A linear actuator is an actuator that creates motion in a straight line, in contrast to the circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in many other places where linear motion is required. Hydraulic or pneumatic cylinders inherently produce linear motion. Many other mechanisms are used to generate linear motion from a rotating motor.
Principles
In the majority of linear actuator designs, the basic principle of operation is that of an inclined plane. The threads of a lead screw act as a continuous ramp that allows a small rotational force to be used over a long distance to accomplish movement of a large load over a short distance.
Variations
Many variations on the basic design have been created. Most focus on providing general improvements such as higher mechanical efficiency, speed, or load capacity. There is also a large engineering movement towards actuator miniaturization.
Most electro-mechanical designs incorporate a lead screw and lead nut. Some use a ball screw and ball nut. In either case, the screw may be connected to a motor or manual control knob either directly or through a series of gears. Gears are typically used to allow a smaller (and weaker) motor spinning at a higher rpm to be geared down to provide the torque necessary to spin the screw under a heavier load than the motor would otherwise be capable of driving directions. Effectively this sacrifices actuator speed in favor of increased actuator thrust. In some applications, the use of worm gear is common as this allows a smaller built-in dimension still allowing great travel length.
Advantages
1. Cheap. Repeatable. No power source required. Self-contained. Identical behavior extending or retracting.
2. Cheap. Repeatable. An operation can be automated. Self-contained. Identical behavior extending or retracting. DC or stepping motors. Position feedback possible.
3. Simple design. Minimum of moving parts. High speeds possible. Self-contained. Identical behavior extending or retracting.
4. Very small motions possible.
5. Very high forces possible
6. Strong, light, simple, fast.
7. Very compact. The range of motion greater than the length of the actuator.
Disadvantages
1. Manual operation only. No automation.
2. Many moving parts prone to wear.
3. Low to medium force.
4. Consumes barely any power. Short travel unless amplified mechanically. High speeds speed. High voltages required, typically 24V or more. Expensive, and fragile. Good in compression only, not in tension. Typically used for Fuel Injectors
Principles
In the majority of linear actuator designs, the basic principle of operation is that of an inclined plane. The threads of a lead screw act as a continuous ramp that allows a small rotational force to be used over a long distance to accomplish movement of a large load over a short distance.
Variations
Many variations on the basic design have been created. Most focus on providing general improvements such as higher mechanical efficiency, speed, or load capacity. There is also a large engineering movement towards actuator miniaturization.
Most electro-mechanical designs incorporate a lead screw and lead nut. Some use a ball screw and ball nut. In either case, the screw may be connected to a motor or manual control knob either directly or through a series of gears. Gears are typically used to allow a smaller (and weaker) motor spinning at a higher rpm to be geared down to provide the torque necessary to spin the screw under a heavier load than the motor would otherwise be capable of driving directions. Effectively this sacrifices actuator speed in favor of increased actuator thrust. In some applications, the use of worm gear is common as this allows a smaller built-in dimension still allowing great travel length.
Advantages
1. Cheap. Repeatable. No power source required. Self-contained. Identical behavior extending or retracting.
2. Cheap. Repeatable. An operation can be automated. Self-contained. Identical behavior extending or retracting. DC or stepping motors. Position feedback possible.
3. Simple design. Minimum of moving parts. High speeds possible. Self-contained. Identical behavior extending or retracting.
4. Very small motions possible.
5. Very high forces possible
6. Strong, light, simple, fast.
7. Very compact. The range of motion greater than the length of the actuator.
Disadvantages
1. Manual operation only. No automation.
2. Many moving parts prone to wear.
3. Low to medium force.
4. Consumes barely any power. Short travel unless amplified mechanically. High speeds speed. High voltages required, typically 24V or more. Expensive, and fragile. Good in compression only, not in tension. Typically used for Fuel Injectors
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