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 TM 55-1905-220-14-7
3-208. DIRECTIONAL CONTROL VALVE - MAINTENANCE INSTRUCTIONS
a. GENERAL
The directional control valve is comprised of a rectangular valve body containing a precision fitted sliding
spool in a central, longitudinal bore. Spool lands serve to divide the bore into a series of separate chambers,
and ports in the valve body lead into these chambers. The position of the spool determines which ports are
open to each other and which are sealed off from the others. Thus, oil flow is directed from one port to another
within the valve body.
b. PRINCIPLES OF OPERATION
(1) Valve Type:
SPRING CENTERED - Spring centered valves are provided with a spring and centering washer at each
end of the spool. The springs and washers center the spool within the valve body, when solenoids are de-
energized.
(2) Function
(a) Three cross section views of a valve are shown. The cross sections show location of the spool lands
and the basic valve block machining. Each cross section is provided to show porting of the valve as the spool
is moved within the valve block. Assume the spool is moved to the left within the valve body. The "P"
pressure port will connect to the "A" cylinder port and the "B" cylinder port will open to the "T" tank port.
3-3220
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