Power transmission apparatus with a coiled torsional spring capable of being wound around rollers on a sleeve assembly for transmitting a torque

A power transmission apparatus comprising:

• a stationary support shaft having a front portion and a rear portion;
• a sleeve assembly disposed rotatably around said support shaft and having an annular surface unit, which is formed with a plurality of axially extending slots therethrough;
• a primary driving gear sleeved fixedly on said sleeve assembly and rotatable in a predetermined direction;
• a plurality of rollers confined respectively and rollably within said slots in said sleeve assembly, each of said rollers having two opposite side portions that project respectively and outwardly from two opposite sides of a respective one of said slots in said sleeve assembly;
• a secondary driving gear sleeved rotatably on said sleeve assembly and rotatable in the predetermined direction;
• a driven gear sleeved rotatably on said support shaft;
• and
• a coiled torsional spring disposed around said sleeve assembly and having a front end that is fastened to said secondary driving gear, and a rear end that is fastened to said driven gear, said spring being spaced apart from said rollers, said spring being wound around said rollers when said secondary driving gear rotates so that said rollers are clamped and locked between said spring and said sleeve assembly, thereby permitting synchronous rotation of said primary driving gear, said spring, and said driven gear.