US3564833A

US3564833A - Friction false twisting

Info

Publication number: US3564833A
Application number: US792981*A
Authority: US
Inventors: Roy Spencer Holliss
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1968-01-30
Filing date: 1969-01-22
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23
Also published as: ES363098A1; BR6906009D0; DE1904614A1; CH508748A; FR2000984A1; AT313124B; CH134869A4; IE32865B1; IE32865L; BE727695A; NL6901157A; GB1212393A; CA922182A

Abstract

APPARATUS FOR FRICTION FALSE TWISTING IN WHICH A TWIST BARRIER COMPRISING A STATIONARY CYLINDRICAL PIN IS SO POSITIONED AT A DISTANCE OF THE ORDER OF 1/8 INCH FROM THE PERIPHERY OF THE OUTLET END OF A FRICTION FALSE TWIST TUBE WITH WHICH THE YARN BEING FALSE TWISTED MAKES FRICTIONAL CONTACT AND TO GUIDE MEANS AROUND OR THROUGH WHICH THE YARN IS WITHDRAWN FROM SAID TWIST TUBE THAT THE YARN MAY BE PARTIALLY WRAPPED AROUND SAID PIN WITH AN ARC OF CONTACT THEREWITH OF BETWEEN 60* AND 100*.

Description

FRICTION FALSE TWISTING I Filed Jan. 22, 1969 I lnvenlof ,Fw pi /Mme A644 Ass United States Patent C 3,564,833 FRICTION FALSE TWISTING Roy Spencer Holliss, Pontypool, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Jan. 22, 1969, Ser. No. 792,981 Claims priority, application Great Britain, Jan. 30, 1968, 4,777 68 Int. Cl. D02g 1/04; D01h 7/92, 13/08 US. Cl. 57--77.4 1 Claim ABSTRACT OF THE DISCLOSURE The invention concerns improvements in or relating to friction false twisting.

The art of friction false twisting of yarns, by means of a rotating twist tube having flared end-portions, at least, composed of material having a high coefficient of friction with the yarn, is relatively new.

The basic principles of the process are described, with particular reference to the bulking of synthetic polymeric filaments and yarns, and the process and apparatus broadly claimed in the specifications of British Letters Patent Nos. 797,051 and 801,335.

A difficulty that has been encountered rather more specifically in friction false twisting than in false twisting by means of conventional spindles having twist-trapping pins or rollers, is that of twist bleeding, which term is used to define the occurrence of occasional lengths of yarn having, improperly, some residual twist following de-twisting in the false twist sequence of twisting and de-twisting.

Such twist bleeding, which is randomly distributed within yarn from one processing position, and between yarns from different processing positions, is evident as an undesirable short-term flashiness (dark streaks) in the resultant fabric, e.g. a weft-knitted fabric.

It has now been discovered that a critical amount of positive twist trapping by means of a twist barrier closely spaced from the outlet of the friction false twisting tube used for bulking can lead to the virtual prevention of twist bleeding, as evidenced by the disappearance of flashiness in resultant fabric, without significant effect on the bulk of the yarn.

The amount of twist trapping is critical, because too little will not assist in overcoming the defect of twist bleeding while too much can have the effect of virtually eliminating the bulk from the yarn.

According to the invention, therefore, in and for the process of friction false twisting, a twist barrier comprising a stationary pin is so positioned with respect to the outlet end of a friction false twist tube with which the yarn being false twisted makes frictional contact and to guide means around or through which the yarn is withdrawn from said twist tube, that the yarn may be partially wrapped around said pin with an arc of contact therewith of between 45 and 180 and that contact with said pin is made by the yarn immediately after it has left contact with said outlet end of said twist tube.

The invention also provides an apparatus for operating the above process of friction false twisting.

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Preferably the stationary pin is cylindrical and has a hard wear-resistant surface. Ceramic, bright chrome and matt chrome surfaces have proved satisfactory.

An arc of contact of between 60 and is preferred, as within this range twist bleeding is minimised without damaging the yarn or its filaments and without reducing the bulk in a yarn that has been bulked by the friction false twisting process.

Below 60, the amount of twist bleeding begins to increase rapidly, so that below 45 the extent of improvement is too marginal to be acceptable. Over 100, for example between 100 and the tension is such as to break any stray filaments, which is usually undesirable. Above and in particular when a complete (i.e. 360) wrap is made around the pin, the tension is so high that the bulk is removed altogether.

By immediately after is meant that the stationary pin should be positioned as closely to the outer periphery of the outlet end of the twist tube as is possible consonant with remaining free from contact therewith and with allowing threading-up of the twist tube and pin to be accomplished readily. A distance of as little' as inch has proved satisfactory; but even as close a distance as 3 inches has proved to be relatively ineffective in minimising twist bleeding.

The diameter of a cylindrical pin is not too critical, within the range of realistic diameters; but a small diameter, for example inch, is preferred to a larger one, for example inch.

As an instance of the efficacy of the invention, the following detailed examples thereof are given, though they should not be construed as limiting the invention in anyway.

EXAMPLE I being composed of polyurethane having a inch inner diameter, flaring to an outer diameter of 2 inches, and short hardness 92 and 88 respectively. The heater upstream of the twist tube was at a temperature of 225 C., and the yarn was positively fed into and withdrawn from the twist zone by draw rolls and take-out rolls, respectively, so as to underfeed the yarn through the zone at an underfeed of 3.3% and a concomitant tension of 19 grams. The tension downstream of the twist tube was 50 grams.

A stationary, cylindrical matt chrome pin of inch diameter was positioned at a distance of inch from the outer periphery of the polyurethane end-portion of the twist tube, such that the yarn made an arc of contact of 90 around it end route to the take-out roll.

The yarn so produced was satisfactorily bulked and gave no indication of twist bleeding, as evinced by fiashiness, when made into a weft-knitted fabric.

EXAMPLE II With the same apparatus and stationary pin characteristics as described in the previous example, a 150 denier/ 30 filament yarn derived from polyethylene terephthalate was false twist bulked at 1000 feet/minute. The twist tube was rotated at 10,000 rpm. and the heater upstream of the tube was at a temperature of 220 C. The yarn was positively fed into and withdrawn from the twist zone by draw rolls and take-out rolls, respectively, as above, so as to underfeed the yarn through the zone at an underfeed of zero percent and a concomitant tension of 25 grams. The tension downstream of the twist tube was 100* grams.

The yarn so produced was satisfactorily bulked and gave no indication of twist bleeding, as evinced by flashiness, when made into a weft-knitted fabric.

Although the specific conditions may vary somewhat with other synthetic polymeric yarns, the invention has been found to be equally effective with other polyamide and polyester yarns, for example, those derived from polycaprolactam and polyethylene isophthalate, respectively, and with yarns derived from such synthetic polymers as polyacrylonitriles and polyolefines.

The accompanying diagrammatic drawing illustrates the invention.

In the drawing, yarns Y and Y are led slightly separated away from a heater (not shown and by which the twist is set) through guides 1, 3 to the inlet end of two contra-rotating twist tubes 5, 7. As indicated, the yarns pass diagonally through the hollow twist tubes, making contact at each end thereof with a bush of polyurethane, the outlet ones of which are shown at 9, 11.

From the bushes 9, 11 the yarns are partially wrapped around stationary cylindrical pins, 13, 15, acting as twist barriers, the arc of contact being, for example 90. Both the yarns are then brought together on the periph- 'ery of take-out roll 17, when they may be passed to either plying or separate wind-up stations (not shown).

What is claimed is:

1. Apparatus for friction false twisting in which a twist barrier comprising a stationary cylindrical pin is so positioned at a distance of the order of inch from the periphery of the outlet end of a friction false twist tube with which the yarn being false twisted makes frictional contact and to guide means around or through which the yarn is withdrawn from said twist tube that the yarn may be partially wrapped around said pin with an arc of contact therewith of between and References Cited UNITED STATES PATENTS 2,936,570 5/1960 Arthur et al. 5777.4X 3,154,906 11/1964 Van Assendelft et a1. 5777,4X 3,204,396 9/1965 Poster at al. 5734 3,330,104 7/1967 Dunwoody 57-512 3,439,485 4/1969 Lloyd 57-34 DONALD E. WATKINS, Primary Examiner