Abstract: This mechanism (3) for linking an opening handle (4) to a lock pin (2) comprises a calliper (6) interacting with the handle (4), a rod (11) engaged so as to slide in only one direction in a sleeve (13) at the lower end of which the pin (2) is inserted; the sleeve (13) is equipped with a ring (19) which is slidably fitted around the sleeve and can be moved during set-up from a first position at the base of the flexible arms (14) to a second position situated at the ends of the arms nearest the calliper (6), in which position the ring (19) clamps the arms (14) around the rack (12) and is held in place by suitable means (23, 24). The ring (19) prevents the arms (14) and their inner teeth from coming away at all from the rack (12), thereby guaranteeing the total irreversibility of the mechanism in both directions of the link.