Terex TS14G, Maintenance Manual

Page: 244 / 376

Section 235-0060
Bowl Hydraulic System - Bowl Control Valve
SM 1887 1-00
2
cylinders which raises the apron. Oil forced out of the
apron cylinder rod ends flows into the control valve
housing and back into the tank. The purpose of the
load check valves inside the apron spool is to
prevent the apron cylinders from moving when the
apron spool is shifted from neutral to raise.
Power Down Bowl - Raise
When signal pressure is applied to the end of the
bowl spool, it shifts into the raise position. Oil flows
out of the housing bowl port and enters the bowl
cylinder base end ports. This extends the bowl
cylinders which raises the bowl. Oil forced out of the
bowl cylinder rod ends flows into the control valve
housing and back into the tank. The purpose of the
load check valves inside the bowl spool is to prevent
the bowl cylinders from moving when the bowl spool
is shifted from neutral to raise.
Ejector - Lower
When signal oil pressure is applied to the end of the
spool, the spool shifts. This action aligns ports in the
spool with ports in the valve so that oil can return
through the same port that it left and then unseat the
check valve and return through an outer channel in
the valve and back to tank. Main oil pressure is still
allowed to flow through the centre of the valve since
the spool does not totally block its flow.
Power Apron - Lower
When signal oil pressure is applied to the opposite
end of the apron spool, it is shifted in the opposite
direction into the lower position. Oil flows out the
opposite housing port and flows into the apron
cylinder rod ends. This retracts the apron cylinders
which lowers the apron. Oil from the cylinder base
ends returns to the valve housing return port and
back into the tank.
Power Down Bowl - Lower
When signal oil pressure is applied to the opposite
end of the bowl spool, it is shifted in the opposite
direction into the lower position. Oil flows out the
opposite housing port and flows into the bowl cylinder
rod ends. This retracts the bowl cylinders which
lowers the bowl and cutting edge into the ground. Oil
from the cylinder base ends returns to the valve
housing return port and back into the tank.
relief valve (5), three check valve assemblies
(18 to 28) and valve housing (3).
The main pressure relief valve permits bypassing
hydraulic oil back to the tank, should oil pressure
exceed 127.5 bar (1 850 lbf/in
2 ). Check valves in the
spools prevent return oil flow from cylinders until
supply oil pressure at the spools is sufficient to move
the loads. Thus they prevent unexpected movement
(dropping) of a load until oil pressure is sufficient to
hold or raise it.
Note:
The bowl spool in the control valve used with a
power down bowl is a double acting type and contains
two load check valves and springs. The apron spool
in the control valve used with a power apron is a
double acting type and contains two load check
valves and springs. The ejector spool is a single
acting type containing one check valve and spring.
OPERATION
Neutral
With no signal oil pressure applied, the spools are
held in their neutral positions by centering springs at
either end. Oil supply through the inlet port flows
through the central passage around spool grooves to
the outlet port, and through the oil return hose to
tank. Since valve oil ports connected to the cylinder
supply hoses are blocked by the spools, no oil can
flow to or from the cylinders. The cylinders are
therefore held in their position by oil trapped on their
pistons.
Ejector - Raise
When signal oil pressure is applied to the end of the
spool, the spool shifts. This action aligns the spool
lands to block the supply oil flow from the valve inlet
channel to the outlet port.
Supply is now directed through the spool holes and
bore to unseat the spool check valve and then flow to
the cylinder forcing it to extend.
Power Apron - Raise
When signal pressure is applied to the end of the
apron spool, it shifts into the raise position. Oil flows
out of the housing apron port and enters the apron
cylinder base end ports. This extends the apron
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