Rotorcraft blade provided with a tiltable flap

1. A rotorcraft rotor blade ( 1 ) including at least one tiltable trailing-edge flap ( 5 ), said flap ( 5 ) being suitable for pivoting about a virtual hinge axis (Y′) extending substantially along the span of said blade ( 1 ) and of said flap ( 5 ), said blade ( 1 ) including at least one main ball joint ( 30 ) provided with an inner cage ( 32 ) together with a first pin ( 31 ) and an outer cage ( 33 ), the front portion ( 33 ′) of said outer cage ( 33 ) of the main ball joint ( 30 ) being connected to a linear actuator ( 10 , 10 ′) arranged in said blade ( 1 ) and serving to pivot said flap ( 5 ), said first pin ( 31 ) of the main ball joint ( 30 ) being substantially perpendicular to said virtual hinge axis (Y′) about which said flap ( 5 ) pivots.

2. A blade according to claim 1 , wherein the axis of symmetry of said main ball joint ( 30 ) is arranged substantially 25% of the way along the chord of said flap ( 5 ), starting from the leading edge of said flap ( 5 ).

3. A blade according to claim 1 , wherein said main ball joint ( 30 ) is self-lubricating.

4. A blade according to claim 1 , wherein said first pin ( 31 ) is secured to said blade ( 1 ), said outer and inner cages ( 33 , 32 ) of the main ball joint ( 30 ) being disposed between the top and bottom plates ( 15 , 16 ) of a fork arranged at the trailing edge of the blade, said first pin ( 31 ) of the main ball joint ( 30 ) passing through said top and bottom plates ( 15 , 16 ).

5. A blade according to claim 4 , wherein said actuator ( 10 ) is connected to said front portion ( 33 ′) of the outer cage ( 33 ) of said main ball joint ( 30 ) successively via a first connecting rod ( 40 ), a crank ( 41 ), an extensible flexible pivot ( 43 ), and then via a second connecting rod ( 44 ).

6. A blade according to claim 5 , wherein said first connecting rod ( 40 ) is a flexible leaf.

7. A blade according to claim 6 , wherein said flexible leaf is integrated with said crank ( 42 ).

8. A blade according to claim 5 , wherein said extensible flexible pivot ( 43 ) comprises a simple pivot ( 43 ′), a rod ( 43 ″′), and a threaded sleeve ( 43 ″), said simple pivot ( 43 ′) being connected firstly to said crank ( 42 ) and secondly to said rod ( 43 ″′), the threaded sleeve ( 43 ″) being secured to the second connecting rod ( 44 ), said rod ( 43 ″′) being engaged in said threaded sleeve ( 43 ″).

9. A blade according to claim 5 , wherein said extensible flexible pivot ( 43 ) comprises a spring ( 45 ) having turns that touch at rest, said spring ( 45 ) being secured firstly to said crank ( 42 ) and secondly to said second connecting rod ( 44 ).

10. A blade according to claim 4 , wherein the rear portion ( 33 ″) of the outer cage ( 33 ) of the main ball joint ( 30 ) is secured to the flap ( 5 ).

11. A blade according to claim 1 , wherein said blade ( 1 ) has two actuators ( 10 , 10 ′), said blade being provided with two main ball joints ( 30 , 30 ′) spaced apart by a distance (L 1 ) along the span of the flap that is equal to half said span (L) of said flap.

12. A blade according to claim 1 , wherein said blade includes at least one fastener ball joint that is not controllable by an actuator.