Komatsu Galeo PC800-8 Shop Manual page 273

10 Structure, function and maintenance standard
8. Boom shockless control function
This function improves safety by preventing
spillage of the load from the bucket and by
reducing the shock when the boom is stopped,
thereby reducing operator fatigue.
Actuation
Boom shockless
switch
ON
(Contacts open)
OFF
(Contacts closed)
• If the boom is raised, the pilot pressure from the PPC valve is generated in line A. When this happens, the
pressure in line A passes through check valve (2) and pushes the spool of the main valve in the direction of
the arrow. The pilot oil at the left end of the spool passes through line B and the PPC valve, and returns to
the tank. However, when this happens, check valve (4) is being pushed open by the pressure in line A, so it
also allows the oil to pass in the opposite direction. For this reason, the boom can be raised without any delay
in response.
• In this condition, if the boom RAISE operation is stopped, the spool of the main valve moves in the opposite
direction to the arrow and drains the oil from line A. However, the action of check valve (2) means that the
oil must pass through orifice (1). As a result, the spool returns slowly to the neutral position to prevent any
shock.
PC800, 850-8
Cancel solenoid Boom shockless
valve
De-energized
Energized
control
ON
Canceled Suitable for compacting or skeleton work
SEN00386-03
Remarks
Suitable for normal operations
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