Patent ID: 7316533

Claim:
A fastener for continually exerting a tightening torque to a fastening member fixedly screwed onto a mounting base, comprising a torsion coil spring formed in a winding shape so as to be inserted in an axial direction onto the fastening member and having a fixing end to be fixed onto the mounting base so that tightening torque can be accumulated in said torsion coil spring, and a detachable stopper configured to be fitted to said torsion coil spring, with said torsion coil spring having accumulated tightening torque, in such a manner that said detachable stopper can be removed from said torsion coil spring in order to release the accumulated tightening torque of said torsion coil spring, wherein said detachable stopper is constituted by a cylindrical member, and wherein said torsion coil spring is configured so as to be formed in a cylindrical shape to be retained without change in diameter by said stopper and so as to radially expand gradually larger in diameter toward said fixing end of said torsion coil spring into a cylindrical cone shape upon being released from said stopper.