A gear swiftness planetary gearbox reducer is a representative exemplory case of acceleration changers, and presently used units can be categorized by the type of gears, shaft positions and set up of gears into (1) equipment reducer with parallel axes, (2) equipment reducer with orthogonal axes, (3) gear reducer with perpendicular nonintersecting axes, and (4) equipment reducer with coaxial axes.

Types and mechanisms of equipment reducers with parallel axes
The apparatus reducers with parallel axes use spur gears, helical gears, or herringbone gears. Their input and result shafts are parallel. For reduction ratios, 1/1 – 1/7 for one-stage shafts, 1/10 – 1/30 for two-stage shafts, and 1/5 – 1/200 for more than three-stage shafts are commercially offered. The general characteristics of gear reducers with parallel axes are the following :

For high precision gears, the transmission efficiency is quite high. (98 to 95% for one-stage gear reducer)
When correctly lubricated, it can be used for a long period.
Could be produced relatively cheaply since standardized gears are used.
Gear reducers with spur gears are used for increasing speed.
The sizes of gear reducers with spur gears are is normally large. Compared to worm equipment reducers with the same speed ratio, their outer shapes are large, and the number of parts increases resulting in constructional disadvantages. For that reason, it is used for machines with high rotation on the load side, or which require higher output rotation compared to the prime movers (for increasing velocity). The apparatus types are proven in Table 2.1.

The gear reducers with parallel axes usually use helical gears. They are found in steel facilities, ships, cranes, elevators, and conveyors. For automation machines, these equipment reducers are also known for geared motors which are equipment reducers with directly linked motors.