Patent GB-600438-A (GB)
Title: Improvements in and relating to electric billet heating machines
IPC: C21D1/40
Filed: 1945-11-16
Abstract: 600,438. Control systems for consumption apparatus. ENGLISH ELECTRIC CO., Ltd., and BARLOW, K. F. Nov. 16, 1945, No. 30795. [Class 38 (iv)] In an electric billet heating machine, the final temperature of the billet is controlled by means responsive to the total energy applied to the billet. A rotating disc type I<SP>2</SP>t integrating meter 9 is energized through a variable ratio transformer 11, from a current transformer 10 in the primary circuit of a main transformer 4 supplying the electrode heating circuit for the billet 1 and when so energized, drives a cam 12 co-operating with an armature 13 which co-operates with fixed contacts 15, 16. With contacts 24a, 24b, 24c of switch 24 in the automatic position as shown, a relay coil 27, controlling contacts 27a, 27b, 27c, 27d is energized independently of start and stop switches 25, 26 respectively. Closure of start switch 26 energizes a lifting coil 17 for the armature 13 which completes a circuit for relay coil 18, the contacts 18a of which close to energize coil 7a of the contactor 7 which closes to complete the heating circuit from A.C. supply mains 5 to the electrodes 2, 3, coil 27 now being energized over a holding contact 27b and fixed contact 16. Subsequent to the operation of switch 26, armature 13 is maintained in contact with the contact 16 by the cam 12, which, after a predetermined amount of energy, depending upon the setting of autotransformer 11, has been applied to the billet, completes one revolution to allow the armature to fall back into the slot 12a, thereby deenergizing relay 18 to terminate the heating cycle and releasing a ram 22 operating in cylinder 23 and under the control of electromagnetic air valve 21 which is controlled by the coil 21a through interlocking contact 7b of contactor 7 and contact 18b of relay 18. Operation of stop switch 25 before completion of the heating cycle, de-energizes relays 27 and 18 and the former connects (a) a resetting transformer 28 to supply mains 14, (b) the meter 9 to the secondary 28b of the said transformer, and (c) short-circuits the auto-transformer 11. The meter continues to operate until cam 12 reaches the position where the armature 13 falls into the slot 12a. With switch 24 in the " manual " position, relay 18 is energized directly through the start and stop switches 25, 26 and contact 24a ; contact 24b maintains a holding circuit for relay 18, whilst contact 24c de-energizes relay 27 to effect the connections at (a), (b) and (c) above. Electrode current may be controlled during the heating process by means of an additional cam 30 which is effective either to short-circuit an impedance 33 in the primary circuit of the main transformer or vary the setting of a main tapchanging transformer 6. Modifications may include dispensing with the auto-transformer 11 and the transformer 10 may be replaced by one having a variable ratio. Alternatively, the meter 9 may be supplied from a fixed ratio transformer having a tapped winding therein to provide adjustment for different I<SP>2</SP>t values or the meter may be supplied from a shunt, the adjustment of final temperature being obtained by tappings on the shunt or by a variable impedance in the meter circuit. Specifications 595,585 and 600,436, [both in Group XI], are referred to.