US2936567A - Twisting of textile filaments - Google Patents

Description

United States Patent 2,936,561 rwisriNG F TEXTILE mAMENrs John Percival Russell,l Croesyceiliog, Cwmbran Eric Stutchfield,` West lfontnewydd, 'Cwmbram John Ralph Myers, Croesyceiliog, Cwmbran, and David Foxall Arthur, West Pontnewydd, Cwmbran, England, assignltrlilidto ,BritishV Nylon Spinners Limited, Pontypool, Eng- `Appiieiiiimirpiy z, 1956, serial No. 595,543 claims priority, application Great Britain July 19, 195s 4 claims. (ci. `5'/'11.4)

.very many years, and of late they have been found par ticularly suitable for use in crimping thermoplastic textile lfilaments by a twisting, setting, and back-twisting se- :quence. It will be appreciated that a fase-twist-tube nables such a crimping operation to be carried out in continuous fashion,I instead of in separate steps, as in the case with certain other crimping processes. Heat is applied to the filaments while they are in thehighly-twisted ycondition to set this twist, so that when the equal and opposite twist of the untwisting occurs after the lament's -leave the twist tube, crimpingoccurs.

Th@ Principle 1111011 which all known false-twist-tubes i" have operated is to cause the running filaments to acquire the rotational motion of the tube by means providing for contact with a part or parts of the inside of the tube whereby each revolution of the' tube applies one revolution to "the filaments. ,Thus the laments may be caused to pass round a pin orpulley wheel mounted within the tube across the axis thereof or trapping means may be provided ,tortrap them against one side of the tube. Alternatively, ,fthe bore of the tube itself may be made eccentric over fsome part of its length so that .the filaments are caused to acquire the rotational motion of the tube by taking a `4short path away from the axial line. In other tubes, the laments enter through a radial hole at one end of the Qtube, i.e. through a hole displacedl radially from the axis ofthe tube.

`In the process wherein a running textile filament is crimped by means of a false-twist-tube, a very high de- --gree of twist is required; for instance, 90 turns per inch is by no meansextraordinarily high, although around textile filament and having its internal surface, at least at one end thereof, composed of a non-abrasive material having a high coeicient of friction with the textile filament required to be twisted thereby. The invention also comprises a process whereby a false twist is imparted to a running textile filament by causing the filament to bear against, and be rotated by, the inner peripheral surface of one end, at least, of a twist-tube, and on one side of the axis thereof, the internal surface of the tube et that one end at least being composed of a non-abrasive material having a high coefcient of friction with the filament. The invention also comprises the crimping of a thermoplastic textile filament by such a process, wherein 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, the succeeding lengths of twist-set filament are then cooled before untwisting, and the'untwisted filament is wound up under low tension in crimped form.

According tothe invention, the filament is twisted by direct frictional contact with the inner peripheral surface of the tube, and thus, if the filament is held steady in the same relative position on the periphery of the tube, the ratio of the rotational speed of the filament to that of the tube will depend on the ratio of the inner diameter of the tube to the diameter of the filament. It follows that, as this last ratio will be relatively large, say, of the order of 250 to 1, for a given degree of twist and a given throughput, the speed of the twist-tube can ,be considerably reduced in comparison with a twist-tube operating according to the conventional principle in which one rotation of the tube is never capable of inserting more than one twist in the filament passing through it. Furthermore, a considerably enhanced throughput can be achieved at relatively moderate rotational speeds of the twist-tube.

By a material having a high coefficient of friction with the textile filament is meant not only a material which, per se, has such a coefficient of friction, but also material which by reason of its surface characteristics and/or resilience has such a coefficient in practice, i.e. under operating conditions for any particular textile filament as held against the material by its own tension or by other means.

As examples of materials which may be used to line the twist-tube, various sorts of rubber are suitable to a higher or lo-Wer degree, but the most eminently satisfactory material is natural rubber with carbon black filler. This material attains a polished condition after a certain amount of use, which appears to confer the necessary frictional qualities combined with resistance to wear, which are the critical features for a successful material. The filament is caused to bear against the inner periphery `of the twist-tube on one side of the axis. thereof by 75, turns per inch satisfactory .for most multilament yarns lof between SO'andV 100 denier. 'Thus in order .that the processV shall be reasonably productive it .has .beennecessary to rotate the tube at very high speeds, and

-speeds of the order of 30,000 rpm. are often used. As

:an example, in order that nylon continuous filament yarns :should berrimpled and woundupat a speed of 33 feet per minute, a rotational speed of 28,000 rpm. has been necessary. Such high rotational speeds of the twist-tube obviously create difficulties relating to their construction fand maintenance, and it is the object of the present invention 'to achieve'a satisfactory fand, indeed, enhanced `=productivity of crimped yarnl at considerably lower rota- "tiorialfspeeds of the twist-tube.

comprises ta' .twist-tube Jfor imparting Ya false twistA toma leading it towards and/or away from the tube to a guide,

or guides, the path between the end of the tube and the guide or guides being at an angle (up to approximately `a rightV angle) to the projection of the axis of the tube.

It is necessary in the first caseto ensure that the correct amount of pre-tensioning has been applied to the filament. The correct angle and pre-tension for each filament can best be discovered empirically, and it should be such that some little slip occurs between the periphery and the filament, which condition, besides-representing the optimum for twisting effect, is also consonant with no damage to the filament. lf the slip is allowed to be too great, damage may occur. Tensions such as are used in any normal false twist crimping process are satisfactory` and must be such as to hold thevlilainent firmly 0 A'I`his'object is achieved by thepresent inventionwhich ..7

against the inner periphery of the tube without jumping. One embodiment of the invention will now 'be described with reference t0 the accompanyingdrawings, in 'which Figure 1 is a section through a twist tube according to the invention; and Y Figure 2 is a sketch showing the use of a twist-tube according to the invention in a process for crimping a thermoplastic, textile filament. l

Referring particularly to Figure 1, the twist-tube comprises a iixed annular portion 1 and a driven 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 1l, the inner surface of which makes direct Contact with the yarn 13. The yarn is led to the tube at an angle to the axis thereof, and led away from the tube over a pulley 15, at a similar angle to the axis of the tube. 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. The dimensions of a twist-tube which have been found to be satisfactory in practice, are as follows:

Referring now to Figure 2, a yarn 13V 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 2l comprising a glass tube 23 having electric resistance coils 25 wound therearound. The device is sutlciently long to ensure that the twist in the thermoplastic yarn may be set by means of the heat produced by it at the high values of yarn throughput possible in this invention. After passing through the tube, the yarn travels through the air for a suicient time vfor it to 'cool below its plastic state, and then passes into Vone end of a twist-tube 27 such as that illustrated in Figure l. Thettwist-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 the rubber Vbush contained within the twist-tube.

The yarn is 'led from the twist-tube around a pulley-wheel 31, which ensures contact of the yarn with the bush at this end thereof, and therefore along the whole length of the bush. It is a question of experiment to tind the most suitable .angles of entry and exit of the yarn, and they will depend mainly. on the denier of the yarn and the number of turns per inch of twist it is desired to insert in it. In general, however, it may be stated that angles between 45 and 90 are required, the greater angles imparting vhigher vtwist than the lesser. The angles referred to are that between the yarn entry path and the projection of the axis of the twist-tube, and that between the yarn exit path and the projection of the axis of the tube. After passing over the pulley-wheel 31 the yarn is led through the nip of a pair of forwardly rolls 33, 35 which feed the of turns per inch of twist inserted in the yarns is very little affected by variations in tension or speed of the yarn, or by variations in speed of the tube above the critical speed, or by the amount of wear of the material forming the inner surface of the tube. The reason for this is that, naturally, for crimping purposes, the number of turns per inch will be high, and, at these high values, the increase in torque to be imparted to the yarn to raise the number of turns per inch by, say, 5%,.will require to besomething of the order of 30%. Thus the settings of tube speed, and yarn tension and speed are not lrequired to be controlled within very narrow limits, as in some other processes.

The minimum angular velocity, in revolutions per minute, of the twist tube can be ascertained from the formula:

V`=T t 121ty RM where Y t is the speed of the textile filament in feet per minute.

yarn forward at a slightly greater speed than that at I,

kwhich it is eventually wound up lby the roll 37 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 falsetwist 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 condition is allowed top cool ysomewhat between the heating device and the Vtwist-tube; twist in the opposite sense is imparted to the `twist-set yarn directly on leaving the twist-tube; and the now crimped yarn is Wound up under a low tension.

VWe have found that, using an apparatus according Vto VVthe invention, as generally described above, in a process ,for crimping `rnultifilament yarns of, for example, poly- Yhexamethylene adipamide, once the twist tube is rotating et or above a given minimum angular velocity, the value Turns per inch Ry is the radius of the textile filament in inches. RM is the internal radius of the twist-tube in inches.

Furthermore, the apparatus produces a textile filament, of a given nature, of constant twist factor (i.e. turns per inch multiplied kby the square root of the denier), for example, of the order of 680 or thereabcutsl for polyhexamethylene adipamide yarn comprising filaments of v3 denier each, so that once the apparatus is arranged to give the optimum twist to sucha textile filament of a certain denier, it will be correct also for imparting the optimum twist to such filaments of any other denier.

To illustrate the variation in turns per yinch of twist with denier, the'followingv table shows `the inter-relation of these two factors on multifilament yarn of polyhexamethylene adipamide, with a tube rotating at 15,00 r.p.m., tension on the yarn of 25 grams, and a throughput of 170 feet per minute. kthe tube at the same side of the axis thereof, at an angle vof 45 to the axis of the tube. v

TABLEl Yam Denier 21o 15oV 100 7o eo 45 so 'ramper inch 42 55 1o sa as 103l 125 the axis thereof atan angle of 45 to the axis ofthe tube.

TABLE 2 Throughput in teet/mlni As examples of the use of the twist tube of the vinvention in processes for crimping multilament yarn of lpolyhexamethylene adipamide inV a continuous fashion, the

Y following process conditions are given in VExamples `l 31o 1 1 inclusive:

Example 1 Multlament yarn from asnpply Ypackage is 4.led

through a tensioning device, such as amagnetic hysteresis type and thence over and in contact with a metal plate, electrically heated to 23.5 C., to thc twist-tube `which. 'is rotating at 1'50.0;r.p.m. Guides are so positioned;v above and below the twist-tube, wvhose .axisfof :rotation is The yarn enteredand left cal, that the yarh enters andfleaves the tube, at'one side of the axis thereof, at an angleof 45 to the axis of the tube. Under the above conditions', yarn may be processed at speeds between 2O and 60 feet/minute, and wound up ona package under low tension.

Examples 2 to 9 The process of Example l is carried out'on 30 and 60 denier multiilarnent yarn but this is heated while in the highly-twisted condition by means of radiant heat within a tube, throughthemiddle of which the yarn passes, instead of by contact with the hot metal plate. The tube is 25 cms. longV and made of glass and the heat lis generated by an yelectric resistance wire coiled around the outside of it. The temperatures expressed are those recorded by a thermocouple in equilibrium in the yarn path the tube, and are the maximum temperatures so recorded.

i Through- Temper- VExample No, Yarn A putin Tension, ature,

' Denier feet] grams C.

minute so 205 6.5 534 60 205 22.0 413 60 500 5.5 545 60 300 23.0 545 30 200 3.5 55s 30 200 19.0 55s 30 500 3.5 41s a 300 21.0 419 Example 10 150 denier multifilament yarn was crimped by a process similar to those described for Examples 2 to 9 above, except that the heater tube was only 13 cms. long. The maximum temperature within the tube was 705 C., and the crimped yarn was produced at a speed of 200 feet/ minute, with an ingoing tension of 24 grams.

Example 11 60 denier/ 10 filament yarn of polyhexamethylene adipamide is led from a supply package, through a magnetic hysteresis tension device which imposes an output tension of 25 grams on it, to the twist-tube rotating at 4000 r.p.m., and enters at an angle of 80 to the projection of the axis of the twist-tube. Positioned between the tension device and the twist-tube, so as to heat the yarn passing through it in its highly-twisted condition, is an infra-red heater 3 feet in length. The heater comprises a rod-like electric heating element positioned along one focus of an elliptical cross-section reflector tube surrounding it, and the yarn passes along the other focus of the ellipse. rIhe temperature within the tube is 224 C., as measured by a thermocouple in equilibrium in the yarn path within thev tube. The yarn leaves the twist-tube at `an angle of 80 to the projection of the axis thereof and is wound up under low tension at a speed of 200 feet/ minute.

Example 12Y Polyhexamethylene adipamide monoiilament of l denier is processed in continuous fashion by a twist-tube of the invention and in accordance with the arrangements of Example 11, except that the pre-tension imposed upon it is less than 2 grams, and the twist-tube is rotated at 4,600 r.p.m. A twist-lively filament is thus produced having some 20 turns per inch inserted, set, and removed in continuous fashion. The twist factor is low in this case owing to the dilerent frictional nature of the surface of the monofilarnent, and owing to the greater torque needed to insert a given twist in such an elemental structure as a monolament than is required for a multiiilament yarn.

Example 13 50 denier multilament yarn of the synthetic linear polyester sold as Terylene (registered trademark) was crimped in accordance withv Example ll', 'but with the twist-tube rotating at 4,600 r.p.m.

` It should be stressed that, in all the above examples, the yarn should undergo a suicient amount of cooling after heating and before untwisting to ensure that 'it is not in a plastic condition such that actual deformation 'of it will occur during untwisting. A suicient `space between heater and twist-tube, in which the yarn passes through the ambient atmosphere, will provide the conditions for this cooling. It should also be mentioned that, if the twist-tube itself is suitably mounted sothat its axis is inclined to Vthe vertical by the requisite angle,` say 45, as shown diagrammatically in Figure 2, a convenient horizontal disposition of the ,several pieces of apparatus can be achieved.

Although electrical heating by contact or radiation has been described for setting, such can also be achieved by pressure steam, or by contact with heated solid particles, such as glass, in uidized condition brought aboutby the passage of air therethrough. The twist-tube of the invention has one further great advantage over those previously known, in that it is capable of imparting a false twist to several textile lilaments at once. Guides may be so positioned at the entrance to and exit from the tube that a number of textile filaments may be maintained in contact with different relative positions of the inner periphery of the tube. Thus, two, three, four or more textile filaments can be processed simultaneously, and this added productivity of the invention further increases its usefulness over the conventional false twist-tube and processes utilizing the same. Furthermore, by a suitable arrangement of supply and wind-up packages and guides, it is possible to impart false twist of differing senses to a. plurality of textile laments, and to ply oppositely initially-twisted textile filaments together to produce balanced yarns. In this case, some textile iilaments will pass through the tube in one direction, and some in the other; or one in one direction, and one in the other.

Suitable thermoplastic textile filaments for crimping include those of the synthetic linear polymeric amides or esters, such as nylon or Terylene (registered trademark), and those of cellulose acetate and triacetate. It is also possible to crimp non-thermoplastic textile tla ments which have been treated with a thermosetting agent. If the textile filament to be crimped is a monoiilament, it will not be practicable or necessary to impart such a high number of turns per inch of twist as for a multiflament yarn. Useful monolaments of a twistlively, rather than crimped, nature may be produced with a twist of from 20 to 30 turns per inch, or there abouts, which iilaments may be incorporated in fabrics in such a way as to impart stretching to those fabrics.

Finishing of articles containing yarns crimped according to this invention may be carried out in similar manner as for any known crimped yarns produced by twisting, setting and back-twisting. However, owing to the relatively far higher speed of production of the yarns according to the invention, it may be advantageous to develop the bulkiness and stretchiness of the articles somewhat more slowly, and a convenient time for doing this is provided by the normal scouring ltreatment in liquid up to, say, 50 C. in temperature.

What we claim is:

l. Apparatus for imparting false twist to textile laments comprising a rotatable member having an axial bore with outwardly ared ends extending therethrough, means guiding a textile filament to one end of said bore along a path angulated with respect to the bore axis of the order of between 45 and 90, and means guiding the textile filament from the other end of said bore along a path angulated with respect to the bore axis of the order of between 45 and 90, the interior surface of said bore, at least at the liared ends thereof, being composed of a non-abrasive material having a high eot 7 efficient of friction with the textile lament, and ythe diameter of said bore exceeding the diameter of said filament, whereby a plurality of turns of false twist is imparted to the filament for each revolution of said rotatable member.

2. Apparatus as dened in claim 1, wherein said rotatable member is mounted on a txed annular member 'by means of an anti-friction bearing.

3. Apparatus as detinedrin claim 1, wherein the interior surface of said bore comprises a bush composed of natural rubber with carbon black ller.

4. Apparatus for imparting false twist to textile ilaments comprising a sequential arrangement of filament lsupply means, tensioning means, heating means, twisttube and guide means, said twist-tube including a rotatable member having an axial bore with outwardly `flared ends extending therethrough, the interior surface of said bore, at 'least the flared ends thereof, being composed of a non-abrasive material having a high coef.- cient of friction with the textile filament, and the diameter of said bore exceeding the diameter of said lilament, whereby a plurality of turns of false twist is im,- parted to the iilamentvfo'r each revolution of said roe tatable member, the axis of said rotatable member being angulated with respect to the lament path from `said heating means to said twist-tube and the lament path from said twist-tube to said guide means.

References Cited in the le of this patent UNITED STATES PATENTS 2,475,922 Stockly July 12, 1949 2,753,679 Von Schmoller et al. 7...- July 10, 1956 2,823,513 Vandamme et al. Feb. V18, 1958 FOREIGN Y PATENTS 154,341 Austria Sept. 26, 1938 440,546 Italy Oct. 13, 1948 (Addition to Patent 399,231) 472,583 France Aug. 11, 1914 496,585 Great Britain Dec. 2, 1938 500,823 Great Britain Feb. 16, 1939

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