 | |
| Illustration 1 | g01511653 |
(1) Rear service brakes (2) Wires to transmission electronic control module (3) Left brake pedal (4) Wires to stop lamps (5) Right brake pedal (6) Service brake control valve (7) Accumulator for the rear service brakes (8) Accumulator for the front service brakes (9) Front service brakes (10) Fan (11) Brake oil pressure switch (12) Gear motor (13) Piston pump (14) Hydraulic oil cooler (15) Hydraulic oil filter (16) Control manifold (17) Breaker relief valve (18) Hydraulic tank (AA) Pressure tap for the rear service brakes (BB) Pressure tap for the front service brakes (CC) Pressure tap for the service brake accumulators | |
 | |
| Illustration 2 | g01511693 |
Left side view of the machine (1) Rear service brakes (9) Front service brakes (12) Gear motor (17) Breaker relief valve (18) Hydraulic oil tank | |
 | |
| Illustration 3 | g01511697 |
Right side view of the machine (6) Service brake control valve (7) Accumulator for the front service brakes (8) Accumulator for the rear service brakes (11) Brake oil pressure switch (13) Piston pump (16) Control manifold (AA) Pressure tap for the front service brakes (BB) Pressure tap for the rear service brakes | |
Piston pump (13) supplies the hydraulic oil that is required in order to operate the brake and the hydraulic fan system. Oil flows from pump (13) to control manifold (16). The control manifold includes the following components: a pressure relief valve, a shuttle valve, an inverse shuttle valve, a cut in valve, a cut off valve, a priority valve, a proportional solenoid valve and a check valve.
Control manifold (16) controls the flow of oil from pump (13) to brake accumulators (7) and (8). The control manifold (16) also controls the flow of oil to gear motor (12) for the hydraulic fan. A cut off valve that is located in control manifold (16) limits the oil pressure that flows from pump (13) .
Control manifold (16) contains a priority valve. When this valve is closed, oil flows to an inverse shuttle valve that is located in control manifold (16). The oil then flows to brake accumulators (7) and (8). When the accumulators are charged, the priority valve opens. Oil then flows to gear motor (12) for the hydraulic fan system. A port in control manifold (16) connects to brake oil pressure switch (11). Brake oil pressure switch (11) monitors the oil pressure in the brake accumulators. If the oil pressure in either brake accumulator drops below the minimum threshold, switch (11) actuates.
Brake accumulators (7) and (8) contain a precharge of dry nitrogen. When oil flows into an accumulator, the pressure oil moves the piston inside the accumulator. The piston moves against the charge of dry nitrogen gas. This puts compression on the dry nitrogen until the oil pressure reaches the cut out pressure. The oil also flows to service brake control valve (6) .
Service brake control valve (6) is in the circuit from the accumulators to the service brakes. When a brake pedal is pushed, oil from each accumulator flows to the service brakes. The service brakes are then applied.
When service brake control valve (6) is released, the lines from the accumulators are blocked. The brake lines are connected to the drain port. This allows the service brakes to release. The supply oil is then dumped back into hydraulic oil tank (18) .
Each brake application removes a quantity of oil from the accumulators. The piston in each accumulator moves toward the port end for the oil until the oil pressure decreases to the cut-in pressure. Control manifold (16) then permits oil from pump (13) to flow to brake accumulators (7) and (8). This occurs until the pressure increases to the cut out pressure.
The hydraulic circuits for the front service brakes and for the rear service brakes are completely separate. Applying force to a brake pedal causes the tandem spools in service brake control valve (6) to move. This allows oil from both accumulator (7) and accumulator (8) to flow to the brakes in each axle housing. The pressure of the oil causes the wet disc brakes that are enclosed in each axle to engage. The heat from the friction of the brakes is removed by the oil in the axle housings.
If brake oil pressure is lost during machine operation, the transmission shifts to neutral. However, the transmission only shifts to neutral when the machine is in either FIRST SPEED FORWARD or FIRST SPEED REVERSE.1F-N-1F or 1R-N-1R