Programmable power transmission mechanism with a small-size servomotor for cooperating with a power source to rotate a rotating shaft in two directions

A programmable power transmission mechanism comprising:

• a torque input unit including a servomotor, at least two stationary support shafts, and a rotating shaft that is parallel to and that is rotatable relative to said support shafts, said servomotor being provided with a motor shaft, which is rotatable in opposite first and second directions;
• a torque transmission unit including
• an input gear sleeved rotatably on said rotating shaft and adapted to be driven by a power source to rotate in one of said first and second directions,
• a pair of first and second gears sleeved rotatably on said rotating shaft and rotatable by said servomotor in said first and second directions, respectively, in such a manner that only one of said first and second gears can rotate at a time, and
• an output gear sleeved fixedly on said rotating shaft;
• and
• an output device including at least one first torque output unit and at least one second torque output unit, each of said first and second torque output units including
• a primary driving gear sleeved rotatably on a respective one of said support shafts, said primary driving gears of said first and second torque output units being connected to said input gear in two different manners so as to rotate in two opposite directions when said input gear rotates,
• a secondary driving gear sleeved rotatably on the respective one of said support shafts and meshing with a respective one of said first and second gears, only one of said secondary driving gears of said first and second torque output units being rotatable at a time,
• a sleeve assembly sleeved rotatably on the respective one of said support shafts and connected fixedly to said primary driving gear;
• a driven gear sleeved rotatably on the respective one of said support shafts and meshing with said output gear so as to transfer rotation between said driven gear and said output gear such that said driven gear and said output gear rotate in two opposite directions, and
• a coiled torsion spring having two ends that are fastened respectively to said secondary driving gear and said driven gear and being movable between a wound position, where said spring is wound on said sleeve assembly so as to permit power transmission from said primary driving gear to said driven gear when said primary driving gear rotates, and an unwound position, where said spring is unwound from said sleeve assembly so as to interrupt the power transmission from said primary driving gear to said driven gear when said primary driving gear rotates.