GB430768A - Improvements in or relating to electric spot welding machines - Google Patents

Abstract

430,768. Welding. HOHS, F. C., and NEW PROCESS WELDERS, Ltd., Scott's Road, Southall, Middlesex. March 29, 1934, No. 9883. [Class 83 (iv)] In an electric welding-machine wherein power means are provided for forcing the movable electrode against the work, a pedal is connected to the movable electrode through a lost motion coupling and a spring so that light pressure on the pedal will press the electrode lightly against the work, to allow positioning thereof, whilst heavier pressure on the pedal will compress the spring and energize the power means to cause the electrode to be pressed heavily against the work. The machine comprises a fixed electrode 1 and a movable electrode 2 carried by a lever 3 connected by a rod 6 to a pedal 4, pivoted at 5 to the machine frame. The rod 6 is slidable through the lever 3 which is maintained against a stop 11 on the rod by a spring 12. The initial pressure on the pedal causes the spring 12 to press the electrode 2 lightly against the work, but further pressure on the pedal compresses the spring 12 and causes the rod 6 to oscillate a lever 15 pivoted to the lever 3 and depress a valve 14, thereby closing an exhaust port 19 and admitting compressed air from a supply pipe 16<a> to a flexible pipe 17<a> and thence to a cylinder 8 pivoted to the machine frame. The piston 7 which is pivoted to the lever 3 thereupon forces the electrode 2 against the work to effect the weld. A spring 10 in the cylinder 8 returns the lever 3 to inoperative position, or alternatively or in addition a return spring may be attached to the pedal 4 or the rod 6, and a light spring 20 returns the valve 14. Known means may be provided for closing the primary circuit of the welding transformer when the heavy pressure has been established and for opening the circuit after completion of the weld.