Patent ID: 8684693

Claim:
An apparatus for adjusting the pitch angle of a rotor blade ( 1 ) of a wind energy installation, having a flexible envelope drive train ( 10 ) which can be moved and stressed by a drive wheel ( 9 ) and via which the rotor blade ( 1 ) can be rotated in opposite directions about its longitudinal axis and having a tensioning roller for increasing a looping-around angle of the drive train which stresses the flexible envelope drive train, wherein the envelope drive train ( 10 ) can be moved on only a single plane, which is at right angles to the rotation axis of the drive wheel ( 9 ), and acts on a rotating bearing ring which forms an end piece of the rotor blade ( 1 ), and in that the drive wheel ( 9 ) is connected to a motor/gearbox unit ( 7 ), which is mounted on the hub ( 2 ) of the rotor blade ( 1 ), for individual adjustment of the rotor blade, wherein the envelope drive train is open and is connected at its ends to the rotating bearing ring so that the envelope drive train ( 10 ) loops around the rotating bearing ring ( 4 ) over a part ( 13 , 14 ) of its circumference in each rotation position of the rotor blade ( 1 ).