GB1146156A - Stud welding - Google Patents

Abstract

1,146,156. Stud welding circuits. HIRST WELDING RECTIFIERS Ltd. 24 May, 1967 [26 May, 1966], No. 23593/66. Heading H2H. A stud welding timing circuit is arranged to terminate the welding current prematurely if the current is outside of say Œ 10% of a selected value. The potential across a series resistor 9 is applied to an amplifier 28, the output of which is fed through a lead 52 to a transistor circuit 29 which energizes one of lamps 58, 61, 64 and terminates the welding current at the end of a determined time or immediately if the current is low or high through relays connected thereto. In a modification relays (RLG), (RLH), (Fig. 2, not shown) in parallel with lamps 58, 64 vary the welding voltage appropriately each time a weld is terminated prematurely. The welding time may be adjusted inversely with the current by means of a switch S, which in its reversed position selects from a transistor T5 a voltage varying with the current hence varying the charging time of a capacitor 46. In this case the current tolerance may be widened to Œ20% of the selected value.