Patent ID: 7284939

Claim:
A fastener comprising a bolt having a head and a threaded shank, a nut, having a threaded hole, threaded onto the threaded shank of the bolt, and a washer disposed on said threaded shank between the head of the bolt and the nut, wherein: the threaded shank of the bolt and the threaded hole of the nut are substantially symmetrical about a common central axis extending lengthwise of the shank of the bolt, and the threads of the nut and shank have the same pitch; said nut has a tapered recess facing said head of the bolt, the recess having a first end, and a second end farther than said first end from the head of the bolt, and a wall extending from said first end to said second end, said wall being tapered and symmetrical with respect to said common central axis, the taper of said wall being such that said first end of the recess is larger than said second end; said washer comprises a sheet of material having a thickness smaller than the pitch of said threads, said washer having an object-engaging part in engagement with a face of an object surrounding the shank of the bolt, said object being prevented by the bolt head from disengagement from the bolt, and said sheet being formed with a tapered projection, said tapered projection extending into said tapered recess of the nut, and having a lower part and a tapered part, said tapered part having an external surface symmetrical about said central axis and said tapered part being in engagement with said tapered wall of the recess, and a passage in the washer through which the shank of the bolt extends, said passage including a hole formed in said projection at a location remote from said object-engaging part, said hole having an edge and being sufficiently eccentric with respect to a said external surface of the tapered part that rotation of the nut on said bolt in a direction to tighten the fastener on said object causes the wall of the recess in said nut to exert a lateral force on said washer, pressing said edge of the hole in the washer against the threads of the shank of the bolt, thereby exerting a locking action resisting loosening of the fastener.