and the implements, from going higher than the setting
of the relief valve.
NOTE: The setting used in the pressure control valve for
the steering circuit is 1825 + 25 psi (128.3 + 1.8 kg/cm2).
The pump oil in passage ( ) goes around piston (4),
through check valve (5) and through line (8) to the
metering valve for the steering system. Piston (4) is held
in an open position by spring (15). The oil to check valve
(5) also goes through passage (7), into a chamber in
piston (4). When the pressure of the oil in line (8) and in
piston (4) is approximately 1825 psi (128.3 kg'cm2), the
force of the oil is more than the force of springs (15), and
the piston moves to a position that stops the oil from
passage (1) to line (8). When the pressure of the oil in
line (8) and the piston is less than 1825 psi (128.3
kg'cm2), spring (15) moves the piston to let more oil go
to line (8). When the pressure of the pump oil in
passage (I) is more than 1825 psi (128.3 kg,'cm2), the
action of springs (15) and the pressure of the oil in piston
(4) keeps the pressure of the oil to the steering system at
1825 psi (128.3 kg,'cm2).
9J4818 VALVE GROUPS
The pressure setting of the relief valve can be
1. Passage for oil from pump. 2. Line to control for
changed. Add to shims (14) for an increase. Remove
implements. 3. Line to control for implements. 4.
shims for a decrease. Add to shims (10) for an increase
Piston. 5. Check valve. 6. Passage to tank. 7.
in the regulation of the oil pressure to the steering
Passage in piston. 8. Line to steering system. 9. Dump
system. Remove shims for a decrease in pressure.
valve. 10. Washers and shims. 11. Spring for dump
valve. 12. Pilot valve. 13. Spring. 14. Shims. 15.
When the engine is running, the oil from the pump goes
through relief and pressure reduction valve (6), through
The pump oil in passage (1) goes through the orifice
line (7), to metering valve (2) for the steering. The
in dump valve (9) and into the chamber for spring (11).
pressure of the oil in line (7) is approximately 1825 psi
The pressure of the oil, and spring (1I), keeps dump
(128.3 kg,'cm2). The movement of the steering wheel
valve (9) closed. The oil in the spring chamber is against
operates the metering valve. When the steering wheel is
pilot valve (12) which is held closed by spring (13). If the
being turned in the direction of a right turn (clockwise),
pressure of the oil gets to approximately 3900 psi (274.2
the oil from line (7) goes through metering valve (2) and
kg/cm2), the oil in the chamber for spring (11) opens
through line (3). The oil in line (3) goes to the rod end of
pilot valve (12). This oil goes into passage (6). With
cylinder (13), and to the head end of cylinder (14) and
only the force of spring (11) on dump valve (9), the pump
the rods in the cylinders move. The cylinder rods move
oil in passage (1) opens dump valve (9) and goes into
the front wheels to positions that will let the machine
passage (6) to the tank. The relief valve prevents the
make a right turn. The oil from the head end of cylinder (
pressure of the oil, between the pump
13) and from the rod end of cylinder (14) goes through
line (4), through metering valve (2) and through line (I) to