US 4,791,268 A · Arc plasma torch and method using contact starting

Abstract

An arc plasma torch includes a moveable cathode and a fixed anode which are automatically separated by the buildup of gas pressure within the torch after a current flow is established between the cathode and the anode. The gas pressure draws a nontransferred pilot arc to produce a plasma jet. The torch is thus contact started, not through contact with an external workpiece, but through internal contact of the cathode and anode. Once the pilot arc is drawn, the torch may be used in the nontransferred mode, or the arc may be easily transferred to a workpiece. In a preferred embodiment, the cathode has a piston part which slidingly moves within a cylinder when sufficient gas pressure is supplied. In another embodiment, the torch is a hand-held unit and permits control of current and gas flow with a single control.

Claims23

Dependent claims

A method for starting to operate an arc plasma torch having a body with a plasma exit port at one end and an anode and a cathode that are movable relative to one another within the torch body along a first direction, comprising:

resiliently urging the cathode into electrical contact with the anode,
providing a surface transverse to said first direction that is operatively coupled with movable one of said cathode and anode,
blocking said exit port with said cathode when said cathode is in contact with said anode
providing a gas chamber within said torch body between said transverse surface and said cathode and said anode that is sealed by said blocking,
causing an electrical current to flow within the torch and from said cathode to said anode,
supplying a pressurized gas to the interior of the torch at said chamber, and
directing at least some of said gas in said chamber to act on said transverse surface to separate said anode from said cathode forcibly and against the force of said resilient urging whereby an electric arc is generated between said anode and said cathode and whereby said exit port is opened.

4 more elements

Dependencies are inferred from the claim text.

Arc plasma torch and method using contact starting

Life of this patent

Arc plasma torch and method using contact starting

Life of this patent

Abstract

Claims23