Patent GB-975631-A (GB)
Title: Capacitance discharge stud welding apparatus
IPC: B23K9/10
Filed: 1961-05-31
Abstract: 975,631. Welding by pressure. KSM PRODUCTS Inc. May 31, 1961 [Aug. 3, 1960], No. 19721/61. Heading B3R. [Also in Division H2] A capacitance discharge stud welding apparatus comprises means for moving a stud into contact with a workpiece or a workpiece support, a capacitor charging circuit including capacitor means and means for supplying unidirectional voltage thereto, a welding circuit comprising the capacitor means connected between the means for moving a stud and the workpiece support, a capacitor charging control circuit comprising means sensitive to voltage and including a relay, which are operative, when the charge on the capacitor means reaches a predetermined value, to open the charging circuit and an operating control circuit including means responsive to the operation of the relay to render the means for moving a stud operative to move the stud into contact with a workpiece following the opening of the charging circuit. A three-phase supply is connected, through contacts 10, 12, 14 of a relay 18 powered by singlephase from the same supply, to a transformer 28, the secondary of which supplies a full-wave rectifier 32 connected to a bank of capacitors 34, 36, 38 through parallel switches 35, 37, 39 and normally open contacts 42 of a relay 44. A resistor 46 is connected across the capacitors through normally closed contacts 48 of a relay 50 and a voltage control relay 60 is connected across the capacitors through a silicon Zener diode 62 and a potentiometer 64 whose ends are connected to a stud holder in a stationary stud welder and to a base on which the work is clamped. A single-phase current is supplied to a transformer 30 for the control apparatus. A voltage sensitive relay or thyratron may replace the Zener diode. In operation after a switch 20 in the circuit of relay 18 has been operated to cause the contacts 10, 12, 14 to close, two seriesconnected switches 54, 56 in the control circuit are closed by the operator using both hands, thus operating solenoid 58 controlling a pneumatic clamp for the workpiece and operating a relay 50 for opening contacts 48 to remove the resistor 46 from the charging circuit. The relay 44 is also energized to close contacts 42 to complete the charging circuit and to open contacts 45. When the voltage on the diode 62 reaches a critical value, variable by the potentiometer 64, it passes current to the relay 60 which opens its contacts 61 to de-energize relay 44 and open contacts 42 to interrupt the charging circuit and to close contacts 45 to energize the relay 66. The relay 66 opens its contacts 68 in series with relay 44 to ensure that the relay remains deenergized and closes its contacts 70 to energize a relay 76 which in turn closes its contacts 78 to energize solenoid 82 for actuating the pneumatic piston-and-cylinder device for moving the stud towards the work. Contacts 80 are opened after a delay by relay 76 to de-energize solenoid 82 to retract the stud holder after welding. A switch 84 is provided in series with solenoid 82 to allow capacitors to be charged and voltage adjusted without effecting a weld. A similar apparatus may be used to supply four successively operated guns supplied from separate condensers.