Plastic fastener

Claim 1

A plastic fastener having a head and an integral bifurcated shank forming at least two shank portions, an axial bore traversing said head and extending throughout said shank, said bore being substantially cylindrical adjacent said head and adapted to accept a complimentary axially moveable drive pin having a predetermined diameter, said bore being tapered and defined within said shank by tapered facing surfaces on said shank portions and said tapered bore having its major diameter terminating at said cylindrical bore adjacent said head, said tapered bore having a substantially uniform radius of curvature of varying depth relative to the axis of said fastener with said radius of curvature being substantially complementary to said pin, each shank portion including an axially disposed radial relief means that extends throughout substantially all of the axial extent of each of said shank portions, said relief means on each shank portion including an axially disposed slot means which is substantially perpendicular to and opens into said bifurcation while extending radially outwardly from said bifurcation at tapering depths for a substantial portion of the axial extent of each shank portion and a second slot means extending radially inwardly from the circumferential outer surface of each shank portion to form between the two tapered slots a thin walled buckle section joining two substantially equal sections of each shank portion, said drive pin which includes at least one laterally extending lug projecting downwardly therefrom and acceptable from axial movement within one of said shank portion slots communicating with said bore, recess means communicating with said one slot adjacent to but spaced from the free end of said shank, said recess means adapted to accept said at least one lug in positive locking relationship when said pin is driven axially in said bore to expand said shank portions.