Patent GB-514449-A (GB)
Title: Improvements in the control of electrically driven reversible rolling mills or the like for the treatment of strip material
IPC: B21B35/08
Filed: 1938-05-06
Abstract: 514,449. Control of motors. ENGLISH ELECTRIC CO.. Ltd., and CARNEGIE, H. S. May 6, 1938, No. 13560. [Class 38 (iii)] Travelling to predetermined limits. - An electrically-driven reversing roller mill equipment for cold strip or sheet material passed backwards and forwards through the mill from one reel to the other includes limit switches which stop the driving motor at the end of each pass, or operate indicators to show that this should be done manually, just before the material entering the rolls has reached the point at which it was stopped on the preceding pass in the same direction. In the figure the rolls 1 of a reversible rolling mill, suitable for rolling strip metal, are driven by an electric motor and the strip is coiled on reels 2 and 3 which are coupled to a dynamo-electric machines 4 and 5 respectively. For the direction of rotation shown, machine 5 acts as a coiling motor while machine 4 acts as a brake generator whereby the tension on the strip is maintained substantially constant in a known manner. A limit switch of the screw type is adapted to be clutched to each reel so that at the end of each pass either the rolling motor is stopped automatically or an indication, visible or audible, is given to the operator to enable him to stop the mill at the required point. The pass which is shown commencing is thus terminated by the engagement of nut 10 with switch 13 resulting from rotation of screw 8 which is clutched at 6 to reel 2, switch 12 serving to slow down the rolling motor before stopping. Only the limit switch which is coupled to the uncoiling reel is effective at the end of any pass so that rolling finishes substantially where it began at the commencement of the preceding pass notwithstanding the increased length of the strip. A disc or other type of limit switch may, alternatively, be used. Preliminary inching adjustments are described for inserting the strip into the mill from a reel A and for initially setting the limit switches and after these adjustments have been made clutches 6 and 7 are both engaged and the strip is passed backwards and forwards through the mill which rolls between the same limiting points on the strip at every pass. To prevent the rolls meeting the edge of a thick piece of metal at the end of a pass the mill may be stopped successively shorter at the end of each pass by racket devices 16 and 17 which influence the setting of the limit switches. The increasing length of travel of the nuts of the limit switches at each alternate pass may be utilized to operate a regulator to increase the speed of rolling progressively. The screwing down of the mill and restarting in the opposite direction may be initiated automatically by the limit switches or the control gear for the rolling motor. Known electric motor-driven screw-down means may be controlled by rotary switches or relays, actuated by the limit switches, and restarting is effected, automatically, each time the screwdown gear comes to rest. With the reels in the position shown in the Figure, switches 12 and 13, shown in the control circuit in the lower part of the figure, are closed and switch 15 is open. Closure of a manual control switch 40 energizes relay 42 to start the rolling motor in the right direction and the closing of auxiliary contacts 42a energizes relay 44 through closed switch 41 to bring the motor up to full speed. Near the end of the pass the opening of switch 12 slows down the motor and the opening of switch 13 finally stops it, open auxiliary contacts 42b serving to prevent operation of relay 43 meanwhile. The limit switch then starts up the screw-down gear which opens contacts 45 during operation. When the rolls have been screwed down to a predetermined point, the screw-down motor stops, contacts 45 reclose and the rolling motor restarts in the opposite direction. Starting, slowing and stopping may be effected on the Ward-Leonard system and if machines 4 and 5 are fed from the same generator they would be likewise controlled. Machines 4 and 5 have mechanical brakes which are held off electrically.while the machines are running. The setting of the limit switches after each pass may be effected by differential gear, dispensing with the clutch 6.