Hydraulics
9803/7130 Issue 1
5 - 3 5 - 3
Circuit Descriptions
Section E Section E
Loader Valve - Load Hold Check Valves
Component Key:
X Parallel Gallery
Y Service Line
1A Pump Inlet
3B Lift Ram Spool
3H Load Hold Check Valve
24 Lift Ram
25 Lift Ram
Operation 1
The illustration shows 'arms raise' being selected by the lift
ram spool 3B.
The weight of the loaded shovel, as indicated by the arrows,
produces a higher pressure in service line Y than in the
parallel gallery X.
This pressure differential causes load hold check valve 3H to
close, thus preventing the load from dropping.
Operation 2
As the neutral circuit has been blocked by the central lands
of the selected spool 3B, the pressure in parallel gallery X
increases until it is greater than that in service line Y.
At this point, load hold check valve 3H opens, allowing oil to
flow from the parallel gallery into the service line and operate
the lift rams 24 and 25.
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