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| Illustration 1 | g00984572 |
Location of the accumulator charging valve | |
The accumulator charging valve is located on the left side of the front frame, in the transmission compartment.
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| Illustration 2 | g00290902 |
Port locations for the accumulator charging valve (1) Accumulator port for the front brakes (2) Inlet from the brake and pilot pump (3) Plug (4) Outlet to the hydraulic tank (5) Accumulator port for the rear brakes (6) Pressure relief valve (7) Port for the brake accumulator oil pressure switches | |
The brake and pilot section of the gear pump supplies hydraulic oil to the braking system. The oil first flows to the brake accumulator charging valve. The accumulator charging valve maintains the pressure in the brake accumulators at a constant range while the engine is running.
The inverse shuttle section of the accumulator charging valve senses the lower pressure of the two accumulator pressures. The oil then flows from the inverse shuttle section of the accumulator charging valve to the brake accumulator oil pressure switches.
A spool in the accumulator charging valve then moves in order to allow the hydraulic oil to flow to one accumulator or to both accumulators. In addition, the brake and pilot section of the gear pump supplies oil to the parking brake circuit, the hoist pilot circuit and the steering pilot circuit. Any excess oil which is not required for these systems is diverted back to the hydraulic tank.
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| Illustration 3 | g00879865 |
Schematic for the accumulator charging valve (1) Accumulator port for the rear brakes (2) Inlet from the brake and pilot pump (4) Outlet to the hydraulic tank (5) Accumulator port for the front brakes (6) Pressure relief valve (7) Port for the brake accumulator oil pressure switches (8) Flow control valve (9) Orifice for controlling the rate of oil charge to the brake accumulators (10) Check valve (11) Spool for cut-in and cut-out pressure (12) Inverse shuttle valve | |
The accumulator charging valve contains the following internal components; a pressure relief valve, a flow control valve, a flow control orifice, a spool for cut-in and cut-out pressure and an inverse shuttle valve.
The accumulator charging valve controls the flow of oil from the brake and pilot section of the gear pump to the brake accumulators. Pressure relief valve (6) limits the oil pressure that flows from the brake and pilot section of the gear pump to the braking circuit.
Flow control valve (8) regulates the flow of oil to the braking circuit. Any excess oil that is not required by the pilot circuit or the braking circuit is diverted back to the hydraulic tank.
Note: Flow control valve (8) contains shims that set the stand-by pressure of the brake and pilot pump. When the pump is at stand-by pressure, the brake accumulators do not require charging.
Check valve (10) prevents oil from flowing through the accumulator charging valve, and back to the brake and pilot pump.
Spool (11) is for controlling the cut-in and the cut-out pressures for the accumulator charging valve. When the oil pressure in the braking circuits reaches the cut-in pressure, spool (11) shifts. The movement of spool (11) causes the spool in control valve (8) to also shift. This stops the flow of oil to inverse shuttle valve (12) .
Oil flows through inverse shuttle valve (12) to the brake accumulators during oil charge. Pressure oil from inverse shuttle valve (12) flows to the oil end of the two brake accumulators. However, the oil flow between the two brake accumulators is kept separate. Inverse shuttle valve (12) is designed to charge each brake accumulator when the pressure reaches the cut-in pressure.
Port (7) from inverse shuttle valve (12) connects to the two brake accumulator oil pressure switches. One switch alerts the operator when the brake oil pressure drops below the minimum operating pressure. The other switch engages the parking brake if the pressure further decreases.