SERVICE MANUAL
Fig. 1 - Double Diaphragm Spring rake Chamber
1 Push Rod
2 Service Brake Chamber
3 Spring Brake Chamber
4 Spring Brake Push Rod Assembly
5 Parking Brake Spring
6 Breather Cap
7 Release Bolt
8 Push Rod spring
DESCRIPTION
The double diaphragm spring brake chamber
assembly consists of a tandem-type cylinder assembly
connected to the foundation brake group either through
the air brake slack adjuster or wedge assembly.
The cylinder assembly consists of two basic sections.
One section is a conventional service brake chamber
while the second section is the spring (parking) brake
chamber. The spring brake chamber contains a
powerful spring which is completely compressed by air
pressure in normal driving mode.
OPERATION
NORMAL DRIVING
In normal operation with the parking brake released (Fig.
2) the spring brake control valve on the instrument panel
must be in the released position. When the control valve
is in the released position, air pressure is permitted to
pass through the control valve and provide the spring
brake chambers with air, thereby loading the spring
brake chamber and compressing the parking brake
spring, holding the rear wheel brakes in the released
position.
Fig. 2 - Normal Driving Position
SERVICE BRAKE APPLICATION
When the service brakes are applied, air is forced into
the service brake chamber (Fig. 3) forcing the pushrod
and piston assembly outward, extending the pushrod
assembly.
Fig. 3 - Service Brake Application
When the brake (foot) valve is released, air in the service
brake system is exhausted and the service brake
chamber
pushrod
assembly
and
diaphragm
are
permitted to return to the normal released position. The
pushrod sprirg assists in this function by forcing the
pushrod and plate assembly into the normal released
position.
CTS-4101W - Page 3
