Patent ID: 7591754

Claim:
A planetary gear train driven by a shaft, the planetary gear train comprising: a sun gear with an integral coupling; a ring gear; and a plurality of planet gears rotatably mounted in a planet carrier and meshing with the sun gear and the ring gear; wherein the with the integral coupling connects the sun gear to the shaft, with the integral coupling having at least one undulant flexible section joined to a spindle for accommodating misalignment between the sun gear and the shaft, wherein the undulant flexible section contains two parallel interior walls which are generally perpendicular to a central axis of the shaft and which are joined by an outer ring member; and wherein the at least one undulant flexible section further comprises an outer radius Ra with a corresponding outer radius thickness Ta, an inner radius Rb with a corresponding inner radius thickness Tb, an outer ring radius Ro, an inner ring radius Ri, and a shaft fillet radius Rs, and wherein the at least one undulant flexible section has the following design criteria: Rb/Ra< 0.6 2< Tb/Ta< 3.5 Ri> 2* Ta Ro> 2 *Ri Rs> 2 *Tb.