Toro 10178SL Service Manual Groundsmaster 4300 D Preface Publication

Lift Circuit: Lower Cutting Decks
A four section gear pump is coupled to the piston (trac-
tion) pump. Gear pump section (P4) supplies hydraulic
flowtotheliftcontrolmanifoldandliftcylinders.Thegear
pump takes its suction from the hydraulic reservoir.
Counterbalance
Once the cutting decks are fully lowered, the lift control
manifold proportional relief valve (PRV) maintains back
pressure (counterbalance)  on  the deck  lift cylinders.
This  counterbalance pressure  transfers  cutting deck
weight to the machine to improve traction. A set of wires
locatedbehindthecontrolarmaccesscoverallowcoun-
terbalance pressure to be adjusted to one of three set-
tings.
The lift control  manifold includes three  (3) electrically
operated valves. Solenoid valve (S1) is used to direct oil
flowtoextendtheliftcylinders   whenenergized  orretract
them when de--energized. Solenoid  valve (S2) allows
hydraulic flow from the rod end of the lift cylinders when
energized and prevents oil passage from  the lift cylin-
ders  when   de--energized.  Proportional  relief   valve
(PRV) is used to control  the operation of the manifold
logic cartridge (LC)andalsoacts  asacircuit reliefvalve.
Apressuretransducer  locatedintheforwardtractionhy-
draulictubeisusedbythecontrollerasaninputtodeter-
mine  traction circuit  pressure.  Based  on transducer
input and machine counterbalance setting, an electrical
output from the controller is provided  to the lift control
manifold proportional relief valve (PRV) to vary counter-
balance pressure. As traction pressure increases (e.g.
climbing a  hill) the  counterbalance  pressure also  in-
creases to increase the weight on the tires and improve
traction.
While operating the  machine during conditions  of not
raising or lowering the cutting decks (joystick in the neu-
tral (center)  position) (Fig. 19),  all of  the lift manifold
valves (S1, S2 and PRV)arede--energized.Thede--en-
ergized relief valve (PRV) allows hydraulic flow to return
to tank through the manifold. This flow causes a pres-
sure differential that shifts the logic cartridge (LC) which
allows pump flow to bypass  the lift cylinders. Flow re-
turns to the oil filter and then to the hydraulic reservoir.
LIFT CIRCUIT: NOT RAISING OR LOWERING
NOTE:  When the mow speed limiter is in the transport
position, the cutting decks will not lower.
Lower Cutting Decks (Fig. 18)
When the joystick  is moved to the  lower position, the
controller energizes all of the lift manifold valves (S1, S2
and PRV). The  energized relief valve (PRV) prevents
flow through the valve which returns logic cartridge LC
to the unshifted position. With lift manifold cartridges in
this position, pump flow is directed to the barrel end of
allliftcylinders  toextend thecylinders andlower thecut-
ting decks. Fixed orifices in the lift control manifold (C2,
C4, C6 and C8) control the lowering speed of the cutting
decks by providing a restriction for the return flow from
the lift cylinders.
While the cutting decks are being lowered, the propor-
tional relief valve (PRV) has a secondary function as a
circuit relief to limit lift circuit pressure to 2000 PSI (138
bar). Lift circuit pressure can be monitored at lift control
manifold port G4.
S1, S2 AND PRV
DE--ENERGIZED
LC SHIFTED
When the  joystick is  returned to  the neutral  (center)
position, all of the lift manifold valves (S1, S2 and PRV)
are de--energized. The de--energized relief valve (PRV)
allows hydraulic flow to return to tank through the man-
ifold. This flow causes a pressure differential that shifts
the logic cartridge (LC) which allows pump  flow to by-
pass the lift cylinders. All lift cylinders and cutting decks
are held in position by de--energized valve S2.
LIFT
CONTROL
MANIFOLD
FROM
PUMP P4
TO OIL
FILTER
Figure 19
Groundsmaster 4300--D
Page 4 -- 19
Hydraulic System
Product Specification
CategoriesLawn Mower Manual, Sprinkler and Irrigation Manuals, Toro Sprinkler and Irrigation Manuals
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- 255 pages
Document TypeCatalog
LanguageEnglish
Product BrandToro. Customer Service Representatives are available by phone: Monday - Friday 7:30 a.m. to 9:00 p.m. (CDT) - Saturday 8:00 a.m. to 8:00 p.m. (CDT) - Sunday 10:00 a.m. to 8:00 p.m. (CDT)
Canada 1-888-225-4886 USA 1-888-384-9939, Lawn Mower
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Publishertoro.com
Wikipedia's PageToro Company
CopyrightAttribution Non-commercial
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