BAFFLE AS 2739623 - Caterpillar

Illustration 1 g00278177
Location of retarder air control valve
Whenever the operator needs to retard the machine, a hand control that is on the right side of the steering column provides a modulated application of the service brakes.The retarder air control valve is under the dashboard. The hand control is connected to the retarder air control valve by a shaft assembly.
Illustration 2 g00278178
(1) Cam for the air control valve
(2) Piston
(3) Valve seat for exhaust air
(4) Spring
(5) Valve seat for inlet air
(6) Supply passage
(7) Delivery passage
(8) Exhaust passage The retarder air control valve modulates air pressure to the control passage of the brake air relay valve. The delivery pressure is limited to 550 kPa (80 psi). When the hand control is in the OFF position, air at system pressure at supply passage (6) is blocked by the inlet valve. When the hand control is moved out of the OFF position, cam (1) pushes down on spring (4). Spring (4) applies pressure on piston (2). Piston (2) moves downward against the exhaust end of the valve assembly. The exhaust end of the valve assembly contacts valve seat (3). This prevents air from reaching exhaust passage (8). The air inlet end of the valve assembly is off valve seat (5). Supply air flows past the air inlet end of the valve assembly to delivery passage (7).The delivery air pressure below piston (2) will increase until the delivery air pressure is more than the pressure of spring (4) above piston (2). The delivery air pressure will push piston (2) until the air inlet end of the valve assembly is against valve seat (5). The exhaust end of the valve is still against valve seat (3). Delivery air pressure to the control passage of the relay valve will remain constant until the hand control is moved.When the hand control is moved to the OFF position, there is less force on spring (4) . Air pressure will raise piston (2). Delivery air pressure is allowed to flow past valve seat (3) to exhaust passage (8). This occurs until the force above piston (2) and below piston (2) is equal. When the air pressure is equal, the exhaust end of the valve assembly seats on valve seat (3).