Compressed air is supplied from the main to port 1 and fills the internal chamber of the directional valve. Since the effective area of piston 6 of plunger 5 is greater than that of piston 7, plunger 5 is held in the position shown by the difference in the forces exerted by the pressure. I n the same way, plunger 8 is held in the position shown. At this, both ports, 2 and 3, connected to the actuator (operating cylinder or device), are connected to port 4, which leads to the atmosphere. When pilot air under pressure is admitted into port 9, plunger 8 begins to move to the left, and compressed air from port 1 is admitted into port 3 and further into the actuator. Port 2, as before, is connected to the atmosphere. If port 9 is connected to the atmosphere and compressed air is admitted into port 10, then plunger 5 is shifted to the left, and air from port 1 is admitted into port 2. At the same time, plunger 8 is pushed back to the right to its initial position (as shown) and port 3 is connected to the atmosphere through port 4.
$3681$SHP,FC$