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Classification of pneumatic actuators

2020-06-02
1.Double acting actuator

The switching action of the actuator is driven by the air source, which is called DOUBLEACTING (double acting).

The selection of double-acting actuators uses DA series pneumatic actuators as examples:

The output torque of the rack and pinion actuator is obtained by multiplying the piston pressure (supplied by the air source pressure) by the pitch circle radius (force arm). And the friction resistance is small and the efficiency is high. The output torque is linear in both clockwise and counterclockwise rotations. Under normal operating conditions, the recommended safety factor for double acting actuators is 25-50%.

2, Single acting actuator

SPRINGRETURN (single-acting) ON / OFF action is only driven by air source, and the spring is reset when closed.

Take SR series pneumatic actuator as an example. In the application of spring return, the output torque is obtained in two different operations. According to the stroke position, each operation produces two different torque values.

The output torque of the spring-return actuator is obtained by multiplying the force (air pressure or spring force) by the force arm: the output torque is obtained by the air pressure entering the middle cavity compression spring, which is called "air stroke output torque" in In this case, the pressure of the air source forces the piston to turn from 0 degrees to 90 degrees, resulting in a reaction force due to the compression of the spring.

The torque gradually decreases from the maximum value at the starting point to the second condition: the output torque is obtained by the spring restoring force acting on the piston when the middle cavity is out of air, which is called "spring stroke output torque". In this case, due to the spring extension Long, the output torque gradually decreases from 90 degrees to 0 degrees. As mentioned above, the single-acting actuator is designed based on the production of a balanced torque under two conditions. In each case, by changing the relationship between the number of springs on each side and the air source pressure, it is possible to obtain an unbalanced torque. Two conditions can be obtained in spring return applications: out-of-gas opening or out-of-gas closing. Under normal operating conditions, the recommended safety factor for spring-return actuators is 25-50%.

Pneumatic actuator features:

1. Compact double-piston gear, rack-type structure, precise meshing, high efficiency, and constant output torque.

2. The aluminum cylinder, piston and end cover are the lightest compared to actuators of the same structure.

3. The cylinder body is extruded aluminum alloy and hard anodized. The inner surface has a hard texture, high strength and high hardness. Sliding bearings made of low-friction materials avoid direct contact between metals, low friction coefficient, flexible rotation, and long service life.

3. The installation and connection dimensions of pneumatic actuators and valves are designed according to international standards ISO5211, DIN3337 and VDI / VDE3845, which can be interchanged with ordinary pneumatic actuators.

4. Air source hole conforms to NAMUR standard.

5. The bottom shaft mounting hole (in line with ISO5211 standard) of the pneumatic actuator is double square, which is convenient for the valve with square rod to be installed linearly or 45 °.

6. The top and top holes of the output shaft conform to the NAMUR standard.

7. The adjusting screws at both ends can adjust the opening angle of the valve.

8. Double-acting and single-acting (spring return) of the same specifications.

9. You can choose the direction according to the needs of the valve and rotate clockwise or counterclockwise.

10. Install solenoid valve, positioner (opening indication), return device, various limit switches and manual operation devices according to user needs.