H-9
35 Series 4WD, Model - 3535, 4035, 4535 and 5035 SM June’08
incoming high pressure fluid from the engine
driven pump to the manual pump inlet.
A small amount of steering effort must always
be supplied throughout a turn to add the
extra 15 to 20 lb/in
2
pressure to whatever the
pump is supplied to the manual pump.
This gives “steering feel” while providing
sufficient force to over come the resistance
of the control valve spool centering spring.
As soon as the manual steering effort ceases,
the 15 to 20 lb/in
2
pressure differential in the
manual pump to control valve spool centres
and the fluid in steering circuit becomes
static. The fluid moving from the engine drive
pump into the centered control valve is
directed back onto the reservoir.
Fluid from the engine driven pump is directed
by control valve to manual pump inlet or
returned to the reservoir when not needed.
Fluid supplied by the engine driven pump
never goes directly to the steering cylinder.
i. Turning :
The initial turn of the steering wheel driving
the attached manual pump, moves the
control valve spool and opens the port to the
manual pump and the steering cylinder. The
fluid from the engine driven pump enters the
control valve and this fluid passes through
the control valve spool passage into the
manual pump. The fluid the passes through
and out of the manual pump under high
pressure to and through the control valve to
the steering cylinder and against the cylinder
piston. An equal amount of fluid displaced
by the moving piston flows to the control
valve under low pressure and return to the
reservoir to supply the engine driven pump.
ii. Neutral
With no steering at the manual pump, the
control valve spool is in the centered or
neutral position. Fluid in the closed manual
steering circuit is static. With the spool
centered fluid flow from the engine driven
pump is directed through the open control
valve channels back to the reservoir. When
the steering wheel is turned to move the valve
spool off its centered position this fluid is
instantly available.
Steering