Abstract: A pivot mechanism comprising first and second frames linked so as to pivot, in which locking members may co-operate with teeth on one of the frames in order to lock the mechanism, and at least one stop member which is joined to the second frame and which is arranged so that the locking member abuts at an angle against said stop member if the pivot mechanism is subjected to a pivot torque in a first direction of rotation whilst the locking member is in its locked position: if this torque exceeds a threshold value, the stop member is displaced towards the over-locking member and pushes it against the teeth of the frame in order to lock it.