US3678676A - Heat setting trapped pre-inserted twist - Google Patents

Abstract

Continuous thermoplastic yarns having ribbon-like cross sections are textured in a continuous operation, wherein drawing thereof may also occur, by trapping twist possessed by said yarns in a heat-setting zone through the use of slotted guide elements or pins which may be opposed in close proximity or the yarn may be wrapped around a single stationary pin to prevent the twist escaping from the heat-setting zone. A predetermined amount of twist may be inserted prior to start-up of the process by preinserting the desired number of turns per inch or allowed to build up to the desired level as a result of the twist in yarn unwinding from a supply package.

Description

United States Patent Rothwell et al.

[ 51 July 25,1972

[54] HEAT SETTING TRAPPED PRE- INSERTED TWIST [72] Inventors: Ronald E. Rothwell, Colonial Heights; Charles W. Berlnger, Richmond, both of [21] Appl. No.: 828,180

US. Cl ..57/157 TS, 57/34 HS, 57/77.3

3,069,837 12/1962 Olson ..57/l57 3,153,891 10/1964 Kissler 3,196,602 7/ 1965 Jenkins et a1. 3,261,116 7/1966 Kunzle et a1... 3,445,996 5/1969 Berger, Jr. ..57/34 Primary Examiner-John Petrakes Attorney-Roy H. Massengil and Luther A. Marsh [57] ABSTRACT Continuous thermoplastic yarns having ribbon-like cross sections are textured in a continuous operation, wherein drawing thereof may also occur, by trapping twist possessed by said yarns in a heat-setting zone through the use of slotted guide elements or pins which may be opposed in close proximity or the yarn may be wrapped around a single stationary pin to prevent the twist escaping from the heat-setting zone. A predetermined amount of twist may be inserted prior to startup of the process by pre-inserting the desired number of turns per inch or allowed to build up to the desired level as a result of the twist in yarn unwinding from a supply package.

5 Claims, 6 Drawing Figures Patented July 25, 1972 2 Sheets-Sheet 1 I NVEN TOR. Rona/d fifi'o/hwe BY Char/es W'Bermger a 7v- 7 WW ATTORNEY Patented July 25, 1972 3,678,676

2 Sheets-Sheet Z llilll gj wz Char/es W Ber/lager BY @W M ATTORNEY HEAT SETTING TRAPPED PRE-INSERTED TWIST BACKGROUND OF THE INVENTION This invention relates to the production of torque-type yarns in a rapid continuous operation. Preferably, an undrawn thermoplastic monofilament or multifilament yarn is drawn and heat set while in a twisted condition to impart a twist memory to said yarn in a coupled operation. The source of yarn may be received directly from the quench stack of a spinning position or delivered from a supply package mounted on a creel.

The prior art has long recognized the advantages to be achieved from torque yarns, particularly for ladies wear articles such as hosiery and various foundation garments. An appreciation of the state to which this particular art has advanced may be obtained from a review of U. S. Patents, such as Nos. 2,019,183, where a three step process was required, and 3,435,607, in which a similar result is achieved in a single operation by backing twist up the threadline from the traveler onto a heated surface to accomplish heat setting said twist in the yarn which is drawn several times its original length in the same operation.

During the development of the torque yarn technology, many methods have been employed in attempts to improve the properties of the yarn and to reduce the cost of production. While substantial improvements have been made, problems still exist which impose undesirable limitations. The most serious limitations are imposed by mechanical devices which will not operate safely beyond certain speeds and other speed limiting factors such as friction developed by the interaction of the threadline either upon itself or with contact surfaces. In all of the methods known heretofore the yarn is continuously twisted by a rotating false twist tube or traveler element which backs up the twist, and surface frictional forces.

Therefore, the primary object of the present invention is to provide a method for continuously producing torque yarns having modified cross sections or multifilament yarns temporarily possessing ribbon-like cross sections during processing in a rapid manner free from the objectionable limitations imposed by conventional methods.

SUMMARY OF THE INVENTION In accordance with the present invention a continuous thermoplastic yarn is received in a continuous manner from a supply source. The yarn strand should possess a cross sectional configuration which is essentially flat or the individual filaments should possess cross sections having opposed broad surfaces. These cross sectional configurations may be obtained by profiling the shape thereof during the extrusion step in preparing the yarn or by causing a group of two or more filaments comprising a yarn to temporarily spread apart to form a ribbon-type structure. Preferably, the yarn has not been drawn subsequent to spinning and may be received directly from the spinning station or a supply package. The undrawn yarn is advanced through a drawing or stretching zone to impart molecular orientation thereto prior to entering a heat set zone wherein the yarn possesses a predetermined number of twists per inch while passing through said zone. The twist level is established by inserting the desired amount of turns per inch prior to starting the operation or by allowing the desired amount of twist to build up from the removal of the yarn from a supply package where applicable. The twist is trapped within the heat set zone by restricting rotational movement of the essentially flat configuration of the yarn in a combination of slots and/or opposed pins or other means which maintain the desired twist level within said zone. In operations involving removal of yarn possessing twist from the end of a supply package which causes a build up of twist, the restricting means must be designed to allow excess twist to pass through the heat set zone afler reaching an equilibrium twist level. Also, the yarn may be passed around stationary pins in the path of yarn travel or similar means which do not permit the selected amount of twist to run out of the heat set zone. The major advantage resides in the fact that the yarn does not have to be twisted during a false-twist, heat-set process which imposes the objectionable limitations noted above. Thus, the principal requirements involved in carrying out the present invention include the use of any type of device or elements capable of restricting the rotation of a moving strand, which may be either a monofilament or multifilament yarn, within a predetermined zone, but in both instances the strand must be characterized by oppositely disposed broad surfaces that prevent the twisted portion of the moving strand from rotating while in said zone thereby trapping the twist therein at an equilibrium or predetermined amount of twist level. If the yarn feed introduces twist into the strand when unwinding from a package, the rotation-restricting means must be designed to permit the twist to pass through the twist zone after an equilibrium twist level is attained.

The yarn is heated to an elevated temperature range sufficient to relax or heat set the yarn in its twisted condition to establish a twist memory in the yarn which is permanent unless subsequently heated to a higher temperature. Better results are obtained if the yarn is heated in the heat set zone, but is is posible to heat the yarn to the necessary temperature prior to entering said zone. Preferably, the yarn contacts a surface heater; however, other types of heating sources such as hot air, steam and infrared lamps may be employed which are quite suitable. After leaving the heat set zone at a lower temperature, the yarn is wound onto a pim or bobbin. High speed winders are employed to facilitate take-up in a coupled spinning, drawing and texturing process, but conventional ring and traveler mechanisms are suitable for take-up of the yarn on drawtwisters and similar equipment which operate at relatively slower speeds.

Another aspect of the invention contemplates its adaptability to processes which employ drawn yarn. These processes are normally conducted by throwsters during a rewinding step such as coning, twisting and the like. The conventional equipment presently beingemployed by the fiber processors may be modified slightly to include means for trapping a predetermined amount of twist in a yarn and a source of heat for heat setting a twist memory in the yarn while it is being processed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view in front elevation of a modified drawtwisting machine suitable for producing torque-type thermoplastic yarn in accordance with the present invention.

FIG. 2 is a plan view of a slotted disc assembly employed for restricting rotation of a traveling yarn strand having a cross section characterized by broad surfaces with respect to their thickness and a crank-type device associated with the disc for rotating said disc to impose twist on a yarn strand passing through the slot therein.

FIG. 3 illustrates a bilobal yarn cross section which is highly preferred for processing on the apparatus shown in FIGS. 1 and 2.

FIG. 4 is a fragmentary view in front elevation of another arrangement of apparatus suitable for processing thermoplastic yarn received in a coupled spinning, drawing and false twisting operation in accordance with this invention.

FIG. 5 is a fragmentary view in front elevation of an arrangement of apparatus suitable for processing drawn thermoplastic yarn by heat setting twist-ed yarn being removed from a supply package and passed through a heat set zone prior to takeup.

FIG. 6 illustrates a multifilament yarn strand shaped into a ribbon-like cross section to produce broad surfaces for processing on the apparatus shown in "the preceding Figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings and particularly to FIG. 1 wherein one embodiment of the invention is illustrated on a drawtwisting machine which has been modified to provide means for entrapping twist in a section of a traveling yarn strand, and means for heat setting the yarn strand in a heated condition to impart a twist memory to said yarn. More specifically, there is shown a yarn supply package from which an undrawn yarn strand 12 is unwound and forwarded to guide member 14 which guides several wraps of said yarn strands onto a cot roll 16 before passing downward over the surface of a feed roll 18 that is in surface contact with the cot roll 16. The yarn strand 12 is a bifilament having a figure eight cross section as illustrated in FIG. 3. The feed roll 18 is rotated by means not shown and the cot roll 16 is surface driven by said feed roll. From the feed roll 18 the yarn strand passes for several wraps around a draw roll 20 and idler roll 20A which are rotating at higher speeds than said feed roll to draw the yarn a desired amount. At this point in the process, the yarn is substantially free of twist.

The drawn and untwisted yarn departs the drawing zone and passes through a trapped twist zone and guide 21 prior to takeup on a package 22 by a ring and traveler 24 in a conventional manner. At the exit of the trapped twist zone the yarn strand passes through a restricting means 30, illustrated in FIG. 2, which is comprised of a disc 32 rotatably mounted to a support member 31 and provided with a yarn guide slot 34. The periphery of the disc is provided with gear teeth that intermesh with teeth on a rotatable crank 36 having similar threads to produce a worm and wheel gear. When the yarn strand is laced through the slot 34 a desired number of twists can be inserted into said strand by operating crank element 36. The crank may be operated clockwise or counterclockwise to insert either S or Z twist into the yarn. The size of the slot 34 will be determined from the size and type of cross section possessed by the yarn strand to be processed.

The twist inserted into the yarn strand 12 by operation of crank 36 remains trapped above the slot 32 since the yarn is restricted from rotating within said slot. A plate-type heater 38 is positioned between said restricting means and draw roll 20 in the path of the yarn strand whereby the yarn strand is in surface contact with the heated surface of said plate heater. The heated surface imparts sufficient heat to the yarn in its twisted condition to heat set a memory of said twist in the yarn.

All types of thermoplastic yarns capable of being heat set may be processed in accordance with the present invention which includes the most important commercial products such as polyamides, polyesters, and polyolefins. The temperature of the heater 38 wii] of course depend upon the type composition and size of the yarn strand and the speed of travel.

FIG. 4 illustrates an embodiment of the invention which is capable of processing a yarn strand traveling at several thousand feet per minute. A strand 40 of undrawn filaments is received from a spin position, not shown. The yarn strand passes over guide bar 41 and is drawn to impart orientation of the molecular structure of the yarn between draw roll 42 and draw roll 44 which is rotated a desired multiple of times faster than draw roll 42. After drawing, the yarn strand is passed through a heat set zone and taken up on a package 46 by a conventional high speed winder. Twist is inserted into the yarn strand in the heat set zone and trapped therein by twist trapping means 48 and 50. The twist memory is heat set in the yarn by heat conducted from a plate-type surface heater 52. Preferably, the twist is pre-inserted in the yarn between means 48 and 50 prior to startup of the process. While passing through the twist trapping means 48 and 50 the yarn strand cross section must assume a ribbon-type configuration as shown in FIG. 6 to prevent rolling or rotation of the filaments which would release the twist from the heat set zone.

in FIG. 5 there is illustrated a typical false twisting machine such as disclosed in U. 5. Pat. No. 2,803,105 except the normally rotating false twist spindle has been replaced with a stationary snubbing pin. A multifilarnent yarn strand comprised of drawn filaments is withdrawn from a yarn package 62 and passed through a guide 63 to a heat set zone while in a twisted condition where heat setting of the yarn occurs from heat supplied by plate heater 64 and thereafter wound onto a take-up package 66 by a conventional high speed winder. The twist is previously inserted into the supply yarn and builds up to the desired level by removal of the yarn over the end of the package 62. This buildup of twist is trapped by a stationary pin 68 which spreads the filaments to form a ribbon-like yarn strand and impedes the passage of the twist buildup being transferred from the yarn supply package. When twist builds up to a desired amount an equilibrium level is reached and then the twist being removed from the supply package passes through the twist trapping zone and remains in the yarn strand as wound onto the take-up package.

This invention is further illustrated by a comparison of the relative yarn torque measurements of yarn produced on several embodiments as compared with conventional false twisted yarn.

EXAMPLE 1 This example represents conventional false twist conditions employed on a conventional Leesona 553 false twist machine which was threaded and operated under normal conditions. One wrap of a drawn bifilament yarn prepared from polycaproarnide having a figure eight cross section was placed around the pin of the false-twist spindle which was operated at 195,000 r.p.m. to insert 31 turns per inch in the yarn traveling at yards per minute. The heater was maintained at 187C to heat set the twist in the yarn. The yarn resulting from several trials had relative torque measurements ranging from 45 to 55.

EXAMPLE 2 The machine in the trials of Example I was stopped and the yarn was re-threaded to remove the trapped twist and then restarted under the same conditional conditions except the false-twist spindle or pin was left stationary. Resultant relative yarn torque measurements ranged from 45 to 55 revealing that the yarn had a similar amount of torque properties as the yarns processed under conventional conditions wherein the false-twist spindle was rotated.

It is noted that the primary limitation of false-twist machine delivery speeds is imposed by the spindle speeds necessary to obtain a given twist level. As will be quickly recognized, the delivery speed may be increased to much higher rates when utilizing a stationary pin in accordance with this invention.

EXAMPLE 3 The invention was demonstrated on a Leesona Model l0-B downtwister modified to include a 6 inch long contact heater placed below the feed roll, and a stationary pin was placed in the yarn path between the heater and the take-up spindle. A 17/2 round cross section polycaproamide yarn was supplied to the machine from a yarn package. One full wrap of the yarn was placed on the stationary pin. The yarn was delivered at 148 yards per minute and taken up on the spindle while inserting 0.50 turns of mechanical twist. The stationary pin caused twist in the yarn being removed from the package to back up onto the heater surface maintained at 190 C to heat set the twist in the yarn. It was observed that the twist built up to an equilibrium level and thereafter the additional twist stripped past the stationary pin. The yarn had an average torque value of 60.

EXAMPLE 4 The method of Example 3 was repeated except a 20 denier bifilament yarn was used. The resultant yarn had an average torque measurement of 52.

EXAMPLE 5 A Whitin Model RYA drawtwister was provided with a 6 %inch long contact heater placed below the draw roll and a stationary pin was disposed in the yarn path between the heater and take-up spindle. A 20/1 bifilament cross secn'on yarn prepared from polycaproamide was supplied from an undrawn yarn package. The yarn was wrapped once around the stationary pin and rotated to pre-insert 80 turns of twist per inch in the yarn length between the draw roll and the disc. Upon starting the machine, the yarn was drawn at 985 yards per minute and taken up at a spindle speed of 9,500 r.p.m. whereby 0.26 turns per inch of mechanical twist was inserted during take-up. The twist trapped above the pin was heat set in the yarn by the heater which was maintained at 220 C. The

' stretch properties of the yarn were measured in accordance with the standard Leesona skein shrinkage test and yielded a value of 51 percent.

EXAMPLE 6 The method of Example 5 was repeated except the yarn was taken up on an auxiliary winder. The yarn was drawn at 1,800 yards per minute in this process and a 12 inch heater surface at a temperature of 225 C was used to heat set the yarn. Since the same amount of twist remained trapped in the yarn during that setting thereof, the yarn had a similar stretch potential.

EXAMPLE 7 A Schweiter Precision Coner Type KEK-PN was provided with a 10 inch surface heater located between the supply package and take-up spindle and a stationary pin was placed between the heater and the take-up spindle. The machine was supplied with drawn 17/2 polycaproamide multifilament yarn. The yarn was wrapped one time around the stationary pin and was in contact with the heater which was heated at 190 C. The machine was set at a winding speed of 235 yards per minute. A ribbon-like structure was imposed upon the yarn by the stationary pin whereby twist from the yarn being removed from the supply package backed up onto the heated surface of the heater where heat setting of the yarn in said twisted condition occurred. Relative yarn torque measurements obtained from samples of yarn produced by this method ranged from 45 to 55.

EXAMPLE 8 The method of Example 7 was repeated except a 20 denier bifilament yarn prepared from hexamethylene diamine in accordance with the procedures disclosed in copending U. S. Application Ser. No. 733,556, filed May 31, 1968, was substituted for the multifilament yarn. The resultant yarn appeared to possess a little more torque than the false twisted yarn of Example 7.

We claim:

l. A method for producing a torque-type yarn strand in a continuous operation wherein said traveling yarn strand has a ribbon-like cross section prepared from a thermoplastic organic polymer and is plasticized by heating to a temperature below the melting point and imparting a false-twist memory to the yarn prior to take-up at a lower temperature, the improvement which comprises pre-inserting from 20 to 250 twists per inch in the yarn strand within a heat-setting zone by cranking oppositely disposed broad surfaces which trap and maintain said pre-inserted twist in said yarn strand, said surfaces being located downstream of said zone, and heat setting said twist within said heat-setting zone.

2. A method as described in claim 1 wherein the yarn strand is a monofilament having opposed broad surfaces.

3. A method as described in claim 1 wherein the yarn strand is a multifilament yarn.

4. A method as described in claim I wherein the traveling yarn strand is received from a spinning position.

5. A method as described in claim 4 wherein the heat set yarn having a false-twist memory is wound upon a sleeve by a high speed winder.

Ponbbo UNITED S TATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,678,676 Dated July 25, 1972 Inventor) Ronald E. Rothwell and Charles W. Beringer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 36, "conditional" should be conventional-.

Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attestlng Officer Commissioner of Patent:

Claims (5)

1. A method for producing a torque-type yarn strand in a continuous operation wherein said traveling yarn strand has a ribbon-like cross section prepared from a thermoplastic organic polymer and is plasticized by heating to a temperature below the melting point and imparting a false-twist memory to the yarn prior to take-up at a lower temperature, the improvement which comprises pre-inserting from 20 to 250 twists per inch in the yarn strand within a heat-setting zone by cranking oppositely disposed broad surfaces which trap and maintain said pre-inserted twist in said yarn strand, said surfaces being located downstream of said zone, and heat setting said twist within said heatsetting zone.

2. A method as described in claim 1 wherein the yarn strand is a monofilament having opposed broad surfaces.

3. A method as described in claim 1 wherein the yarn strand is a multifilament yarn.

4. A method as described in claim 1 wherein the traveling yarn strand is received from a spinning position.

5. A method as described in claim 4 wherein the heat set yarn having a false-twist memory is wound upon a sleeve by a high speed winder.

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