Lull 944E-42 Service Manual - Manual (Page 406)

Hydraulic System
8.154 Model 644E-42/944E-42 Rev. 6/04
8.8.57 Attachment Tilt and Slave Circuit
Description (Single Joystick
)
System pressure is applied in the attachment tilt and
slave cylinder circuit (see page 8.100 and page 8.104)
from the attachment tilt section of the Main Control Valve.
Fluid flow is directed to either side of the attachment tilt
and slave cylinder pistons by shifting of the spool in the
attachment tilt section of the main control valve
assembly. The spool is shifted by pilot pressure provided
from the Accumulator Charge/Secondary Function Valve
to the Single Joystick Pilot Select Valve, controlled by
electrical solenoids and regulated by the position of the
joystick thumb switch.
Attachment Tilt Down Circuit (See page 8.100)
With the switch moved UP, the attachment tilts
DOWN. When the switch is in the UP position
the Thumb Switch Solenoid directs pilot
pressure from the Accumulator Charge/
Secondary Function Valve to the Single Joystick Pilot
Select Valve. Pilot pressure from the “CTA” Port on the
Single Joystick Pilot Select Valve shifts the spool in the
Main Control Valve and system pressure is directed to
the “R” Ports to the rod ends of the Attachment Tilt
Cylinder and the Slave Cylinders.
The extension of the Slave Cylinders is fixed by the
position of the Boom so that only the Attachment Tilt
Cylinder is retracted to tilt the attachment downward. The
pressure from the Main Control Valve opens the
Counterbalance Valve and allows return oil from the base
of the Attachment Tilt Cylinder to flow out the “E” Ports of
the cylinders to the attachment tilt section of the Main
Control Valve, pass through the Oil Cooler, to the Return
Filter and then drains to the Hydraulic Reservoir.
If circuit pressure reaches 4000 psi (276 bar) the port
relief valve will open and allow hydraulic oil to return to
the Oil Cooler, return filter and to the reservoir. In any
case, if the return filter becomes plugged the indicator
light will come ON, indicating that return hydraulic oil will
bypass the filter when pressure reaches 25 psi (1,7 bar)
and return to the reservoir unfiltered.
c. Attachment Tilt Up Circuit (See page 8.104)
With the switch moved DOWN, the attachment
tilts UP. When the switch is in the DOWN
position the Thumb Switch Solenoid directs pilot
pressure from the Accumulator Charge/
Secondary Function Valve to the Single Joystick Pilot
Select Valve. Pilot pressure from the “CTB” Port on the
Single Joystick Pilot Select Valve shifts the spool in the
Main Control Valve and system pressure is directed to
the “E” Ports to the base ends of the Attachment Tilt
Cylinder and the Slave Cylinders.
If circuit pressure reaches 4000 psi (276 bar) the port
relief valve will open and allow hydraulic oil to return to
the Oil Cooler, return filter and to the reservoir. In any
case, if the return filter becomes plugged the indicator
light will come ON, indicating that return hydraulic oil will
bypass the filter when pressure reaches 25 psi (1,7 bar)
and return to the reservoir unfiltered.
Return oil from the rod side of the Attachment Tilt
Cylinder is directed back to the attachment tilt section of
the Main Control Valve. Oil passes through the Oil
Cooler, to the Return Filter and then drains to the
Hydraulic Reservoir. If the return filter becomes plugged
the indicator light will come ON, indicating that return
hydraulic oil will bypass the filter when pressure reaches
25 psi (1,7 bar) and return to the reservoir unfiltered. MT3780
MT3790