The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 23, 2000
Filed:
Sep. 10, 1998
Valerian Nemchinsky, Florence, SC (US);
The Esab Group, Inc., Florence, SC (US);
Abstract
The invention relates to an emissive element for supporting an electric arc in a plasma arc torch using an oxygen gas to create the plasma. The element includes a body having a front face for supporting the electric arc which is defined by at least two distinct components formed from different materials. The first component is an emissive material having a low work function for readily emitting electrons in support of the arc and being reactive with the oxygen plasma gas to form an oxide during an operation of the torch. The oxide forms an electrically resistive layer on the front face of the body upon cooling subsequent to the operation of the torch. Hafnium is a preferred material for the first component. The second component comprises a conductive material having an electrical conductivity greater than the oxide layer for supporting the arc during the initiation of a subsequent torch operation at least until the oxide reaches an operating temperature. Silver and copper are preferred materials for the second component. The conductive material provides a conductive path which allows the arc to be supported thereon until the oxide layer reaches an operating temperature, thereby preventing thermal cracking and removal of the oxide layer. Accordingly, electrode start erosion is reduced.