PLATE AS. - 2990588 - Caterpillar

Illustration 1 g06238627
Illustration 2 g06238636
The service brake control valve (1) is located under the service brake pedal in the operator station.
Illustration 3 g06238632
(1) Port from hydraulic accumulator
(2) Service brake pedal
(3) Port to brakes
(4) Port to tank
(5) Spool
(6) SpringThe service brake control valve is actuated by depressing service brake pedal (2). When, brake pedal (2) is depressed spool (5) is lifted actuating the service brake control valve.Modulation of the pressurized oil in the hydraulic accumulator to the braking system is controlled by the service brake control valve. The position of brake pedal (2) causes a specific pressure at the brakes. As the position of brake pedal (2) changes, the pressure to the brakes change.When the operator pushes brake pedal (2), brake pedal (2) lifts spool (5) in the service brake control valve. Pressure oil from the hydraulic accumulator is blocked at port (1) and the oil in the service brakes flows from port (3) through spool (5) and is returned to the hydraulic tank through port (4). The oil pressure in the brakes decreases, causing the brakes to apply.When, the parking is released and service brake pedal (2) is not depressed oil flows from the hydraulic accumulator to port (1) of the service brake control valve. Oil flows from port (1) through spool (5) to port (3) for the brakes. Pressure oil at port (3) is also sent to the bottom of the spool (5), spool (5) lifts and reduces the pressure of the oil supplied from the hydraulic accumulator to the brakes.