Page 53 - PNEUMATIC SYSTEM INSTRUMENT

THREE-WAY, TWO-POSITION VALVES

2(A)

1(P) 3(R)

Figure 7.4: Three-way valve cross section and schematic symbol

Three-way, two-position valves consist of three ports connected

through passages within a valve body. The valves pressurize and

exhaust one outlet port to control a single-acting cylinder or pilot

another valve.

Three-way valves direct pressurized air to the cap-end side of the

cylinder. Shifting the spool to the other extreme position blocks flow

and pressure to the actuator. The actuator is connected to the exhaust

passage; therefore, spring force or gravity must return the rod to its

original position.

36