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PRESSURE
RELIEF VALVE
MAIN PRESSURE
OIL GALLEY
(INTERNAL)
MAIN RETURN
OIL GALLEY
(INTERNAL)
MINI-VALVES
MOTOR/PUMP
ASSEMBLY
PUMP INLET
OIL
RESERVOIR
PUMP
OUTLET
Figure 1-3. Pressure Relief Valve Not
Functioning
Figure 1-2.
a. Oil Reservoir - Main oil supply. Approximately
two quarts.
b. Motor/Pump Assembly - A positive displace-
ment gear type pump provides the necessary oil
pressure and volume.
c. Pressure Relief Valve - Provides an alternate oil
path when the hydraulic cylinders reach the end of
their stroke.
d. Electro/Hydraulic Mini-Valve Assemblies -These
direct the fluid to the appropriate hydraulic cylin-
ders.
e. Hydraulic Lines, Fittings, Connections - They
provide a path for the hydraulic oil.
f. Hydraulic Cylinders - They convert the hydraulic
fluid pressure and volume into mechanical motion.
1-2. Component Operation
a. Motor/Pump Operation
The motor/pump assembly is a gear type pump that
provides the oil pressure and volume for the entire
hydraulic system. The pump has an inlet side and
an outlet side. The inlet side is connected to the
reservoir which provides the oil supply. The reser-
voir has a very fine mesh screen strainer which
prevents foreign material from entering the oil sys-
tem.
The output line of the pump is connected to the main
oil galley which is internal and common to all the
hydraulic mini-valves and pressure relief valve.
Also, common to the hydraulic mini-valves and
pressure relief valve is an oil galley that internally
connects to the oil reservoir to provide a return path
for the hydraulic oil. See figure 1-2.
b. Pressure Relief Valve
This device provides an alternate oil path when the
hydraulic cylinders reach the end of their stroke
and the pump continues to run. If this path were not
provided, the pump motor would stall because the
oil cannot be compressed. The pressure relief
valve is directly connected to the mini-valve bodies
and shares both the common internal main pres-
sure oil galley, and the return oil galley, that inter-
nally connect to the reservoir.
Figure 1-4. Pressure Relief Valve Functioning
050305.06
PRESSURE RELIEF
ADJUSTMENT NUT
PRESSURE
GAUGE
SPRING
LOADED
PLUNGER
PRESSURE
RETURN
050305.07
PRESSURE RELIEF
ADJUSTMENT NUT
PRESSURE
GAUGE
SPRING
LOADED
PLUNGER
OIL LINE
FROM
PUMP
OIL RESERVOIR
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