GB797555A - Improvements in or relating to electrical resistance welding apparatus - Google Patents

Abstract

797,555. Welding by pressure. ROLLSROYCE, Ltd. Jan. 4, 1957 [Oct. 14, 1955], No. 29440/55. Class 83 (4). [Also in Group XXVI] In an electric resistance spot, stitch or step-by-step seam welding machine having fixed and movable rod or roller electrodes, the movable electrode is actuated by a first piston, the stroke of which is determined by a second fluid-pressure-actuated piston. The movable electrode 11 is connected to the rod 26 of a piston 24 having a central groove 28 vented through a duct 30 to atmosphere. The second piston 31 in a second cylinder 17 on the end of the first cylinder 14 carries a buffer 36 which abuts a skirt 25 on the first piston 24. In operation, the movable electrode 11 is fully retracted to allow insertion of the work by exhausting the lower chambers of both cylinders by linked valves 44 and operating control valve 45 to supply air at 80 - 100 1bs./sq. inch to the upper chamber 38 of the first cylinder. The electrode 11 is raised into a position adjacent the work by actuating valves 44 to supply air at 80 - 100 lbs./sq. inch to the lower chamber 40 of the second cylinder 17 and air at 60 lbs./ sq. inch to the lower chamber 43 of the first cylinder 14. Welding is then effected by alternately connecting the upper chamber 38 of the first cylinder 14 to exhaust and to the pressure source by actuating the control valve 45 under the control of an electronic timer, a switch 48 being operated when the chamber 38 is exhausted to connect up the welding circuit. In a modification welding current is passed when the upper chamber 38 is supplied with air at 30 1bs./sq. inch, the chamber being exhausted after welding so that an increased pressure on the electrode exerts a forging action.