Power transmission apparatus using planetary gear having a plurality of gear trains and methods of use thereof

摘要

Provided is a power transmission apparatus using a planetary gear having a plurality of gear trains. The apparatus includes: a housing including a cover which is open or closed, and a speed change locking unit which locks and releases selectively one of ring gears; a carrier installed inside the housing; a planet gear set including three or more different sized planet gears; a ring gear set including ring gears; a sun gear set including sun gears meshed with external teeth of the planet gears and having an output shaft which outputs power to an outside of the housing; and an input shaft which is aligned coaxially to the output shaft and rotates the carrier by external force transmitted from the outside of the housing. The input shaft extends out of the housing by passing through the shaft extension.