Bendix Commercial Vehicle Systems BP-R1 BOBTAIL PROP RELAY VALVE 6/09 - Manual (Page 2)

2
FIGURE 3 - BP-R1 ™ BOBTAIL PROPORTIONING RELAY
VALVE
INLET-EXHAUST
VALVE
SPRING
(NOT USED
IN ALL
MODELS)
INLET-EXHAUST
VALVE
PROPORTIONING
PISTON
CONTROL
PORT
RELAY
PISTON
SPRING
SERVICE
PISTON
SERVICE
PORT
“BLEND
BACK”
PISTON
SUPPLY
PORT
TRAILER
SUPPLY
TRACTOR
PROTECTION
DUAL
BRAKE
VALVE
SERVICE PORT
BP-R1 ™
VALVE
DELIVERY
PORT(4)
SUPPLY
CONTROL
PORT
SERVICE
FIGURE 4 - BP-R1 ™ APPLYING - TRACTOR/TRAILER
COMBINATION
RELAY
PISTON
INLET-
EXHAUST
VALVE
INLET-EXHAUST
PISTON
PROP
PISTON
FIGURE 2 - BP-R1 ™ TRACTOR AIR SYSTEM
of the inlet and exhaust valve. With the exhaust passage
sealed, continued movement of the piston unseats the inlet
portion of the inlet and exhaust valve, allowing supply air
from the reservoir to
fl ow out the BP-R1
™ valve delivery
ports to the brake actuators. (See Figure 4.)
OPERATION
INITIAL CHARGING
During the initial build up of tractor system air pressure,
supply air
fl ows through internal body and cover passages
in the BP-R1 ™ valve to the blend back piston.
Activating the trailer supply valve (dash control with red
octagonal button), simultaneously charges the trailer and
the BP-R1
™ valve control port. Air entering the BP-R1 ™
valve control port causes the proportioning piston to move
toward its stop in the cover. The integral inlet and exhaust
valve is carried along with the piston until it seats and
seals the exhaust passage. Continued movement of the
proportioning piston opens the inlet valve. With the tractor
and trailer air system fully charged, the vehicle may be
operated.
SERVICE BRAKES APPLYING — TRACTOR/
TRAILER COMBINATION
Brake application air enters the BP-R1 ™ valve service port
and is conducted through the service piston to the exhaust
diaphragm which
fl exes in response to the incoming air and
seals the exhaust passage in the exhaust piston. Air
fl ows
around the exhaust diaphragm then through the center of
both the blend back and proportioning pistons to the inlet
and exhaust valve. Flowing around the inlet valve, applica-
tion air moves through a passage in the cover to the top of
the service relay piston. In response to air pressure, the
relay piston moves into contact with the exhaust portion
DELIVERY
PORT
SPRING
BRAKE
REAR AXLE
SERVICE RESERVOIR
EARLIER
MODELS
HAVE A
DIAPHRAGM
HERE