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| Illustration 1 | g00997384 |
The tank contains oil for the following machine systems: steering system, hoist system, suspension system, brake system and fan drive system. Return line filters are located inside the tank.
Piston pump (12) is a variable displacement pump. The piston pump, which is driven by the torque converter, supplies oil to the steering system. The output of the piston pump, which is controlled by load sensing pressure, passes through signal and pressure reducing valve (6) .
Electric drive pump (13) supplies oil to the secondary steering system. The electric drive pump, which is a gear pump, is driven by an electric motor which is connected to the battery. The electric drive pump is activated if pressure switch (5) senses a low pressure from piston pump (12) or if a switch in the operator's compartment is pressed.
The outlet ports of signal and pressure reducing valve (6) and electric drive pump (13) are connected to steering check and combiner valve (11). The steering check and combiner valve supplies metering pump (4). The metering pump is a gerotor pump which supplies oil to steering cylinders (7). The metering pump contains two makeup valves which are an integral part of the valve spool within the metering pump and two relief valves which protect the steering cylinder lines and the steering cylinders. The metering pump rotates as the steering wheel rotates.
Gear pump (8) supplies oil to the hoist system. The gear pump is a fixed displacement pump which is driven by the torque converter.
Hoist control valve (1) controls hoist cylinders (2) and tailgate cylinder (3). Counterbalance valve (9) ensures that the tailgate cylinder operates with the hoist cylinders. The hoist control valve is operated by pilot pressure, which is supplied from the brake system. The hoist control valve is electrically controlled. Relief valve (1b) limits the system pressure.
Lowering control valve (1a) can be opened in order to connect the piston side of the hoist cylinders to the tank. On earlier machines, lowering control valve (10) can be opened in order to connect the electric drive pump to the rod sides of the hoist cylinders. These components are used to lower the dump body if the engine is not operational.
On earlier machines, suspension cylinders (21) are connected to accumulators (14) which act as suspension springs. The suspension system is a closed system. The oil is blocked by control valves (15) and control valves (16) .
On earlier machines, control valves (15) can connect the piston pump for the brake system to the suspension system. Control valves (16) can connect the suspension system to the tank. The control valves are used to set the ride height of the front suspension.
Gear pump (22) supplies oil to the fan drive system. Fan motor (19) is driven by oil from the gear pump.
On earlier machines, the fan speed is controlled by thermal valve (17) and hydraulic fan valve (18). On later machines, the fan speed is controlled by solenoid valve (20). Bypass valve (23) directs hot oil through the oil cooler.