When compressed air is delivered from the brake valve to port a, rubber diaphragm 1 is raised and the air is directed through ports d and b to the brake chambers. At the same time, diaphragm 1 closes off air discharge to the atmosphere. When braking has been completed, the pressure under diaphragm 1 drops rapidly and the diaphragm is bent downward by the pressure of the air in the brake chambers and by spring 2. This closes port a and opens port f, allowing the air to escape to the atmosphere, by-passing the brake valve. As a result, the brakes are more rapidly released.
$4045$EHP,Va$