Patent GB-815665-A (GB)
Title: Improvements in or relating to electric control systems for rolling mills
IPC: B65H23/198
Filed: 1956-12-31
Abstract: 815,665. Automatic control systems for rolling mills. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Dec. 31, 1956 [Jan. 6, 1956], No. 39620/56. Class 38 (4). [Also in Group XXXVII] Relates to a cold reduction mill in which metal strip is unwound from a reel adapted to be coupled to two electric motors, the motor OM being clutched directly to the motor IM which is, in turn, coupled to the reel through reduction gearing. As shown, the motor IM returns current alone to the generator G, the motor OM being disconnected but having its armature still coupled to the reel. To maintain the strip tension constant between the reel and mill, the back E.M.F. of the reel motor is regulated in proportion to mill speed, and the motor current is controlled in proportion to the tension desired. The back E.M.F. regulation is effected by magnetic amplifier IMA which controls a pilot motor RM driving rheostats RI, RDR. A voltage representative of mill speed is applied to draft compensation rheostat DCR which is connected to pattern winding TP. A coil RMV, energized in response to the back E.M.F. of the reel motor, opposes the winding TP. An IR signal winding aids the winding RMV, and a bias winding TB aids the winding TP. As the metal leaves the reel, the speed of the motor IM increases and motor RM is operated to reduce the field excitation of the reel motor. The reel motor current is controlled by means of magnetic amplifier 2MA acting on the field winding CF of the generator G. The amplifier 2MA has an anti-hunt winding AH interconnected through a resistor-capacitor circuit across generator field winding RF. Control winding C is energized in accordance with the motor current, and the speed signal winding S is responsive to the mill speed, the switch UE being closed when the motor IM is disconnected to re-calibrate the effect of winding S for such change of operation. Winding B provides a fixed adjusted effect, whilst winding Pat is connected across tension-adjusting rheostat TAR. The windings B, Pat are opposed by windings S, C, AH, an inertia compensation winding IC being effective to cause the magnetic amplifier to operate over its entire output range. The energizing circuit for the winding IC comprises draft compensation rheostat 2 DAR, gear ratio adjusting potentiometer 38, and strip width adjusting rheostat SWR. Reel diameter rheostat RDR is ganged to the motor-operated rheostat RI, and, since motor IM alone is effective, switch DIM is closed. Switch UX effects a compensation as a function of the number of armatures coupled to the drive. The magnetic amplifier 2MA may be replaced by amplifying machines comprising an exciter for the generator field winding, and a sub-exciter having windings corresponding to the control windings of the magnetic amplifier, Fig. 9 (not shown). Other arrangements for providing hold-back tension of the material being unwound from the reel are referred to. Thus, four motors may be connected selectively to the generator with variable ratio gearing and clutches between each motor and the reel, Fig. 10 (not shown). In another fourmotor arrangement, the motors are divided into pairs and a clutch and transmission gear are associated with each pair, Fig. 11 (not shown).