Lull 944E-42, Service Manual

Page: 402 / 844

Hydraulic System
8.152 Model 644E-42/944E-42 Rev. 6/04
8.8.55 Frame Sway Circuit Description
Hydraulic flow is applied in the frame sway circuit (see
page 8.90 or page 8.92, and page 8.94 or page 8.96) by
the secondary section of the hydraulic gear pump to the
“Inlet” Port on the Main Control Valve. The primary
section of the pump provides hydraulic flow to the “P” Port
on the Accumulator Charge/Secondary Function Valve
out the “EF” Port to the “Inlet” Port at the Main Control
Valve. System pressure is directed to either side of the
frame sway cylinder by the shifting of the spool in the
Main Control Valve. The spool is shifted by pilot pressure
from the Accumulator Charge/Secondary Function Valve
Out the “PIL” Port, to the “P” Port of the Frame Sway
Joystick. Pressure is regulated by the position of the
joystick.
A secondary function of this circuit is to maintain oil
pressure in the Stabilizer Cylinder as the Frame Sway
function is used and/or when the vehicle moves along
uneven Terrain. System pressure from the “P Gauge”
Port on the Main Control Valve enters the “P” Port on the
Stabilizer Cylinder Block and passes a Pressure Relief
Valve. From here the oil will fill the Rod End or Base End
of the Stabilizer Cylinder depending on which end
requires the oil. This is regulated by the position of the
Rear Axle and the amount of oil pressure in the circuit. Oil
Pressure of 100 PSI (6,89 bar) is maintained in the circuit
by the Pressure Relief Valve which will dump excess
pressure out the “T” Port of the Stabilizer Cylinder Block
and send it to the Hydraulic Reservoir unfiltered.
a. Frame Sway LEFT (See page 8.90 or page 8.92)
With the Joystick moved to the LEFT, pilot
pressure from Port “1,” (SN 18460 and Before)
or Port “2” (SN 18461 and After), shifts the
spool in the Frame Sway section of the Main
Control Valve. System pressure from the Pump is
directed to the Main Control Valve then to the Frame
Sway Cylinder “FTB” Port. Oil passes through a 0.048"
Orifice at the Frame Sway Cylinder base end.
Return oil flows from the rod end of the cylinder through
a 0.041" Orifice and Check Valve to the Stabilizer
Cylinder “FTR” Port. Oil passes through a Solenoid Valve
in the Stabilizer Cylinder Block Port “V” and returned to
the Main Control Valve out the “Outlet” Port, then through
the Oil Cooler, to the Return Filter and then to the
Hydraulic Reservoir.
b. Frame Sway RIGHT (See page 8.94 or page 8.96)
With the Joystick moved to the RIGHT, pilot
pressure from Port “1”, (SN 18460 and Before)
or Port “2” (SN 18461 and After), shifts the
spool in the Frame Sway section of the Main
Control Valve. System pressure from the Pump is
directed to the Main Control Valve then to the Stabilizer
Cylinder “V” Port. Oil passes through Solenoid Valve and
Stabilizer Cylinder base end before exiting through the
“FTR” Port.
Return oil flows to the “FTR” Port on the Frame Sway
Cylinder through a 0.041" Orifice to the base end of the
cylinder. Oil exits the Frame Sway Cylinder through a
0.048" Orifice and Check Valve at the “FTB” Port and
returns to the Main Control Valve out the “Outlet” Port,
then through the Oil Cooler, to the Return Filter and then
to the Hydraulic Reservoir.
MT3760
MT3770