Patent GB-824571-A (GB)
Title: Improvements in or relating to flash-butt resistance welding machines
Inventor: MORISON DAVID GRAY
IPC: B23K11/04
Filed: 1957-02-28
Abstract: 824,571. Welding by pressure. RESISTANCE WELDERS Ltd. Feb. 12, 1958 [Feb. 28, 1957], No. 6784/57. Class 83 (4). [Also in Group XXIX] In a flash butt welding machine having a moving head displaced by liquid pressure acting on a ram, the liquid being placed under pressure by a pneumatically operated pressure multiplying device, the device comprises common pneumatic means acting simultaneously on two plungers in separate chambers and valve means operable to effect selectively simultaneous connection of both chambers to the ram cylinder or connection of one chamber to the ram cylinder and connection of the other chamber to a lowpressure reservoir. A head 11 with a clamp 13 forming one electrode is fixed to a frame 10 and a head 12 with a clamp 14 forming the other electrode is movable on the frame by a power unit 17 which includes a block 18 having a cylinder 19 for the ram connected to the moving head. A reservoir 24 for liquid, e.g. oil, is mounted on the block, an air cylinder 29 is mounted above the reservoir and in the block and an extension thereof are formed on upper chamber 26 opening into a coaxial lower chamber 27. A piston 31 is in the air cylinder is mounted on a rod 32 having pistons 33, 34 of larger and smaller diameters acting in the chambers 26, 27. Passages 42 in the piston 33 connect the reservoir with the chamber 26 and passages 43 in the piston 34 connect the chambers 26, 27 when the piston 31 is in its top position as in Fig. 2. A large passage 44 leads from the chamber 26 to the reservoir and is normally closed by a solenoid operated valve 45 controlled by a switch 77 and a large passage 48 leads from the chamber 27 to the ram cylinder, a non- return valve 49 in the passage being by-passed by a variable restriction passage 51. Small passages 53, 55 lead from chamber 26 to the ram cylinder and have a metering valve 54 and a non-return valve 56 therein and a small branch passage 57 leads from the passage 53 to passage 55 and has a normally closed solenoid-operated valve 58 controlled by switch 78 therein. Air at variable pressure of 20-40 lb. per square inch or air at 80 lb. per square inch is supplied to the cylinder by solenoid-operated valves 62, 63 controlled by switches 75, 76. The ram is coupled to a member which carries at the rear of the block 18 a compressed-air cylinder which is slidable on a piston fixed to the block and a rod coupled to the ram actuates switches 75, 76, 77, 78 in a control box. In operation workpieces 15, 16 are held in the machine and moved to and fro for preheating with welding current or by alternately operating valve 62 and the valve controlling air supply to the cylinder behind the block 18. The operation may be manual or automatic in accordance with voltage changes in the welding circuit. Air from valve 62 moves the piston 31 downwardly to close passages 42, 43 and eject liquid from the chambers 26, 27 into the ram cylinder. The switch 78 is held closed to by-pass the valve 54 and the rate of return of the ram is controlled by the passage 51. After preheating air from valve 63 is admitted to the cylinder 29 and switch 78 is opened so that liquid from chamber 26 passes slowly through metering valve 54 and the head advances for flashing. After a predetermined movement of the head the rod connected to the ram operates switch 77 so that the valve 45 opens to allow liquid in chamber 26 to flow into the reservoir. The liquid in the ram cylinder is now only actuated by piston 34 so that increased pressure is produced to effect butting and forging. According to the Provisional Specification a by-pass valve connecting the upper liquid chamber with the ram cylinder or with the reservoir is controlled by the movement of the moving head and the air cylinder and liquid chambers may be horizontally arranged.