Craftsman 247.287751 - Manual (Page 18)

HOW YOUR LOG SPLITTER OPERATES
Cylinder Rod
r"
Cylinder
Piiot
Pressure
Line
Pump
Reservoir
High Volume
Low Pressure
Gear Section
Low Voiume
High Pressure
Gear Section
THE PUMP
A two-stage log splitter pump has one large and one
small gear section, using common inlet and outlet ports.
Below a preset pressure (called unloading pressure)
a check valve between the two gear sections allows
both flows to combine. Together, the two gear sections
create a large volume flow which produces rapid
cylinder movement under low load conditions.
Above unloading pressure, a pilot pressure line(which
simulates actual pressure at the cylinder) activates the
unloading valve, which causes the flow to bypass the
large gear section and return to the pump inlet area.
The small gear section is now operating alone, and will
generate the higher pressure necessary for the actual
log splitting operation.
The original factory setting for the unloading valve is
designed to provide maximum flow while remaining
below engine stalling load. Note: Splitting capability
is not affected by the setting of the unioading valve.
Do not attempt to adjust or reset it without a
pressure gauge (should be performed by an
authorized SEARS Serve Center only).
THE DIRECTIONAL VALVE AND CYLINDER
From the pump, oil flows to a four way, three position
directional valve. At the neutral position this valve
directs the flow back to the oil reservoir, bypassing the
cylinder. When the directional valve is directing the flow
to the back of the cylinder, the cylinder rod extends
quickly until it meets significant resistance. Upon
reaching unloading pressure, movement of the shaft
will slow but will continue forward. If the pressure
reaches a preset maximum (called relief valve pressure)
the relief valve, located within the directional valve, will
allow the flow to bypass the cylinder and return to the
reservoir. This can happen when the cylinder rod meets
excessive resistance, or when it reaches the end of its
stroke and can move no farther.
Note: Never operate at relief valve pressure for more
than a few seconds.
When the directional valve is directing the flow to the
front of the cylinder, the rod will retract quickly since
it is encountering no resistance. The relief valve will
momentarily bypass the flow at the end of the return
stroke but the directional valve should then automatical­
ly return to the neutral position, directing the flow direct­
ly into the reservoir. This serves to protect the pump
from possible damage due to prolonged operation at
relief valve pressure.
Because of the potential for system damage, the relief
valve is carefully and precisely preset by the
manufacturer.
Note: The user should not attempt to adjust or
change the setting of the relief valve.
OPERATIONAL PROBLEMS
If you have trouble with your log splitter, please refer
to the Hydraulic Trouble Shooting Guide on page 19.
Note: Readjustment of valves or disassembly of
pump should be performed by your SEARS Service
Center only.
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