Operation; Initial Charging; Service Brakes Applying—Tractor/Trailer Combination; Bp-R1 Tractor Air System And Bobtail Proportioning Relay Valve - BENDIX BP-R1 BOBTAIL PROP RELAY VALVE Manual

TRAILER
SUPPLY
SERVICE PORT
CONTROL
DUAL
BRAKE
VALVE
REAR AXLE
SERVICE RESERVOIR
™
FIGURE 2 - BP-R1 TRACTOR AIR SYSTEM

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
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
2
TRACTOR
PROTECTION
BP-R1
™
VALVE
DELIVERY
PORT(4)
PORT
SUPPLY
SERVICE
SPRING
BRAKE
™ valve service port
CONTROL
PORT
PROPORTIONING
PISTON
INLET-EXHAUST
VALVE
SPRING
(NOT USED
IN ALL
MODELS)
SUPPLY
PORT
™
FIGURE 3 - BP-R1
VALVE
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
ports to the brake actuators. (See Figure 4.)
™
INLET-EXHAUST
VALVE
FIGURE 4 - BP-R1 ™
COMBINATION
"BLEND BACK"
SERVICE
PISTON
PORT
INLET-EXHAUST
VALVE
BOBTAIL PROPORTIONING RELAY
™
PROP
PISTON
INLET-EXHAUST
PISTON
APPLYING - TRACTOR/TRAILER
SERVICE
PISTON
EARLIER
MODELS HAVE
A DIAPHRAGM
HERE
SPRING
RELAY
PISTON
DELIVERY
PORT
valve delivery
RELAY
PISTON