Swash-plate device for controlling the pitch of rotor blades with non-rotating plate articulated by cotters on a central ball joint

A device for controlling a pitch of a plurality of blades of an aircraft rotor on which each blade is, firstly, rotated around an axis of rotation of a shaft of the rotor by means of a hub rotating integrally with the shaft, and, secondly, rotating integrally, around a longitudinal blade pitch change axis, with at least one pitch lever controlled by a corresponding pitch rod, connected to a plate rotating with the rotor and belonging to a swash-plate assembly in which the rotating plate is rotary mounted on a non-rotating plate, restrained against any rotation around the rotor axis, the two plates being annular, surrounding the rotor axis, and being oscillating mounted by the non-rotating plate on a central ball joint, centered on the rotor axis and mounted sliding parallel to the rotor axis around a cylindrical guide coaxial to the rotor axis and non-rotating around the said rotor axis, with the result that the swash-plates can be translated parallel to the rotor axis and tilted in any direction around the rotor axis, being activated by control actuators connecting the non-rotating plate to the structure of the rotor aircraft, for the control of a collective pitch and a cyclic pitch respectively of the blades, wherein the ball joint is immobilized in rotation around the said rotor axis on said guide, and two grooves, diametrically opposite in relation to the rotor axis and each of a constant section, are arranged in a spherical external face of the ball joint, so as to extend in concentric circular arcs around a first diametrical axis of the ball joint which is perpendicular to the rotor axis, two cotters being, on the one hand, mounted pivoting on the non-rotating plate around a second diametrical axis of the ball joint, which second diametrical axis is perpendicular to said first diametrical axis, and, on the other hand, mounted sliding each in one of the grooves respectively of the ball joint.