False twisting device
I United States Patent 1 1 1111 3,879,927  
 Bueb et al. Apr. 29, 1975 FALSE TWlSTlNG DEVICE 3.535.866 10/1970 Tsuruta et al 57/774 x 3,537,250 ll/l970 Mackintosh 57/774 [751 lnvcmms OPlddenr Karma: 3,670,488 6/1972 Richter 57/774 &#34;8&#34; Smbergl Edgar 5.740.939 5/1973 Nevcuk.... 57/7745 Muschelknautz, usen; 3,745,755 7/1973 Kcto 57/77 4 Wolfgang Rellensmann, Zons u. Neuss, all of Germany Primarv Examiner-Donald E. Watkins 73 A B Akt ll h ft, i 1 sslgnee zzg r g g i Arlorney, Agent, or Frrm-Plumley &amp; Tyner [22] Filed: Mar. 20, I974 [21] Appl. No.; 452,928 ABSTRACT pp Priority Data The invention is related to a false twister for the pro- Mar. 20. 1973 Germany 23l3723 duction of synthetic textured or stretch-type yarns or filaments, consisting of two or more successive inter- [52] U.S. Cl 57/77.4; 57/156 nal friction twisters, wherein the inlet-end friction sur- [5] Int. Cl. D02g l/04 faces of the internal friction twister mouthpieces have [58] Field of Search 57/77.3-77.45, a high coefficient of friction whilst the friction sur- 57/156 faces of the outlet mouthpieces have a low coefficient of friction in relation to the friction surfaces at the [56] References Cited inlet end.  
  UNITED STATES PATENTS 3.066.473 lit/1962 Mucdu 57/774 8 Claims, 7 Drawing Figures PMENIEBAPRZSISYS 3,879,927  
 sum 1 of 3 FIG. I  
 FALSE TWISTING DEVICE This invention relates to a process and a false twister for the production of textured and/or stretch-type textile filaments or yarns.  
  In the so-called torsion process for texturing yarns or filaments consisting at least partly of thermoplastic material, the yarns or filaments are passed in twisted form through a heating zone and a cooling zone. The yarns or filaments are twisted for example by means of a false twister which follows the heating and cooling zone in the direction of travel of the yarn or filament, and which transmits to the filament a frictional force producing a torsional moment in the filament. Heating and subsequent cooling of the filament in its twisted form fixes a state of permanent deformation in the filament which is responsible for the characteristic properties of the filaments thus produced. In order to produce a filament of high quality, it is necessary on the one hand that the twister should produce a certain torsional moment governed for example by the material. denier and number of the individual capillaries and by quality features of the end product. On the other hand, the tension to which the filament is subjected as it passes through the twister should not be excessively increased so that the deformation fixed into the filament in the fixing zone is not eliminated or destroyed.  
  It is known that there are various technical possibilities for bringing a travelling filament into contact with friction surfaces of a twister to produce a torsional moment in the filament. For example, British Pat. No. 797.051 describes an arrangement in which the filament is drawn through a twist tube whose internal surfaces, which come into friction contact with the filament. consist of a material having a high friction coeffcient. in one preferred embodiment of this so-called internal friction twister for example. a mouthpiece consisting of a material having a high friction coefficient is fitted both to the inlet end and to the outlet end of the twist tube (in the direction of travel of the filament). German Offenlegungsschrift No. 2.123.618 describes a friction-type texturing arrangement comprising at least two twist tubes through which the filament is guided in such a way that a looping angle of at least about 360 is obtained, and which is distinguished by the fact that the friction inserts consist of a ceramic or a hard metal.  
  However, it has been found that. in the event of an increase in the rate of filament travel in internal friction twisters of this kind, not only is the torsional moment transmitted to the filament altered, the ratio between the tension prevailing in the filament on leaving the twister and the tension which had prevailed in the filament before entry into the twister is also increased. In view of this effect. a certain ratio has to be maintained between the rotational speed of the twister or the speed of the friction surfaces and the rate of filament travel to ensure that the tension prevailing in the filament on leaving the twister does not become excessive. If the filament tension ratio which is favourable to the particular filament and which. in general. is preferably low, is to be maintained. the rotational speed of the twister has to be increased accordingly. However. it is not possible in practice to increase the rotational speed of the twister arbitrarily because. technically, this becomes increasingly more difficult beyond certain rotational speeds. for example from the point of view of the service life of the ball bearings. controlling the centrifugal forces generated at the mouthpieces or avoiding a high noise level.  
  Accordingly. it is desirable to have a twister which transmits a sufficiently high torsional moment to the filament and, at the same time. produces little or no increase in filament tension, especially at high rates of filament travel and, in relative terms. low rotational speeds of the twister.  
  lnventions have been developed with a view to transmitting a torsional moment to the filament on the one hand and to accelerate rather than decelerate the filament as it passes through the twister on the other hand. German Offenlegungsschrift No. 2,040,749 describes a friction twister which consists of three externally mounted rings which are inclined relative to the direction of filament travel and along whose intern a] friction surfaces the filament travels. in addition, German Offenlegungsschrift No. 2,038,067 for example describes an arrangement in which the filament is guided over a specially shaped friction surface into a rotating twist box and. after changing direction over a guide roller. leaves the twister again through the inlet opening. Twisters which are designed to produce the favourable properties referred to above in this or a similar manner. are generally complicated. which applies in particular to those comprising several rotating components and shafts, or are unsatisfactory for example in regard to generation of the torsional moment.  
  The object of the present invention is to provide a twister which functions on the technically simple principle of internal friction twisting and which, in addition to generating a satisfactory torsional moment, guarantees a sufficiently low filament tension ratio, especially in cases where there is a low ratio between the rotational speed of the twister and the rate of filament travel.  
  According to the invention, there is provided a false twister for the production of synthetic textured or stretch-type yarns or filaments, consisting of two or more successive internal friction twisters. wherein the inlet-end friction surfaces of the internal friction twister mouthpieces l have a high coefficient of friction whilst the friction surfaces of the outlet mouthpieces 2 have a low coefficient of friction in relation to the friction surfaces at the inlet end.  
  According to the invention there is also provided a process for the simultaneous stretching and texturin g of synthetic filaments or yarns using internal friction twisters. wherein the filament or yarn, after passing through a heating and a cooling zone. in which it is also stretched. is guided through two or more internal friction twisters and a high torsional moment in relation to the negligibly low torsional moment applied at the outlet end is imparted to the filament or yarn by the inletend friction surfaces of the twister mouthpieces.  
  The friction coefficient of the friction surfaces at the inlet end should preferably be between 0.4 and 0.7. depending upon the material to be textured. Friction coefficients at the inlet end between 0.5 and 0.6 have proved to be particularly favourable. The friction coefficient of the mouthpieces at the outlet end should be as low as possible. preferably less than 0.3.  
  In a simple internal friction twist tube. as shown in FIG. 1. an inlet end mouthpiece l and an outlet end mouthpiece 2 are arranged in a twist tube 3 which is driven, for example. by means of a drive belt 4. The filament 5 is drawn through the twist tube in the manner illustrated in FIG. I. A torsional moment is generated in the filament through its frictional contact with the rotating mouthpieces 1 and 2. The inlet end and outlet end looping angles (b1 and 422 may be between 45 and 90, for example, according to requirements. It has been found that the ratio between the tension prevailing in the filament on leaving the twist tube and the tension which had prevailed in the filament before entry into the twist tube is substantially reduced if the mouthpiece 2 at the outlet end has a lower coefficient of friction than the mouthpiece l at the inlet end. Unfortunately, the torsional moment transmitted from the twist tube to the filament also decreases with a mouthpiece combination such as this. However, if after leaving the twist tube the filament is guided through a second twist tube similarly equipped with different mouthpieces, it is surprisingly found that, on the one hand, there is still a low ratio between the filament tensions after and before this double twister whilst, on the other hand, a sufficiently high torsional moment is generated.  
  In one embodiment of a twister according to the invention as illustrated in FIG. 2, the filament 5 initially passes over an inlet mouthpiece 1 having a high coefficient of friction and then over an outlet mouthpiece 2 having as low a friction coefficient as possible (for example polished steel or ceramic). In the embodiment illustrated in FIG. 2 with two successive twist tubes, the filament again passes over a second inlet mouthpiece I having a high coefficient of friction and over a second outlet mouthpiece 2 having as low a coefficient of friction as possible. The outlet mouthpieces 2 can be regarded as substantially frictionless guides by which the twisted filament is brought from a preceding into a following twist tube.  
  Naturally the invention also includes filament guides in which the filament is guided twice through the same twist tube. In an arrangement of, for example, two twist tubes of the kind shown in FIG. 2a, the filament first of all passes through the first twist tube, then through the second twist tube and finally back through the first twist tube, in cases where this procedure is adopted.  
  Instead of being guided over a smooth outlet mouthpiece, the filament can also be guided over a filament guide, preferably in the form of a roller 6, at the outlet end of the twist tube, as shown in FIGS. 3, 4 and 4a, in order to avoid contact between the filament and the twist tube at the outlet end. In order to enhance the filament-transporting effect of the mouthpiece at the inlet end, the guide roller 6 is arranged in such a way, in a preferred embodiment illustrated in FIGS. 4 and 40, that the filament is only slightly deflected from its path, as seen in a vertical projection on to the inlet mouthpiece. The distance d amounts to about (0.2 0.8) R,. The distance e is derived from the need for the filament to be guided close to, but without touching, the outlet edge of the twist tube.  
  Accordingly, another preferred embodiment of the invention is a false twister consisting of two or more successive internal friction twisters, distinguished by the fact that the internal friction twister mouthpieces 2 are missing from the outlet end and are replaced by filament guide elements known per se, preferably in the form of rollers.  
  In order to enhance the filament-transporting effect of a twister of this kind which is only effective at the inlet end, it is possible according to another aspect of the invention to increase the size of the mouthpieces to such an extent that an optimum ratio exists between torque generation, filament tension ratio and the uniformity with which the frictional force is transmitted.  
  In a conventional mouthpiece, the characteristic radii R,- and R are, for example, between 10 and 15 mm and between 20 and 30 mm, respectively, whereas with an enlarged mouthpiece they may be, for example, between 20 and 30 mm and between 40 and mm, respectively. The radius of curvature r may be, for example, between 5 and 10 mm. The significance of the radii R,, R, and r can be seen from FIGS. 4 and 4a. The advantage of increasing the geometry of the mouthpiece is that the surface speeds are increased by the increase factor. It has also surprisingly been found in practice that, by increasing the size of the mouthpieces, it is also possible to enhance the transporting effect of the inlet mouthpiece.  
  Accordingly, the invention also relates to a false twister consisting of two or more successive internal friction twisters acting at the inlet end, distinguished by the fact that the radii R, and R amount to between 20 and 30 mm and to between 40 and 60 mm, respectively.  
  The advantages afforded by the invention are in par ticular the fact that, by arranging one behind the other, two or more internal friction twist tubes whose inlet and outlet friction surfaces have been modified in re gard to their friction coefficient in accordance with the invention, it is possible to obtain a twister which, whilst producing the same torsional moment, has a lower filament tension ratio than a conventional internal friction twist tube with two mouthpieces having the same coefficients of friction.  
  By means of the specific arrangement of modified twist tubes one after the other, torsional moment and filament tension ratio can be adapted within wide limits to meet the requirements of a particular filament and process, in particular, by the use of a modular system.  
  The invention is described in more detail in the following with reference to the accompanying drawings, wherein:  
  FIG. I shows a conventional internal friction twist tube with two identical mouthpieces.  
  FIG. 2 shows one embodiment of a false twister according to the invention.  
  FIG. 2a shows a second embodiment of the false twister according to the invention.  
  FIG. 3 shows a third embodiment of the false twister according to the invention.  
  FIG. 4 shows the path followed by the filament through a twist tube in accordance with the invention having staggered outlet rollers.  
  FIG. 5 illustrates a texturing process using a false twister according to the invention (simultaneous stretching and texturing).  
  According to FIG. 5, a filament coming from a bobbin 7 travels through delivery rollers 8 and passes over a heater 9. The filament then travels through two successive internal friction twisters I0 and 11, is continuously stretched by the stretching godet l2 and 1S wound into a package by means of the winding unit 13, optionally after passing through a second heatlng zone and following the application of a preparation.  
  The invention also relates to a process for the slmultaneous stretching and texturing of synthetic filaments and yarns using internal friction twisters and a heatfixing zone, distinguished by the fact that. after passing through the heat-fixing zone, in which it is also stretched, the filament or yarn is guided through two or more internal friction twisters, and a high torsional moment in relation to the negligibly low torsional moment applied at the outlet end is imparted to the filament or yarn by the inlet end friction surfaces of the twister mouthpieces.  
  The process is suitable for texturing yarns consisting at least partly of thermoplastic material. It is preferred to use yarns of polyamides, such as polyamide-6 and polyamide-6,6, or yarns of polyesters, such as polyethylene terephthalate.  
  The following Example is to further illustrate the invention without limiting it.  
 EXAMPLE A polyamide yarn (polyamide-6 of dtex 22/3) is stretched by stretching rollers in a ratio of l 3.3 and is introduced at a temperature of [65C through a heated zone into the false twister according to the invention illustrated in FIG. 4 at a rate of 700 metres per minute. The twist tube is rotated at 18,000 rpm. The mouthpieces have an internal radius of mm and an external radius of 45 mm. The inlet mouthpieces are made of Vulkollan 70 Shore, and the outlet mouthpieces of polished steel. The textured filament thus produced has a coldwater shrinkage of 30 to 50 percent. If a yarn of the same quality were to be twisted with a simple, conventional twist tube equipped with two normal Vulkollan mouthpieces, the twist tube would have to rotate at around 25,000 r.p.m.. Thus, by using the twister according to the invention, the rotational speed of the twist tubes can be reduced by 28.6 percent, which is desirable from the operational point of view.  
 We claim:  
  1. A false twister for the production of synthetic textured or stretch-type yarns or filaments, consisting of two or more successive internal friction twisters, wherein the inlet-end friction surfaces of the internal friction twister mouthpieces (l have a high coefficient of friction whilst the friction surfaces of the outlet mouthpieces (2) have a low coefficient of friction in relation to the friction surfaces at the inlet end.  
  2. A false twister as claimed in claim I, wherein the inlet-end friction surfaces of the internal friction twister mouthpieces have a friction coefficient of 0.4 to 0.7.  
  3. A false twister as claimed in claim 2, wherein the inlet-end friction surfaces of the internal friction twister mouthpieces have a friction coefficient of 0.5 to 0.6.  
  4. A false twister as claimed in claim 1, wherein the friction coefficient of the mouthpiece at the outlet end is less than 0.3.  
  5. A false twister as claimed in claim 1, wherein the internal friction twister mouthpieces (2) are missing at the outlet end and are replaced in their function as filament guides by filament guide elements known per se.  
  6. A false twister as claimed in claim 5, wherein a roller (6) is used as the filament guide element.  
  7. A false twister as claimed in claim 1, wherein the radii R, and R, of the twister mouthpieces amount to between 20 and 30 mm and to between 40 and 60 mm, respectively.  
  8. A process for the simultaneous stretching and texturing of synthetic filaments or yarns using internal friction twisters, wherein the filament or yarn, after passing through a heating and a cooling zone, in which it is also stretched, is guided through two or more internal friction twisters and a high torsional moment in relation to the negligibly low torsional moment applied at the outlet end is imparted to the filament or yarn by the inletend friction surfaces of the twister mouthpieces.