Windmill rotor

In a windmill rotor for obtaining energy from wind, having a plurality of at least three plate-like main blades connected symmetrically around a shaft, each main blade bowing outwardly so that said main blades collectively define a generally sphere-like chamber, and each main blade having a plate-like secondary blade mounted on its inner surface defining a gap between the main and secondary blades and having a gap entrance and a gap exit, each said secondary blade being movable relative to the main blade under centrifugal force between a first position occupied at rest or at low rotational speeds and having a wide gap entrance and a narrow gap exit and a second position occupied at high rotational speeds and having a narrow or substantially closed gap entrance;

• the improvement which comprises a plate-like auxiliary blade mounted on the inner surface of each main blade adjacent to and ahead of said secondary blade in the direction of rotation, said auxiliary blade defining with said main blade a scoop for receiving said wind and deriving thrust therefrom, said scoop having an entrance at the trailing edge of the auxiliary blade and an exit at the leading edge of the auxiliary blade, said scoop entrance being wider than said scoop exit and being substantially no wider than said gap exit when said secondary blade is in its second position.