Plasma-transferred-arc torch construction

A plasma-transferred-arc torch construction comprising an elongate central cathode subassembly having a downstream-directed cathode-discharge end and a radial mounting shoulder at an upstream mounting region thereof, an elongate insulating sleeve forming part of said subassembly downstream from said shoulder;

• a tubular mounting subassembly including a radially extending base of insulating material at said region and having a central bore through which the upstream end of said cathode assembly extends, with said shoulder in axial reference to said base;
• and an annular anode subassembly adapted for axial reference to said base via said sleeve and having a bore removably supported by said sleeve, said anode subassembly being convergent at its downstream end for axially overlapped radially spaced coaction with said cathode-discharge end;
• said tubular mounting subassembly including elongate outer tubular structure fully surrounding said cathode and anode subassemblies and having a convergent annular downstream end overlapping but in spaced relation to the convergent end of said anode subassembly, said outer tubular structure having axially adjustable threaded reference to said base, and angularly spaced insulating spacer elements of limited angular extent in the space between said convergent ends and adapted for insulated compressional loading upon threaded adjustment of said outer tubular structure to retain the base reference of both said cathode and anode subassemblies, and said anode subassembly including shielding-gas supply-passage means communicating with the convergent space between said convergent ends, whereby said convergent space serves both as a manifold for shielding-gas flow and as a convergent nozzle for discharge of shielding gas around an externally transferred arc discharge downstream from and between said cathode and anode subassemblies.