Patent ID: 7677154

Claim:
An electrohydraulic control unit for rotor blade adjustment of a wind farm, comprising: a hydraulic cylinder having a piston chamber and a piston rod chamber; an inflow-side valve assembly for establishing a pressure fluid connection between a pump and said piston chamber; an outflow-side valve assembly for establishing a pressure fluid connection between said piston chamber and a tank, said inflow valve assembly having at least two parallel-connected switch valves, and said outflow valve assembly having at least two parallel-connected switch valves, and said at least four switch valves being triggerable in different combinations for establishing a desired position of said hydraulic cylinder, wherein said piston rod chamber is in permanent pressure fluid connection with the pump or a pressure fluid reservoir upstream of said inflow valve assembly, wherein said switch valves of said inflow valve assembly are prestressed by respective first springs to an open switching position, and wherein said switch valves of said outflow valve assembly are prestressed by respective second springs to a closed switching position.