Hydraulics
9803/7130 Issue 1
7 - 5 7 - 5
Circuit Descriptions
Section E Section E
Componet Key:
C Lower Service Port
D Upper Service Port
E Bi-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 - Bi-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 bi-restrictor E.
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 X, out past A.R.V. 4J 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
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