Hitachi ZW180 Technical Manual page 124

Combined Operation Circuit
•
Lift Arm Raise/Bucket Dump
•
When the bucket is dumped with the lift arm
raised, pilot pressure shifts the lift arm and bucket
spools.
•
Although pressure from the own pump is applied
to port LS1 of the priority valve, port LS2 is not
pressurized as it is connected to the hydraulic oil
tank.
•
As pressure at port LS1 is larger than the spring
force of the priority valve, the spool moves
rightward.
•
Therefore, pressure oil from the main pump flows
to the lift arm cylinder through the check valve
and the lift arm spool in the control valve, and
raises the lift arm.
•
Pressure oil from the main pump also flows to the
buket cylinder through the check valve, orifice and
bucket spool in the control valve, and dumps the
bucket.
•
Although lift arm raising operation is more heavy
loaded than the bucket dumping operation,
pressure oil through the bucket operation circuit
flows to the bucket cylinder after passing the
check valve and orifice. Therefore, both the lift
arm cylinder and the buket cylinder move
smoothly.
SYSTEM / Hydraulic System
T2-3-8