Plastic screw grommet

Claim 1

A one-piece plastic screw grommet for use in mounting a screw relative to a blind bore of a predetermined diameter located in a fibrous material panel, said grommet including a head and a shank having a common bore passing through said head into said shank, said shank having an upper first portion with an external dimension adjacent said head substantially equal to said predetermined bore diameter and said shank carrying axially disposed rotation prevention means thereon, circumferentially disposed shoulder means intermediate the extremities of said shank and projecting radially beyond said predetermined dimension, an intermediate tapered portion connecting said predetermined dimensioned upper portion and a lesser dimension lower portion extending to the free end of said shank opposite said head, said shoulder means being at least two in number and disposed on said upper portion with said tapered intermediate portion blending into the lowest axially located shoulder means, said shank further including at least two axially extending slots which communicate between the common bore and the external surface of said shank, a shouldered arm positioned in each of said slots and connected at one extremity adjacent the said lesser dimension lower portion and extending toward said head, each said shouldered arm on its radially outer surface being tapered outwardly to an intermediate point and thence inwardly to form shoulder means, the inner surface of said arms adjacent their point of connection to said shank lower portion initially having substantially parallel opposed surfaces extending axially to an intermediate point and then diverging outwardly away from one another to form a throat, adapted to lead in a screw, said intermediate point on the inner surface of said arms lying in a plane transverse to the axis and adjacent to or on a plane passing through the shoulder means carried by said arms, and axially extending flange means integral with and extending from the double tapered free ends of said arms, said common bore is non-circular through said head and a substantial portion of said shank and thence blending into a cylindrical bore in said lower portion said non-circular bore being generally in cross section an elongated shape with the major sides diverging linearly from their connection to substantially flat ends toward their midpoints which fall on a plane lying in the axis of the fastener to form a generally six-sided figure, each third side being substantially parallel and with at least two pairs of said parallel sides being spaced a distance substantially equal to the pitch diameter of a screw to be used therewith whereby said screw will be guided into axial alignment with said cylindrical bore in said lower portion thereby substantially preventing canted introduction of said screw.