1. Open gear:
The gear is totally exposed to the outside; there is no casing or dust cover; the working conditions are rather poor; the external debris is easy to access; and lubrication and maintenance are more frequent; it is typically used in low-speed transmission such as construction machinery, agricultural equipment and advised mechanical equipment.
2. Closed gear:
Mostly employed in significant events, closed gear consists of carefully machined, securely closed box (casing), which provides the optimum conditions for lubrication and protection; the gears are not exposed to the outside. Typical in cars include engine gears, transmission gears, and so forth.
3. Semi-open gear:
Sometimes the huge gear is partly submerged in the oil pool when the gearing has a basic protective cover. The working circumstances have been better than those of the open type, but they still cannot be rigorously avoided from the infiltration of external trash.
