Toro Groundsmaster 5900 Series Service Manual page 130

PTO Circuit Relief
Hydraulic System: Hydraulic Flow Diagrams
1.5 CID
PTO SWITCH OFF
PRV ENERGIZED
LC1 SHIFTED
g287730
Maximum mow circuit pressure is limited for each deck by the proportional
relief valve (PRV) in the hydraulic control manifold. The front and left deck
relief valves are set at 207 bar (3000 PSI) and the right deck relief valve is set
at 138 bar (2000 PSI).
Proportional relief valve (PRV) and logic cartridge (LC1) work together as a
circuit relief. When increased circuit resistance is met or if a cutting blade should
strike an object, the pressure increase is felt at the relief valve (PRV). If the
pressure should exceed the relief valve (PRV) setting, the relief valve (PRV)
will open, creating a small amount of hydraulic flow to return to tank through a
manifold sensing line. This flow causes a pressure increase that shifts logic
cartridge (LC1) and diverts circuit flow away from the deck motor to manifold
port P2 (Figure 43). When circuit pressure lowers, relief valve (PRV) closes
which returns logic cartridge LC1 back to its neutral position allowing circuit flow
to return to the deck motor.
M1
OR2 .025"
SQ
RV
110 PSI
PRV
10 PSI 600 PSI
M2
LC2
OR1
.063"
LEFT DECK
Figure 43
Page 5–30
G1
P1
PUMP
FLOW
10 PSI LC1
3000 PSI
P2
CD
RETURN
Groundsmaster ®
16227SL Rev B
5900 & 5910