On the role of springs in single-acting pneumatic actuators

The working principle of single-acting pneumatic actuator

When compressed air enters the middle cavity of the cylinder piston from air port 2, the two pistons move toward both ends of the cylinder, forcing the springs at both ends to compress. The air in the cavities at both ends is discharged through air port 4. At the same time, the two pistons synchronously drive the gear shaft to rotate counterclockwise. . After the compressed air is switched by the solenoid valve, the two pistons in the cylinder move toward the middle under the elastic force of the spring itself. The air in the middle cavity is discharged from the air port 2. At the same time, the two pistons synchronously drive the gear shaft to rotate clockwise. By rotating clockwise and counterclockwise, the purpose of opening and closing the valve is achieved.

Double-acting pneumatic actuators require the thrust of compressed air to open and close. In other words, this pneumatic actuator will remain fixed in a certain position when it loses air.

The single-acting pneumatic actuator is an automatic reset type. After the air source pressure is lost, the actuator will drive the valve to return to the initial setting position under the action of the elastic force of the spring. Relatively speaking, it is safer and more reliable.

How to ensure that the spring is foolproof at critical moments?

1.The material of the spring is very critical. The spring is rolled from spring steel wire. The performance and strength of various brands of spring steel are different, and the price is also very different. There is a huge difference between imported wire rods and domestic wire rods. Correspondingly, the fatigue life and strength of springs also vary greatly. The finely crafted spring can easily exceed 1 million times during the entire service cycle, and the attenuation of the force value is only 10%-12% (compared with the original force value before fatigue testing).

2.The single-acting pneumatic actuator spring is composed of a spring seat and a copper tube connection. The quality of the connection directly affects the quality of the actuator. Whether the spring will bend sideways, whether the spring will make abnormal noise during operation, whether the spring has 5° adjustment margin, and a series of other issues.

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