SERVICE MANUAL
Fig. 6 Brake Application, Loss of Air in Secondary
System
Fig. 7 Brake Application, Loss of Air In Primary System
1Primary Reservoir
2Secondary Reservoir
3Inlet & Exhaust A
4Piston A
5Piston B
6Check Valve
7Exhaust
8Inlet & Exhaust B
9Spring Brake Control Valve
10Double Check Valve
Brake Application with Loss of Air In Primary Sys-
tom (Fig. 7)
If air pressure in the primary reservoir should fall below
approximately 379 kPa (55 psi), the pressure below
piston "A" is insufficient to resist spring force above arid
piston "A" moves into contact with valve "A". Initial
contact between piston "A" and valve "A" closes the
hollow exhaust passage of piston "A". Continued
movement of piston opens the inlet valve "A".
The secondary reservoir and spring brake control valve
is protected from air pressure loss by action of check
valve.
When brake application is made through the brake valve,
air delivered from the secondary system of the brake
valve enters the inversion valve control port. Air enters
control port, moves past the inlet of valve "A" and is
conducted through a passage in the body to the
underside of piston "B." The added force of air pressure
below piston "B" moves up, opening the exhaust valve
"B." When exhaust of valve "B" opens, air pressure
trapped in the emergency section of the spring brake
chamber is allowed to escape resulting in a brake
application by emergency section. The amount of air
pressure released from spring brake is proportional to
the amount of air pressure delivered to the control port of
the inversion valve by delivery of brake valve secondary
system.
Parking (Spring) Brake Application (Fig. 8)
When both primary and secondary systems are charged
with air and spring brake control valve is placed in
"apply" or exhaust position, the inversion valve air supply
and air pressure in the spring brake chambers will be
exhausted. The single check valve in the inversion valve
assists the exhaust of air from the spring brake by
allowing air below piston "B" to flow back out the open
exhaust of spring brake control valve.
When air pressure below piston "B" has dropped
enough, piston "B" moves down opening the inlet of
valve "B" thus providing an additional exhaust passage
for air exhausting through the inversion valve from spring
brakes.
Fig. 8 Parking Broke Application
1Primary Reservoir
2Secondary Reservoir
3Inlet & Exhaust A
4Piston A
5Piston B
6Check Valve
7Exhaust
8Inlet & Exhaust B
9Spring Brake Control Valve
10Double Check Valve
CTS-4079 - CHAPTER VII - Page 5
