Worm Gear Mechanism
Worm Gears Are Found In Industrial Applications, Heavy Equipment, And Even Consumer Applications. Although Their Efficiency Is Relatively Low, They Can Provide Very High Reduction Ratios And, In Many Cases, Are Self-Locking.
Worm gears are constructed of a worm and a gear (sometimes referred to as a worm wheel), with non-parallel, non-intersecting shafts oriented 90 degrees to each other. The worm is analogous to a screw with a V-type thread, and the gear is analogous to a spur gear. The worm is typically the driving component, with the worm’s thread advancing the teeth of the gear.
Like a ball screw, the worm in a worm gear may have a single start or multiple starts – meaning that there are multiple threads, or helicies, on the worm. For a single-start worm, each full turn (360 degrees) of the worm advances the gear by one tooth. So a gear with 24 teeth will provide a gear reduction of 24:1. For a multi-start worm, the gear reduction equals the number of teeth on the gear, divided by the number of starts on the worm. (This is different from most other types of gears, where the gear reduction is a function of the diameters of the two components.)
A worm gear is a spiral thread simial to a thread on a bolt. The worm gear engages a bevel gear, as the worm gear turns its threads push the teeth of the bevel gear cauing the bevel gear to rotate.
The thread angle is such that only the worm gear may be truned to drive th larger gear. If the larger gear is attempted to be turned the teeth of teh bevel gear just jame against the worm gear keeping the larger gear locked in position.
This means that a worm gear only lets power flow in one direction from the worm to the gear but not the other way around.