User Manual

3
Bendix
OPERATION - CHARGING SPRING BRAKE
ACTUATORS (FIGURE 3)
Air pressure used to control the spring brake actuators
enters the Bendix
®
R‑7
™
modulating valve through the
supply port, passing through one side of the double check
valve, through the open inlet valve, over the balance piston,
and out the delivery ports to the spring brake actuators.
When air pressure in the spring brake actuator cavity has
released the spring brake actuators—and when air pressure
on top of the balance piston is sufcient to overcome the
force of the balance piston spring—the balance piston
moves, allowing the inlet valve spring to close the inlet
valve. This in turn, shuts off further air pressure from the
reservoir supplying the modulating valve.
FIGURE 3A - CHARGING ‑ PARKING BRAKE SUPPLY LESS
THAN BALANCE PISTON SETTING
FIGURE 3 - TYPICAL SYSTEM SCHEMATIC
COMPRESSOR
BRAKE
VALVE
AIR
DRYER
SLACK
ADJUSTER
QUICK
RELEASE
VALVE
ANTILOCK
MODULATOR
- 4 PLACES
RELAY
VALVE
RELAY
VALVE
BRAKE
CHAMBER
PARK CONTROL
VALVE
R-7
™
MODULATING
VALVE
SUPPLY
FRONT AXLE
REAR AXLE
FIGURE 3B - CHARGING ‑ PARKING BRAKE SUPPLY EQUAL
TO OR GREATER THAN BALANCE PISTON SETTING