Patent GB-952683-A (GB)
Title: Control and regulating system for arc-welding equipment, more particularly stud welding equipment with power regulation
IPC: B23K9/20
Filed: 1962-02-02
Abstract: 952,683. Control circuits for arc welding. PECO VERKAUFSGESELLSCHAFT. Feb. 2, 1962 [Feb. 21, 1961], No. 3987/62. Heading H2H. The welding time of a stud welding gun P is automatically regulated according to the welding current by a circuit comprising a measuring resistance R M  feeding a first electronic lime stage Z n  which controls a contactor G through elements S T  and which is adjustable to vary the welding time according to the workpiece dimensions, e.g. stud diameter or cross-section. The adjustment of stage Z II  is coupled to that of a second time stage Z 1  having maximum time values corresponding to minimum permissible values of welding current, the arrangement ensuring that if, in a particular case, the stage Z II  does not open contactor G within the maximum time determined by stage Z I , this opening is effected by stage Z I  which also initiates a warning signal and/or prevents any further welding operation. The equipment is supplied through a power unit N, Fig. 2, closure of main switch S energizing a relay M whose contact M 1  controls the gun coil P sp  and contactor G, and whose contact M 2  controls the time stage Z 1 . Operation of the gun trigger D energizes a relay E to complete a circuit including a choke D r  and a relay F which, if the current is sufficiently high, operates to start the time stage Z I  (through contact f 2 ) and to hold relay E energized until contactor G is operated, in the event of premature release of the trigger D. In time stage Z I  a transistor T 1  blocks and a transistor T 2  conducts, so that a relay H is energized to close an interlock contact h 1 , to close a contact h 2  and so energize relays A, B, thus lifting the gun P and closing contactor G, and to close a contact h 3  and so start the time stage Z n . The volt drop across resistance R M  is stepped-up through a D.C. transformer comprising transistors T 3 , T 4  and an associated transformer, and then fed to the stage Z 11  in which the time taken for a condenser C 2  to charge to a certain voltage depends on the setting of a switch S 2  and on the voltage received from resistance R M . When condenser C 2  reaches the appropriate voltage, a four layer semi-conductor diode T 5  conducts and the resultant pulse is amplified by transistors T 6  and T 7  to energize a relay I, which switches off relays A, B and thus de-energizes gun coil Psp and opens contactor G. Relay I remains energized until relay H is de-energized due to condenser C 1  charging up, and the relay E is switched off (when contactor G closes) by energization of a relay L which remains energized until the gun trigger D is released, whereupon another welding operation can be initiated. If the welding current is too low the condenser C 1  charges up before condenser C 2  and deenergizes the relay H which switches off relays A, B to terminate the weld, the de-energization of relay H before relay B causing a condenser C 3  to discharge through a relay K whose consequent energization switches on a warning lamp W and switches off the relay M. The relay K is self-holding and thus another welding operation cannot be initiated until it has been released by operation of a key T. Condensers C 1 , C 2  are charged through resistors R 1 , R 2  whose values are selected by the setting of the switch S 2  which is coupled to the switch S 1 . If desired, the relay K may operate only the lamp W or the relay M. A modification is mentioned, but not described, in which protection is also provided against excessive welding currents by effecting a minimum time setting corresponding to a maximum current value.