Construction and Working of a Worm Gear Speed Reducer

Worm Gear Speed ReducerOne of the major applications of gears is in gear reduction. Gear reduction results in the decrease in speed of rotation but leads to an increase in torque. Almost all the types of gears systems viz. spur gears, bevel gears, helical gears, etc. can be used for gear reduction where the output gear has a larger diameter as compared to the input gear. But the most efficient gear reduction is achieved through the use of worm gears speed reducer systems.

Construction of a Worm Gears Speed Reducer System
The construction of a worm gear is fairly simple. It consists of a cylindrical spiral groove called the worm acting as the input and is mounted with a larger gear called the worm gear (or worm wheel) which acts as the output.

Working of a Worm Gears Speed Reducer System
The worm gear starts spinning due to the input and causes the worm gear to rotates. For each rotation of the worm, the worm gear moves by one tooth. Hence the number of rotations required by the worm for complete rotation of the worm gear is equal to the number of teeth on the worm gear. Generally the reduction ratio is given by:

R = Number of teeth on the worm gear : 1

Where R = gear reduction.

Advantages and Application
The greatest advantage of a worm gear speed reducer is the high gear reduction ratio. Another advantage is the compact size of the system as compared to other gear systems. Also the worm gears are non reversible due to high torque required for the reverse operation.

The worm gear system finds application in small-motorized instrument and toys. Most of these are battery operated and have a small motor. Though the speed produced is higher, the torque is less. The reduction in speed and increase in torque can be achieved by application of the worm gear system. They are also used in conveyor belts due to their non-reversibility. Worm gears are also used in the differential gear system called TORSEN(R). However their application in vehicles in not wide spread since their gear reduction is larger than required.