Insulating bushing assembly

Claim 1

An insulating bushing assembly extending through an aperture in a wall of electrical apparatus, comprising: a. An electrically insulating bushing having an enlarged portion and a reduced portion and having an annular shoulder between said portions, the reduced portion extending through the aperture and having an annular groove spaced from the shoulder; b. an elastic gasket between the shoulder and the wall; c. an annular coil spring in the groove and having a cross sectional diameter greater than the depth of the groove and substantially less than the width of the groove at the surface of the reduced portion, and d. the spring contacting a peripheral corner of the aperture on the side of the wall opposite the gasket and external of the reduced portion to enable the spring to roll on an inturned surface portion of the groove radially inwardly of the groove with the corner as the center of spring rotation into tight contact between the groove surface and the corner in response to expansion of the gasket, whereby the elastic gasket is retained in fluid-tight compression between the bushing and the wall.