GB955424A - A continuous process and apparatus for stretching travelling filaments of fully synthetic thermoplastic organic polymers - Google Patents

Abstract

955,424. Artificial filaments stretching apparatus. FARBENFABRIKEN BAYER A.G. July 22, 1960 [July 23, 1959], No. 25651/60. Heading B5B. Travelling filaments of synthetic thermoplastic organic linear polymers are stretched by drawing, by means of one or more godet wheels, a filament (or bundle of filaments) from one or more godet wheels in opposition to an adjustable braking force, which force is automatically maintained constant at the godet wheel(s) so that the tension in the filament is maintained constant while it is travelling through the stretching zone, the peripheral speed of the draw godet wheel(s) being constant and higher than that of the feed godet wheel(s). As shown in Fig. 4, a godet 4 round which travels a filament 1 from a bobbin 2 is mounted on a shaft 12 connected to the gear-wheels of a gear pump 13 which pumps oil from a flexible pipe 14 through a hollow shaft 15 and a torsion capillary 16 and pipe 18 into a storage tank 19 from which it is withdrawn through pipe 14. The end of the torsion capillary 16 which is attached to the casing of the pump 13 is rotated relatively to the end of the capillary 16 which is attached to the stationary member 17 by means of a weight 21 which is suspended from the periphery of the casing of the pump 13 by a strap and consequently tends to rotate the pump casing and twist the capillary 16 into a spiral, thereby reducing the cross-section of the capillary 16. The torque which the filament 1 exerts on the godet 4 rotates the complete system against the torque exerted by the weight 21 until the resistance to the flow of oil through the torsion capillary 16 and thus the torque at the gear pump has become so large that the tension in the filament 1 and the torque exercised by the weight 21 are in equilibrium. As shown in Fig. 5, the torsion capillary 16 is clamped at one end in the portion 22 of the pump housing which is mounted on ball bearings 22 so as to be pivotable about its axis, and at the other end in the fixed support member 17 which is provided with a duct communicating with the capillary and with the pipe 18 leading to the oil storage tank 19. As shown in Fig. 6, a gear pump 13 within a housing 22 circulates oil from the reservoir 19, through the flexible feed pipe 14, valve 23, 24, flexible tube 28 and pipe 18 back to the reservoir 19. The valve member 23 is internally threaded and engages the threaded end of the valve spindle 25 the other end portion 26 of which is squared and is a sliding fit in a corresponding recess in the support member 17. A weight 21 attached by means of a strap to the pump housing 22 rotates the latter in the ball bearings 29 in such a direction that the valve member 23 is moved axially towards the valve seat 24 and the valve thus partially closed. The torque exerted by the filament on the feed godet 4 acts against the weight and tends to open the valve. The oil brakes shown in Figs. 4 to 6 are suitable for high filament tensions and slow spinning speeds. For stretching low denier filaments it is advantageous to use an electric eddy current brake as shown in Fig. 7, wherein a filament 1 is guided over a godet 4 mounted on a shaft supported in a bearing 30 and carrying at its other end a disc 31 of aluminium or copper. Arranged to be rotatable and also axially displaceable in a threaded pedestal 33 is a soft-iron disc 32 opposite disc 31 carrying four permanent magnets 34, each pair of which are opposite one another as North and South poles. Rotation of the godet 4 by the filament 1 and consequent rotation of the disc 31 induces electric currents in the disc 32 and the magnets 34 exert a braking torque on the disc 31 and also a counteracting torque on the disc 32. This torque is balanced by the opposing torque exerted on the disc 32 by a weight 37 suspended from the periphery of a disc 35 by means of a strap 36 so that, as the disc 32 is rotated, it is simultaneously displaced to increase the air gap between the magnets and the disc 31, so that the torque on the disc 31 is reduced. As shown in Fig. 8, a draw godet 38 corresponding to the godet 4 is mounted on a shaft 39 which is connected to the sun wheel 40 of a differential gear which is driven by a gear 41 through gear-wheels 42 and 43. Mounted on the gear-wheel 43 is a bevel gear 44 which meshes with the sun wheel 40 of the differential gear. A second bevel gear 45 of the differential gear is connected to a brake device corresponding to that shown in Fig. 6. If the brake device is locked, the godet 38 is rotated by direct drive. Contrariwise, if the brake is released, it starts to rotate until the torque at the bevel gear 45 is equal to the torque on the shaft 39 produced by the drawing of the filament by the godet 38. The invention enables stretched filaments of more uniform denier to be produced.