Direct current arc welder

Claim 2

In a direct current arc welder comprising a phase control circuit for controlling the triggering phase of at least one controlled rectifier element to convert alternating current into direct current which is in turn supplied to a welding electrode and a workpiece to be welded and a feed back circuit for negatively feeding a portion of the direct current output thus converted back to a control circuit for the phase controlled rectifier circuit to thereby control the welder output, the improvement which comprises a gain compensating circuit provided in said phase control circuit by which the gain of the control circuit can be compensated in response to the value of said direct current output of the welder to maintain the gain of said control circuit at a substantially constant value irrespective of variations in the value of said direct current output.

Claim 3

In a direct current arc welder comprising a phase a phase control circuit for controlling the triggering phase of at least one controlled rectifier element to convert an alternating current into direct current which is in turn supplied to a welding electrode and a workpiece to be welded and a feed back circuit for negatively feeding a portion of the direct current output thus converted back to the phase control circuit to thereby control the welder output, the improvement wherein said phase control circuit includes an output preset circuit of the welder, a control signal generator circuit and a gain compensating circuit, the output of said preset circuit being adapted to be compared with a negatively feed back signal fed from said feed back circuit to provide a signal rEpresentative of the difference therebetween which is in turn supplied to said control signal generator circuit through said gain compensating circuit.

Claim 4

In a direct current arc welder comprising a phase a phase control circuit for controlling the triggering phase of at least one controlled rectifier element to convert an alternating current into direct current which is in turn supplied to a welding electrode and a workpiece to be welded and a feed back circuit for negatively feeding a portion of the direct current output thus converted back to the phase control circuit to thereby control the welder output, the improvement wherein said phase control circuit includes an output preset circuit of the welder, a control signal generator circuit and a gain compensating circuit, the output of said preset circuit being adapted to be compared with a negatively feed back signal fed from said feed back circuit to provide a signal rEpresentative of the difference therebetween which is in turn supplied to said control signal generator circuit through said gain compensating circuit.

Claim 5

A direct current arc welder as claimed in claim 2, wherein said phase control circuit comprises a first series circuit including a pulse transformer, a uni-junction transistor and a resistor and a second series circuit including a condensor disposed in parallel to a synchronizing circuit and having one end connected with the emitter of said uni-junction transistor, an amplifier transistor and a resistor, said preset circuit including a variable resistor connected in parallel to a DC power source and said gain compensating circuit including a first resistor, a amplifier transistor and a second resistor, said first resistor and amplifier transistor of said gain compensating circuit being connected in series with each other and connected in parallel to a resistor having one end connected with the base of the amplifier transistor of said second series circuit while the base of said amplifier transistor of said gain compensating circuit connected with the positive terminal of said DC power source through said second resistor, whereby the voltage of the feed back signal is supplied between a slider of said variable resistor and said resistor connected with the base of said amplifier transistor.

Claim 6

In a direct current arc welder comprising a phase control circuit for controlling the triggering phase of at least one controlled rectifier element to convert alternating current into direct current which is, in turn, supplied to a welding electrode and a workpiece to be welded and a feed back circuit for negatively feeding a portion of the direct current thus converted back to the phase control circuit thereby to control the welder output, the improvement wherein said phase control circuit includes an output preset circuit, a comparision circuit for comparing the output from said preset circuit with the negative feed-back signal to provide a signal representative of the difference therebetween, a triangular wave generator circuit including a gain compensating circuit and a control signal generator circuit whereby, only when the output of said triangular wave generator circuit exceeds the value of said signal representative of the difference therebetween, a signal can be supplied to said control signal generator circuit.

Claim 7

In a direct current arc welder comprising a phase control circuit for controlling the triggering phase of at least one controlled rectifier element to convert alternating current into direct current which is, in turn, supplied to a welding electrode and a workpiece to be welded and a feed back circuit for negatively feeding a portion of the direct current thus converted back to the phase control circuit thereby to control the welder output, the improvement wherein said phase control circuit includes an output preset circuit, a comparision circuit for comparing the output from said preset circuit with the negative feed-back signal to provide a signal representative of the difference therebetween, a triangular wave generator circuit including a gain compensating circuit and a control signal generator circuit whereby, only when the output of said triangular wave generator circuit exceeds the value of said signal representative of the difference therebetween, a signal can be supplied to said control signal generator circuit.

Claim 8

A direct current arc welder as claimed in claim 4, wherein said control output preset circuit includes a DC power source of constant voltage and a variable register connected in parallel to said power source, said comparision circuit having a resistor and an amplifier transistor for comparing the output from said preset circuit with the negative-feed back signal, said control signal generator circuit including a series circuit having a pulse transformer and a switching transistor disposed between the positive and negative terminals of said power source, a resistor connected with a combination of a resistor and a condensor connected between the emitter and base of said switching transistor of said series circuit and a switching transistor disposed between a junction between said condensor and a resistor and said comparison circuit, said triangular wave generator circuit including the gain compensating circuit, said triangular wave generator circuit consisting of a resistor connected between the base of said switching transistor of said control signal generator circuit and the negative terminal of said power source, a series circuit including a condensor connected in parallel to a synchronizing circuit and an amplifier transistor the base of which is connected with the negative terminal of said power source through a resistor, and a resistor, and an amplifier transistor of said series circuit and one end of said resistor, the base of which is connected with said condensor.

Claim 9

A direct current arc welder according to claim 4, wherein said phase control output preset circuit includes a first DC power source and a variable resistor connected in parallel with said power source, said comparison circuit for comparing the output of said preset circuit with said negative feed back signal including a first resistor and a first amplifier transistor connected together in parallel with said variable resistor, and said control signal generator circuit having a pulse transformer and a first switching transistor connected in series between the positive and negative terminals of said first power source.

Claim 10

A welder according to claim 6, wherein said control signal generator circuit further includes a second resistor connected between the base and emitter of said first switching transistor, a series circuit of a resistor and a capacitor including a first capacitor and a third resistor connected across said second resistor and further including a second switching transistor connected between the junction of said first capacitor and said third resistor and said first amplifier transistor of said comparision circuit.

Claim 11

A welder according to claim 7, wherein said triangular wave generating circuit includes said gain comparison circuit, said triangular wave generating circuit having a fourth resistor connected between the base of said second switching transistor and one terminal of said first DC power source, a second amplifier transistor and a fifth resistor, one end of which is connected to one electrode of said second amplifier transistor, connected across said fourth resistor, and a synchronizing circuit for said alternating current, including a third amplifier transistor, the emitter and collector electrodes of which are connected between the base electrode of said second amplifying transistor and one end of said fifth resistor.

Claim 12

A welder according to claim 7, wherein said triangular wave generating circuit further includes a fourth amplifier transistor and a second capacitor connected in series and being resistively coupled to a second D.C. power source, the junction of said second capacitor and said fourth amplifying transistor being connected to the base of said second amplifying transistor.