Methods of making high voltage resistant members

In a method of making a high voltage resistant integrated member in the form of an insulated oil-less bushing characterized by:

• forming a core of a conductive rod with paper windings thereabout, said forming including the steps of interposing metal foil within the paper windings and impregnating the windings with a hardenable epoxy resin, and curing said resin at a predetermined temperature;
• extruding a sheath of essentially unvulcanized elastomer on said core, said extrusion being performed at a temperature below the vulcanizing temperature of the elastomer, the elastomer being selected from the group consisting of ethylene-propylene-diene copolymers, ethylene-propylene copolymers and butyl rubber;
• mounting at least one fully vulcanized elastomeric shed on the sheath, the shed being fabricated from a material of the same or similar elastomer formulation as used for the sheath to provide a core-shed-sheath asemblage, and
• then heating the core-shed-sheath assemblage to vulcanize the sheath and bond same to the core and to the shed;
• wherein an improvement in the step of mounting before the step of heating to vulcanize comprises:
• expanding the sheds at room temperature to allow fitting them onto the sheath;
• cooling the sheds while maintaining them expanded;
• placing the cooled expanded sheds on the sheath covered core;
• and
• then allowing the sheds to shrink tightly onto the sheath by warming them to room temperature.