Variable pitch mechanism for fan blades

摘要

In a variable pitch fan assembly having a plurality of fan blades mounted in a rotor for rotation about their longitudinal axes and a drive shaft for rotatively driving the rotor, the pitch varying mechanism has a planetary gear train connected to each fan blade to rotate the latter to change the pitch or angle of attack of the blades, actuator means for effecting bi-directional rotation of the planetary gear train and a no-back, bi-directional brake interposed between the actuator means and the planetary gear train to transmit pitch-changing rotation from the actuator means to the planetary gear train and lock the planetary gear train to the rotor and prevent transmission of blade torque loads to the actuator means during steady state operation when no blade pitch-change is being effected.