Patent GB-929131-A (GB)
Title: Improvements in resistance welding guns and in welding apparatus incorporating such guns
IPC: B23K11/30
Filed: 1959-07-07
Abstract: 929,131. Welding by pressure. A. F. FETZ. July 7, 1959, No. 23359/59. Class 83 (4). An electric resistance welder includes a piston and cylinder having a rod connected either to the piston or cylinder and supporting a welding electrode having a coolant passageway therein, the rod having an axial passageway extended by a deflector tube projecting into the electrode passageway to form a coolant duct, a port for connecting the head end of the cylinder to a pressurized coolant supply source and a coolant circuit connectable with the source and including the duct and the cylinder on one side of the piston. Each welding gun may comprise a cylinder 10, Fig. 1, which communicates with a bore 62 in a head 60, and a piston 12 which slides in the cylinder and carries a valve 72 normally spring pressed upwardly and open to allow communication between the bore 62 and a bore 24 in the piston rod 10. An extension 54 on the piston-rod is connected to a supply cable 50 and a port 48 in the extension communicates with an annular space between the bore 46 of an electrode 34 and a pipe 42 screwed into the bore 24 in the piston-rod. The valve 72 may be replaced by a ball valve. In operation with water flowing from inlet 62 down the bore 24 into the electrode, pressure is applied to the electrode by upward movement of the table 488. Increased pressure in the cylinder above the piston results and the closing of the valve 72 so that the piston is loaded to produce the required welding pressure. A pressure switch is provided to operate at a predetermined pressure, the welding current circuit, and a pressure relief valve is arranged in parallel with the pressure switch. In a modified gun the valve 72 is replaced by a simple small vertical bore and the cable is connected to the electrode carrier by a U-shaped clip. A dovetail connection between the piston-rod and electrode carrier may be provided, a layer of insulating material being arranged between the parts. In an embodiment of a gun similar to that of Fig. 1 but with a coil spring arranged between the piston and the sleeve 18 to keep the piston normally raised, water is supplied through the passage 62 and then pressure is boosted to push the piston downwardly. In another gun a ball valve 158, Fig. 11, is provided in the piston and radial passages 164 from the bore 24 to the space between the piston and sleeve, water is normally supplied to the inlet 48 to flow in the electrode, up through the bore 24 and via a by-pass 168 to the bore 24 and finally to the bore 62 via the lifted ball valve. Water also flows into the cylinder to keep the piston raised. To effect welding the water is supplied from bore 62 so that pressure builds up above the piston, closes the ball valve and lowers the piston. The water below the piston flows to bore 48 via the passages 164. A small diameter bore may replace the ball valve or no passage is provided in the piston when a water conduit is connected to an aperture 178. Threads 184 are provided on the electrode to allow its easy removal by a spanner. In another gun a diaphragm 200, Fig. 15, connected between the top of the piston-rod 194 and the wall of an upper cylinder space and a further diaphragm is connected to a lower flange on the rod and the wall of a lower cylinder space. Water supplied from a port 216 flows from the lower space into the bore 218 via radial bores and through the electrode to a port 48 to maintain the piston-rod raised. To effect welding water is supplied to a port 64 at a higher pressure to press the piston-rod downwardly. In another gun the pipe 224, Fig. 17, within the electrode extends through the piston-rod bore to the upper end of the piston 12 and cooling water is supplied to an inlet 232 to flow to space 230 into the radial bores 234 and finally into bore 62. To effect welding the pressure in bore 62 is increased. In an embodiment similar to that of Fig. 17, when the piston has been somewhat lowered the radial bore is obstructed by the sleeve so that flow through the electrode ceases. Alternatively, a non-return valve is provided at the top of the piston. The electrode holder which may be screwed into the end of the piston-rod may be inclined or cranked. In another gun a bored member 342, Fig. 25, carrying a piston 350 extends from the head 60 and slidable on the piston and normally spring urged upwardly is a cylinder 344 carrying a head 344 to which the electrode 340 and supply lead 50 are secured. Water normally flows from inlet 62 down bore 352 of member 342 into a pipe 356 leading to electrode interior and finally to an outlet 358 or the supply may be in the opposite direction. To effect welding the supply pressure is increased to build up pressure in space 354 below piston 350 to move the cylinder 344 downwardly. In another gun a cylinder 374 Fig. 27 contains a piston 386, with rod 388 for carrying the electrode, in a lower chamber 392 below a dividing member 376 and an upper piston 382 spring urged upwardly and with a rod 402 sliding in the member 376. A Venturi 368, 400 with a bore 370 leading from its narrow part to the space above the upper piston is provided in the head, the Venturi being connected by a conduit 401 to an annular chamber in the member 376 which communicates with axial grooves in the rod 402. Water is normally supplied from conduit 512, Fig. 45, to flow via an inlet 398 into space 392 to raise piston 386 and to cool the electrode and via a pipe 750 and non-return valve 752 to conduit 510. To effect welding the direction of flow is reversed and water is supplied via conduit 754 to the Venturi, valve 752 closing, to flow via conduit 400 and grooves to space above piston 386 to lower this piston and press the electrode against the work. When the electrode is pressed against the work the pressure in the Venturi increases and water flows through bore 370 to press the piston 382 downwardly. The rod 402 closes the conduit 401 and increases the pressure on the piston 386. A pressure switch in the conduit 754 closes the welding current circuit and a relief valve prevents further increase. In a modification. Fig. 29 (nit shown), water normally flowing through the electrode is brought up to flow over the lower piston and then through a Venturi connected to the cylinder wall. In another modification, Fig. 30 (not shown), the water supply to the space above the lower piston is cut off after the electrode engages the work by upward movement of the member dividing the cylinder into two chambers. A multi-spot welder comprises a base 486, Fig. 31, supporting on inflatable air cushions 494 a table 488 guided for vertical movement and spring urged downwardly, the table 488 carrying on the left-hand side horizontal counter electrodes 496 and on the righthand side inclined adjustable counter electrodes 498. Welding guns 504, 506 with movable electrodes are carried on fixed supports 507 and are connected with water conduits 510, 512. In a modified machine using the described welding guns, a counter electrode 540; Fig. 34, is supported on a frame 526 and connected to a supply cable 546. An arm 530 pivoted at 532 on the frame and urged by spring 580 against a stop 578 pivotally carries an arm 534 which supports the welding gun 536 at one end. The other end is pivoted to the piston-rod 560 of a piston 561 in a cylinder 556 pivoted at 558 to the frame. Cooling water conduits 584, 586 are provided in the cylinder on each side of the piston whose rod has conduits 562, 566 leading to the gun. With water supplied to conduit 586 the piston 561 is lowered to rotate the arm 534 and raise the gun until a stop 590 is reached by the arm when further lowering of the piston causes rotation of the arm 530 to move the gun from over the lower electrode. On reversal of the water supply and with work on the lower electrode the arm 530 rotates into contact with stop 578 and then the arm 534 rotates to bring the gun in contact with the work. A pressure switch actuates the welding current circuit. For use with the guns of Fig. 11 or 17 in which the piston and electrode are normally held raised by the cooling water, the water is supplied via a valve 688, Fig. 41, to the gun via a manifold 512, through the gun and via valve 688 to a sump 596. When the work-table 488 is lifted to engage the electrode closing of a switch 692 causes valve 688 to be changed so that water is supplied above the piston in the gun. Compressed air is supplied to the differential piston of the device 604 to exert pressure on the water above the piston in the gun.