GB474553A - Improvements in or relating to electric welding - Google Patents

Abstract

474,553. Supply systems for resistance welding. BERGHAUS, B. Dec. 5, 1936, Nos. 33448, 33449, and 33450. Convention dates, Dec. 7, 1935, Sept. 23, 1936, and Oct. 27, 1936. [Class 38 (iv)] Timed current impulses for resistance welding are obtained from an A.C. or D.C. source 2, Fig. 1, by first switching on the current by switch 4, and then, after the desired time interval, short circuiting the welding electrodes 1 or welding transformer by closing switch 3, the short circuit current being reduced or suppressed by means such as resistance 6, which are switched in at about the same instant, after which all the switches are opened in readiness for the next weld. In a modification, the suppressing resistance may be arranged in the shunt field circuit of a D.C. generator supplying the welding current. In a further modification, the suppressing resistance is arranged in the independent D.C. supply circuit to the field of an alternator. The electrodes 17, in the system shown in Fig. 5, are supplied through transformer 16 from an alternator 22 driven, together with its exciter 26, from the motor 29. Adjustable rheostats 24, 28 are arranged in the exciting circuits of the alternator 22 and its exciter 26, the circuit being closed or opened by the switches 25, 31, respectively. In operation, the switches 31, 25 and 3 are closed in succession. After the welding interval, short circuiting switch 4 is closed, and at or about the same instant, the field winding of the welding alternator 22 is switched out, either directly by opening switch 25 or indirectly by opening switch 31. The switches 25, 31 may be replaced by reversing switches, or a reversing winding for the exciter 26 may be energized by current supplied from the short circuit through a transformer and rectifier. Fig. 9 shows a similar system, with additions thereto including. driven drum type switches to ensure correctly timed operation, and relay discharge switches. The alternator 36 supplies welding transformer 50 through a circuit which is closed by space discharge switch 58 having igniting electrodes 58a connected to the igniting transformer 59 supplied with current at the correct instant through a drum switch 52 on a shaft 48 driven in synchronism with the motor 37 which drives the alternator 36 and its exciter 38. The short circuiting discharge switch 61 is similarly closed, at the correct interval after the main switch 58 is closed, by means of the drum switch 54 also mounted on shaft 48. The exciter 38 generates current when its exciting winding is supplied with D.C. through rectifiers 44 and transformer 43, the circuit through the transformer being closed by drum switches 45, 46. Drum 45 is mounted on shaft 48 and drum 46, having two brushes 47, one adjustable, is driven from shaft 48 at a reduced speed, whereby the instant of termination of the excitation period may be adjusted. The reverse field winding 57 of the exciter 38 is energized through rectifier 56 and transformer 55 only when the short circuiting current flows. The drum switches 52, 54 may control the main and short circuiting switches directly instead of through discharge switches.