An electric linear actuator converts electric motor motion into linear motion using screw, wheel and axle, or cam mechanisms. Different types of electric motors can be used depending on the application needs. Construction techniques can vary, with some requiring a compact design.
A linear actuator is a device that generates linear motion from an energy source. It can push, pull or move back and forth. The actuator generally performs this task through some mechanical or hydraulic means. An electric linear actuator is a type of mechanical actuator that uses an electric motor to create motion, which is often non-linear in nature. A linear actuator converts this motion into linear motion.
An electric linear actuator makes this conversion with three basic types of mechanisms. The first is a screw actuator, the second is a wheel and axle actuator, and the third is a cam actuator. The electric motor in a screw actuator turns a nut, which causes the screw shaft to move in a straight line. The rotation of a wheel and axle actuator causes a cable, belt or rack to move in a linear fashion. The cam in a cam actuator has an eccentric shape that provides linear motion as it rotates against the base of a shaft.
Types of electric motors can include a direct current (DC) brushed motor, a brushless DC motor, an induction motor, or a stepper motor. These motors typically create rotary motion, although the specific method varies based on the application needs of the electric linear actuator. Some applications may require the motor to exert a large amount of force, while other applications may require a greater emphasis on accuracy.
An oil refinery may require an electric motor to drive a linear actuator with great force and speed. This application typically requires a high power induction motor using AC current. A linear actuator in laboratory instrumentation is more likely to need a low-power stepper motor turning a fine-pitch screw to provide linear motion accurate to a thousandth of an inch (0.254 mm).
The standard construction technique for an electric linear actuator treats the electric motor as a separate component from the actuator. The motor in this type of construction is typically within its own casing and attaches to the outside of the actuator. The drive shaft of the motor then connects to the drive screw of the actuator.
Some applications require an electric linear actuator to use a compact construction technique. This generally involves treating the motor and actuator as part of the same unit to occupy as little volume as possible. A common design approach to this problem is to hollow out the motor drive shaft so that the actuator drive screw and nut can fit inside the shaft. This design eliminates the need for a gear between the drive screw and the motor.
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