An actuator is any device that creates motion in a system. A gear actuator is a specific type of actuator that typically creates motion using a basic worm gear. This style of gear consists of a threaded screw and a common toothed gear. As the screw turns, it makes the gear turn. 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 traveling backwards through the actuator.
A good example of a gear actuator in action is a basic car jack.
The basis of almost 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, rotates against a toothed gear. As the screw pushes against the gear teeth, it moves in the direction of the screw threads. The screw does not move, as one thread moves away from the gear teeth, another takes its place. This rotation allows the screw to remain stationary but creates movement in the gear.
This rotation can power almost any device with the right setup, from turning a wheel to powering a radio. In its simplest form, the gear actuator is connected directly to a rotating shaft as part of a larger machine. This turning motion is often directly transformed into usable force through the movement of a machine or the effect of an object.
A good example of a gear actuator in action is a basic car jack. As a person pumps the lever into the jack, it causes a threaded rod to rotate. The rotating rod moves a gear, usually around a second threaded rod. The rotating gear pushes the rod up, which will lift a heavy object. This also shows the two common reasons to use a gear actuator: manual and non-reverse feed.
Screws have the ability to increase power by creating a large moving surface in relation to the size of the screw. As a result, these systems are good for amplifying human power to a much greater force. This allows an unassisted person to do things they wouldn’t normally do, like lift a car to change a tire.
Along with the power amplification, the movement in a worm gear is one-sided. The screw can turn the gear, but the gear cannot 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 cannot make the jack throw the person backwards.