Abstract: A plasma arc torch with improved sealing of connections between fluid passages of adjoining parts of the torch, means for reducing current leakage through a control fluid, and an improved pilot arc electrical assembly, includes a main torch body and an insulator body which abut and each of which has a plasma gas passage and a control fluid passage which extend to the abutting end faces of the bodies and are aligned thereat. Connections between the aligned plasma gas passages are made via coupling tubes each having a first portion inserted into a receiving portion of the passage in the main torch body and a second portion inserted into a receiving portion of the passage in the insulator body. Each inserted portion includes a pair of O-rings spaced apart along the length of the tube for sealing the connection.

Abstract: An electrode for a plasma arc torch comprises a copper holder having a lower end which mounts an emissive element serving as the cathode terminal for the arc during operation. A relatively non-emissive separator formed of silver alloyed with 0.5 to 4 percent of copper or other metals surrounds the emissive element and separates the emissive element from the copper holder at the exposed end face of the electrode. The separator serves to prevent the arc from detaching from the emissive element and attaching to the copper holder.

Abstract: An electrode for a plasma arc torch comprises a copper holder having a lower end which mounts an emissive element serving as the cathode terminal for the arc during operation. A relatively non-emissive separator formed of silver alloyed with 0.5 to 4 percent of copper or other metals surrounds the emissive element and separates the emissive element from the copper holder at the exposed end face of the electrode. The separator serves to prevent the arc from detaching from the emissive element and attaching to the copper holder.

Abstract: A plasma arc torch is provided with an extended water-injection nozzle assembly characterized by the ability to produce a bevel cut or weld, and a cut or weld within a concavity on the top surface of a workpiece. The nozzle assembly includes a nozzle base, a swirl ring and an outer shell press-fit together to center and maintain the concentricity of the water-injection bore of the outer shell relative to the gas-constricting bore of the nozzle base. A radially exterior, frusto conical surface of the nozzle base and a radially interior, frusto conical surface of the outer shell define a fluid passageway therebetween for communicating a vortical flow of cooling fluid from an external source to the water-injection bore of the outer shell. Preferably, the vortical flow of cooling fluid further constricts the plasma arc extending outwardly from the electrode and along the longitudinal discharge axis defined by the plasma arc torch in the direction of the workpiece.