Patent GB-564210-A (GB)
Title: Improvements in, or relating to, appliances for use in electric flash welding
IPC: B23K11/24
Filed: 1943-03-06
Abstract: 564,210. Electric flash welding. TAYLOR, H. G., and SMITH, A. P. March 6, 1943, No. 3683. [Class 83 (iv)] In a flash. welding machine operated by a hydraulic ram controlled automatically by electrical means, the admission of pressure to the ends of the ram cylinder is controlled by a valve system operated by two solenoids, the current to which is controlled by the electric system. The opposite ends of the ram cylinder 6 are connected by pipes 32, 33 to a casing preferably containing two valves 9, 10, which are connected together by a lever 11 pivoted at 47 and which is operated by a pair of solenoids 12 and 13. The movement of the ram is effected by a minor pump 14 and a major pump 15, both driven continuously by electric motors and having a common tank 16 and pipes 19, 22, 25, the minor pump being used to reciprocate the movable workpiece slowly in the initial heating period and being electrically controlled by a device 31 during the flashing period so that the supply of hydraulic pressure is varied with the voltage across the welding faces, and the major pump being normally connected so as to return liquid to the tank 16 through the byepass 26 which is closed by an electricallycontrolled solenoid-operated valve 17 at the final movement of the ram to put on the welding pressure. A double-armed hand switch 40 is closed before welding is started by pressing -a push-button switch 41, which causes solenoid S1 to be energized through switch 5 and so closes switch P1. At the same time a solenoid S2 is energized and switch P2 closed so that S1 remains excited on release of push-button 41. P2 also puts in solenoid S3 through switch P3. Then solenoid S4 is energized through switches P8, 4 and P9 to close the switch P7 to energize solenoid 37 so that welding current switch 36 closes the circuit of the welding transformer. Switch P6 is also closed to close through switch P5 the circuit of the up solenoid 12 so that the ram moves forward. An adjustable solenoid S5 is energized when the parts touch through the secondary 43 of a transformer in lead 35 to switch 36 and a rectifier 44. Switch P10 is thus moved to the right and solenoid S6 is energized so that after a short interval occasioned by time-lag device 45, a switch P11 is closed so that a solenoid S7 is energized, switch P3 having been operated and solenoid S3 thus cut out by energizing of solenoid S6. Energizing of solenoid S7 opens the switch P12 and closes the switch P13. Cutting out of solenoid S3 also cuts out solenoid 12. When S6 is energized, a switch P14 is closed to keep S6 energized until P10 has gone over to the left. Thus rapid making and breaking of P3 is prevented. Closure of P13 connects solenoid 13 so that the ram moves back and welding current is broken. Current in secondary 43 is thus reduced and switch P10 returns to the left to render solenoid S6 inactive and thus solenoid S7 is de-energized so that P12 and P3 close to restore current to S3 and so also to solenoid 12 to move the ram forward again. After this has been repeated a number of times, the ram moving further forward at each reciprocation due to metal burning off the ends of the work, an arm on the ram engages and closes a switch 1 to close a circuit through the device 31 for rendering the action of the pump 14 sensitive to the voltage across the work faces, the action being that the supply of fluid is lessened when the voltage is low due to small resistance at the welding faces and increased when the voltage is higher. An arc between the faces is thus maintained constant for the flashing period. The ram then closes switch 2 to put in solenoid S3 independently of P3 and the ram continues to move forward, during flashing until it closes switch 3. Solenoid S8 is thus energized to close switch P15 which causes solenoid 18 to be energized so as to close byepass 26 by a valve 17 and allow the pump 15 to exert final heavy pressure on the ram which opens switch 4 to de-energize solenoid S4 and thus solenoid 37 to cut off the welding current. The ram continues to compress the weld until it opens switch 5 to cut off current to S1 after a time limit occasioned by time-lag device .42 so as to release switches to their starting positions. The valves may be moved by hand when desired by a lever 46 with a certain amount of free movement relatively to the lever 11 and mounted on the shaft 47. The lever has a projection 49 for normally closing the switch 50 in the control circuit during automatic operation and a depression 48 to engage a switch 51 which is normally open but when closed by the lever 46 closes an auxiliary circuit to solenoid S8 to keep the major pump operative during hand control of the ram. The automatic action of the apparatus may be stopped by pressing a switch 52. The ram may be moved back after completion of the welding operation by operating the valves by the hand lever 46.