GB891979A - Constant gap control for sheet shearing lines - Google Patents

Abstract

891,979. Automatic speed-control systems. BLAW-KNOX CO. Oct. 6, 1960 [Nov. 4, 1959], No. 34291/60. Class 38 (4). [Also in Groups XXII and XXX] The speed of a conveyer 17 in a shearing line having means 12 for delivering strip S to a shear 15, is maintained automatically in excess of that of the delivery means 12 by means which respond to the speed of the delivering means 12 and to the cutting frequency of the shear 15 to maintain the gap G between adjacent severed sheets on the conveyer substantially equal to a predetermined value regardless of changes in the speed of the delivery means 12 and in the cutting frequency of the shear. The strip S from a reel C passes between rolls 10 to the straightener 12, which delivers the strip to the shear 15. A control 36 receives signals from tachometer generators 37-39 driven by rolls 14 engaging the strip, by the shear 15 and conveyer 17 respectively. Drives for the straightener 12 and the shear are by variablespeed motors 25, 27 controlled by regulators 26, 28, that for the conveyer 17 being by a variable-speed motor 30 energized by a variablevoltage generator 50 which may be driven by a constant-speed motor 51. The field 52 of generator 50 is energized by a magnetic amplifier 53 having windings 54-56 connected to tachometer generators 45-47 driven by the straightener 12, shear 15 and the conveyer respectively. The output winding 58 of the amplifier 53 is connected to the field 52 and to an A.C. source and a rectifier 59. Variable resistors or potentiometers 48, 59, 60 are included in the tachometer circuits. Operation.-The potentiometer 48 is adjusted so that no signal is delivered by the generator 46, and the opposing signals from generators 45, 47 are adjusted so that the conveyer 17 is driven at the same speed as the straightener 12 and there is no gap G between the sheets S<SP>1</SP>. A gap is introduced by setting the potentiometer 48, thus increasing the saturation of the core 57 and increasing the output of winding 58 which increases the speed of motor 30. The feedback signal from generator 47 opposes the signals from generators 45, 46 and brings the system to equilibrium when motor 30 has reached the speed giving the desired gap G, which will be maintained regardless of the speed of the straightener 12 and frequency of the shear. In a modification (Fig. 2, not shown), the amplifier is replaced by an Amplidyne &c. which is driven by a constant-speed motor.