Hydraulics
9803/3280 Issue 1
6 - 5 6 - 5
Circuit Descriptions
Section E Section E
Loader Valve - Load Hold Check Valves
Component Key:
1A Pump Inlet
B Parallel Gallery
D Service Line
3C Lift Ram Spool
3J Load Hold Check Valve
33 Lift Ram
34 Lift Ram
Operation 1
The illustration shows 'arms raise' being selected by the lift
ram spool 3C.
The weight of the loaded shovel, as indicated by the arrows,
produces a higher pressure in service line D than in the
parallel gallery B.
This pressure differential causes load hold check valve 3J to
close, thus preventing the load from dropping.
Operation 2
As the neutral circuit has been blocked by the central land of
the selected spool 3C, the pressure in parallel gallery B
increases until it is greater than that in service line D.
At this point, load hold check valve 3J opens, allowing oil to
flow from the parallel gallery into the service line and operate
the lift rams 33 and 34.
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