jcb JS220 Service Manual

31 - 3
Section E
Hydraulics
9803/6400
Section E
31 - 3
Issue 2*
Control Valve JS200/JS240
Operation (continued)
Individual Operation
1. Travel Spool Switch (Refer to Fig. 1,3,4).
When the P
bl1 (Pal1) is pressurised and the 5-spool travel spool is selected (Fig. 4), the neutral passage A is closed and
downward flow is cut off, so the oil delivered from the PL port flows from the 5-spool neutral passage A past the sleeve (M) into
passage I to the spool neck, to the passage K (passage J) and flows to the cylinder port B
Li (ALi).
When the P
bR1 (Par1) port is pressurised and the 4-spool travel spool is selected to neutral, passage a is closed and downward
flow is cut off, so the oil delivered from the P
R port flows from the 4-spool neutral passage a to the sleeve K(N), passage f to the
spool neck, passage g (passage h) and flows to the cylinder port B
RI (ARI).
The return oil from the cylinder port flows through the spool neck and is released to the tank.
When one side of the 4-spool (5-spool) travel spool is selected (Fig. 3,4), the signal land (K) (L) is closed but the oil entering
from the signal port P
p flows through the restriction (I) (J) passage, land (K) (or restriction (I) (J) passage (f) (g) (h) then land (L)
and is connected with the tank passage so the signal passage (f) pressure does not rise and the travel linearity spool maintains
its indicated position due to spring force. (Fig.1)
When the above operations (4,5 spool simultaneous, or separate) are made, flow to the tank passage of the signal passage (b)
is cut off so the P
t port pressure rises.
Boom Spool Selection
2. Up (II speed confluence) (Refer to Fig. 1,3,5,8,).
When pilot port P
aR2 is pressurised and the boom I spool is selected, the 4-spool neutral passage a is closed and the oil
delivered from the P
R port flows from the 4-spool parallel passage b and pushes up the load check valve (O), flowing through
passage i spool neck and passage K and pushes open the lock valve poppet (P) and flows into A
R2 port.
When P
aR2 is pressurised (Fig. 1,8) part of the oil flows from the outer passage through the P2 port and flows to the shuttle (Q)
passage z x, and from the P
3 port flows through the outer passage again and pressurises P4 port and selects the boom II spool.
At this time, due to the spool being selected (Fig. 8) and the flow to the neutral passage A from passage D being cut off, the oil
delivered from P
L flows through passage B, pushes open load check valve (R) and flows through passage C H L1 (Fig. 3) L2
(Fig. 5), converging with passage K from 4-spool passage m.
The return oil from cylinder port B
R2 flows though passage j and through boom I spool neck and is released to the tank
passage. (Fig. 5)
3. Lower (Refer to Fig. 6, 14).
When the pilot port P
bR2 is pressurised and the boom I spool is selected (Fig. 6), the 4-spool neutral passage a is cut off and
the oil delivered from the P
R port flows through the 4-spool parallel passage b, pushes open the load check valve (O) and flows
through passage i j from cylinder port B
R2.
The return oil from cylinder port A
R2 flows through the lock valve poppet (P) and, through passage K, flows to the spool neck
and is released to the tank passage.
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jcb JS220 Specifications

General

Brand	jcb
Model	JS220
Category	Excavators
Language	English