GB543421A - Improvements in or relating to apparatus for reducing the cross-sectional area of elongated metal bodies - Google Patents

Abstract

543,421. Automatic control systems. STEVENS, A. H. (Stringfellow, H. A.). March 14, 1940, No. 4815. Addition to 517,035. [Class 38 (iv)] [Also in Groups XXII and XXXVII] The reduction of line, strip &c. under tension as described in the parent Specification is effected under the control of means stated to maintain a substantially fixed ratio between the forward and back pulls applied by the winding reels. The invention is described with reference to the cold rolling of strip. The strip passes from the reel 4 under a fixed roller 5 over rollers 10 mounted in a cradle 9, and under second roller 5 to the winding up reel 3. Between the rollers 10 the strip passes in a plane between the reducing rolls 2 which may be idle and need not be so small that backing up rolls are necessary. Between the reels 3, 4 and the rollers 5 the varying inclination of the strip due to change in the effective reel diameter acts on arms carrying rollers 6 and controlling rheostats 32, 39. The cradle 9 is supported by arms 11 locking on plane surfaces 12, 13 on a base and 14 (Fig. 6) on the cradle. Toothed racks 15 and segments 16 prevent slip. Springs 17 engage the mill housing to counteract the unbalanced weight of the rockers when out of the central position. A rack 18 carried by the cradle engages a sector controlling the movable arms 41, 41a of rheostats 42, 42a in a housing 45 rotatable for further control by gearing driven by a reversing motor 46 under the control of contacts 47 to 51, the contact 47 being carried by the cradle. Switches 44 are set according to the direction in which the strip is passing through the mill. The motors are compound wound and when driving the reel for winding up the shunt coil 23 is in circuit and the coil 24 out of circuit. The motor characteristic is such that the series coil 22 predominates causing the pull on the strip and the rate of travel thereof to remain substantially constant notwithstanding the increasing effective diameter of the reel. The rheostats associated with the driving motor are inoperative. The reel from which the strip is unwinding is braked dynamically by its motor the field coil 23 being out and the coil 24 in. The coil 24 is in series with the rheostats 39 and 42 and the rheostat 32 is connected across the armature. As the coil decreases in diameter the theostats 32 and 39 under the armpit of the roller 6 decrease the current on winding 24 and at the same time increase the amount of current shunted at 30 from the armature. Should the tension on the delivery side of the rolls become too great the horizontal component acting on the cradle due to the inclination of the strip between the rollers 10 and 5 will cause the cradle to move to the left in Fig. 1 and the arm 41 is moved to cut out resistance from the circuit of the winding 24 and increase the retarding effect. At the same time owing to the change on the pull of the strip, tension is relieved on the delivery side of the rolls and increases on the supply side. On starting up the reel 3 the cradle moves to the left till the contacts 47 and 48 close starting the motor 46 to cause a reduction of the braking effect till the parts take up position to give the desired ratio between the tensions. After this the contact 47 floats between the contacts 48 and 49 during normal operation the motor 46 then only coming into operation to prevent increased movement of the cradle in one direction or the other. The tension ratio is adjusted by a right and left hand screws 58, Fig. 8, that causes the distance between the contact 48 and 50. Screws 59 and 60 adjust the contacts 49 and 51 to control the amount of float permitted before the motor 46 comes into operation.