SkyTrak 6036 Service Manual - Manual (Page 163)

Section 9 Hydraulic System
Model 6036/6036T S/N 9B0500 thru 14833 9-13
PRESSURE
COMPENSATOR
SPRING
PORT C2
COMPENSATOR
SPOOL
PORT C1
MAIN
SPOOL
INTERNAL
SENSING
PASSAGE
PRESSURE PRESSURE
Fig. 9.9 Working Section Compensator Valve with
Spool Shifted - Sectional View
Center Position
When the joystick is placed in the center or neutral
position, no PWM signals are sent to the raise or
lower pulsar solenoid. The control valve spool is
centered so that supply pressure is blocked at port
P and supply pressure in the supply passage acts
on the compensator spring to keep the valve
closed. Load sensing pressure is vented back to
the reservoir through the inlet relief valve, Fig.
9.10.
Raise Position
When the joystick is placed in the raise position,
PWM signals are sent to the boom raise pulsar
solenoid. The control valve spool is shifted so that
supply pressure is directed through ports P to C1
to the base end of both left and right boom hoist
cylinder pistons. Return oil from the rod end of the
boom hoist cylinder pistons is directed back to the
control valve through ports C2 to T and the return
line to the filter and reservoir. If supply pressure
reaches 2650 psi
(182,6 bar), the inlet relief valve
will open allowing hydraulic oil to return to the
reservoir, Fig. 9.10.
The pilot valve reduces the pressure to 200 psi
(13,8 bar). This filtered supply is directed to the
pilot stage and pulsar solenoids in the raise/lower
working section.
All return oil flows to the return filter and reser-
voir. If the filter becomes clogged, hydraulic oil
will bypass the filter when the pressure reaches 10
to 15 psi (0,69 to 1,03 bar).
9.3.3 Boom Raise/Lower Circuit
a. Description
Hydraulic pressure is applied in the boom raise/
lower circuit by the 30 gpm section (rear half) of
the tandem pump, which draws its fluid through a
suction strainer in the reservoir, Fig. 9.10. The
supply pressure enters the inlet section and is
directed to the pilot valve filter, and through the
supply passage to the raise/lower working section.
When the supply pressure reaches 200 psi
(13,8
bar), the bypass (compensator) valve opens to
return. The inlet relief valve is set at 2650 psi
(182,6 bar).
MK0070
Lower Position
When the joystick is placed in the lower position,
PWM signals are sent to the boom lower pulsar
solenoid. The control valve spool is shifted so that
supply pressure is directed through ports P to C2
to the rod end of both left and right boom hoist
cylinder pistons. This supply pressure also pilots
open the counterbalance valve. The open
counterbalance valve allows return oil from the
base end of the hoist cylinders pistons to be
directed back to the control valve through ports C1
to T and the return line to the filter and reservoir.
If supply pressure reaches 2650 psi
(182,6 bar),
the inlet relief valve will open allowing hydraulic
oil to return to the reservoir, Fig. 9.10.
NOTE: Shifting the raise/lower working section
spool manually by moving the optional valve lever
toward the control valve will also actuate the hoist
cylinder to raise the boom.
e. Manual Override
Working sections can be operated manually using
a ball-handle rod, or if not available, a 3/8-16
threaded rod or bolt, Fig. 9.8. This is very useful
for checking valve operation or for use in emer-
gency boom operation. The main spool can be
shifted 0.25" (6,4 mm) which is equivalent to
22-1/2 degrees of rod movement. The rod is
threaded into an adapter which is linked to the
main spool through a pivot shaft and clevis.
Details of the override arrangement are shown in
Fig. 9.42.
f. Outlet Section
The outlet section of the control valve acts as an
end cover and manifold for the valve stack.
Details of the outlet section arrangement are
shown in Fig. 9.40.
PORT C2 PORT C1