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How your log splitter operates, The pump, The directional valve and cylinder – MTD 243-638-000 User Manual

Page 15: Dperational problems

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HOW YOUR LOG SPLITTER OPERATES

Cylinder

^ Cylinder

Directional

Valve

Relief Valve

Breather

Cap Unloading

Valve '

Pilot

Pressure

Line

Pump

Reservoir

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 pres­
sure) 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) acti­
vates 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 neces­
sary 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 capabiiity
is not affected by the setting of the unloading
vaive. Do not attempt to adjust or reset it without
a pressure gauge (shouid be performed by an
authorized service deaier oniy).

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

Low Volume

High Volume

High Pressure

Low Pressure

Gear Section

Gear Section

shaft will slow but will continue forward. If the pres­
sure reaches a preset maximum (called relief valve
pressure) the relief valve, located within the direction­
al 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 automati­
cally return to the neutral position, directing the flow
directly into the reservoir. This serves to protect the
pump from possible damage due to prolonged opera­
tion at relief valve pressure.

Because of the potential for system damage, the relief

valve is carefully and precisely preset by the manu­
facturer.

NOTE: The user should not attempt to adjust or
change the setting of the relief valve.

DPERATIONAL PROBLEMS

If you have trouble with your log splitter, please refer

to the Hydraulic Trouble Shooting Guide.

NOTE: Readjustment of valves or disassembly of
pump should be performed by an authorized ser­

vice dealer only.

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