All About Worm Gears, Combo Gears and Combination Tigears
When large amounts of speed reduction are needed, the worm gear is usually the speed reducer of choice. It’s commonly used in conveyor systems, especially as a braking feature for the conveyor when the motor is not running. Worm gears can shift speeds quickly from 20:1, and even 300:1, making them a useful tool in unpredictable environments.
What sets the worm gear apart from other speed reducers is the fact that while the gear cannot turn the worm, the worm easily turns the gear. The shallow angle on the worm creates friction and holds the worm in place.
A worm gear is usually made up of a brass wheel and steel worm. It looks like a screw flush against a spur with moderately angled teeth.
The ability of the worm gear to turn on a dime is not the only reason it has become one of the most popular speed reducers on the market today. Modifications in the design and manufacturing of this device have enabled the worm gear to become more compact and more efficient. A worm gear’s size is determined by the center distance” of the reducer and these well-known industry standards are typically used by manufacturers as a catalog numbering system for purchasers.
Aside from the above mentioned high reduction ratio, there is another reason worm gears are so popular. On a standard gear, if enough force is applied to the gear, it can change directions rather easily. This can be disastrous in the right setting, so worm gears are used. The friction generated between the worm and the wheel prevents any reverse direction power, regardless of the force applied to the gear.
The only downside to using worm gears in your conveyor systems is lubrication. The structure and design of the gear makes it hard to lubricate and because of the friction generated it requires a hard-to-filter lubricant – ISO 320 and greater.
You can make a worm gear more effective my employing a technique known as twofold enveloping. The single enveloping worm gear is a cylindrical component with same diameter around the outside as the length of the threaded section. The gear’s teeth only partially envelop the worm thread. However, with twofold enveloping, the gear teeth envelop a larger portion and this results in better precision and twisting. This unique design strategy enables better oiling of the gear, as well, because there is plenty of space between each of the worm gear’s teeth.
The worm gear, while a favored commodity especially in conveyor systems, is not a perfect tool for every application. Just as it has huge benefits for a variety of environments, it also has shortcomings that may prevent the average user from purchasing it and instead looking at a different type if speed reducer. The common consensus though is that the benefits outweigh the downfalls, and that is why the worm gear has become such a commonplace speed reducer in a variety of setting, especially in the conveyor systems of the food processing industry.
