Electronic vent valve

Details Electronic vent valve Electronic vent valve

1999-08-06

2002-11-05

Lavinder, Jack (Department: 3683)

Fluid-pressure and analogous brake systems

Releasing

Control pipe

C303S007000, C303S015000, C303S020000

Reexamination Certificate

active

06474748

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates, in general, to pneumatic braking systems such as are typically employed on rail transport vehicles (e.g., trains) and other relatively large wheeled transport vehicles (e.g., heavy trucks). More particularly, the present invention relates to a so-called “electronically controlled pneumatic” (hereinafter “ECP”) type of braking system for such vehicles, most particularly ECP braking systems for trains and other rail transport vehicles.
BACKGROUND OF THE INVENTION
The principles of a pneumatic braking system are well understood by those of ordinary skill in the relevant art. Typically, an onboard air compressor furnishes and replenishes as necessary compressed air to the system. A so-called “main reservoir” is typically employed to maintain a substantially constant feed pressure to the system downstream thereof. The main reservoir is recharged by the onboard compressor whenever its pressure drops below a predetermined level.
A train “consist” is formed of a number of related railcars linked end to end. The main reservoir, normally located in a forward locomotive along with the compressor, feeds a pneumatic line, commonly referred to as a “brake pipe” which typically extends the length of the train. In the formation of a train consist, the individual brake pipe sections located on each individual railcar are linked together through pneumatic couplings. On each individual railcar, a “branch pipe” supplies compressed air from the brake pipe running the length of the train to the individual braking components of the individual railcar, which typically include a so-called “AB-Type control valve” (also sometimes referred to as a “triple valve”), an “auxiliary reservoir”, an “emergency reservoir” and the brake cylinders of the railcar. [Examples of AB-Type control valves are the ABD, ABDX and ABDW control valves currently or previously manufactured by Westinghouse Air Brake Company, i.e., “WABCO”.] During times when the brakes are “released” (e.g., no braking force being applied), compressed air from the pneumatic brake pipe is supplied via the branch line to maintain a predetermined compressed air charge within the auxiliary and emergency reservoirs of each railcar in the train consist. In some designs, a so-called “combined auxiliary and emergency reservoir” is provided on a railcar. The brakes on an individual railcar are applied by supplying compressed air from at least the auxiliary/emergency reservoir(s) located on the railcar to the brake cylinders of the railcar. The compressed air displaces the pistons of the brake cylinders to apply a mechanical braking force to the wheels of the railcar.
In the conventional pneumatic braking system, as originally developed, the only means for actuating the transfer of compressed air from the auxiliary/emergency reservoir(s) to the brake cylinders is through the brake pipe itself. An engineer or other operator lowers the brake pipe pressure, e.g., by manipulating a brake lever on a brake control panel located in the locomotive. For example, the brake pipe pressure can be lowered by venting the brake pipe to atmosphere in response to movement of a control handle by the engineer.
The AB-Type control valves located on each individual railcar are constructed such that they respond to a lowered brake pipe pressure by supplying compressed air from at least the auxiliary reservoir located on each railcar to the brake cylinders of the railcar, thereby applying the brakes of the railcar. The amount of air pressure supplied from the auxiliary reservoir to the brake cylinders by the AB-Type control valves is proportional to the amount by which the brake pipe pressure is lowered by the engineer. Typically, the control handle allows the engineer to apply a continuously variable braking force beginning with a so-called “release” position (in which the brake pipe pressure is at a maximum and the braking pressure applied at the individual railcars is therefore at a minimum, e.g., the brakes are released), through a “minimum service” brake application, a “full service” brake application and ultimately to an “emergency” brake application (in which the brake pipe pressure is at a minimum and the braking pressure applied at the individual railcars is therefore at a maximum). Other braking applications may be available to the engineer such as suppression and continuous service, but the principle is basically the same, namely, that the engineer's movement of the braking control handle lowers the brake pipe pressure, and the AB-Type control valves located in the individual railcars respond by supplying air from the auxiliary/emergency reservoir(s) located on the individual railcars to the brake cylinders proportionately according to the degree by which the brake pipe pressure is lowered by the engineer.
When the engineer moves the control handle to the “emergency” position, the brake pipe pressure is precipitously reduced. As is well understood in the art, the individual AB-Type control valves on the individual railcars are constructed such that, when the brake pipe pressure drops below a determined pressure, the AB-Type control valves transfer compressed air from both the auxiliary and emergency reservoirs on each railcar to the brake cylinders of the railcar, resulting in a greater mechanical braking force being applied than in a service braking application, wherein only compressed air from the auxiliary reservoirs is supplied to the brake cylinders.
One advantage of the above-described conventional pneumatic braking system is that it provides a “fail safe” mechanism. Since the brakes at the individual railcars are applied in response to a decrease in brake pipe pressure, a rupture of the brake pipe, a failure of the compressor, etc. results in the brakes being applied and not in a brake failure. In view of the dire consequences of brake failure on a railway train, it is understandable that pneumatic braking development has been characterized by the fail safe concept.
However, a limitation of such a conventional pneumatic braking system described above that has been long appreciated is the delay in braking that occurs as the change in brake pipe pressure propagates along the length of a train. For example, it has been estimated that a brake pipe pressure drop in a freight train of approximately one mile in length may take about one minute to travel the length of the train if it is a service brake application and about one-half minute if it is an emergency brake application.
To overcome this limitation, so-called “electronically controlled pneumatic” (or “ECP”) braking systems have been developed. ECP braking systems also utilize the concept of control valves located on each railcar which transfer previously stored compressed air from auxiliary/emergency reservoir(s) located on the railcars to the brake cylinders thereof to generate a braking force. However, in an ECP braking system, the control valves can be electrically actuated (i.e., through electropneumatic valves). Therefore, signals to the railcar control valves are transmitted at least electrically, rather than only through the brake pipe pressure, thereby substantially eliminating the propagation delay along a long freight train mentioned above.
In a typical implementation of an ECP braking system on a freight train, the lead locomotive is provided with a master controller (e.g., microprocessor controlled) which receives input data signals describing the degree of braking application applied by the engineer via the brake control handle. The master controller then formulates braking commands for the railcars and sends electrical braking command signals to individual car control units or “CCU”s (e.g., also microprocessor controlled) located on each individual railcar which describe the degree of braking to be applied by each individual railcar. The electrical braking command signals sent by the master controller typically describe the braking application in terms of a percentage of the pressure required for a full service brake application

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