jcb JS200 Service Manual page 332

Section E
55 - 5
Operation
In the Soft State
When lever is in neutral (Refer to Fig. 1).
a. The hot oil separated from the oil cooler line enters
the R port of the cushion valve.
b. It flows through the reverse notch spool interior and
through passages e and f.
Then, after flowing through passages e and f, it flows
through the outer periphery of the respective cushion
spools, returning to the hydraulic oil tank through the T
port of the cushion valve.
During Dipper Closing Operation
a. Pilot pressure enters the A port of the cushion
valve from the remote control valve. Because this
pilot pressure enters at the left end of the cushion
spool and left end of the reverse notch spool, the
respective spools move to the right.
b. The pilot pressure inside the cushion spool enters
the g cavity through the spool hole. It then passes
the reverse notch spool outer periphery and enters
the control valve from C port.
c. The return oil (pilot pressure) from the control valve
enters the f cavity after passing from the D port to
the outer periphery of the reverse notch spool. It
then passes through the cushion spool outer
periphery and returns to the hydraulic oil tank from
the T port.
d. At this point, the hot oil from R port flows through
the h passageway and enters the right end of the
cushion spool because the reverse notch spool is
switched to the right, so the e and f passageways
are closed. The hot oil passes through throttle c
and d and enters the remote control valve from B
port. (The hot oil warms the remote control valve).
9803/6400
Hydraulics
Cushion Valves
Section E
55 - 5
Issue 2*