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PART 2-2
BRAKE SYSTEM
2-7
lever
can move upward
far
enough,
it
passes
over
the
end of
the tooth
and
engages
the
tooth.
When
the
brakes
are
released,
the
adjusting
spring
pulls
the
lever
downward
causing
the
star
wheel
to turn
and
expand
the
shoes.
The
star wheel
is
turned
one
tooth
at
a
time
as
the
linings
progressively
wear.
With
the
car
moving forward
and
the
brakes
applied,
the
secondary
shoe
is
against
the
anchor
pin
and
the
primary
shoe
is
moved
toward
the
drum.
Therefore,
the
adjuster
does
not operate.
The
rear
brake assembly
is
basi
cally
the
same
as
the
front
brake.
The
conventional
parking
brake
lever, link,
and
spring
are
used
in
the
rear
brake.
The
anchor pins on all
brakes
are
fixed
and non-adjustable.
BOOSTER
SYSTEM
The
power
brake booster is in
stalled
on
the
engine
side
of
the
dash
panel
and
is
connected
to the
brake
pedal
through
a
lever
assem
bly
and
push
rod
link.
The booster
consists of a
vacuum
chamber,
atmospheric
valve,
con
trol
valve
plunger
assembly,
dia
phragm
and
an
atmospheric
cham
ber.
Atmospheric
pressure
is
present
at
all
times
in
the
atmospheric
chamber
at
the
front
side
of
the
atmospheric
valve.
The
air
intake
to the
atmospheric
chamber
is
pro
tected
by
an
air
filter. The
atmos
pheric
chamber
is
separated
from
the
vacuum
chamber
by
the
bellows
assembly
within
the
vacuum
cham
ber.
Vacuum
is
present at all
times
in
that
area
of
the
vacuum
chamber
forward
of
the
diaphragm. Vacuum
is
supplied
through
a
hose from
the
intake
manifold
to the
vacuum mani
fold
and check valve on
the
booster
body. With
this
integral
check valve
and
vacuum
chamber,
it is
possible
to
obtain
several
power
assisted
brake
applications
with
the
engine
shut
off.
This
arrangement
makes a
vacuum
reservoir
unnecessary.
Either
vacuum
from
the
forward
side
of
the
diaphragm
or
air
from
the
bellows (atmospheric
chamber)
can
be
connected
to
the
rear side of
the
diaphragm
through
porting
in
the
control
valve
hub
and
the
plunger
assembly.
VACUUM SOURCE
CHECK VALVE
ATMOSPHERIC
SOURCE'
VACUUM PORT
CLOSED
BRAKE PEDAL
VACUUM
ATMOSPHERIC
PRESSURE
FIG. 2-Booster
in Applied Position
APPLYING POSITION
As
the
brake
pedal
is
depressed,
the
valve
operating
rod
and
valve
plunger
assembly
move
forward
compressing
the
plunger
return
spring
(Fig.
2).
The initial
move
ment of
the
plunger closes
the
port
ing
from
the
vacuum
chamber
pre
venting
further
evacuation
of
the
area
back
of
the
diaphragm.
Fur
ther
movement of
the
plunger
forces
the
atmospheric
valve
off
its
seat so
that
atmospheric
pressure
from
the
bellows
can
enter
the
hub
porting
that
leads
to
the
rear
side
of
the
diaphragm.
With
vacuum
on
the
front
side
of
the
diaphragm
and
atmospheric
pressure
on
the
back
side
of
the
diaphragm,
a
force is
developed
to
H1205-A
move
the
diaphragm,
push
rod
and
master
cylinder
piston
forward
to
close
the
compensating
port
and
force hydraulic fluid
under
pressure
through the
residual
pressure
check
valve
and
brake
tubes to the
wheel
brakes. As hydraulic
pressure
is
de
veloped
in
the
hydraulic
system,
a
reaction
counter-force
acts
against
the
reaction
lever
and
ring
assem
bly.
This
reaction
lever
and
ring
assembly
is designed
to transmit the
reaction
forces
back
through
the
actuating
control
valve
assembly
to
the
brake
pedal
and
provide
the
driver
with
a
resistance
that
is in
proportion
to
the
brake
hydraulic
apply
forces. This
is
the
means
of
providing
the
proper
"driver
feel"
to the
power
brake
unit.
VACUUM SOURCE
--iHr^r
ATMOSPHERIC
SOURCE
VACUUM
PORT OPEN
P]
VACUUM
f^?]
ATMOSPHERIC PRESSURE
FIG. 3-Booster
in
Holding
Position
BRAKE
PEDAL
H1206-A
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