BENDIX M-21-M-22 ANTILOCK MOD ASSY Servisní příručka stáhnout pdf (Strana 12)

Double Check and Quick Release Valve (QR-1C)

The Double Check and Quick Release Valve (QR-1C) is a dual function valve. The

valve’s primary function is to serve the emergency side of a spring brake actuator as a

quick release valve. In addition, it functions as an anti-compound device. The double

check valve prevents a service and emergency brake application from occurring simul-

taneously. The air connectors to the valve are as follows:

1. Valve delivery port (2) connected to emergency port of spring brake.

2. Valve balance port (1) connected to delivery of brake valve or relay valve.

NOTE: If relay valve is installed on vehicle it should be connected to the delivery

side (not service or signal side).

OPERATION

Spring Brakes Released

When the spring brakes are released, air from the park control valve flows through the

QR-1C Valve, causing the double check valve and the quick release diaphragms to

flex and seal the balance and exhaust ports. Air flows into the emergency port of the

spring brakes from the QR-1C Valve delivery ports.

Spring Brakes Applied

When the spring brakes are applied, supply line air pressure to the valve is exhausted

through the park control valve. As air pressure is removed from one side of the double

check valve and quick release diaphragms they flex in opposite direction, opening the

balance and exhaust ports. Spring brake emergency pressure is released at the

exhaust port of the valve, while the small amount of air trapped between the two

diaphragms is released through the relay valve or brake valve exhaust.

Anti-compounding

When a service brake application is made with the spring brakes applied, service air

enters the balance port and flows through the valve into the emergency ports of the

spring brakes. This prevents the compounding of a service and spring brake applica-

tion. Service air passing through the valve flexes the double check and quick release

diaphragms, sealing the supply and exhaust ports. When the service application is

released, air is exhausted from the spring brakes.

Air Brake System

Revised 11/15/99

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BENDIX M-21-M-22 ANTILOCK MOD ASSY Servisní příručka Strana 12