ACTUATOR-ROCKER 3E8777 - Caterpillar

Illustration 1 g01135836
Hydraulic schematic for the braking system
(1) Brake release cylinder
(2) Pressure tap for the brake release system
(3) Brake release sequence valve
(4) Connection for recovery bar type brake release system
(5) Parking brake control valve
(6) Shuttle valve
(7) Shuttle valve
(8) Front wheel brakes
(9) Connection for recovery hook type brake release system
(10) Parking brake oil pressure switch
(11) Line to pilot circuit
(12) Check valve
(13) Pressure tap for the parking brake circuit
(14) Brake accumulator oil pressure switch - alert indicator
(15) Brake accumulator oil pressure switch - brake application
(16) Brake accumulator
(17) Service brake pedal
(18) Service brake and transmission neutralizer pedal
(19) Residual brake oil pressure switch
(20) Service brake oil pressure switch
(21) Check valve
(22) Brake accumulator relief valve
(23) Portable hydraulic pump quick connect coupler
(24) Pressure tap for the brake accumulator circuit
(25) Service brake control valve
(26) Pilot relief valve
(27) Pressure tap for the pilot system
(28) Pilot oil filter
(29) Check valve
(30) Portable hydraulic pump quick connect coupler
(31) Brake accumulator charging valve
(32) Pilot and braking pump
(33) Hydraulic tank
(34) Breaker relief valve
(35) Rear wheel brakes Wheel brakes (8) and (35) are divided into two sections. The service brake section is an oil pressure applied and spring released brake. The parking brake section is an oil pressure disengaged and spring engaged brake. The service brake can be used when the parking brake is disengaged.The service brakes are controlled by two brake pedals in the operator station. The left and right brake pedal assemblies are connected by a mechanical linkage. The left pedal is service brake and transmission neutralizer pedal (18). The right pedal is service brake pedal (17).When service brake pedal (17) is depressed, only the service brakes are applied. When service brake and transmission neutralizer pedal (18) is depressed, the service brakes are applied and the transmission is neutralized. This allows the full engine power to be used in the hydraulic system. When service brake and transmission neutralizer pedal (18) is released, the transmission engages and the service brakes are released.With the engine running, oil flows from hydraulic tank (33) to pilot and braking pump (32) which is part of the steering, pilot and braking pump. The oil then flows from pilot and braking pump (32) through check valve (29) to brake accumulator charging valve (31).The piston in brake accumulator (16) is held against the oil intake end with dry nitrogen gas. Brake accumulator (16) stores hydraulic oil pressure for the service brakes. After the service brakes have been activated several times, the volume of oil in the accumulator is less. When the pressure in the brake accumulator decreases, brake accumulator charging valve (31) routes oil from pilot and braking pump (32) to brake accumulator (16). When the brake accumulator oil pressure rises, the charging spool in brake accumulator charging valve (31) blocks the flow of oil to brake accumulator (16) and routes the flow of oil to the pilot circuit.From brake accumulator (16), the oil flows to service brake control valve (25). Service brake control valve (25) is a tandem valve that routes brake oil to both the front axle