Ball coupled compound traction drive

Traction drive apparatus having a variable turns ratio comprising

• a rotatable input member disposed for rotation about an input axis,
• a plurality of drive balls disposed for rotation within said input member, each said drive ball having a center and rotating about a drive ball rotational axis through said center,
• each said drive ball rotational axis being fixed with respect to each said drive ball, respectively, and disposed at a ball skew angle .theta. with respect to said input axis,
• said ball skew angle .theta. between said drive ball rotational axes and said input axis controlling said variable turns ratio,
• a first outer race ring fixedly attached to a housing and a second outer race ring forming a rotatable output member,
• said drive balls being captured between said first and said second outer race rings such that torque is transmitted from said input member to said output member,
• each said drive ball having a point of contact with said first outer race ring on a line through said center which forms a preselected angle with said input axis and said ball skew angle .theta. affecting said variable turns ratio (TR) in accordance with ##EQU4## means for preloading said first and second outer race rings to control torque limits of said torque transmitted from said input member to said output member;
• and
• means for varying said ball skew angle .theta. between said drive ball rotational axes with respect to said input axis to vary said variable turns ratio between said rotatable input member and said rotatable output member.