2-29
BOOM SWING OPERATION
9)
Boom left swing operation
T1
P3
Boom swing
P3
To cylinder rod
side via B2 port
To A2 port via
Cylinder head side
Spool changeover
direction
B2
A2
Swing
Dozer
To bridge passage
in boom swing comp.
Supply
(connecting)
Pb2
R35Z72MCV24
Boom left swing operation
When the boom left swing operation is carried out, the secondary pressure from the remote control
valve is applied to Pb2 port to change over the boom swing spool.
Since the P3 side bypass passage is shut off at the boom swing section after the boom swing spool
changeover, the oil flowed from P3 port through the P3 side parallel passage flows into B2 port
through the load check valve in the boom swing section and the bridge passage since B2 port and
the bridge passage have been opened after the spool changeover and then into the rod side of the
boom swing cylinder.
On the other hand, the oil returned from the head side of the boom swing cylinder flows into A2 port
to the tank passage that has opened with the spool's notch after the spool changeover.
Then, the boom swing cylinder retracts to swing the attachment left.
