Drive unit for robotic manipulators

An internally balanced involute-type speed reducer;

• the reducer comprising a stator stage, an input stage, an output stage, and a plurality of gear sets in mesh, the reducer further comprising:
• a stator ring gear including a row of many gear teeth fixedly connected to a stator core by a direct coupling, and
• a rotor providing input torque rotatably connected to the stator core about a central axis and inclusive of an offset crank with offset axis parallel to the central axis and offset by a distance of the crank offset, and
• an offset crank fixedly connected to the rotor, the crank rotatably connected to a compound pinion;
• the crank offset sized to position the compound pinion teeth in mesh on one side with the ring gears;
• the rotor rotating with gears in mesh between the stator ring gear and pinion teeth;
• whereby the compound pinion precesses round the stator ring gear;
• a counterweight fixedly connected to the rotor and located in a void between an external gears and the ring gears and 180 degrees out of phase with the offset crank of the rotor, and
• the compound pinion including two rows of many gear teeth laid out in rows that mesh with ring gear and output gear where their pitch circles intersect at only one point per mesh;
• the compound pinion being rotatably connected to the rotor about the offset) crank axis, and
• an output ring gear coaxial to the stator and comprising:
• a plurality of gear teeth distributed evenly about the central axis and in constant mesh with the gears of the compound pinion;
• whereby precession of the compound pinion around the stator ring gear induces rotation of the output ring gear about the central axis;
• the reducer gear ratio set by difference between the reduction ratio of the compound pinion and stator ring gear and the reduction ratio of the pinion gears and output ring gear;
• the output rotation direction set depending on whether the ratio of stator ring gear teeth to pinion teeth is greater or less than that between the output ring gear teeth and the compound pinion teeth,
• wherein an actuator assembly further includes a hollow center extending through the stator core from end to end;
• and
• wherein the two rows of gear teeth of the compound pinion are merged into a single set of many gear teeth laid out in a single row, with teeth extending radially outwards and evenly distributed around the peripheral circumference of the compound pinion and in mesh with both the stator ring gear and the output ring gear.