8L-87
BACKLAP CIRCUIT SCHEMATIC
AND THEORY OF OPERATION
System Conditions:
• Engine running
• Cutting units lowered
• Traction pedal in the NEUTRAL position
• PTO switch in the BACKLAP position
• Backlap switch in the ON position
• Park brake engaged
Oil Supply to Reel Valves
Hydraulic oil is drawn from the hydraulic tank and
enters the gear pump, supplying oil to all three pump
sections. Sections 1 (front reel) and 2 (rear reel) supply
operating pressure oil to port “P” of the corresponding
reel valve.
Backlap Circuit
Operating pressure oil supplied by sections 1 and 2 of
the gear pump enters the reel valves at port “P” and is
routed to the solenoid valves. When the PTO switch is
placed in the BACKLAP position and the backlap
switch is in the ON position, the solenoid valves shift.
This routes operating pressure oil out port “B” to the
reel motors in series, driving the reel motors in the
reverse direction. The oil flow to the reel motors is
adjustable, with the backlap valve controlling the speed
of the reels for the backlap process. The adjusted rate
of oil flow will regulate reverse rotational speed and
maintain reverse motor speed as load is applied to the
reel motors. Speed adjustment settings can be main-
tained and will not affect mowing operation when
motors are shifted to mow rotation.
Circuit Relief
The backlap circuit is protected by the 2200 psi (152
bar) pilot-operated relief valves located in the reel
valves. The relief valves will open if the oil pressure in
the mow circuit reaches 2200 psi (152 bar), routing the
oil through port “T” of the reel valves to the oil cooler,
return filter, and then the hydraulic tank.
Oil Return
Return oil from the reel motors enters the reel valves at
port “A” and flows through the solenoid valves to the oil
cooler, return filter, and then the hydraulic tank.
The return filter and oil cooler are equipped with crack
bypass valves. If either of them becomes clogged and
restricts oil flow, the valve(s) will open to allow oil to
bypass the return filter (or oil cooler) to allow oil to flow
to the hydraulic tank.
Hydraulic oil is used to lubricate the internal compo-
nents of pumps and motors. This oil is returned via the
case drain lines back to the hydraulic tank.
NOTICE
See “Mow Circuit—Theory of Operation” on page
10D-33 for the electrical operation of this circuit.
Содержание SLF 1880
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