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Figure 11. DG5V10 with DG4S4-01 Pilot
Section IV - Pilot Valve Section
A. Spool Type - Pilot Valve Section
To maintain proper control, closed center pilot spools are
normally used in two stage valves. In most cases, a number
‘‘6’’ type pilot spool is used.
When a type ‘‘4’’ or ‘‘8’’ main stage spool is used, the letter
‘‘V’’ is inserted into the pilot valve model code.
B. Spool Positioning - Pilot Valve Section
Pilot spools are positioned within the valve by special spool
arrangements. The three basic pilot valve spool arrangements
are spring centered, spring offset and detents. The following
paragraphs (1 through 3) describe pilot spool arrangements.
1. Spring Centered: A spring and washer are installed at
each end of the pilot valve spool. The spring moves the
spool until the washer contacts the end of the valve body. In
the deenergized condition of the pilot valve, the spool is held
in center position within the body by the springs and washers.
2. Spring Offset: Spring offset models use one spring and
washer to return the pilot valve spool to an offset position. In
this model, a solenoid is completely removed from the spring
end of the pilot valve. Solenoid operating power is reduced
by the sacrifice of the center spool position.
3. Detents: A detent mechanism is installed on one or both
ends of the pilot valve spool. Detent valve solenoids can be
momentarily energized to the correct position and then power
may be removed from the solenoid. This reduces the input
control power below that of an offset model.
The detent(s) hold the pilot spool in the last position attained
until the opposite solenoid is energized. As in the offset
valve, solenoid power is reduced by the sacrifice of the
center spool position.
C. Methods of Control - Pilot Valve
The following pilot control methods are available for pilot
spool position.
Control
Model Codes
Electrical Solenoid
DG4S4-01, DG4V-3, DG4V-3S
1. Remote Pilot: Pilot valves, such as a DG3V3, are
available for use with a remote pilot source. This means that
a valve can be shifted from a remote pressure source by
other valves in the logic circuit. Refer to service parts
drawings listed in Table 1.
2. Electrical Solenoid Pilot Operation: Electrical solenoids
are attached to the pilot valve body. Internal push pins
connect the solenoid to the pilot spool. When the magnetic
field of solenoid ‘‘B’’ is energized, the solenoid armature
moves the push pin and shifts the pilot spool towards
solenoid ‘‘A’’ (see Figure 12a). When solenoid ‘‘A’’ is
energized, the pilot spool shifts toward solenoid ‘‘B’’ (see
Figure 12b). When both solenoids are de-energized, the pilot
spool shifts to center position (see Figure 12c).
