PROTECTOR 1003587 - Caterpillar

Illustration 1 g03121777The service brake control valve is located under the front of the cab.The service brake control valve is actuated by depressing the service brake pedal in the cab. When the brake pedal is depressed, a roller on the pedal assembly actuates the service brake control valve.The service brake control valve is a dual pressure reducing valve with two independent output pressures.
Illustration 2 g01412318
Service Brake Control Valve
(A) Supply ports from the brake accumulator charging valve. (B) Return ports to the hydraulic tank. (C) Supply ports to the service brakes.
Modulation of the pressurized oil in the accumulators to the service brakes is controlled by the service brake control valve. The position of the brake pedal causes a specific pressure at the service brakes. As the position of the pedal changes, the pressure also changes at the service brakes.
Illustration 3 g01411987
View (A-A) of the service brake control valve
(1) Piston
(2) Spring
(3) Spring
(4) Retainer
(5) Ball
(6) Spacer
(7) Upper valve spool
(8) Outlet to rear service brakes
(9) Outlet to hydraulic oil tank
(10) Passage
(11) Supply from accumulator for the rear service brakes
(12) Drain port to tank
(13) Upper valve spool passage
(14) Cavity
(15) Lower valve spool
(16) Plug
(17) Outlet to front service brakes
(18) Passage
(19) Lower Valve spool passage
(20) Supply from accumulator for the front service brakes
(21) Cavity
(22) Spring The service brake control valve modulates the flow of pressurized oil. The flow of pressurized oil is modulated between the brake accumulators and the service brakes. The position of either brake pedal causes a specific pressure at the service brakes. As the position of the pedal changes, the pressure at the service brakes also changes.When the operator pushes the brake pedal, a roller on the brake pedal assembly forces piston (1) downward. Piston (1) applies force on springs (2) and (3). The force of springs (2) and (3) moves retainer (4) and ball (5). Movement of retainer (4) and ball (5) causes upper valve spool (7) to move away from the seat in spacer (6).The movement of upper valve spool (7) causes the movement of lower valve spool (15) and the compression of spring (22). When valve spools (7) and (15) move, passages (10), (12), and (18) block oil flow to the hydraulic oil tank. Pressurized oil from accumulator ports (11) and (20) flow through passages (10), (13), (18), and (19). The oil then flows through passages (8) and (17) in order to apply the service brakes. At the same time, pressurized oil flows into cavities (14) and (21), and through passages (13) and (19). The oil pressure at the service brakes has the same pressure as the oil in cavities (14) and (21).Oil pressure in cavity (21) and the force of spring (22) act to balance lower valve spool (15) against the force of the pressure in cavity (14). In the same manner, pressure in cavity (14) creates a force against the bottom of upper valve spool (7). The upper valve spool