Cadillac 1933 V8 Operator's Manual page 201

8
Cadillac 355-C, 370-C, 452-C—LaSalle 345-C
Fig. 10. Sectional views of brake assister used on 345-C
and 355-C cars
develops power only as long as the driver continues
to push on the pedal. As soon as the driver stops
pushing on the pedal, the assister ceases to build up
additional force and merely holds the position which
has been reached. The assister releases automatically
when the driver releases his foot from the pedal.
The relative position of the brake assister parts is
shown in Fig. 10. The piston divides the housing
into two chambers; the front or atmospheric chamber
which is open to the rear chamber when the brakes
are not in operation, and the rear or vacuum chamber
which is connected to the intake manifold vacuum
line. The assister operating tube carries an inner rod
which operates the vacuum and atmospheric valve
located in the rear end of the operating tube. The
operating tube, of course, also connects the piston
mechanism to the pedal lever.
Fig. 11. Brake assister in normal released position.
The vacuum and atmospheric valve is all the way
forward uncovering the passage in the operating tube
and opening the front chamber to the intake vacuum
line through the rear chamber
The vacuum and atmospheric valve is of the piston
type and controls the vacuum passage between the
two chambers in the cylinder and the passage between
the front chamber and the atmosphere outside of the
cylinder. The valve is held in the closed position by
means of a spring as shown in Fig. 10. When the
valve is moved part of the way back toward the rear
it closes the vacuum passage between the two cham-
bers in the cylinder, and when moved all the way
back, the valve keeps the vacuum passage closed and
opens the front chamber to the atmosphere. The air
entering the cylinder passes through a chamber filled
with hair (Fig. 10) which serves as an air cleaner to
exclude dus"t and dirt.
The construction of the pedal lever assembly is the
same as that used on the V-12 and V-16 cars and the
adjustments are made in identically the same manner.
Fig. 12. The brake pedal has been depressed sufficiently
to move the valve back far enough to close the passage
between the front and rear chambers. The assister
cannot function even though the passage between the
two cylinders is closed as the front chamber is not yet
open to the atmosphere
Assister Operation: The various steps in the operation
of the vacuum brake assister are shown in Figs. 11 to
16 inclusive.
In Fig. 11, the brakes are in the released position.
It will be seen that the valve rod and valve are all the
way forward with relation to the piston. With the
valve in this closed position, the passage between the
two cylinder chambers is open and the atmospheric
passage is closed. Both chambers are now connected
to the intake manifold and the vacuum on both sides
of the piston is equal.