Sealed expansion anchor

Claim 1

A one-piece plastic anchor member for insertion into an apertured workpiece and adapted to accept the shank of a screw, said anchor including a head having an aperture therein and a surface for clampingly engaging one side of a workpiece, a shank flexibly attached to and extending from said head, said shank having a pair of legs spaced laterally from one another throughout their length, a hollow flexible tubular member extending from said head between and laterally spaced from said legs, said tubular member including an endless sidewall of substantially unform thickness and being generally oval with a pair of opposed flat sidewalls, respectively generally paralleling the medial surface of said legs and a pair of curved end walls connecting said sidewalls at opposite ends thereof, said tubular member defining a generally axially extending bore communicating with said head aperture, the inner surface of said tubular member forming said oval bore having a circumferential extent substantially equal to the pitch diameter of said screw whereby said flexible tubular element is transformed from an oval to a substantially cylindrical configuration with its incidental lateral expansion outwardly into engagement with and urges said legs against the surfaces forming the aperture in said workpiece upon insertion of said screw into said bore, said cooperation between the circumferential extent of the Bore and the pitch diameter of the screw insuring substantial thread engagement through a substantial circumferential portion of said tubular member whereby said screw is securely retained against inadvertent axial withdrawal.