are optimal within the permissible total resistance.

In the practical application of the interlocked cup elements to the production of filter cigarettes the die formed cups may be assembled in sticks of standard or continuous length as best shown in FIG. 5. The sticks would then be introduced into a cigarette-forming machine with automatic means for feeding and cutting. Cutting could be conveniently at any integral multiple of a half cup length. FIG. 6 shows how a cut at 8-8 and another at 99 separated by three half-lengths produces a filter unit comprising three perforated walls similar to that shown at 3' in assembled position in the cigarette of FIG. I. The small diameter half-portion 22 fits within and reinforces large diameter portion of the cup on the left and the large diameter half-poriton 21 fits over and reinforces the small diameter portion of the right hand cup. The three sections of large diameter, being alike, define an outer cylindrical surface suitable for assembly with and adherence to the moisture-proof outer lip-contacting portion of the cigarette. In this form it is easy to handle and to assemble with the filamentary or fibrous element 11. Another form of filter unit suited to another type of cigarette-making machine is made up of a unit of three interlocking cups as shown in FIGURE 7. These may be formed, punched and stacked in a conventional cut-and-carry type of die forming machine closely adjacent to the cigarette rolling machine and passed to the latter as a unit assembly for incorporation in a cigarette.

Cigarette-making machines are in general costly precision equipment. In order that the benefits of this invention may be made more easily available commercially without extensive capital investment in completely new machines I contemplate the construction of auxiliary filterforming machines as the major cost element. In one arrangement the unit filter comprising a multiple nested cu-p element would be formed and passed to the cigarette-making machine by a synchronized transfer mechanism for incorporation in the cigarette. In a second arrangement the filter cups would be continuously formed and nested by the new machine equipment and fed in continuous form to the cigarette-making machine where filter units would be synchronously separated for incorporation in the cigarettes. A third arrangement contemplates continuous forming and nesting of cups in stick form with an additional operation of cutting to standard stick lengths. The sticks thus formed would then be hopper fed into the cigarette-making machine with unit cutting phased into the cigarette assembly operation.

Cups of the form shown have been easily formed from .001 sheet aluminum foil which is well suited for the purpose because of the high heat conductivity of the aluminum material and also because of its light weight and inlert character. Even in such a thin section the cups are easily and safely handled and when cemented in the tube give the latter substantial reinforcement. However, plastic cups are also satisfactory.

In laboratory work carried on in conjunction with this development it was found that the filter unit 3' would, of itself, and when used alone, separate out quantities of tar and water from the smoke of tobacco. To determine what combustion products were passing through trials were run with standard filter cigarettes, first as purchased, then with others of the same pack cut at the filter-tobacco interface and a metallic interlocking cup unit interposed between the filter and tobacco. In every case the materials caught behind the auxiliary unit were approximately double those trapped in the filter of a standard assembly. Examination of the metallic units showed that they were still trapping both tar and moisture in the same quantities as before. The elimination of the easily-condensed low volatile products from the smoke stream increased markedly the effectiveness of the surface active filter in removal of the more highly volatile hydrocarbon products. About twenty percent of the production cigarettes showed uneven staining of the filters, not always in the same areas, indicating a channeling effect due to non-uniform fiber packing. None of the filters behind the metallic cup elements showed such channeling.

While I have described methods by which the objects and advantages of this invention may be realized I wish to point out that changes may be made in the details of construction and arrangement of parts shown and described without departing from the spirit of the invention. Therefore, it is to be understood that all of the matter set forth and shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a filter-tip cigarette of the character described the combination of auxiliary filter means comprising a plurality of identical interlocking metallic die formed cup elements, forming a substantially unitary structure the bottom wall only of each of said cups perforated in random pattern with a plurality of narrow tapered slots, the said slots having a total area per cup of not less than one percent nor more than three percent of the area of the said bottom wall in order that the resistance of the cup elements shall be high relative to the resistance of the filter as a whole; and the said slots having the ratio of edge length to area of opening maximized to promote condensation by cooling; together with a surface active filter wholly external to said cups abutting one end of said unitary structure; and a tobacco column abutting the other end of the said unitary structure, all within a tubular wrapper.

2. The article of claim 1 in which the edges of the said slots project slightly outward of the plane of the bottom of said cup elements, the opposed edges of said slots adapted to elastic deformation toward said plane and toward one another with the passage of smoke through the slots, the said deformation acting to significantly increase the resistance to the flow of smoke only during impulsive drawing upon the cigarette, and the elasticity of said edges sufiicient to return the edges to define substantially the original area of the slots upon cessation of such impulsive drawing.

3. The article of claim 1 in which the said cup elements are further characterized by: peripheral wall surfaces coacting to form a first seal against the passage of smoke between such surfaces, together with the circumferential grooves between the edges of the said cup elements and the wall of the adjacent cup adapted to receive circumcferential areas of the inside surface of the tubular wrapper to form a second seal between said inside surface and the unitary structure taken as a whole.

4. As an article of manufacture an auxiliary filter means for cigarettes comprising the combination of a plurality of identical interlocking die-formed metallic cup elements to form a substantially unitary structure, the said structure adapted for assembly within a cigarette in abutting relation between a column of tobacco and a surface active fibrous filter, the bottom wall only of each of said cups perforated in random pattern with a plurality of narrow tapered slots, the said slots having a total area of not less than one percent nor more than three percent of the area of said bottom wall, and the said slots having a ratio of edge length to area of opening maximized, these conditions combining to promote deposit of low volatile products of combustion within the auxiliary filter and to prevent wetting and channeling of the fibrous filter so that the said fibrous filter may more effectively trap the more volatile combustion products when the said article is in use therewith.

5. As an article of manufacture an auxiliary filter means for cigarettes comprising: the combination of a plurality of identical interlocking die formed metallic cup elements to form a substantially unitary structure of rod-like form; the separation of a short substantially unitary section of said structure to include a plurality of said cup elements to form a first filter element adapted for assembly within a cigarette in abutting relation between a column of tobacco and a fibrous second filter element; the bottom wall only of each of said cups perforated in random pattern with a plurality of narrow tapered slots, the said slots having a total area of not less than one percent nor more than three percent of the area of said bottom wall, and the said slots having a ratio of edge length to area of opening maximized to promote condensation of the least volatile combustion products within the said first filter element when in use and so assembled.

References Cited UNITED STATES PATENTS 267,070 11/1882 Franke 131-210 3,064,657 11/ 1962 Sh'riner 13110.7 3,172,410 3/1965 Miller 13110.5 3,250,280 5/1966 Yow-Jiun-Hu 131-105 LUCIE H. LAUDENSLAGER, Primary Examiner.

Images