Hybrid non-transferred-arc plasma torch system and method of operating same

A hybrid non-transferred-arc plasma torch system comprising:

• a plasma torch,
• said torch including a plasma torch body,
• said body being hollow and having a chamber therein opening to the body exterior through a relatively small diameter nozzle,
• passage means for supplying a plasma gas to said chamber,
• a cathode carried by said plasma torch body coaxial with said nozzle and functioning under a created arc to issue an arc flame through the nozzle,
• an exterior anode electrically isolated from said cathode and the plasma torch body coaxial of said nozzle and spaced downstream therefrom,
• said exterior anode having a passage therethrough axially aligned with said nozzle and an active anode surface surrounding said passage of relatively large area radially remote from the axis of the arc flame issuing from said torch.
• means for initially subjecting said cathode and said anode of said plasma torch body to a potential difference sufficient to create an arc therebetween, and for subsequently subjecting said cathode and said exterior anode to a potential difference to cause said arc to extend through said exterior anode passage,
• and wherein said torch and said anode are positioned such that said arc flame extends to and freely beyond the active anode surface such that a reverse flow of electrons completes the circuit from the arc flame beyond the anode surface back to said active anode surface, wherein said exterior anode comprises a cup-shaped member fixed to said torch body and extending axially beyond the body at said end bearing said nozzle to define a secondary gas chamber about the arc-flame exiting from the torch body nozzle and passing through said exterior anode passage, and means for supplying a secondary gas to said secondary gas chamber such that the secondary gas forms a sheath of non-ionized gas between the arc column and the wall of the exterior anode defining said passage therethrough, axially aligned with said torch body nozzle which functions to constrict the arc of said hybrid non-transferred-arc plasma torch system through said exterior anode passage and the portion of the arc which extends freely beyond the active anode surface.