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Description of the development of pneumatic diaphragm actuators

1, the old pneumatic film actuator:
The executive agency is one of the most widely used executive agencies in the past. It usually accepts standard signal pressure of 20~100KPa, and has the advantages of simple structure, reliable operation, convenient maintenance and low price. The actuator is divided into two types: positive and negative: domestic model ZMA (positive acting) and ZMB (reaction), which means: Z-actuator type; M-pneumatic film type; A-positive action; B -reaction. When the signal pressure increases, the push rod moves downwards as the positive acting actuator; conversely, when the signal pressure increases, the push rod moves upwards as the reaction type actuator. In terms of structure, the positive and negative acting mechanisms are basically the same, and are composed of a membrane cover, a corrugated diaphragm, a push rod member, a spring, a bracket, and the like. By adding spacers to the positive-acting structure and replacing individual parts, it becomes a reaction type.

2, fine small pneumatic film actuator
It is designed primarily for the problem of bulky and reactive reliability of older film actuators. In terms of reducing weight and height, it changes the single spring of the old structure into multiple springs, and places the spring directly in the upper and lower membrane cover, so that the bracket is greatly reduced and reduced; in terms of reliability, the reaction will be the old-fashioned actuator The deep corrugated rolling diaphragm was changed to an "O" ring seal. The push rod in the old structure was not guided, and the smoothness of the movement was poor, while the fine small actuator increased the orientation.
In summary, the compact actuators are characterized by high reliability, small size and light weight. Its model: positive action ZHA, reaction ZHB

Advantages of the membrane actuator structure:
1; simple structure
2; convenient maintenance
3; low price

Disadvantages of the membrane actuator structure:
1; diaphragm structure can only be used for valves with shorter strokes.
2; the diaphragm is under low pressure, and the spring has to offset most of the pressure, the remaining output force is very small; in order to increase the output force, the usual practice is to increase the size, so that the size and weight of the actuator change Great
3; The gas pressure of the factory is usually 500~700kPa, it only uses 250KPa, and the air pressure is not fully utilized.

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