US2440226A

US2440226A - Method and apparatus for producing and stretching artificial yarn

Info

Publication number: US2440226A
Application number: US673446A
Authority: US
Inventors: Howard W Swank
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1943-08-19
Filing date: 1946-05-31
Publication date: 1948-04-20
Anticipated expiration: 1965-04-20

Description

April 20, 1948. I H. w. SWANK I 2,440,226

METHOD AND APPARATUS FOR PRODUCING AND STRETCHING ARTIFICIAL YARN Filed May 31, 1946 4 Sheets-Sheet 1 INVEN TOR A I TURNE v.

April 1948- H. w. SWANK 7 2,440,226

METHOD AND APPARATUS FOR PRODUCING AND STRETCHING ARTIFICIAL YARN filed May 31, 1946 4 Sheets- Sheet 2 INVENTOR B I fiawapolllswnm A TTOENEY.

April 20, 1948- v H. w. S'WANK 2,440,226

METHOD AND APPARATUS FOR PRODUCING AND STRETCH ING ARTIFICIAL YARN Filed May 31, 1946 4 Sheets-Sheet 3 INVENTOR B HOWAkDWSH/ANA nrromvtx April 20, 1948. H. W.'SWANK 2,440,226

METHOD AND APPARATUS FOR PRODUCING AND STRETCHING ARTIFICIAL YARN Filed May 31, 1946 4 Sheets-Sheet 4 'INVENTOR Hon 4,00 WSW/91w" A TTORNEY Pa tented Apr. 20, 1948 METHOD AND mm'rus ron raonvcmo am) s'rasrcnmc, aarmcmr. man

Howard w. Swank, Richmond, vs. assignor to E. I. du Pont de Nemours & Company, Wiln, Del, a corporation of Delaware Application May :1, 1m, Serial No, 873,446

' 21 Claims. (01. 18-8) 1 This invention is a continuation-in-part of copending application Serial No. 499,162. filed August 19, 1943, and relates to the manufacture of regenerated cellulose yarn from viscose. More particularly, this invention relates to a method and apparatus for drawing freshly spun, yarn around a feed wheel for use in the production of viscose rayon and particularly for use in the hot dip method to produce high tenacity regenerated cellulose yarn of substantially uniform physical characteristics.

United-States Patents No. 1,901,007 of March 14, 1935, and No. 1,996,989 of April 9, 1935, disclose procedures for producing viscose rayon of improved tenacity by passing the coagulated partially regenerated filaments through a hot aqueous bath heated to 70 C. to 100 C. and, while the filaments are in contact with such hot aqueous bath, subjecting them to substantial tension and/or stretching. In each of the procedures disclosed in the aforementioned patents, the amount of swelling or plasticizing of the yarn by the hot water treatment was not readily controllable and the application of stretch over a substantial length of the yarn did not give consistent reproducible results so that a product of uniform characteristics could be obtained.

United States Patent No. 2,248,862 of July 8,

1941, discloses a hot bath stretching arrangement wherein the first feed wheel is partially immersed in the hot bath and whereby the hot bath is applied only at the bottom of the feed wheel. The application 01 the hot bath to the first feed wheel only at the bottom thereof limits the takeoif point of the yarn to the side of the feed wheel and at a point not greater than 60 from the point where the feed wheel contacts the hot bath if the thread is to be at the maximum temperature (and this is necessary for optimum re-- sults) at the time of stretching. If the thread were taken off at some other point greater than 60 from the point of application of the hot bath, such as from the top of the first feedwheel in its passage to the second feed wheel, the temperature of the thread at the time of stretching would be less than the temperature of the bath due to cooling by evaporation from the feed wheel.

Additionally, such arrangement is objectionable in that it prevents-the imposition of the maximum possible spinning tension, such as of the order of 1 gram per denier, between the two positively driven rollers. It is well recognized that the tenacity of yarn produced is dependent to a very large extent on the amount of tension imposed on the partially regenerated yarn, and

formed yarn is apparently due to the fact that stationary yamdirectional guides are used and the frictional resistance to the travel of the yarn makes it necessary to spin at lower tensions than would be possible if the yarn came in contact with'substantially no frictional resistance. Further, the application of a hot bath to the yarn passing around theroller, as disclosed in said Patent No. 2,248,862, is not suited to the optimum control of stretching as will be more fully explained hereinafter.

slippage of the freshly formed yarn on the feed wheels when yarn was being spun by the bucket spinning process was a. major problem some years ago. The use of double wraps around the feed wheel and especiallythe use of a freely rotatable snubber guide roller, such as shown in United States Patent No. 1,977,611, was decidedly helpful in the development of yarn of more uniform properties. However, in the spinning of large denier yarns, such as 1100 denier,

under high tension, and especially when the yarn is treated with a hot aqueous bath and stretched a. substantial amount, a small number of the filaments are commonly broken. Thehot bath does not act instantaneously on all the filaments comprising the bundle and, as soon as most of the filaments become plasticized, they stretch, releasing a large part of their load to the less plasticized filaments which bear or try to bear an unproportionally large load, and finally break.

Thesebroken filaments most frequently wrap around the snubber guide roller, continue tobuild up, and often cause other filaments to break, until the entire bundle breaks or until the wrap becomes so large as to prevent normal operation of the roller.

In addition. the advent of much higher spinning tensions (of the order of 1 gram per denier) made necessary in order to maintain a high degree of uniformity a plurality of complete wraps around the feed wheel and two or more wraps around the snubber roller guide. While slippage of the yarn on the stretching wheel was thus avoided, increased roller wraps were a barrier against any practical application. It is, of course, apparent that in spinning at tensions well below the yarn breaking tension many of these difliculties never arise. Nevertheless. when spinning at speeds 25% to 50% higher than commonly used and at maximum tensions on the filament bundle within 80% to 95% of the breaking tension, what would normally be considered extremely minor irregularities become of extreme importance and the procurement of optimum benefits from this extremely high tension spinning are vitally dependent on every minute refinement.

It is an object of this invention to provide an improved process for drawing freshly spun yarn around a feed wheel.

Another object is to present the yarn to the feed wheel during its passage therearound in a substantially uniform bundled form free of floating or wandering filaments.

Another object is to presentithe yarn to be. stretched in a uniformly bundled form substantially free of floating or wandering filaments.

Another object of this invention is to stretch the freshly spun viscose rayon yarn impregnated with a hot aqueous liquid between two feed wheels and substantially reduce or indeed inhibit the formation of filament wraps on the snubber guide roller.

A further object of this invention is to provide an apparatus for carrying out the aforementioned process.

A still further object of the invention is to provide a novel means for bundling the freshly formed yarn to. prevent filament wraps on the snubber guide :oller.

mentioned. The peripheral speeds 'of the feed wheels are such as to impose in the yarn a total tension of the order of 1 gram per denier. As will become apparent hereinafter, the stretch is confined within a short distance in the path of travel of the yarn (as it comes onto the first feed wheel and as it leaves said feed wheel) and at a time when the yarn is uniformly impregnated with the hot aqueous bath.

In that embodiment-of this invention which is directed to improvements in the process involving hot aqueous bath stretching the bath may be water, acidulated water, or a viscose regenerating bath of the same or different composition as that into which the viscose is initially spun. It has been found that optimum results are obtained by applying to the yarn to be stretched a bath heated to a temperature of about 90 C. to 95 C. so that stretching will take Place in yarn that is not below 85 C. at the region and time of stretching, although excellent results can often be obtained by impregnating the yarn to be stretched at much lower temperatures, such as at 75 C. or thereabouts.

The details of the invention will become more apparent by reference to the accompanying drawings when taken in connection with the fol- I lowing detailed description.

A still further object is to provide a novel snub- I ber guide roller.

Other objects will be apparent from the description hereinafter set forth.

The objects of the invention are generally accomplished by passing freshly spun viscose rayon yarn one or more times over and around a feed wheel and, between each successive pass of the yarn over the feed wheel, passing the yarn under a freely rotatable snubber roller that prevents the yarn from tracking on itself and imparts a twist to the yarn immediately prior to its contact with the snubber roller. The twist greatly reduces the formation of filament wraps on the snubber roller and is substantially removed, leave ing the filaments bundled together and the yarn substantially free from loose and wandering filaments before the yarn again contacts the feed wheel. The yarn leaving the feed wheel can be collected in an appropriate collection device. In another embodiment of the invention, freshly spun viscose rayon is stretched between two positively driven feed wheels, the yarn passing one or more times around the first feed wheel and a plurality of times around the second feed wheel. While the yarn is on the first feed wheel, it is uniformly impregnated with a hot aqueous liquid. In the passage of the yarn over and around the first feed wheel, the yarn is passed under a freely rotatable displacement snubber roller to prevent the yarn from tracking onitself and to impart twist thereto. The twist is imparted to the yarn at a point immediately prior to its contact with the snubber roller, and the formation of filament wraps on the snubber roller is greatly reduced. The twist is substantially removed, leaving the filaments bundled together and the yarn substantially freeof loose or wandering filaments, before the yarn again contacts the first feed wheel. The yarn is then passed over and around the second feed wheel, which is also provided with a snubber roller guide. of the type previously In the drawings,

Figure 1 is a perspective view, partly in section, showing an apparatus suitable for carrying out the invention;

Figure 2 is a front elevation of the first stretching wheel and the snubber roller cooperating therewith, and also showing the zone of hot bath application;

Figure 3 is a side elevation of the set-up shown in Figure 2;

Figure 4 is an enlarged front elevation, partly in section, of the means for applying the hot aqueous bath;

Figure 5 is a top plan view, broken away for clarity, showing the arrangement of the snubber roller with respect to the feed wheel;

Figure 6 is a modified form of snubber roller suitable for use when two passes of the yarn are made about the snubber roller;

Figure 7 is a section of another modified form of snubber roller suitable for use when two passes reference numerals designate like parts, the reference numeral ill designates a multi-hole spinneret through which the viscose solution, supplied thereto through a conduct l2, is. extruded into a spinning bath l4 contained in a. trough I. The filaments I8 extruded within the bath through the spinneret iii are passed around guides 20, 22, 24, 26 and 28 positioned beneath the level of the bath. The guide 28 is designed to impose a tension on the yarn and may be of the type shown in United States Patent No.'2,083,251. The yarn 30 is withdrawn from the bath H by a positively driven feed wheel 32 and passed once around said feed wheel 32. In its passage over,,

pluralityv of times around a second positively driven feed wheel 33. The yarn 33, in its passage around the feed wheel 33, also passes under a freely rotatable snubber roller 33. The feed wheels 32 and 33 are mounted on shafts "and -42, which are driven by means (not shown) at such rates that the peripheral speed of the wheel 33 is greater than the peripheral speed of the wheel 32 whereby the yarn between said wheels is stretched, After leaving the feed wheel 33, the

the let be determined to control the amount of preliminary stretch to give the best results. By this process. the yarn that is stretched in the primary bath is then given a preliminary small amount of stretching before becoming positively engaged on the feed wheel and is then brought to a temperature of about 90' C. just prior to its flnal yarn is collected in a rotating bucket 44 into which it is guided by a reciprocating funnel 43.

While the yarn 30 is on the first feed wheel 32, it is impregnated with a jet of hot aqueous bath 50.

The feed wheel 32 is provided at the rear thereof with an upwardly inclined (slinger ring) flange 54, from which the hot bath liquid applied to the feed wheel is discharged into a collecting shroud 58 from which it is removed by a conduit 58. In order that the bath be discharged from the feed wheel 32 only at the flange 34, the Jet of hot liquid 30 is applied to the upper portion of the feed wheel 32 within therange of 120. as shown in Figure 2, and the thread-contacting portion 59 of the feed wheel is constructed with a slighttaper, as indicated by the reference character A in Figure 3, to insure that centrifugal force will drive the "liquid from the thread-contacting portion 53 of the feed wheel 32 to the point of the flange 34 before discharging it from the wheel. While this taper A may be no more than 1", preferably it is greater than 3", but in no case more than 6 or 8.

The region of application of the jet ill will vary with the contour of the feed wheel 32, the peripheral speed and radius thereof. when the yarn '30 leaves the wheel 32 at the top, as indicated in Figure 2 by the reference character T, the Jet 50 is located preferably at an angle of 10 or anywhere within the 75? angle, designated as C in Figure 2. When the yarn leaves the wheel 32 from the side, referred to as "alternate route of thread" and designated by the reference character S, the Jet 30 is directed onto the wheel 32, preferably at the top center or anywhere within the 45 angle marked D. In these embodiments, the Jet of hot bath liquor II is applied to the yarn within a. zone of an angle of about 90 from the point the yarn leaves the wheel, and it is preferably also so directed as to have a component of its velocity in the .direction of rotation of the wheel 32.

Part of the stretching of the yarn 30 takes place over the surface 39 of the feed wheel 32 just before the yarn loses contact with the wheel. resulting in slippage of the yarn on the wheel. It is, therefore, important that the yarn be in the most plastic condition possible to keep this slippage at a minimum, and to provide plenty of lubrication by means of a liquid so that this slippage will not damage the yarn. Some slippage also occurs in the region where the yarn 30 first contacts the wheel 32. since the surface 59 of the wheel is wet with the hot treating liquor. The tension device 23 located in the spinning bath i4 serves as a retarding force on the yarn, which stretches the partially heated yarn on the feed wheel before sufficient contact of the surface is present between the yam and the feed wheel to prevent slippage. It is, therefore. very important that the point of application of the hot bath jet 50 be uniform on the wheel 32 from position to position and that the desired point of application of wheel 32.

stretching between the feed wheels. The optimum location of the Jet will vary somewhat, as previously indicated. depending on the peripheral speed and radius of the feed wheel.

Several factors are considered in the construction of the Jet and the exact angle of impingement of the bath on the wheel. The temperature of the hot aqueous bath liquid drops from the time it first contacts the yarn until it is removed from the wheel. The absolute temperature drop across the wheel will be determined by the absolute magnitude of flow of the hot bath. Since it is desired to keep the temperature drop at a minimum, fairly large flows of hot bath are used.

In the form shown in the drawings, the Jet 30 is obtained through the use of a pipe 82, which is provided with an oriflce 34 at a suflicient distance from the mouth of the pipe to permitthe Jet 30 to be. supplied in a smooth large flow and to prevent splashing of the Jet when it impinges on the The pipe 32 is secured to the shroud. as shown in Figures 2 and 3, and thehot bath liquid is supplied at a constant pressure to the top thereof from a source (not shown).

As previously mentioned, the jet is directed so as to have some component of its velocity in the direction of rotation of the wheel. The yarn lies on the feed wheel in the form of a ribbon, due to the extremely high tension imposed on the yarn and its normal tendency to hug the wheel, and the direction of the jet upon this ribbon of yarn with positive force achieves mort rapid penetration of heating liquor into the yarn.

It is desirable to eliminate all sharp corners or edges from the feed wheel 32, thereby eliminating points and edges from which the bath may be discharged from the feed wheel rather than be pumped to the slinger ring flange 34 where it is discharged into the shroud 33. The proper contour of the feed wheel 32 is also partially determined by the angl between the plane of rotation of the feed wheel 32 and the horizontal. If the 'thread-contacting. surface 88 slopes too steeply from the flange N to the front of the feed wheel 32, gravity partially overcomes centrifugal force and the treating liquor is discharged from the front of the feed wheel. The flow of hot bath along the upper surface of the wheel is aided by tilting the plane of rotation of the wheel from the vertical by an amount approximately equal to the degree of taper of the feed wheel. a

In the set-up shown in Figures 1, 2 and 3, the yarn 30 is given one pass under the snubber roller 34. In such a set-up. the snubber roller 34 may be like that described in United States Patent No. 1,977,611. As described in said patent, the snubber roller 34 has a frusto-conical thread-contactingportion 33 and an upwardly inclined flange 83 at the rear thereof. The snubber roller 34 is freely rotatable on a stud i0, and the flange i3 is positioned within a shroud 12. ,A pipe 14 conducts any liquor, which passes from the snubber roller 34 to the shroud 12, to the conduit 33.

In order to satisfy the requirements of this in vention. the snubber roller 34 must be positioned passing through the axis of the feed wheel by a small angle of about 6' or 8'.

By locating the snubber guide 30 in thisfmannor, the yarn 30 coming down from the feed wheel 02 first contacts the flange of the snubber 00 and, due to the askew position thereof, rolls down the flange onto the (less tapered) frustc-conical body 00. Because the yarn rolls on itself in coming onto the snubber roller 04. it develops temporarily a certain amount of twist. The twist actually takes place between the point at which the yarn leaves the feed wheel I! and the contact point with the snubber guide roller 04, so that the yarn contacting the snubber roller 34 is well bundled and broken filaments are not picked up and wrapped around the snubber roller 34 but are carried along as part of the continuous filament bundle. when the yarn leavesthe snubber roller 04 and travels to the feed wheel 32, thetwist is removed. However, due to the brief existence of the twist. the many filaments comprising the yarn are more closely bundled together than they would be otherwise, and the yarn is prevented from being spread out as a wide ribbon on the snubber roller 00. As previously stated, due to the high tension imparted in the'thread, it is appreciably flattened as a ribbon on the wheel 32, but the filaments are still all sumciently united that, when substantial stretching of the yarn takes place, each filament more uniformly assumes its share of the load.

The arrangement shown in Figures 2, 3 and 5 illustrates one wrap around the snubber roller, which is entirely satisfactory when the tension differential between the oncoming yarn and the yarn leaving is not too great. when this differential is large, then the yarn should be given two or more passes around the feed wheel and snubber roller.

If two passes of the yarn are to be made about the snubber guide roller, snubber guide rollers of the type shown in Figures 6 and 7 may be used, and the twist will be imparted to the yarn in its two successive passes therearound.

Referring now toFlgure 6, the reference numeral 00 designates a one-piece snubber roller which can be used when the yarn is given two passes about it. This snubber roller 00 is provided with two thread-contacting portions 02 and 04 having the same diameter and two flanges 00. and 00 of the same angularity. This snubber roller 80 is positioned in the same askew position as the snubber roller 00, and the'yarn 00 is directed first onto the flange 00, from which it is rolled onto the thread-contacting surface 02 to ,impart the temporary twist. In its second pass,

the yarn 30 is fed onto-the flange 00 and is rolled onto the thread-contacting surface ,84 whereby the temporary twist is imparted to the thread. When snubber roller 00 is used, any filament wraps which occur between the flanges l0 and 00 can be removed only with some difficulty.

The modified snubber roller designed to take two passes of the yarn therearound and to satisthereto, shown in Figure '7, comprises two elements 00 and 02 which are independently and freely rotatable on a stub shaft 0|, one end of which is fixedly mounted in a shroud 00. The rotatable elements 00 and 02 are held on the shaft by means of a press-fit washer 00. The element 00 has a substantially cylindrical body I02 and an inclined flange I04 at' the rear thereoi. The element 02 also has a substantially cylindrical body I00 and an inclined flange I00 which terminates in a small cylindrical flange III. The rotatable element 02 is smaller than the element 00 and it is so mounted that the substantially cylindrical body I02 of the element 00 overlaps and is spaced from the flange IIO of the element 02. As is shown in Figure 'I, the

, element 02 is provided on the rear end thereof with a boss III which is positioned in a recess Ill and on the front face of the element 00. While the-liquid discharged from the element 02 generally flows over the rounded shoulder of the element 00, due to the action of centrifugal force a certain amount may .be discharged into the recess I It, in which case it is conducted by means of ducts IIO to a passage I I0, from which it is removed by the conduits I20. The liquid from the element 00 is discharged in the passage III. In operation, this snubber roller is positioned in the same askew manner beneath the feed wheel 02 as the snubber roller 04, and as diagrammatically shown in Figure 8.

In operation, the yarn 00, as it comes from the feed wheel, is led onto the flange I04, from which it rolls onto the thread-contacting cylindrical surface I02 and whereby the temporary twist is imparted to the yarn. In its second passage, the yarn 00 is led onto the flange I00, from which it rolls onto the thread-contacting cylindrical surface I00 whereby the temporary twist is imparted. By having both elements 00 and 02 independently rotatable, each of them seeks its own speed of rotation when driven by the yarn passing therearound. In this way, any chance of frictional rubbing of the yarn on the surface is avoided because only one path of the yarn is in contact with each independent rotatable element of the guide. The slope of the flanges I04 and I00 is preferably about 40 to 50 with respect to the axis of rotation.

If more than two passes of yarn around the feed wheel are desired, the snubber roller hereinbefore described may be substituted by snubber rollers having three or more independently rotatable elements of. the type shown in Figure 7, or, when a single roller is used, three or more flanges and thread-contacting surfaces of the type shown in Figure 6.

The snubber roller 30 may be of any of the types herein described, depending of course on the number of passes the yarn makes therearound. Because. of the high tension on the oncoming side and the relatively low tension on the yarn leaving the second feed wheel 00, it is preferred and more generally needed to use snubber rollers of the type shown in Figures 6 and '7 wherein a double pass of the yarn about the snubber roller is obtained.

The feed wheelsand the snubber guides herein described are constructed of such surface material that sulfur 'and sludge from .the spinning bath will not adhere in the yarn path, forming ridges from which the hot liquid will be discharged without flowing to the flange. A glass surface has given satisfactory results.

Instead of collecting the yarn in, a bucket, it can be'collected on a bobbin.

To fiuther illustrate this invention, the following specific example, wherein proportions are by weight, is given:

Example A viscose solution containing 7% cellulose, 63%

NaOH ripened to.a sodium chloride salt index stretch applies additional tension, so that be-;

tween the two feed wheels the tension is equal to 1060 grams. The yarn is collected in a centrifugal spinning bucket under an average tension of about 15 grams (measured between the second feed wheel and the bucket funnel), and in view of this great tension differential three passes of yarn are made over the second feed wheel, necessitating a double pass of yarn under the snubber roller guide, although but a single pass is needed under the snubber roller guide associated with the first of the stretching feed wheels since the tension differential here is relatively small.

During .5 hours of spinning, using the double roller guide shown in Figure 7 under the second feed wheel and so positioned that a temporary twist was produced in the yarn with each pass thereto, not a-single wrap was formed and the yarn produced was oi uniform high quality with the desired high tenacity. However, when this. double roller snubber guide was replaced with a one-piece cylindrical roller under which the yarn passed without the benefit of temporary twist being applied thereto, eight wraps were formed during a hour period. of which two wraps built up so large by entanglement of other filaments that the yarn was broken.

This invention enables the production of yarn of substantially uniform physical properties having a desirably high elongationas well as high tenacity, good knot strength, and excellent fatigue value. Such yarn is eminently suited for the manufacture of cord for use in the reinforcement of rubber structures, such as rubber tires, steam hose'and the like, and is also useful in many other fields where high strength and reasonable good elongation are desired. This invention permits the production of yarns of higher average dry tenacities than have been possible heretofore by the hot bath spinning method and greatly reduces spinning difficulties.

The invention is not restricted to stretching, between two spaced positively driven feed wheels, viscose yarn impregnated with a hot aqueous liquid. The invention, and particularly the set up of feed wheel 32 and snubber roller 34 hereinbefore described, can be employed in any apparatus or process wherein a yarn is passed one or more times around a feed wheel to avoid sli viously described, whereby,

agulates and regenerates the viscose and, if desired, the yarn can bestretched during its passage therethrough as hereinbefore described, and the feed wheel 32 draws the freshly produced yarn therefrom. slippage of the yarn on the eed wheel I2 is avoided by means of the snubber roller 34, under which the yarn passes between each successive pass about the feed wheel 32. The snubber roller 84 is of the construction, and mounted relative to the feed wheel 32 as prein the passage of the yarn from the feed wheelto the snubber roller, the yarn will be twisted and the twist will leave the yarn after the yarn leaves the snubber roller in its travel back to the feed wheel. The yarn, upon leaving the feed wheel, funnel 48 into the bucket II where is it collected in the form of a cake.

In the embodiment described immediately pre- 1 ceding, the snubber roller can be of arv of the types previously described, depending 'on the number of passes the yarn makes therearound, such roller being positioned, as hereinbefore described, so that the twist will be imparted to the yarn in each of its successive passes thereto.

The method of applying the jet of hot aqueous liquid on the first feed wheel per se forms no part of this invention (except in the combination disclosed herein) and forms the subject-matter of application Serial No. 499,162. v

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited thereto except as set forth in the appended claims.

I claim:

1; In the process of drawing freshly spun yarn around afeed wheel and avoiding slippage of the yarn thereon, the steps which comprise passing the yarn from said feed wheel under a freely rotatable snubber roller to prevent the yarn from tracking on itself, and imparting a twist to said yarn in its passage to said snubber roller.

2. In the process of drawing freshly spun yarn around a feed wheel and avoiding slippage of the yarn thereon, the steps which comprise passing the yarn from said feed wheel under a freely rotatable snubber roller to prevent the yarn from tracking on itself, imparting a twist to said yarn in its passage to said snubber roller, and permitting the twist to leave after the yarn passes from said snubber roller in its travel back to said feed wheel.

3. In the process of drawing freshly spun yarn around a feed wheel and avoiding slippage of the yarn thereon, the steps which comprise passing the yarn from said feed wheel under a freely rotatable snubber roller to prevent the yarn from tracking on itself, and imparting a twist to said yarn betweenthe point it leaves said feed wheel page thereon and a snubber roller is employed to prevent the yarn from tracking on itself. Thus, for example, the feed wheel 32 and the freely rotatable snubber roller 34 arranged as hereinbefore described can be positioned between the and the point it contacts said snubber roller.

' 4. In the process of drawing freshly spun yarn around a feed wheel and avoiding slippage of the yarn thereon; the steps which comprise passing the yarn from said feed wheel under a freely rotatable snubber roller to prevent the yarn from tracking on itself, imparting a twist to said yarn between the point it leaves said feed wheel and the point it contacts said snubber roller, and per-, mitting the twist to leave after the yarn passes from said snubber roller in its travel back to said feed wheel.

5. In the process of drawing freshly spun yarn around, a feed. wheel and avoiding slippage of the is directed by the yarn thereon,

the yarn a plurality -a,44o,saa 1 I 12 roller. permitting the twist to leave the yarn after the yarn passes from said snubber roller in its travel back to said feed wheel, and conducting...

the yarn after it finally passes from said feed feed wheel to said snubber spaced positively driven feed wheels viscose yarn impregnated with a hot aqueous liquid, the steps which comprise passing theyarn from one of said feed wheels under a freely rotatable snubber roller to prevent the yarn from tracking on itself, and imparting a twist to said yarn in its passage to said snubber roller.

7. In the process of stretching between two spaced positively driven feed wheels viscose yarn impregnated with a hot aqueous liquid, the steps which comprise passing the yarn from at least one of said feed wheels under a freely rotatable snubber roller on itself, imparting a twist to said yarn in its passage to said snubber roller, and permitting the twist to leave after the yarn passes from said snubber roller in its travel back to said feed wheel.

8-. In the process of stretching between two spaced positively driven feed wheels viscose yarn impregnated with a hot aqueous liquid, the steps which comprise passing the yarn from at least one of said feed wheels under a freely rotatable snubber roller to prevent the yarn from tracking on itself, and imparting a twist to said yarn between the point it leaves said feed wheel and the point it contacts said snubber roller.

9. In the process of stretching between two spaced positively driven feed wheels viscose yam impregnated with a hot aqueous liquid, the steps which comprise passing the yarn from at least one of said feed wheels under a freely rotatable snubber roller to prevent the yarn from tracking on itself, imparting a twist to said yarn between the point it leaves said feed wheel and the point it contacts said snubber roller, and permitting the twist to leave after the yarn leaves said snubber roller in its travel back to said feed wheel.

10. In the process of stretching between two positively driven feed wheels yam impregnated with a hot liquid, the steps which comprise passing the yarn a plurality of times about one of said feed wheels, passing the yarn a plurality of times about a freely rotatable snubber roller in its successive passages about said feed wheel, im-. parting a twist to said yarn in each successive passage from said feed wheel to said snubber roller, and permitting the twist to leave after the yarn leaves said snubber roller in its travel back to said feed wheel.

11. A method of producing high tenacity viscose rayon yarn which comprises extruding a viscose solution into a spinning bath, withdrawing the yarn from said bath, passing the yarn around a positively driven feed wheel, applying a jet of hot aqueous liquid to the yarn on said feed wheel and while it is within a. zone of 90 from the point it leaves said wheel, the temperature of said aqueous liquid'being such as to heat the yarn to a temperature of at least 75 0., passing the yarn around a freely rotatable snubber roller in its passage around said feed wheel to prevent said yarn from tracking on itself, imparting a to prevent the yarn from tracking wheel to a second feed wheel having a peripheral speed higher than that of the first feed wheel,

12. A method of producing high tenacity viscose rayon yarn which comprises extruding a viscose solution into a spinning bath, withdrawin the yarn from said bath, passing the yarn around a positively driven feed wheel, applying a jet of aqueous liquid heated to a temperature of from- 90' C, to 95 C. to the yarn on said feed wheel and while it is within a zone of 90 from the point it leaves said wheel, passing the yarn around'a freely rotatable snubber roller in its passage around said feed wheel to prevent said yarn from tracking on itself, imparting a twist to said yarn in its passage to said snubber roller, permitting the twist to leave the yarn after the yarn passes from said snubber roller in its travel back to said feed wheel, and conducting the yarn after it finally passes from said feed wheel to a second feed wheel having a Peripheral speed higher than that of the first feed wheel.

13. A method of producing high tenacity viscose rayon yarn which comprises extruding a viscose solution into a spinning bath, withdrawing the yarn from said bath, passing the yarn around a positively driven 'feed wheel. applying a jet of hot aqueous liquid to the yarn on said feed wheel and while it is within a zone of 90 from the point it leaves said wheel, the temperature of said aqueous liquid being such as to heat the yarn to a temperature of at least 0., passing the yarn around a freely rotatable snubber roller in its passage around said feed wheel to prevent said yarn from tracking on itself, imparting a twist to said yarn between the point it leaves said feed wheel and the point it first contacts said snubber roller. permitting the twist to leave the yarn after the yarn passes from said snubber roller in its travel back to said feed wheel, and conducting the yarn after it finally passes from said feed wheel to a second feed wheel having a peripheral speed higher than that of the first feed wheel.

14. A method of producing high tenacity viscose rayon yarn which comprises extruding a viscose solution into a spinning bath. withdrawing the yarn from said bath, passing the yarn around a positively driven feed wheel, applying a jet of hot aqueous liquid to the yarn on said feed wheel, and .while it is within a zone of from the point it leaves said wheel, the temperature of said aqueous liquid being such as to heat the yarn to a temperature of at least 75 (3., passing the yarn around a freely rotatable snubber roller in its passage around said feed wheel to prevent said yarn from tracking on itself, imparting a twist to said yarn in its passage to said snubber roller, permitting the twist to leave the yarn after the yarn passes from said snubber roller in its travel back to said feed wheel, conducting the yarn after it finally passes from said feed wheel to a second feed wheel having a peripheral speed higher than that of the first feed wheel, passing the yarn a plurality of times about said second feed wheel, passing the yarn a plurality of times about a freely rotatable snubber I twist to said yarn in its passage to said snubber 75 roller, and permitting the twist to leave after the yarn leaves the snubber roller in itstravel back to said second feed wheel.

15. A method as set forth in claim 14, wherein the temperatures of the hot aqueous bath is from 90 C. to 95 C. Y

16. In combination a feed wheel over and about which yarn is passed and a freely rotatable snubber roller to displace the yarn passing about said feed wheel, said snubber roller having a plurality of inclined flanges and a body portion in advance of each flange, the front edge of the body portion last engaged by the yarn being free, said snubber roller being mounted askew to said feed wheel whereby in the successive passages of the yarn from said feed wheel to said snubber roller it will pass successively onto the respective flanges and roll therefrom to the body portion forwardly thereof to impart a twist in said yarn.

17. In combination a feed wheel over and about which yarn is passed and a freely rotatable snubber roller to displace the yarn passing about said feed wheel, said snubber roller having a plurality of flanges inclined at the same angularity with' respect to the axis of rotation of said snubber roller and a body portion in, advance ofreach flange, the front edge of the body portion'last engaged by the yarn being free, said snubber roller being mounted askew to said feed wheel whereby in the successive passages of the yarn from said feed wheel to said snubber roller it will pass onto the respective flange and roll therefrom to the body portion forwardly thereof to impart a twist in said yarn.

18. The combination as set forth in claim 16 wherein the snubber roller is formed of one piece.

19. The combination as set forth in claim 17 wherein the snubber roller is formed of one piece and has two flanges and two body portions.

20. The combination as set forth in claim 16 wherein the snubber roller is formed of one piece and the body portions in advance of each flange being of substantially the same diameter.

21. The combination as set forth in claim 17 wherein the snubber roller is formed of one piece and has two flanges and two body portions, said body portions being of substantially the same diameter.

HOWARD W. SWANK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number