As the ball valve can be opened and closed only by turning the ball 1 / 4 circle, it belongs to the partial rotary angular stroke valve, so the pneumatic actuator used in it also selects the partial rotary type.
At present, the commonly used partial rotary pneumatic actuator of ball valve can be divided into rack and pinion type, sector blade type and fork type according to the transmission mode, and the fork type can be divided into external fork type and internal fork type according to the cylinder diameter.
The structure of fan blade pneumatic actuator is shown in the figure. In the sector vane pneumatic actuator, one blade divides the air chamber into two parts. The blade consists of a solid main body and a sealing device on the 2 sides of the main body. The shaft is an integral part of the blade. By applying air pressure to port a, the blade rotates 90 degrees. The air pressure at port B moves the blade back to its original position. The output torque characteristics of the sector vane pneumatic actuator are the same as those of the double acting rack and pinion pneumatic actuator, which are both horizontal linear characteristics.