6-22 4203780 First Edition
HYDRAULICS
6
Mow Circuit (OFF) Theory of
Operation
System Conditions:
• Engine running
• Cutting units lowered
• Mow switches in OFF position
• Park brake released
NOTE
See “Mow Circuit—Theory of Operation” on page 4-36
for the electrical operation of this circuit.
Oil Supply to Deck Valves
Oil is drawn from the hydraulic tank through a 100-mesh
screen, and enters the gear pump, supplying oil to all four
pump sections. Sections 2 (front deck), 3 (left wing deck),
and 4 (right wing deck) supply operating-pressure oil to
port “P” of the corresponding cutting unit deck valves.
Motor Shutdown/Blade Braking
Operating pressure oil flows to the relief valve (3000 psi)
and the solenoid valve. With the mow switch(es) in the
OFF position, the solenoid valves are de-engerized,
opening the valves. Oil can then flow through the valves,
returning to the hydraulic tank. With the oil pressure/flow
diverted to the hydraulic tank, the blade brake check
valves close (630 psi), preventing oil flow through the
motors.
The blade brake check valves have a second pilot line on
the motor side. As oil flow is stopped to the motors, the
motors will act a pumps as they rotate during shutdown.
This pilot line allows the valve to close slowly, acting as a
cutting unit motor brake. This prevents a sudden
shutdown of the motors.
Circuit Relief
The mow circuit is protected by a pilot-operated relief
valve. The relief valve will open if the oil pressure in the
circuit reaches 300 psi, allowing oil to bypass the circuit
and return directly to the hydraulic tank.
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