TM 5-3805-258-24-1
A I R S Y S T E M A N D B R A K E S
A I R C I R C U I T F O R T H E
W H E E L B R A K ES
BRAKE CONTROL VALVES
There are two brake control valves. Each valve is
fastened directly under a pedal that is operated by
the operator’s left and right feet.
L O C A T I O N O F T H E B R A K E P E D A L S
1. Left pedal. 2. Right pedal.
When left pedal (1) is pushed, air goes in two
directions. It goes to the transmission neutralizer
valve and causes the transmission to disengage.
It also goes through orifice check valve (5), double
check valve (6) and on the air cylinders to engage
the wheel brakes.
L O C A T I O N O F B R A K E C O N T R O L V A L V ES
3. Brake control valve for left pedal. 4. Brake control valve
for right pedal. 5. Orifice check valve. 6. Double check
valve.
When right pedal (2) is pushed, air goes through
double check valve (6) and directly to the air cyl-
inders.
S Y S T E M S O P E R A T I O N
Operation
BRAKE CONTROL VALVE (Brakea Releeaed)
7. Seet. 8. Rubber spring. 9. Piston. 10. Retainer. 11. Out-
let passage. 12. Spring. 13. Valve. 14. Valve body. 15.
Spring. 16. Exhaust paasage. 17. Inlet paasage. 18. Ex-
haust diaphragm.
When a brake pedal is pushed, a force is put on
seat (7). This force pushes rubber spring (8) and
piston (9) down. Piston (9) comes in contact with
valve (13) and closes exhaust passage (16). Further
movement of the pedal causes piston (9) to move
valve ( 13) down, away from its seat in valve body
(14). Pressure air is now free to go from inlet passage
(17) to outlet passage (11).
When the force of spring (15) becomes more than
the force of spring (12), piston (9) lifts enough to let
valve (13) come in contact with valve body (14)
again. This stops the flow of air through outlet pas-
sage (11). Piston (9) is still against valve (13), so
exhaust passage (16) is closed. The control valve is
now in balance and air pressure is held in the system.
If the pedal is lifted a small amount, the force
above piston (9) is less. The force of spring (12) will
lift the piston off of valve (13). Pressure air in the
system goes around piston (9) through exhaust pas-
3-80
