Blade for a wind turbine, and a servicing unit for a blade

1. A blade for a wind turbine, comprising

a substantially hollow shell which comprises an opening which extends along at least part of the length of the blade,

a servicing unit displaceable along the shell, at least partly arranged inside the shell and comprising an arm adapted to project out of the shell through the opening, and

a closing gate moving at least between a closed position in which the closing gate substantially overlaps the opening, and an open position in which the closing gate exposes the opening and allows the passage of the arm therethrough.

2. The blade of claim 1 , wherein the closing gate is pivotably attached to the shell.

3. The blade of claim 2 , wherein the closing gate is integrally formed with the shell, with a narrower section forming a hinge.

4. The blade of claim 1 , wherein the closing gate is flexible and locally deformable such that a longitudinal portion of the opening is exposed while the rest of the opening remains closed by the closing gate.

5. The blade of claim 1 , wherein the closing gate comprises several independent closing gate portions along a length of the opening, such that one closing gate portion shifts to the open position while other closing gate portions remain in the closed position.

6. The blade of claim 1 , wherein a distal edge of the closing gate comprises a projecting tab intended to overlap the shell when the closing gate is in the closed position.

7. The blade of claim 1 , wherein the servicing unit comprises a carriage which is arranged substantially inside the shell and displaceable along the blade, and to which the arm is attached.

8. The blade of claim 7 , wherein the shell is provided with an internal stiffening structure and a guide for guiding the carriage, the guide being fixed to the stiffening structure.

9. The blade of claim 7 , wherein the shell is provided with an internal longitudinal channel at least along part of the blade, the channel having a shape in cross section adapted to serve as a guide for guiding the carriage.

10. The blade of claim 1 , wherein the servicing unit is disposed to engage the closing gate as the servicing unit moves along the shell to cause shifting of at least part of the closing gate to the open position so as to expose at least part of the opening.

11. The blade of claim 10 , wherein the servicing unit pushes to the open position at least a portion of the closing gate adjacent the servicing unit.

12. The blade of claim 11 , wherein the blade comprises a parking position for the servicing unit, whereby when the servicing unit is in the parking position the servicing unit doesn't interfere with the closing gate.

13. The blade of claim 1 , wherein the arm is moveable between a deployed position in which the arm projects from the shell through the opening and a fold-away position in which the arm remains inside the shell.

14. The blade of claim 1 , wherein a blade surface servicing tool is attached at a distal end of the arm.

15. The blade of claim 1 , wherein the arm is arranged to extend in proximity to the leading edge of the blade.

16. The blade of claim 1 , wherein the opening in the shell is located on a pressure side of the blade.

17. A wind turbine comprising the blade of claim 1 .

18. A blade for a wind turbine, comprising:

a substantially hollow shell which comprises an opening which extends along at least part of the length of the blade,

a servicing unit displaceable along the shell, comprising a carriage arranged inside the shell and an arm attached to the carriage and adapted to project out of the shell through the opening, and

a closing gate moving at least between a closed position in which the closing gate substantially overlaps the opening, and an open position in which the closing gate exposes the opening and allows the passage of the arm therethrough.