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
.
