David M Small

US Patent:

6703581, Mar 9, 2004

Filed:

Feb 27, 2001

Appl. No.:

09/794540

Inventors:

Joseph P. Jones - Lebanon NH
Roger W. Hewett - Plainfield NH
Kevin D. Horner-Richardson - Cornish NH
David A. Small - Strafford VT

Assignee:

Thermal Dynamics Corporation - West Lebanon NH

International Classification:

B23K 1000

US Classification:

21912157, 21912154, 21912152, 21912159

Abstract:

A contact start plasma torch and method of starting the torch includes a negatively charged cathode body and a positively charged anode body. A conductive element in the torch is constructed of an electrically conductive material and is free from fixed connection with the cathode body and the anode body. The torch is operable between an idle mode wherein the conductive element provides an electrically conductive path between the cathode body and the anode body and an pilot mode wherein a pilot arc is formed between the conductive element and at least one of the cathode body and the anode body. The pilot arc is blown by working gas flowing through the torch toward an exit orifice of the torch whereby the working gas is exhausted from the torch in the form of an ionized plasma.