GB833389A - Timer for a high speed resistance welding machine - Google Patents

Abstract

833,389. Control systems for resistance welders. ROBOTRON CORPORATION. Feb. 20, 1958, No. 5546/58. Class 38 (4). A timing circuit for a resistance welder times the electrode moving circuit from the time that the welding current is applied in order to reduce the delay between cessation of the welding current and the opening of the electrodes. A thyratron 3 controlling the electrode movement through a relay 6, 8, 9 is controlled by a C.R. circuit 29, 31, 32 charged through a rectifier 26 from a pair of A.C. lines 1, 2 through the primary winding 22 of a transformer 23, which energizes another thyratron 38. A thyratron 21 is controlled by a C.R. circuit 12, 13 charged through a thyratron 11. On closure of a switch 4 thyratron 3 conducts, operating relay 6, 8, 9 which causes closure of the welding electrodes and selfmaintaining contacts 6. A C.R. circuit 14, 15 is now charged through a rectifier 17 and a switch 18 which blocks thyratron 11, causing capacitor 12 to discharge. Subsequently thyratron 21 conducts, energizing transformer 23 which supplies energy to a thyratron 38, conduction of which energizes a further thyratron 57 controlling the welding current. When the negative potential of a C.R. circuit 51, 52 charged from the lines I, 2 through a rectifier 48 overcomes the positive potential of a capacitor 34 the welding current is terminated and similarly when the negative potential of capacitor 52 overcomes the positive potential of discharging capacitor 29 thyratron 3 blocks releasing the welding electrodes which may therefore commence to open. By adjustment of the timing circuits the electrodes may open either in advance or arrear of the termination of the welding current. Release of the relay 6, 8, 9 causes the thyratron 11 to conduct when C.R. circuit 14, 15 has discharged thus extinguishing thyratron 21. When switch 18 is thrown to repeat position and the switch 4 held closed the above cycle will take place continuously.