Planetary gear box with two double eccentrics

In a planetary gear box with two double eccentrics which comprises an input shaft, a first outer gear secured to said input shaft, a plurality of second outer gears meshing with the first outer gear, a plurality of crankpins which are connected to the second outer gears so that a rotary movement of the second outer gears is transduced into an orbital movement of the crankpins, two gear-wheel planets which have a plurality of pin holes formed therein circumferentially spaced from each other, said planets having outer gear teeth formed at the periphery of each planet, the crankpins being inserted into the pin holes so that eccentric revolutional movements of the planets, which are angularly spaced 180.degree., are generated by means of the orbital movement of the crankpins, an outer gear ring surrounding the outer gear teeth of the planets and having inner teeth which mesh with the planets, this gear ring being formed on an outer part of a housing of the gear box and constituting one member, the crankpins being journaled in a planet carrier forming another member, one of said members being a low speed rotating element and the other member being a stationary element of said planetary gear box, the improvement wherein:

• said gear box has only two of said crankpins diametrically opposite one another, each crankpin having a double eccentric, each double eccentric having a bearing with an internal radial clearance on one eccentric less than a normal radial clearance and a bearing with said normal radial clearance on the other eccentric, each planet having two pin holes equipped one with a bearing of an internal radial clearance less than a normal radial clearance and the other with a bearing with said normal radial internal clearance.