| 摘要 |
1,206,730. Control systems for stud welding. WARREN FASTENER CORP. 20 Dec., 1968 [21 Dec., 1967 (2)], No. 60607/68. Heading H2H. Welding apparatus, such as stud welding apparatus, comprises a plurality of welding devices 14(1) ... 14(4) each of which may be supplied from a common welding supply 11 by way of individual contactors 13(1) . . . 13(4) and a common welding sequence controller 12, the readiness of a selected welding device 14 for a welding operation being ascertained by a scanning unit 19 and given access to the sequence controller 12 by means of its associated access control unit 18(1) ... 18(4) whereby the welding device is supplied with current from the supply 11 and the welding operation carried out under the control of the welding sequence controller 12 during which operation the operation of any of the other welding devices 14 is inhibited. When the operation by the selected welding device has ended the scanning, unit 19 restarts to ascertain the readiness for operation of the next welding device which is, in turn, connected to the supply 11 and sequence controller to perform a welding operation and so on. Thus only one sequence controller is required and the welding supply 11 need be sufficient to supply current to one welding device only. Each welding device is provided with switching means enabling the device to be inoperative in a sequence of welding operations. Safety switching means are provided whereby any welding device not in operation is near short circuited to safeguard a welding operator. The scanning unit 19 basically comprises a free-running multivibrator and a binary counter to produce pulses which are used in the control system to sequence the welding operations, the control of both the pilot arc current, produced by withdrawing a stud from the workpiece, and of the welding current being effected by means of thyristors. The control system includes a plurality of NOR logic units, relay and transistor switching units, and cycle counting units, the various stages in each welding operation being effected with relation to a zero crossing in the waveform of the alternating current supply. The stud welding guns 4 may be of the kind described and claimed in Specification 1,118,707. |
