Rotational support of a wind turbine blade

1. An assembly for rotationally supporting a wind turbine blade relative to a wind turbine hub, the assembly comprising an intermediate ring having an inner annular portion and an outer annular portion provided with means for attaching the turbine blade,

whereby the intermediate ring is rotatably mounted to the hub via a first bearing arrangement, characterized in that the first bearing arrangement comprises a radial bearing and a thrust bearing,

wherein the inner annular portion is mounted to the hub via the radial bearing and the outer annular portion is mounted to the hub via the thrust bearing, and

wherein the thrust bearing comprises first and second sliding surfaces which are clamped to the hub between first and second clamping members.

2. The assembly according to claim 1 , wherein the radial bearing has a pitch diameter that is at least fives times smaller than a pitch diameter (d t ) of the thrust bearing.

3. The assembly according to claim 1 , wherein the hub comprises a hub flange extending in a radially inward direction and the intermediate ring comprises a U-shaped section, whereby a first leg of the U-shaped section forms a first clamping member and a second leg of the U-shaped section forms a second clamping member.

4. The assembly according to claim 1 , wherein the intermediate ring comprises a ring flange extending in a radially outward direction, which ring flange is clamped by the first and second clamping members.

5. The assembly according to claim 1 , wherein the thrust bearing comprises a first set of bearing segments, which have a sliding surface that forms a first sliding surface of the thrust bearing, and further comprises a second set of bearing segments which have a sliding surface that forms a second sliding surface of the thrust bearing.

6. The assembly according to claim 5 , wherein the bearing segments are made of a fibre-reinforced polymer material.

7. The assembly according to claim 6 , wherein the bearing segments are provided on a clamping surface of the first and second clamping members, whereby the clamping surface has openings through which the sliding surface of the bearings segments protrude.

8. The assembly according to claim 7 , wherein the bearing segments have a circular sliding surface.

9. The assembly according to claim 5 , wherein the bearing segments provide a continuous annular sliding surface.

10. The assembly according to claim 9 , wherein the bearing segments are formed by curved strips of sliding material, each strip having an attachment side comprising one or more shaped protrusions.

11. The assembly according to claim 10 , wherein the curved strips are provided on an axial surface of a clamping member or on an axial surface of the hub or on an axial surface of the intermediate ring, and

wherein the axial surface comprises correspondingly shaped recesses for receiving the one or more protrusions of each curved strip.

12. The assembly according to claim 10 , wherein the one or more shaped protrusions comprises a stud and/or a rib that extends over the full length of the curved strip.

13. The assembly according to claim 5 , wherein the sliding surface of each bearing segment is provided with a channel or dimples for holding a lubricant.

14. The assembly according to claim 1 , further comprising a second bearing arrangement for rotatably supporting the blade relative to the intermediate ring.

15. The assembly according to claim 14 , wherein the second bearing arrangement comprises at least three rods, whereby a first end of each rod is in connection with the intermediate ring by a first swivel joint and a second end of each rod is in connection with blade via a second swivel joint.

16. The assembly according to claim 15 , wherein the blade is supported on a shaft extension of the hub by a second radial bearing.