HOUSING 4M2281 - Caterpillar

Illustration 1 g01138165The parking brake control valve is located on the left side of the rear frame.
Illustration 2 g01138468
Parking brake control valve
(1) Parking brake solenoid valve for the remote control system
(2) Parking brake solenoid valves
(3) Solenoid valve for implement and steering lockout
(4) Pressure tap for the parking brake circuit
(5) Port from the pilot relief valve
(6) Port to brake release sequence valve
(7) Port to hydraulic tank
(8) Parking brake oil pressure switch
(9) Port to parking brakes The parking brake control valve has two parking brake solenoid valves (2) controlled by a parking brake switch in the operator station. The remote control system when fitted also controls the operation of parking brake solenoid valve (1) and parking brake solenoid valves (2). The operation of parking brake solenoid valve (1) is identical to parking brake solenoid valves (2).
Illustration 3 g01138542
Schematic for the parking brake control valve
(1) Parking brake solenoid valve for the remote control system
(2) Parking brake solenoid valves
(3) Solenoid valve for implement and steering lockout
(4) Pressure tap for the parking brake circuit
(5) Port from the pilot relief valve
(6) Port for brake release sequence valve
(7) Port to hydraulic tank
(8) Parking brake oil pressure switch
(9) Port to parking brakes
(10) Spool When the engine is running and the parking brake switch is in the ON position, no power is supplied to solenoids (2). Pressure oil from the pilot relief valve at port (5) is stopped by valve spools (10). The parking brakes are engaged by the force of the parking brake springs. Oil from the parking brakes is free to return to the hydraulic tank through port (9), valve spools (10) and port (7).When the parking brake switch is moved to the OFF position, power is supplied to solenoids (2). Solenoids (2) energize and move valve spools (10). Pressure oil from the pilot relief valve at port (5) flows through valve spools (10) and port (9) to the parking brakes. Oil pressure disengages the parking brakes and allows the machine to move.Machines equipped with the brake release system contain the brake release sequence valve which is connected to port (6). When the parking brake is disengaged, oil pressure is directed through port (6) to the brake release sequence valve.