Patent GB-1154285-A (GB)
Title: Process and apparatus for the Crimping of Yarns
IPC: D02G1/00
Filed: 1968-03-28
Abstract: 1,154,285. Crimping of yarns. ELDIMA A.G. 28 March, 1968 [28 March, 1967], No. 15047/68. Heading B5B. [Also in Division D1] Apparatus for use in the crimping of a yarn consisting at least in part of a thermoplastic material, comprises two yarn forwarding devices (rollers 4, 8) which are spaced apart, a laser beam source 11 and a lens or lens system 13 capable of concentrating a laser beam 12 from the said source on to a yarn 1 passing between the yarn forwarding devices, the arrangement being such that in use the yarn may be passed between the two yarn forwarding devices through a laser beam (i.e. at point 10), whereby the yarn is heated to produce a temperature gradient across the yarn. Thus in Fig. 1, the starting yarn 1 is drawn off by rollers 4 from feed spool 2 via guide roller 3. A further pair of rollers 8 which rotates at a somewhat higher peripheral speed than the pair of rollers 4, moves the yarn 1 under tension over the two plates 5 and 6 which, with the aid of guide grooves 7, ensure an undisturbed movement of the yarn. Plate 5 suitably has a temperature of about 70 C. for preheating the yarn and the plate 6, the interior of which is provided with a cooling medium, serves to cool .the yarn. At point 10, one side of the yarn is heated by means of the laser beam 12 and wound up after passing the pair of rollers 8 in a tension-free state by means of a device (not shown). For an increased development of the crimp, the yarn can be subjected to a subsequent heat treatment by means of a device (not shown). The laser beam 12 is generated in laser 11 and concentrated in optical system 13 to impart the high energy density necessary to provide a steep temperature gradient at point 10, at which the beam impinges on textile yarn 1. The laser 11 radiates continuously and the beam 12 produces the heated zone over the whole length of yarn 1, as shown in Fig. 5. In Fig. 2, a pulsating laser beam 15 is generated by a variablefrequency modulator 14 which at point 10 produces heated zones 16 at intervals governed by the speed of the yarn and the frequency of the modulation. The heated zones are spaced apart in a longitudinal direction along the yarn, as shown in Fig. 6. In Fig. 3, the concentrated beam is moved to and fro over the yarn 1, transversely to the longitudinal axis of the yarn. The optical system 13 lying in the continuous beam 12 oscillates about the axis 11, oscillation being achieved by an electromagnetically excited oscillator (not shown) connected to the optical system 13. The back and forth movement of the beam is indicated by symbols 12<SP>1</SP> and 12<SP>11</SP>. In Fig. 4, yarn 1 is made to oscillate transversely to the continuous beam 12, this oscillating movement being produced by contact with a yarn guide 19 connected to an electromagnetically excited oscillator (not shown). The period or non-period pulsation or oscillation frequency of laser beam 12 and of yarn 1, as well as the speed of the forward movement of the latter, may be chosen so that the distance between the zones 16 and thus the crimp character of the yarn is as desired according to the end use envisaged for the yarn. In a further embodiment, the yarn can be rotated about its axis during the action of the laser beam. Thus, between the plate 6 and rollers 8, for example a false twisting device rotating at low speed of revolution can be mounted, by means of which a slight false twist is imparted to the yarn between roller pairs 4 and 8. Yarn 1 thus rotates at point 10 about its axis so that the continuously heated zone 9 or the discontinuously heated zones 16 extend in a helical path around the axis of the yarn. Yarns which may be crimped by processes according to the invention include both monofilament and multifilament yarns made either completely or partially of a thermoplastic material as for example a polyamide, e.g. polyhexamethylene adipamide, or condensates of #-aminocaproic acid or 11-aminoundecanoic acid, polyesters (e.g. polyethylene terephthalate, vinyl polymers (e.g. polyacrylonitrile), polyolefins and cellulose acetate. In general, the yarn is stretched and whilst in the stretched condition heated by the laser beam so that a temperature gradient is formed across the yarn, and after heating the yarn cooled with relaxation of tension, and if desired then subjected in the relaxed state to further heat treatment. Filaments may be so treated which have not been subjected to any, or only to partial, cold stretching for the purpose of molecular orientation, and then subsequently the remaining cold stretching is effected.