Patent ID: 6093905
Filing Date: 2000-07-25
Classification: B23K,H05H

Abstract:
A process for operating a plasma torch on shut down, the plasma torch having a plasma gas chamber supplied with a plasma gas, an electrode supplied with current for generating a plasma cutting arc by ionization of the plasma gas, and a nozzle disposed in front of the electrode through which the plasma cutting arc extends to a workpiece, in an operational cutting mode of the torch the plasma gas within the plasma gas chamber having a swirl component imparted thereto by a swirl ring, said process comprising:shutting down the plasma torch according to a first shutdown mode for a first predetermined number of pierces attributed to the electrode;controlling the first shutdown mode such that plasma gas flow through the swirl ring and nozzle decrease to zero substantially immediately after termination of arc current to the electrode;after the first predetermined number of pierces, switching to a second shutdown mode for an additional second predetermined number of pierces; andcontrolling the second shutdown mode such that plasma gas flow through the swirl ring and nozzle are sustained after termination of arc current to the electrode.