Self-propelled trolley

1. A self-propelled trolley for handling a wind-turbine blade of a wind-turbine, the trolley comprises:

a driving device for propelling the trolley between locations;

a lifting device, the lifting device configured to raise and lower the wind-turbine blade, wherein a maximum height of the trolley is less than or equal to the height of a wheel of the trolley when the lifting device is in a non-lifted position; and

a holding device, wherein the holding device is arranged for holding the wind-turbine blade at a point along its length, wherein the holding device and lifting device are connected by a universal joint to allow the blade free movement, between the lifting device and the holding device, during transport of the wind-turbine blade.

2. The self-propelled trolley according to claim 1 , comprising a remote control interface, the remote-control interface configured to control the driving device.

3. The self-propelled trolley according to claim 1 , wherein the driving device comprises a motor and a drive train for transferring power to two or more wheels of the trolley.

4. The self-propelled trolley according to claim 1 , wherein the lifting device is configured to support a load, such that a point at which the load is supported by the lifting device is arranged over the trolley for any position of the lifting device.

5. The self-propelled trolley according to claim 1 , wherein the lifting device comprises a hydraulic lifting arrangement.

6. The self-propelled trolley according to claim 1 , wherein the lifting device is rotatable relative to the driving device.

7. The self-propelled trolley according to claim 1 , wherein the holding device comprises a cradle the cradle being shaped to accommodate a curved surface of the wind-turbine blade.

8. The self-propelled trolley according to claim 1 , wherein the holding device is configured to accommodate a securing element for securing the wind-turbine blade to the holding device.

9. The self-propelled trolley according to claim 1 , wherein a maximum height (H max ) of the trolley comprises at most 1.5 m when the lifting device is in a non-extended position.

10. The self-propelled trolley according to claim 1 , comprising a communications interface for communicating with a communications interface of a further transport device.

11. The self-propelled trolley according to claim 1 , comprising at least one sensor for sensing a relative position of the trolley.

12. The self-propelled trolley according to claim 1 , wherein a maximum height (H max ) of the trolley comprises at most 1.25 m when the lifting device is in a non-extended position.

13. A method of handling a wind-turbine blade, the method comprises the steps of:

positioning a self-propelled trolley at a point underneath the wind-turbine blade;

providing a holding device for the wind-turbine blade;

actuating a lifting device of the self-propelled trolley to raise or lower the wind-turbine blade on the holding device;

providing a universal joint between the lifting device and the holding device;

transporting the wind-turbine blade while allowing the holding device to freely rotate with respect to the lifting device; and

controlling a driving device of the self-propelled trolley to propel the trolley between locations.

14. The method according to claim 13 , comprising the steps of

deploying a self-propelled trolley to transfer a tip end of the wind-turbine blade to a target destination; and

deploying a self-propelled trolley to move a root end of the wind-turbine blade to a corresponding target destination.

15. A self-propelled trolley for handling a wind-turbine blade, the trolley comprises:

a driving device for propelling the trolley between locations;

a holding device configured for holding the wind-turbine blade; and

a lifting device, connected to the holding device by a universal joint, the lifting device configured to raise and lower the wind-turbine blade, wherein the holding device is connected to the lifting device with the universal joint such that the holding device may freely rotate with respect to the lifting device during transport of the wind-turbine blade.