US Patent 7255537 Wind turbine gear unit with integrated rotor bearing

In a gear unit for use in wind turbines and of the kind with a planetary gear stage, and an integrated main rotor bearing that is adapted to provide location for the rotor hub relative to the wind turbine nacelle and to locate the planet carrier relative to a low speed ring gear, the forces due to bending moments acting between the rotor hub and nacelle are transmitted substantially directly from the rotor hub to the nacelle via the main bearing and substantially none of the bending moments are transmitted to the nacelle via the ring gear of the planetary gear stage.