Importance

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Abstract

A plasma arc cutting torch, particularly one operating in the 0-200 ampere range, has a shield mounted at its lower end adjacent a workpiece to block splattered molten metal from reaching a nozzle of the torch. The shield is electrically insulated, preferably by mounting it on an insulating ring that is itself secured on a cap screwed onto the torch body. A secondary gas flow through the torch passes through the space between the nozzle and the shield to provide cooling. Bleed ports in the shield allow an enhanced flow rate with the remaining flow being at a rate, in conjunction with the size of an exit orifice in the shield, to stabilize the plasma arc. The bleed ports are outwardly angled away from the arc. Canted ports in the secondary gas flow path, but before the bleed ports, produce a swirling of the gas flow which enhances the quality of the cut. A flow control system, preferably one utilizing parallel branch conduits and control valves, allows the selection of flow rates for the secondary gas depending on the cutting conditions.

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First Claim