Method and apparatus for automatic gas control for a plasma arch torch

Abstract

A method and apparatus for controlling a gas supply to a plasma arc torch uses a proportional control solenoid valve positioned adjacent the torch to manipulate the gas flow to the torch, thereby extending electrode life during arc transfer and shutdown. Swirl ring design can be simplified and gas supply and distribution systems become less complicated. The invention also allows manipulation of shield gas flow to reduce divot formation when making interior cuts. The system can be controlled with a digital signal processor utilizing a feedback loop from a sensor.

1 - 20 . (canceled) 
   
   
       21 . A system for controlling gas flow to a plasma arc torch, the plasma arc torch including a plasma chamber defined by an electrode and a nozzle, the system comprising:
 a plasma gas supply line for providing a plasma gas flow to the plasma chamber;   an on-off valve for controlling a gas flow through the plasma gas supply line;   a programmable control valve for controlling the gas flow through the plasma gas supply line to the plasma chamber, wherein the plasma gas flow is channeled through the on-off valve and the programmable control valve before reaching the plasma chamber; and   a digital signal processor that provides an output to the on-off valve and the programmable control valve, wherein the on-off valve or the programmable control valve is manipulated based on the output from the digital signal processor.   
   
   
       22 . The system of  claim 21  wherein the programmable control valve comprises a proportional solenoid control valve. 
   
   
       23 . The system of  claim 21  wherein the output is based on a predetermined operating parameter of the plasma arc torch. 
   
   
       24 . The system of  claim 23  wherein the predetermined operating parameter comprises at least one of current, gas flow volume, and gas flow pressure. 
   
   
       25 . The system of  claim 21  further comprising a sensor coupled to the plasma gas supply line that provides a signal to the digital signal processor such that the digital signal processor manipulates the output sent to the programmable control valve based on the signal. 
   
   
       26 . A system for controlling gas flow to a plasma arc torch, the system comprising:
 a plasma gas supply line for channeling a plasma gas flow from a plasma gas supply to the plasma chamber;   a first means for controlling the gas flow channeled through the plasma gas supply line using an on-off valve disposed on the plasma gas supply line;   a second means for controlling the gas flow channeled through the plasma gas supply line using a programmable control valve wherein the plasma gas flow is channeled through the on-off valve and the programmable control valve before reaching the plasma chamber; and   a digital signal processor that provides an output to the on-off valve and the programmable control valve, wherein the on-off valve or the programmable control valve is manipulated based on the output from the digital signal processor.   
   
   
       27 . A method of controlling gas flow to a plasma arc torch during operation of the plasma arc torch, the plasma arc torch including a plasma chamber defined by an electrode and a nozzle, the method comprising:
 channeling a plasma gas flow through a plasma gas supply line to the plasma chamber, such that the plasma gas passes through an on-off valve and a programmable proportional valve before reaching the plasma chamber;   controlling the on-off valve and the programmable control valve using an output from a digital signal processor.   
   
   
       28 . The method of  claim 27  wherein the controlling step further comprises the step of manipulating the on-off valve and programmable control valve to control the plasma gas flow in response to the output received from the digital signal processor. 
   
   
       29 . The method of  claim 27  further comprising coupling a sensor to the plasma gas supply line, such the sensor provides a signal to the digital signal processor and the digital signal processor manipulates the output sent to the programmable control valve based on the signal from the sensor. 
   
   
       30 . The method of  claim 27  further comprising the steps of:
 providing a second gas flow through a shield gas supply line;   manipulating a second on-off valve and a second programmable control valve to control the second gas flow through the shield gas supply line; and   monitoring an operating parameter of the shield gas flow with a sensor coupled to the shield gas supply line.   
   
   
       31 . The method of  claim 27  further comprising the steps of:
 using a signal from a sensor coupled to the plasma gas supply line;   passing the signal to the digital signal processor, the digital signal processor manipulating the signal to generate an output; and   operating the programmable control valve and the on-off valve based on the output generated by the digital signal processor.