Electric welder with current-voltage feedback circuit that provides desired slope curve

• US 4,465,920 A
• Filed: 04/20/1981
• Issued: 08/14/1984
• Est. Priority Date: 09/22/1978
• Status: Expired due to Term

• Current Assignee: Teledyne-Walterboro
• Original Assignee: Teledyne-Walterboro
• Inventors: Greene, William J., Hoyt, Harold C. Jr.
• Primary Examiner(s): Shaw, C. C.
• Application Number:
  US06/255,354
• Time in Patent Office: 1,212 Days
• Field of Search: 219/133, 219/134, 219/130.33, 219/130.32, 219/130.01, 322/25, 322/59, 322/60
• US Class Current: 219/133
• CPC Class Codes: B23K 9/10 Other electric circuits therefor; Protective circuits; Remote controls

Abstract

A D.C. welder includes an engine-driven D.C. generator, a polarity-revers switch which can change the direction of current flow through the field winding of that generator to provide a positive or negative polarity at the welder output terminals, a circuit that automatically permits only uni-directional current flow through that field winding during the starting of the engine, and a further circuit that energizes a solenoid to close contacts which enable that generator to operate as the starting motor for that engine but which thereafter de-energizes that solenoid and then keeps it de-energized until the engine is at, or close to, rest.

Claims

1. An electric welder which comprises a D.C. generator, a command circuit that can develop a variable value command signal, a current feedback circuit, a voltage feedback circuit, a control circuit which receives said command signal from said command circuit and that can simultaneously respond to a signal from said current feedback circuit to provide a current-modified command signal which will be applied to the field winding of said D.C. generator, said field winding responding to said current-modified command signal to cause said electric welder to operate in a constant current mode, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage feedback circuit to provide a voltage-modified command signal which will be applied to said field winding of said D.C. generator, said field winding responding to said voltage-modified command signal to cause said electric welder to operate in a constant voltage mode, a voltage-current feedback circuit which receives said signal from said current feedback circuit and which simultaneously receives said signal from said voltage feedback circuit, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage-current feedback circuit to provide a voltage-current-modified command signal which will be applied to said field winding to said D.C. generator, said field winding responding to said voltage-current-modified command signal to cause said electric welder to operate in a slope mode, and mode-selecting means that selectively connects said current feedback circuit or said voltage feedback circuit or said voltage-current feedback circuit to said control circuit.

2. An electric welder which comprises a D.C. generator, a command circuit that can develop a variable value command signal, a current feedback circuit, a voltage feedback circuit, a control circuit which receives said command signal from said command circuit and that can simultaneously respond to a signal from said current feedback circuit to provide a current-modified command signal which will be applied to the field winding of said D.C. generator, said field winding responding to said current-modified command signal to cause said electric welder to operate in a constant current mode, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage feedback circuit to provide a voltage-modified command signal which will be applied to said field winding of said D.C. generator, said field winding responding to said voltage-modified command signal to cause said electric welder to operate in a constant voltage mode, a voltage-current feedback circuit which receives said signal from said current feedback circuit and which simultaneously receives said signal from said voltage feedback circuit, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage-current feedback circuit to provide a voltage-current-modified command signal which will be applied to said field winding of said D.C. generator, said field winding responding to said voltage-current-modified command signal to cause said electric welder to operate in a slope mode, mode-selecting means that selectively connects said current feedback circuit or said voltage feedback circuit or said voltage-current feedback circuit to said control circuit, said D.C. generator being adapted to develop a positive voltage or a negative voltage at an output thereof, means to enable said D.C. generator to selectively develop said positive voltage or said negative voltage at said output thereof, a subcircuit means that enables said current feedback circuit to provide a current feedback signal of a given polarity when said D.C. generator is developing said positive voltage at said output thereof and to provide a current feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said output thereof.

3. An electric welder which comprises a D.C. generator, a command circuit that can develop a variable value command signal, a current feedback circuit, a voltage feedback circuit, a control circuit which receives said command signal from said command circuit and that can simultaneously respond to a signal from said current feedback circuit to provide a current-modified command signal which will be applied to the field winding of said D.C. generator, said field winding responding to said current-modified command signal to cause said electric welder to operate in a constant current mode, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage feedback circuit to provide a voltage-modified command signal which will be applied to said field winding of said D.C. generator, said field winding responding to said voltage-modified command signal to cause said electric welder to operate in a constant voltage mode, a voltage-current feedback circuit which receives said signal from said current feedback circuit and which simultaneously receives said signal from said voltage feedback circuit, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage-current feedback circuit to provide a voltage-current-modified command signal which will be applied to said field winding of said D.C. generator, said field winding responding to said voltage-current-modified command signal to cause said electric welder to operate in a slope mode, mode-selecting means that selectively connects said current feedback circuit or said voltage feedback circuit or said voltage-current feedback circuit to said control circuit, said D.C. generator being adapted to develop a positive voltage or a negative voltage at an output thereof, and means to enable said D.C. generator to selectively develop said positive voltage or said negative voltage at said output thereof, a subcircuit means that enables said voltage feedback circuit to provide a voltage feedback signal of a given polarity when said D.C. generator is developing said positive voltage at said output thereof and to provide a voltage feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said output thereof.

4. An electric welder which comprises a D.C. generator, said D.C. generator being adapted to develop a positive voltage or a negative voltage at an output thereof, selective means to enable said D.C. generator to selectively develop said positive voltage or said negative voltage at said output thereof, a command circuit that can develop a variable value command signal, a current feedback circuit, a subcircuit means that enables said current feedback circuit to provide a current feedback signal of a given polarity when said D.C. generator is developing said positive voltage at said output thereof and to provide a current feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said output thereof, a voltage feedback circuit, a subcircuit means enabling said voltage feedback circuit to provide a voltage feedback signal of a given polarity when said D.C. generator is developing said positive voltage at said output thereof and to provide a voltage feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said output thereof, a control circuit which receives said command signal from said command circuit and that can simultaneously respond to a signal from said current feedback circuit to provide a current-modified, command signal which will cause said electric welder to operate in a constant current mode, said control circuit being adapted to receive said command signal from said command circuit and to simultaneously respond to a signal from said voltage feedback circuit to provide a voltage-modified command signal which will cause said electric welder to operate in a constant voltage mode, and mode-selecting means that selectively connects said current feedback circuit or said voltage feedback circuit to said control circuit.

5. An electric welder which comprises output terminals, a D.C. generator that can selectively develop a positive voltage or a negative voltage at one of said output terminals, an energizing circuit for the field winding of said D.C. generator, a polarity-controlling switch that can be set in one position to enable said energizing circuit to cause current to flow through said field winding in a direction which will enable said D.C. generator to develop said positive voltage at said one output terminal, said polarity-controlling switch being adapted to be set in a second position to enable said energizing circuit to cause current to flow through said field winding in the opposite direction and thereby enable said D.C. generator to develop said negative voltage at said one output terminal, a command circuit that can develop a variable value command signal, a current feedback circuit, a control circuit which receives said command signal from said command circuit and that can simultaneously respond to a signal from said current feedback circuit to provide a current-modified command signal which will be applied to the field winding of said D.C. generator, said field winding responding to said current-modified command signal to cause said electric welder to operate in a constant current mode, a subcircuit means that enables said current feedback circuit to provide a current feedback signal of a given polarity when said D.C. generator is developing said positive voltage at said one output terminal and to provide a current feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said one output terminal.

6. An electric welder as claimed in claim 5 wherein a voltage feedback circuit supplies a signal to said control circuit, wherein said control circuit receives said command signal from said command circuit and can simultaneously respond to a signal from said voltage feedback circuit to provide a voltage-modified command signal which will be applied to the field winding of said D.C. generator, wherein said field winding responds to said voltage-modified command signal to cause said electric welder to operate in a constant voltage mode, wherein mode-selecting means selectively connects said current feedback circuit or said voltage feedback circuit to said control circuit, wherein a subcircuit means enables said voltage feedback circuit to provide a voltage feedback signal of said given polarity when said D.C. generator is developing said positive voltage at said one output terminal and to provide a voltage feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said one output terminal.

7. An electric welder which comprises output terminals, a D.C. generator that can selectively develop a positive voltage or a negative voltage at one of said output terminals, an energizing circuit for the field winding of said D.C. generator, a polarity-controlling switch that can be set in one position to enable said energizing circuit to cause current to flow through said field winding in a direction which will enable said D.C. generator to develop said positive voltage at said one output terminal, said polarity-controlling switch being adapted to be set in a second position to enable said energizing circuit to cause current to flow through said field winding in the opposite direction and thereby enable said D.C. generator to develop said negative voltage at said one output terminal, a command circuit that can develop a variable value command signal, a voltage feedback circuit, a control circuit which receives said command signal from said command circuit and that can simultaneously respond to a signal from said voltage feedback circuit to provide a voltage-modified command signal which will be applied to the field winding of said D.C. generator, said field winding responding to said voltage-modified command signal to cause said electric welder to operate in a constant voltage mode, a subcircuit means that enables said voltage feedback circuit to provide a voltage feedback signal of a given polarity when said D.C. generator is developing said positive voltage at said one output terminal and to provide a voltage feedback signal of said given polarity when said D.C. generator is developing said negative voltage at said one output terminal.

8. An electric welder which comprises output terminals, a generator that can selectively develop a positive voltage or a negative voltage at one of said output terminals, an energizing circuit for the field winding of said generator, a polarity-controlling switch that can be set in one position to enable said energizing circuit to cause current to flow through said field winding in a direction which will enable said generator to develop said positive voltage at said one output terminal, said polarity-controlling switch being adapted to be set in a second position to enable said energizing circuit to cause current to flow through said field winding in the opposite direction and thereby enable said generator to develop said negative voltage at said one output terminal, a command circuit that can develop a variable value command signal, a control circuit which receives said variable value command signal from said command circuit to provide a command signal which will determine the value of the current flowing through said field winding of said generator, and a Hot Start circuit which selectively supplies a current-limiting signal of a fixed polarity to said control circuit which will cause said control circuit to respond to said signal from said Hot Start circuit rather than to said command signal from said command circuit and hence will limit the value of welding current which can be supplied by said output terminals during the initiation of a welding operation to a value corresponding to said signal from said Hot Start circuit regardless of the polarity of said voltage at said one output terminal and also regardless of the value of said command signal supplied by said command circuit.

9. An electric welder as claimed in claim 8 wherein a feedback circuit senses the initiation of a welding operation, wherein the output of said feedback circuit is connected to said control circuit, wherein the output of said control circuit is connected to said polarity-controlling switch whereby said control circuit is connected between said feedback circuit and said polarity-controlling switch, wherein said control circuit can simultaneously respond to said command signal from said command circuit and to a feedback signal from said feedback circuit to supply a feedback-modified command signal to said control circuit, and wherein the output of said Hot Start circuit is connected between said feedback circuit and said polarity-controlling switch.

10. An electric welder which comprises a generator, an internal combustion engine coupled to said generator to drive the armature of said generator, a command circuit which can be set to provide a predetermined command signal, a load-sensing circuit that selectively permits said internal combustion engine to operate at idling speed or causes said internal combustion engine to operate at a higher speed, and a servo system which can sense a condition of the welds to be performed by said welder to vary the current flowing through the field winding of said generator and thereby cause the output of said electric welder to perform said welds in the manner called for by said command signal from said command circuit, said servo system including a feedback circuit which senses said condition of said welds to develop a feedback signal, and means responding to said feedback signal and to said command signal to enable said current flowing through said field winding of said generator to cause the output of said electric welder to perform said welds in the manner called for by said command signal from said command circuit, said load-sensing circuit being connected to said feedback circuit and responding to a predetermined signal from said feedback circuit to cause said internal combustion engine to operate at said higher speed, and said feedback circuit providing said predetermined signal whenever said output of said electric welder is performing a weld, whereby said internal combustion engine will drive said armature at said higher speed to enable said generator to provide welding power and said feedback signal and said command signal will provide the level of welding power called for by said command signal from said command circuit.