An actuator is any device that creates movement in a system. A gear actuator is a specific type of actuator that typically creates movement using a basic worm gear. This style of gear consists of a threaded screw and common toothed gear. As the screw turns, it makes the gear rotate. This style of actuator is preferred in two circumstances: when manual power is used to operate the device or when the system cannot have power travel backward through the actuator.
The basis of nearly every gear actuator is a worm gear. These devices are extremely simple, being a combination of two of the first simple human machines. A threaded bar, the screw, turns against a toothed gear. As the screw pushes against the gear’s teeth, it moves in the direction of the screw’s threads. The screw doesn’t move, as one thread moves away from the gear’s teeth another takes its place. This rotation allows the screw to remain stationary but it creates motion in the gear.
This rotation can power nearly any device given the right setup, everything from turning a wheel to powering a radio. At its most simple, the gear actuator is connected directly to an axle that turns as part of a larger machine. This turning motion is often turned directly into usable force through either moving a machine or affecting an object.
A good example of a gear actuator in action is a basic car-jack. As a person pumps the handle on the jack, it causes a threaded rod to turn. The turning rod moves a gear, which is usually around a second threaded rod. The turning gear pushes the rod upwards, which will lift a heavy object. This also shows the two common reasons to use a gear actuator: manual and non-reversed power.
Screws have the ability to magnify power by creating a large moving surface relative to the size of the screw. As a result, these systems are good for magnifying human power into a much greater force. This allows an unassisted person to do things he couldn’t ordinarily do, such as lift a car in order to change a tire.
Along with power magnification, the movement in a worm gear is one way. The screw can turn the gear, but the gear can’t move the screw. This restriction prevents energy from traveling in both directions through the gear actuator. In the example above, the person can lift the car but the car couldn’t cause the jack to fling the person back.