GB888563A - Improvements in or relating to control systems particularly for resistance welding apparatus - Google Patents

Abstract

888,563. Control systems for resistance welders. LANCASHIRE DYNAMO ELECTRONIC PRODUCTS Ltd. May 7, 1958 [Feb. 7, 1957], No. 4253/57. Class 38 (4). A control system for operating a switching device for, say, a resistance welding machine, at determined intervals comprises a multi-cathode discharge tube 10 which in conjunction with a first group of cathodes 0-4 of a second tube 12 counts cycles of A.C. to determine an " on " time, and which in conjunction with a second group of cathodes 5-9 also in the second tube determines an " off " time. The times are selected by switches S1, S2 for the " on " time and S3, S4 for the " off " time, each pair of switches feeding a coincidence detector 18, 20 which each feeds an output pulse to cathodes 5 or 0, respectively, of the tube 14 and cathode 0 of the tube 10, to initiate a further count. A switch S5 having three positions allows a single cycle, continuous operation, or a shut-down, after a number of cycles determined by a switch S6 co-operating with a further tube 28. In the quiescent state of the circuit, cathodes 9 of both tubes 10, 12 are glowing. A or a number of sequences are started by resetting switch 26 which allows a pulse generator 15 to transfer the glow of tube 10 to cathode 0, which in turn through another pulse generator transfers the glow on tube 14 to cathode 0, thus switching on an output device 22 controlling an external circuit through one of rectifiers 23. When the " on " time has been counted out, the coincidence detector transfers the glows to cathode 0 of tube 10 and cathode 5 of tube 12, the latter turning off the output device 22 for a time dependent on the setting of the switches.