US2936570A - Twisting of textile filaments - Google Patents

Description

May 17, 1960 D. F. ARTHUR ETAL v 2,936,570

TwIsTING oF TEXTILE FILAMENTS Filed Nov. 16, 195e .2/ .2:5 2529 5 39 /57 Q/ g i I,27 Gaf @57 INVENTORS ATTORNEYS United States Patent 4O TWISTING F TEXTILE FILAIVIENTS David Foxall Arthur, West Pontnewydd, Cwmbran, and Alan Frederick Weller, Newport, England, assignors to British Nylon Spinners Limited, Pontypool, England Application November 16, 1956, Serial No. 622,546 4 Claims. (Cl. 57-157) The present invention relates to improvements to, and modifications in, the processes of twisting and crimping textile filaments as described and claimed in the specification of our copending U.S.A. patent application No. 595,543.

In the above patent specification there is described, inter alia, -a process for imparting a false twist to a running textile filament wherein the filament is caused to bear against, and be rotated by, the inner peripheral surface of one end portion at least, of a rotating twist-tube and on one side of the axis thereof. The internal surface of the tube at least at its yarn-contacting end-portion is composed of a non-abrasive material having a high coeiiicient of friction with the filament. Such a falsetwisting process can, if the filament is heat-set while in the highly twisted state, be very conveniently used to insert a crimp in thermoplastic filaments such as nylon as is described in the aforementioned specification.

It is stated in the specification that, once the twist-tube is rotating at or above a given minimum angular velocity, the value of turns per inch of twist inserted in multifilament yarns is very little affected by variations input tension or speed of the yarn, o-r by variations in speed ofthe tube above the critical speed. This minimum angular velocity can be calculated for any given value of turns per inch of twist and denier of textile filament.

We have now discovered that, although the above proposition is broadly true, there is a relationship between filament speed, the speed of that portion of the inner peripheral surface `of the tube with which the filament makes contact and filament input and output tensionson the one hand and turns per inch of twist inserted 0n the other, for any given dimensions of the tube and of the angles of entry land exit made with it by the filament. According to this relationship, there is an optimum value for the ratio of 'filament speed to the peripheral speed of thatpart of the tube with which the filament makes contact; that is to say, that at a certain value of this ratio, the greatest number of turns per inch of twist will be inserted in the filament. This is, of course, due to the complicated frictional effects between the filament and the inner peripheral surface of the tube resulting from` the forward motion of the filament and the relative transverse motion of the tube surface.

if the abovementioned ratio is of a value lower than the optimum, it will be necessary, in order to achieve the desired turns per inch of twist, to have an input tension higher than is desirable for effective setting of the filament in the highly twisted state. For the best heatsetting results, it is desirable to allow the filament to shrink somewhat during heat-setting, say by at least 2% and preferably by at least 3% and such a shrinkage can normally only occur in nylon filaments for example, if the tension in the lament is low, i.e. of the order of 0.2. gram per denier, or less, under the normal conditions fo-r heat-setting such a filament on the run. The conditions (i.e. temperature and time of heating and soV 2,936,570 Patented May 17, 1960 race cooling) for the effective heat-setting of a running textile filament will depend on the nature and denier of the filament, the nature of the heating and cooling media and the speed of the filament, as well as on the amount of contraction allowed during the setting treatment as a whole.

If the above-mentioned speed ratio is of a value significantiy higher than the optimum, for example 0.9 or greater, not only will the turns per inch of twist not be as great as could be achieved, but also, owing to the increased tension multiplying factor, the output tension (with the drawing-olf speed remaining constant) will be of a value such as may cause undue wear on the filamentcontacting surface of the twist-tube.

The discovery concerning the optimum value of the abovementioned ratio enables a satisfactory compromise to be worked out between the conflicting requirements of the twist factor necessary for producing the necessary crimping deformations and of the conditions required to set those deformations effectively.

The value of the ratio for optimum conditions when crimping multifilament yarn of nylon according to the invention is around 0.8. However, since the value of the output tension rises sensibly proportionally to the value of the speed ratio (the drawing-off speed of the filaments remaining constant) it is only desirable to `work at the optimum ratio for the lower denier yarns (say, up to denier) as the 4value of the output tension becomes too high for satisfactory crimping when working at the optimum speed ratio and an input tension of 0.2 gram per denier with heavier denier yarns. In the latter case, a ratio tof 0.54 produces the best results in all the circumstances. It can be said, therefor, that for textile filaments as defined in our previous specification No. 595,543 with which the invention is solely concerned, the value of the speed ratio must be at least 0.50, and is preferably of a value of 0.8 for nylon multifllament yarns lof up to 70 denier, when the input tension is of the order of 0.2 grams per denier, or such tension as wiil allow of a sensible amount, say 3%, of shrinkage of the filament during setting, without impairing the stability of running of the filaments. Multilament Vyarns or cords of up to 840 denier can be successfully false-twisted according to the invention, although crimped yarns lare normally required to be of a much lower denier than this. i

The present invention, therefore, comprises a process for imparting a false twist to a running textile filament wherein the filament is caused to bear against, and be rotatedby, the inner peripheral surface of one end portion, at least, of a rotating twist-tube and on one side of the axis thereof, the internal surface of the tube at that one end portion at least being composed of a non-abrasive material having a high coefficient of friction with the `filament and wherein the ratio of the filament speed to the surface speed of that part of the innerl peripheral surface of the tube with which the filament makes contact is not less than 0.5. The invention also comprises a process for crimping a thermoplastic textile filament wherein a false twist is imparted to the said filament according to the above-mentioned process and the filament is heated over succeeding lengths of itself which are in the highly twisted condition to an extent sufficient to set the twist therein whilst the filament is allowed to contract by a sensible amount, the succeeding lengths of twist-set filament are then cooled before untwisting, and the filament is untwisted and then wound up under low tension.

An understanding of the invention may be faciiitated by reference to the accompanying drawings forming a part of this specification in which:

Figure l is a schematic showing of the crimping of thermoplastic multifilament yarn according to the invention; and

Figure 2 is an enlargedl sectional view of the twist tube, rotated clockwise so that its axis is horizontal, schematically shown in Figure l.

Referring to Figure 1, yarn 13 of thermoplastic material is withdrawn over one end of a supply package 17, and is then passed around the drum of a magnetic hysteresis tensioner 19 which imposes a constant output tension on the yarn. The yarn is then led through an infra-red heating device 21 comprising a glass tube 23 having electric resistance coils wound therearound.

After passing through the tube, the yarn travels through the air for a sucient time for it to cool below its plastic state, and then passes into one end of av twist-tube 27 such as that illustrated in Figure 2. The twist-tube is mounted with its axis at an angle to the vertical such that the yarn led directly through and from the heating device makes contact with one side 29 of the inner peripheral surface of a rubber bush (see Fig. 2) Contained within the twist-tube. The yarn is led from the twisttube around a pulley-wheel 31, which ensures contact of the yarn with the bush at this end thereof, and therefore along the whole length lof the bush. After passing over kthe pulley-wheel 31 the yarn is led through the nip of a pair of forwarding rolls 33, 35, which feed the yarn forward at a slightly greater speed than that at which it is eventually wound up by the roll 37v on the'package 39. Thus the yarn between the rolls 33, 35 `and the wind-up package 39 is relaxed slightly. In operation, the yarn is given a high degree of false twist by means of the twist-tube, which high twist in `one direction feeds back through the heating device to the tensioning device, and is set; the yarn in its twist-set conditionl is allowed to cool somewhat between the heating device and the twist-tube; twist in the opposite sense is imparted to the twistset yarn directly on leaving the twist-tube; and the now crimped yarn is wound up under a low tension.

Referring now to Figure 2, the twist-tube comprises a ixed annular portion i, and a drive annular portion 3 mounted on roller bearings 5, 7 therein. The driven annular portion 3 is rotated by band 9. Fitted Within the driven annular portion 3 is a rubber bush 11, the inner surface of which makes direct contact with the yarn 13. The yarn is led to and away from the tube at an angle to the asis thereof. Thus the yarn when suitably tensioned is kept in contact with the'whole length of' the inner surface of the rubber bush, and also with the two curved end portions thereof.

In order to demonstrate more clearly the interaction of the various factors referred to above, the following examples show the values of the factors for the best operating conditions when crimping multilament nylon yarns of various deniers.

, Y4 rubber with carbon' black filler, and having the following dimensions: Y Y

(i) Length of bush 1% (ii) Internal diameter of cylindrical portion of bush- 5A; (iii) Thickness of bush 7/16 (iv) Radius of curvature of end lips o-f bush 7A@ A 30 denier ten-lament nylon yarn was led from a supply packageV to an additive tension device which ap-V piied a tension ofy 6 grams (0.2 gram per denier) as input tension on the yarn reaching the twist-tube which was rotating at 2,000 r.p.m. Between the tension device and the twist-tube the yarn was led through an infra-red heater in order to heat-set the yarn in its'highly-twisted state, there being a gap of somel 6 inchesv between the end of the heater and the twist-tube to all-ow the hot yarn to cool suiliciently to below the temperature at which it is in a plastic condition. The infra-red heater was of the type in which the heatingV element (an electric resistance) is positioned along one focus of an elliptical reflecting tubeV and the yarn passes along the other focus of the tube. The temperature of a therrnocouple in equilibrium in the yarn path Ywithin the tube was 242 C. The yarn was drawn through the twist tube at 265 feet a minute by a roller positioned on the other side of the twist-tube from the heating tube, the yarn being wrapped twice around the roller, and the yarn was caused to enter one end of the twist-tube along a path the projection of which was at an angle of S5 to the proiection of the axis of the tube (an angle ot' at least SOY being preferred according to the invention), to run in lirm, steady contact with the inner peripheral surface of the rubber bush on one side of the axis thereof without any tendency to jump, and to leave the twist-tube along a path at a similarly-defined angle of y". The tension in the yarn between the twist-tube and the drawing-off rolls was measured at 22 grams. Between the drawing-oft' rolls and the wind-up the yarn was relaxed, so that thel winding was carried out under low tension. speeds ratio (yarn speed to surface speed of inner periphery of bush) was 0.81, the twist inserted in the yarn was 131 turns per inch, and the yarn was allowed to contract by 3.5% between the drawing-off rolls and the tension device. v

Examples 2 to 5 Forconvenience', theseV examples are presented in table form. The* apparatus was similar to that described in Example 1,v and these examples show the varied andV 5'0" varying. conditions' in processes similar to that of Example 1 for increasing deniers of nylon yarn crimped at 26'5 feet a minute. It' will be observed that the temperature of thev setting tube is increased with denier and that the conditions are always'such that at least 3% contraction of 55 the yarn isl allowed.

Heat Yarn Angular setting Twist Denier] speed,l Speeds velocity Entry Exit ten- Percent temper turns Example Number Number of Iect/ ratio of tube, tension, sion, shrinkatnres per laments :ninr'.p.m. grams grams age in yarn inch ute path,

2 45/15 2 65 0. 81 2, 000 8 30 3. 3 250 105 3.... (iO/2,0 265 0.81 2, O00 12 42 3. 4 255 101 e 100/34 265 0.54 3, 000 20 42 4. 2 270 72 5 150/50 265 t). 4 3, 000 30 66 4. 0 290 57 Example I The twist-tube used in this example, andv in all thel following examples, was one such as is described and illustrated herein and in the specification and drawings of our cto-pendingk application No. 595,543 having. an in ternal surface inthe form of a bush, composed of natural 'I5U ments for crimpingv comprising the steps of tensioning" Although a yarn speed of 265 feet/minute is lexcmpii-YV Inches Under these optimum conditions, when the y a running length of textile filament between iixed points, twisting the filament length by frictional contact with an encircling, annular rotating surface composed of nonabrasive material having a high coeicient of friction with the textile filament, the diameter of said surface exceeding the diameter of said lament, whereby a plurality of turns of false twist is imparted to the lament for each revolution of said surface, the speed of said filament being at least half the peripheral speed of said surface, the axis of said surface being angulated with respect to the filament path approaching and leaving said surface, applying heat to said filament length at a point leading said surface sufficiently to permit substantial cooling therebetween, and maintaining the tension in the portion of said length leading said surface at a value not exceeding about 0.2 gram per denier, whereby the lament is permitted to shrink at least about 2.0% between the point of heat application and said surface.

2. A process as delined in claim 1, wherein the angle between the axis of said surface and the filament path approaching said surface is at least 80.

3. A process as defined in claim ,1, wherein the speed of said filament is about 0.8 times the peripheral speed of said surface, andthe filament does not exceed denier. I

4. A process as deiined in claim 1, wherein the false twisted filament is wound up under low tension.

References Cited in the file of this patent UNITED STATES PATENTS 2,463,620 Heberlein Mar. 8, 1949 2,673,442 Long Mar. 30, 1954 2,753,679 Von Scholler et al. July 10, 1956 2,803,109 Stoddard et al. Aug. 20, 1957 FOREIGN PATENTS 440,546 Italy oct. 13, 194s 496,585 Great Britain ]Dec. 2, 1938 500,823 Great Britain Feb. 16, 1939

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