YOKE-BRAKE 1085734 - Caterpillar

Illustration 1 g00689800
The parking and secondary brake control valve is located in the operator's compartment to the right side of the operator.
Illustration 2 g00303024
Parking and secondary brake control valve (2) Knob (3) Valve body (4) Spring (5) Orifice (6) Outlet port to brake actuators (7) Inlet port from air reservoir (8) Exhaust port to atmosphere (9) Valve assemblyWhen the reservoir is discharged, parking and secondary brake control valve (1) will be in the ON position. Parking and secondary brake control valve (1) is in the ON position when knob (2) is pulled out. Valve (9) will be seated against the upper face of valve body (3). This will isolate pressurized air from outlet port (6) and exhaust port (8). Air pressure in the reservoir is allowed to increase to the operating range.When the air pressure gauge registers a pressure within the operating range, the operator must push knob (2) and the operator must hold knob (2) in order to release the brakes. Pressurized air from the reservoir enters the valve through inlet port (7). The air then passes through orifice (5). The air then exits through outlet port (6) to the brake actuators, which release the brakes. Air pressure then holds valve (9) seated over exhaust port (8) .Parking and secondary brake control valve (1) can be actuated manually. To actuate parking and secondary brake control valve (1) manually, the operator must pull knob (2) .Parking and secondary brake control valve (1) can also be actuated by a pressure reduction in the air system. If the air system fails or if the pressure drops below approximately 275 35 kPa (40 5 psi), spring (4) will unseat valve (9). This will cause the pressurized air to exhaust to the atmosphere, which will apply the brakes. Parking and secondary brake control valve (1) will remain open until the pressure in the system is greater than 380 35 kPa (55 5 psi).