HOSE AS 3468414 - Caterpillar

Service Brake Disengaged, Parking Brake Disengaged
Illustration 1 g03394921
(A) Oil from the hoist system or the ejector system (B) Oil to the hoist system or the ejector system (C) Oil to ejector system (740B Ejector only) (D) Oil to the control system for the cross axle differential locks (1) Service brake (Front) (2) Oil cooler (3) Manifold (4) Pressure switch (5) Accumulator (Center) (6) Check and pressure reducing valve (7) Pressure switch (8) Accumulator (Parking Brake) (9) Pressure switch (10) Service brake (Center) (11) Pressure switch (12) Brake control valve (service) (13) Accumulator (Front) (14) Brake control valve (Parking) (15) Parking brake (16) Temperature sensor (17) Service brake (Front) (18) Piston pump (Brake) (19) Service brake (Center) (20) Temperature sensorWhen the pedal in the cab is not operated, the service brakes are disengaged.Oil flows from piston pump (18) through check and pressure reducing valve (6) . The oil is blocked by the spools of brake control valve (12) . Oil flows into accumulators (5) and (13) .Oil also flows through brake control valve (14) into accumulator (8) . Oil flow though the brake control valve depends on the position of the parking brake control. Refer to Systems Operation, Testing and Adjusting, "Parking Brake System" for further information.Accumulators (5) and (13) charge until the required system pressure is achieved. When the required system pressure is achieved, the pump control valve, which is part of piston pump (18) , moves and the piston pump destrokes. The piston pump continues to produce enough flow in order to overcome losses within the system. The check valves within check and pressure reducing valve (6) maintain pressure in the accumulators.Check and pressure reducing valve (6) supplies oil at a reduced pressure to the hoist/ejector pilot pressure system. The check and pressure reducing valve also supplies oil at a reduced pressure to the control system for the cross axle differential locks.On 740B Ejector machines only, piston pump (18) supplies oil to the ejector system.Service Brakes Engaged, Parking Brake Disengaged
When the pedal in the cab is pressed, the service brakes are engaged.Oil flows through brake control valve (12) to service brakes (1) and (17) for the front axle. Oil also flows through brake control valve (12) to service brakes (10) and (19) for the center axle.Pressure in the lines to the service brakes activates pressure switches (4) and (11) . Pressure switch (4) causes the brake lights to illuminate. Pressure switch (11) changes the downshift point of the transmission in order to maintain engine speed.Pressure drops in the line from piston pump (18) which causes the pump control valve to move and the piston pump upstrokes. The pump control valve is part of the piston pump. The pump upstrokes until the required system pressure is achieved and accumulators (5) and (13) are fully charged.If the engine or the piston pump fail, accumulators (5) and (13) supply the oil flow that is required to engage the service brakes.Component Locations
Illustration 2 g02463385
Typical exampleService brakes (1) , (10) , (17) , and