Cutting Unit Circuit - Toro Groundsmaster 3500 30807 Service Manual

Cutting Unit Circuit

Mow
The gear pump (P1) is directly coupled to the the hydros-
tat which is driven by the engine. Taking its suction di-
rectly from the hydraulic tank, the gear pump (P1)
supplies fluid flow to the manifold block and to the cutting
unit motors.
Solenoid valve (S or S1) is de−energized with the engine
running when either the PTO switch is in DISENGAGE,
or the transport/mow slide is in TRANSPORT. When
solenoid valve (S or S1) is de−energized, flow by−
passes the cutting deck motors through the solenoid
valve (S or S1) and moves on to the fluid cooler, filter,
and gear pump inlet.
Solenoid valve (S or S1) is energized with the engine
running when the PTO switch is in ENGAGE, and the
transport/mow slide is in MOW. When energized, sole-
noid valve (S or S1) allows flow out manifold block port
M1 to the cutting unit motors.
Fluid flows through the left, right, and then rear cutting
unit motors before returning to the manifold block port
(M2). When solenoid valve (S or S1) is energized, fluid
pressure shifts return circuit components in the hydraul-
ic manifold as follows:
Units Prior to Serial No 314000001: When solen-
oid valve (S1) is energized, fluid pressure shifts
blade relief valve (BV) which allows flow returning
from the deck motors to pass through the manifold.
Returning fluid continues on to the fluid cooler, filter,
and gear pump inlet.
Unit Serial No. 314000001 & Up: When solenoid
valve (S) is energized, fluid pressure shifts relief
valve (RV) which allows a small amount of hydraulic
flow returning from the deck motors past the relief
valve. This returning flow is restricted by the orifice
in the logic cartridge (LC2) creating a pressure im-
balance that shifts the logic cartridge to allow oil flow
from the deck motors to pass through the manifold.
Returning fluid continues on to the fluid cooler, filter,
and gear pump inlet.
If cutting unit circuit pressure exceeds relief pressure of
3200 PSI (221 bar) during deck motor operation, sole-
noid valve (S or S1) shifts to allow circuit pressure relief.
Hydraulic System
Cutting Unit Blade Braking (Units Prior to Serial No.
314000001)
When the solenoid valve (S1) is de−energized, the
blade relief cartridge (BV) shifts to its closed position,
blocking return flow from the deck motors and slowing
the cutting blades. The inertia of the rotating cutting
blades, however, effectively turns the deck motors into
pumps causing an increase in pressure as the flow from
the motors comes up against the closed blade relief car-
tridge (BV). When this pressure builds to 1500 PSI (103
bar), blade relief cartridge (BV) opens which allows hy-
draulic flow to return to tank and reduces return pres-
sure. When return pressure drops below 1500 PSI (103
bar), blade relief cartridge (BV) reseats to further slow
the cutting blades. This action repeats several times in
a very short period as the blades finally come to a stop.
Once the blades have stopped, blade relief cartridge
(BV) remains closed to keep the deck motors from rota-
ting.
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