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| Illustration 1 | g00946356 |
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Brake system schematic (1) Pressure switch for the parking brake (2) Parking and secondary brake (3) Accumulator charging valve (4) Accumulator (5) Inverse shuttle check valve (6) Check valve (7) Parking brake control valve (8) Right service brakes (9) Pressure switch for low oil pressure (10) Pilot control valve (11) Pressure relief valve (12) Slack adjusters (13) Oil filter (screen) (14) Check valve (15) Brake pump (16) Oil filter (17) Unloading valve (18) Manifold (19) Service brake control valve (20) Left service brakes (21) Left tandem housing (22) Electric drive pump (secondary brake) | |
Brake pump (15) provides oil flow for the service brakes. Oil flows from the pump to accumulator charging valve (3).
Accumulator charging valve (3) controls the amount of oil that flows to accumulators (4). The accumulator charging valve contains the following components: inverse shuttle check valve (5), pilot control valve (10), check valve (14), unloading valve (17) and pressure relief valve (11).
Pressure oil flows through inverse shuttle check valve (5) to accumulators (4) when the accumulators are being charged. The inverse shuttle check valve keeps the oil flow between the two accumulators separate. The inverse shuttle check valve charges each accumulator as the accumulator pressure falls.
Check valve (14) in accumulator charging valve (3) prevents oil from flowing back through the charging valve.
A third port in inverse shuttle valve (5) is used to connect pressure switch (9). The pressure switch alerts the operator when there is inadequate brake pressure in the brake system.
As pressure oil flows into each accumulator (4), the oil will compress against the piston in the accumulators. This will compress the dry nitrogen until the oil pressure reaches the cut out pressure for accumulator charging valve (3). The oil also flows to service brake control valve (19). The accumulator charging valve closes when the accumulators reach the cut out pressure and the pump pressure goes to the standby pressure. Check valve (14) holds pressure in the accumulators. Refer to Specifications, "Accumulator Charging Valve" for your machine for information on the cut-in pressure, cut out pressure, and standby pressure.
Each brake application will remove some oil from accumulators (4). The piston in each accumulator moves toward the oil end of the accumulator until the pressure reaches the cut-in pressure. Accumulator charging valve (3) then permits oil from the pump to flow to the accumulators until the pressure reaches the cut out pressure.
Service brake control valve (19) controls right service brakes (8). The service brake control valve also controls left service brakes (20). The service brake control valve is in the line between accumulators (4) and the service brakes. When the brake pedal is depressed, oil from each accumulator flows to the brakes in order to apply the brakes.
When the brake pedal is depressed, the service brakes in each spindle are applied. Depressing the brake pedal causes the tandem spool in service brake control valve (19) to move. Oil from accumulators (4) flows to the brakes in each spindle. The heat from the friction of the brakes is removed by the oil in the tandem housing.
When the brake pedal is released, service brake control valve (19) blocks the lines from accumulators (4) and the brake lines are opened to the tank port. The service brakes are released and the oil flows back to the tandem housing.
Parking brake control valve (7) has a manually operated spool. The parking control valve controls the flow of oil pressure to parking brake (2).