Importance

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Abstract

An electrode for a plasma arc torch and a method of fabricating the same are disclosed, and wherein the electrode includes a copper holder having a lower end which mounts an emissive insert which acts as the cathode terminal for the arc during operation. Where the torch is used in an oxidizing atmosphere, the copper holder tends to oxidize, and the arc tends to attach to the oxidized copper rather than the insert, which results in the rapid destruction of the holder. To prevent this destruction, the present invention incorporates a sleeve of silver or other metal having a relatively high work function, and which is positioned to surround the insert and form an annular ring on the lower end surface of the holder and thus to surround the exposed end face of the emissive insert. The annular ring serves to prevent arcing from the copper holder, and so that the arc is maintained on the insert.

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First Claim