TM 5-3805-260-24
Bowl Down
When the bowl valve spool in control valve (3) is held
in DOWN position (A), the oil from pump (20) in line (16)
goes out of the control valve through line (5) into the
head ends of bowl cylinders (2). The DOWN position of
the bowl valve spool also opens a passage for the oil in
vent line (8) to go through the control valve to the tank.
The pump oil in the head ends of cylinders (2) moves the
pistons and rods, connected to the bowl, down and
lowers the bowl. The pistons push the oil from the rod
ends of the bowl cylinders and opens carry check valves
(4). The check valves open because the oil in vent line
(8) can go to the tank. The rod end oil, pushed through
valves (4), goes through line (9), through control valve
(3), through return oil line (13) into the filter and tank
(19).
Relief valve (10) in control valve (3) prevents high oil
pressure damage to the parts in the oil circuit of pump
(20). If pump oil pressure increases to approximately
2525 psi ( 177 kg/cm2) (17 425 kPa) the pressure opens
the relief valve and the pressure can not increase any
farther.
Release the control lever and a spring on the bowl
valve spool moves it to HOLD position (B). Now, the
pump oil goes to the filter and tank and the passage for
the oil in vent line (8) is closed. The stopped oil in vent
line (8) keeps the carry check valves closed. The bowl
can not go down because the pistons, in the bowl
cylinders, can not push oil through the closed carry
check valves.
Bowl Up (No Illustration)
Hold the control lever in the UP position and it keeps
the bowl valve spool in UP position (C), in control valve
(3). The UP position of the bowl valve spool opens a
passage to the tank for the oil in vent line (8) and also
lets the pump oil, in the control valve, go through line (9)
to carry check valves (4). With vent line (8) open to the
tank, the pump oil in line (9) goes through carry check
valves (4) into the rod ends of bowl cylinders (2). The
pump oil moves the pistons and rods, connected to the
bowl, up to lift the bowl. The pistons push the oil out of
the head ends, of the bowl cylinders, through line (5) to
control valve (3). The oil goes through the control valve
and through return oil line (13) into the filter and tank
(19).
Release the control lever and the spring on the bowl
valve spool moves it to HOLD position (B). The HOLD
position of the bowl valve spool closes the passage to
the tank for the oil in vent line (8) and carry check valves
(4) close. The movement of the bowl stops when the
check valves close and the bowl control lever must be
moved to either lower or lift the bowl.
4-17
