Plasma arc cutting torch having extended lower nozzle member

Claim 1

A plasma arc torch which is characterized by the ability to provide beveled cuts while maintaining a relatively short standoff distance from a workpiece, and comprising an electrode defining a discharge end and a longitudinal axis, an upper nozzle member mounted adjacent said discharge end of said electrode and having a first bore therethrough of predetermined length L1 and which is aligned with said longitudinal axis, a lower nozzle member mounted adjacent said upper nozzle member on the side thereof opposite said electrode and having a second bore therethrough of predetermined length L2 which is aligned with said longitudinal axis, said lower nozzle member comprising a cylindrical body portion defining a forward end portion and a rearward end portion and having said second bore extending coaxially therethrough and defining a bore diameter D2, an annular mounting flange positioned on said rearward end portion of said body portion, a frusto-conical surface formed on the exterior of said forward end portion so as to be coaxial with said second bore and having a cone angle of between about 60° and 120°, an axial height H, and a radial dimension R, means for creating an electrical arc extending from said discharge end of said electrode through said first and second bores and to a workpiece located adjacent the side of said lower nozzle member opposite said upper nozzle member, means for generating a vortical flow of a gas between said electrode and said upper nozzle member and so as to create a plasma flow outwardly through said first and second bores and to said workpiece, means for introducing a jet of liquid between said upper and lower nozzle members and so as to envelope said plasma as it passes through said second bore, and wherein length L2 is at least as great as length L1, H is equal to at least about one half L2, L2 is between about 0.16 to 0.60 inches, and D2 is between 0.125 to 0.260 inches.