Electrode for plasma arc torch having channels to extend service life

Claim 3

The method as defined in claim 1 wherein the insert is separated from physical contact with the holder by an annular sleeve composed of a material having a work function greater than the work function of the insert.

Claim 4

An electrode adapted for supporting an arc in a plasma arc torch and comprising: a tubular holder defining a longitudinal axis and comprising a discharge end; an endwall closing the discharge end of said holder and having an opening formed therein extending axially at least partially therethrough and coaxially with the longitudinal axis defined by said holder; an emissive insert mounted within the opening; and a plurality of open channels formed in the holder which terminate adjacent said endwall, whereby said channels define a corresponding plurality of passageways for directing a portion of a stream of gas along said channels and radially inwardly across said endwall.

Claim 5

An electrode adapted for supporting an arc in a plasma arc torch and comprising: a tubular holder defining a longitudinal axis and comprising a discharge end; an endwall closing the discharge end of said holder and having an opening formed therein extending axially at least partially therethrough and coaxially with the longitudinal axis defined by said holder; an emissive insert mounted within the opening; and a plurality of open channels formed in the holder which terminate adjacent said endwall, whereby said channels define a corresponding plurality of passageways for directing a portion of a stream of gas along said channels and radially inwardly across said endwall.

Claim 6

The electrode of claim 3 wherein said holder comprises a metal selected from the group consisting of copper and copper alloys.

Claim 7

The electrode of claim 3 wherein the insert comprises a metal selected from the group consisting of hafnium, zirconium, tungsten and alloys thereof.

Claim 8

The electrode of claim 3 wherein said holder is composed of a material having a work function greater than the work function of the insert.

Claim 9

The electrode of claim 3 wherein said channels formed in the holder which terminate adjacent said endwall each comprise a pair of opposed sidewalls, at least one of the sidewalls extending along a portion of a radial which intersects the longitudinal axis defined by said holder.

Claim 10

The electrode of claim 7 wherein the opposed sidewalls form an acute angle.

Claim 11

The electrode of claim 3 wherein said endwall comprises an annular sleeve separating the insert from physical contact with said holder.

Claim 12

The electrode of claim 9 wherein the annular sleeve is composed of a material having a work function greater than the work function of the insert.

Claim 13

The electrode of claim 9 wherein the annular sleeve is composed of a material having a work function greater than the work function of the insert and greater than the work function of said holder.

Claim 14

The electrode of claim 9 wherein the annular sleeve is composed of metals selected from the group consisting of copper, silver, gold, platinum, rhodium, iridium, palladium, nickel and alloys thereof.

Claim 15

The electrode of claim 9 wherein the annular sleeve has a radial thickness of at least 0.1 inches.

Claim 16

The electrode of claim 3 wherein the discharge end of said holder comprises a frustoconical surface and wherein said channels are formed in said frustoconical surface.

Claim 17

A plasma arc torch comprising: a torch body; an electrode secured to said torch body, said electrode comprising: an elongate tubular holder defining a longitudinal axis and comprising a discharge end; an endwall closing the discharge end and having an opening formed therein extending axially at least partially therethrough and coaxially with the longitudinal axis defined by said holder; an emissive insert mounted within the opening; and a plurality of open channels formed in the holder which terminate adjacent said endwall; a nozzle secured to the torch body and having a bore therethrough aligned with the longitudinal axis defined by said holder, the bore positioned opposite the discharge end of said holder for constricting a plasma arc; means for generating an electrical arc extending from said emissive insert in the direction of a workpiece; and means for generating a flow of gas between said electrode and said nozzle so as to create a plasma flow through the bore of said nozzle in the direction of the workpiece, whereby a portion of the flow of gas is directed by said channels and said nozzle radially inwardly across said endwall to maintain said endwall substantially free of erosion deposits and to thereby extend the useful service life of the torch.

Claim 18

A plasma arc torch comprising: a torch body; an electrode secured to said torch body, said electrode comprising: an elongate tubular holder defining a longitudinal axis and comprising a discharge end; an endwall closing the discharge end and having an opening formed therein extending axially at least partially therethrough and coaxially with the longitudinal axis defined by said holder; an emissive insert mounted within the opening; and a plurality of open channels formed in the holder which terminate adjacent said endwall; a nozzle secured to the torch body and having a bore therethrough aligned with the longitudinal axis defined by said holder, the bore positioned opposite the discharge end of said holder for constricting a plasma arc; means for generating an electrical arc extending from said emissive insert in the direction of a workpiece; and means for generating a flow of gas between said electrode and said nozzle so as to create a plasma flow through the bore of said nozzle in the direction of the workpiece, whereby a portion of the flow of gas is directed by said channels and said nozzle radially inwardly across said endwall to maintain said endwall substantially free of erosion deposits and to thereby extend the useful service life of the torch.

Claim 19

The torch of claim 15 wherein said endwall comprises an annular sleeve separating said insert from physical contact with said holder.

Claim 20

The torch of claim 15 wherein the discharge end of said holder comprises a frustoconical surface and the bore of said nozzle includes a frustoconical surface which conforms to and is spaced from said frustoconical surface of the discharge end of said holder.

Claim 21

The plasma torch as defined in claim 17 wherein said channels are formed in the frustoconical surface of said discharge end of said holder.