Linear actuators are designed to drive parts of machines and mechanisms in a linear progressive motion. The drive converts electrical, hydraulic energy or compressed gas energy into motion or force. This article presents an analysis of hydraulic linear actuators, their advantages, and their disadvantages.
So how a linear actuator works?
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According to the principle of operation, linear actuators can be divided into:
– electric;
– pneumatic;
– hydraulic.
Electric linear actuators convert electrical energy into mechanical energy. As an engine, they use either a rotating or linear electric motor. The rotating electric motor moves the rod by means of a mechanical transducer, for example by means of a ball screw or roller screw.
Pneumatic and hydraulic actuators are actually mechanical converters and represent a kind of insert (pneumatic or hydraulic) between the engine and the actuator.
Pneumatic linear actuators have a piston inside a hollow cylinder. Pressure from an external compressor or hand pump moves the piston inside the cylinder. With increasing pressure, the piston moves along the axis, creating a linear force. The piston returns to its initial position by means of a spring or compressed gas supplied from the other side of the piston. Hydraulic linear actuators work the same way pneumatic actuators do, but practically incompressible fluid supplied by the pump moves the rod better than the compressed air.
Hydraulic Actuators
Advantages:
1. Hydraulic actuators are suitable for tasks requiring high forces. They can create a force 25 times bigger than pneumatic actuators of the same size. They operate at pressures up to 27 MPa.
2. Hydraulic motors have a high power rating per volume.
3. Hydraulic actuators can keep the force and torque constant without the pump supplying additional fluid or pressure, since the fluids, unlike gas, are practically not compressed.
4. Hydraulic actuators can be located at a considerable distance from pumps and motors with minimal loss of power.
Disadvantages:
1. Like pneumatic actuators, fluid loss in hydraulic actuators leads to less efficiency. In addition, leakage of liquid leads to contamination and potential damage to a number of located components.
2. Hydraulic actuators require many accompanying components, including a fluid reservoir, motors, pumps, bleeding valve, heat exchanger, etc. In connection with which such drives are difficult to locate.
When a particular installation, machine or part of the device performs any straight-line movements during operation, the natural choice for you will be a compact hydraulic linear actuator. This is especially true in cases where a reliable drive is required, which in mechanical or pneumatic design would be too complicated or expensive.
