Bendix Commercial Vehicle Systems AUTO SLACK ADJUSTER SERVICE MANUAL - Manual (Page 4)

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Introduction
Spicer ® brand self adjusting brake adjusters compensate for wear in
brake shoe linings caused by normal braking operation. Upon
brake application, the brake adjuster assembly rotates, rotating
the brake camshaft. The camshaft moves the shoes into contact
with the drum.
During brake application and release, the adjuster mechanism
rotates the camshaft slightly to maintain the correct shoe-to-
drum clearance.
Operation
The Spicer ® brand self adjusting brake adjuster is a clearance sensing
brake adjuster that maintains a nominal distance or clearance
between lining and drum. The clearance notch in the rack
corresponds to this normal lining-to-drum clearance. (See
Figure 1.)
When the brake applies:
• The rack moves upward and rotates the one-way clutch.
The one-way clutch allows slippage in this direction.
• Brake application torque presses the wormshaft against
the coil spring. Wormshaft movement releases the cone
clutch.
When the brake releases:
• The coil spring presses against the wormshaft, engaging
the cone clutch.
• The rack is pulled back to its original position in the
clearance notch.
• Any lining wear causes the rack to turn the locked one-
way clutch while rotating the wormshaft via the locked
cone clutch.
• The wormshaft rotates the wormwheel and camshaft,
adjusting the brakes.
NOTE: A properly working Automatic Slack Adjuster does not
require manual adjustment while in service. The manual adjuster
hex is intended for use during adjuster installation and brake
overhaul.
WARNING: Automatic slack adjusters should not be repeatedly
adjusted to correct excessive in service pushrod stroke, because
this condition indicates that a problem exists with the automatic
adjuster, with the installation of the adjuster or with related
foundation brake components which manual adjustment will not
correct.
Figure 1 Components of the Brake Adjuster
Introduction/Operation
ONE-WAY
CLUTCH
CONE
CLUTCH
RACK
CLEARANCE
NOTCH
WORMSHAFT
COIL
SPRING
CONTROL ARM
ANCHOR BRACKET
CONTROL
ARM