Stationary actuator device for controlling the pitch of fan blades of a turboprop

A device for controlling pitch of fan blades of a turboprop including at least one set of variable-pitch fan blades, the set being constrained to rotate with a rotary ring centered on a longitudinal axis and mechanically connected to a rotor of a turbine, each blade of the set being coupled for pitch adjustment to a synchronization ring centered on the longitudinal axis, the device comprising:

• an actuator centered on the longitudinal axis and secured to a stationary structural element of the turboprop, the actuator including a rod movable along the longitudinal axis;
• a turntable which is mounted at a center thereof on the rod of the actuator via a rotary connection such that the turntable is rotatable about the longitudinal axis while the rod of the actuator remains stationary in rotation;
• a plurality of connection arms which mechanically connect the turntable to the synchronization ring, each of the connection arms includes an axial link and a radial link, a first end of the axial link is fastened to the turntable via a first connection which pivots about a first tangential axis, a second end of the axial link is fastened to a first end of the radial link via a second connection which pivots about a second tangential axis, and a second end of the radial link is connected to the synchronization ring, the radial link is stationary in a longitudinal direction;
• means for converting the movement of the radial link of each connection arm into turning of the synchronization ring about the longitudinal axis;
• and
• a tangential link having a first end fastened to the second end of the radial link of a connection arm by a connection that pivots about a longitudinal axis, a second end of the tangential link being fastened on a blade root support that is swivel-mounted on the rotary ring and that is connected to the synchronization ring via a drive link,
• wherein longitudinal movement of the turntable under drive from the actuator causes the radial link to move in a direction that is substantially radial so as to cause the synchronization ring to turn about the longitudinal axis.