Mechanisms – Worm Drive Mechanism

For this assignment we looked at mechanisms that allowed for rotational movement to be translated into vertical or horizontal movement. I thought the worm and gear mechanism was really interesting.

This mechanism has been around for many centuries. The earliest records of the use of the worm drive date back to Pappus of Alexandria, a Greek mathematician, in the 3rd century AD. The name of the mechanism comes from the fact that it utilizes a gear and a worm screw.

This mechanism is also known as an endless screw because there is no end to the number of 360 degree rotations it can make. As the worm drive spins perpendicularly to the gear, its tread lines up with the teeth of the gear and cause the gear to rotate.

The worm screw spins at a faster rate than the gear does, which allows the gear to create more power. This happens because speed is inversely proportional to power. It is also important to note that rotating the gear does not cause the worm screw to spin, so in order for this mechanism to work, the worm screw must initiate the movement.

The worm drive is most commonly used in elevators because, as I mentioned above, the gear cannot turn on the worm, so when used in elevators this mechanism doubles as breaks – preventing free fall from occurring. Worm drives can also be found in automobiles, conveyor belts, and various other pieces of machinery.

I thought this mechanism was really interesting because even though it has a relatively unimpressive appearance, it has some pretty useful features. In addition to its locking/breaking abilities, of which no other arrangement of gears can claim, the worm gear can also be used for gear reductions, the reduction of revolutions per minute.

Gear reductions allow for machinery to be much more manageable. However, gear reduction can be achieved with various other methods of organizing gears and is therefore not unique to worm drives. In addition to the above, I thought it was very interesting have this mechanism functioned on the basis that the gear and the screw were perpendicular – not something I really imagine when I think of gears.

         


http://kmoddl.library.cornell.edu/model.php?m=16
http://kmoddl.library.cornell.edu/model.php?m=492
http://kmoddl.library.cornell.edu/model.php?m=572
http://www.electrolift.com/the-worm-gear-advantage.php
http://mechteacher.com/worm-gear/