2.1.2.3 When the application valve is opened by the upward
movement of the service valve stem, auxiliary (supply)
or main reservoir air flows into Passage 16a and to the
following passages and chambers:
2.1.2.3.1 To Port 16 in the pipe bracket which is connected
to the brake cylinder application pipe or brake cylinder relay
valve control pipe.
2.1.2.3.2 To the face of the charging valve diaphragm initiating
a movement of the charging valve spool that cuts off
the exhaust of brake pipe air from the quick service volume.
This movement serves to terminate quick service action of
the Control Valve.
2.1.2.3.3 To the large spring chamber in the service valve.
The force of this pressure, combined with the force of the
spring and coupled with the force of the brake pipe pressure
in the chamber above the large diaphragm, oppose
the force of the control reservoir air pressure in the chamber
under the large diaphragm. Whenever the point of
equalization of forces across the diaphragm is reached,
the service valve will assume a lap position.
2.1.2.3.4 To the underside of the service limiting valve.
Whenever this air pressure increases to a point in slight
excess of the force of the spring, the spool valve will move
upward and cut off any further flow of air into Passage 16.
The predetermined setting of the spring is intended to limit
the maximum pressure delivered to the brake cylinder application
pipe or brake cylinder relay valve control pipe during
a service application.
2.1.2.4 Whenever a manual adjustment has been made at
the Brake Valve on the controlling vehicle to permit a higher
brake pipe pressure, it is possible to get over-reductions
with the “26-C” Control Valve. Over-reductions should not
have any effect on brake cylinder application pipe pressure,
since this pressure is predetermined by the load settings
of the springs within the limiting valves.
2.1.2.5 An over-charge in the control and selector volume
reservoirs can be reduced to brake pipe pressure by manually
moving the automatic brake valve handle on the controlling
vehicle alternately between Application and Release
positions. During application, selector volume air flows to
exhaust via the selector spool valve, and, during release,
the control reservoir air is free to flow to the selector volume
passage in the selector spool chamber. Several applications
and releases may be required, depending upon the
severity of the over-charge. Whenever the release cap is
manually set in Direct Release, control reservoir air may
also flow into brake pipe through Choke J as well as through