Hydraulics
9803/7130 Issue 1
5 - 6 5 - 6
Circuit Descriptions
Section E Section E
Loader Valve
Component Key:
A Spool Waist
C Spool Lands
D Spool Waist
E Upper Waist
X Parallel Gallery
1A Pump Inlet
3B Lift Ram Spool
3H Load Hold Check Valve
24 Lift Ram
25 Lift Ram
Arms Lower
When a spool is selected as shown at 3B, the central lands
of the spool C block the neutral circuit. Oil from the pump,
entering at 1A, is diverted into the parallel gallery X, flows
around the waisted section of the spool D, opens the load
hold check valves 3H and 3G (not illustrated), and out to the
rod side of lift rams 24 and 25.
The upper land of the selected spool E blocks the flow from
the parallel gallery to the head side port and oil returning
from the rams is diverted into the exhaust gallery.
Float
The float facility is provided to allow the arms to move up
and down so that the shovel can follow the surface contours
as the machine is driven over uneven ground.
This is achieved by moving the lift spool 3B up beyond
'arms lower' into the 'float' detent, when the feed from the
parallel gallery to the service ports is blocked and the neutral
circuit is re-opened. Both service ports are connected to
exhaust via the spool waists A.
Oil can then be displaced from either end of the lift rams 24
and 25 into the exhaust gallery, allowing the rams to open
and close as required.
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