GB968007A - Improvements relating to electric arc stud welding - Google Patents

Abstract

968,007. Control systems for stud-welding apparatus. CROMPTON PARKINSON Ltd. April 26, 1963 [May 2, 1962; Feb. 17, 1963], Nos. 16882/62 and 5065/63. Heading H2H. [Also in Division B3] Electric arc stud welding apparatus comprises means for charging a bank of capacitors and means including an ignitron for discharging the capacitors through the stud and workpiece to effect the weld, the arc being initiated either by retraction of the stud from the workpiece or by means of a fusible tip on the stud. Capacitors 3 are charged to a predetermined potential by means of a transformer 1 and a circuit including a rectifier 5 and contacts R3a of a relay R3, the potential being determined by the slider 9 of a potentiometer 10 in parallel with a capacitor 3. A tube TT conducts at the predetermined potential to energize relay R3 opening contacts R3a to terminate charging of the capacitors. A contact 11 operated by a timing device T periodically de-energizes relay R3 to remake the charging circuit to maintain the charge on the capacitors if these remain idle for any period. To initiate a weld, push-button PB is closed to energise relay R7, closing contacts R7a, R7b. Closure of contact R7a energizes relay R4 which isolates the capacitors 3 from the charging source by opening contacts R4a, R4b and by closing contact R4c completes the firing circuit for the ignitron 15. With a stud 16 with a fusible tip 17 in contact with the workpiece 18 (as shown in the Figure) welding current will flow through the ignitron 15 to fuse the tip 17 and thereafter complete the weld in the normal manner. When it is required to carry out a weld by first retracting the stud 16 a switch SW3 is closed to energize the stud retracting solenoid 20. The weld is initiated as before by closing push-button PB which fires the ignitron 15 through which current initially passes by way of a circuit including the now closed contact R7b. Simultaneously with the firing of the ignitron 15 the opening of a contact R4d deenergizes the solenoid 20 whereupon the stud 16 moves into contact with the workpiece 20 when the full welding current will flow through the ignitron 15. A switch SW2 allows the selection of the number of capacitors 3 used for the welding operation.