GB764764A - Improvements relating to electric arc stud welding and pin brazing - Google Patents

Abstract

764,764. Welding by pressure. CROMPTON PARKINSON, Ltd. March 28, 1955 [April 8, 1954], No. 9004/55. Class 83 (4). In electric stud welding or soldering apparatus including a tool having a solenoid coil for retracting the stud against a spring, the'coil is connected in series with the welding circuit so as to be energized to retract the stud as soon as the circuit is completed and a contactor is provided for short-circuiting the coil after retraction of the stud to apply full welding or soldering current. A gun has a two-part solenoid coil 10a, 10b about a stationary armature 11 and a movable armature 12 mechanically connected to the stud chuck 21, the armatures being pressed apart by a spring 13. The gun is connected in a circuit as in Fig. 2, the D.C. source P being a motor generator set or rectifier. With the stud S in contact with the work W the button PB is pressed to energize a timing relay TR and a control relay CR having contacts CR1, CR2 and CR3. The contacts CR1 energize the coil 10a through a lead 16, the stud S and the work W to lift the stud and strike a low current arc. When the arc voltage is established the coil 10b in parallel with the arc is energized to hold the stud retracted. Contacts CR2 short-circuit the button and CR3 energize contactor C, whose contacts C1 close to shortcircuit the coil 10a, full welding current then flowing. The arc continues until contacts TR1 of relay TR open to de-energize relay CR and in turn contactor C to interrupt the welding current and to de-energize coil 10b, allowing the stud to be thrust down by the spring 13. In a modification the coil 10b is connected through further contacts CR4 (not shown) of the relay CR so that the stud may be thrust downwardly before the welding current is interrupted. In a further modification the coil 10b is opencircuited so that the stud is thrust downwardly immediately the coil 10a is short-circuited. In another modification a further time delay relay controls the main contactor so that the welding current may be allowed to flow until after the stud has reached the workpiece. Specification 580,702 is referred to.