Speed differential planetary gear train

Claim 1

A speed differential planetary gear train comprising, a first rotatable shaft connected to an eccentric for rotation therewith, the eccentric rotating about the axis of the first shaft. a two gear cluster comprising a first external gear and a second external gear, said cluster being journaled on said eccentric for rotation about the axis of the eccentric, said first external gear meshing and rotating within a first internal gear disposed around it, thereby forming a first gear system, said second external gear meshing and rotating within a second internal gear disposed around it, thereby forming a second gear system, means preventing rotation of one of said internal gears, and means connecting the other of said internal gears to a second shaft for rotation therewith, said second shaft having an axis of rotation which is colinear with the axis of rotation of the first shaft, the two said systems both being standard involute systems with N = PD for each gear, said external gears having different numbers of teeth, the gears of the said train being further related substantially in accordance with the following equations: 1) E = (D.sub.int - D.sub.ext) /2 2) F.sub.F,A = E.sub.B,C 3) 0.84 d.sub.int ≦ D.sub.ext ##EQU3## wherein N is an integer equal to the number of teeth on the respective gear; P is the diametral pitch of the respective gear; D is the gear diameter; E is the offset between the center of the eccentric and the axis about which the eccentric rotates; the non-rotating internal gear is designated as F; the external gear which meshes with the non-rotating internal gear is designated as A; the other external gear is designated as B; and the other internal gear is designated as C.