GB811051A - Electric resistance welding gun - Google Patents

Abstract

811,051. Welding by pressure. ALLAN, A. J., and BOOTH, P. H. July 19, 1957 [Sept. 10, 1956], No. 22943/57. Class 83 (4). An electric resistance welding gun comprises a plunger 11, for carrying an electrode 14, slidable in a guide member 10 and biased in one direction, a switch 25 mounted on the guide member for connecting the gun to a source of current, means on the plunger to engage a member. 29 to actuate the switch, a trigger 37 movable against a bias to actuate the switch and means 40 to render selectively the plunger and trigger inoperative to actuate the switch. Handles 13a, 13b extend from each side of the guide member, a cylindrical barrel, and the plunger in the barrel is connected at one end to a copper or brass ferrule 16 holding the electrode and bears at the other end against a spring 20 which urges the plunger against a stop 24 in the barrel. The tension of the spring is adjustable by a screw 23 in the barrel end cap. A micro switch 25 is mounted in the handle 13b and an operating arm 29 therefor is pivoted at 30 to extend through a slot 31 in the barrel into a recess 32 in the plunger. The trigger 37 is slidable in the guide member and engages a spring-loaded pin 39 in contact with the arm 29. A cam 40 rotatable by a lever 42 is mounted behind the trigger so that when the lever is in a position 45 a flattened cam portion 43 allows a locking pin 49 to be spring urged out of a recess 47 in the plunger but prevents movement of the trigger. In lever position 44 the locking pin is urged into the recess 47 and the flat 43 allows trigger operation. In lever position 46 both plunger and trigger are locked. In operation with lever 42 in position 45 the gun is pressed against the work to move the plunger against the spring so that a face 34 on the plunger engages the arm 29 to actuate the switch thus allowing current flow along the cable 35 to a carbon bush 36 contacting the ferrule 16. With the lever 42 in position 44 the gun is pressed against the work and the trigger is pressed to actuate the switch. The spring 20 may be dispensed with when compressed air is admitted to the barrel behind the plunger by a pipe 55.