Description Of Planetary Gear System - Brother FAX218 Service Manual

2.3.2

Description of planetary gear system

The planetary gear train consists of the sun gear 18/82, two planet gears 20, arm A, and arm
B, as shown below.
Planet gear 20B
If the motor rotates, the sun gear 18/82 rotates so that the rotational torque is transmitted to
the engagement between the sun gear and the planet gears 20. Since the arms and planet
gears are so designed that the moment of the arms is less than that of the planet gears, the
arms turn around the center shaft in the same direction as the sun gear 18/82.
If the planet gear(s) becomes engaged with any other gear so that the arm cannot turn any
more, the rotational torque of the sun gear 18/82 is transmitted to that planet gear. Accord-
ingly, the planet gear starts rotation in the opposite direction of the sun gear 18/82.
Motor gear
Arm B
Planetary Gear System
Stopper of arm A
Sun gear 18/82
III – 7
Planet gear 20A
Arm A