TM 5-3805-261-23-1
THEORY OF OPERATION - CONTINUED
0003 00
HYDRAULIC SYSTEM - CONTINUED
0003 00
d.
Implement Control Valves.
(1)
Each of the control levers at the sides of the steering console operates a hydraulic control valve. The con-
trol valves are mounted side by side with the pump oil passages connected and with the return oil passages
connected so that only one line is needed for each. Each valve controls a hydraulic cylinder or motor in the
hydraulic system.
(2)
The operation of each control valve is the same. The rate of oil flow from each opening in a control valve
for a hydraulic cylinder is not the same. There are valves that have approximately the same rate of oil flow
from each opening. The size of the orifices from valve spool to openings is one of the controls for the rate
of flow. The other control is the force of the spring against the valve. The spring force is not the same in
each control valve.
(3)
The resolver valve allows oil with the higher pressure in either passage opening, then through the valve
into the next passage. The higher pressure of the oil on the ball in the valve closes the valve passage with
oil that has low pressure.
(4)
The implement valve in HOLD position has pump oil at a pressure of approximately 2,150 psi (14,824
kPa) in the valve when the engine is running.
(5)
When the engine is started, the pump oil in the passage goes into the next passage and then through the
holes in the valve to the chamber for the valve that has no spring. The pump oil in the passage is stopped
by the valve spool and there is an increase in the pressure of the oil from the pump. As the pressure of the
oil gets higher, the oil pushes the valve against the force of the spring until the valve is moved to a posi-
tion, in which very little pump oil can go around the valve into the passage. There is a small amount of oil
leakage around the valve spool in HOLD position because of the high pressure of the oil in the passage.
(6)
The location of the implement valve is lower than the oil in the tank. Tank pressure forces oil through all
passages in the valve preventing air from entering the valve.
LEVER
OPENING FOR ROD END
OPENING FOR HEAD END
OF CONTROL CYLINDER
OF CONTROL CYLINDER
PASSAGE TO TANK
RESOLVER VALVE
PASSAGE FROM
VALVE
RESOLVER VALVE
SPOOL
PASSAGE TO TANK
VALVE FOR
CONTROL OF
PASSAGE
SPRING
FROM PUMP
PASSAGE FOR OIL TO
PASSAGE TO
SHUTTLE VALVE IN PUMP
SPOOL
CHECK VALVE
397-048
0003 00-27
