6-12 4181383 First Edition
HYDRAULICS
6
Raise Circuit Schematic and Theory
of Operation
See Figure 6-8.
System Conditions:
• Engine running
• Traction control switch in the OFF position
• Raise/lower joystick in the RAISE position
NOTES
• See “Raise/Lower Circuit—Theory of Operation” on
page 4-30 for the electrical operation of this circuit.
• All cylinders operate the same way; left rear cylinder
shown.
Operating-pressure oil is supplied to port “P” of the lift
valve by the steering circuit. (See “Steering Circuit
Schematic and Theory of Operation” on page 6-10.) With
the raise solenoid valve energized, and the
lowering/proportional valve de-energized, oil flows
against the check valves of each valve, and exits the lift
valve assembly through ports “C1” through “C5” in
parallel to the rod end of each lift cylinder.
Oil passes through a 0.040 inch (1.016 mm) orifice at the
rod end of each lift cylinder, and oil is applied to the back
of the piston, causing the cylinder to retract, raising the
cutting units.
Oil from the piston end of the lift cylinders flows back to
the lift valve assembly through ports “C6” through “C10”
in parallel. Oil exits the lift valve assembly through port
“T,” and flows to the return filter, and oil cooler and back
to the hydraulic oil tank.
If there is resistance to flow at the lift cylinders, causing
oil pressure to rise above the steering relief valve setting
of 1740 psi (120 bar), the steering relief valve will open.
Oil flow will then be dumped back to the hydraulic oil tank
through the return filter and oil cooler.
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