Planetary gearboxes function - How it works

The simple planetary gearbox comprises of the coaxial sun gear,
planet carrier and outer gear sub-assemblies, and is combined with the
planet gears rotating at constant centres about the planet carrier.
The input is from the sun gear and the drive motion to the planet carrier is via the planet gears.
The rolling contact of the planet gears with the outer gear provides the appropriate ratio.

 

1 = Sun gear (input shaft)
2 = Planet gear
3 = Outer gear
4 = Planet carrier (output shaft) Multi-stage gearboxes are available by connecting the individual stages in sequence.
Within the gear unit combination the individual stages are sized to their torque requirement.