RUBBER 3727812 - Caterpillar

Brake and Hoist System
Illustration 1 g03350651
(1) Piston pump (Brake) (2) Engine (3) Transmission (4) Gear pump (Hoist) (5) Brake temperature sensor (6) Pressure switch (brake light and ECM) (7) Brake control valve (foot pedal) (8) Brake accumulators (9) Brake control manifold (10) Pressure sensor (low brake pressure) (11) Parking brake accumulator (12) Parking brake control valve (13) Parking brake pressure switch (14) Parking brake (15) Hoist Control valve (15A) Lowering control valve (stopped engine) (15b) Relief valve (16) Hoist cylinders (17) Suspension cylinders (Front) (18) Hydraulic tank for the hoist and braking systemsThe machine has two hydraulic tanks. Tank (18) contains oil for the hoist and braking systems.The gear pump (4) for the hoist system is driven by the transmission (3) .Gear pump (4) supplies oil to the hoist system. The gear pump is a fixed displacement pump.Hoist control valve (15) controls hoist cylinders (16) . The hoist control valve is operated by pilot pressure, which is supplied by the braking system. The hoist control valve is electrically controlled. Relief valve (15b) limits the system pressure.Lowering control valve (15a) can be opened in order to connect the piston side of the hoist cylinders to the tank. The lowering control valve is used with the lowering procedure for the body. Refer to Operation and Maintenance Manual, "Lowering the Body with the Engine Stopped".Oil for the braking system is contained in the hydraulic tank for the hoist, or the ejector, and braking systems. Return oil from the braking system passes through oil filters which are located in the hydraulic tank.Oil for the service brake cooling system is supplied by the hoist system when the hoist control is in the following positions:
HOLD
RAISE
FLOATPiston pump (1) supplies oil in order to engage the service brakes. The piston pump also supplies oil in order to disengage the parking brake. The piston pump is driven by the engine. The piston pump continuously charges three accumulators. The accumulators can be used to operate the service brakes and the parking brake if the engine or the piston pump are not operational.Parking brake control valve (12) , which is operated by a solenoid, controls the flow of oil to parking brake (14) . The parking brake is located in the drive line. The parking brake can be used to slow the machine if the service brakes are not operational. When the parking brake is engaged, pressure switch (13) sends a signal to the ECM which illuminates an indicator in the cab.Brake control manifold (9) has the following main functions:
Lock pressure in accumulators (8) and (11) if the engine or the piston pump are not operational
Supply pilot pressure to the hoist system
Supply oil pressure to the cross axle differential locksIf the brake system pressure is too low, pressure sensor (10) sends a signal to the ECM. The Caterpillar Monitoring System provides a warning (category 3) if the system pressure is too low.Brake control valve (7) is foot operated and the brake control valve controls the flow of oil to the