Patent GB-414221-A (GB)
Title: Improved method and apparatus for rolling
IPC: B21B37/54
Filed: 1933-07-31
Abstract: 414,221. Rolling. McBAIN, W. C., 1054, Mahoning Avenue, Youngstown, Ohio, U.S.A. July 31, 1933, No. 21505. Convention date, Aug. 15, 1932. [Class 83 (iv).] A strip of metal 7 is passed through rolls 11 and back again as often as desired, being wound and unwound on reels 14 and 14<1>, a pulling tension and a drag tension being imposed by the reel motors, the energy of the drag tension being used to cause its motor to generate, and help the system. Several arrangements are described in which the working rolls may be idle or driven. In Fig. 1, a synchronous motor 35 driven from mains 37 drives generators 33, 30 and 36, the generator 33 supplying current to drive a motor 28 coupled by clutches 21, 21<1> and gearing 20, 17, 16 to drive or brake the reel 14 or 14<1>. The reels are also driven by motor 19 or 19<1> supplied with current from the constant current generator 30. When braking the strip the separately excited fields 22 or 22<1> of these motors causes them to act as a generator. The exciter generator 36 supplies the field 22 of the motor 19, through a rheostat 23 automatically moved to compensate for the increasing torque on the reel 14 as it coils up the strip and increases in diameter as follows :-a bell crank feeler 25 is moved by increasing diameter to pull on a weighted cable 26 which rotates a pulley 24 on the spindle of the rheostat 23 to adjust it to give constant tension on the strip. The handwheel 38 acting on rheostats 39 and 40 is set to give the required speed of the mill which is indicated by the tachometer voltmeter 49. The handwheel 41 acting on rheostats 42, 43 and 44 is set to give the required back tension as shown on the ammeter 50. The last part of the rheostat 42 gives a reverse current to the field 31 of the generator 30 to negative the residual field when 19 is to be stopped. Handwheel 45 operates a controller switch 46 to cut out the back tension. In operation, to load the mill with a strip, the end 7<1> of a coiled strip on rollers 79 in a box 78 is threaded through the mill from the right to the reel 14. The motor 19 is cut out by the handwheel 45. The reel 14 is rotated slightly by moving the control 41 so that the strip 7 can be attached thereto, the pass of the rolls 11 are adjusted. The clutch 21 is engaged and clutch 211 disengaged so that the motor 28 assists the permanently coupled motor 19 to drive the reel 14, on operating the handwheels 38 and 41 to control the speed of the motor 19. After coiling on the reel 14 the free end of the strip is attached to the reel 141, ready for pulling the strip back from left to right. This is done by hand operating the control 45 to 46 to utilize motor 19 as a brake and generator and motor 191 as a tensioner. Clutch 21 is disengaged and clutch 21<1> engaged. The tension is now controlled by rotating clockwise the handwheel 41 (while the speed control handwheel 38 remains neutral) thus connecting field 31 of the generator 30 to the exciter 36 through the rheostat 42. Generator 30 driven by motor 35 supplies current to machines 19, 191, the fields 22, 221 of which are in parallel across the exciter 36 and have rheostat 23 or 23<1> in series with them. Rheostat 23 is in the position of minimum resistance to provide maximum retarding torque on the shaft 15 while the reel 14 is full, and rheostat 23<1> similarly gives minimum torque to the shaft 15 of the empty reel 141. The required strip tension is obtained from the rheostat 42 which controls the excitation of the generator 30 supplying current to the reel motors 19, 19<1>. The extra speed of the motor 19<1> over the motor 19 gives an E.M.F. to energize the field 32 of the generator 30 and so assists in giving it a constant-current characteristic. Strip tension having been adjusted, the speed controller 38 is rotated clockwise so that generator 33 supplies current to the motor 28 to pull the strip from left to right through the mill. When the strip starts to move, the machines 19, 19<1> start to rotate, exercising equal and opposite torques, but 19 being driven against the torque acts as a generator in series with the generator 30 and its output is thus absorbed by 191 acting as a motor, since it turns in the direction of its torque. The generator 30 thus supplies only the extra current required to maintain the desired strip tension, its two fields 31 and 32 being controlled by the handwheel 41 and its rheostats.