6-20 4203780 First Edition
HYDRAULICS
6
Mow Circuit (ON) Schematic and
Theory of Operation
System Conditions:
• Engine running
• Cutting units lowered
• Mow switch(es) in ON position
• Park brake released
NOTES
• See “Mow Circuit—Theory of Operation” on
page 4-36 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 (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.
Mow Circuit
Operating pressure oil flows to the relief valve (3000 psi),
solenoid valve, and the brake valve pilot port (630 psi).
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 brake
valve (630 psi). 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, allowing oil to bypass the circuit
and return directly 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. In the
event of the return filter becoming plugged, a 25-psi
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 in the event of a hose failure.
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