Patent GB-761434-A (GB)
Title: Improvements in or relating to electrical resistance welding apparatus
Inventor: COOKE FRANK ARTHUR
IPC: B23K11/31
Filed: 1953-02-05
Abstract: 761,434. Welding by pressure. ROLLS-ROYCE, Ltd. May 4, 1954 [Feb. 5, 1953], No. 3338/53. Class 83 (4). In a spot, stitch or step by step welder having a cylinder and a piston therein, a pressure-responsive device operates in a space within the piston which is closed off from the cylinder space and is connected to one electrode, the piston being movable in the cylinder to a greater extent than the device is movable in the piston, and means are provided to supply pressure fluid to the piston ends to move it in the cylinder and to the device to move it and the electrode relatively to the piston. In an embodiment, the movable rod electrode 12 of a welder is secured to the rod 17 of a stepped piston 31 in the hollow upper part 21 of a piston formed of two parts 20, 21 working in a cylinder 14. The stroke of the piston 20, 21 is adjustable by a hand wheel 39 screwed to a threaded extension 37 thereon. Air at 85 lbs. p.s.i. is admitted from a main 44 through a hand operated valve 47 in one position to the top of the cylinder 14 and through the valve in the other position to the bottom of the cylinder. Air at 60 lbs. p.s.i. from the main through a reducing valve, is admitted to the top of piston 31 through a valve 51 in one position and a bore 42 in the rod 17. With the valve 51 in the other position the top of piston 31 is connected to atmosphere. The bottom of the piston 31 is connected through a union 28, secured to the piston 20, 21 and sliding in a slot in the cylinder 14, to a shuttle valve 54. Air from the main is connected through a solenoid operated valve 57 to one inlet 55 of the valve, the inlet being connected to the main when the solenoid is de-energized and to atmosphere when energized, a second inlet 56 is connected through a solenoid operated valve 59 either to atmosphere when the solenoid is de-energized or to air at 30 lbs. p.s.i. in a reservoir 60 when the solenoid is energized. A sliding member in the shuttle valve opens the latter to pressure air acting on it from one inlet and closes the valve to the other inlet. A zero pressure switch 72 initiates welding current flow after a delay period when the pressure in inlet 55 falls to atmosphere. In operation, the valve 47 is firstly set to lift piston 20, 21 to allow insertion of workpieces between the electrodes and is then set to lower the piston 20, 21. The valve 51 is set to supply 60 lbs. p.s.i. air to the top of piston 31, air at 85 lbs. p.s.i. being supplied to the bottom through valve 57. An electronic timer is operated and firstly the solenoid 57a is energized, the pressure below piston 31 falling to atmosphere and the work being squeezed by the electrodes. The switch 72 operates to supply welding current after a delay. Simultaneously with or before current supply the solenoid 59a is energized and air at 30 lbs. p.s.i. is admitted beneath the piston 31 to relieve the electrode pressure. Solenoid 59a is de-energized shortly after the flow of welding current ceases and electrode pressure increases for forging. Alternatively a two. position, pressure air supply and atmosphere, solenoid-operated valve may be connected to the under side of piston 31 and the rod electrodes may be replaced by rollers. A flexible diaphragm clamped between the two piston parts 20, 21 may replace the piston 31.