Esab Welding Products, Inc.

Union Carbide Corporation

L-tec Company

Wayne S Severance, Jr

Tommie Z Turner

Philip K Higgins

Larry Wade Stokes

David G Anderson

Peter Budai

George T Rogers

A cutting and welding system is disclosed which includes a metering system for controlling at a location remote from the plasma arc torch the amount of gas and water fed to the plasma arc torch. The system includes at least one torch having an electrode, a nozzle assembly positioned adjacent the discharge end of the electrode, and structure for generating a flow of gas between the electrode and the nozzle assembly to create plasma flow through the bore to a workpiece. A gas line communicates with a source of gas and the plasma arc torch for supplying gas to the torch. A plurality of metering orifices are positioned within the gas flow line in a parallel bank with each other so that the gas may flow through each of the metering orifices. Each metering orifice has a predetermined diameter opening. A gas control valve is mounted adjacent each of the metering orifices within the gas flow line on the upstream side toward the supply of gas. Each gas control valve is operable between open and closed positions for allowing gas flow through a metering orifice upon actuation of the valve. Control means selectively actuates the gas control valves to control gas flow through selected metering orifices to allow a predetermined amount of gas to flow to the plasma arc torch. A method of controlling the cutting current generated to the torch also is disclosed.

Plasma arc cutting system having fluid metering and power control systems

A plasma arc torch used in underwater cutting is disclosed. The plasma arc torch includes a torch body having a front end of substantially cylindrical configuration, and an electrode supported by the torch body and defining a discharge end extending toward the front end. A nozzle is mounted on the front end of the torch body adjacent the front discharge end of the electrode, and has a bore through which plasma is ejected. A cylindrical support body is secured onto the outer surface of the torch body and extends in spaced relation from the torch body outer surface toward the front end and forms an annular opening. A cylindrical sleeve has a rear portion received within the annular opening of the cylindrical support body and extends in spaced relation along the front end of the torch body to define an annular air chamber extending along the front end and forming an annular outlet opening positioned adjacent the nozzle. A high velocity gas is injected into the annular air chamber. The high velocity gas swirls downward through the outlet opening for generating a protective air curtain for the plasma during underwater torch operation.

Plasma arc torch used in underwater cutting

Nozzle for plasma arc torch

A plasma arc torch is disclosed and includes an electrode defining a discharge end and a longitudinal axis. A nozzle base, formed of metallic material, is positioned adjacent the discharge end of the electrode. The nozzle base has an outer, annular configured mounting surface and a frusto-conical surface positioned adjacent the mounting surface and tapering toward the longitudinal axis in a direction away from the electrode. A lower nozzle member, formed of metallic material, is secured onto the nozzle base mounting surface on the side opposite the electrode, and includes an interior surface spaced from the outer frusto-conical surface of the nozzle base to form a water passage. A ceramic insulator is secured onto the outer surface of the lower nozzle member and extends substantially along that surface for preventing double arcing and insulating the lower nozzle member from heat and plasma generated during torch operation. In a one embodiment the ceramic insulator is secured by means of glue. In another embodiment, the ceramic insulator is secured by an O-ring.

Plasma arc torch having improved nozzle assembly

An electrode for a plasma arc torch and a method of fabricating the same are disclosed, and wherein the electrode includes a copper holder having a lower end which mounts an emissive insert which acts as the cathode terminal for the arc during operation. Where the torch is used in an oxidizing atmosphere, the copper holder tends to oxidize, and the arc tends to attach to the oxidized copper rather than the insert, which results in the rapid destruction of the holder. To prevent this destruction, the present invention incorporates a sleeve of silver or other metal having a relatively high work function, and which is positioned to surround the insert and form an annular ring on the lower end surface of the holder and thus to surround the exposed end face of the emissive insert. The annular ring serves to prevent arcing from the copper holder, and so that the arc is maintained on the insert.

Electrode for plasma arc torch and method of fabricating same

A process for starting a plasma arc torch is disclosed which minimizes the oxidation of the electrode to thereby extend the life of the electrode. A flow of non-oxidizing gas is first generated between the discharge end of the torch electrode and the nozzle assembly of the torch. A pilot arc then is created between the discharge end of the electrode and the nozzle assembly. The pilot arc is transferred and the flow of non-oxidizing gas is terminated. A flow of oxidizing gas then is generated for plasma formation.

Plasma arc torch starting process having separated generated flows of

The invention is a method and apparatus that comprises supplying a mixture of gases to a constricted plasma arc. The mixture comprises a gas that will sustain the plasma arc at the lower voltages typical of electric-arc welding and in the absence of a plasma and a gas which provides good heat transfer characteristics. The relative proportion of the gas that will sustain the plasma arc at the lower voltages present in the mixture is large enough to support the plasma arc, and the relative proportion of gas having good heat transfer charactristics present in the mixture is small enough to prevent failure of the arc at the lower voltage. A voltage drop is maintained which is high enough to maintaing the plasma arc using the gas mixture while low enough to operate at a substantially constant current using a low voltage constant current power supply.

System for low voltage plasma arc cutting

A plasma arc process and a combination plasma arc torch and nozzle assembly in which the arc plasma gas composition contains at least 50% oxygen. An oxygen containing reactive gas is passed through a gap between a first and second nozzle body of a nozzle assembly having a first and second arc constricting passageway adapted to constrict the arc plasma. The width of the gap is of a critical dimension to permit a tungsten electrode to be used without suffering from rapid electrode erosion.

Growing community of inventors

Florence, SC, United States of America

Wayne S Severance, Jr