WORM GEAR:
A worm gear is used for transmitting power between two non-parallel and non-intersecting shafts. It is useful when a large speed reduction ration is required between crossed axis shafts. A worm is similar to a screw and a worm gear is similar to a nut. Therefore, if the worm is rotated, the worm gear can be caused to rotate due to the screw like action of the worm.
Worm & worm gear are composed of a single body. Gear geometries are created from the parameters of ISO standards. The tooth profile is represented by multiple arcs. The sprocket tooth geometry data is:
•Created from a predefined data file
•Edited from a predefined data file
•Exported from a predefined data file
•Imported from a predefined data file
TYPES OF GEARS:
There are three different types of gears that can be used in a worm drive.
The first are non-throated worm gears. These don't have a throat, or groove, machined around the circumference of either the worm or worm wheel. The second are single-throated worm gears, in which the worm wheel is throated. The final type are double-throated worm gears, which have both gears throated. This type of gearing can support the highest loading.
An enveloping (hourglass) worm has one or more teeth and increases in diameter from its middle portion toward both ends.
Double-enveloping worm gearing comprises enveloping worms mated with fully enveloping worm gears. It is also known as globoidal wormgearing.
Uses:- The primary benefit of worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can also be used as speed reducers in low- to medium-speed applications.
Application:-
Tuning Instruments – most guitars, basses, banjos and other stringed instruments use a worm gear for the tuning mechanism to work. The gear’s force reduction is the main reason for this, coupled with the locking capability that keeps the desired string tightness in place. This type of worm gear is different to most as you can tune both up and down; whereas most worm gears can only be turned in one direction.
Elevators/Lifts – worm gears can often be found in the machinery of common elevators/lifts because of their compact size and non-reversible properties. As the gear/load cannot transmit motion back through the worm/hoist, using this type of gear can act as a secondary braking system. This means the load cannot free fall and load speed is easily regulated.
Torsen Differentials – Large trucks or off-road vehicles, such as the Hummer, often need to deliver different amounts of torque to the each wheel, depending on what action the vehicle is performing. For example, wheels need to spin at different speeds whilst turning a corner as the inside wheels travel a shorter distance. A vehicle’s Torsen differential will handle this movement via a combination of worms and worm gears that separate each individual wheel’s performance.
Gates and Conveyor Belts – Typical worm drives can only be turned in one direction, which means that conveyor belts and security gates lock-up when not being used and will not run backwards. Automatic security gates will often adopt two worm drives, one to open and another to close. This means the gate can be locked in each direction and cannot be breached or forced.