Alamo 803213C, FC-FL-0001 Hydraulic Gear Pump, Sectional Control Valve

MAINTENANCE

INTERSTATER 03/09 Maintenance Section 5-23

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.

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 cylinde r.

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 sectio n of the va lve. Wh en a cylinder is bottomed, the relief valve

will open and allow oil from the gear pump to return to the reservoir.