A gear rate reducer is a representative exemplory case of swiftness changers, and presently used models could be categorized by the kind of gears, shaft positions and set up of gears into (1) equipment reducer with parallel axes, (2) gear reducer with orthogonal axes, (3) equipment reducer with planetary gearbox perpendicular non-intersecting axes, and (4) equipment reducer with coaxial axes.

Types and mechanisms of gear reducers with parallel axes
The gear 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 a lot 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 equipment reducer)
When properly lubricated, it can be used for a long time.
Could be produced relatively cheaply because standardized gears are used.
Gear reducers with spur gears are used for increasing quickness.
The sizes of gear reducers with spur gears are is generally large. In comparison to worm gear reducers with the same swiftness ratio, their outer forms are huge, and the number of parts increases resulting in constructional disadvantages. Consequently, it is used for machines with high rotation on the load side, or which need higher output rotation than the primary movers (for increasing speed). The gear types are shown in Table 2.1.

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