Patent GB-861762-A (GB)
Title: Improvements in or relating to electric welding apparatus
IPC: B23K11/25
Filed: 1957-04-12
Abstract: 861,762. Welding by pressure. IGRANIC ELECTRIC CO. Ltd. April 12, 1957 [April 19, 1956], No. 12018/57. Class 83 (4). Electric welding apparatus comprises synchronous tuning means, a fixed electrode and a movable electrode, means operable to cause the movable electrode to move towards the fixed electrode and thereafter to apply an increasing force on workpieces therebetween until a predetermined force is reached, means for ensuring that the predetermined force is maintained substantially constant for a given interval of time, means for initiating operation of the timing means and thereby the welding current during the interval and means effective at or after the termination of the interval to further increase the force applied to the movable electrode at a rate independent of the magnitude of the welding current. A welder comprises an adjustable lower electrode 1 and a movable upper electrode 2 carried on a shaft 5 passing through a frame 4. A U-shaped magnetic core 6 with a winding 9 on its polepieces is mounted on the bottom of the frame and coils 12, 13 with adjustable cores 10, 11 are mounted on the top of the frame. The upper end of the shaft extending above the frame has a reduced portion 28 carrying a plate 29 and surrounded by a cylindrical sleeve 30 having a flange 31 and an arm 32 for operating a switch 33 on the plate 29. Plate 29 and flange 31 are connected by a number of springs 34. A fluid cylinder 35 is mounted on the frame and has a piston 36 secured to the sleeve 30 and a piston 37 secured to the shaft 5 beneath a shoulder 38 thereon, and supply of fluid e.g. air above the piston 36 is via a valve 42, normally to exhaust, operated by a solenoid 42a connected to a synchronous timer ST through a switch 45 carried on the top of the cylinder 35. Supply of fluid below the piston 37 is via a valve 41, normally in its supply position, operated by a solenoid 41a connected to the timer. The switch 33 is connected to the timer for initiating the welding current. A transformer 58 connected to the timer is connected to the lower electrode and the upper electrode via the coil 9. In operation with the parts in the position shown in Fig. 1 and a supply of rectified current to the windings 12, 13 to hold an armature 17 raised against the cores 10, 11, the timer is energized to place valve 41 in exhaust and thus allow the electrode 2 to sink down under gravity to engage the work 3. The plate 29 and sleeve 30 also move down and a member 46 on the flange 31 operates the switch 45 thus causing valve 42 to supply fluid above piston 36. Sleeve 30 then applies a force to the upper end of the shaft through the springs 34 and the force builds up (see Fig. 7) without relative movement between the shaft and sleeve until at a point X the springs stretch. As the springs stretch and the sleeve moves on the shaft to engage the shoulder 38 the force on the electrode remains substantially constant and then an increasing force is transmitted directly to the shaft. During the movement of the sleeve on the shaft the switch 33 is operated to cause welding current to flow. If magnetic force assistance is required the coils 12, 13 are not energized and armature 17 rests on stop nuts 27 on the shaft so that when welding current flows through the coil 9 the armature is attracted. If a delayed forging is required the coils 12, 13 are energized to hold the armature but with the cores 10, 11 in a lowered position and when the force developed by the coil 9 overcomes that developed by the coils 12, 13 the armature snaps down to strike a hammer blow. A projection may be provided on one of the parts to be welded. Specification 780,583 is referred to.