Electrode for plasma arc torch and method of making the same
First Claim
1. An electrode for supporting an arc in a plasma arc torch, said electrode comprising:
- a metallic holder having a front end, and a cavity in said front end; and
an insert assembly mounted in said cavity and comprising;
an emissive insert having an inner face, an outer face, and a bore formed therein, said emissive insert composed of a metallic material having a relatively low work function; and
a non-emissive core positioned within said bore, said non-emissive core having an end portion, wherein said non-emissive core acts to draw heat out of said emissive insert and transfer the heat to said metallic holder.
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Accused Products
Abstract
An electrode for supporting an arc in a plasma arc torch. The electrode includes a metallic holder having a cavity formed in a front end portion. An insert assembly is mounted in the cavity. The insert assembly includes an emissive insert composed of a metallic material having a relatively low work function. The emissive insert has a bore formed therein for securing a non-emissive core. The core has a base portion, which provides an interface between the emissive insert and the holder. The core and base portion act to thermally conduct heat out of the emissive insert so that the service life of the emissive insert is increased by the lowering of the emissive insert'"'"'s operating temperature.
38 Citations
15 Claims
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1. An electrode for supporting an arc in a plasma arc torch, said electrode comprising:
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a metallic holder having a front end, and a cavity in said front end; and
an insert assembly mounted in said cavity and comprising;
an emissive insert having an inner face, an outer face, and a bore formed therein, said emissive insert composed of a metallic material having a relatively low work function; and
a non-emissive core positioned within said bore, said non-emissive core having an end portion, wherein said non-emissive core acts to draw heat out of said emissive insert and transfer the heat to said metallic holder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
further including an overlay portion at said front end, said overlay portion directly contacting said emissive insert so that none of said sleeve is exposed at said front end.
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5. The electrode as defined in claim 4, wherein said sleeve has a peripheral surface, which is bonded to walls of said cavity.
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6. The electrode as claimed in claim 4, wherein said overlay portion of said metallic holder has a thickness of about 0.010 inches.
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7. The electrode as claimed in claim 2, wherein said metallic holder comprises a metal selected from the group consisting of copper and copper alloys.
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8. The electrode as claimed in claim 2, wherein said emissive insert comprises a metal selected from the group consisting of hafnium, zirconium, tungsten, and alloys thereof.
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9. The electrode as claimed in claim 2, wherein said non-emissive core is silver.
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10. A plasma torch comprising:
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an electrode including a metallic elongate tubular holder defining a longitudinal axis and having a front end wall, said transverse front end wall having a substantially planar outer front face which is perpendicular to said longitudinal axis, a cavity formed in said outer front face along said longitudinal axis, and an insert assembly mounted in said cavity and which comprises;
(a) a generally cylindrical emissive insert, having a bore formed therein, disposed coaxially along said longitudinal axis and having an outer end face lying in the plane of said outer front face of said holder, and an inner end face distal to said outer end face, said emissive insert being composed of a metallic material having a relatively low work function so as to be adapted to readily emit electrons upon an electric potential being applied thereto;
(b) a non-emissive core positioned within said bore of said emissive insert, said non-emissive core having a base portion that substantially covers said inner end face of said emissive insert and acts as an interface between said emissive insert and said holder to transfer heat to said holder; and
a nozzle mounted adjacent said transverse front end wall of said electrode and having a bore therethrough which is aligned with said longitudinal axis; and
a power supply, which creates an electrical arc extending from said emissive insert of said electrode through said bore and to a workpiece located adjacent said nozzle. - View Dependent Claims (11, 12)
an overlay portion at said front end wall, said overlay portion directly contacting said emissive insert so that none of said sleeve is exposed at said front end wall.
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12. The plasma torch of claim 10, wherein said non-emissive core and base comprise silver.
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13. A method of fabricating an electrode adapted for supporting an arc in a plasma arc torch, which comprises:
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creating a bore in a substantially cylindrical emissive material;
positioning a non-emissive core, having a base, within said bore to form an insert assembly;
providing a cylindrical metallic blank having a front end and forming a first cavity in said front end;
pressing said insert assembly into said first cavity of said blank so that said base of said core interfaces between said cylindrical emissive material and said blank;
swaging said blank so that said insert assembly is bound to said cylindrical metallic blank;
forming threads on a portion of said blank distal to said front end; and
boring and grooving said blank to provide a second cavity. - View Dependent Claims (14, 15)
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Specification