Patent ID: 8061262

Claim:
A stepper motor comprising: a cylindrical central gear having two ends with a centerline extending between said ends, and an external surface with circumferentially distributed and radially directed teeth, a means for mounting said central gear such that said central gear is constrained to move in pure rotational motion about the centerline of said central gear, a cylindrical hoop gear having a centerline and a bore with a circular internal surface having circumferentially distributed and radially directed teeth, three equal-lever arm cranks mechanisms, each of said mechanisms having a centerline, and each of said crank mechanisms being connected at a point to said hoop gear such that said connection points are equally spaced from said hoop gear centerline and equally spaced around the perimeter of a circle about said hoop gear centerline, and each of said crank mechanisms being adapted for mounting said hoop gear such that said hoop gear is constrained to move in translational-circular, and singularity-free motion about the centerline of said central gear, wherein said central gear is configured to fit within the bore of said hoop gear in such a manner that a plurality of said central gear teeth and said hoop gear teeth directly intermesh at a contact point between said gears whose location travels around the entire circumference of said central gear when said hoop gear makes a full translational-circular revolution about said central gear centerline, and three fluid-pressure-driven drive members chosen from the group consisting of piston or diaphragm mechanisms, each of said members having a centerline and a direct contact point with said hoop gear and configured such that said drive member-hoop gear connection points are equally spaced from said central gear centerline and equally spaced around the perimeter of a circle centered on said central gear centerline and equally spaced and interspersed between the locations of said crank mechanisms centerlines and further configured so that each said drive member applies a radially directed force to said hoop gear so as to cause said translational-circular and singularity-free motion of said hoop gear.