Hydraulics
9803/3280 Issue 1
6 - 9 6 - 9
Circuit Descriptions
Section E Section E
Loader Valve - A.R.V. Operation
Component Key:
1A Pump Inlet
3C Lift Ram Spool
3D Shovel Ram Spool
3F ARV - Head Side
3G ARV - Rod Side
31 Shovel Ram
32 Shovel Ram
Under normal operating conditions, with the shovel in the
'carry' position, the mechanical linkage keeps the shovel
level as the arms are raised, to prevent spillage of the load.
If, as illustrated, the shovel is fully tipped when the arms are
being raised, the shovel is unable to tip further, producing
back pressure in the head side of the shovel rams 31 and
32 and cavitation in the rod side.
As the arms continue to rise, the back pressure increases
until it reaches the setting of A.R.V. 3F. This A.R.V. then
opens, allowing the excess back pressure to be dumped to
exhaust and prevent the rams and linkage from being
damaged.
The rod side A.R.V. 3G senses a higher pressure in the
exhaust gallery than in the service port and therefore opens
to allow exhaust oil to overcome the cavitation.
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