Cathode structure of plasma-arc torch

Abstract

A cathode structure of a transition type plasma arc torch, in which a cooling effect is enhanced, and also an amount of consumption of cathode material is reduced by continuously moving a discharge point in the bottom end surface of the cathode during generating of a plasma arc. The cathode structure includes one cathode (21) of small-diameter circular column shape having a minute concave surface portion formed on its bottom end surface symmetrically with respect to its axis, a holder (20) for holding the cathode having such structure that easy and highly effective cooling is possible, and a generating device of lines of magnetic force (23) disposed coaxially with the aforementioned cathode (21) so that a line of magnetic force vector B such that E.times.B.noteq.0 may be fulfilled with respect to a line of electric force vector E generated on the bottom end surface of the cathode, may be generated symmetrically with respect to the axis of the cathode.

Dependencies are inferred from the claim text.