Raychem Limited

Gary H Wiseman

Mark S Thompson

Ryan W Dupon

Douglas J Musolf

Adam C Tanous

Ronald James Mosso

Jeffrey A Bennett

William M Robinson

Edward S Sherman

Adam S Tanous

John T Fossett

A sealed vented surge arrester and method of manufacture is described wherein the valve elements are held under compressive loading while strength members including a moisture sealing void filling compound are pressed fit from the sides of the unit with a shed applied over it. The design achieves all the desirable features of tubular strength members with an ease of manufacture from utilizing half-shell or more members which can be applied from the sides along the longitudinal axis of the valve elements during manufacture to provide better void filling between the structural members and the valve elements.

Electrical surge arrester

A metal oxide dielectric dense body, comprising (I) grains having a predominant crystalline phase (a) a primary metal oxide selected from the group consisting of silicon and magnesium oxide and (b) optionally a secondary metal oxide selected from the group consisting of aluminum and zinc oxide and (II) between about 1 and about 20 atom % bismuth, vanadium, or boron oxide or combination thereof, discontinuously located at the boundaries of the crystalline grains or as inclusions in the crystalline grains, the atom %'s based on the total atoms of bismuth, vanadium, boron, silicon, magnesium, aluminum, and zinc. The dense body has a density which is at least 95% of theoretical.

Metal oxide dielectric dense bodies, precursor powders therefor, and

A metal oxide dielectric dense body, comprising (I) grains having a predominant crystalline phase (a) a primary metal oxide selected from the group consisting of silicon and magnesium oxide and (b) optionally a secondary metal oxide selected from the group consisting of aluminum and zinc oxide and (II) between about 1 and about 20 atom % bismuth, vanadium, or boron oxide or combinations thereof, discontinuously located at the boundaries of the crystalline grains or as inclusions in the crystalline grains, the atom %'s based on the total atoms of bismuth, vanadium, boron, silicon, magnesium, aluminum, and zinc. The dense body has a density which is at least 95% of theoretical.

This invention provides a process for making metal oxide varistor precursor powder comprising (a) dissolving soluble precursors of the additive metal oxides, e.g. bismuth nitrate as precursor for bismuth oxide, in an aqueous solution, (b) forming a suspension or slurry in the aqueous solution of a powder of the desired primary metal oxide, e.g. zinc oxide, having the desired particle size, (c) adding a precipitating reagent to convert the additive metal from the soluble precursor form to the oxide or hydrous oxide form and precipitate the oxide or hydrous oxide in the presence of the primary metal oxide particles, (d) removing water and by-product salts to form a powder. The resulting varistor precursor powder contains smaller particles of the additive metal oxides evenly distributed throughout larger particles of the primary metal oxide. Varistors prepared from the resulting powder can be sintered at temperatures lower than conventionlly used, for example 900.degree. C.-1000.degree. C. and the resulting varistors exhibit properties of volts per grain boundary value higher than conventional varistors for example 3.75 to 4.5 and dielectric constants lower than conventional varistors, e.g., under 1000.

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San Francisco, CA, United States of America

Gary H Wiseman