Apparatus and process for cooling a plasma arc electrode

An electrode for a plasma arc cutting torch having a torch body, an anode secured on the torch body with a central outlet orifice for said plasma arc, resilient means mounted within the body that urges said electrode into electrical connection with said anode, and means for directing a flow of pressurized plasma gas to a plasma chamber defined by said electrode, said anode, and said torch body to produce a liquid force within said plasma chamber that separates said electrode from said anode against the force of said resilient means, said electrode comprising,

• a body portion that seals said outlet orifice when said electrode and said anode are in electrical connection,
• a shoulder portion having an outer side surface in a closely spaced, sliding engagement with said torch body that also provides a seal against a flow of the pressurized gas from the plasma chamber along said outer side surface, and
• a cooling gas flow passage formed in said electrode and extending between a first end of said electrode open to said plasma chamber and a second end open to a region sealed from said plasma chamber by said shoulder portion,
• said cooling gas flow passage being dimensioned and configured to restrict the flow of the pressurized gas therethrough to maintain a substantial pressure differential between the gas pressures at the ends of said passage while at the same time allowing a sufficient cooling gas flow through said passage to cool said electrode.

A process for cooling an electrode mounted in a torch body of a plasma arc torch at a plasma chamber also defined by an anode mounted on the torch body, comprising

• directing a flow of pressurized plasma gas to said plasma chamber,
• forming a gas flow passage through said electrode extending from said plasma chamber to a region sealed from said chamber and at a lower gas pressure than said plasma chamber, and
• diverting a portion of said pressurized gas flow through said passage to cool said electrode, and
• restricting said diverted flow through said passage to produce a substantial pressure drop along the length of said passage.

In a plasma arc torch having (i) a torch body, (ii) an anode supported on the body, and (iii) a cathode mounted for an axial sliding movement within the body, said cathode, anode and torch body defining a plasma chamber, the improvement comprising

• resilient means mounted within the body that urges said anode and said cathode into electrical contact,
• means for directing a pressurized flow of a plasma gas to said plasma chamber to produce a fluid force within said plasma chamber that separates said anode from said cathode,
• a volume opposite the chamber that is vented to atmosphere which is at a substantially reduced pressure as compared to the gas pressure in said plasma chamber, and
• a cooling gas flow passage formed in said cathode that is in fluid communication between said plasma chamber and said volume, said passage being dimensioned and configured to restrict a gas flow therethrough to a sufficient degree to maintain a pressure differential between the plasma gas in said plasma chamber and the plasma gas in said volume, while at the same time passing a sufficient gas flow to said volume to cool the cathode.