Structural principle of diaphragm actuator

Pneumatic diaphragm actuator refers to the use of an elastic diaphragm to convert input air pressure into thrust on the push rod, which causes corresponding displacement of the valve core and changes the valve opening. The pneumatic piston actuator outputs thrust through the piston inside the cylinder. Due to the high allowable pressure in the cylinder, it can obtain a larger thrust and is easy to control long stroke actuators. A typical pneumatic thin film actuator mainly consists of an elastic thin film, a compression spring, and a push rod.

 

The output of pneumatic diaphragm actuators is displacement, which is related to signal pressure. When the specifications of the actuator are determined, A and K are constants, so the displacement of the actuator is proportional to the signal pressure. When the signal pressure enters the membrane chamber, this pressure is multiplied by the effective area of the membrane to obtain thrust, causing the push rod to move and the spring to be compressed until the reaction force generated by the spring is balanced with the thrust on the membrane. The greater the signal pressure, the greater the thrust, and the greater the displacement of the push rod, i.e. the compression of the spring. The displacement range of the push rod is the stroke of the actuator. The push rod moves from zero to full stroke, and the valve moves from fully open (or fully closed) to fully closed (or fully open).