Patent GB-1535870-A (GB)
Title: Process and apparatus for false twist texturing of yarns
IPC: D02G1/08
Filed: 1976-06-11
Abstract: 1535870 False twisting HEBERLEIN MASCHINENFABRIK AG 11 June 1976 [16 June 1975 25 Feb 1976] 24279/76 Heading D1D A false twisting process comprises feeding yarn at a predetermined angle to a point on a cylindrical friction twist-imparting surface 3 rotating at a constant speed, directing the yarn from the point along a helical path whilst maintaining the angle α between the direction of movement of the surface 3 and the direction of movement of the yarn along the helical path at a constant value, the angle α being larger than the twist angle Ï imparted to the yarn while passing along the surface 3, withdrawing the twisted yarn from a second point on the twist-imparting surface 3 and registering and/or controlling the tension of the yarn being fed to the first point in relation to the tension of the yarn being withdrawn from the second point. As described, the yarn 7 is fed over tension sensing guide 9 to a rotating ribbed cylinder 1. The cylinder 1 is provided with radial thread guides 5 mounted on helical support 6, the guides being disposed radially in grooves 4 of the rotating cylinder 1. The rotation of the cylinder 1 urges the yarn against the guides 5 and thus causes the yarn to move in a fixed helical path around the cylinder 1. The yarn is withdrawn from the cylinder 1 and fed over tension sensing roller 12. The resultant forces of the tension in the yarn being fed to and from the rotating cylinder 1, as detected by guide 9 and roller 12, are indicated by pivoted pointer 15. Movement of thread guide 9 varies the angle of wrap around the cylinder 1 to keep the input and output yarn tensions constant. The initial angle of wrap of the thread around the cylinder can be varied by adjustment of the thread guide 9 relative to its mounting shaft 11. When the tension sensing pointer 15 is pressed against abutment 19 or 20 a safety device can stop the machine or illuminate a warning light. In an alternative embodiment, Fig. 3 (not shown) the tension of the yarn approaching and leaving the twist-imparting cylinder 1 is detected by thread guides 9, 17. The difference in tension detected is applied to a difference amplifier, Figs. 4 and 5 not shown which causes the thread guide 9 to move along and around the twist-imparting cylinder 1 so as to vary the angle of a wrap and thus the tension in the yarn so as to maintain the input and output tensions the same. The thread guide 9 is moved along and around the cylinder 1 by a servomotor (22) moving a screw threaded support (20) along the length of the cylinder, the thread guide rotating in a groove in the helical support 6 around the cylinder during its longitudinal movement. The thread tensioner, Fig. 4 (not shown), comprises a rod rotatable around a torsion spring (28) and carrying soft magnetic end (29) which operates in association with induction controlled resistances (30, 31) and permanent magnet (32). In operation, the two tension sensing devices 9, 17 feed signals to the difference amplifier (26) which controls servomotor (22) and the position of thread tension sensor 9 to maintain the thread tensions equal. If the thread tensions sent by sensors 9, 17 are very different, a control device may cut the yarn.