HYBRID NON-TRANSFERRED-ARC PLASMA TORCH SYSTEM AND METHOD OF OPERATING SAME

摘要

A hybrid non-transferred-arc plasma torch system (2) utilizes an arc plasma torch (4) whose hollow body (10) carries internally a cathode (11) aligned with a relatively small diameter nozzle (12) which functions under a created arc to issue and arc flame (19) through the nozzle (12) with a plasma gas (32) applied to the chamber (14) of the hollow body (10). An external anode (30) electrically isolated from the cathode (11) and the transferred-arc plasma torch body (10) coaxial with the nozzle (12) and spaced downstream thereof has an active anode surface (47) of relatively large area radially remote from the axis of the arc flame (19) issuing from the transferred-arc torch with the external anode positioned such that the arc flame (19) extends freely beyond the active anode surface (47) with a reverse flow of electrons (46) completing the circuit from the arc flame (19) beyond the anode surface back to that anode surface (47). The external anode (30) is of cup-shaped configuration extending axially beyond the torch hollow body (10) to define a secondary gas chamber (42) about the arc-flame (19) exiting from the torch body nozzle (12) to constrict the arc (19) as it exits from the exterior anode passage (43) and that arc portion which freely extends beyond the active exterior anode surface (47).