jcb JS 200 Series, Service Manual

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31 - 4
Section E
Hydraulics
9803/6400
Section E
31 - 4
Issue 2*
Control Valve JS200/JS240
Operation (continued)
Dipper Spool Selection
1. Dump (Refer to Fig. 9).
When the pilot port P
aL4
is pressurised and the arm I spool is selected, the oil delivered from P
L
port through the 5-spool neutral
passage A pushes up the sleeve (S) load check valve (T) and, through passage U, passes through the spool neck and passage
V, pushing open the load sensing valve poppet (U) and flowing from the cylinder port A
L4
.
Also, part of the oil delivered by P
L
flows from 5-spool parallel passage B to the restriction (V), pushes open the load check
valve (W) and converges in passage U.
The return oil from cylinder port B
L4
flows through the spool neck from passage X and is released to the tank passage.
2. Crowd (Refer to Fig. 10, 15, 16).
When the pilot port P
bl4
is pressurised and dipper I spool is selected (Fig. 10), the oil delivered from P
L
through the 5-spool
neutral passage A pushes up the sleeve (S) load check valve (T) and from passage U flows through spool neck and passage X
and flows from the cylinder port B
L4
. Also, part of the oil delivered from P
L
flows through the restriction from the 5-spool parallel
passage b, pushes open the load check valve (W) and converges in passage U .
The return oil from cylinder port A
L4
pushes open the load sensing valve poppet (U), flows through passage V and is released to
the tank passage, but at this time, part of the oil flows through the spool hole ( X ), pushes open the regenerative circuit poppet
(Y) inside the spool, flows through the restriction (Z) and converges in the passage U (Fig. 15,16).
3. II Speed Confluence
When the dipper I spool is selected (Dump, Crowd: Fig. 9, 10), when the pilot port P
bR4
is pressurised and dipper II spool is
switched, the oil delivered from P
R
port flows through 4-spool neutral passage a and pushes open load check valve (z) and
converges into passage U from passage t or Z and at the same time pushes open the check valve (y) poppet (x) (Fig. 3). It
flows through the outer passage from the P6 port, through passage v from A
R4
port and flows through the spool restriction (w)
and converges in passage u.
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