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MAINTENANCE
INTERSTATER 02/11 Maintenance Section 5-23
© 2011 Alamo Group Inc.
MAINTENANCE
Hydraulic Gear Pump
The gear pump, mounted to the pump mount and
driven by the crank shaft pulley, produces oil flow
for the control circuit. The gear pump inlet is
connected, via a hose, to the reservoir which
supplies control circuit oil. A high pressure hose
connects the pump outlet to the sectional control
valve inlet.
NOTE: The gear pump is not used when tractor
hydraulics are used to power the control circuit.
Sectional Control Valve
The control valve directs oil flow from the gear
pump to the hydraulic cylinders. In the "HOLD"
position, the spool blocks oil flow to the cylinders
which prevents movement, and directs oil through
the valve back to the reservoir.
When the spool is shifted, oil flows to one side of
the cylinder while the other side is opened to the
return line. The cylinder rod then moves in or
out and changes the cutter unit's position.
In the "FLOAT" position, the spool will open both
sides of the cylinder to the return line. The cylinder
rod is then free to move since oil can enter or
leave either side of the cylinder.
There are two valve sections for each side of the
tractor. One is for TILT, one is for LIFT. The
sections are bolted together between an inlet and
an outlet section. The LIFT section has three
positions: UP, HOLD and DOWN & FLOAT. The
TILT section has four positions: UP, HOLD, OUT
and FLOAT.
A pressure relief valve is mounted in the inlet
section of the valve. When a cylinder is bottomed,
the relief valve will open and allow oil from the
gear pump to return to the reservoir.