
Reference
Only
INTRODUCTION
18000 SERIVCE/MAINTENANCE MANUAL
1-62
Published 12-05-17, Control # 035-23
Luffing Jib Lower
When luffing jib control handle is moved forward for luffing
down
, an input voltage of 2.6 volts or more is sent to node-1
controller. Node-5 controller sends a variable zero to 24 volt
output that is divided by a resistor and applied to luffing pump
EDC. Node-8 controller sends a variable zero to 24 volt
output that is divided by a resistor and applied to motor PCP.
Pump EDC tilts swashplate in the
up
direction to satisfy
pressure memory. Node-1 controller compares luffing
holding pressure to value in pressure memory. When system
pressure is high enough, node-8 controller sends a 24 volt
output to luffing jib brake solenoid valve HS-15. The brake
solenoid shifts to block drain port and opens port to low-
pressure side of luffing jib system to release luffing jib drum
brake.
When brake is released, pump EDC continues to tilt
swashplate to stroke pump in the down direction. In the down
direction, hydraulic fluid flow is from port A of pump to port B
of motor. Return fluid is from port A of motor to port B of
pump.
Node-5 controller output voltage to pump EDC and node-8
controller output voltage to motor PCP is relative to control
handle movement. As luffing jib control handle is pushed
forward, pump swashplate angle is increased. When system
pressure exceeds the PCOR (Pressure Compensating Over-
Ride) valve setting of 4,930 psi (340 bar), the valve shifts to
direct flow from shuttle valve into maximum displacement
side of servo cylinder. The PCOR valve over-rides the
c om m an d f r o m s e r v o P C v a l v e, i nc r ea s i ng m o t or
displacement and output torque and reducing output speed.
When PCOR valve closes, control of the motor returns to
servo PC valve.
Node controllers are continuously balancing the system
pressure and the motor displacement angle so the motor
displacement goes to minimum when control handle is all the
way forward, if the motor torque requirement is not too high.
Node-8 controller monitors motor displacement and controls
motor speed by regulating the hydraulic fluid flow through the
pump.
The weight of luffing jib attempts to drive motor faster than
return fluid can return to low-pressure side of pump. System
charge pump maintains fluid supply at a positive pressure to
motor. Pump swashplate position restricts the returning fluid
flow. Pressure builds on fluid return side of closed-loop,
acting as a hydraulic brake to control lowering speed.
When luffing jib control handle is moved to neutral position,
node-1 controller compensates for hydraulic system leakage
or changing engine speed. Node-5 controller sends a zero
output voltage to luffing jib pump EDC that moves
swashplate to center position. This shifts the motor back to
maximum displacement for slower output speed to slow the
drum rotation. Node-1 controller stores the load holding
pressure in pressure memory. After control handle center
switch opens, Node-8 controller sends a zero output to
disable luffing jib brake solenoid valve HS-15 to apply brake
before luffing jib pump de-strokes.
PRESSURE
SENDER
X
A
B
SUCTION
MANIFOLD
DOWN
UP
340 PSI
(23 BAR)
B
A
LUFFING JIB
(DRUM 6) PUMP
MAKE-UP CHARGE PRESSURE
DRUM
BRAKE
PM
ELECTRIC
DRUM
PAWL
LUFFING JIB
DRUM 6
.060
SERVO PILOT PRESSURE
FROM RIGHT TRAVEL
CHARGE PUMP
HS-15
4 GPM
(15 m/l)
OPENS AT
200 PSI (14 bar)
FIGURE 1-38
18CSM1-137
Содержание 18000
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