GB1136726A - Improvements in or relating to the collection of synthetic polymeric yarns or filaments - Google Patents

Abstract

1,136,726. Driving spindles and rollers; builder motions. IMPERIAL CHEMICAL INDUSTRIES Ltd. 19 Sept., 1966 [1 Oct., 1965], No. 41758/65. Heading D1D. [Also in Division G3] In apparatus for winding packages over-end, particularly in draw-twisting synthetic polymeric filaments, in which the material is fed to the spindles, which may be of the ring or cap type, from a processing roller or rollers, e.g. a single roller, a roller with a separator roller, or a pair of nip rollers, and the spindles and roller(s) are driven independently from or by separate motors, programming means are provided positively to control the winding operation at least during the slow-down period, the means including a servo-device for controlling the spindle-motor, and tachogenerators to monitor the speeds of the spindles and rollers and produce signals which are compared during the slow down period to feed a resultant signal to the servo-device. Braking means associated with the programming means apply first a light restraint and finally a complete restraint to the spindles as the rollers come to a stop. The invention aims at maintaining a constant balloon tension during all stages of the wind, thereby preventing breaks, streaks and loops, and unstable packages and ensuring that each package contains the standard weight of perfect yarn. In a preferred form, filament from a cheese 3, Fig. 1, is guided at 7, 9, 11 and 13 to the nip of forwarding rollers 15, 15'; it then travels over a snubbing-pin 17 (from which point onwards the yarn is stretched), driven drawroller 19 and inclined separator 21, to be taken up on a ring-spindle at 29. There may be several drawing-zones, and zones where the yarn is relaxed or given other treatment. Reversals of the ring-rail are brought about as a plate 37 reciprocating with the rail strikes microswitches. The positions of the microswitches are controlled by cams on a shaft rotating at constant speed. The feed and draw rollers are driven by an A.C. induction motor, and the spindles by a D.C. motor. Start-up period. A manually adjustable timer is provided to ensure that the spindles start before the draw-rollers, so that the necessary balloon-tension is achieved when the rollers start. It is arranged that the traveller speed attains a maximum when the rollers start, to fall to a minimum acceptable value when the rollers reach maximum speed; also, the spindles attain maximum speed when the rollers reach theirs. The period before the rollers reach maximum is kept to a minimum to keep the wash bunch as small as possible. Main wind During this period the drawrolls are driven at constant speed, and a stable balloon is maintained by reducing the spindle speed so that the ratio of the square of the traveller speed to the package-diameter is at all times constant. The desired spindle-speed programme is represented by the profile of a cam, Fig. 3, mounted to rotate, at constant speed, with the traverse-cam. The profiled cam acts on the slider of a linear potentiometer to produce a reference signal which is compared with the signals from a tacho-generator driven by the D.C. spindle-motor in a reference error unit. The error signal from this is fed to the pre-amplifier of a servo-device which changes the current fed to the D.C. motor. The servo-device comprises, in addition to the pre-amplifier, a three-phase magnetic amplifier, of which the input comes from the pre-amplifier, and the output comprises the voltage for the D.C. motor armature, the shunt field exciting circuit for the motor being derived from a rectifier across one phase of the power supply to the device. The cam may additionally vary the spindle-speed cyclically throughout the wind to "scramble" the lay; it may also abruptly increase the spindle-speed at certain times to prevent "patterning". The range of the potentiometer may be controlled by a rotary potentiometer at each of its ends. Slow-down period, first stage The A.C. motor is switched off, and the roller speed allowed to decay normally, while a controlled relationship is maintained between the speeds of the spindles and rollers. When the cam initiates the slow-down procedure, it disconnects the potentiometer from, and connects a second tachogenerator to, the reference error unit. This tacho-generator monitors the speed of the rollers, and its signal is compounded with an additional one which ensures that the spindle-speed exceeds a value which would ensure the formation of a stable balloon with the draw-rolls stopped. The composite signal is compared with the signal from the first tacho-generator. The additional signal is produced from a further ("traveller-speed") potentiometer placed by the cam across the first tacho-generator. The resultant signal from the reference unit is fed back to the D.C. spindlemotor. Brakes are applied to the spindles, lightly enough for the spindles to continue to be rotated slowly, the D.C. motor current being enough to prevent the motor hunting. A third ("change-over speed") potentiometer across the second tacho-generator ensures that the spindles slow down smoothly. Slow-down period (second stage). When a zero-speed sensing device coupled to the second tacho-generator senses that the rollers have stopped, it causes the brakes to be fully applied, and, through being coupled to the servodevice, de-energizes the D.C. spindle motor. A second variable timer ensures that the ring- rail is not stopped until the elapse of a predetermined time after the rollers are stopped, to ensure the winding of a slow-down bunch.