31 - 15
Operation (cont’d)
Combination Operation
2. Anti-drift valve - Boom, Arm Section
(Refer to Fig. 12, 13 and 14)
The anti-drift valve is installed on the cylinder port of the arm
to prevent the boom or arm rams from naturally sinking.
Under neutral status, the cylinder port pressure is
transmitted to the spool head 13 (23) through the passage
16 (23), the spring chamber 14 (24) and the passage 15 (22).
The poppet 12 (22) is seated properly by spring force and
the force formed by the poppet area difference.
During boom raising or arm dump (Fig.14), the oil supplied
by the pump pushes the poppet 12 (22) and flows out from
the cylinder port.
During boom lowering or arm crowd (Fig.15), port PLc1
(PLc2) is pressurised, the spool is selected and the oil in the
spring chamber 14 (24) is guided to the drain port Dr1 (Dr2).
From the passage 15 (22), the flow opens the poppet 12 (22)
and the return oil from the cylinder port passes through the
boom1 (arm1) spool and flows to the tank passage.
Section E Hydraulics
9803/6020
Section E
31 - 15
Issue 1
Control Valve
Fig. 13
289860
Neutral State
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