Patent GB-833678-A (GB)
Title: Improvements in or relating to piston and cylinder assemblies for use in pneumatically operated welders
Inventor: WOLFBAUER EUGENE ANTHONY
IPC: B23K11/31
Filed: 1956-07-17
Abstract: 833,678. Welding by pressure. SAVAIR VALVE & EQUIPMENT CO. July 17, 1956, No. 22014/56. Class 83 (4). [Also in Group XXVIII] In a piston and cylinder assembly, suitable for use in a pneumatically-operated welder and comprising a cylinder 14 with a wall at each end and an intermediate wall 42 dividing the cylinder into two chambers 44, 46, a piston in each chamber and means 54 extending through the intermediate wall and connecting the pistons for movement in unison, one piston has an extension 68 extending through an opening in an end wall 50 and a clearance space is provided between the extension and the opening to permit the passage of air from the chamber adjacent said end wall and means connect the space with the other chamber. A resistance welding electrode 32 is mounted in the piston extension 68 and the assembly is mounted in a yoke 16 which carries a cooperating electrode 18, a pistol grip 10 being pivotally mounted on the cylinder. The cylinder has a body 36 with end caps 48, 50 and a wall 42 on a sleeve 40 within the body 36 forms the intermediate wall. Piston 56 in chamber 46 has a rod 54 integral therewith and slidable in an opening in the wall 42, which rod connects the piston 56 to piston 58 in chamber 44. An integral cylindrical extension 68 of piston 56 projects through the cap 50 and a sleeve 70 carrying the holder 30 for the electrode 32 is slidable in the extension with a pin and slot connection and the sleeve is normally urged to the right by a spring 84. The extension 68 slides in a bearing 158 having a series of axially extending grooves 160 open to the atmosphere at one end and to the chamber 46 at the other. A valve 20 is mounted on the cylinder and is solenoid operated by pressing a button 26 on the grip 10 to effect movement of the pistons. A spool valve 106 with spaced annular grooves 118, 120 normally spring-biased to the left but movable to the right by the armature 112 of the solenoid, is slidable in a sleeve 104 having grooves 122, 124, 126, 128, 130 opening into the sleeve, grooves 122, 126 being connected to outlet and inlet ports respectively. Slots 138, 140, 142, 144 register with grooves 122, 124, 128, 130 and with a recess 148, slots 150, 152 in the body 36 and a pair of passages 154 extending along the body 36 to open into the chamber 46 at 156. Slots 150, 152 register with annular grooves 162, 164 in the wall 42 and these grooves communicate with passages 166, 168. In operation, the solenoid is energized by pressing button 26 and the valve 106 move the position shown in Fig. 2. Compressed-air flows from inlet groove 126 to groove 162 via the valve and then through passage 166 to the rear of piston 56. The piston moves to the right and when a passageway 172 in the rod 54 is uncovered air also flows through this passageway to the rear of piston 58. The electrode 32 contacts the work and spring 84 is compressed welding current is initiated for a desired time. After a predetermined period the solenoid 22 is de-energized and the valve 106 shifts to the left when air from the inlet groove 126 flows into groove 164 and through passage 168 to the front of piston 58 to retract the pistons. During the forward movement of the pistons air in the chamber 46 in front of piston 56 flows directly through grooves 160 and air in front of piston 58 flows through passages 168, 164, 142, 144, 154 into chamber 46 and then through grooves 160. On the return stroke air in the chamber 46 is exhausted directly through passage 166 to exhaust groove 122 and air in chamber 44 is exhausted through passage 172 to passage 166.