Patent ID: 7744322

Claim:
A nut which is comprised of: a nut body which has received in it at least three nut segments and a nut segment urging spring which urges the nut segments, where the nut segments are, when rotated in the tightening direction after a bolt is inserted into the nut segments, screwed on to a threaded portion of the inserted bolt; a spring case which is attached at an upper end thereof to an outer circumferential surface of the nut body other than an upper part of the nut body so that the spring case is rotatable together with the nut body; a washer which is rotatably attached to a lower part of the spring case; a nut body urging spring which is received in the spring case with one end of the spring connected to the spring case or to the nut body and another end thereof to the washer, so that the spring constantly urges the nut body in the tightening direction when the nut body is screwed on to the bolt.