Blade gripping device

1. A blade gripping device for gripping a rotor blade of a wind turbine, said rotor blade having multiple pitch angles along its axis, said blade gripping device comprising:

a blade gripping assembly with at least one frame and a number of blade gripping tools, including a movable seat which has a portion which conforms to a rotor blade, a sensor arrangement realized to sense a specific feature of the blade, and a position computation unit to compute a pitch angle of the rotor blade, whereby the position computation unit is configured to orientate the seat relative to the frame in a blade gripping manoeuvre to orient the seat to the computed pitch angle of the rotor blade along the horizontal axis.

2. The device according to claim 1 , whereby the sensor arrangement comprises at least one sensor realized to detect a specific shape of the rotor blade.

3. The device according to claim 1 , whereby the sensor arrangement comprises at least one sensor realized to detect a specific position of the rotor blade relative to the device.

4. The device according to claim 3 , whereby the sensor is realized to detect a marker of the rotor blade.

5. The device according to claim 4 , whereby the marker comprises a magnetic marker.

6. The device according to claim 1 , whereby the sensor arrangement comprises at least one optical sensor.

7. The device according to claim 6 , whereby the at least one optical sensor comprises a camera, which operates in an optical wavelength perceptible to the human eye.

8. The device according to claim 6 , whereby the at least one optical sensor comprises a laser sensor.

9. The device according to claim 1 , whereby the sensor arrangement comprises at least one sensor realized to sense a magnetic field.

10. The device according to claim 1 , whereby the sensor arrangement the position computation unit is realized to compute a specific position and an orientation of the rotor blade from sensor data provided by a number of sensors of the sensor arrangement.

11. The device according to claim 1 , further comprising a number of position adjustment assistance means realized to assist a movement of the device relative to the rotor blade.

12. The device according to claim 11 , whereby the position adjustment assistance means comprise at least one of:

a display for an operator,

a sound and/or light signal generating unit realized to output sound and/or light signals representing a position of the device relative to the rotor blade,

an automatic movement mechanism realized to automatically move the blade gripping tools of the device into a predefined gripping position with respect to the rotor blade.

13. The device according to claim 1 , comprising

a first frame which is essentially horizontally aligned in a designated operating position and

a second frame which is essentially horizontally aligned in the designated operating position and

the blade gripping assembly,

whereby the first frame and the second frame are connected to each other via a swivel connection, the swivel connection realized to permit a yawing movement of the second frame relative to the first frame.

14. The device according to claim 1 , wherein at least one blade gripping tool comprises

a sling and

an automatic sling handover mechanism comprising a sling-conveying element and a sling-receiving element, whereby the sling-conveying element is realized to convey a connection means of the sling along a two-dimensional predefined path of travel around a part of the rotor blade towards the sling-receiving element to connect to a receptor of the sling-receiving element.

15. A method of moving a blade gripping device with at least one frame for gripping a rotor blade of a wind turbine, relative to the rotor blade, whereby the device comprises a blade gripping assembly with a number of blade gripping tools including a seat which has a portion which conforms to a rotor blade, said seat being on one side and a sling on the other side for encircling opposite sides of the rotor blade, and a sensor arrangement and whereby the sensor arrangement senses a specific feature of the rotor blade in order to support a movement of the device, whereby the specific feature is such that it is used to tilt the seat and the sling about a horizontal axis relative to the frame and the rotor blade in a blade gripping manoeuvre.

16. The method of claim 15 , further comprising the step of computing a specific position of the rotor blade with a position computation unit.