PURPOSE: To enable transmission of an output during reversing, by a method wherein a solar gear with a one-way clutch and an integral rotary arm are mounted on an input shaft, an arm with a one-way clutch and a transmission gear are mounted on the support shaft of a planetary gear and the support shaft of an arm with a one-way clutch, and a driven gear geared with the transmission gear is mounted on an input shaft.

CONSTITUTION: When a motor 1 reversed, an arm 10 is also integrally rotated along with rotation in a direction B of an input shaft 2. Since a solar gear 6 is not rotated by means of a clutch 9, a support shaft 12 and a transmission gear 16 are revolved along with revolution in a direction B of an arm 10. Since the support shaft 12 is rotated in reverse direction to a direction C based on the arm 10 but the solar gear 6 is not rotated, the planetary gear 14 is rotated in a direction D as it is revolved in a direction B. The transmission gear 16 is rotated as it is revolved, and a driven gear 17 geared with the gear 16 is rotated in a direction B. since the diameter of the transmission gear 16 is differed from that of the planetary gear 14, the gear 16 moves the gear 17 to a point (d). Since a rotation speed ratio of an input shaft to an output shaft is set to 1/10, the speed of the output shaft is reduced to 1/10 of that of the input shaft.