GILLIG LOW FLOOR, Service Manual

Page: 238 / 506

238
Air System
quick Release Valve (Bendix qR-)
The quick release valve (Figure 6- 36) is used
in the air distribution system at the front
brakes. The purpose of this valve is to reduce
the time required to release the brakes by
hastening the exhaust of air pressure from
the brake chambers. When a brake applica-
tion has been made and released, the exhaust
port of the quick release valve opens and
the air pressure from the brake chambers is
exhausted through the quick release exhaust
port rather than back through the brake ap-
plication valve.
qR- Valve Operation
When a brake application is made, air pres-
sure enters the brake valve port. The dia-
phragm moves down, sealing the exhaust. At
the same time, air pressure forces the edges
of the diaphragm down and air flows out the
delivery port. When air pressure beneath
the diaphragm equals the pressure above the
diaphragm, the outer edge of the diaphragm
will seal against the body seat. The exhaust
port is still sealed by the center portion of the
diaphragm when the brake valve application
is released. The air pressure above the diaphragm is released back through the brake valve exhaust. Air
pressure beneath the diaphragm forces the diaphragm to rise, opening the exhaust and allowing the air in
the brake chambers to exit.
qR- Preventive Maintenance
Every 100,000 miles, 12 months, or 3600 operating hours, disassemble the valve, wash metal parts in
mineral spirits and wipe rubber parts dry. Bendix recommends that all rubber parts and any components
showing wear or deterioration be replaced; contact your Gillig parts representative for valve rebuild kits.
qR- Operating and Leakage Tests
While holding a foot brake valve application, coat the exhaust port with soap solution. Leakage of a 1"
bubble in 3 seconds is permitted. Next, coat the body and cover with a soap solution. No leakage is per-
mitted between the cover and body.
Figure 6-36, Quick Release Valve
SUPPLY
(FROM BRAKE VALVE)
DELIVERY
(TO CHAMBER)
O-RING
DIAPHRAGM
BODY
20-500-32
EXHAUST