Toro Groundsmaster 4300-D Service Manual page 85

Mow Circuit Cutting Deck Blade Braking (continued)
Groundsmaster ® 4300-D
16226SL Rev C
g186192
When the operator turns the PTO switch O
control manifold proportional relief valves (PRV1 and PRV2) are de-energized.
The valves will shift to direct fluid away from the deck motors and toward the oil
cooler and filter. Hydraulic pressure is reduced to the cutting deck motors which
slows the cutting blades and also allows the deck control manifold relief valves
(RV1 and RV2) to shift. The shifted relief valves removes the flow path from the
orifice before the logic cartridge, causing the logic cartridge to shift and block
the return oil path from the deck motors
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 logic cartridges (LC1 and LC2). When this pressure
builds to approximately 10,340 kPa (1,500 psi), the relief valves open which
allows a small amount of hydraulic flow past the relief valve
flow causes a pressure increase that shifts the logic cartridge to once again allow
fluid flow from the deck motors
10,340 kPa (1,500 psi), the relief valve re-seats and causes the logic cartridge to
close again, blocking return flow from the deck motors to further slow the cutting
blades. This action of the relief valve opening and the logic cartridge shifting
occurs several times in a very short period as the blades finally come to a stop.
Once the blades have stopped, the logic cartridge remains in the closed position
to keep the deck motors from rotating.
Figure 34
(or if the decks are raised), the deck
FF
(Figure
(Figure 34). When return pressure drops below
Page 4–23 Hydraulic System: Hydraulic Flow Diagrams
32).
(Figure 33). This