三位式氣動(dòng)執(zhí)行器是一種特殊規(guī)格的執(zhí)行機(jī)構(gòu)，提供了0°，45°，90°或0°，90°，180°的三位式操作方式。中間位置是依靠?jī)蓚�(gè)輔助活塞的移動(dòng)產(chǎn)生的機(jī)械制動(dòng)來(lái)實(shí)現(xiàn)的。中間位置是可調(diào)的。如90°行程的執(zhí)行器能提供20°，30°，50°，70°等的中間位置。其工作原理中下：
Three position actuator provide an operation of 0°, 45°, 90°or 0° , 90°, 180°，The midway position is achieved by a mechanical stop of movement on the 2 auxiliary pistons. This midway stop positions adjustable. Example： 90°actuator can provide 20°, 30°, 40°, 50° , 70°etc. Following is the principle of operation：

1，全關(guān)位置。如圖1所示，全閉位置是在氣源進(jìn)入4口， 2口排出空氣后實(shí)現(xiàn)的。
1, Fully Closed Position
From chart 1 we can see that this position is obtained when air is supplied to port 4 and port 2 is in the state of exhaust air.

2，全開(kāi)位置。如圖2所示，全開(kāi)位置是在氣源同時(shí)進(jìn)入2口和C口，4口和D口排出空氣后實(shí)現(xiàn)的。
2, Fully Open Position
From chart 2 we can see that this position is obtained when air is supplied to port 2 and port C, meantime, port 4 and port D are in the state of exhaust air.

3，中間位置。如圖3所示，中間位置是在氣源分別進(jìn)入2口和D口，4口和C口排出空氣后實(shí)現(xiàn)的。在實(shí)現(xiàn)中間位置的過(guò)程中，氣源供到D口，迫使輔助活塞向中心移動(dòng)，推桿作為機(jī)械限位使內(nèi)部活塞在設(shè)定的中間位置停止。
3, Midway Position
From chart 2 we can see that this position is obtained when air is supplied to port 2 and port D, meantime, port 4 and port C are in the state of exhaust air. In fact that the midway position is achieved by a mechanical stop of movement on the two auxiliary pistons.