The primary advantage of worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can be applied as swiftness reducers in low- to medium-acceleration applications. And, because their reduction ratio is based on the number of gear teeth by itself, they are smaller sized than other styles of gears. Like fine-pitch lead screws, worm gears are usually self-locking, making them suitable for hoisting and lifting applications.
Although the sliding contact decreases efficiency, it provides very quiet operation. (The utilization of dissimilar metals for the worm and gear also contributes to quiet procedure.) This makes worm gears well suited for use where sound should be minimized, such as in elevators. In addition, the use of a softer material for the gear means that it could absorb shock loads, like those knowledgeable in major equipment or crushing devices.
The meshing of the worm and the apparatus is an assortment of sliding and rolling actions, but sliding contact dominates at high reduction ratios. This sliding action causes friction and high temperature, which limits the efficiency of worm gears to 30 to 50 percent. In order to minimize friction (and for that reason, heat), the worm and gear are created from dissimilar metals – for example, the worm could be made of hardened steel and the gear manufactured from bronze or aluminum.
Such as a ball screw, the worm in a worm gear might have a single start or multiple starts – and therefore there are multiple threads, or helicies, on the worm. For a single-start worm, each full switch (360 degrees) of the worm advances the gear by one tooth. Consequently a gear with 24 teeth provides 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 number of begins on the worm. (This is different from most other types of gears, where the gear reduction is a function of the diameters of both components.)
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