Reduction gears are mechanisms that lower the speed or torque of a rotating input shaft through use of gears with varying circumferences. Speed reducers such as gear boxes rely on reduction gears to perform their function of decreasing the number of rotations per minute.
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Reduction gears are made of strong, durable metal like steel and are available in a wide range of sizes and reduction ratios, which are the ratios of the input speed to the output speed. When several reduction gears are used in succession, the multistage speed reducer is able to achieve ratios of up to 1,000:1. Average ratios are measured in integers such as 5:1 or 250:1. Reduction gears are the central component in gear boxes, gearheads, gear drives and other speed reducers; these devices would not function without them. There are other devices that slow the speed of an input shaft using different techniques such as cyclo reducers and planetary gearboxes. Reduction gears find wide usage in industrial and manufacturing processes and are utilized in conveyor belts, robotic assemblies, material handling, packaging applications and more. Perhaps the most well-known example is the transmission found in motor vehicles. Because the engine runs at high speeds, reduction gears are necessary to slow the RPM down to a level that the wheels can handle.
Reduction gears use at least two gears of differing sizes that work together to slow the input speed. In single stage reductions, there are two gears, one with a circumference larger than the other. Because the large gear requires a longer distance to turn to complete one full rotation, the small gear will turn at least twice as the large gear turns. This is the basic principle behind reduction gears. The number of rotations required for the input gear to equal the output gear provides the reduction ratio, which allows the operator to calculate the best gearbox for the job. Multistage reductions use many gears that work in the same way. The output can be calculated by multiplying the reduction of the first set with the reduction of the second with the reduction of the third and so on. Another way to identify reduction gears is by counting the teeth on both the input and output gear and arranging it into a ratio. Speed reducers use a variety of input and output configurations to attach the shaft to the mechanism such as inline, right angle or parallel offset. Both vertical and horizontal orientations are possible. The main types of gearing arrangements for reduction gears are spur, helical, planetary, harmonic, worm, bevel and cycloidal.
