TM9-2330-374-14&P
Internal
Brakes.
d.
(1) T h e i n t e r n a l b r a k e s a r e l o c a t e d w i t h i n t h e b r a k e d r u m s . E a c h i n t e r n a l
The outer surfaces of the
b r a k e s h o e s a r e f i t t e d w i t h b r a k e l i n i n g s . E a c h shoe is anchored at one
e n d o n a n a n c h o r p i n o n w h i c h i t p i v o t s . T h e other end of each shoe is
free to be pushed out or pulled.
( 2 ) A n S-shaped cam (2) on the end of the camshaft is mounted between the free
R o t a t i o n of the cam (2) forces the shoes (1) o u t
ends of the two shoes (1).
causing the brake linings to contact the drum.
(3) A b r a k e s h o e t e n s i o n s p r i n g ( 3 ) , n e a r t h e f r e e e n d s o f t h e b r a k e s h o e s ,
r e t r a c t s the brake shoes (1) from the drum and holds them in a retracted
position until the brakes are applied.
Internal
brakes
e. Slack Adjusters. The slack adjusters (1, figure 4-24) are levers mounted on
the brake camshafts (2).
Push rods (3) of the air chambers (4) operate the slack
adjusters (1) which in turn rotate the camshafts (2) causing the cams to press the
f . A i r Brake Chamber. T h e air brake chambers (4, figure 4-24) are mounted
adjacent to the internal wheel brakes. The air brake chambers convert air pressure
i n t o m e c h a n i c a l m o t i o n t o o p e r a t e t h e s l a c k a d j u s t e r s w h e n a p p l y i n g b r a k e s . The
spring in the air brake chamber may be caged in case of air loss or brake failure to
move the semitrailer.
g . Service Air Line. The service air line (7, figure
e x t e n d s from the air hose coupling (tagged SERVICE), on
the right side of the front
crossmember, along the right frame rail to the emergency
Its purpose
is to transmit changes in air pressure originated in the
towing vehicle, which
causes the emergency relay valve to function.
4-45