US3516240A

US3516240A - Method of false-twisting plural ends of thermoplastic yarn

Info

Publication number: US3516240A
Application number: US769219A
Authority: US
Inventors: Bobby Ray Fain
Original assignee: Alamance Industries Inc
Current assignee: Alamance Industries Inc
Priority date: 1968-10-21
Filing date: 1968-10-21
Publication date: 1970-06-23
Anticipated expiration: 1987-06-23

Description

June 23, 1910 B. R. FAIN 3,516,240

METHOD OF FALSE-TWISTING PLURAL ENDS OF THERMOPLASTIC YARN Filed Oct 21, 1968 2 Shets-Sheet'l ATTORNEYS B. R. FAIN June 23, 1970 METHOD OF FALSE-TWISTING PLURAL ENDS OF THERMOPLASTIC YARN Filed Oct. 21, 1968 2 Sheets-Sheet 2 INVENTOR. BOBBY RAY FA) N BYW 524 dig, 1! film,

ATTORNEY:

United States Patent 3,516,240 METHOD OF FALSE-TWISTING PLURAL ENDS 0F THERMOPLASTIC YARN Bobby Ray Fain, Burlington, N.C., assignor to Alamance Industries, Inc., Burlington, N.C., a corporation of North Carolina Filed Oct. 21, 1968, Ser. No. 769,219 Int. Cl. D02g 1/02 U.S. Cl. 57-157 10 Claims ABSTRACT OF THE DISCLOSURE Plural ends of thermoplastic yarn are joined together and first false-twisted in one direction while being heatset, then subsequently false-twisted in the opposite direction with the same number of turns but without heatsetting, and then the yarns are separated and taken up on separate bobbins. Torsional stresses are imparted to the yarn by this process so that periodically reversing small closely spaced substantially uniform spring-like coils are formed along the length of the yarn.

This invention relates generally to a method of simultaneously false-twisting plural ends of thermoplastic yarn to impart enhanced torsional stresses to the yarns.

It is known to produce reversing torsional stresses in thermoplastic yarn by passing the yarn over a heated blade in what is known as an edge-crimping process. It is also known to produce reversing torsional stresses in thermoplastic yarn by simultaneously false-twisting a pair of yarns in one direction while heat-setting the twisted together yarns and then oppositely false-twisting the paired yarns in a second operation while applying a lesser number of turns and a reduced heat-setting temperature to the yarns. The yarns produced by either of these methods are characterized by periodically reversing small closely spaced substantially uniform springlike coils along the length thereof. When these yarns are knit to form fine gauge fabric, such as ladies hosiery, the stitch loop interconnected prevents full development of the coils in the yarn but a sufficient distortion of the yarn is obtained to provide stretch and a creped appearance to the fabric.

In each of these procedures the production cost is relatively high because, in the edge-crimping process, it is difficult to maintain the blade in properly sharpened condition for long periods of time. In the other process,

two separate false-twisting operations must be employed.

Hosiery knit of yarns processed by the edge-crimping" method have sufficient stretch to cling to the leg but are slow to recover after having been stretched to near their stretch limit, as when the fabric in the knee area is stretched when the leg is bent.

With the foregoing in mind, it is an object of the present invention to provide a method of false-twisting plural ends of thermoplastic yarn which may be carried out in a continuous and economical manner, and which method produces suflicient torsional stress to the yarn that improved stretch recovery is imparted to fine gauge fabrics, knit of the yarn, such as ladies sheer hosiery.

According to a preferred embodiment of the present invention, the joined together yarns are looped about the exit pin of a false-twist spindle in such a manner that the yarns rub across themselves while being first falsetwisted in one direction. In this first false-twist operation, the twisted together yarns are heat-set in advance of the false-twist spindle. The joined yarns are subsequently false-twisted in the opposite direction with the same number of turns but without heat-setting, and the yarns are wrapped about the exit pin with a single 360 degree wrap during the second false-twisting operation. The process is carried out in a continuous manner and requires only minor modifications of a conventional type false-twist machine.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in which- FIG. 1 is a somewhat schematic isometric view of a small section of a preferred type of false-twist apparatus for carrying out the method of the present invention;

FIG. 2 is a greatly enlarged fragmentary view of the upper end portion of the first false-twist spindle and illustrating the manner in which the joined together yarns are initially threaded or looped around the exit pin;

FIG. 3 is a view similar to FIG. 2 illustrating the direction in which the looped yarn runs across and over itself at the exit pin when the first false-twist spindle is rotated in a counterclockwise direction;

FIG. 3A is a View similar to FIG. 3 but illustrating the yarns being looped in the opposite direction when the first false-twist spindle is rotated in a clockwise direction;

FIG. 4 is a view similar to FIG. 3, but illustrating the manner in which the joined together yarns are wrapped about the exit pin of the second false-twist spindle;

FIG. 5 is a greatly enlarged fragmentary view of one of the false-twisted yarns in partially relaxed condition, illustrating the flattened appearance of the yarn and the formation of the periodically reversing coils therein;

FIG. 6 is an elevational view of a boarded seamless stocking wherein the leg and foot portions are knit of yarn processed in accordance with the method of the present invention; and

FIG. 7 is a greatly enlarged fragmentary portion of the knit fabric in relaxed condition, being taken in substantially that area of the leg of the stocking enclosed by the dotted square 7 in FIG. 6, and illustrating the irregular distortion of the yarn in the stitch loops to provide stretch and a creped appearance to the fabric.

The present invention is particularly concerned with a method of false-twisting plural ends of thermoplastic yarns which fall within the range of those yarns normally used in knitting ladies sheer hosiery and the like, for example, within the range of about 7 to 70 denier. The yarn may be a monofilament yarn, such as for example denier, and multifilament yarns falling within the preferred range may also be utilized. For example, 15 denier yarn consisting of 3 filaments and 14 denier yarn consisting of 2 filaments may also be utilized in this process.

Referring to the drawings, FIG. 1 schematically illustrates one station of the preferred type of apparatus used to false-twist the yarn in accordance with the present method. The false-twist machine illustrated is of the type known as the Model 553 false-twist machine, manufactured by Leesona Corporation, and only slight modification of this machine is required to adapt it to the present method. A pair of yarns Y and Y are withdrawn from respective yarn supply :pirns and 21 which are suitably supported on the lower portion of the machine. The yarns Y and Y are preferably in the raw condi tion received from the yarn producer and may be supplied with a special finish to provide proper lubrication.

The yarns Y and Y are drawn upwardly through respective guide wire loops 22, 23 which are supported on a rod 24 and the yarns are joined together as they pass through a sinuous wire guide 25 which is attached to the leading flange of a support plate 26. The joined yarns pass on opposite sides of tension disc support posts 27 and then through a yarn guide 28. The joined together yarns pass downwardly and beneath a guide wire which is fixed on a support rod 31. The yarns are then wound around a driven lower feed roll 32 and a separator roll 33. As the yarns leave the lower feed roll 32, they are engaged by a small nip roll 32a to limit the downward passage of twist. The yarns then pass upwardly through a yarn receiving groove in a heater block 34, through a pigtail yarn guide 35, and into a false-twist spindle 36 which is rotated by a drive belt 37.

As shown in FIGS. 2 and 3, the upper end of the false-twist spindle 36 is provided with a small exit pin 38 which is tapered inwardly toward the center from each end and which is formed of a hard ceramic material, such as Al Si Mag. The diameter at the central portion of the pin 38 is preferably small, on the order of .030 of an inch. The joined together yarns Y, Y are threaded around the exit pin 38 of the false-twist spindle 36 in a special manner, as shown in FIGS. 2, 3 and 3A, depending upon the direction of rotation of the false-twist spindle 36. The special threading of the yarns about the exit pin 38 will be presently described.

The joined yarns Y and Y are then directed upwardly from the exit pin 38 and wound around a driven upper feed roll 40 and separator roll 41, then Wrapped with one and one-half turns around a guide roller 42, downwardly beneath a guide roller 43 and then beneath a guide wire 44. From the guide wire 44, the yarns are threaded up through a second false-twist spindle 45 and wrapped about an exit pin 46 in the usual manner with a single 360 degree wrap, as shown in FIG. 4. The second false-twist spindle 45 is rotated in an opposite direction from the false-twist spindle 36 or in a clockwise direction. This opposite rotation of the second false-twist spindle 45 tends to reduce this torque imparted to the yarns by the first false-twist spindle 36.

From the false-twist spindle exit pin 46, the yarns pass upwardly and are wound about a driven upper feed roll 50 and a separator roll 51, pass upwardly over a guide roller 52 where the two ends of yarn Y and Y are separated and taken up on separate take-up packages. The yarn Y is led through a traversing yarn guide 53 and is wound onto a take-up tube 54 to form a package 55. The take-up tube 54 is rotated by means of a cork drive roll 56 which rotates against the surface of the yarn package 55. The yarn Y' is led through a traversing yarn guide 60 and is wound onto a take-up tube 61 to form a package 62. The take-up tube 61 is rotated by means of a cork drive roll 63 which rotates against the surface of the yarn package 62 and at the same speed as the upper cork drive roll 56.

The speed of the lower feed roll 32 and the upper feed rolls 40, 50 is the same to maintain tension on the joined yarns as they pass through the heater 34 and through the first and second false-twist spindles 36, 45. The rotational speed of the upper feed rolls 40, 50 is adjusted relative to the speed of the cork drive rolls 56, 63 so that the individual yarns Y and Y are wound onto the respective take-up packages 55, 62 with a 2% overfeed.

Thus, as illustrated in FIG. 1, the yarns Y and Y are Just false-twisted in one direction by the false-twist spindle 36 and the twisted yarns are heat-set as they move through the heater block 34. The yarns are then false-twisted in the opposite direction by the spindle 45 without any heat being applied to the yarns between the upper feed roll 40 and take-up packages 55, 62. The false-

twist spindles

36, 45 are rotated at the same speed because they are both driven by the same drive belt 37, but are positioned on opposite sides thereof so that they rotate in opposite directions.

The only modification which must be made to the false-twist machine in order to carry out the present process involves the addition of suitable guides to feed the two yarns from seperate pirns until they are joined together at the guide wire 25, the addition of the

guide rollers

42, 43, 52 and the guide wire 44. The yarns are directed through the second false-twist spindle 45 so that they do not pass through the heater block at the next station, which is not shown but is positioned directly beneath the false-twist spindle 45. The lower feed rolls which are positioned beneath this adjacent heater block are not utilized in practicing the method of the present invention. However, the production of the machine is not reduced by use of the present method because two yarns are processed together at this single station.

The special manner in which the joined yarns Y and Y' are threaded or wrapped about the exit pin 38 of the false-twist'spindle 36 is illustrated in FIGS. 2, 3 and 3A. In threading up the machine to begin the operation, the yarns are drawn upwardly through the hollow false-twist spindle 36 by means of the usual threading wire, not shown, and behind the exit pin 38. A loop L is then formed (FIG. 2) and the free end portions of the joined yarns Y and Y are then passed through the loop in a direction which is determined by the rotational direction of the spindle 36. The spindle shown in FIG. 2 is to be rotated in a counterclockwise direction so the yarn is drawn through the loop from left to right. When the spindle is to be rotated in the opposite direction, the yarn is drawn through the loop in the opposite direction; i.e., from right to left, as shown in FIG. 3A.

The yarns are then drawn upwardly and wrapped around the upper feed roll 40 and the separator roll 41 so that the loop L is closed, as illustrated in FIG. 3. The false-twist spindle 36 is shown in FIG. 3 as being rotated in a counterclockwise direction, looking downwardly thereon, and torque is imparted to the yarns in a Z direction. The second false-twisting of the yarns in the opposite direction removes a substantial portion of this torque so that the final yarn has only a slight amount of torque. However, the final yarn has sufiicient torque that it is preferable that yarns of opposite torque be knit in alternation to balance the overall torque in the fabric. Thus, Z torque yarns are formed by threading them about the exit pin of a counterclockwise rotating spindle in the manner illustrated in FIGS. 2 and 3. Yarns having S torque are formed by threading them about the exit pin of a clockwise rotating spindle in the manner illustrated in FIG. 3A.

'In either case, the joined together running yarns pass upwardly on one side of the exit pin and then downwardly on the same side of the exit pin to form a loop in the yarn. These joined together yarns then pass beneath the exit pin and upwardly on the opposite side and through the loop as they leave the exit pin. Thus, the yarns rub across themselves at the bite of the loop. The rubbing action of the yarns across themselves at the exit pin 38 of the false-twist spindle 36 contributes to and aids in imparting latent torsional stresses to the yarn. This rubbing action combined with the heat-setting of the twisted together yarns below the false-twist spindle provides both torque and latent torsional stresses to the yarns so that they curl or coil in a periodically reversing direction, as illustrated in FIG. 5.

The processing of the yarn, in accordance with the present invention, results in a flattening of the yarn to form it into a ribbon-like configuration or cross-section, and this flattening is believed to result from the manner in which the yarns are tightly twisted together below the false-twist spindle 36 and while in a heated condition. Some of the flattening of'the yarns may also be attributed to the rubbing action of the yarns at the special loop formed around the false-twist spindle exit pin 37. If the yarn of FIG. 5 were completely relaxed, it would twist upon itself and form pigtails along the length thereof. However, the yarn is maintained under a sufficient tension during the process so that it is wound onto the takeup packages 55, 62 in a substantially straight condition.

Before knitting, the yarn is preferably rewound from the take-up packages 55, 62 and wound onto suitable knitting tubes while it is maintained under a tension, from about 2 to .5 grams, so that any kinks in the yarn are removed and the yarn is wound in a straight condition. A suitable lubricant is preferably added to the yarn as it is rewound onto the knitting tube. During the knitting operation, the yarns are also maintained under a sufiicient tension that they cannot relax and form curls or coils therein.

In knitting a ladies sheer seamless stocking, such as is shown at S in FIG. 6, a fine gauge yarn processed in accordance with the present invention is preferably knit in the leg and foot portion 70, 71 while the welt 72, shadow welt 73, heel pocket 74, and toe pocket 75 are preferably knit of a heavier denier yarn. The leg and foot portions 70, 71 are preferably knit with yarns which have been processed in opposite directions so that the torque of the yarn in alternate courses is in reverse directions. Thus, the stitch loops in the odd numbered courses C-1, C3 and (1-5 of FIG. 7 have a tendency to incline to the right because they are knit of yarn having torque in one direction while the sitch loops in the even numbered courses C-2, (3-4 and C6 have a tendency to incline to the left because they are knit of yarn having torque in an opposite direction. Thus, the overall torque in the stocking is balanced and there is no objectionable twisting of the stockings.

The stockings may be finished in the conventional manner, such as by dyeing and boarding. During the finishing of the stockings, the yarn in the stitch loops tends to curl and coil, thereby distorting the yarn in the manner illustrated in FIG. 7. This distortion of the yarn and stitch loops imparts a substantial amount of stretchability to the fabric and after it is released, the fabric quickly returns to the relaxed condition because the yarns have a strong tendency to return to the crimped and curled condition. This elastic characteristic provides the stocking with a high degree of snap-back that is highly desirable as it reduces the problem of baggy knees; particularly in panty hose and the like where the upper portion of the garment is supported in a substantially fixed position around the waist of the wearer.

As an illustrative, but non-limiting example, very satisfactory hosiery has been produced in accordance with yarn processed in accordance with the following specific example. Single ends of denier monofilarnent nylon are extruded with a round cross-section and have a lubricating finish applied thereto of the type known as a type 1296-smooth, manufactured by Nopco Chemical Company. This application of lubricating finish to the yarn as it is extruded provides a low coeflicient of friction on the yarn and a slick finish which aids in running the two yarns together.

The single ends of 15 denier monofilament yarn are withdrawn from the supply bobbins 20, 21 (FIG. 1), joined together and passed upwardly through the falsetwist spindle 36, While the heater block is maintained at a temperature of approximately 315 F., and the false-twist spindle 36 is rotated at a sufiicient speed (about 345,000 r.p.m.) to impart 112 turns per inch of false-twist to the joined together yarns. The yarns are then directed through the second false-twist spindle 45 where a reverse falsetwist is imparted to the yarns, without heat, and the yarns are separated at the guide roller 52 and taken up on separate packages. The yarns between the lower feed roll 32 and the upper feed roll 40 are maintained under constant tension and with zero overfeed, while the yarns between the upper feed roll 50 and the take-up packages 53, 62 are fed with a 2% overfeed so that they are relaxed to a very minor degree.

The yarns are threaded around the false-twist exit pin 38 of the spindle 36 by the special looped or slip-knot configuration of FIGS. 2 and 3, which also provides an eflicient twist trap to prevent passage of the twist from one side of the exit pin to the other. The joined together yarns are threaded around the exit pin 46 of the falsetwist spindle 45 by the usual single wrap, as illustrated in FIG. 4. When the yarns Y and Y are separated and taken up on the packages 55, 62, they each have identical characteristics and are very uniform throughout their length. Other pairs of identical 15 denier monofilament nylon yarns are processed in an identical manner, except that the yarns are threaded about the exit pin 38 of the spindle 36 in the manner indicated in FIG. 3A, and the false-twist spindle 36 is rotated in an opposite direction from that indicated in FIG. 1; i.e., in a clockwise direction.

When false-twisting other than 15 denier monofilarnent nylon, the range of turns of false-twist imparted at the false-twist spindles 36, may be varied from about 80 to 125 turns per inch and the temperature of the heater block may be maintained within the range of about 300" to 400 F., depending upon the speed of travel of the yarn through the heater block and the type of yarn being processed. In the processing of multifilament yarn, it is desirable to apply some prior twist to the individual yarn ends before joining and false-twisting them in accordance with the present invention. This prior twist may vary from about 2 to 12 turns per inch and is preferably about 3 turns per inch for 14/ 2 yarn. This prior twist tends to hold the yarns together and aids in the splitting apart of the yarns after they have been joined together and falsetwisted through both of the false-twisting

spindles

36, 45.

As has been mentioned, the present process is more economical than any known method of imparting a crimpcurl to fine denier yarn, and hosiery knit of this yarn has enhanced stretchability and recoverability with a pleasing appearance and hand. The enhanced elasticity and recoverability of the fabric is particularly desirable in panty hose because it prevents bagginess of the fabric in the knee area when the leg is straightened after having been bent at the knee.

In the drawings and specification there have been set forth preferred embodiments of the invention and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

I claim:

1. A method of processing thermoplastic yarn to produce small closely spaced substantially uniform springlike coils in each of said yarns, the rotational direction of said coils periodically reversing along the length of the yarn and providing a stretchable yarn suitable for knitting of hosiery and the like, said method comprising the continuous steps of (a) joining together a pair of thermoplastic yarns,

(b) false-twisting the joined together yarns in one direction while heat-setting the twisted together yarns,

(c) subsequently false-twisting the yarns a second time with a false-twist in the opposite direction and applying the same number of turns, but without applying any heat to the yarn during the second false-twisting operation,

((1) separating the two yarns, and

(e) taking up the separated yarns on separate bobbins.

2. A method according to claim 1 wherein each yarn end is within the range of about 7 to denier.

3. A method according to claim 1 wherein the joined yarns are false-twisted in steps (b) and (c) within the range of about to turns per inch.

4. A method according to claim 1 wherein each yarn end is 15 denier monofilament and the joined yarns are false-twisted in steps (b) and (c) with about 112 turns per inch.

5. A method of processing thermoplastic yarn on a false-twist machine including first and second spaced apart false-twist spindles, each spindle including an axial bore through which the yarn is adapted to pass, an exit pin supported at one end of said spindle and having a yarn engaging central portion extending over the axial bore of said spindle, means for imparting rotation to said first and second spindles in opposite directions, and a heating zone positioned in advance of said first false-twist spindle and through which the yarn passes prior to moving through said first spindle, said method comprising the steps of (a) withdrawing a pair of yarns from corresponding supply sources and guiding the same in joined together relationship through said heating zone and said first false-twist spindle,

(b) threading the yarns about said exit pin of said first false-twist spindle by passing the joined totogether yarns upwardly on one side of said exit pin and downwardly on the same side of said exit pin to form a looped portion in the yarn, passing the yarn down around and beneath said exit pin and upwardly on the opposite side of the exit pin and through the looped portion whereby the yarns cross themselves at the bight of the looped portion,

(c) threading the joined yarns through said second false-twist spindle and about the exit pin by Wrapping the yarns thereabout,

(d) separating the joined together yarns,

(e) threading the separated yarns onto corresponding take-up packages, and

(f) continuously withdrawing the yarns from the supply packages and winding them onto the corresponding take-up packages while false-twisting the joined together yarns in one direction at said first false-twist spindle and heat-setting the yarns, and subsequently false-twisting the yarns in the opposite direction at said second false-twist spindle without applying any heat to the yarn, the false-twisting and heat-setting of the paired yarns and the rubbing of the yarns across themselves at said first false-twist spindle im parting torque and latent torsional stresses thereto.

6. A method according to claim 5 wherein each end of yarn is within the range of about 7 to denier.

7. A method according to claim 5 wherein the joined yarns are false-twisted at both the first and second spindles within the range of about to turns per inch.

8. A method according to claim 5 including the step of rewinding the yarn from the take-up packages and onto knitting pirns while maintaining the yarn under a tension of from about 2 to 5 grams to prevent kinking of the yarn.

9. A method according to claim 8 including the step of applying a lubricant to the yarn as it is being rewound from the take-up package to the knitting pirn.

10. A method according to claim 5 wherein the heating zone includes a heater block maintained at about 315 F., each yarn is 15 denier monofilament, and the joined yarns are false-twisted at both the first and second spindles with about 112 turns per inch.

References Cited UNITED STATES PATENTS 2,952,116 9/1960 Burleson 57-157 3,041,814 7/1962 Held 5734 3,423,924 1/1969 Comer et al. 57157 FOREIGN PATENTS 1,074,322 3/1954 France.

1,091,308 10/1954 France.

JOHN PETRAKES, Primary Examiner US. Cl. X.R. 5734