6-20 4203781 First Edition
HYDRAULICS
6
Mow Circuit (ON) Schematic and
Theory of Operation
System Conditions:
• Engine running
• Cutting units lowered
• Mow switch(es) in the ON position
• Park brake released
NOTES
• See “Mow Circuit—Theory of Operation” on
page 4-37 for the electrical operation of this circuit.
• The function of each deck valve is the same, except
where noted.
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 (right deck), 3 (front deck),
and 4 (left wing deck), supply operating pressure oil to
port “P” of the corresponding cutting unit deck valves.
Mow Circuit
Operating pressure oil flows to the 3000 psi (207 bar)
relief valve, solenoid valve, and the 630 psi (43 bar) brake
valve pilot port. With the mow switch(es) in the ON
position, the solenoid valve shifts, applying pressure
against the check valve, stopping oil flow through the
solenoid valve. Operating pressure oil increases and
opens the 630 psi (43 bar) brake valve. Operating
pressure oil flows out of the valve body through port “A,”
driving 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 3000 psi (207 bar), allowing oil to bypass
the circuit and return to the hydraulic tank.
Oil Return
Oil returning from the motors enters the valve body at
port “B,” and flows through the pilot-operated brake valve,
exiting the valve body at port “T” and is returned to the
hydraulic tank:
Right Wing Deck: The oil from this motor is routed
directly to the hydraulic tank.
Front Deck and Left Wing Deck: The oil from these
decks is routed through the oil cooler and through a
10-micron filter to remove debris from the oil. If the
return filter becomes plugged, a 25 psi (1.7 bar)
pressure switch will activate the “Return Filter” light
on the control panel and return filter will be
bypassed.
Oil that leaks through the motors drains back to the
hydraulic tank through the case drain hoses. A check
valve located in the return line at the bottom of the
hydraulic tank prevents oil from back-feeding into the oil
return lines if a hose fails.
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