What is the working principle and selection of pneumatic valves?

Pneumatic valve is an execution unit in a fluid control system in the field of industrial automation. It is actuated by pneumatic It is composed of an actuator and a valve, and then drives the actuator through the air source pressure to control the operation of the valve. This chapter mainly describes the commonly used quarter-turn switch pneumatic valve.



The composition of pneumatic valve

It is mainly composed of two main parts: pneumatic actuator and valve. Of course, according to different working conditions and user needs, different accessories can also be equipped to achieve different functions, such as solenoid valves, air source triple parts, and feedback devices. , electrical positioner, etc.



Pneumatic actuator classification

From the mode of rotation, it is divided into two types: linear stroke and angular stroke;from the structure, it is divided into: piston type, diaphragm type, plunger type, vane type, etc.;from the function, it is divided into: single-acting, double-acting, three-position type wait.



Double-acting working principle (JLATD)

When the air source pressure enters the middle cavity between the two pistons of the cylinder from the air port (2), the two pistons are separated and moved toward the two ends of the cylinder. The air in the air chambers at both ends is discharged through the air port (4), and at the same time, the two piston racks are synchronized. Drive the output shaft (gear) to rotate counterclockwise. On the contrary, when the air source pressure enters the air chambers at both ends of the cylinder from the air port (4), the two pistons move toward the middle of the cylinder, and the air in the middle air chamber is discharged through the air port (2). At the same time, the two piston racks drive the output shaft (gear) synchronously. ) rotate clockwise. (If the piston is installed in the opposite direction, the output shaft will rotate in the opposite direction, which is the double-acting reverse type.)


Single-acting working principle (JLATE)

When the air source pressure enters the middle cavity between the two pistons of the cylinder from the air port (2), it causes the two pistons to separate and move toward both ends of the cylinder, forcing the springs at both ends to compress, and the air in the air chambers at both ends is discharged through the air port (4). The two piston racks synchronously drive the output shaft (gear) to rotate counterclockwise. After the air source pressure is reversed through the solenoid valve, the two pistons of the cylinder move toward the middle direction under the elastic force of the spring. The air in the middle air chamber is discharged from the air port (2). At the same time, the two piston racks synchronously drive the output shaft (gear) Rotate clockwise. (If the piston is installed in the opposite direction, the output shaft will rotate in the opposite direction when the spring returns, which is the single-acting reverse type)


JLAW pneumatic actuator series

Double-acting working principle (JLAWD)

(See Figure 1) When the pressurized air source enters the air chamber of the cylinder (left A and right A) from the air port (A), the two pistons and the piston rod assembly move synchronously toward the right end of the cylinder, (left B and right B) The air in the air chamber is discharged through the air port (B). At the same time, the piston assembly synchronously drives the fork rotating shaft to rotate counterclockwise, completing the angular stroke of 0°-90°. After the solenoid valve is ventilated, when the air source pressure enters the air chambers at both ends of the cylinder (left B and right B) from the air port (B), the two pistons and the piston rod assembly move toward the left end of the cylinder (left A and right A). The air is discharged through the air port (A), and at the same time, the piston assembly synchronously drives the fork rotating shaft to rotate clockwise, completing the 90°-0° movement.


Single-acting working principle (JLAWE)

(See the picture on the right) When the pressurized air source enters the air chamber of the cylinder (left A and right A) from the air port (A), the two pistons and the piston rod assembly move synchronously toward the right end of the cylinder, forcing the spring assembly to compress, (left B and right B) The air in the air chamber is discharged through the air port (B). At the same time, the piston assembly synchronously drives the fork rotating shaft to rotate counterclockwise, completing the angular stroke of 0°-90°. After the solenoid valve is ventilated, the air source pressure generates elastic force from the spring assembly at the pressure relief (right B) end of the air port (A), causing the two pistons and the piston rod assembly to move toward the left end of the cylinder. At the same time, the piston assembly synchronously drives the fork to rotate in the axial direction. Rotate clockwise to complete the 90°-0° motion.