Pancake planetary drive

An improved two stage planetary differential drive comprising:

• A. a housing,
• B. an inner nonorbiting member in the housing,
• C. an outer nonorbiting member in the housing, one of said nonorbiting members being rotatively fixed to the housing, the other nonorbiting member being rotatively movable in the housing,
• D. a shaft connected to the other nonorbiting member and projecting from said housing,
• E. an annular orbiting member positioned in the housing radially between the inner and outer nonorbiting members, said orbiting member having an inner wall and an outer wall surrounding the inner wall, said inner nonorbiting member and the inner wall of said orbiting member being formed with opposing surfaces constituting teeth in meshing engagement with one another, there being at least one less tooth in the inner nonorbiting member than in the orbiting member inner wall, said outer nonorbiting member and the outer wall of said annular orbiting member being formed with opposing surfaces constituting teeth in meshing engagement with one another, there being at least one more tooth in the outer nonorbiting member than in the orbiting member outer wall, and
• F. means for orbiting the orbiting member about said shaft axis, all of said orbiting and nonorbiting member teeth being disposed radially outward from and in the same transverse section of the drive as said orbiting means so that when said orbiting member is orbited, the forces exerted on said orbiting means are all in said section.