Patent ID: 7227672

Claim:
A gear changing device, comprising: a drive motor rotatable in a forward direction or a reverse direction; a sun gear that is rotated by the drive motor; a planetary gear that is constantly engaged with the sun gear; a rotating member that is concentric with the sun gear and rotates in a same direction as the sun gear when the sun gear rotates in the forward direction, so as to pivotally rotate the planetary gear around the sun gear, and that stops rotating when the sun gear rotates in the reverse direction, so as to allow the planetary gear to rotate on an axis of the planetary gear to a plurality of predetermined positions on a path of the planetary gear where the planetary gear pivotally rotates, the rotating member being provided on a circumference thereof with a plurality of recesses and projections that are one of indented and protruded in a diametrical direction of the rotating member, the rotating member alternately disposing the recesses and projections, each having a specific width; a plurality of transmission gears that are engaged with the planetary gear at the predetermined positions on the path of the planetary gear where the planetary gear pivotally rotates; and electronic sensors switch that detects the recesses and the projections at a fixed position.