Method and circuit for protecting plasma nozzle
AssigneeThe Lincoln Electric Company
InventorEdward A. Enyedy
Life of this patent
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Abstract
A system, method and circuit for protecting a plasma nozzle of the type including an electrode within the nozzle and a paper supply for creating an arc between the electrode and nozzle for establishing a plasma issuing from the nozzle toward a workpiece, which system, method and circuit detects when the nozzle contacts or drags along the workpiece and shifts the power supply to a low current operating mode if the power supply is in a high current operating mode.
Claims37
A system for protecting the nozzle of a plasma torch comprising a nozzle with a plasma outlet opening and an internal electrode chamber and an elongated electrode in said chamber and spaced from said nozzle a distance defining an annular gas passage means for allowing flow of a gas through said passage means and through said outlet for impingement against a workpiece below said outlet as an electrical power supply maintains an arc current to said electrode for sustaining said plasma from said nozzle to said workpiece, said system comprising:
- current control means for selectively shifting said power supply between a first high arc current mode and a second low arc current mode greater than zero, means for detecting contact of said nozzle with said workpiece and means responsive to said detection for holding said current control means in said second mode as long as said contact is detected.
A method of protecting the nozzle of a plasma torch of the type comprising a nozzle with a plasma outlet opening and an internal electrode chamber and an elongated electrode in said chamber and spaced from said nozzle a distance defining an annular gas passage means for allowing flow of a gas through said passage means and through aid outlet for imingement against a workpiece below said outlet as an electrical power supply maintains an arc current to said electrode for sustaining said plasma from said nozzle to said workpiece and current control means for selectively shifting said power supply between a first high arc current mode and a second low arc current mode greater than zero, said method comprising the steps of:
- (a) detecting contact of said nozzle with said workpiece;
- and,
- (b) maintaining said current control means in said second mode in response to said contact detection as long as said contact is being detected.
A method for protecting the nozzle of a plasma torch of the type comprising a nozzle with a plasma outlet opening and an internal electrode chamber and an elongated electrode in said chamber and spaced from said nozzle a distance defining an annular gas passage means for allowing flow of a gas through said passage means and through said outlet for impingement against a workpiece below said outlet and said nozzle as an electrical power supply maintains an arc current to said electrode for sustaining said plasma from said nozzle to said workpiece and current control means for selectively shifting said power supply between a first high arc current mode and a second low arc current mode greater than zero, said method comprising the steps of:
- (a) sensing the voltage of said nozzle;
- (b) comparing said nozzle voltage with a reference voltage;
- and,
- (c) causing said torch to be operated in said second mode when said sensed nozzle voltage is within a selected range of said reference voltage.
A circuit for protecting the nozzle of a plasma arc torch as it operated at a high current level, said circuit comprising means for sensing the voltage at said nozzle, means for comparing said nozzle voltage with a reference voltage and means for limiting the arc current to said torch to a current value greater than zero when said nozzle voltage is within a selected range of said reference voltage.
Dependencies are inferred from the claim text.