Blade pitch change mechanism

摘要

A pitch change mechanism for a plurality of fan blades (12) comprises adjustment device (60) to rotate the blades (12) about their longitudinal axes. A gear box (34) provides rotary power to drive the adjustment device (60) in response to a control signal. The gear box (34) is mounted in the fan shaft (30) and rotates therewith. An input shaft (33) to the gear box (34) is mechanically connected to a turbine shaft (32) so that the input shaft (33) rotates with the turbine shaft (32). The difference between the speeds of the fan shaft (30) and the turbine shaft (32) is used to drive an output shaft (39) of the gear box (34). The rotary power of the output shaft (34) drives the pitch adjustment device (60) via a plurality of gears (50).