Plasma arc torches are widely used in the cutting and marking of materials. A plasma arc torch generally includes an electrode and a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, and passages for arc control fluids (e.g., plasma gas). The torch produces a plasma arc, i.e., a constricted ionized jet of a gas with high temperature and high momentum. Gases used in the torch can be non-reactive (e.g., argon or nitrogen) or reactive (e.g., oxygen or air). During operation, a pilot arc is first generated between the electrode (cathode) and the nozzle (anode). Generation of the pilot arc can be by means of a high frequency, high voltage signal coupled to a DC power supply and the torch or by means of any of a variety of starting methods.
Current plasma arc torches utilize electrodes having either one or two sealing members (e.g., o-rings) for providing fluid seals within the torch during operation, e.g., to prevent liquids and/or gases from entering certain regions of the torch. One example of such a configuration is in U.S. Pat. No. 8,338,740. In most prior art torches, the first contact of the plasma gas with the electrode body is downstream of the swirl ring, so the plasma gas is already swirling when it makes this first contact. What would be beneficial would be an electrode that allows some of the complexity of gas flow to be moved closer to the electrode body, permitting a shorter electrode body to be used in modern complex torches.
USPTO Backgrounds
USPTO Backgrounds