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Section E
8 - 11
*
Excavator Valve - Manual Control
Hydraclamp Valve Operation
(Sideshift Machines)
When the backhoe is being used for excavating duties, the
kingpost assembly must be 'clamped' to the sideshift
rearframe.
The hydraclamp control valve assembly (items G, D and C) is
positioned in the inlet end of the excavator valve block and is
connected directly to the parallel gallery B. The valve
operates in conjunction with solenoid valve E housed in the
side of the excavator valve block.
1 - Clamps Pressurised
When the hydraclamp switch A is in the OFF position (not
pressed), the solenoid valve E is de-energised. The solenoid
valve in this de-energised state blocks the exhaust path from
the parallel gallery B to the drain port (tank).
When an excavator service is operated, pressure is
generated in parallel gallery B, this pressurised oil enters the
clamp valve C and lifts poppet D off its seat against the force
of spring G. The oil flows past the poppet and out to the
hydra-clamps 62.
9803/3280
Hydraulics
Circuit Descriptions
C
D
G
F
E
62
Purchased from www.WorkshopManuals.co.uk
2 - Clamps Released - Not Precision Control Machines
When the hydraclamp switch A is in the ON position
(pressed down), the solenoid valve E is energised. The
solenoid valve in this energised state now allows a
connection to be made from the parallel gallery B to the
drain port (tank) via gallery F.
Oil from the hydra-clamps is vented through the clamp valve
and gallery F to the drain port (tank).
Also, pressure resulting from the operation of an excavator
service passes by poppet D as before but the oil takes the
path of least resistance and is vented via gallery F to the
drain port (tank).
Restrictor H ensures that not all oil in gallery B is dumped
back to tank.
3 - Clamps Locked Up
If no service is being operated, pressure in the parallel gallery
falls to that of the neutral circuit and the force of spring G is
sufficient to keep the poppet seated.
Pressure is therefore trapped in the line to the clamps,
maintaining the excavator end in a securely clamped
condition.
H
A
B
S270680
Section E
8 - 11
DRAIN
CLAMP
PORT
PORT
E
A270690
Issue 2*
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