BENDIX M-21-M-22 ANTILOCK MOD ASSY Wartungshandbuch PDF herunterladen (Seite 9)

Check Valve

The in-line check valve is a device placed in an air line to allow air flow in one direc-

tion only, and to prevent flow of air in the reverse direction. An arrow indicating the

direction of air flow is cast into the body of the valve.

OPERATION: Air flow in the normal direction moves the check valve disc from its

seat, and the flow is unobstructed. Flow in the reverse direction is prevented by

the seating of the disc, which is caused by a drop in upstream air pressure and

assisted by the spring.

Brake Valve (treadle)

The Dual Brake valve (E6) is a floor-mounted, treadle-operated type brake valve. Two

separate supply and delivery circuits, for service and secondary braking, provide the

driver with graduated control for applying and releasing the vehicle brakes.

The circuits in the E-6 dual brake valve are identified as follows: The No. 1 circuit portion

is that portion of the valve between the spring seat which contacts the plunger and

the relay piston; the No. 2 circuit portion is that portion between the relay piston and

the exhaust cavity. See figure x.

The No. 1 circuit portion of the valve is similar in operation to a standard single-circuit

air brake valve, and under normal operating conditions the No. 2 portion is similar in

operation to a relay valve.

Both No. 1 and No. 2 circuit portions of the brake valve use a common exhaust protect-

ed by an exhaust diaphragm.

OPERATION

Applying: Normal Operation—No. 2 circuit portion

When the No. 1 inlet valve is moved off its seat, air is permitted to pass through the

bleed passage and enters the relay piston cavity. The air pressure moves the relay pis-

ton, which contains the exhaust seat and closes the No. 2 exhaust valve. As the No. 2

exhaust valve closes, the No. 2 inlet valve is moved off its seat, allowing the No. 2 air

to flow out the No. 2 delivery port. Because of the small volume of air required to

move the relay piston, action of the No. 2 circuit portion of the valve is almost simulta-

neous with the No. 1 circuit portion.

Applying: loss of air in the No. 2 Circuit

Should air be lost in the No. 1 circuit, the function will be as follows: As the brake trea-

dle is depressed and no air pressure is present in the No. 1 circuit supply and delivery

ports, the No. 1 piston will mechanically move the relay piston, allowing the piston to

close the No. 2 exhaust valve and open the No. 2 inlet valve and allow air to flow out

the No. 2 delivery port.

Balanced: No.1 Circuit portion

When the No. 1 delivery pressure acting on the piston equals the mechanical force of

the brake pedal application, the No. 1 piston will move and the No. 1 inlet valve will

close, stopping the further flow of air from the No. 1 supply line through the valve. The

exhaust valve remains closed, preventing any escape of air through the exhaust port.

Air Brake System

Revised 11/15/99

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 31 32

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