SkyTrak 6036 Service Manual - Manual (Page 154)

Section 9 Hydraulic System
9-4 Model 6036/6036T S/N 9B0500 thru 14833
c. Working Sections
There are two parallel working sections of the
control valve, Fig. 9.2, one for controlling the boom
raise/lower function and one for controlling the
boom extend/retract function, Fig. 9.3.
The boom raise/lower working section contains:
• A spring centered spool that is shifted by
the operator joystick and its associated
cable that directs the hydraulic oil. Func-
tion and operation of the spool is ex-
plained in the raise/lower circuit, para-
graph 9.2.2.
• A load-drop check valve to prevent a load
from dropping when the operating spool is
shifted.
• Two work ports that allow the hydraulic oil
to flow to and from the cylinders.
• One port relief valve, set at 2850 ± 50 psi
(196,4 ± 3,4 bar). Function of the relief
valve is explained in the boom raise/lower
circuit, paragraph 9.2.2. Operation of the
valve is explained in paragraph 9.2.1.b.
The boom extend/retract working section contains:
• A spring centered spool that is shifted by
the operator joystick and its associated
cable that directs the hydraulic oil. Func-
tion and operation of the spool is ex-
plained in the extend/retract circuit,
paragraph 9.2.3.
• A load-drop check valve to prevent a load
from dropping when the operating spool is
shifted.
• Two work ports that allow the hydraulic oil
to flow to and from the cylinders.
• Two port relief valves, set at 2850 ± 50 psi
(196,4 ± 3,4 bar). Function of the relief
valves is explained in the boom extend/
retract circuit, paragraph 9.2.3. Operation
of the valves is explained in paragraph
9.2.1.b.
Warning
• If anyone is injured by or if any hydraulic fluid
is injected into the skin, obtain medical
attention immediately or gangrene may
result.
• Wear appropriate eye protection. Hydraulic
fluid can cause permanent eye injury. Do
not wear loose fitting clothing when servicing
the forklift.
MAIN
RELIEF
VALVE
WORK
PORTS
INLET
PORT
OUTLET
PORT
BOOM
RETRACT
PORT
RELIEF
VALVE
BOOM RAISE
PORT RELIEF
VALVE
INLET
SECTION
OUTLET
SECTION
PARALLEL
WORKING
SECTIONS
PLUG
MA2090
d. Outlet Section
The outlet section is an end cover where the outlet
port is located on the side of the cover, Fig. 9.3.
9.2.2 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. 9.4. Supply
pressure is directed to either side of the right and
left boom hoist cylinder pistons, by the shifting of a
spool in a directional control valve found in the
main control valve assembly. The spool is shifted
by the operator joystick and its associated
control cable. The joystick positions for raising
and lowering the boom are as follows:
Center Position
When the joystick is placed in the center or neutral
position, the directional control valve spool is
positioned so that supply pressure is directed
through ports F to C, Fig. 9.4, to the return filter
and reservoir, Fig. 9.4. 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).
Fig. 9.3 Main Control Valve (Cable Control)
BOOM EXTEND
PORT RELIEF
VALVE