Importance

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Abstract

A plasma arc torch comprises relatively displaceable electrode and nozzle components having first and second positions relative to one another in which the electrode respectively contacts the nozzle and is spaced an operating distance therefrom. Arrangements are disclosed for relatively displacing the electrode and nozzle between the first and second positions thereof with a pre-determined force of engagement therebetween in the first position, and without having to interrupt the flow of arc gas and/or the flow of arc current during such relative displacement. A torch start up safety test procedure is performed by sequentially displacing the electrode and nozzle between the two positions thereof, sensing for appropriate open and closed circuit conditions therebetween, and enabling the creation of a pilot arc only when a pre-determined sequence of circuit conditions is sensed. Sequential displacement of the electrode and nozzle together with the application of a pre-determined force of engagement therebetween promotes cleaning of oxides from the area of contact between the electrode and nozzle.

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First Claim