Attorney, Agent, or Firm—Bell, Seltzer, Park & Gibson
A cutting and welding system is disclosed which includes a metering system for controlling at a location remote from the plasma arc torch the amount of gas and water fed to the plasma arc torch. The system includes at least one torch having an electrode, a nozzle assembly positioned adjacent the discharge end of the electrode, and structure for generating a flow of gas between the electrode and the nozzle assembly to create plasma flow through the bore to a workpiece. A gas line communicates with a source of gas and the plasma arc torch for supplying gas to the torch. A plurality of metering orifices are positioned within the gas flow line in a parallel bank with each other so that the gas may flow through each of the metering orifices. Each metering orifice has a predetermined diameter opening. A gas control valve is mounted adjacent each of the metering orifices within the gas flow line on the upstream side toward the supply of gas. Each gas control valve is operable between open and closed positions for allowing gas flow through a metering orifice upon actuation of the valve. Control means selectively actuates the gas control valves to control gas flow through selected metering orifices to allow a predetermined amount of gas to flow to the plasma arc torch. A method of controlling the cutting current generated to the torch also is disclosed.
46 Claims, 5 Drawing Sheets