The primary benefit of worm gears is their capability to provide high reduction ratios and correspondingly high torque multiplication. They can be utilized as rate reducers in low- to medium-acceleration applications. And, because their decrease ratio is founded on the number of gear teeth alone, they are more compact than other styles of gears. Like fine-pitch lead screws, worm gears are typically self-locking, which makes them perfect for hoisting and lifting applications.
Although the sliding contact reduces efficiency, it provides incredibly quiet operation. (The use of dissimilar metals for the worm and gear also contributes to quiet operation.) This makes worm gears suited to use where noises should be minimized, such as in elevators. In addition, the use of a softer materials for the apparatus means that it can absorb shock loads, like those experienced in major equipment or crushing machines.
The meshing of the worm and the gear is an assortment of sliding and rolling actions, but sliding contact dominates at high reduction ratios. This sliding actions causes friction and heat, which limits the proficiency of worm gears to 30 to 50 percent. In order to minimize friction (and for that reason, heating), the worm and gear are made from dissimilar metals – for example, the worm may be made of hardened steel and the gear made of bronze or aluminum.
Like a ball screw, the worm in a worm gear may possibly have a single start or multiple starts – and therefore there are multiple threads, or helicies, on the worm. For a single-start worm, each total transform (360 degrees) of the worm increases the gear by one tooth. Thus a gear with 24 teeth will provide a gear reduction of 24:1. For a multi-begin worm, the apparatus reduction equals the number of teeth on the apparatus, divided by the amount of starts on the worm. (That is different from almost every other types of gears, where in fact the gear reduction is definitely a function of the diameters of the two components.)
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