TM 5-3805-262-20
PNEUMATIC SYSTEM,
Provides air pressure for parking and service brakes, hydraulic
r e s e r v o i r,
c l u t c h c u t - o u t,
low pressure warning buzzer, horn, windshield washer, and
air pressure gage. System operation is controlled by two brake treadle and valve
assemblies, washer control, and horn valve located on cab deck. Comprised of air
compressor assembly, brake actuators (described above), brake treadle and valve
assemblies, pressure protection valve, pressure reducing valve, washer control,
fluid reservoir, horn, and horn valve.
AIR COMPRESSOR.
Compressed air supplied by a two cylinder, reciprocating compressor
mounted on engine, right side. Driven by drive belt between air compressor pulley
and radiator fan cooling hub when engine operating. Governor mounted on rear of air
compressor and connected between air compressor and air reservoir to control com-
pression. Air compression starts when air reservoir pressure falls below 95 psi and
stops when pressure reaches a maximum of 122 psi. When air reservoir pressure
reaches maximum, governor routes air to unloader in compressor which stops compres-
s i o n . I f g o v e r n o r f a i l s t o o p e r a t e p r o p e r l y , s a f e t y v a l v e i n s t a l l e d i n a i r r e s e r v o ir
opens at 150 psi venting air to atmosphere preventing damage to system and possible
p e r s o n n e l i n j u r y. Input air drawn through air cleaner via air cleaner adapter mount-
ed on engine intake manifold.
AIR RESERVOIR.
Air from air compressor routed to, and stored in, air reservoir un-
til required by system components. Check valve installed at reservoir inlet prevents
compressed air from flowing back to air compressor. Drain valve installed in bottom
o f a i r r e s e r v o i r t o d r a i n w a t e r t h a t a c c u m u l a t e s d u e t o c o n d e n s a t i o n . A i r a c t u a t ed
s e n d i n g u n i t i n a i r r e s e r v o i r o u t l e t g e n e r a t e s a n e l e c t r i c a l s i g n a l f o r a i r p r e s s u re
gage mounted in instrument panel cluster.
BRAKE TREADLE AND VALVE.
Controls air flow to brake actuators. Incorporates a rub-
ber piston spring. Pressing on brake treadle compresses this spring; further pedal
is depressed, more spring resists. This feature allows more even control of air
pressure, assuring more accurate control of brake application. A combined check val-
ve and stop light switch prevents excessive air being applied to brake actuators and
t u r n s r e a r s t o p l i g h t s o n.
INCHING TREADLE AND VALVE.
Controls air flow to clutch cutout cylinder mounted on
transmission control valve. Inching treadle and valve same as brake treadle and val-
ve. Depressing this treadle disengages transmission during loader operation allows
operator to inch further from or closer to load.
BRAKE ACTUATORS.
See hydraulic brake system description on page 1-24 above for
d e s c r i p t i o n o f b r a k e a c t u a t o r s.
CLUTCH CUTOUT.
Used to disengage transmission during loader operation to inch load-
er closer to or further from load. When inching treadle depressed, compressed air
routed to cylinder in transmission control valve . Push rod in cylinder moves a spool
i n t r a n s m i s s i o n c o n t r o l v a l v e . S p o o l s t o p s f l o w o f o i l t o c l u t c h e s a n d r e l e a s e s
pressure in clutches so that transmission is in neutral. Allows effective way of
causing loader to inch forward other than using brake treadle.
AIR PRESSURE GAGE.
Mounted on instrument panel cluster. Green area of gage indi-
cates enough air pressure for safe operation of loader. Red area of gage indicates
there is insufficient air pressure for safe operation. Air system is at a maximum
pressure of 110 psi.
1-25
