Voltage overload arrester

Claim 2

A voltage overload arrester as defined in claim 2 wherein the outer peripheral layer is composed of a mixture including about 30 percent to 90 percent by weight of nickel, and up to about 20 percent by weight of magnesium oxide.

Claim 3

A voltage overload arrester as defined in claim 1 wherein the material having a relatively high thermal electron-emission ability in the outer peripheral layer is thorium oxide.

Claim 4

A voltage overload arrester comprising, a gas-tight housing, a pair of shaped electrode members positioned in working relation within the housing, said electrodes each having a work surface in spaced facing relation to each other, and an outer peripheral layer composed of a substantially uniform mixture of a material consisting essentially of 10 percent to 50 percent by weight of thorium oxide, 30 percent to 90 percent by weight nickel and 0 percent to 20 percent by weight magnesium oxide sintered onto at least one of the electrode work surfaces.

Claim 5

A voltage overload arrester as defined in claim 5 wherein the material of the mixture is in a powdered form and the thorium oxide powder has an average grain size ranging from about 1 Mu m to about 50 Mu m, the nickel powder has an average grain size ranging from about 1 Mu m to 50 Mu m, and the magnesium oxide powder has an average grain size ranging from about 0.2 Mu m to about 10 Mu m.

Claim 6

A voltage arrester as defined in claim 5 wherein the material of the mixture is in a powdered form and the thorium oxide powder has an average grain size of about 30 Mu m, the nickel powder has an average grain size of about 10 Mu m and the magnesium powder has an average grain size of about 2 Mu m.

Claim 7

A voltage overload arrester comprising, a housing composed of an insulating material having a pair of openings formed therein, electrodes extending through the openings of said housing and positioned adjacently spaced from one and her and having work surfaces in spaced facing relation to each other, a means sealing said electrodes to said housing to form a gas-impermeable housing, said electrodes protruding beyond said means to form contact points, and an outer peripheral layer sintered onto at least one of said work surfaces, said layer being composed of a mixture of a material having a relatively high thermal electron-emission ability selected from the group consisting essentially of a rare earth metal and thorium oxide, and another material including at least nickel said materials being a powder having an average grain size below abouT 50 m.

Claim 8

A voltage overload arrester as defined in claim 8 wherein the outer peripheral layer is composed of a substantially uniform mixture containing about 10 percent to 50 percent by weight thorium oxide, 30 percent to 90 percent by weight nickel and up to 20 percent by weight magnesium oxide.

Claim 9

A voltage overload arrester as defined in claim 8 wherein the outer peripheral layer is composed of a substantially uniform mixture containing about 10 percent to 50 percent by weight of thorium oxide powder having an average grain size of about 30 percent Mu m, about 30 percent to 90 percent by weight of nickel powder having an average grain size of about 10 Mu m and up to about 20 percent by weight of magnesium oxide powder having an average grain size of about 2 Mu m.