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

1. A device for controlling pitch of fan blades of a turboprop including at least one set of adjustable-pitch fan blades, the set being secured to rotate with a rotary ring centered on a longitudinal axis and mechanically connected to a turbine rotor, 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, secured to rotate with the turbine rotor and mechanically connected to the synchronization ring by a plurality of connection arms,

wherein each connection arm comprises

an axial link connected to an actuator rod,

a radial link connected to the synchronization ring,

a first bellcrank connecting the axial link to the radial link such that actuating the actuator causes the synchronization ring to move in turning about the longitudinal axis, and

a second bellcrank secured to the rotary ring and connected firstly to the radial link and secondly to a tangential link fastened to the synchronization ring such that movement of the radial link in a direction that is substantially radial causes the synchronization ring to move in turning about the longitudinal axis.

2. A device according to claim 1 , wherein one end of the axial link of each connection arm is connected to an outer cage of a rolling bearing having its inner cage connected to the rod of the actuator and configured to slide longitudinally on a shaft of the turbine rotor via fluting.

3. A device according to claim 1 , wherein the radial link of each connection arm is guided radially by leaktight bearings.

4. A device according to claim 1 , wherein one end of the axial link of each connection arm is connected to the actuator rod.

5. A device according to claim 1 , further comprising means for imparting a predetermined pitch to the fan blades in an event of the actuator failing.

6. A device according to claim 1 , wherein each connection arm passes radially through a casing arm of the turboprop.

7. A device according to claim 1 , wherein the connection arms are regularly distributed about the longitudinal axis.

8. A device according to claim 1 , wherein the set includes ten fan blades and the actuator is mechanically connected to the synchronization ring by five connection arms.

9. A two-propeller turboprop comprising:

a turbine including two contrarotating rotors and two sets of adjustable-pitch fan blades constrained to rotate with two rotary rings connected to respective ones of the rotors, the pitch of the fan blades of at least one of the sets being controlled by a device according to claim 1 .