TUBE AS 3157497 - Caterpillar

Illustration 1 g02549058Braking is achieved is by using oil to move actuator (1) that holds exhaust valves (2) open. The movement of the exhaust valve is still initiated by the camshaft. The exhaust valves would normally close completely under normal operation. The Cat Compression Brake will prevent the valve from fully closing when braking is desired.
Illustration 2 g02549059Each Cat Compression Brake Actuator contains a piston (4) that is responsible for contacting the valve bridge and preventing the exhaust valves from closing completely. The engine oil return line (4) contains check valve (3). The check valve will prevent engine oil from returning to the supply rail when the exhaust valves are forced to remain open. The valves will remain open during the intake, compression, and power strokes of the cylinder.