9803/3280
Issue 1
8 - 5
8 - 5
Circuit Descriptions
Section E
Section E
Componet Key:
C
Lower Service Port
D
Upper Service Port
E
One Way Restrictor
X
Parallel Gallery
4A
Slew Spool
4B
Boom Spool
4H
ARV
4J
ARV
Slew Ram End Damping
As ram
A
nears the closed position, damping rod
B
seats in
cone
C
, where it is held by spring
D
. Tapered flutes on the
end of the rod produce a restricting orifice, thus restricting
the speed of the oil being exhausted from the ram. This
provides a cushioning effect between the piston and the
dump end of the ram, effectively damping out the shock
loads which would otherwise occur when the boom reaches
the end of its slewing arc.
Excavator Valve
- One Way Restrictor Operation
Because of its weight, the excavator end could take over
control when boom lower was selected. The falling boom
would tend to push oil out of the ram faster than the head
side was being filled. Consequently, when the excavator had
reached the ground, there would be a time lapse while the
ram filled with oil before the service would operate again.
To prevent this from happening, the boom service is fitted
with a one way restrictor. When the boom is being raised,
t he p op p et in rest ric t or
E
is held off it s seat b y t he
pressurised oil flow, therefore oil delivery to the boom ram
rod side is unrestricted.
When the boom is being lowered, the oil flow through the
one way restrictor
E
re-seats the poppet, therefore the flow
of oil is restricted through the small drilling in the base of the
poppet. This slows the boom down to a controllable speed.
Excavator Valve - Slew Operation
The illustration shows R.H. slew selected. The lower port
C
has been pressurised by the spool. Oil flows from the
parallel gallery
B
, out past A.R.V.
4H
to both the head side
of the L.H. slew ram and the rod side of the R.H. slew ram.
The boom therefore slews to the right hand side of the
machine. Displaced oil from the rod side of the L.H. slew
ram and from the head side of the R.H. slew ram flows back
through the upper service port
D
and back to tank.
A
Ram
B
Damping Rod
C
Cone Seat
D
Spring
w
A230420
A
D
B
C
