Double-acting actuator and single-acting actuator: principles of work, differences, application fields. Spring return actuator as a kind of single-acting actuator.
Single Acting vs. Double Acting Actuators: Working Principles, Differences, and Application Fields
What Is Pneumatics and How does It Work
In pneumatic systems, the air is used to produce linear movement. For example, if we take a pneumatic actuator, the compressed air is used to move the piston inside of the cylinder. A single-acting pneumatic actuator operates from compressed air which moves the piston in a single direction only. A different force will be required for retracting. When compressed air is applied to move the piston in both directions, it is known as a double-acting actuator.
Even though the difference between double and single action doesn’t seem to be huge, however, the operating principles differ. Hence, the single/double action actuators have their advantages and disadvantages. Hence, they might be applied in different fields.
Double Action vs. Single Action
So, what is the difference between single action and double action? Based on what has been mentioned, we can define double-action vs. single action as follows:
- Single action: when a pneumatic means is applied to move the piston in a single direction.
- Double action: when a pneumatic means is applied to move the piston in both directions: forward and backward.
Hence, a single-acting pneumatic cylinder differs from a double-acting pneumatic cylinder in its operating principle. Hence, there will be differences in application fields, as well.
Single vs. Double Action: Difference
It looks like the main difference between single and double action is in the way the pneumatic force is applied and whether another mechanical force is needed to retract the piston. However, if we check the application fields of both types of actuators: single action versus double action ones, we will see that they are quite different.
Single Acting Cylinder vs. Double Acting Cylinder
These are basically two different kinds of cylinders used for linear actuators.
In the case with a single-acting cylinder, the compressed air or gas is used to move the piston from one side but not in a reverse direction. A different source of mechanical force is used to retract the piston.
In the case with a double-acting cylinder, the air is used to move the piston in both directions. No external mechanical force is used.
Double Acting Cylinder
So, how can we define a double-acting cylinder and what is its operation principle? How does a double-acting cylinder work?
In a double-acting cylinder, the force that delivers linear motion works in both directions. Each end of the double-acting cylinder is equipped with a port. The air enters through the port. So, the piston moves forward and backward by the force of compressed air.
Single Acting Cylinder
In the single-acting cylinder, the force that delivers linear motion works in a single direction. A single-acting pneumatic cylinder is equipped with a single port where the compressed air enters. This air is used to relocate the actuator piston to the needed position.
An external mechanical force (a spring, gravity, mechanical movement) is used to retract the piston.
A single-acting pneumatic cylinder is usually compact and the air consumption is lower than in a double-acting cylinder.
Spring return actuator
A spring return actuator is a single-acting pneumatic actuator where the force of a spring is used to retract the piston. Due to its simplistic design and affordable pricing, the spring return.
This is one of the most widely used actuators due to its simplicity and relatively cheap cost.
Double Acting Actuator
If you check a double-acting pneumatic actuator, you will see that only one force moves the piston: the force of compressed air or gas. First, the pressurized air is fed to one side of the piston. This force moves the piston to the needed position. When the piston gets to the setup position, the pressurized air is fed to another side of the piston. The piston moves in a reverse direction until it achieves the setup position.