Patent ID: 8016532

Claim:
An anti-loose lock nut which prevents a screw coupling between a bolt and a nut by a coil spring which is mounted in the inner circumferential surface of the nut from loosening, the anti-loose lock nut characterized in that: an extended diameter portion whose inner diameter is wider than the thread of the nut and in the inside of which a spiral groove is not formed, is formed in the inner circumferential surface of the nut; an insertion groove into which a bent end portion is fit-coupled is formed in the end of the extended diameter portion, in which the end of the coil spring is outwardly bent to form the bent end portion; a semicircular curved portion is protrudingly formed in the inner surface of the coil spring, and the outer surface of the coil spring is formed of a flat cross-sectional plane; clearance spaces are formed in the lengthy width of the extended diameter portion and the insertion groove, respectively; and the coil spring is obtained by winding an elastic wire in a spiral direction, in which according to the cross-sectional shape, the lengthy direction width of the coil spring is narrower than the thread pitch of the bolt and the central direction width of the coil spring is wider than the thread pitch of the bolt.