GB721449A - Improvements in or relating to portable electric spot welders - Google Patents

Abstract

721,449. Welding by pressure. DIVERS, S. V., and YOXALL, F. Dec. 18, 1952 [Sept. 21, 1951], No. 22119/51. Class 83 (4). In a portable electric spot-welder having a toggle lever mechanism whereby the distance between the electrodes can be varied, the mechanism is adapted to lock the electrodes in their gripping position. In an embodiment a head 2 affixed to a transformer 3 carries an electrode 5 fixed in an aperture 7. Three split bushes 8, 9, 10; 8, 10 being of metal and 9 of an insulating material, are interposed between the electrode 5 and the aperture and a tightening means comprising a headed screw 17 in a transverse aperture 13 which engages a threaded collar 12 on one side of the split bushes and a clearance collar 11 on the other side which pulls the collars together to wedge against the bushes. A second electrode 6 is mounted in a similar manner but with only one bush, this of metal, in a block 20 pivoted at 21 to the head 2. A toggle operating device comprises an arm 32 pivoted at 31 to the block 20 and an arm 35 pivoted at one end to the arm 32 at 34 and at the other end at 36 to a block 37 adjustable in a guide 38 by a screw 42 acting against a spring 41. Movement of the arm 32 away from a handle 45 opens the electrodes 5, 6 while movement of the arm 32 towards the handle closes them. When the pivot 34 moves to a position on the same side of a line joining pivots 31, 36 as that of the pivot 21 and a nose 34a on the arm 34 engages the arm 32 the electrodes lock in position. Movement of the block 37 by the screw 42 varies the distance between the electrodes in their gripping position. A trigger 4 controls supply of current to the primary of the transformer, the secondary being connected to the electrode 5 through the bush 10 and to the electrode 6 by a strap 46. The arm 32 may be operated manually or by power.