Bendix Commercial Vehicle Systems R-14 RELAY VALVES 5/10 - Manual (Page 2)

2
be conveniently used as either a service or spring brake
relay valve. An exhaust cover is installed that protects the
1/8” balance port when the R-14
® valve anti-compound
feature is not in use.
All parts are interchangeable between the R-12 ® and R-14 ®
valves with the exception of the detail components of the
R-14
® valve cover. Both valves make extensive use of
non-metallic internal components. For ease of servicing,
the inlet/exhaust valve can be replaced without the need
for line removal.
OPERATION
APPLICATION
Air pressure delivered to the service port enters the small
cavity above the piston and moves the piston down. The
exhaust seat moves down with the piston and seats on the
inner or exhaust portion of the inlet/exhaust valve, sealing
off the exhaust passage. At the same time, the outer or
inlet portion of the inlet/exhaust valve moves off its seat,
permitting supply air to fl ow from the reservoir, past the
open inlet valve and into the brake chambers.
BALANCE
The air pressure being delivered by the open inlet valve
also is effective on the bottom area of the relay piston.
When air pressure beneath the piston equals the service
air pressure above, the piston lifts slightly and the inlet
spring returns the inlet valve to its seat. The exhaust
remains closed as the service line pressure balances the
delivery pressure. As delivered air pressure is changed,
the valve reacts instantly to the change, holding the brake
application at that level.
EXHAUST OR RELEASE
When air pressure is released from the service port and air
pressure in the cavity above the relay piston is exhausted,
air pressure beneath the piston lifts the relay piston and the
exhaust seat moves away from the exhaust valve, opening
the exhaust passage. With the exhaust passage open,
the air pressure in the brake chambers is then permitted
to exhaust through the exhaust port, releasing the brakes.
ANTI-COMPOUNDING (SIMULTANEOUS
SERVICE AND PARK APPLICATION)
In those applications where the R-14 ® relay valve is used to
control spring brake chambers, the anti-compound feature
may be utilized. With the anti-compound feature of the
R-14
® valve connected, a service application made
while the vehicle is parked is countered by a release of
the parking brakes. To utilize this feature, the exhaust
cover of the quick release portion of the R-14
® valve is
removed and a line is installed which is connected to
the delivery of the service brake valve or relay valve.
With no air pressure at the service port of the R-14
®
valve, the parking brakes are applied. If a service brake
application is made, air from the service brake valve
enters the exhaust port of the quick release of the
R-14
® valve and moves the diaphragm, blocking the service
port. Air then proceeds into the cavity above the relay
piston, forces the piston down, closing the exhaust and
opening the inlet to deliver air to the spring brake cavity
as described under the section of this manual entitled
Application.
INLET/
EXHAUST
ASSEMBLY
EXHAUST COVER
FIGURE 2 - SECTIONAL VIEWS
RELAY
PISTON
INLET
EXHAUST
VALVE
ASSEMBLY
R-14H R-12V
RETAINING
RING
EXHAUST
SEAT
RELAY
PISTON
EXHAUST
SEAT
RETAINING
RING
EXHAUST
PORT
DIAPHRAGM
BALANCE/QUICK EXHAUST PORT
(ANTI-COMPOUND)
EXHAUST
PORT