[Illustration: Fig. 11. Emergency Position of No. 6 Distributing
Valve with Quick-Action Cap.]
A. In an emergency application, the equalizing piston 26 moves to the
extreme right, the knob on the piston strikes the graduating stem 59,
causing it to compress the graduating spring 46, and move the slide
valve 48 to the right, opening port "j".
[Illustration: Fig. 12. Independent Application.]
Brake pipe pressure in chamber "p" flows to chamber "X", pushes down
check valve 53, and passes to the brake cylinders through port "m" in
the cap and distributing valve body. When the brake cylinders and brake
pipe pressures equalize, check valve 53 is forced to its seat by spring
54, thus preventing air in the brake cylinders from flowing back into
the brake pipe. When a release of the brake occurs and piston 26 is
moved back to its normal position, spring 46 forces graduating stem 59
and slide valve 48 back to release position.
139. Q. Explain the operation of the distributing valve when making an
independent application of the brake.
A. When the independent brake valve handle is moved to application
position, air is admitted from the reducing valve pipe through the
application cylinder pipe to the application chamber and cylinder.
Pressure forming in the application cylinder will move the application
piston 10 to the right, carrying with it the exhaust valve 16 and the
application valve 5, closing the exhaust port and opening the supply
port, admitting main reservoir air from chamber "a" to the brake
cylinders (see Fig. 12) until the pressure in the brake cylinders and
chamber "b" slightly exceeds that in chamber "g", when the application
piston 10 and valve 5 will move back to lap position. By moving the
brake valve handle to either release or running position, the air is
exhausted from the application cylinder and chamber, thus reducing the
pressure in chamber "g", allowing the pressure in chamber "b" to force
the piston to the left, carrying with it the exhaust valve 16, opening
the exhaust ports "e" and "d", allowing the air from the brake cylinders
to escape to the atmosphere, thus releasing the brake.