A locking fastener assembly comprising a fastener having a shaft (12) and a head (14 or 114) and first threads (16) for placing the shaft (12) in tension to clamp a part (18). A threaded washer (20) has second threads (22) for disposition between the head (14 or 114) and the part (18). A torsion spring (24) reacts between the head (14 or 114) and the washer (20) for urging the head (14 or 114) and the washer (20) to rotate in opposite directions. The assembly is characterized by the first and second threads (22) being of different pitches and in the same helical direction whereby the torsion spring (24) continually rotates the washer (20) to maintain a pre-load on the shaft (12). To assemble the components, the hex head (14 or 114) is first torsionally loaded against the washer (20) utilizing the torsional spring (24) such that the components would rotate apart if the pre-load was removed. The hex head (14 or 114) and washer (20) are of the same polygonal (hexagonal) shape and are rotated together with a conventional socket type wrench disposed over both at the same time. The locking fastener assembly is then tightened as the head (14 or 114) and washer (20) are rotated together or in unison to the desired torque.
Hess, Daniel P., "Locking fastener assembly" (2000). USF Patents. 813.
University of South Florida