wsm L3130, Workshop Manual

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8-M12
L3130 · L3430 · L3830 · L4630 · L5030, WSM HYDRAULIC SYSTEM
■
Lifting to Neutral (Acting the shockless
mechanism)
In returning from Lifting to Neutral, the spool (1) is
pushed back to the arrow-mark direction. When the
Neutral position comes near, the groove part D of the
spool (1) makes the pressure difference at the P port and
C
1
port. Therefore, the check valve in the rear hydraulic
block gradually closes, and absorbs any shock at lifting
stop. In that case, since oil is remained in the chamber
A of the unload poppet 1 (2) and closes. However, the
unload poppet 2 (3) opens because of low pressure in
chamber B, and then the oil from the pump returns to the
transmission case through T
3
port until unload poppet 1
(2) opens.
W1014273
■
Lowering
When the control lever is moved to “DOWN” position,
spool (2) moves to arrow-mark direction, and pushes the
poppet 2 (1). It forms a circuit with the C
2
port and T
2
port.
The oil in the hydraulic cylinder is forced out by the
weight of the implement, and returns to the tank through
the C
2
port and T
2
port, lowering the implement.
The pressurized oil at the P port pushes open unload
poppet 1 (3) and returns to tank from T
1
port.
■
Floating
When the control lever is moved all the way to the
bottom, spool (2) and poppet 2 (1) remain in the position
described for “Lowering”. The oil flows freely between
the hydraulic pump, hydraulic cylinder and tank.
W1014640
(1) Spool
(2) Unload Poppet 1
(3) Unload Poppet 2
A : Chamber A
B : Chamber B
D : Groove P : Pump Port
C
1
: Cylinder Port 1
T
3
: Tank Port 3
(1) Poppet 2
(2) Spool
(3) Unload Poppet 1
A : Chamber A
P : Pump Port
C
2
: Cylinder Port 2
T
1
: Tank Port 1
T
2
: Tank Port 2
T
4
: Tank Port 4
KiSC issued 02, 2007 A