A blocking device that includes a blocking pin movable on the first element between an unblocked position and a blocked position, and an actuating element secured to the second element and arranged to move the blocking pin. The blocking pin is fastened to the first element by a stressing element arranged to exert a force stressing the blocking pin toward its unblocked position between the unblocked position and an intermediate position of the blocking pin, and to exert a force stressing the blocking pin toward its blocked position between the intermediate position and the blocked position of the blocking pin.