TM5-3805-260-24The one-way check valves are used to let air flow inone direction only. Air, coming into the check valve onthe internal thread end of the valve, will put spring (3) incompression and valve (2) will open. Air under pressureis now’ free to flow through the check valve.Air, coming into the check valve on the externalthread end, will push valve (2) against seat (I). The flowof air is stopped.Brake Control ValveWhen the brake pedal is pushed, a force is put onseat (I). This force pushes rubber spring (2) and pistonassembly (3) down. Valve seat (7) closes exhaustpassage (12) in valve (9). Piston assembly (3) movesvalve (9) off of valve seat (8). Pressure air from inletpassage (13) goes around salve (9) to outlet passage(6). The air then goes to the relay valve for the scraperand tractor air chambers.TYPICAL LOCATION OF BRAKE CONTROL VALVE(Under Pedal)BRAKE CONTROL VALVE1. Seat. 2. Rubber spring (2). 3. Piston assembly. 4.Retainer. 5. Spring. 6. Outlet to double check valve.7. Valve seat. 8. Valve seal. 9. Valve. 10. Valve body.11. Valve spring. 12. Exhaust passage. 13. Inletpassage to dry tank. 14. Exhaust diaphragm.When the air pressure below piston assembly (3)becomes more than the force above the piston, thepiston lifts enough to let valve (9) move up to valve seat(8). This stops the supply of pressure air. Pistonassembly (3) is still in contact with valve (9), so exhaustpassage (12) is also closed. The control valve is now inbalance. A pressure is held in thelines and the air chambers for the wheel brakes.If the pedal is lifted a small amount, the mechanicalforce above piston assembly (3) is less. The pressureair below the piston and the force of spring (5) will lift thepiston off of valve (9). Pressure air in the lines and theair chambers goes around piston assembly (3), throughexhaust passage (12) and out exhaust diaphragm (14)until the forces above and below the piston are inbalance. When the pedal is complete released, pistonassembly (3) moves off valve (9) and releases the airpressure. valve (9) is held against valve seat (8) byspring (11).Differential Lock ValveThe differential lock valve controls the supply of air tothe differential lock cylinder and to the control port of thepilot salve. Depressing the pedal moves plunger (I) andspool (2) down unseating valve (5) and allows air to flowfrom supply port (6) out through delivery port (4) to thelocking piston and the pilot valve. Releasing the pedalallows the valve return, sealing supply port (6) andallowing air to flow from the piston and pilot valve outthrough exhaust port (3).DIFFERENTIAL LOCK VALVE1. Plunger. 2. Spool. 3. Exhaust port. 4. Delivery port.5. Valve. 6. Supply port.2-133
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