Epicyclic gear train integral sun gear coupling design

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.