WIRE 0632948 - Caterpillar

Illustration 1 g00661293
Location of the Pedal and Base for the Service Brake Control
Illustration 2 g00661304
Location of the Valve for the Service Brake ControlThe pedal (1) and base (2) for the service brake control is located on the right side of the floor inside the cab. The valve (3) is located directly under base (2) on the underside of the floor of the cab.
Illustration 3 g00660652
Service Brake Control (1) Pedal (2) Base (3) Valve assembly (4) Return to tank port (5) Brake port for the center service brakes (6) Accumulator port for the center service brakes (7) Spool for the front service brakes (8) Brake port for the front service brakes (9) Accumulator port for the front service brakes (10) Spool for the center service brakesThe service brake control valve is connected to pedal (1) and base (2). There are two spools inside the valve which are offset when the pedal is pressed. Spool (7) controls the oil supply to the front service brakes and spool (10) controls the oil supply to the center service brakes. When the pedal for the service brake is pressed the flow of oil through port (4) is blocked to the hydraulic tank. Spool (7) connects accumulator port (9) to brake port (8) and spool (10) connects accumulator port (6) to brake port (5). Oil pressure from the accumulator for the center service brakes enters valve assembly (3) at accumulator port (6). Spool (10) then directs the oil out of brake port (5) to the brakes for the center axle. At the same time, oil pressure from the accumulator for the front service brakes enters valve assembly (3) at accumulator port (9). Spool (7) directs the oil out of brake port (8) to the brakes for the front axle.The oil pressure in the brake lines is transmitted to the underside of spools (7) and (10) through internal passages. As the pressure increases spool (7) and spool (10) move up. This acts to balance the force that is applied to brake pedal (1). The balanced position of spool (7) and spool (10) block accumulator port (6) and accumulator port (9). Brake port (5) and brake port (8) are also blocked and a constant oil pressure exists in the brake lines until either the force on brake pedal (1) is increased or reduced.The front and center brake groups are activated simultaneously. There is no delay in the engagement of the front axle brakes and the center axle brakes.The supply pressure from the brake pump is 20400 kPa (2950 psi). The maximum pressure in the brake lines is 3100 kPa (450 psi). It is not possible to apply sufficient force to brake pedal (3) that the pressure in the brake line increases above 3100 kPa (450 psi).