Plasma torch nozzle with improved cooling gas flow

An improved plasma torch assembly comprising:

• a nozzle and a retaining member;
• said nozzle comprising a substantially barrel-shaped nozzle body having a longitudinal opening therethrough for directing the flow of a gas for a plasma arc from rearward portions of said body downstream to forward portions of said body, and then out of said forward portions to form a plasma arc in the presence of a sufficient electrical potential difference;
• said nozzle body further comprising
• a rear section for which the outer surface portions diverge with respect to the downstream direction,
• a center section for which the outer surface portions are cylindrical with respect to the downstream direction, and
• a forward section for which the outer surface portions converge with respect to the downstream direction so that said outer surface of said nozzle body changes direction at said forward section for creating a pressure gradient where said center section meets said forward section when a gas flows from said center section to said forward section in which the pressure gradient tends to hold the gas along said outer surface as it flows, and so that the gas converges at said face of said nozzle body;
• and
• said retaining member comprising means for positioning and maintaining said nozzle in a torch assembly, and means for directing a flow of cooling gases against said outer surface of said nozzle body.

A plasma arc torch comprising:

• a substantially cylindrical hollow outer insulator;
• an electrode body carried concentrically within said insulator;
• an electrode in electrical contact with said electrode body;
• a nozzle retaining member carried by portions of said outer insulator;
• and
• a nozzle carried by said retaining member and in adjacent surrounding relationship to said electrode, said nozzle comprising a substantially barrel-shaped nozzle body having a longitudinal opening therethrough for directing the flow of a gas for a plasma arc from rearward portions of said body downstream to forward portions of said body, and then out of a tip at said forward portions to form a plasma arc in the presence of a sufficient electrical potential difference;
• said nozzle body further comprising
• a rear section for which the outer surface portions diverge with respect to the downstream direction,
• a center section for which the outer surface portions are cylindrical with respect to the downstream direction, and
• a forward section for which the outer surface portions converge with respect to the downstream direction so that said outer surface of said nozzle body changes direction at said forward section for creating a pressure gradient where said center section meets said forward section when a gas flows from said center section to said forward section in which the pressure gradient tends to hold the gas along said outer surface as it flows, and so that the gas converges at said face of said nozzle body.