GROVE 4-11
CD3340B/YB4411 HYDRAULIC SYSTEM
Published 04/07/2015 Control # 569-00
Description of Operation
Hydraulic System
The hydraulic system is a closed-center hydraulic system.
Which means that hydraulic oil is blocked from returning to
tank when the valves spools are in the neutral position. The
control valve sections used in the hydraulic system of the
main control valve are pressure compensated valve sections
incorporating a flow divider principle in their operation. This
provides the ability to control multifunction operation when
flow demand exceeds pump capacity though slowed down
proportionally. This means that all circuits will continue to
function regardless of differences in their load and
regardless of the pump flow. The flow relationships specified
between functions are maintained over the full range of the
pump.
Figure 4-2 illustrates the interrelationship of the load sense
shuttle (1), the compensator (2), the directional spool or
variable orifice (3), combined with the variable displacement
load sense pump (4).
After the spool is activated the work port load pressure is
transmitted to the bridge (5). The load sense shuttle (1), in
turn, transmits the highest work port pressure to the load
sense port of the pump (4) and all compensators (2) within
the valve assembly. Pump (4) responds to the load sense
signal with load sense pressure plus pump margin or
differential pressure. It is this margin or differential pressure
that overcomes the compensators (2) and permits flow to
bridge (5) and work port A (16) or B (17). This system
establishes a constant pressure differential across a variable
orifice spool (3). At full stroke of spool (3) the maximum
orifice can be determined, thus creating spool flow ranges
(i.e. 76, 114, 151 Lpm [20, 30, 40 gpm]) at a predetermined
pressure differential at spool (3). It is the working
combination of the components that sets up the flow dividing
principle.
Inlet Section
The inlet section (Figure 4-2) is connected to the pressure
side of the variable displacement load sense pump by a
hydraulic hose. There is a load sense relief valve installed in
the inlet section.
Working Valve Sections
There are four working sections (Figure 4-2) of the main
control valve that receive hydraulic oil from the variable
displacement load sense pump. These sections control the
hoist, telescope, lift and swing functions. They are closed-
center sections, blocking any return of oil back to tank until
the valve spool is actuated to operate a function. Flow is then
directed through the return core (14, Figure 4-2) to the outlet
port of the inlet/outlet section and then to tank.
FIGURE 4-1
Item Description
1 Housing
2Piston
3 Shoe
4 Port Plate
5 Drive Shaft
6Swash Plate
7 Shaft Seal
8 Compensator Control
9Valve Plate
a0727
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