Thermal Dynamics Corporation

Bruce O Hatch

Richard A Spaulding

Robert D Kneeland

Raymond G Wilkins

This plasma arc torch includes an improved front end assembly to create an improved gouge path when compared with prior art plasma arc gougers. The front end assembly includes a unique secondary gas nozzle for distribution of the secondary gas in a partial radial blanket up to 300.degree. around the plasma. Conventional nozzles distribute the seondary gas in a total, 360 degree, blanket around the plasma. An improved tip design is believed to develop an enlarged plasma stream to further enhance the gouging process.

Plasma arc gouger

A plasma-arc cutting torch housing defines a chamber which has an outlet at the end of the housing. The torch also includes an electrode in the chamber near the outlet and a provision in the chamber for separating the gas flowing towards the outlet of the housing into a primary gas flow adjacent to the electrode for generating a plasma and a secondary gas flow away from the electrode for cooling the torch and the workpiece. The electrode has a centrally disposed bore therethrough for conveying gas. An insert in the workpiece end of the electrode burns away so as to expose the essentially disposed bore therethrough, thereby automatically quenching operation of the plasma arc so as to minimize damage to the torch. In the preferred embodiment, the electrode has a stepped centrally disposed bore which stops short of the insert. In an alternate embodiment, the stepped bore extends through to the insert and accommodating insert bore. A generally cylindrical insulator is also provided for directing the primary and secondary gas flows.

Plasma-arc torch with gas cooled blow-out electrode

A plasma-arc torch is provided having a spring loaded ejector mechanism for expelling the electrode and thereby breaking off electrical contact so as to prevent operation of the torch when necessary parts are not in place.

Spring loaded electrode exposure interlock device

A plasma-arc torch includes an interlock in the form of a sliding gas valve which permits interruption of torch operation by closing off fluid flow through the torch when necessary parts such as the electrode, tip, fluid distributor, and/or cup are not in place.

Plasma-arc torch with sliding gas valve interlock

A plasma-art torch interlock with flow sensing is provided. A flow rate sensor is included within the conduit supplying working fluid to a plasma-arc torch. By sensing an increase in flow rate of the working fluid which is caused by a necessary part being not in place, a control circuit shuts off power to the torch. Pressure in the conduit may also be sensed and the power to the torch shut down if a minimum pressure needed for torch operation is not achieved. In a second embodiment, two conduits are provided to supply fluid to the torch. One conduit supplies the primary working fluid to create the plasma-arc while the other supplies secondary flow for purposes of cooling.

Plasma-arc torch interlock with flow sensing

A plasma-arc torch interlock with pressure sensing is provided. A pressure sensor is included within the conduit supplying working fluid to a plasma-arc torch. By sensing a decrease in pressure of the working fluid which is caused by a necessary part being not in place, a control circuit shuts off power to the torch. In a second embodiment, two conduits are provided to supply fluid to the torch. One conduit supplies the primary working fluid to create the plasma-arc while the other supplies secondary flow for purposes of cooling.

Plasma-arc torch interlock with pressure sensing

The present invention minimizes shock hazard in using a touch start plasma torch. The resistance between the torch tip and the workpiece is compared to a predetermined value set by estimating the resistance between a person's hand to ground under the most unfavorable conditions. In the preferred embodiment, such comparison is performed by supplying an AC voltage to a resistor in series with a torch tip, the resistor having a resistance equal to the predetermined value. The peak voltage at a point in the circuit connection between the resistor and torch tip is sensed and if such peak is less than half of the peak voltage of the AC voltage supplied to the resistor and torch tip, the resistance between the torch tip and ground is less than the predetermined value and a control signal will be generated. A relay will switch on the power supply supplying high voltage between the cathode and the workpiece only when it receives the control signal indicating that the resistance between the torch tip and ground is below the predetermined value.

Torch operation interlock device

In the plasma arc torch of this invention the same gas may be used for generating a plasma and for secondary gas flow for cooling the torch and the workpiece. A torch housing defines a chamber which has an outlet at the end of the housing. The torch also includes an electrode in the chamber near the outlet and means in the chamber for separating the gas flowing towards the outlet of the housing into a primary gas flow adjacent to the electrode for generating a plasma and a secondary gas flow away from the electrode for cooling the torch and the workpiece. In the preferred embodiment, air may be used for both the plasma forming gas and the secondary gas and the electrode has a halfnium insert. The torch has a torch tip adjacent to the electrode and the torch may be started without a pilot arc by touching the workpiece with the torch tip. No standoff between the electrode and the workpiece needs to be maintained and the torch operator simply drags the torch tip on the workpiece resulting in a more accurate cut or weld.

Plasma torch with a common gas source for the plasma and for the

A plasma arc cutting torch housing defines a chamber which has an outlet at the end of the housing. The torch also includes an electrode in the chamber near the outlet and means in the chamber for separating the gas flowing towards the outlet of the housing into a primary gas flow adjacent to the electrode for generating a plasma and a secondary gas flow away from the electrode for cooling the torch and the workpiece. The electrode has a centrally disposed bore therethrough for conveying gas. Inserts in the bore at opposite ends of the electrode burn away so as to expose the centrally disposed bore and thereby automatically quench operation of the plasma arc so as to prevent damage to the torch. In the preferred embodiment, the electrode has a centrally disposed transverse bore and a pair of transverse bores intermediate the central bore and the electrode ends. In an alternate embodiment, the pair of transverse bores are eliminated and gas is conducted by means of an annular gas distributor.

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Lebanon, NH, United States of America

Bruce O Hatch