Anti-Drift Valve - Doosan DX140R Shop Manual

Anti-drift Valve

An anti-drift valve is installed in the cylinder port on the side of
the arm load (arm bottom) which prevents the unwanted self-
lowering of the arm (boom) cylinder.
In the neutral state (Figure 14), cylinder port pressure is guided
to the spring chamber (AD5) through path (AD2), poppet (AD3)
gap, and path (Ad4).
The poppet (AD1) is fully seated by the differential pressure
generated by the spring force and the area difference of the
poppet.
In arm damp (boom upward) operation (Figure 17), the oil
supplied from the pump pushes the poppet (AD1) open and
flows into the cylinder port.
Figure 17
In the arm crowd operation (boom upward), pc1 (pc2) is
pressurized to move the poppet (AD3) in order to induce the oil
in the spring chamber (AD5) to the drain path (DR) via the
poppet (AD3) gap and spool (AD6) gap; consequently, the
poppet (AD1) is opened and the lubricant oil in the cylinder port
flows to the tank path (Ta) via the spool.
Figure 18
SP001029
Main Control Valve
Page 19