Screw-fixing device, with locking in the screwed state

A threaded fastening device, with locking in a screwed state, comprising:

• a body having a threaded cylindrical surface configured to threadingly engage a complementary thread;
• at least one jaw connected at least indirectly to the body and having a locking surface on a side facing the complementary thread in use;
• the at least one jaw configured and positioned to come into locking abutment against the complementary thread;
• the at least one jaw extending in a direction that is substantially circumferential with respect to an axially extending cylinder axis of the cylindrical surface, between an attachment end connected to the body, and an end which is floating in a substantially radial direction;
• and
• an actuation element moveable between a locking position and a release position, to selectively place the jaw in a locking state in which the locking surface exerts a locking pressure on the complementary thread, and respectively in a release state wherein pressure of the locking surface on the complementary thread is substantially withdrawn;
• wherein the actuation element comprises an actuation ring mounted in rotation with respect to the body about the axis of the threaded cylindrical surface.