US3616635A - Method for heat stabilization of synthetic thermoplastic yarns or threads - Google Patents

Abstract

THIS APPLICATION DISCLOSES A TWO-FOR-ONE TWISTER WITH A TENSION-CONTROL TO THE COLLECTING BOBBIN WHERE A DENSE BODY OF THREAD IS WOUND FOR SUBSEQUENT HEAT-TREATMENT TO STABILIZE ELONGATION CHARACTERISTICS.

Description

1971 P. R. PETERSEN 3,615,635

METHOD FOR HEAT STABILIZATION 0F SYNTHETIC THERMOPLASTIC YARNS OR THREADS Filed Sept. 16, 1968 INVENTOI? PHILIP R. PETERSEN Umted States Patent US. Cl. 57--157 R 3 Claims ABSTRACT OF THE DISCLOSURE This application discloses a two-for-one twister with a tension-control to the collecting bobbin where a dense body of thread is wound for subsequent heat-treatment to stabilize elongation characteristics.

This invention relates to the heat stabilization of synthetic thermoplastic yarns or threads and, in particular, to the heat stabilization of polyester sewing threads. In particular, this invention is an improved method of preparing a body of synthetic, thermoplastic yarn or thread for heat stabilization.

In recent years there has been a large increase in the manufacture and sale of permanent-press fabrics. These fabrics are usually subjected to a chemical treatment after weaving but before cutting and are oven heat-treated after the sewing has been finished in order to make permanent the shape and press desired. Cotton, which has been traditionally used as a sewing thread, is unsuitable for use as a sewing thread to sew together permanent-press garments because it is not resistant to the chemicals involved and lacks the needed abrasion resistance in a permanently-pressed garment. Accordingly, the garment in dustry has resorted to the use of synthetic thermoplastic fibers for sewing threads. For example, sewing thread is made of these materials by twisting staple length polyester fibers and thereafter doubling in the usual fashion. While these fibers produce a thread that is entirely satisfactory from a chemical point of view and is quite compatible with the oven treatment of pre-pressed garments, a problem arises in connection with synthetic sewing thread that does not exist when cotton is used. This problem stems from the fact that the garment industry has tremendous inventories of sewing machines which have been designed to handle cotton sewing threads and, because the stretch characteristics of polyester threads are quite different from those of cotton, serious mechaical difliculties have arisen. To solve the elongation problem suppliers of sewing thread have resorted to a heat treatment which has been found to modify the stretch characteristics of polyester sewing threads in order that those threads may behave sufficiently like cotton that conventional sewing machines may be used without modification.

In the past, the heat stabilization treatment of polyester sewing threads has been effected by winding a cylindrical yarn body on a hollow flanged metal support some seven to ten inches in diameter and ten or more inches long. The thread is wound in such a way that adjacent coils touch or nearly touch one another and thus form a very dense package up to an inch thick. This package is subjected to a heat treatment which in eflect makes the elongation characteristics, after the treatment, more nearly like those of cotton.

While sewing thread prepared in the foregoing fashion is entirely satisfactory, it is somewhat costly to produce because, after doubling, there is a twisting operation, and after the twisting operation, the thread must be unwound from the package on which it is collected for twisting and wound on the cylindrical body which supports it during heat treatment. Furthermore, the preparation of the thread "ice body for heat treatment requires that the winding be effected under conditions of rigidly controlled tension. After heat treatment of the body, another winding operation is required before the sewing thread is in a package suitable for shipment to customers. Any winding operation subjects the thread to some wear and thus causes some reduction in quality.

It is an object of the present invention to provide a method of preparing polyester sewing thread for heat treatment by which one of the winding steps is wholly eliminated and the resulting economy is achieved with an increase in the quality of the finished product.

It is a further object of the present invention to twist and collect sewing thread under controlled tension, as part of a single operaiton, whereby there is avoided the intermediate winding step between twisting and the winding of the package shipped to the customer with resulting reduction in cost and increase in quality.

Other objects and advantages of the present invention will be apparent upon consideration of the following detailed description of a preferred embodiment thereof in connection with the annexed drawings wherein the single figure is a schematic view in end elevation and in section of a two-for-one twisting machine modified for the practice of the method of the present invention.

In the drawing, the numeral 10 designates a stationary yarn body which is located around a hollow twister tube 11 provided with a flier 12 which functions to prevent the rubbing of the thread on the outside of the package. Thread is drawn upwardly from the body 10 through the flier 12 and passed downwardly through the tube 11. Yarn body 10 is located in a container 12a. From the lower end of the tube 11 the thread passes through a rotating disc 13 from which it is thrown out radially to be drawn upwardly between the container 12a and balloon control shield 14 to a pigtail guide 15. From pigtail guide 15 the yarn is led over a godet 16 comprised of a driven roller 17 having a frictional thread contacting surface and an idler 18 having grooves in the surface to cause the yarn to pass in a generally helical pattern back and forth between rollers 17 and 18 enough times so that the speed of drive cylinder 17 becomes an anchor point for the controlled stretching which takes place between godet 16 and an aluminum drum 19 which constitutes the bobbin upon which the thread is collected.

Bobbin 19 is a hollow aluminum cylinder having flanges at each end, the near flange 20 being apparent in the drawings. The thread is laid up by a so-called parallel traverse mechanism between the end flanges of the cylinder 19 as a tightly wound body up to one inch thick, having an internal diameter of about seven to ten inches and a length of about ten inches. Preferably the traverse is adjusted to lay the yarn up with a minimum helix angle or pitch such that adjacent threads on each course touch one another. This is not absolutely necessary, however, since any wind that produces a very dense body of thread is satisfactory. When the required amount of yarn has been wound, the cylinder 19 is dotted and subjected to heat treatment in the usual fashion.

The tension to which the thread is subjected between the godet 16 and the surface of the cylinder 19 is very critical. For example: A 50/2 cotton count (213 den. total) thread is spun of Kodel high tenacity polyester fiber (Eastman Chemical Products, Inc.) and twisted on the two-for-one twister utilizing twenty turns per inch twist and setting the tension at thirty grams while winding onto an aluminum bobbin such as the part 19 shown in the drawings. This bobbin can contain a layer of thread approximately /8 inch thick and is later heated in an oven until all of the thread on the bobbin reaches 375 F. The resulting thread is then ready for use after Winding and lubricant application.

- While the illustrated form of the invention shows tension developed between a godet and a rotating drum, it may be possible to impart suflicient tension by substituting a drag device for the godet 16.

While the invention has been described in connection with a two-for-one twister, it is equally applicable to any type of up-twister where the collection of the yarn is independent of the magnitude of the twist imparted to it. The illustrated two-for-one twister is a conventional one, as manufactured by Socit des Mcaniques Verdol.

While the invention has been described in conjunction with the preparation of sewing thread, it is applicable to other uses where the collection after twisting is required to be under conditions of tension independent of the twisting operation itself.

What is claimed is:

1. The method of preparing thermoplastic threads for heat treatment to improve the initial elongation characteristics that comprises withdrawing yarn from a package along a path While rotating the yarn about the axis of said path to a point of tension control, drawing yarn from said tension control point to a winding region under uniform conditions of tension and there winding a hollow thread body of superimposed courses of thread, each course being laid up at a helix angle so small that the adjacent coils of thread touch one another, said body defining a hollow core having an internal diameter no less than ten times the radial thickness of the thread body and thereafter heating said thread body.

2. The method of preparing thermoplastic threads for heat treatment to improve the initial elongation characteristics that comprises withdrawing yarn from a stationary package to a point of tension control along a predetermined path while rotating the yarn about the axis of said path to impart twist thereto, drawing yarn from said ten- 41 sion control point to a winding region under uniform conditions of tension and there winding successive, superimposed courses of thread to produce a hollow thread body having a core with an internal diameter no less than ten times the radial thickness of the thread body, the adjacent coils of each course of thread being close enough to one another to make a very dense thread body and thereafter heating said thread body until all parts of it have reache a temperature of 375 F.

3. The method of preparing thermoplastic threads for heat treatment to improve the initial elongation characteristics that comprises withdrawing yarn from a stationary package and drawing it to a point of tension control through a path passing axially through and then beside said package while rotating the yarn about the axis of the package to impart a two-for-one twist, drawing yarn from said tension control point to a winding region under uniform conditions of tension and there Winding a hollow cylindrical body having a core with an internal diameter no less than ten times the radial thickness of the thread body, adjacent coils of each course of thread touching one another and thereafter heating said thread body.

References Cited UNITED STATES PATENTS 2,158,607 5/1939 Bochmann 2423-128 2,729,051 1/1956 Clarkson 57-'62 X 3,277,640 10 1966 Colombu et al. 57-6 2 3,423,922 1/1969 Smith 5762 X 2,421,336 5/1947 Kline et al. 2872 JOHN PETRAKES, Primary Examiner US. Cl. X.R. 5734 HS, 62

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