Screw locking system for electrical applications - has three successive threads deformed by flattening crests to lock in tapped hole

摘要

The locking system for a screw is partic. suitable for electrical applications where the screw carries a locking washer held against an upper surface, and where the threads lower down screw into a tapped hole in a plate. A set of e.g. three successive threads, is deformed over a limited region so that force must be used to turn the screw when these threads enter the tapped hole. These threads are located above a threaded section (A) at the bottom of the screw. This deformation consists in flattening a small part (9) of the crests of the threads over a region (B) above this bottom section (A). The depth of thread of the deformation region is about five percent of the full thread diameter. The three deformations can be equally spaced around the screw.