Linear actuator is an actuator, which is created in linear motion, compared with conventional circular motion motor. Linear actuators are used in machine tools and industrial machinery, computer xxx equipment (such as disk drives and printers), valves and dampers, and many other places where linear motion is required. The hydraulic cylinder or pneumatic cylinder inherently produces linear motion. Many other mechanisms are used to generate linear motion from rotating electrical machines.
Types of linear actuators
Mechanical actuators usually operate by converting rotary motion into linear motion. Transformation is usually done through several simple types of mechanisms.
Screw: Screw, screw jack, ball screw and roller screw actuators all operate according to a simple mechanical principle called screw. By rotating the nut of the actuator, the screw shaft moves in a straight line.
Axle: Hoist, winch, rack and pinion, chain drive, belt drive, rigid chain and rigid belt actuator work according to axle principle. Rotating wheels move cables, racks, chains or belts to produce linear motion.
Cam: The working principle of cam actuator is similar to that of wedge, but its stroke is relatively limited. When the wheel cam rotates, its eccentric shape provides thrust at the bottom of the shaft.
Some mechanical linear actuators can only pull, such as hoists, chain drives and belt drives. Others only push (e.g. cam actuators). And pneumatic hydraulic cylinder or screw can be designed to generate force in two directions.
Mechanical actuators usually convert the rotary motion of the control knob or handle into linear displacement through screws and/or gears attached to the knob or handle. A screw jack or car jack is a familiar mechanical actuator. Another series of actuators are based on segmented spindles. The rotation of the jack handle is mechanically converted into the linear motion of the jack head. Mechanical actuators are also often used in laser and optical fields to manipulate the positions of linear platforms, rotating platforms, mirror supports and goniometers. And other positioning instruments. For accurate and repeatable positioning, index marks can be used on the control knob. Some actuators include encoders and digital position readings. These are similar to the adjustment knobs used on micrometer, but their purpose is position adjustment rather than position measurement.
A hydraulic actuator or hydraulic cylinder usually includes a hollow cylinder in which a piston is inserted. Unbalanced pressure exerted on the piston will produce a force that can move an external object. Because the liquid is almost incompressible, the hydraulic cylinder can provide controlled and accurate linear displacement of the piston. The displacement is only along the axis of the piston. A common example of a manually operated hydraulic actuator is a hydraulic jack. Generally, however, the term “hydraulic actuator” refers to a device controlled by a hydraulic pump.
Or pneumatic actuators cylinders, similar to hydraulic actuators, except that they use compressed air instead of liquid to generate force. Their working principle is similar to a piston, in which air is pumped into the chamber and pushed out from the other side of the chamber. Pneumatic actuators is not necessarily used for heavy machinery and when there is a large amount of weight. One of the reasons why pneumatic actuators are superior to other types is that the power source is only an air compressor. As air is the input source, pneumatic actuators can be used in many mechanical activity places. Disadvantages are that most air compressors are bulky, bulky and loud. Once installed, they are difficult to transport to other areas. Pneumatic actuators may leak, which makes them less efficient than mechanical linear actuators.
A micro electromechanical linear actuator, in which the lead nut is a part of the motor. The screw does not rotate, so when the motor rotates the screw, the screw extends or retracts. Pressure compensated underwater linear actuator for remote control of ROV Typical compact cylindrical linear electric actuator Typical linear or rotary+linear electric actuator Moving coil Linear, rotary and linear+rotary actuators work in various applications.
Electromechanical actuators are similar to mechanical actuators, except that control knobs or handles are replaced by motors. The rotary motion of the motor is converted into linear displacement. Electromechanical actuators can also be used to power motors that convert electrical energy into mechanical torque. Modern linear actuators have many designs, and every company that manufactures them tends to have its own proprietary methods. The following is a general description of a very simple electromechanical linear actuator.