NOZZLE FOR PROVIDING A UNIFORM GAS FLOW IN A PLASMA ARC TORCH

摘要

In a plasma arc cutting torch (10), a flow of plasma gas is bypassed out of a pl asma chamber (14) preferably at an annular gap between a pre-orifice in an inner nozzle piece (36) and an exit nozzle orifi ce in an outer nozzle piece (38). A bypass channel (20) formed between the inner and outer nozzle pieces directs the bypass flow to atmosphere. A metering valve (22) or restricting orifice remote from the gap controls the amount of the bypass flow and delays th e response of changes in the flow parameters in the plasma chamber (14) to changes in the bypass flow. The pre-orifice and nozzl e orifice are positioned and dimensioned to optimize the mass flow velocity and the strength of a vortex-type flow at the pr e-orifice, thereby creating a virtual nozzle immediately below the electrode (30). The gas flow in the plasma chamber (14) is highly unif orm and very steady.