GB900271A - Improvements in and relating to resistance welding - Google Patents

Abstract

900,271. Welding by pressure. PRESSED STEEL CO. Ltd. Nov. 23, 1960 [Jan. 5, 1960], No. 300/60. Class 83 (4). In effecting a plurality of resistance welds, a plurality of groups of welding electrodes are sequentially brought into contact with one of a pair of overlapped workpieces, the electrodes being connected to the secondary windings of a polyphase transformer or transformers with corresponding electrodes in the different groups connected to the same phase connection of the secondary windings, and the secondary windings being connected to one another through the workpieces as each group of electrodes is brought into contact with the workpiece, and the electrode groups are energized in sequence. The workpieces 10, 11, Fig. 1, are overlapped on a copper bar 12 and groups of electrodes 13-15, 13a-15a, 13b-15b are coupled to the bus-bars 25-27 connected to the star connected secondary windings 16-18 of a three-phase transformer 19. Each group is urged in sequence into contact with the workpieces and the circuits to the groups are connected in sequence. A machine comprises a frame 30, Fig. 2, carrying three groups of three electrodes 31a-33a, 31b-33b, 31c-33c above a copper back-up bar 34, the electrodes being connected to the busbars 39, 40, 41 supplied from the secondaries of a three-phase transformer. The electrodes have pneumatic operating cylinders 42-44a, b and c supplied electrically-operated valves 46a, b, c controlled by a sequence timer. In operation, three groups of three welds are effected automatically in sequence. The back-up bar or member of bars may be curved.