US 4,300,866 AGranted

Self-retaining spring washer

AssigneeTRW Inc.

InventorsCharles K. Fisher, Pierre E. Arias

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Abstract

A one-piece spring washer for use with threaded fasteners such as screws has a self-retention feature whereby, once positioned on the screw, it remains firmly in place. The washer comprises an annular body defining a central aperture for receiving the screw shank and a plurality of thread engaging teeth bent up from the body about the aperture for holding the washer in place. Each tooth has a helical thread confronting edge having a pitch that is steeper than, and in the opposite sense of, the pitch of the screw thread so that the teeth extend crosswise of and grip the crest of the thread. A plurality of spring elements are bent up from the washer body outboard of, but in the same direction as, the teeth. The spring elements, which flex downwardly when the screw is tightened against a workpiece, load the screw axially to resist loosening of the screw.

Claims16

Dependent claims

In combination, spring washer a and a threaded fastener of the type including a threaded shank and a head, the thread of the fastener having a crest, a groove and a predetermined sense and pitch, said washer comprising:

A. a generally flat, annular body defining a top surface, a bottom surface and a central aperture for receiving the shank of the fastener, the bottom surface of said body being adapted to bear against the head of the fastener;
B. a plurality of thread engaging teeth projecting above the top surface of said body about the central aperture for resiliently engaging the thread of the fastener and for retaining the washer on the fastener, each of said teeth including
i. a helical thread confronting edge that is oriented in a sense opposite to the sense of the fastener thread and having a pitch that is substantially steeper than the pitch of the fastener thread so as to engage and extend diagonally crosswise of the crest of the fastener thread;
and
C. a plurality of spring elements also projecting above the top surface of said body in the same general direction as said teeth, said spring elements being adapted to flex downwardly toward said body when the head of the fastener is tightened against a workpiece and to resiliently bias the fastener axially away from the workpiece thereby to prevent loosening of the fastener relative to the workpiece.

2 more elements

Dependencies are inferred from the claim text.