Spot welding appts. with electronic circuit to control current - for mfr. of steel cages for reinforcing concrete pipes

摘要

Electronic control circuit is provided for the resistance spot welding of steel rods in mfg. cases for reinforcing concrete pipes etc. The welding electrodes are fed periodically from a transformer, using a timer controlled by the movement between the electrodes and the rod junctions. The timer is coupled via a clock generator to a controller fed with a signal (Sa) representing the actual welding current, and the desired, reference currents (Sr). The controller adjusts the welding voltage according to the output signals of the clock generator, and supplies a voltage to the transformer which is inversely proportional to the alteration in Sa. In the pref. electronic circuit, a thyristor stage is connected in series with the prim. of the transformer, and actuated by a logic circuit included in the clock generator. Used for accurate control of welding current to obtain strong welds which are subject to inspection involving vibration combined with tensile stress.