US 3099594 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
July 30, 1963 J. F. CAINES ETAL METHOD FOR BLOOMING FILTER TOW 2 Sheets-Shee t 1 Filed May '5, 1960 SUPPLY OF TOW TOW FEED BLOOMING AND OF ADHESIVE ATTITUDE TOW CREATION FEED Fig.
STUFFING AND CIGARETTING PRODUC STIFFENING Fig. 4
JAMES F CAM/E5 R/CHARD E DYER J. KNOX PAN/V/LL JR.
INVENTORS A TTOR/VEYS uly 30, 1963 J. F. CAINES ETAL 3,099,594
METHOD FOR BLOOMING FILTER TOW v I 2 Sheets-Sheet 2 Filed May 5, 1960 JAMES F CAM/ES R/CHARD E DYER J KNOX PA/VN/LL JR.
INVENT United States Patent 3,099,594 METHOD FOR BLOOMING FILTER TOW James F. Caines, Richard F. Dyer, and James Knox Pannill, In, Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed May 5, 1960, Ser. No. 27,091 Claims. (Cl. 156-152) This invention relates to a new method and apparatus for processing tow into tobacco smoke filter elements. More particularly, this invention concerns a process and apparatus of the class indicated wherein tow may be manufactured into tobacco smoke filter elements of a high quality with fewer steps and with less apparatus than heretofore required.
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 (one of the inventors herein) 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 efficiently and better handle tow. Also, such type modification with a slot jet permits the better processing of tow of a wider denier range.
Although the foregoing processes and constructions satisfactorily fufill the needs of many filter manufacturing installations, with the advent of the need of additional installations as well as the desirability of the greater facility for processing certain of the tows now available, a demand has arisen for further simplified and improved processes and apparatus. It is apparent, therefore, that the developrnent of new and simplified process and apparatus for the production of the tobacco smoke filter elements represents a highly desirable result.
After extended investigation we have found a process and apparatus for making filter elements of the class indicated and of a quality at least equivalent or in certain instances better than the presently produced filter elements, but wherein the process is simplified and wherein there is substantial apparatus saving in making the constructions needed for carrying out the instant process.
This invention has for one object to provide a novel and simplified method and apparatus for the manufacture of tobacco smoke filter elements. Another object is to provide a method which does not involve as many steps or require as many apparatus components as heretofore used in the industry to produce filter elements of existing quality. Still another object is to provide a simplified process and apparatus combination for converting filter tow to filter elements which is adaptable to the processing of a wide range of tow deniers. Still a further object is to provide a jet construction specially suitable for processing tow which is being converted to filter elements. Another object is to provide such jet construction equipped with facilities for the introduction of plasticizer or the like 3,099,594 Patented July 30, 1963 "ice 2 addenda into contact with the tow and to prevent the escape thereof in the exhaust from the jet. Other objects will appear hereinafter.
In the broader aspects of our invention we have found that a plasticizer in particular or the like or equivalent addenda 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 or the like addenda are 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. Procedure in accordance with the present invention is in contrast to prior methods and apparatus wherein the plasticizing or the like treatment is accomplished after considerable mechanical treatment of the tow. As apparent, there-fore, the present invention saves operative steps and apparatus parts as well as eliminates the possibility of substantial mechanical abrasion and breaking of filaments.
For assistance in a better understanding of the present invention reference is made to the attached drawings forming a part of the instant application.
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 a circular jet such as may be used in carrying out the process of the present invention.
FIG. 4 is a side elevation view of a jet construction as in FIG. 3 but wherein the jet has been provided with additional parts for facilitating the introduction of plasticizer.
FIG. 5 is a side elevation view somwhat similar to FIG. 4 but wherein the jet is shown in section for better illustrating wherein the addenda adding conduits and the like parts may be associated with the jet.
FIG. 6 is a side elevation view somewhat of a schematic nature for illustrating the combination of preferred plasticizing apparatus parts in association with the circular jet of the instant invention.
Referring to FIGURE 1, the process of the present invention may be seen to consist primarily of the combination step of blooming and creation of adhesive attitude preceded and followed by tow feed steps. By comparison with FIGURE 1 of the aforementioned Patent 2,794,480, it can be seen that simplification and combination of functions have been effected by combining the opening step and eliminating the fluffin-g step shown therein.
Referring now to FIG. 2, the process of the present invention 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 compresed air in a specially adapted venturi nozzle 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. application Serial No. 761,602 or as in Crawford and Stevens US. Patent 2,794,480 and then to a cigaretting machine 9.
Referring to FIG. 3, the basic circular jet will now be described. It will be noted that the jet is of the same general design and configuration as the jets described in Dyer application Serial No. 609,642, now U.S. Patent 2,924,868. However, differences reside in the provision of multiple air inlets to the jet body and a major revision of the venturi tube design. Extensive study has shown that the most efiicient venturi jets from the viewpoint of minimum energy losses have a relatively small ratio of venturi throat length to throat diameter. However, it has been found that venturi jets of conventional design are not effective in blooming and debundleizing continuous multifilament tow containing several thousand highly crimped filaments in the order of 0.6 to 16 denier per filament. It was found that the most effective blooming was obtained when the venturi throat length to diameter ratio was increased drastically to a ratio of about 6 to 1. Moreover, the exit flare or diverging portion of the nozzle should have an included angle of about 3 to 5 degrees rather than 7 to '10 degrees. It might also be pointed out that -use of just a long straight tube with no divergent exit angle gives poor blooming and debundleizing action. Thus the venturi tube design is of some importance to obtain optimum tow blooming and complete debundleizing or separation of the individual filaments from each other.
Referring to FIG. 3, the jet is composed of an outside shell '10 containing several inner members 11, 13 and 14 held in place by threaded plugs 12 and 15. A passageway '16 extends through the jet device so that the continuous multifilament crimped tow may be passed from the entrance 17 in member 11 to an exit 18 in member 14. The passageway in member 11 form diameter. The outer surface 19 of the lower end of 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 thin plate orifice plate 13, an annular orifice or passageway for metering the air floiw into the venturi tube member 14.
The venturi tube member 14 is provided with a converging entrance section 21 of about 30 to 40 degrees included angle, and in series a straight cylindrical tube passage 22 having a length of from 2 to times the inside diameter of the passage 22, and a flaring or divergingexit section 23 with an included angle of from 2 to 7 angle.
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 passage 22 is too short, or the exit angle of passageway 23 is too great, less than optimum blooming will result. Likewise, if passage 23 has little or no exit angle flare, the blooming of the tow will also be poor. Best results are obtained when the length of passageway 22 is about six times its inside diameter and the included angle of the exit passage 23 is about 3 to 5 degrees.
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 is substantially of uniflow. 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 shell 10 through one or more openings 24 and 24' to an annular chamber formed by the outer surface of inlet member 11 and shell 10 and sealed at one end by threaded plug 12. It has been found that, while one inlet 24 is often adequate, better air flow distribution can be obtained with two or more openings equi-spaced around the shell periphery. The air from the chamber 25 then impinges on the tow by passing through the annular orifice formed by the tapered portion 19 of inlet tube 11 and the tapered opening 20 in 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 non-critical surfaces can be made without departing from the spirit of the invention.
The critical relationships for a typical preferred jet for processing 37,000 total denier, 1.6 denier per filament tow are given in the following Table A:
Table A Inside diameter of tube 11 inches 0.250 Angle of taper 19 on end of tube 11 degrees 60 Orifice plate opening diameter inches 0.468 Orifice plate entrance angle 20 "degrees" Orifice plate thickness inches 0.125 Venturi tube entrance angle 21 degrees 35 Venturi tube throat diameter 22 inches 0.750 Venturi tube throat length 22 do 4.50 Venturi tube exit angle 23.; degrees 5 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 venturi member 14 is retarded and partially confined. To achieve this end, a plurality of flat spring fingers 2.6, 26, 26 and others (not shown) are positioned equidistant around the outer surface of the venturi member 14 and extend beyond the end of the member 14 a distance of 3" to 8". The fingers 26' are curled slightly outward at 27 to avoid snagging the tow, are slidable axially on the member 14, and are held in place by a clamp ring 28 and suitable thumb screw tightening means 29. The force to spring the fingers outward is adjustable by moving the clamp 28 closer to or farther away from the end 18 of the member 14.
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 debundleizing 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 circular jet described in FIG. 3 whereby the plasticizer or like material may be incorporated on the tow as the tow passes through the jet. In further detail, referring to FIG. 4, the air supply line 30 to the circular jet 6 has connected in series along its length a pressure regulator 31 and a liquid atomizing unit 32. After leaving the atomizer unit 32 the air line is branched at 33 to provide as many smaller air supply connections as required by the jet shell 10. The plasticizer liquid in the form of an aerosol generated in the atomizer 32 is conveyed in the air to the jet 6 and impinges along with the air on the tow as it passes through the jet orifice plate. Several suitable means are commercially available for generating the aerosol from the plasticizer, such as the air line lubricators made by the Alemite Company of Chicago, Illinois, and it is not desired to be restricted to any particular type of aerosol generator. In many cases the system of plasticizing the tow shown in FIG. 4 may be satisfactory in the manufacture of certain filter elements.
Reference is now made to FIG. 5 wherein there is shown another type modification of the circular jet whereby the plasticizer may be introduced directly into the jet and onto the tow being processed therein. A plurality of metering gear pumps 36, 36 and as" are connected to a supply tank 35 of plasticizer liquid. The down-stream side of each pump is connected through pipe lines 37, 37 and 3/7, to a capillary tube probe having a small opening at the entrance end. One or more of these probes 38 and 39 are positioned in the exit flare of the venturi member 14. One or more other probles 40 are located in the tow entrance tube 11 and discharge near the orifice plate 13. As the plasticizer emerges from these probes it is distributed by the high velocity jet air onto the tow filamerits.
Consideration will now be directed to FIG 6 which figure in certain respects corresponds with FIG. 2 and represents the preferred apparatus and process embodiment of the instant invention. -In referring to PEG. 6, two metering gear pumps '56 and 56 are connected to a supply tank 55 of plasticizer. The output of these pumps is connected by flexible hose or tubing 50 and 50 to slit tube applicators 51 and 51'. The tube applicators are stainless tubing having a narrow 0.01 to 0.06 slit cut longitudinally along one side. The tubes are sealed at each end by end plates. One end plate is provided with a threaded connection to the flexible tubing 50. The slits may be covered with thin felt and/ or a fine mesh screen to help evenly distribute the flow of the plasticizer along the len th of the slits. The hollow tube applicators are rigidly fastened to an arm 62; pivoted about the axle 63. At one end of the 'arm 62 the piston rod of an air cylinder 64 or solenoid is connected with a hinge pin. The cylinder is anchored to the machine frame by a hinge pin at 65 The slot tube applicators are so mounted that one slot faces generally downward and the other generally upward. The tow 71 passes under the downward facing slot 51 and over the upward facing slot 51, snubbing 5 to 30 on each slot tube. As the tow fed through the nip of feed rolls 4 passes under and over the slot tubes a controlled amount of plasticizer is metered onto the tow. The air cylinder or solenoid 64 is coordinated with the start-stop means of the tow blooming apparatus to rotate the slot tubes counterclockwise out of contact with the tow when the machine is stopped and clockwise into contact as the machine is started. This prevents wicking of too much plasticizer onto spots on the tow when the machine is at rest. The tow passes over the straight tube applicators as a fiat ribbon about 2" to 6" wide and as it enters the jet 75 is compacted into a cylindrical form. Thus, although every filament may not have received an application of plasticizer from the applicators, any local point in the crosssection of the tow has filaments that did receive plasticizer. The amount of plasticizer on these filaments is in general in excess of that required to bond the filaments together adequately. When the tow is subjected to the high velocity explosive blast of air in the jet orifice plate 13 (FIG. 3) and ventuni tube 14, the excess plasticizer on hese filaments is blown olf 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 spring fingers 26, 26, etc. (FIG. 2) at the exit of the venturi tube 14 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 eificient 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 sufficient velocity energy to blow off and remove plasticizer from the surface of the bloomed filaments. Without the presence of the retarding spring fingers 26 the filter mass would not be formed at the exit of the jet and poorer distribution of the plasticizer would ensue as well as excessive losses of plasticizer to the atmosphere. However, in the present invention the processed tow 72 (FIG. 6) is well bloomed and plasticized.
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 as well as an understanding of the process of the present invention will be had from a consideration of the several specific examples which follow and which are set forth to illustrate certain preferred embodiments of the instant invention.
Example I Filter rods were made by the round venturi jet of this invention using the general apparatus setup of FIG. 2 and the plasticizer application apparatus of FIG. 4 and using 37,000 denier tow containing about 23,200 filaments having an average size of 1.6 denier. For comparison, filter rods were made of the same tow using the slot venturi apparatus and method of Dyer et al. application Serial No. 736,900. Also, a comparison was made with the tension blooming method of the prior art with a 72,000 denier, 2.0 denier per filament tow. The physical characteristics of the filter rods and the processing comments were as follows:
Present invention Slot Tension circular venturi blooming venturi Total denier 37,000 37, 000 72,000 Denier/filament (D /F 1.6 1. 6 2. Crimps/ineh 16.0 16. 0 17.0 Weight of mm. rod, grams. 0.63 0. 670 0.87 Pressure drop of 90 mm. rod, in. H20... 15. 4 16. 8 13. 3 Rod hardness 10. 1 8.8 8.9 Pressure drop of 15 mm. tip, in. H10. 2. 94 3.0 2. 4 Tar removal, percent 42. 4 43. 8 34. 0 Jet air consumption, C F M. free a 4 None Rod test designation 1 CLY 4 ARK 1 AXM In this example, 1.6 D./F., 37,000 total denier tow was processed using the same setup as used for the round venturi jet blooming of Example I except the probe application of FIG. 5 was used for applying the plasticizer. Filter rod characteristics were substantially as obtained in Example I.
Example 111 Example II was repeated using the slot tube applicator of FIG. 6. The plasticizer was applied with a uniformity equal to that generally obtained with a spray booth and banded tow. Rod hardness was acceptable. No differences in filtration properties were noted compared to the rods obtained by this invention in the above examples.
While the method of applying the plasticizer to the tow has been described in relation to three specific forms of apparatus, it will be recognized that other forms of apparatus might be used. For example, kiss roll applicators might be substituted for the slot tube applicators of FIG. 6. A kiss roll applicator is illustrated in Head US. Patent No. 2,807,864.
Example IV Filter rods were made using the round venturi jet of this invention and employing the general apparatus setup of FIG. 2, using the flat spring fingers 26, 26, 26" and other parts (see FIG. 3). A 1.6 denier per filament tow of 18,500 total denier was processed in said apparatus to produce filter rods having a pressure drop of 16.7 inches of water and satisfactory hardness, circumference, and tar removal efiiciency. The Weight of tow contained in the subject rods was 7% less than the weight of rods of comparable properties prepared by the method of Dyer et al. Serial No. 736,900, referred to above.
Example V Filter rods were prepared from 3 D./F., 33,000 total denier tow using the general apparatus setup of FIG. 2 including the round venturi jet of this invention and the flat spring fingers of FIG. 3. Rods of satisfactory hardness, appearance and circumference were produced at a pressure drop of 12.0 inches of water having a tar removal eificiency of 29.7%. Filter rods produced by the mechanical '(roll) method of the prior art from a 3 D./F., 80,000 total denier tow at the same pressure drop contained 24% more tow for a tar removal elficiency of 29.0%, namely for a removal about the same as the filters of the present invention.
Example VI A tow containing 9,000 filaments averaging approximately 5.0 denier was used to prepare filter rods using the apparatus of FIG. 2, especially the round venturi jet of this invention, and the flat spring fingers of FIG. 3. At a pressure drop of 9.4 inches of Water, which is comparable to that of a 5 D./F., 85,000 total denier tow processed into a filter rod of similar dimensions using the tension blooming method of the prior art, a rod weight of 0.810 gram was found to be associated with satisfactory hardness and appearance. The filter rod produced by prior art tension blooming from 5 D./F., 85,000 total denier tow at equal pressure drop weighed 0.965 gram, or 19.0% more.
Therefore, it is apparent from the foregoing examples that filters of equivalent properties which require less material can be made using the method and apparatus of the present invention. Further, the size of the tow required to accomplish this may be considerably smaller than that used in the mechanical method of the prior art and this feature possesses some additional advantages.
In the above examples any of the usually used plasticizers may be employed in the present invention. That is, plasticizers such as triacetin, tripropionin, etc. may be employed. The exact addena 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 .6-16, 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 fila ments other than cellulose acetate. For example, filament bundles or tows of polyester fibers and polyolefin fibers may be processed in a somewhat similar manner. In the instance of the latter type of filaments which are not susceptible to plasticization, the addenda applied to 5 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 circular 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 5 to 90 p.s.i.
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.
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 eifected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.
1. In a process of manufacturing filter elements from a bundle of crirnped, continuous filaments, the improvement feature which comprises applying an addendum to the filaments, passing the filaments thus treated with addendum through a jet whereby the addendum is distributed over the filaments and the filaments put out of registry and retarding the exit of the filaments from said jet.
2. In a process of manufacturing filter elements from crimped, continuous filaments, the improvement feature which comprises applying an addendum to the filaments, passing the filaments thus treated with addendum into a jet supplied with high velocity gas whereby the addendum is further distributed on the filaments and the crimp in the filaments put out of registry and retarding the exit of the filaments from said jet so that the retarded filaments act as a filter thereby filtering out addendum from gas exhausted from the jet.
3. A process in accordance with claim 2 wherein the addendum is principally comprised of plasticizer for said filaments.
4. In a process of manufacturing filter elements from crimped, continuous synthetic filaments the improvement feature which comprises passing said filaments into and through .a jet supplied with high velocity gas which gas acts upon the filaments, retarding the exit of the filaments from the jet immediately adjacent the exit from the jet whereby said retarded filaments may act as a filter for the gas exhausted from the jet.
5. A process in accordance with claim 2 wherein the filaments are initially comprised of cellulose acetate of a denier per filament of the order of 1.6 to 5.0 and a total denier of the order of 37,000 to 85,000.
6. The process of manufacturing filter elements from a bundle of filaments contained in a package which comprises withdrawing the filaments from said package, applying an addendum to the withdrawn bundle of filaments and subjecting the filament bundle to a jet of air injected in streamline relatively non-turbulent flow in the direction of advancement of said filament bundle whereby the filament bundle is bloomed, retarding the exit of the bloomed filament bundle from the jet by a mechanical barrier means and then passing the filament bundle thus processed to further steps including the forming of the processed filament bundle into the desired filter element shape.
7, -A process in accordance with claim 6 wherein the filament bundle is a tow of crimped cellulose acetate filaments, the addendum is a plasticizer for cellulose acetate and the barrier means comprises spring fingers.
8. A process of manufacturing filter elements from tow which comprises withdrawing the tow from a supply thereof in the form of a narrow tow ribbon applying plastioizer to the ribbon then passing the ribbon into and through a circular jet supplied with a fluid in relatively streamline flow in the direction of advancement of the tow ribbon whereby the tow ribbon is opened up to some extent, retarding the exit of the blown tow from the jet whereby plasticizer is prevented from blowing off the tow into the surrounding environment and conducting the blown tow in a relaxed condition to further steps including the compacting thereof into the desired shape.
9. A process in accordance with claim 8 wherein the plasticizer is applied to the tow ribbon first on one side then on the other.
10. A process in accordance with claim 8 wherein the tow is comprised of crimped cellulose acetate filaments and the plasticizer applied in an ester.
References Cited in the file of this patent UNITED STATES PATENTS Kline et al. July 29, Modigliani Feb. 13, Croft Apr. 18, Rainard Nov. 20, Wyss et a1 June 24, Swann -a Jan. 10, Rainard et al. Feb. 1 4, Schroeder Oct. 9, Hackney et a1. Dec. 18, Uhleen Mar. 12, Crawford et a1. June 4, Crawford et al. June 4, Head Oct. 1, Slayter et al. Dec. 1, Hall Nov. 1,
FOREIGN PATENTS Canada Mar. 111,