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| Illustration 1 | g00693416 |
(1) Relay valve (tractor) (2) Brake actuator (left side of tractor) | |
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| Illustration 2 | g00693417 |
(3) Relay valve (scraper) (4) Air tank (scraper) | |
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| Illustration 3 | g00701045 |
Relay valve (5) Diaphragm assembly (6) Control passage (7) Valve passage (8) Delivery passage (9) Valve (10) Supply passage (11) Valve (12) Spring (13) Exhaust passage | |
Supply passage (10) is connected to the air tank. Spring (12) holds valve (9) seated in order to stop the flow of air to delivery passage (8) .
When air pressure is sent to control passage (6), diaphragm assembly (5) will be forced down. As diaphragm assembly (5) moves down, valve (11) makes contact with valve (9). This closes the exhaust passage inside valve (9). Diaphragm assembly (5) will push valve (9) downward. This will open a passage so that air from supply passage (10) will go through the valve and out delivery passage (8) to the brake actuators.
When the air pressure to control passage (6) is released, spring (12) will push valve (9) upward. This will stop the flow of air pressure through supply passage (10). Air pressure in delivery passage (8) will push diaphragm assembly (5) upward against the cover of the valve. Valve (11) will move away from valve (9), which will open a passage through valve (9). Thus, the air pressure can go out through exhaust passage (13).