Worm gears transfer power through 90 degrees, often with a change in torque and a reduction in size. They work in one direction and are typically found in elevators, escalators, and industrial machinery. They consist of two shafts and two gears and are unidirectional, making them ideal for places where power does not need to be transferred backwards.
Worm gears are a type of gear system. The object of a worm gear is to transfer power through 90 degrees, often with a change in torque and a reduction in size. Because the entire assembly can exist in a single plane, they operate in locations where the gear system needs to be very small or low profile. Unlike many gear systems, worm gears usually work in only one direction; the shafts turn and the gears turn in one direction. These gears are typically found in elevator and escalator motors, as well as small electric motors and large industrial machinery.
The term worm gear can be confusing. It is used to describe the whole group or one of the gears. Depending on where a person lives, the term worm or worm wheel drive may be much more common.
Regardless of what the parts are called, a typical worm gear consists of two shafts and two gears. A tree feeds a screw, usually called a worm. This screw is connected to a standard spur gear. When used in this configuration, the spur gear’s name is technically the worm gear, but that’s only when the whole assembly isn’t called by that name. The spur gear is connected to a shaft that runs at a 90 degree angle.
This group, with the exception of the shaft connected to the gear wheel, works within a single plane; this means it is flat. This allows power to enter the system in one direction and leave it in a 90 degree turn. The shaft connected to the spur gear is often connected directly to the motion system, allowing the worm gears to sit flush with the object it is working with. This small profile allows it to work inside walls, next to frame pieces, or inside an engine without making a big impact on the size of the item.
Since the spur gear can be any size relative to the screw, it is possible to change the torque of the gear using this system. As a result, worm gears are often used as a reduction system. They reduce the size of the assembly while putting out as much or more force than was put into them.
Worm gears are unidirectional. The screw can easily rotate a spur gear, but it is nearly impossible for the gear to move the screw. Consequently, these gears are used in places where power does not need to be transferred backwards through the system. This is common in industrial engines, where an unexpected backflow of power could result in loss of life.
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