Rotor coupling

1. A rotor coupling for an air displacement rotor, said coupling including:

a first member rotatable about a first axis of rotation;

a second member substantially disposed within a hub of said air displacement rotor, said second member being in angularly variable engagement with said first member for allowing said second member and said hub to rotate about a second axis of rotation;

one side of said air displacment rotor having an input aperture for receiving said first member, whereby said input aperture is angularly movable with respect to said first member;

at least one torque pin for transmitting torque between said first and second members, wherein angular variation between said first and second axes of rotation is delimited by the width of said input aperture and wherein said first and second axes of rotation are freely angularly variable with respect to each other upon rotation of said air displacement rotor such that said rotation is substantially self-balancing during air displacement.

2. A rotor coupling according to claim 1 , wherein said at least one torque pin protrudes from the surface of said first member.

3. A rotor coupling according to claim 1 including at least one elongate recess for engagement with said at least one torque pin.

4. A rotor coupling according to claim 1 including a bearing surface for supporting bearing contact with said first member.

5. A rotor coupling according to claim 4 , wherein said bearing surface is in sliding support engagement with said part spherical portion of said first member.

6. A rotor coupling according to claim 5 , wherein said bearing surface is adapted for complementary engagement with said part spherical portion of said first member.

7. A rotor coupling according to claim 5 , wherein said second member includes said bearing surface.

8. A rotor coupling according to claim 6 including a bearing ring, said bearing ring including said bearing surface.

9. A rotor coupling according to claim 1 , wherein said first member includes a part spherical portion.

10. A rotor coupling according to claim 9 , wherein said at least one torque pin radially protrudes from the surface of said part spherical portion.

11. A rotor coupling according to claim 1 including two torque pins.

12. A rotor coupling according to claim 11 including two corresponding elongate recesses.

13. A rotor coupling according claim 12 , wherein said rotor is in said form of a fan having said hub and a plurality of radially extending fan blades.

14. A rotor coupling according to claim 1 , wherein said first member is adapted for coupling with a prime mover.

15. A rotor coupling according to claim 14 , wherein said prime mover is an electric motor.