GUIDE A. 7B5485 - Caterpillar

Illustration 1 g00652809
"Slack Adjuster" for the "Rear Service Brakes"
Operation of the "Slack Adjuster" keeps the timing constant between the pushing of the "Service Brake Air Control Valve" and the stopping of the machine. Because of the "Slack Adjuster", the same brake application will work with new brakes or with worn brakes. The "Slack Adjuster" is full of oil. The "Slack Adjuster" is located between the air/hydraulic cylinders and the brakes.
Illustration 2 g06266950
Components of slack adjuster
(1) Outlet to a brake
(2) Piston
(3) Inlet from air/hydraulic cylinder
(4) Piston
(5) Outlet to a brake
(6) Oil chamber
(7) Oil passage
(8) Small piston
(9) Small piston
(10) Oil passage
(11) Oil chamber
(12) Passage for makeup oil
(13) Passage for makeup oilWhen the "Service Brake Air Control Valve" is used or when the "Retarder" is used, the "Air/Hydraulic Cylinder" sends oil to inlet (3) and into the "Slack Adjuster". The oil pressure in the "Slack Adjuster" pushes pistons (2) and (4) away from the center of the "Slack Adjuster". Pistons (2) and (4) push the oil in oil chambers (6) and (11) through outlets (1) and (5) to the brakes in each wheel. This oil initiates the brake application.If the brakes have worn, the oil from chambers (6) and (11) may not complete the brake application. When pistons (2) and (4) are against the ends of the "Slack Adjuster", the oil from the "Air/Hydraulic Cylinders" fill oil passages (7) and (10). If the pressure in passages (7) and (10) is higher than the pressure in outlets (1) and (5), small pistons (8) and (9) move away from the piston seats. Additional oil from the "Air/Hydraulic Cylinders" can flow through the open piston seats to passages (12) and (13). This oil flows through outlets (1) and (5) to complete the brake application.When you stop applying the brakes, the "Air/Hydraulic Cylinder" will not send oil to the "Slack Adjuster". The lower pressure in outlets (1) and (5) will cause small pistons (8) and (9) to return to the piston seats. Small pistons (8) and (9) will block passages (12) and (13). When oil stops filling the brakes, the return springs in the brakes will push the service brake pistons. The service brake pistons push the oil from the brake application back into outlets (1) and (5) of the "Slack Adjuster". This oil pushes pistons (2) and (4) to the center of the "Slack Adjuster". The brake is released completely.