Toro Greensmaster 3120 Service Manual page 68

Mow (machines with backlap)
Backlap
Hydraulic System: Hydraulic Flow Diagrams
With the engine running and the function control and joystick levers positioned so
the reels will not turn (refer to the traction unit Operator's Manual), solenoid relief
valve (S1R1) in the mower manifold is de-energized. The de-energized (S1R1)
by-passes flow from the front gear pump section to the hydraulic filter and tank.
Additionally, pilot operated relief valve (PRV) will remain seated to prevent the
reel motors (and reels) from rotating.
With the engine running and the function control and joystick levers positioned to
lower and engage the cutting units (refer to the traction unit Operator's Manual),
solenoid relief valve (S1R1) is energized to direct fluid flow toward the reel speed
control valve (FC1) and the reel motors; refer to
(S1R1) and also functions as the mow circuit relief valve, limiting circuit pressure
to 17,236 kPa (2500 psi). To provide precise reel speed control, flow moving
across the speed control valve (FC1) is pressure compensated by the logic
cartridge valve (LC). The logic cartridge valve maintains a pressure differential
of 517 kPa (75 psi) across the speed control valve. Any excess flow above the
speed control valve setting is by-passed to the tank through the logic cartridge
valve.
With the backlap valve (MR) in the mow position, fluid flows out the (MA) port of
the mower manifold and to the reel motors. The reel motors are connected in
series. Fluid flows through the left front reel motor, then the right front reel motor
and then the center reel motor to turn the reel motors in the mow direction. Mow
circuit pressure will cause the pilot piston under the pilot operated relief valve
(PRV) to shift and open the valve. The shifted relief valve allows fluid to exit the
reel motors and return to the tank through the mower manifold, hydraulic filter
and optional hydraulic fluid cooler (if equipped).
The backlap operation is the same as mowing operation, except for the position
of the backlap valve (MR). When the backlap valve (MR) is in the backlap
position, fluid flows through the backlap valve, out the (MB) port of the mower
manifold and to the reel motors that are connected in series. Fluid flows through
the center reel motor, right front motor and then left front motor as it turns the
reel motors in the backlap direction.
Page 4–22
Figure 23. Solenoid relief valve
Greensmaster 3120
17230SL Rev C