Damage resistant plastic expansion nut and screw therefor

Abstract

A molded plastic one-piece hollow expansion nut comprises an outwardly expandable shank which is insertable through a panel hole and a head at one end of the shank for engaging the panel surface. A screw-receiving bore extends axially through the nut and receives the threaded shank of a screw whose screw head bears against the nut head. The portion of the bore along which shank wall expansion occurs is cylindrical and of slightly larger diameter than the screw thread. The inmost end of the bore is of oblong cross-section and its minor axis is shorter than the diameter of the screw thread. A single screw-engaging thread in the cylindrical bore initially holds and guides the screw. The shank walls opposite the ends of the minor axis have oblique screw-thread receiving slots therethrough which define very sturdy damage resistant nut threads which engage the screw thread. Rotational insertion of the screw draws the insertion end of the nut shank toward the nut head and effects shank expansion to thereby secure the nut in the panel hole. In some embodiments, interengageable components on the nut and on the screw interengage to prevent further screw rotation after the nut reaches fully expanded condition. In some embodiments, ratchet teeth on the screw thread and nut slots engage to prevent screw removal.