Plasma torch for micro-plasma welding

Claim 1

In a plasma welding torch particularly adapted for micro-plasma welding, said torch having a hollow cylindrical torch housing; a pin-shaped electrode terminating in a point; means for mounting the electrode in the torch housing and insulating it therefrom; a plasma gas nozzle being disposed adjacent the point of the electrode and having a cooling chamber formed therein and a plasma channel for the plasma to pass therethrough; an inert gas nozzle being arranged concentrically around the plasma nozzle on said housing; and separate means for supplying plasma gas to the plasma nozzle, inert gas to the inert gas nozzle, welding current to the electrodes, and a cooling agent to the cooling chamber the improvements comprising said pin-shaped electrode having an enlarged diameter cylindrical surface tapering to said point; the plasma channel of the plasma nozzle having a raised annular edge at an end facing toward the point of the electrode so that the closest proximity between the electrode and the nozzle is between the annular edge and the point; cooling means for cooling the electrode including means contacting a portion of the cylindrical surface of the electrode; and said means for mounting the electrode including a passage in a member for receiving the electrode, said passage having a conical portion expanding into a threaded portion, and means for sealing said electrode in said passage, said means for sealing including a conical metal ring having small tolerances disposed in the conical passage, a threaded bushing threaded into said threaded portion to force the conical metal ring into sealing engagement with the conical portion and the cylindrical surface.