Hyundai HL955 Manual page 490

(1)
Control block
Proportional direction valve to the LUDV principle (Load pressure - Independent - Flow -
Distribution)
(2)
Actuator control
At the spool (2) the direction and volume of flow is determined that flows to the actuator
connections (A or B).
The spring chambers (8) are supplied with pilot pressure either via the pilot connections a and b
hydraulic control.
The value of the pilot pressure within the spring chamber (8) determines the stroke of the spool
(2).
The pressure compensator (3) controls the pressure differential at the spool (2) and therefore, the
flow to the actuators (A, B).
(3)
Loader pressure compensation (LUDV)
The control block works to the LUDV principle. In this load - sensing version the pressure
compensators (3) are located between the spool (2) and the actuator connections (A, B).
The highest load pressure of all of the actuators involved is applied to all of the pressure
compensators. In parallel it is also applied to the pump.
If the pump flow is insufficient for all of the functions, then all work movements are reduced in
speed by the same ratio.
(4)
Loading holding
Within each function axis a load holding valve (4) is fitted between the pressure compensator (3)
and the actuator connections.
(5)
Pressure safety, actuator connections
Large nominal size port relief valve (7) with combined anti-cavitation functions protect the
actuators from overloads and cavitation.
(6)
Float position
The float position is obtained by means of a 4-position spool.
(7)
Regeneration
To prevent cavitation, with negative loads (e. g. dump or lowering), the tank port is pre-loaded via
counter balance valve (5) and is fed with oil via the regeneration check valve (6) downstream of
the pressure compensator.
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