Fluid-pressure and analogous brake systems – Releasing – Control pipe
Reexamination Certificate
2003-02-10
2004-11-30
Lavinder, Jack (Department: 3683)
Fluid-pressure and analogous brake systems
Releasing
Control pipe
C303S007000, C303S015000, C303S067000
Reexamination Certificate
active
06824226
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to pneumatic braking systems and more particularly to a pneumatic braking system for a train consist comprising a lead locomotive and one or more remote locomotives.
BACKGROUND OF THE INVENTION
One of the most critical aspects of the operation of railroad vehicles is the predictable and successful operation of the air brake system. However the air brake system is subjected to a variety of dynamic effects, not only as a result of the controlled application and release of the brakes in response to changes in brake pipe pressure, but also due to the varying operating conditions encountered by the train. Thus multiple operating scenarios must be considered for the successful design and operation of the air brake system.
At each railcar, a control valve (typically comprising a plurality of valves and interconnecting piping) responds to locomotive operator-initiated changes in the brake pipe fluid pressure by applying the brakes (in response to a decrease in the brake pipe fluid pressure) or by releasing the brakes (in response to an increase in the brake pipe fluid pressure). The fluid within the brake pipe conventionally comprises pressurized air. The control valve at each railcar senses the drop in brake pipe air pressure as the pressure drop propagates along the brake pipe. In response, at each railcar pressurized air is supplied from a local railcar reservoir to the wheel brake cylinders, which in turn drive the brake shoes against the railcar wheels. The railcar reservoir is charged by supplying air from the brake pipe during non-braking intervals. Typically, the pressure reduction in the brake pipe for signaling a brake application is about seven to twenty-four psi, with a nominal steady state brake pipe pressure of about 90 psi. The braking pressure applied to the railcar wheels is proportional to the drop in the brake pipe pressure. Thus it can be seen that the brake pipe serves to both supply pressurized air to each railcar for powering the brake shoes during a brake application and also serves as the medium for communicating brake application and release instructions to each railcar.
The railcar brakes can be applied in two different modes, i.e., a service brake application or an emergency brake application. A service brake application involves the application of braking forces to the railcar to slow the train or bring it to a stop at a forward location along the track. During service brake applications the brake pipe pressure is slowly reduced and the brakes are applied gradually in response thereto. An emergency brake application commands an immediate application of the railcar brakes through an immediate evacuation or venting of the brake pipe. Unfortunately, because the brake pipe runs for several thousand yards along the length of the train, the emergency braking evacuation does not occur instantaneously along the entire length of the brake pipe. Thus the braking forces are not uniformly applied at each railcar to stop the train.
After one emergency brake application or two or three service brake applications, the brake pipe must be recharged to its nominal operating pressure by supplying pressurized air from a reservoir on the locomotive into the brake pipe. Effective subsequent brake applications cannot be made until the recharging process has been completed.
FIG. 1
illustrates a typical prior art brake system employed by a railway freight train. In a conventional train having only a lead locomotive, the train brake system comprises a locomotive brake system located on a locomotive
100
and a set of railcar brake systems located on a plurality of railcars illustrated by a railcar
200
. The application and release of braking action is controlled by an operator within the locomotive
100
, who uses a manually operated brake handle to effect braking action. The locomotive includes an air brake control system
102
for supplying air pressure to or controllably venting a pressurized brake pipe
101
via a brake pipe valve
120
. The pressurized brake pipe
101
is in fluid communication with each of the railcars
200
of the train as shown.
The locomotive brake control system
102
comprises an air supply input link
111
for supplying pressurized fluid (air) through which the brake pipe
101
is charged. A flow measuring adapter
113
is connected to the air supply link
111
for measuring the charging rate (as a differential pressure between the air supply an output port
116
) of the brake control system
102
. The output port
116
of the flow measuring adapter
113
is connected to an input port
121
of a relay valve
117
. A bi-directional port
122
of the relay valve
121
is coupled to the brake pipe
101
. The relay valve
117
further includes a port
123
coupled through an air pressure control link
103
to an equalizing reservoir
105
. The pressure control link
103
is also connected to a pressure control valve
107
through which the equalizing reservoir
105
is charged and discharged in the process of a brake operation. A port
124
of the relay valve
117
is controllably vented to the atmosphere as an exhaust port. Coupled with brake pipe
101
and air pressure control link
103
are respective pressure measuring and display devices
131
and
133
. The brake pipe gauge
131
measures the air pressure in the brake pipe
101
and the equalizing reservoir gauge
133
measures-the pressure in the equalizing reservoir
105
.
The components of a railcar air brake control system
202
, include a control valve
203
having a port
221
coupled to the brake pipe
101
. The control valve
203
also includes a port
222
coupled to a pressure storage and reference reservoir
205
. Finally, the control valve
203
includes a port
223
coupled to an air brake cylinder
231
, comprising a piston
232
connected to a brake shoe
233
. An increase in air pressure at the port
223
is fluidly communicated to the piston
232
for driving the brake shoe
233
against the wheels
235
of the railcar
200
. Thus the air brake control system
102
of the locomotive
100
controls operation of the pneumatically operated brake shoes
233
at each of the wheels
235
of each railcar
200
.
During train operation, the brake pipe valve
120
, through which the components of the brake control system
102
are coupled to the brake pipe
101
, is open to create a continuous brake pipe fluid path between the locomotive
100
and all of the railcars
200
of the train. The brake pipe valve
120
is controlled by a brake valve cut-out valve
250
, that is in turn controlled by a pilot valve
251
. The pilot valve
251
can be manually operated by the locomotive operator to close the brake pipe valve
120
when it is desired to terminate brake pipe charging or to disconnect the brake pipe
101
from the locomotive brake control system
102
. There are also other valves and control components (not shown in
FIG. 1
) that automatically terminate brake pipe charging during an emergency brake application by closing the brake pipe valve
120
. Each railcar
200
also includes a manually-operated brake pipe valve
240
, as shown in FIG.
1
.
The brake system is initially pressurized by the operation of the pressure control valve
107
, which controls the air supply to the control link
103
to charge the equalizing reservoir
105
to a predetermined pressure. The relay valve
117
is then operated to couple port
121
with the port
122
so that air is supplied there through to the brake pipe
101
, charging the brake pipe
101
to the predetermined charge pressure, as established by the pressure of the equalizing reservoir
105
. When the brake pipe pressure reaches the predetermined pressure, the pressure at the port
122
(connected to the brake pipe
101
) equals the pressure at the port
123
(connected to the equalizing reservoir
105
). This condition indicates a charged brake pipe and the fluid flow path from the equalizing reservoir
105
to the brake pipe
101
via the relay valve
117
is closed.
The pressure storag
Kiss, Jr. James M.
Palanti Robert C.
Smith, Jr. Eugene A.
Beusse Brownlee Wolter Mora & Maire P.A.
DeAngelis Jr. John L.
General Electric Company
Lavinder Jack
Rowold Carl A.
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