US3297506A - Process and apparatus for blooming tow - Google Patents

Description

1967 J. K. PANNILL, JR., ETAL 3,297,505

PROCESS AND APPARATUS FOR BLOOMING TOW 3 Sheets-Sheet 1 Filed Oct. 8, 1962 Qwum 36.

Qwml 30h JamesKPann ilLk mmflm Fm M9 W W R FUDOORQ DZFPmDFw Jan. 10, 1967 J. K. PANNlLL, JR, ETAL 3,297,506

PROCESS AND APPARATUS FOR BLOOMINCI TOW 3 Sheets-Sheet 5 Filed Oct. 8, 1962 JflnzesKPannill/r Robert Q .Yaniz United States Patent 3,297,506 PROCESS AND APPARATUS FOR BLOOMING TOW James K. Pannill, Jr., and Robert C. Yantz, Kingsport,

TGHIL, assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey Filed Oct. 8, 1962, Ser. No. 229,022 6 Claims. (Cl. 156-152) This invention relates to improvements in the method and apparatus for processing tow into tobacco smoke filter elements using an air jet. More particularly, this invention concerns improvement in the process and apparatus wherein tow may be manufactured into tobacco smoke filter elements of an improved quality, but more economically than heretofore possible.

The manufacture of tobacco smoke filter elements from special tows composed of filaments generally in accordance with the disclosure of Crawford and Stevens US. Patent No. 2,794,480 is already quite extensively carried out in the industry. In such processes the tow is usually opened up or banded by a plurality of steps involving primarily mechanical treatment. The tow thus bloomed is passed through a separate device called a spray booth or a plasticizer booth in order to apply certain addenda to the bloomed tow. Thereafter the tow thus treated is conducted to steps for compacting the tow into the desired filter shape and the like.

In a more recent disclosure of Dyer et al. Serial No. 736,900, now US. Patent No. 3,079,663, there has been described a slot jet construction and associated parts whereby existing installations in accordance with the aforesaid Crawford and Stevens inventions may be conveniently modified .and improved. That is, the said Dyer et al. invention of application Serial No. 736,900 is particularly useful in connection with already existing tobacco smoke filter element installations for suitably modifying such installations to more efiiciently and better handle tow. Also, such type modification with a slot jet permits the better processing of tow of a wider denier range.

With the increase in installations for filter manufacture and the desirability of the greater facility for processing certain of the tows now available, demands have arisen for further simplified and improved processes and apparatus. Caines et al. Serial No. 27,091, now US. Patent No. 3,099,594 discloses the development of a new and simplified process and apparatus for making filter elements of the class indicated and of a quality at least equivalent to or, in certain instances, better than those produced earlier. Pannill (one of the inventors herein) is also a co-inventor in the forementioned Caines et al. application.

The method and apparatus for blooming filter tow using the circular venturi jet device of Caines et al. Serial No. 27,091 uses compressed air to debundlize and separate the many individual crimped filaments in a tow from each other. Tow so processed is then ready for manufacture into cigarette rods and thence into filter tips. The work which we have now done shows that equally as good blooming of tow can be obtained by eliminating the tapered venturi section beyond the straight throat of the Caines et al. jet. Our cutoff (or short jet, as we prefer to call it) can function in exactly the same manner as the Caines et al. jet except that our jet uses less air and at lower pressures.

Thus, after extended investigation we have found that the basic jet of the above Caines et al. application may be modified to permit processing a tow into filter elements at reduced jet air pressures and air consumption, with less filament damage and, simultaneously, with an increase in the available filter rod pressure drop range.

This invention has for one object to provide improvements in the method and apparatus for proceming tobacco Patented Jan. 10, 1967 smoke filter tow. Another object is to provide improve ments in said method and apparatus whereby filter elements of a quality equal to or better than that of presently produced filter elements are obtained. Still another object is to provide simplified process and apparatus combinations for converting filter tow into filter elements which is adaptable to the processing of a wide range of tow deniers. A still further object is to provide a jet construction specially suitable for processing tow which is being converted into filter elements, but at air pressures and air consumptions greatly reduced from those presently found necessary. Another object is to provide a method and jet apparatus to process filter tow whereby filament damage is reduced and, additionally, the available pressure drop range of the final end products (cigarette rods and filter tips) is increased. Other objects will appear hereinafter.

A plasticizing material may be applied to tow substantially at the start of the processing of the tow as, for example, just after the tow is removed from the tow package. The tow is then processed in the circular jet of the present invention whereby the plasticizer is thoroughly and uniformly distributed-over and on the tow and the tow suitably bloomed. The tow thus processed is conducted to the filter forming, wrapping and the like steps and excellent filter elements obtained. The above Caines et al. application of our associates discloses several ways in which a plasticizing material may be introduced into their circular jets, which methods and apparatus may be used with the short jet of our invention as well.

Our invention will be made clear from the following specification and the accompanying drawings in which like numerals refer to like parts, and in which:

FIG. 1 is a flow diagram of a process such as may be carried out in accordance with the present invention.

FIG. 2 is a semidiagrammatic side elevation view of an apparatus combination such as may be used for carrying out the process of the present invention.

FIG. 3 is a cross-sectional view of our circular short jet such as may be used in carrying out the process of the present invention.

FIG. 4 is a cross-sectional view of a jet somewhat similar to that of FIG. 3.

FIG. 5 is a cross-sectional view of the thin orifice plate 13 of FIG. 3.

FIG. 6 is a cross-sectional view of the combined orifice and spacer as shown in FIG. 4. This is an alternate construction for parts 13 and 14 of FIG. 3.

Referring now to FIGS. 1 and 2, the tow blooming process is illustrated as follows: Briefly, a continuous multifilament crimped tow 1 is withdrawn from supply package 2 over guide 3 by feed roll pair 4. It passes, under tension generated by the suction of blooming jet 6, over suitable plasticizer applicator(s) 5 into said blooming jet 6. Here it is subjected to an explosive expansion of compressed air in our specially adapted nozzle or jet which is described in more detail hereinafter. While in the jet, the tow as it is bloomed is subjected by means hereinafter described to a spray or fog of an atomized liquid which is a plasticizer for the tow being processed. The plasticized tow is expelled from the jet under the influence of the expanding air flow and passes to feed rolls 7. Feed roll pair 7 is operated at a somewhat slower speed than roll pair 4 so that the tow is in a state of relaxation or under the very minimum of tension between jet 6 and roll pair 7. The tow then advances to a stuffing jet 8 as described in Wexler US. Patent No. 3,016,945, or as in Crawford and Stevens US. Patent No. 2,794,480 and then to a cigaretting machine 9.

Referring to FIG. 3 the circular short jet will now be described. It will be noted that our jet is of the same general configuration as the jet described in Caines et al. application Serial No. 27,091, now U.S. Patent No. 3,099,594, and consists of an annular space for the air to be uniformly directed at the tow which enters through the center of the nozzle. The air strikes the bundle of tow concentrically, mixes with the tow beyond the orifice and conveys the tow through the throat of the jet to exit into a restrictive device or bustle, as it has been called. The flat spring fingers of this device serve to retard and confine the tow upon its exit, thereby enhancing blooming. The tow and the slightly expanded compressed air are mixed together intimately in the orifice and throat of the jet; however, the pressure is suddenly released as the tow and air emerge from the throat and expand to the extremities of the bustle. Rapid expansion into the bustle is desirable, and since the bustle is almost completely open to the atmosphere, the air which is at a pressure of about p.s.i. suddenly releases to atmospheric pressure. This sudden release enhances the blooming of the tow, and the separation of the bundles of filaments in the tow results in the formation of a homogeneous mass of filaments which can be processed into cigarette rods. The Caines et al. jet does the expanding more slowly in its tapered venturi section, after which the mixture of air and tow expand into the bustle. Since the tow and air do expand slowly through the tapered venturi section where air pressure drops with the slow expansion of the gas, the initial air pressure therefore has to be considerably higher when using a venturi type jet in order to obtain and complete the rapid expansion in the bustle. Accordingly our jet requires less air since, in our jet, the tow and air expand rapidly from a small diameter to the larger diameter, and the air expands to make use of the maximum difference in pressure to the atmosphere.

Referring further to FIG. 3, the jet is composed of a body 10 containing inner members 13 and 14 held in place by the threaded inlet member 11. A passageway 16 extends through the jet device so that a continuous multifilament crimped tow may be passed from the entrance 17 in member 11 to an exit 18 in member 10. The passageway in member 11 is substantially of uniform diameter. The outer surface 19 of the lower member 11 is conical in shape with an included angle of about 40 to 80 degrees, for providing, in conjunction with the tapered surface 20 of the thin orifice plate 13, an annular orifice or passageway for metering the air fiow into the converging tube entrance section 21 of about to degrees included angle. A straight cylindrical tube passage 22 extends to the exit 18 and is of a length from tbout /3 to 8 times the inside diameter of the passage 22.

The exact construction of this portion of the jet is of considerable importance to assure a maximum opening or blooming effect on the tow. If the length of the uniform tube passage 22 is too short, less than optimum blooming will result. Best results are obtained when the length of passageway 22 is about six times its inside diameter.

In addition, for proper functioning of the jet, the inside diameter of passageway 22 should be about 0.75 for a tow of about 37,000 denier size, and should be about 163% of the diameter of the orifice plate orifice 20 and 400% of the inside diameter of the passageway 16 in inlet tube 11. The taper 19 of tube 11 should be about 60 degrees and about 30 degrees less than the angle of the taper of the orifice 20 in plate 13 which should be about 90 degrees. Proper sizing of these items insures that the jet will produce a suction at entrance 17 to facilitate threading the tow into the jet device. They also insure metering and impingement of the air onto the tow as it enters the orifice plate. It is also essential that the passageways in the jet be in accurate concentric and axial alignment to insure uniform impingement of the air on the tow around the periphery of the tow and to insure a minimum of turbulence and swirling or twisting of the air flow. If the air flow swirls, it will tend to twist the tow, thus compacting it rather than blooming it and separating the filaments from each other.

Air is provided to the jet body 10 through one or more openings 23 to an annular chamber 24 formed by the outer surface of inlet member 11 and the inner surface of body 10 and sealed at one end by thread 12. The air in annular chamber 24 passes through multiple cylindrical passages 25, in the flanged portion 15 of member 11 into annular space 26. The air exits from annular space 26 through an annular converging orifice formed by the outer tapered portion 19 of member 11 and the taper bore 20 of orifice plate 13.

While the design and assembly of the jet have been described in a specific manner it will be recognized that variations in the size of the jet, the manner of assembling the component parts of the jet and variations in the shape of noncritical surfaces can be made without departing from the spirit of the invention.

The critical relationship for a typical preferred jet for processing 46,000 total denier, 3.3 denier per filament tow are given in the following Table A:

It has been further found that the blooming of the tow can be materially enhanced if the flow of the tow as it exited from the jet tube at exit 18 is retarded and partially confined. To achieve this end, a plurality of fiat spring fingers 29 may be positioned equidistant around the outer surface of the tube member 10 and extend beyond the end of the member 10 a distance of 3 to 8". The fingers are curled slightly outward to avoid snagging the tow, are slidable axially on the member 10; they may be held in place by a clamp ring, collar construction, or the like such as 27 and 28 of FIG 3. The force to spring the fingers outward is adjustable by moving the clamp closer to or farther away from the end 18 of the member 10.

The effect of these fingers is to retard the exit of the tow from the jet and cause a temporary pile-up of a mass of disoriented filaments through which the exhaust air from the jet must pass. This serves two functions. First, the kinetic energy of the exhaust air causes some further debundlizing of the tow filaments, promoting better blooming of the tow. Secondly, the exhaust air is highly filtered by the tow bundle at this point so that any plasticizer not previously deposited and distributed on the tow filaments is now deposited and distributed. Thus the need for a hood and exhaust system to remove any plasticizer from the exhaust air is eliminated.

Referring now to FIG. 4, there is shown a modification of the basic jet of FIG. 3 where the orifice plate and spacer are combined.

As already mentioned above, FIG. 5 is a cross-sectional view of the orifice plate 13 of FIG. 3, and FIG. 6 is a cross-sectional plan of the combined orifice plate and spacer. Here the spacer 14 and orifice plate 13 are so combined into one piece to form a tapered orifice, and the tapered portion of the orifice extends back to where it meets flange 15 of member 11.

When the tow is subjected to the high velocity explosive blast of air in the jet orifice plate 13 (FIG. 3) and tube 10, the excess plasticizer on these filaments is blown off and impinges on the filaments that did not pick up plasticizer in passing over the applicator slots. Thus an aerosol of plasticizer is generated within the jet and an essentially completely uniform plasticizer distribution is achieved on all filaments in the tow by the time it emerges from the jet. The large mass of bloomed filaments retarded by the aforementioned spring fingers at the exit of the tube insures that only an insignificant amount or no plasticizer will escape to the atmosphere. This is the result of the fact that, while the mass of emerging filaments not only acts as a highly efiicient filter medium for the plasticizer, the exhaust air from the jet is so retarded and slowed down as it emerges from the mass of bloomed filaments that it no longer has sufiicient velocity energy to blow off and remove plasticizer from the surface of the bloomed filaments.

An understanding of the functioning of the apparatus parts disclosed in the several figures is already apparent to a substantial extent from the preceding description. However, a further understanding of the functioning will be had from the following examples:

Example I A cellulose acetate tow comprising a ribbon of continuous filaments which had been lubricated with a mineral oil was crimped as disclosed in Crawford et al. U.S. Patent No. 2,953,837 so that the crimp therein was uniform and free of skips. Filter rods were then made from this tow using our short jet, in accordance with the general apparatus setup of FIG. 2 and the plasticizer application apparatus of Caines et al. application Serial No, 27,091. A /4-inch diameter jet with a W -inch inlet nozzle and 14 p.s.i.g. pressure were employed. Additional tow from the same source was similarly processed using the Venturi style jet of %-inch diameter with a di -inch inlet nozzle. No difference was noted in the manner in which the tow processed, using the short jet or the venturi jet. Following are the results of various tests to which the tow was subjected:

Short Venturi Jet Jet 'lntal denier 46, 000 46. 000 Denier/filament (d. If. 3. 3 3. 3 Crirnps/inch 13 13 Weight of 90 mm. rod, grams 0.585 0. 585 Pressure drop of 90 mm. rod, in F110 10. 9 10. 9 Rod hardness 6. 0 7. 6 Pressure drop of 15 mm. tip, in 1120 2. 1 2. 2- 'Iar removal, percent 32. 5 27. 5 J et air consumption, 0. f. in. free ai 67 81 Static pressure of air at jet entrance, 14

As will be noted, with the circular short jet of the present invention the air consumption was about 17% less and at the same time the reduction in operating air pressure was substantial.

Example I] Short Ven turi Jet Jet Air pressure, p.s.i.g 14 20 Feed roll r.p.m./delivery roll r.p.1n. 1. 22 1. 06-1. 10 Min. pressure drop 8. 8 9. 1 Min. WtJUnit Pressure drop 0. 061 0. 059 Max. pressure drop 5. 2 11. 4 Max. WtJUnit pressure drop 0. 045 0. 053

F 1 Ratio of the linear speed of feed roll 4 to linear speed of delivery roll 7,

6 Example III Considerable improvement in versatility is noted in employing the short jet of the instant invention, in that the range of pressure drop available in filter elements prepared from the debundlized tow product is increased. The following data were obtained using a 3.9 d./f., 54,000 total denier, regular cross-section tow which had been crimped to contain 13 crimps per inch.

The increase in pressure drop range is due to the fact that the tow is plasticized when it enters either jet, where the air applies a tensioning force on it tending to straighten out the crimp. The short jet having only a length of 4 /2" along which the air acts, compared to a venturi jet which has a length of about 12 /2 along which the air acts, lets the tow in the short jet retain its crimp and not have to recover it in the bustle of the jet. The ratio of feed roll to delivery roll being much higher for the short jet indicates that this is true.

Example IV Filter rods were made using the short jet of this invention and employing the general apparatus setup of FIG. 2, using the flat spring fingers and other parts (see FIG. 3). A S'denier per filament tow of 60,000 total denier was processed in said apparatus to produce filter rods having a pressure drop of 10.8 inches of water and satisfactory hardness, circumference, and tar removal efiiciency. The weight of tow contained in the subject rods was comparable to the weight of rods of comparable properties prepared by the method of Caines et al. Serial No. 27,091, referred to above.

Example V Filter rods were prepared from 3.2 d./f., 55,000 total denier tow using the general apparatus setup of FIG. 2, including the round short jet of this invention and flat spring fingers. Rods of satisfactory hardness, appearance and circumference were produced at a pressure drop of 12.8 inches of water having a tar removal efficiency of 15.4% /inch pressure drop.

Therefore, it is apparent from the foregoing examples that satisfactory filters having properties equivalent to those prepared with a venturi jet can be made using the method and apparatus of the present invention which requires less air and lower operating pressures. Further, the available range of pressure drop in the final product is increased.

In the above examples any of the usually used plasti- Y cizers may be employed in the present invention. That is, plasticizers such as triacetin, tripropionin, etc., may be employed. The exact addenda incorporated is not a limitation on the instant invention and will depend to some extent on the characteristics of the particular filter tow which is being processed in the apparatus and the type of filter element or rod which it is desired to be produced. Although the present invention has been illustrated by describing the treatment of cellulose acetate filter tows made up of filaments of a denier per filament of the order of .6l6, as this is the type of filter tow most frequently used in the industry at the present time, the instant invention may be applied to tows or filament bundles of filaments other than cellulose acetate. For example, filament bundles or tows of polyester fibers and polyolefin fibers may be processed in a somewhat simi'iar manner. In the instance of the latter type of filaments which are not susceptible to plasticization, the addenda applied to the crimped filaments may comprise a liquid monomer which will serve to bond the filaments at suitable points, areas or zones as the filaments pass through subsequent filter forming steps.

The amount of air pressure applied to the short jet may and is for economical reasons usually kept to a reasonably low value. However, if desired, the pressure may be extended over the range of to 90 p.s.i.g.'

While our short jet has the same capabilities and limitations as the venturi type jet, one critical factor is that the maximum inside diameter of the bustle is 2 /2 inches. If, when processing tows of 30,00060,000 total denier, the bustle diameter is any larger than 2 /2 inches, the tow will not fill the bustle uniformly and the uniformity of the rods so produced will be decreased. The bustle also operates more efficiently if its inside circumference is smooth and unbroken.

Variations of the size of the nozzle which is employed in our jet are permissible, although a nozzle having 7 inch inside diameter, in combination with the standard E inch spacer and orifice, is preferred. Also, we have found that the length of the throat is not critical since our jets having throat diameters of .75 inch performed well at any length less than 4 /2 inches down to about /2 inch, although at a throat length of 3 /2 inches the bloom of the tow was not as good as at the longer or shorter lengths. However, it is to be understood that other variations in throat diameter, nozzle diameter, nozzle spacing, orifice configuration, etc., are included within the scope and intent of our invention.

As is obvious from the foregoing disclosures, our jet uses less air and at lower operating pressure than a venturi type jet, and the rod pressure drop availability is much greater. The fact that the short jet operates at lower air pressure also results in less tendency to break small filament fragments from the main body of the tow caused by the violent action in the jet. As a. consequence the number of these fragments being blown off from the tow is reduced in the order of 90%. The short jet also offers the economic advantage of requiring a smaller and thereby less expensive air compressor system. Lower air usage also tends to reduce operating costs. In addition our jet is less expensive to manufacture.

It is believed apparent from the foregoing that we have provided a simplified procedure and apparatus combination for the manufacture of filter elements or rods from bundles of filaments particularly special filter tow which distinguishes substantially from prior procedures. It is thought apparent from the foregoing description that it may be noted wherein because of the elimination of the need for rolls, spray booths and the like equipment that certain savings may be secured. Tests of the filter elements produced by the present invention indicate that they are equal to the best filter rods presently commercially available and in certain respects the filter elements produced by the present invention may exhibit properties that excel such commercially available products.

Our invention is not limited wholly to the processing of cigarette filter tow but can be used in any process where the debundlizing of tow is required. The design of the jet might in such situations have to be adjusted for the tow and process involved.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A process for jet treatment of tow in the preparation of filter elements with use of reduced amount of air and lower air pressures coupled with a lessened degree of filament breakage and simultaneously an increase in the available rod pressure drop range for the filter element produced thereby, said process comprising withdrawing a continuous multifilament crimped tow from a supply package, then applying plasticizer to said tow, next passing said tow containing plasticizer into a shortened air-treatment zone under tension created by suction in said zone, subjecting said tow in said zone to an explosive expansion of compressed air with sudden release to atmospheric pressure by expelling tow and air rapidly from a small diameter to a much larger diameter and then conducting through a straight cylindrical passage the length of which is not greater than eight times the inside diameter thereof, said tow being under the influence of an expanding air flow while at the same time being retarded and partially confined by spring fingers as it exists from said straight cylindrical passage, thereby being bloomed under a reduced air pressure and air volume without substantial breakage of filaments, and forming the bloomed tow into a filterforming zone wherein are formed filter elements of increased available filter rod pressure drop range.

2. The process according to claim 1 wherein the filament bundle is a tow of crimped cellulose acetate filaments of a denier per filament of 0.6 to 16 and a total denier of 5,000 to 70,000 and the tow as it is expelled from the treatment zone is retarded and partially confined by spring fingers.

3. The process according to claim 1 wherein the length of the straight cylindrical passage is not greater than eight inches and the inside diameter of the straight cylindrical passage is not greater than an inch.

4. The process according to claim 1 wherein the length of the straight cylindrical passage is 3 to 8 inches and the inside diameter of the straight cylindrical passage is A to an inch.

5. A simplified apparatus arrangement for converting a bundle of filaments into a filter element comprising feed rolls for withdrawing the bundle of filaments from a supply thereof, means in series with the feed rolls for applying addenda to the filaments and for blowing the filaments including a circular jet comprised of a tube entrance element and a shortened straight substantially cylindrical tube-type exit member of a length not greater than eight times its inside diameter whereby operation with a reduced amount of air and at reduced pressure is permitted, an orifice plate positioned between the aforesaid members, said orifice plate and adjacent portions of said tube members being enclosed in a cylindrical housing whereby there is provided a chamber adapted to receive a gaseous fluid supplied thereto so that said fiuid flows through the orifice plate and discharges through the exit member, which jet is adapted to subject the filaments to relatively streamline air fiow in series direction, spring finger filament retarding means between the exit from the jet and further rolls in series, said latter rolls being adapted to withdraw the processed filaments and supply the filaments to filter element forming and wrapping means in series.

6. The apparatus arrangement according to claim 5 wherein the inside diameter of the exit member is /2 inch to an inch and the length of the exit member is 3 to 8 inches.

References Cited by the Examiner UNITED STATES PATENTS 2,794,480 6/1957 Crawford et al. 154 2,924,868 2/1960 Dyer 28-1 3,005,251 10/1961 Hallden et al 28-1 3,097,412 7/1963 Becher 28-1 3,099,594 7/1963 Caines et al. 156152 EARL M. BERGERT, Primary Examiner.

R. I. CARLSON, I. P. MELOCHE, Assistant Examiners.

Claims (1)

1. A PROCESS FOR JET TREATMENT OF TOW IN THE PREPARATION OF FILTER ELEMENTS WITH USE OF REDUCED AMOUNT OF AIR AND LOWER AIR PRESSURES COUPLED WITH A LESSENED DEGREE OF FILAMENT BREAKAGE AND SIMULTANEOUSLY AN INCREASE IN THE AVAILABLE ROD PRESSURE DROP RANGE FOR THE FILTER ELEMENT PRODUCED THEREBY, SAID PROCESS COMPRISING WITHDRAWING A CONTINUOUS MULTIFILAMENT CRIMPED TOW FROM A SUPPLY PACKAGE, THEN APPLYING PLASTICIZER TO SAID TOW, NEXT PASSING SAID TOW CONTAINING PLASTICIZER INTO A SHORTENED AIR-TREAMENT ZONE UNDER TENSION CREATED BY SUCTION IN SAID ZONE, SUBJECTING SAID TOW IN SAID ZONE TO AN EXPLOSIVE EXPANSION OF COMPRESSED AIR WITH SUDDEN RELEASE TO ATMOSPHERIC PRESSURE BY EXPELLING TOW AND AIR RAPIDLY FROM A SMALL DIAMETER TO A MUCH LARGER DIAMETER AND THEN CONDUCTING THROUGH A STRAIGHT CYLINDRICAL PASSAGE THE LENGTH OF WHICH IS NOT GREATER THAN EIGHT TIMES THE INSIDE DIAMETER THEREOF, SAID TOW BEING UNDER THE INFLUENCE OF AN EXPANDING AIR FLOW WHILE AT THE SAME TIME BEING RETARDED AND PARTIALLY CONFINED BY SPRING FINGERS AS IT EXISTS FROM SAID STRAIGHT CYLINDRICAL PASSAGE, THEREBY BEING BLOOMED UNDER A REDUCED AIR PRESSURE AND AIR VOLUME WITHOUT SUBSTANTIAL BREAKAGE OF FILAMENTS, AND FORMING THE BLOOMED TOW INTO A FILTERFORMING ZONE WHEREIN ARE FORMED FILTER ELEMENTS OF INCREASED AVAILABLE FILTER ROD PRESSURE DROP RANGE.

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