Solid-state switching-circuit for capacitor discharge stud welding

Claim 2

In stud welding apparatus including a welding gun having means for holDing a stud to be welded to a workpiece, a power supply for providing the welding energy and contactor means for selectively connecting the power supply in circuit with the stud and workpiece to effect the weld, the improvement in said contacting means comprising: A gating rectifier having its anode and cathode connected in series with said power supply and said stud and workpiece to provide the control for the discharge of the welding energy; Circuit means for selectively placing a potential across the gate to cathode junction of the gating rectifier to establish a current of magnitude sufficient to turn on said rectifier to discharge the power supply across the stud and workpiece to effect the weld; and Impedance means in series with the rectifier and the power supply of value sufficient to maintain the current level through the rectifier below the holding value thereof but which permits sufficient leakage current therethrough when the gating rectifier is turned off to maintain dV/dt within acceptable limits upon turning on of said rectifier.

Claim 3

The welding apparatus of claim 1 in which said power supply is a capacitive power supply and said impedance means is a resistor.

Claim 4

The welding apparatus of claim 2 in which said circuit means includes means under control of the operator for connecting the welding power supply across the gate to cathode junction of said rectifier to effect turning on of said rectifier.

Claim 5

Stud welding apparatus including a welding gun having means for holding a stud to be welded to a workpiece comprising: a power supply of high energy and low internal impedance; welding conductor means of negligible impedance directly connecting said power supply across the stud and workpiece; a gating rectifier having its anode and cathode connected in circuit with said welding conductor means to provide the control for the discharge of the welding energy; circuit means for selectedly placing a potential across the gate to cathode junction of the gating rectifier to establish a current magnitude sufficient to turn on the rectifier to discharge the power supply across the stud and workpiece to effect the weld; and impedance means in series with the rectifier and the power supply of value sufficient to maintain a current level through the rectifier below the holding value thereof but which permits sufficient leakage current therethrough when the gating rectifier is turned off to drop the major portion of the power supply voltage across the rectifier when in its off state to substantially eliminate dV/dt upon contact of the stud with the workpiece to prevent premature turning on of the rectifier with its consequential hazardous effects and poor weld results.

Claim 6

Stud welding apparatus including a welding gun having means for holding a stud to be welded to a workpiece comprising: a power supply of high energy and low internal impedance; welding conductor means of negligible impedance directly connecting said power supply across the stud and workpiece; a gating rectifier having its anode and cathode connected in circuit with said welding conductor means to provide the control for the discharge of the welding energy; circuit means for selectedly placing a potential across the gate to cathode junction of the gating rectifier to establish a current magnitude sufficient to turn on the rectifier to discharge the power supply across the stud and workpiece to effect the weld; and impedance means in series with the rectifier and the power supply of value sufficient to maintain a current level through the rectifier below the holding value thereof but which permits sufficient leakage current therethrough when the gating rectifier is turned off to drop the major portion of the power supply voltage across the rectifier when in its off state to substantially eliminate dV/dt upon contact of the stud with the workpiece to prevent premature turning on of the rectifier with its consequential hazardous effects and poor weld results.

Claim 7

The stud welding apparatus of claim 4 wherein said impedance means is in parallel with the stud and workpiece and is shunted thereby upon contact of the stud with the workpiece.