Abstract: A plasma arc torch is disclosed as having an elongated hollow body defining a plenum cavity into which an electrode is mounted. The body has a tip end section which is provided with an arc constricting orifice to permit gas injected into the plenum cavity to issue from the arc constricting orifice. Surrounding the arc constricting orifice on an outer surface of the tip end section is an outwardly extending enlarged head portion. Thus, when an arc is established between the tip and electrode in the vicinity of gas passing through the plenum cavity, an arc is formed which is confined and controlled by the outwardly extending enlarged head portion during operation, for example, on a workpiece. In order to start the arc within the center of the electrode, the electrode has a central part thereof in closest proximity to an inner surface of the body adjacent the arc constricting orifice.

Abstract: In a plasma arc torch having an elongated nozzle with an arc constricting orifice of predetermined diameter and electrical control circuit for regulating the operation of the plasma arc torch, there is provided a visible indicia or light associated with an operator control to assist the operator in the safe operation of the torch. The visible indicia or light includes a by-pass control circuit for energizing the visible indicia or light when the operator control is disconnected. If the torch gets too hot, torch operation is prevented by a thermal disconnect. The visible indicia or light will not be illuminated when the operator control is disconnected, so that the operator will know that the torch is too hot to operate. When the torch cools down, the operator control is disconnected, the visible indicia or light will again be illuminated, indicating that normal operation can be resumed.