Abstract: A plasma arc cutting torch cools its nozzle with a water flow between an inner metallic nozzle member and an outer ceramic nozzle member. A set of auxiliary ports formed in the ceramic element each extend from an associated radial channel that directs a portion of the water to the plasma arc where it forms an annular "jet" that constricts the arc. The auxiliary ports are located and sized to provide an enhanced flow of water through the nozzle while maintaining an optimal flow rate through the radial channel. When a gas flow through the cooling passages is used to sense the height of the torch over a workpiece, the gas flow through the auxiliary ports clears residual water from the nozzle to avoid a false height sensing due to an emission of droplets of the water.

Abstract: The positioning method disclosed herein is particularly applicable to a plasma arc cutting torch of the type in which tangential swirl is imparted to an ionizable gas through which the arc discharge takes place. The gas flow is initiated while the torch is in a retracted position and the torch is then advanced toward the workpiece. The vortex pressure is sensed and a signal is generated which is responsive to changes in vortex pressure. The advance of the torch is terminated in response to a change in the signal corresponding to the abrupt drop in the vortex pressure caused by attachment of the vortex to the workpiece.