The compact blades function…
Two of the
tailgate-
mounted valve’s
working sections controls the two
compaction blades The blade that pivots (rotates) is
called the
sweep blade
The blade that slides in the track
channels is the
slide blade
If the tailgate-mounted valve
has more than two working sections (the sections with
moveable “spools”), the extra work sections are for the
“optional equipment” Work sections for the “options”
are always “in front” (upstream; closest to the pump) of
the blades work sections
The sweep blade’s work section is always upstream of
the slider blade’s work section These two blade sections
have a casted flow path known as
tandem center
A V40
“tandem center” work section has the “power core”
internally blocked
downstream
…this means that the
shifted spool
closest to the pump
(the upstream sweep
section) will consume
all
of the available pump flow with
any downstream spools that are also shifted (the slider
spool) getting no flow
until
the upstream section (the
sweep)
shifts back to neutral
This creates a simple function “sequencing” effect Since
the correct operator’s method of cycling the blades is to
shift and release
both
spools’ hand levers
simultaneously, the sweep blade rotates (sweeps)
first
while the slide blade sits motionless waiting for the
sweep’s spool to knock-out to neutral At the very
moment the sweep’s spool automatically shifts to
neutral, all of the pump’s flow is then directed to the
slider blade’s cylinders and the slider blade begins to
move
As mentioned earlier, both the sweep and the slider
work sections have knock-out positioners These
knockouts, when teamed with the plumbing scheme and
the “tandem” center section castings, provide for the
sequencing of the semi-automatic cycling of the
compaction blades The blades must
both
sequence in
their specific order and they must move distinct and
separate of each other to be functioning normally
The knockout positioner is the device that holds the
blade spools shifted until the hydraulic pressure in that
particular section
rises
to the knockouts
pressure
setting
When this setting is reached, the spool is
released and it shifts to neutral (spool centered)
position The pressure setting specification for the
EXCEL is…sweep knockout spec is 2200 PSI @ throttle
advanced and the slider knockout spec is 2700 PSI @
throttle advanced The pressure
rise
typically occurs
when each pair of cylinders bottom-out at the end of
their stroke
Having said all of this, the compact blades do a semi-
automatic compaction cycle as follows…The cycle begins
with both spools (via hand levers linkage controls)
manually simultaneously shifted outward and released
Both knockout positioners grab and hold the spools
shifted The
sweep
cylinders begin to move first with all
of the pump’s flow going to the sweep cylinders (The
sweep’s valve section is closest to the pump and its
internal casted passages are “tandem-center”, which
means all of the pump oil goes to its own workport and
nothing goes downstream ) The sweep blade continues
to rotate until its cylinders complete their stroke and
they bottom-out This bottoming-out causes a rapid rise
in sweep pressure and the sweep knockout will knockout
the sweep spool to
neutral
centered
Meanwhile, the
slider spool has been held shifted with no pump flow
available to it At the very moment the sweep spool
knocks-out to neutral, all the pump flow is
now
available
to the slider spool which begins directing the flow to the
slider cylinders The slider blade
now
begins to move
and it continues to move until its cylinders bottom-out
and the pressure rises to its setting The slider knockout
then knocks the spool to centered neutral and the first
half
of the semi-automatic blade
cycle
is complete
Both
spools are now at their centered neutral position The
blades are said to be stopped at their cycle
interrupted
position This is correct and normal functioning
The second half of the semi-automatic cycle begins
(after the operator visually assures it is safe to do so)
with both hand control levers being pushed inward
simultaneously The sweep blade again moves first (its
valve section is still upstream of slider, of course) and
the second half of the cycle occurs the same way but in
the opposite direction of the first half
The second ry port relief system…
As mentioned
earlier, the sweep work section has a port relief on the
sweep cylinders extend-side (cylinder’s base-end) and
an anti-cavitation check opposite of it (on the retract-
side; the rod-side) Acting together, these two port
mounted cartridges are a
system
that can relieve the
portion of the structural loads that are above allowable
amounts (This would be seen as a slight
unwrapping
of
the sweep blade when the slider blade is nearly all the
way up) In some applications this situation will rarely
occur and in others it may sometimes occur when the
EXCEL body is near its full capacity
The EXCEL sweep’s secondary port relief is set to 3800
PSI @ “crack” (Crack being 2 GPM)
When the slider blade is travelling upward (“compacting”
the garbage), the sweep blade has already been fully
rotated down to “capture” the hopper’s garbage and the
sweep worksection will be in its centered neutral
position The compacting action of the slider blade
travelling upward will necessarily
induce
a hydraulic
pressure on the sweep cylinders base-side The
only
relief located to relieve the excessive
portion
of this
induced load is the relief on the cylinder
ports
side…the
secondary port relief (This is because the sweep spool
is in its centered neutral position and the spool itself
[Sec01-pg04]
