TM 5-3805-258-24-1SYSTEMS OPERATIONA I R S Y S T E M A N D B R A K ESA I R C I R C U I T F O R T H E E M E R G E N C Y A N D P A R K I N G B R A K EQUICK RELEASE VALVE FOR EMERGENCYAND PARKING BRAKEQ U I C K R E L E A S E V A L V E I N A P P L Y I N G P O S I T I ON1. Outlet port, 2. O-ring seal. 3. Cover. 4. Inlet port. 5.Diaphragm. 6. Body. 7. Exhaust port. 8. Plug.The quick release valve hastens the exhaust of airfrom the brake chamber for the emergency and park-ing brake. The quick release valve has three positionsduring operation. These positions are the APPLY-ING position, when air under pressure passesthrough the valve into the brake chamber; theHOLD position, when pressure is held in the brakechamber; and the RELEASE position, when thebrake chamber exhausts.Q U I C K R E L E A S E V A L V E I N H O L D I N G P O S I T I ONWhen the parking brake disengages (control valvein OFF position), air under pressure enters inlet port(4) of the quick release valve, and moves diaphragm(5) down, closing exhaust port (7). The outer edgesof the diaphragm are deflected downward. Pressureair passes through outlet port (1) to the brakechamber.Q U I C K R E L E A S E V A L V E I N R E L E A S E P O S I T I ONAs soon as the brake chamber pressure below thediaphragm equals the control valve pressure abovethe diaphragm, the edge of diaphragm (5) is forcedup against cover (3). The center of the diaphragmcontinues to cover exhaust port (7). This is theHOLDING position.When the control valve for the emergency andparking brake is moved to ON position, air pressureon the top of the diaphragm is released. The brakechamber pressure below the center of the diaphragmraises it, opening exhaust port (7) and permitting thebrake chamber air to exhaust (RELEASE position).L O C A T I O N O F Q U I C K R E L E A S E V A L VEBRAKE CHAMBER FOR EMERGENCY ANDPARKING BRAKEBrake chamber (6) releases (disengages) and acti-vates (engages) the emergency and parking brake.Brake chamber rod (3) is connected to rod end (7).Rod end (7) is connected to lever (8) which moves theshoes in the brake. When there is no pressure fromthe control valve for the emergency and parkingbrake, there is no air pressure in air chamber (2).Spring (1) holds piston (4) all the way to the rightand keeps the emergency and parking brakeengaged.3-76
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