WO2001010695A1

WO2001010695A1 - Eot service brake assist without radio communications

Info

Publication number: WO2001010695A1
Application number: PCT/US1999/017896
Authority: WO
Inventors: Angel P. Bezos
Original assignee: Westinghouse Air Brake Company
Priority date: 1999-08-06
Filing date: 1999-08-06
Publication date: 2001-02-15
Also published as: EP1226057A4; EP1226057A1

Abstract

An apparatus and method assists a brake control system in applying the service brakes on a European freight train. The apparatus (60) includes a transducer (61), a valve (62), a flow meter (64) and a microprocessor (63). Transducer (61) measures pressure in the rear of the brake pipe. When opened, valve (62) exhausts air from the rear of the brake pipe. Flow meter (64) measures the rate at which air exhausts from valve (62). Microprocessor (63) controls valve (62) in response to the pressure and flow rate readings. When a quick service pulse is detected, microprocessor (63) opens valve (62) thereby allowing air to exhaust to the atmosphere. Using flow rate readings, microprocessor (63) calculates regularly the actual quantity of air exhausted thus far.

Description

EOT SERVICE BRAKE ASSIST WITHOUT RADIO COMMUNICATIONS

FIELD OF THE INVENTION

The invention generally relates to a freight train of the type whose brake equipment allows a graduated release and application of the brakes. More particularly, the invention pertains to a novel system and method by which an apparatus, connected to the brake pipe at the end of the freight train, can be used to assist the brake control system in the lead locomotive in applying the brakes of the train. BACKGROUND OF THE INVENTION

The following background information is provided to assist the reader to understand the environment in which the invention will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.

In a freight train, a pneumatic trainline known as the "brake pipe" is the means by which service and emergency brake commands are conveyed from the conventional brake control system in the locomotive to each of the railcars in the train. As shown in Figure 1, the brake pipe 4 is essentially one long continuous tube that runs from the lead locomotive 2 to the last railcar 3 in the train 1. The brake pipe 4 is actually composed of a series of interconnected pipes 4a, with one pipe 4a secured to the underside of each railcar. As shown in Figure 2, the brake pipe 4 is formed by connecting each pipe 4a via a coupler to another such pipe length on an adjacent railcar.

It is well known that each of the interconnected pipes 4a that comprise the brake pipe 4 share a common, known diameter. The length of the train will also always be a known value. The volume of the brake pipe 4 on the train can thus be easily determined to a high degree of accuracy. As shown in Figure 2, it is to this brake pipe 4 that the pneumatic brake equipment on each railcar 3 connects via a branch pipe 8. The pneumatic brake equipment on each railcar typically includes two storage reservoirs 9 & 10, one or more brake cylinders 11 and at least one pneumatic brake control valve 12 such as an ADB, ABDX or ABD type valve made by the Westinghouse Air Brake Company (WABCO) . Under conditions known in the brake control art, the brake control valve 12 charges the two reservoirs 9 and 10 with the pressurized air it receives from the brake pipe 4. It is the pressure level within the brake pipe 4 that determines whether the brake control valve 12 will indeed charge these reservoirs or deliver pressurized air previously stored in one or both of these reservoirs to the brake cylinders 11. When so pressurized, the brake cylinders 11 convert the pressurized air that they receive from the brake control valve 12 to mechanical force. From the brake cylinders this force is transmitted by mechanical linkage to the brake shoes. The magnitude of the braking force applied to the wheels and/or disc brakes of the railcar is directly proportional to the pressure built up in the brake cylinders. Forced against the wheels and/or disc brakes, the brake shoes are used to slow and/or stop the rotation of the wheels. It is thus the pressure level in the brake pipe 4 that determines whether and to what extent the railcar brakes will be applied.

In addition to the brake pipe 4, the locomotive 2 has its own pneumatic trainlines including a main reservoir equalizing (MRE) pipe, an independent application and release (IAR) pipe, and an actuating pipe. Within a locomotive consist (i.e., two or more locomotives connected together), the MRE, actuating and IAR pipes of each locomotive connect to the MRE, actuating and I7AR pipes of the adjacent locomotives. The MRE pipe is used to equalize the pressure between the main reservoirs of each locomotive in a consist. Air stored in the main reservoir of a locomotive is used to charge the brake pipe to a normal operating pressure of approximately 90 psi when the brakes are released. It is the pressure within the IAR pipe that controls the delivery of pressurized air to, and thus the operation of, the brakes of the locomotive (s) in the train.

There are many different types of conventional brake control systems in use in the railroad industry, both in North America and in Europe. An example of one type of conventional brake control system is the 26-L Locomotive Air Brake Control System manufactured by WABCO. The 26-L System has two brake handles referred to as the automatic and independent brake handles 21 and 22. By placing these handles into the appropriate positions, a train operator in the locomotive can control how the brakes on the locomotive (s) and railcars operate. More specifically, by moving these handles into the proper position, the operator can control how much pressure will be developed in the IAR and brake pipes, as well as in the other pneumatic trainlines of the freight train. Whether affected by brake handle position as in the 26-L System commonly used in North America or by other means as may be used in Europe, the pressure level in the brake pipe 4 is what determines how the pneumatic brake equipment on each railcar will operate. The operation of the 26-L System is now described, specifically as to how movement of the brake handles 21 and 22 affects the pressure in the brake pipe 4. The brake handles are discussed only for purpose of explaining to the reader how the pressure level in the brake pipe 4 can be controlled. It is to be understood that such control may be had by using either brake handles, as in the 26-L System, or other means, as may be used in Europe. By moving the independent brake handle 22, the train operator can direct the brake control system only to apply or release the brakes on the locomotive (s) . In contrast, by moving the automatic brake handle 21, the operator can direct the brake control system to apply or release the brakes on both the locomotive (s) and railcars in the train. The level to which the system reduces or increases pressure within the brake pipe 4, and thus the amount of braking power exerted by the train brakes, ultimately corresponds to the position of the automatic brake handle 21. The automatic brake handle 21 can be moved from and in between a release position at one extreme (in which brake pipe pressure is maximum and the brakes are completely released) to an emergency position at another extreme (in which brake pipe pressure is zero and the brakes are fully applied) .

The positions for the automatic brake handle 21 include release, minimum service, full service, suppression, continuous service, and emergency. Between the minimum and full service positions lies the service zone wherein each incremental movement of the automatic brake handle toward the full service position causes an incremental reduction in brake pipe pressure. The exact amount by which the brake pipe pressure is reduced depends on how far towards the full service position the brake handle 21 is moved. It is this reduction in pressure that signals the brake control valve (s) 12 on each railcar to supply pressurized air from one or both reservoirs 9/10 to the brake cylinders 11 so as to apply the railcar brakes. The amount of pressure built up in the brake cylinders, and thus the magnitude of the braking force applied to the wheels, is proportional to the amount by which the brake pipe pressure has been reduced.

When the automatic brake handle 21 is moved from within the service zone or above towards the release position, the way in which the brakes operate depends on whether the brake equipment has been designed to allow a graduated release of the brakes. Freight trains in the United States typically use brake equipment that permits only a direct release of the brakes. Freight trains in Europe, however, feature brake equipment that allows a graduated release of the brakes. For direct release equipment, in response to such movement of the automatic brake handle 21, the brake control system in the locomotive 2 does not command an increase in the pressure within the brake pipe 4 until the automatic brake handle 21 is placed in the release position. Once the pressure in the brake pipe 4 increases above a preset level (e.g., 2 psi) , the brake control system and the railcar brake control valves 12 it affects respond by completely venting the brake cylinders thereby fully releasing the train brakes. For graduated release equipment, in response to such movement of the automatic brake handle 21 toward the release position, the brake control system commands an increase in the pressure in the brake pipe 4 incrementally. The level to which the brake pipe pressure rises is dependent on the extent to which the automatic brake handle 21 is moved toward the release position. Unlike the locomotive brake control system and pneumatic brake control valves for direct release equipment, those designed for graduated brake release react to this incremental rise in brake pipe pressure by reducing proportionately the pressure in the brake cylinders and thereby the force with which the train brakes are applied.

Freight trains are often equipped with any one of several known end-of-train (EOT) radio telemetry systems. As shown in Figure 1, these systems typically include a locomotive control unit (LCU) 51 located in the locomotive 2 and an EOT device 55 mounted to the last railcar. The EOT device 55 is coupled to the brake pipe 4 on the last railcar 3 by means of a hose and a glad hand.

In a one-way EOT system, the EOT device 55 transmits by radio signals to the LCU 51 data pertaining to the pressure in the brake pipe and the motion of the last railcar 3. To accomplish this, the EOT device includes a pressure transducer to monitor brake pipe pressure, a motion sensor to sense movement of the railcar, a microprocessor unit to control the overall operation of these components, and a transmitter that the microprocessor unit uses to transmit this last railcar data. In the locomotive 2, the LCU 51 includes a primary display, a receiver to receive transmissions from the EOT device, and a microprocessor unit. Controlled by the microprocessor unit, the primary display of the LCU 51 is used to convey the last railcar data to the train operator.

In freight trains, including those equipped with a one-way EOT system, the emergency brake application starts at the lead locomotive 2 and progresses along the brake pipe 4 to the last railcar. Especially for long freight trains, reducing the pressure in the brake pipe 4 from the lead locomotive 2 can be quite time consuming. Moreover, if one of the angle cocks 5 is left closed or the brake pipe 4 is otherwise restricted, the brake equipment beyond the restriction may not receive the emergency brake command needed to apply the brakes in an emergency. For this reason, the railroad industry developed two-way EOT radio telemetry systems.

In a two-way EOT system such as the TRAINLINt^ II EOT system manufactured by WABCO, the LCU and EOT device still perform all of the functions attributed to their counterparts in the one-way EOT system. The EOT device 55 is thus still used to transmit the aforementioned radio signals by which last railcar brake pipe pressure and motion data is conveyed to the LCU 51. The two-way EOT and LCU devices, however, are each equipped with a transceiver (i.e., combination transmitter and receiver) as compared to the single transmitter and receiver for the one-way EOT and LCU devices, respectively. The two-way EOT device 55 also has a pneumatic valve that is controlled by its microprocessor unit, and the LCU 51 also includes an emergency toggle switch. By toggling this switch, the train operator can cause the LCU 51 to transmit an emergency brake radio signal to the EOT device 55. By its microprocessor unit, the EOT device 55 responds to this emergency signal by commanding its pneumatic valve to reduce the pressure in the brake pipe 4 at an emergency rate. Combined with the emergency reduction in brake pipe pressure initiated from the brake control system in the lead locomotive 2, the two-way EOT system allows an even faster application of the railcar brakes in an emergency. In this two-way EOT system, the LCU 51 has a primary display panel which features a dedicated display for each of several types of last railcar data. The last railcar data displayed includes brake pipe pressure, low battery condition, whether the railcar is stopped or in motion, and whether an emergency has been enabled or disabled. The LCU 51 also has a supplemental message display by which it visually conveys additional information such as, for example, data related to arming of the EOT system and whether or not the EOT device 55 and LCU 51 are communicating properly.

It is, of course, well known that the brake equipment on a freight train is configured so that an emergency brake application is initiated at a rate faster than a service brake application. Typically, the emergency reduction in pressure propagates along the brake pipe 4, aided by each successive brake control valve, at a speed of approximately 900 feet/sec. Consequently, for a one mile long freight train, the emergency brake command, if initiated from the head of the train only, would take approximately 10 to 15 seconds to propagate from the lead locomotive 2 to the end of the train. By contrast, a service brake application can take a considerably longer time to reach the last railcar, well over a minute on those freight trains equipped with the older, slower reacting brake control valves. For this reason, the railroad industry developed another type of two-way EOT radio telemetry system, one that permits service brake applications to be implemented at both ends of a freight train.

An example of such a two-way EOT system is the TRAINLINI ^ ES EOT system manufactured by WABCO. In addition to the two-way LCU and EOT devices, the TRAINLINl ES system has a Service Interface Unit (SIU) 52 that connects between the serial port of the ES LCU 51 and the brake pipe 4 on the locomotive, as shown in Figure 1. The SIU 52 provides the ES LCU 51 with the current brake pipe pressure. This allows the ES LCU 51 to initiate automatically a service brake application at the last railcar simultaneously with the service reduction in brake pipe pressure initiated from the lead locomotive 2. Specifically, the ES LCU 51 in the locomotive 2 automatically transmits a service brake radio signal to the ES EOT device 55 when it detects a service reduction in brake pipe pressure via the SIU 52. By its microprocessor unit, the two-way ES EOT device 55 responds to this service brake signal by commanding its valve to reduce the brake pipe pressure from the last railcar at approximately the same service rate as that ordered by the brake control system in the lead locomotive 2. A service application of the brakes can thus be made much faster on a freight train equipped with a TRAINLINFL® ES or similar type EOT system. Using the SIU 52, the ES LCU 51 can also automatically transmit an emergency brake signal when an emergency reduction in brake pipe pressure has been initiated by the brake control system in the locomotive 2. The emergency toggle switch on the ES LCU 51 can also be used to transmit this emergency brake signal . Many European freight trains use a brake control system that employs a different scheme of initiating a service application of the brakes on the train. In particular, the brake control system in the lead locomotive 2 is designed to emit a quick service pulse (QSP) which the brake pipe 4 conveys sequentially to each railcar 3 in the train. The QSP is manifested as a brief drop in pressure, one whose characteristic is distinct from any service brake command and easily recognized by the pneumatic brake equipment on each railcar. By its nature, the QSP propagates along the brake pipe 4 far more rapidly than does a service brake command. It is used to inform each railcar that the brake control system will soon issue a service brake command. In response to the QSP, each brake control valve 12 is designed to reduce the brake pipe pressure locally by a set minimal amount. Conveyed along the brake pipe 4 just prior to the service brake command, the QSP is a means of reducing the amount of time it takes for the brake equipment to implement a service brake application on the train. No matter what type of freight train one considers, a primary goal is to apply the brakes on every vehicle in the shortest possible time. European freight trains that employ the QSP scheme to initiate a service brake application, however, are usually limited in length because even the QSP takes time to propagate the length of the train. By using a two-way EOT system such as the TRAINLINIC ES, however, the overall time it takes to implement a service brake application on QSP-schemed European freight trains can be reduced. As noted earlier, the LCU in the locomotive 2 would automatically transmit a service brake radio signal to the EOT device when it detects a service reduction in brake pipe pressure via the SIU. The EOT device would then respond to the service brake signal by commanding its valve to reduce the pressure in the brake pipe 4 on the last railcar at nearly the same service rate as that ordered by the brake control system in the lead locomotive 2. Such a two-way EOT system can be easily implemented on European freight trains, and would make possible the use of longer QSP-schemed trains.

One problem with such a configuration is posed by the environment in which it would be used. Specifically, the radio link between the LCU and the EOT device may not be completely infallible, especially when the train passes under bridges, through tunnels or as it winds it way through mountainous regions. Simply put, the terrain in which a freight train operates may have a topography with natural, or man-made, obstructions which could block or, at the very least, interfere with the transmission and reception of the radio signals.

One technique of overcoming this problem has been proposed. It involves adding more capability to the EOT device, namely, configuring the EOT device to react pneumatically to the QSP. This would, ideally, be in addition to the capability of the EOT device to react to the service brake radio signal. Specifically, the EOT device could be configured to detect the QSP using its pressure transducer. Once the QSP is detected, the EOT device by its microprocessor unit could then command its valve to reduce locally the pressure in the brake pipe 4 by the aforementioned set amount. Alternatively, its microprocessor unit could be programmed to respond to the QSP by opening the valve for a set period of time (e.g., 15-20 seconds) to make a more substantial reduction in brake pipe pressure. Once the valve closes, the pressure in the brake pipe at the rear end of the train would increase or decrease depending on the magnitude of the service brake command issued by the brake control system in the locomotive. Consequently, should it be unable to receive and react to the service brake radio signal, the EOT device would always be able to detect and react to the QSP. For whatever reason the radio link fails, this technique would permit the EOT device to contribute, albeit minimally, to the overall reduction in brake pipe pressure required by the brake control system to implement a service application of the brakes. The primary problem with this technique, however, is that the QSP conveys no information other than the knowledge that a service brake command will soon be issued. Consequently, the QSP does not inform the EOT device of the magnitude of the upcoming service brake application. As currently implemented, the EOT device can only get the information regarding the magnitude of the brake application from the service brake radio signal. The aforementioned technique does allow the EOT device to act upon the QSP whether or not the service brake radio signal is received. Unfortunately, it also leaves the EOT device incapable of implementing locally the correct level of service braking whenever the EOT radio link fails.

Moreover, in the latter alternative, by making a substantial reduction (especially a full service reduction) in brake pipe pressure in response to the QSP, the aforementioned technique could subject the train to high intensity draft (tensive) forces. Preventing excessive draft forces is a priority because a train could conceivably break in two if such forces become too strong. Damage to the railcars and their cargo can occur if the those forces are not kept below critical levels. By applying the brakes too strongly at the rear of the train in response to the QSP, the brake shoes, wheels and/or disc brakes on the last railcars in the train will also suffer premature and excessive wear. OBJECTIVES OF THE INVENTION

It is, therefore, a primary objective of the invention to provide a system and method of ascertaining pneumatically the magnitude of the service brake application sought by the brake control system in the locomotive and, from the rear of the train, assist the brake control system in implementing the service brake application of the desired magnitude.

Another objective is to provide a system and method of assisting the brake control system in the locomotive in implementing a service application of the brakes not by relying on an EOT radio link to convey and act upon radio brake signals but by monitoring the brake pipe at the end of the train and affecting the pressure thereat based on the change in the flow of air in the brake pipe initiated by the brake control system.

Yet another objective is to provide a system and method of assisting the brake control system in the locomotive in implementing a service application of the brakes, and, in so doing, keep draft forces at safe levels and prevent excessive wear of brake equipment, as compared to prior art techniques.

In addition to the objectives and advantages listed above, various other objectives and advantages of the invention will become more readily apparent to persons skilled in the relevant art from a reading of the detailed description section of this document. The other objectives and advantages will become particularly apparent when the detailed description is considered along with the drawings and claims presented herein.

SUMMARY OF THE INVENTION In a presently preferred embodiment, the invention provides an apparatus for, and a method of, assisting a brake control system in a locomotive in implementing a service application of the brakes on rail vehicles of a freight train. The train carries a brake pipe along which the brake control system conveys a quick service pulse (QSP) as a precursor to conveying a service brake command to all rail vehicles in the train. The brake control system is capable of deriving a service brake command by which it orders the brakes of the rail vehicles to implement a service application of the desired magnitude. The apparatus includes a pressure transducer, a pneumatic valve, a means for measuring flow rate, and a microprocessor unit. The pressure transducer is used to measure the pressure within the rear end of the brake pipe. When opened, the valve is used to exhaust air from the rear end of the brake pipe. The means for measuring flow rate is used to measure the rate at which air exhausts from the brake pipe when the valve is open. The microprocessor unit is used to control the opening and closing of the valve in response to readings taken from the transducer or the means for measuring flow rate or both. In response to a reading from the transducer indicative of the QSP, the microprocessor unit will open the valve thereby allowing air to exhaust from the rear end of the brake pipe. Using the values of flow rate provided by the means for measuring, the microprocessor unit will calculate regularly the actual quantity of air that has exhausted thus far through the valve. As time passes, the microprocessor unit will compare the actual quantity of air with an expected quantity of air. Based on the results of the comparison, the microprocessor unit will manipulate the valve, after a preset time, as follows. If the actual quantity of air is nearly equal to the expected quantity, air continues to exhaust from the rear end of the brake pipe until the actual quantity starts to exceed the expected quantity according to a flow rate curve currently in effect. If the actual quantity of air fails to accrue to within a prefigured amount of the expected quantity, air exhausts until the actual quantity of air equals or exceeds the expected quantity according to an elevated flow rate curve. If the actual quantity of air exceeds the expected quantity, air exhausts from the rear end of the brake pipe until the actual quantity of air equals the expected quantity or exhaustion of air has ceased according to a lowered flow rate curve. Using this approach, the apparatus aids the brake control system in the locomotive in making a service application of the brakes on the rail vehicles with the desired magnitude.

The method that the invention provides is manifested in the following steps. A flow rate curve is formulated according to which air within the rear end of the brake pipe will be expected to exhaust when the QSP is detected there. The rear end of the brake pipe is monitored for the QSP to be issued by the brake control system. As soon as the QSP is detected, air is allowed to exhaust from the rear end of the brake pipe. The flow rate —the rate at which air is being exhausted from the rear end of the brake pipe— is monitored continuously. Using the values of flow rate previously discerned, the actual quantity of air that has been exhausted from the rear end of the brake pipe is calculated regularly. As it accrues, the actual quantity of air is compared with an expected quantity of air as time passes. The expected quantity is the total amount of air that is expected to exhaust from the rear end of the brake pipe at any given time if both ends of the brake pipe were to exhaust air according to the flow rate curve currently in effect. If, after a preset time, the actual quantity of air fails to accrue to within a prefigured amount of the expected quantity, the amount or air oeing exnausteα rro the rear end ot the brale pipe is increased until the actual quantity of air equals or exceeds the expected quantity according to an elevated flow rate curve. If the actual quantity of air is nearly equal to the expected quantity, air will continue to exhaust from the brake pipe until the actual quantity of air starts to exceed the expected quantity according to the flow rate curve currently in effect. If the actual quantity of air exceeds the expected quantity, the flow of air from the rear end of the brake pipe is continuously reduced until the actual quantity of air equals the expected quantity according to a lowered flow rate curve. The exhaustion of air will eventually cease according to the flow rate curve currently in effect. By employing this method, a suitable apparatus can aid the brake control system in the locomotive in making a service application of the brakes.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a freight train equipped with a conventional brake control system and a two-way end-of-train (EOT) radio telemetry system. Figure 2 illustrates the brake pipe of a freight railcar and the pneumatic brake equipment to which it connects.

Figure 3 illustrates an EOT apparatus, according to the invention, that employs a flow meter to measure the rate at which air exhausts from the rear end of the brake pipe. Figure 4 illustrates an EOT apparatus, according to the invention, that employs a transducer and pressure versus fl ow ra te table to measure the rate at which air exhausts from the rear end of the brake pipe.

Figure 5 illustrates a flow rate profile for the invention as it assists the brake control system in implementing a service application whose magnitude is midway between that required for a minimum and a full application of the brakes.

Figure 6 illustrates a flow rate profile for the invention as it assists the brake control system in implementing a service application whose magnitude is below that required for a mid-level application.

Figure 7 illustrates a flow rate profile for the invention as it assists the brake control system in implementing a service application whose magnitude is above that required for a mid-level application.

Figures 8A and 8B show a block diagram of the steps of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Before describing the invention in detail, the reader is advised that, for the sake of clarity and ease of understanding, the invention is described in the following text as if carried out in the environment set out in the background section of this document. Despite being described in this particular context, it should be apparent from a reading of this document that the invention may be implemented on trains equipped with brake control systems and related ancillary equipment made by companies other than WABCO. The invention is presented is in this context not to limit the scope of the claims set forth below but merely to simplify the description, and thus the understanding, of the invention.

Figure 3 illustrates a specially configured end-of- train (EOT) type apparatus, generally designated 60. In this presently preferred embodiment, the EOT apparatus 60 includes a pressure transducer 61, a pneumatic valve 62, a microprocessor unit 63 and a flow meter 6 . Figure 4 illustrates an alternative embodiment of the EOT apparatus in which the flow meter is absent. The function of the EOT apparatus 60, in either embodiment, is to ascertain pneumatically the magnitude of the service brake application sought by the brake control system in the lead locomotive 2. Its primary goal is to assist the brake control system in implementing whatever magnitude of service brake application it desires for the train. Regarding the basic function of each component in the EOT apparatus 60, the pressure transducer 61 is used to detect the quick service pulse (QSP) and otherwise monitor the pressure within brake pipe 4 at the rear of the train. It converts the pressure to which it is exposed into an electrical signal whose attributes correspond to the characteristics of the pressure existing within brake pipe 4 at the time of the conversion. When opened by the microprocessor unit 63, the pneumatic valve 62 allows the pressure within brake pipe 4 at the rear of the train to exhaust to atmosphere. Even as the pressure changes within the brake pipe, the microprocessor unit 63 can maintain the rate at which air exhausts to atmosphere by varying the size of the orifice of the valve 62 through which the air escapes. With the pneumatic valve 62 open, the flow meter 64 can be used to measure directly the rate at which air exhausts from the brake pipe 4 at the rear of the train.

The microprocessor unit 63 is accompanied by the appropriate volatile and non-volatile memories to store data and programming code. Stored in this memory may be a pressure versus flow rate table whose values can be derived by empirical measurement. Flow rate again refers to the rate at which air will exhaust from brake pipe 4 when the valve 62 of the EOT apparatus 60 is open. To generate such a table, a distinct flow rate can be measured for, and will correspond to, each value of pressure within brake pipe 4. By sampling the electrical signal received from the pressure transducer 61, the microprocessor unit 63 can match each pressure reading it takes to its corresponding flow rate in the table. It is in this manner that the microprocessor unit 63 can keep track of the flow rate nearly continuously at the rear end of brake pipe 4. Alternatively, in lieu of the table, the microprocessor unit 63 can be kept apprised of the flow rate by taking readings directly from the flow meter 64. No matter how the flow rate values are obtained, by integrating them over time, the microprocessor unit 63 can calculate a reasonable estimate of how much air has exhausted to atmosphere while the pneumatic valve 62 has been held open.

In a manner well known in the brake control art, the brake control system in the lead locomotive 2 first issues the quick service pulse (QSP) . Shortly thereafter, it issues the service brake command along the brake pipe 4 to all of the railcars in the train. It is with the QSP that the brake control system primes the brake pipe 4 for the upcoming service brake command, i.e., it compels each of the brake control valves 12 to reduce the pressure locally by a set minimal amount. It is with the service brake command, however, that the brake control system actually orders the brake equipment on each railcar 3 to apply (i.e., to make a service application of) the brakes. The magnitude of the service brake application is also conveyed by the service brake command and is manifested as the extent to which the brake control system reduces the pressure in the brake pipe 4 from the front of the train. It represents the force with which the brakes should apply on each railcar. The EOT apparatus 60 of this invention is intended to assist the brake control system in the lead locomotive 2 in implementing a service application of the brakes on the train. Generally, in response to the QSP it receives from the brake control system, the EOT apparatus 60 shall immediately begin to reduce the pressure within brake pipe 4 at the rear of the train. As explained infra, the EOT apparatus 60 shall also determine whether air exhausts from the brake pipe according to a predetermined flow rate curve. Immediately after issuing the QSP, the brake control system in the locomotive 2 issues the service brake command. It is the goal of the EOT apparatus 60 to assist the brake control system at the other end of the train in generating the desired service brake command (i.e., the desired reduction in pressure) throughout brake pipe 4. The EOT apparatus 60 and the brake control system together can more quickly reduce the pressure within brake pipe 4 to the desired level, throughout the length of the train, than could the brake control system by itself from the front of the train. This allows the brake control valves 12 on the railcars 3 to carry out more quickly the service brake command derived by the brake control system.

The EOT apparatus 60 will, of course, exhaust air from the end of brake pipe 4 located opposite the brake control system in locomotive 2. The resulting reduction in pressure will thus propagate inwardly from the ends of brake pipe 4 towards the middle of the train. The predetermined flow rate curve, according to which the EOT apparatus 60 will gauge its operation at least initially, can be formulated to signify a brake command of any magnitude. It represents the variation that is expected to occur in the rate of flow when air is allowed to exhaust from the rear end of the brake pipe in response to the QSP. If both EOT apparatus 60 and the brake control system were exhausting air according to the same flow rate curve, the total amount of air that would be expected to exhaust from valve 62 would be, at any given time, the same as that exhausted from the front end of brake pipe 4. The predetermined flow rate curve will preferably manifest a mid- level service brake command. Notwithstanding the reduction emanating from the front, this fixed, expected quantity of air is herein referred to as Q_EXP. It is preferably chosen to be the same amount of air that the brake control system must exhaust at the front of the train to convey a mid-level service brake command along the brake pipe. By selecting such a mid range value for Q_E/p, the EOT apparatus 60 will be better able to assist the brake control system in the locomotive 2 in implementing both minimum and full service brake applications. Whether the EOT apparatus 60 will actually dump Q_E>-_F depends, however, on the magnitude of the brake command issued by the brake control system. The invention assists the brake control system in the lead locomotive 2 in implementing a service brake application of any magnitude. The EOT apparatus 60 shall first be described as to how it assists the brake control system in implementing a service application whose magnitude is midway between that required for a minimum and a full application of the brakes. It shall then be described as to how it assists the brake control system in implementing a service application whose magnitude is below that required for a mid-level application. Lastly, the EOT apparatus 60 shall be described as to how it assists the brake control system in implementing a service application whose magnitude is above that required for a mid-level application.

The EOT apparatus 60 is now described as to how it assists the brake control system in implementing a mid-level service application of the brakes. Before issuing this mid- level brake command, however, the brake control system in the lead locomotive 2 issues the QSP along the brake pipe 4 of the train 1. According to well established practice, the brake control valves 12 on each railcar 3 react to the QSP in sequence by priming the brake pipe for the upcoming mid-level service brake command.

Using its pressure transducer 61 and microprocessor unit 63, the EOT apparatus 60 detects the QSP as soon as it reaches the rear end of brake pipe 4. Specifically, the microprocessor unit 63 receives from the pressure transducer 61 a signal whose electrical characteristics unmistakably indicate the presence of the QSP. The microprocessor unit 63 responds to the QSP by opening the pneumatic valve 62, thereby allowing air to exhaust from the rear end of the brake pipe to atmosphere. Immediately after issuing the QSP, the brake control system in the locomotive 2 issues the mid-level service brake command according to prior art practice. By this particular command, the brake control system seeks to implement a reduction in brake pipe pressure of a magnitude midway between a minimum and a full service reduction. In implementing this mid-level reduction, the brake control system will exhaust air from the front end of brake pipe 4 and, in doing so, decrease the brake pipe pressure at a preset rate. (In freight trains in the United States, the mid-level reduction lasts approximately 15 seconds at a preset rate of about 1 psi/second, for a total of approximately 15 psi . ) With this particular service brake command, the brake control system thus seeks to exhaust from the front end of brake pipe 4 the same amount of air that the EOT apparatus 60 expects to exhaust from the rear end of the brake pipe .

While the brake control system and EOT apparatus 60 exhaust air from opposite ends of brake pipe 4, the microprocessor unit 63 continuously monitors the rate at which air flows from valve 62. As noted above, the microprocessor unit 63 can monitor the actual flow rate either directly using flow meter 64 or indirectly using transducer 61 in conjunction with the pressure versus flow rate table. The EOT apparatus 60 uses the actual flow rate values obtained during such monitoring to determine whether the air is being exhausted according to the predetermined flow rate curve (i.e., curve C_P) shown in Figure 5. No matter how the actual flow rate values are obtained, the microprocessor unit 63 integrates them over time so as to keep itself continuously apprised of the actual amount of air, Q_ACTV that has thus far been exhausted from the rear end of brake pipe 4. Preprogrammed with the expected flow rate values that comprise the predetermined flow rate curve, the EOT apparatus 60 is able to determine, by integration of all preceding values on the curve, the amount of air, Q_Eχp, that should have exhausted at any given point in time.

Operating according to its programming code, the microprocessor unit 63 will compare Q_ACτ with Q_EXP as time passes. Given that the brake control system has ordered here a mid-level service brake command, the actual flow rate values observed by microprocessor unit 63 at valve 62 should, if plotted, very nearly trace out the predetermined flow rate curve C_P in Figure 5. In other words, the total amount of air, Q_ACT, that the EOT apparatus 60 has exhausted from the rear end of brake pipe 4 at any given point in time should equal the amount of air expected from curve C_P to be exhausted up to that time, i.e., Q_EXP. Assuming this mid-level service brake command and the curve Cp, any difference between Q_EXP and Q_ACT should be minimal at any given point in time. Given that Q_Eχ_P and Q_Acτ are nearly equal at all points in time, the microprocessor unit 63 will infer the following. First, the brake control system in the lead locomotive 2 was exhausting roughly the same quantity of air from the front end of brake pipe 4 as the EOT apparatus 60 was from the rear. Second, in exhausting that quantity of air (i.e., Q_EXP)_/ the brake control system must have issued a mid-level magnitude service brake command. Because air has been exhausting from the front and rear ends of brake pipe 4 essentially at the same rate and in the same quantity, the microprocessor unit 63 will eventually close the pneumatic valve 62 as indicated by the flow rate curve C_P in Figure 5. The pressure at opposite ends of brake pipe 4 will then have been allowed to drop by a preselected amount, PSET-

The EOT apparatus 60 is now described as to how it assists the brake control system in implementing a service brake application whose magnitude is below that required for a mid- level application. Before issuing this low magnitude service brake command, the brake control system in the locomotive issues the QSP along brake pipe 4 sequentially to all railcars 3 in the train 1. According to well established practice, the brake control valves 12 on each railcar 3 react to the QSP in sequence by priming the brake pipe for the upcoming low magnitude service brake command. Using its pressure transducer 61 and microprocessor unit 63, the EOT apparatus 60 detects the QSP as soon as it reaches the rear end of brake pipe 4. The microprocessor unit 63 responds to the QSP by opening the pneumatic valve 62. Also capable of varying the extent to which valve 62 opens, the microprocessor unit 63 begins to exhaust air from the rear end of brake pipe 4.

Immediately after issuing the QSP, the brake control system in the locomotive 2 issues the low magnitude service brake command according to prior art practice. By this particular low magnitude command, the brake control system seeks to implement a reduction in brake pipe pressure of a magnitude lower than that required for a mid-level service application of the brakes. In implementing this low level reduction, the brake control system will exhaust from the front end of brake pipe 4 a smaller amount of air, Q_Low, than it would for a mid-level brake command. The magnitude or value of Q_Low depends, of course, on how slight of a service brake application is being ordered. Whatever the magnitude of the low level service brake command, the rate at which the air will be exhausted will be lower, or its duration will be shorter, than that typically required to carry out the mid-level service brake command. With this low magnitude brake command, the brake control system seeks to exhaust less air than the EOT apparatus 60 initially expects it to exhaust.

While the brake control system and EOT apparatus 60 exhaust air from opposite ends of the brake pipe, the microprocessor unit 63 continuously monitors the rate at which air flows from valve 62. The EOT apparatus 60 uses the actual flow rate values obtained during such monitoring to determine whether the air is being exhausted according to the predetermined flow rate curve C_P shown in Figure 6. By integrating the actual flow rate values obtained from such monitoring, the microprocessor unit 63 keeps itself continuously apprised of the actual amount of air, Q_ACT, that has thus far exhausted from the rear end of brake pipe 4. Microprocessor unit 63 can also compare the actual flow rate values with the expected flow rate values that comprise the predetermined flow rate curve C_P. Preprogrammed with these expected flow rate values, the microprocessor unit 63 is able to derive, by integrating all preceding values on curve C_P, the total amount of air, Q_Eχ_P, that it expects to have exhausted through valve 62 at any given point in time. Operating according to its programming code, the microprocessor unit 63 will compare Q_ACτ with Q_EXP on a continual basis. Given that the brake control system has ordered here a low magnitude service brake command, the actual flow rate values initially observed by microprocessor unit 63 at valve 62 will, if plotted, not trace out the predetermined flow rate curve C_P shown in Figure 6. Instead, the observed flow rate values will, at least initially, plot out the curve C_Bι shown in Figure 6. This curve shows that that the rate at which air is exhausting from valve 62 is higher than expected, significantly higher than it would be if the brake control system were implementing a mid- level or higher magnitude service brake command. From these high flow rate values, the microprocessor unit 63 is informed that the brake control system has dumped from the front end of the brake pipe less air than expected for a mid-level service brake command. In other words, the amount of air that has thus far exhausted from valve 62 (i.e., Q_Aτ) is greater than the amount expected (i.e., QEXP) from curve C_P during this time period.

By continually comparing the actual and expected flow rate values, the microprocessor unit 63 will be able to approximate the magnitude of the serve brake application currently being sought by the brake control system in the locomotive 2. In particular, the microprocessor unit 63 derives a new flow rate curve, identified as curve C_TARGET in Figure 6, based on the magnitude of the difference between the actual and expected flow rate values. The new flow rate curve is comprised of a new set of flow rate values that serve as targets for the EOT apparatus 60 to meet. From the new flow rate curve, the EOT apparatus is informed about how much air that it should expect the brake control system to have exhausted at any given time, given the low magnitude service brake command currently in effect. Operating according to these new flow rate values, the microprocessor unit 63 will adjust the extent to which valve 62 is open so that the actual amount of air vented to atmosphere, i.e., Q_Acτ_/ will closely track that being exhausted from the front end of the brake pipe. With the air now being exhausted from both ends of the brake pipe approximately at the same rate and in the same quantity, the microprocessor unit 63 will eventually close the pneumatic valve 62 as indicated by flow rate curve C_TARGET in Figure 6. The EOT apparatus 60 thus derives and uses the new flow rate curve to more closely comport its operation with that of the brake control system in the locomotive . The EOT apparatus 60 is now described as to how it assists the brake control system in implementing a service application whose magnitude is above that required for a mid- level application of the brakes. Before issuing this high magnitude service brake command, the brake control system in the lead locomotive 2 issues the QSP along brake pipe 4 sequentially to all railcars 3 in the train 1. The brake control valves 12 on each railcar 3 react to the QSP in sequence by priming the brake pipe for the upcoming high magnitude service brake command . Using its pressure transducer 61 and microprocessor unit 63, the EOT apparatus 60 detects the QSP as soon as it reaches the rear end of brake pipe 4. The microprocessor unit 63 then responds to the QSP by opening the pneumatic valve 62 so that air exhausts from the rear end of brake pipe 4 at the preset rate.

Immediately after issuing the QSP, the brake control system in the locomotive 2 issues the high magnitude service brake command according to prior art practice. By this particular command, the brake control system seeks to reduce the pressure in the brake pipe by an amount greater than that required for a mid-level service application of the brakes. In doing so, the brake control system will exhaust from the front end of brake pipe 4 a larger amount of air, Q_HIGH, than it would for a mid-level brake command. The magnitude of Q_HIGH depends, of course, on the strength of the service brake application being ordered. Whatever the magnitude of this high level service brake command, its duration will, of course, be more than the 15 seconds typically required to carry out a mid-level service brake command. Through this high magnitude brake command, the brake control system seeks to exhaust more air than the EOT apparatus 60 initially expects it to exhaust from the predetermined flow rate curve C_P shown in Figure 7. While the brake control system and EOT apparatus 60 exhaust air from opposite ends of the brake pipe, the microprocessor unit 63 continuously monitors the rate at which air flows from valve 62. The actual flow rate values obtained during such monitoring are used to determine whether the air is being exhausted according to the predetermined flow rate curve Cp. By integrating the actual flow rate values obtained during such monitoring, the microprocessor unit 63 keeps itself continuously apprised of the actual amount of air, Q_ACτ_/ that has thus far exhausted from the rear end of brake pipe 4. Microprocessor unit 63 compares the actual flow rate values with the expected flow rate values that comprise the predetermined flow rate curve C_P. Preprogrammed with these expected flow rate values, the microprocessor unit 63 can derive, by integrating all preceding values on curve C_P, the total amount of air, Q_EXP, that it expects to have exhausted through valve 62 at any given point in time.

Operating according to its programming code, the microprocessor unit 63 will compare Q_ACτ with Q_EXP on a continual basis. Given that the brake control system has ordered here a high magnitude service brake command, the actual flow rate values initially observed by microprocessor unit 63 at valve 62 will, if plotted, not trace out the predetermined flow rate curve C_P shown in Figure 7. Instead, the observed flow rate values will, at least initially, plot out the curve C_B2 shown in Figure 7. This curve shows that that the rate at which air is exhausting from valve 62 is lower than expected, significantly lower than it would be if the brake control system were implementing a mid-level or lower magnitude service brake command. From these low flow rate values, the microprocessor unit 63 is informed that the brake control system has dumped from the front end of the brake pipe more air than expected for a mid-level service brake command. In other words, the amount of air that has thus far exhausted from valve 62 (i.e., Q_ACT) is smaller than the amount expected from curve C_P (i.e., Q_EXP) during this time period.

By continually comparing the actual and expected flow rate values, the microprocessor unit 63 will be able to approximate the magnitude of the serve brake application currently being sought by the brake control system at the front of the train. In particular, the microprocessor unit 63 derives a new flow rate curve, identified as curve C_TARG_ET in Figure 7, based on the magnitude of the difference between the actual and expected flow rate values. The new flow rate curve is comprised of a new set of flow rate values that serve as targets for the EOT apparatus 60 to meet. From the new flow rate curve, the EOT apparatus is informed about how much air that it should expect the brake control system to have exhausted at any given time, given the high magnitude service brake command currently in effect. Operating according to these new flow rate values, the microprocessor unit 63 w ll adjust the extent to which valve 62 is open so that the actual amount of a r vented to atmosphere, i.e., Q_ACTA will closely track that being exhausted from the front end of the brake pipe. With the air now being exhausted from both ends of the brake pipe approximately at the same rate and in the same quantity, the microprocessor unit 63 will eventually close the pneumatic valve 62 as indicated by flow rate curve C_TARGET in Figure 7. The EOT apparatus 60 thus derives and uses the new flow rate curve to more closely comport its operation with that of the brake control system m the lead locomotive 2.

From the foregoing, t should be apparent that the flow meter 64, along with the microprocessor unit 63 --to the extent that it aids m measuring flow rate, essentially serve as a means for measuring the rate at which air exhausts from the rear end of the brake pipe. The pressure transducer 61, the pressure versus flow ra te table, and, again, the microprocessor unit 63 also basically constitute a means for measuring the rate at which air exhausts from the rear end of the brake pipe. It is intended that various other arrangements of these parts or even different parts that together perform the same function as the cited means are to be encompassed by one or more of the following claims. Figures 8A-8B show the essential steps for a method of assisting the brake control system in the lead locomotive 2 in implementing a service application of the brakes on a train. This method does not rely on an EOT radio link to convey and act upon radio brake signals to accomplish the objective, even though it can be used in conjunction with an ES EOT radio telemetry system. In carrying out this method, an initial flow rate curve is formulated. This predetermined flow rate curve represents the variations that are expected to occur in the rate of flow when air is allowed to exhaust from the rear end of the brake pipe in response to the QSP. Preferably formulated to signify a mid-level service brake command, this initial flow rate curve also depends on the operating pressure inherent to the brake equipment and piping of the train on which the method is to be used.

The remaining steps of the method are as follows. First, the rear end of the brake pipe is monitored for the QSP to be issued by the brake control system. As soon as the QSP is detected, air is allowed to exhaust from the rear end of the brake pipe. The flow rate —the rate at which air is being exhausted from the rear end of the brake pipe— is monitored continuously. Using the values of flow rate previously discerned, the actual quantity of air that has been exhausted from the rear end of the brake pipe is calculated regularly. As it accrues, the actual quantity of air is compared with an expected quantity of air as time passes. The expected quantity is the total amount of air that is expected to have exhausted from the rear end of the brake pipe at any given time if both ends of the brake pipe were exhausting air according to the flow rate curve currently in effect. If, after a preset time, the actual quantity of air fails to accrue to within a prefigured amount of the expected quantity, the amount of air being exhausted from the rear end of the brake pipe is increased according to an elevated flow rate curve until the actual quantity of air equals or exceeds the expected quantity. If the actual quantity of air is nearly equal to the expected quantity, air will continue to exhaust from the brake pipe according to the flow rate curve currently in effect until the actual quantity of air starts to exceed the expected quantity. If the actual quantity of air exceeds the expected quantity, the flow of air from the rear end of the brake pipe is continuously reduced according to a lowered flow rate curve until the actual quantity of air equals the expected quantity. The exhaustion of air will eventually cease according to the flow rate curve currently in effect. By employing this method, an EOT apparatus can assist the brake control system in the locomotive in dropping the pressure throughout the brake pipe to the target level dictated by the service brake command. Regarding the alternative embodiment, the invention may be carried out using an existing EOT device, such as the ES EOT device 55 described in the background section of this document. This would, however, require extensive modification to the ES EOT device. The pressure versus flow rate table would have to be stored in the memory of the microprocessor unit. The ES EOT device would also need its programming code modified to accommodate the algorithms embodied in the foregoing method steps .

Regarding the preferred embodiment, should one wish to use the flow meter 64 (in lieu of the pressure versus flow rate table) to measure the rate at which air exhausts from the rear end of the brake pipe, the microprocessor unit 63 would also need to be interfaced with the flow meter to accomplish the method, and realize the system, described in the foregoing paragraphs.

The presently preferred and alternative embodiments for carrying out the invention have been set forth in detail according to the Patent Act. Persons of ordinary skill in the art to which this invention pertains may nevertheless recognize various alternative ways of practicing the invention without departing from the spirit and scope of the following claims. Those of such skill will also recognize that the foregoing description is merely illustrative and not intended to limit any of the ensuing claims to any particular narrow interpretation. Accordingly, to promote the progress of science and the useful arts, I secure for myself by Letters Patent exclusive rights to all subject matter embraced by the following claims for the time prescribed by the Patent Act.

Claims

I claim :

1. A method of assisting a brake control system in a locomotive in implementing a service application of brakes on rail vehicles of a train, said train having a brake pipe along which said brake control system conveys a quick service pulse as a precursor to conveying a service brake command, said service brake command being used to order said brakes of said rail vehicles to implement said service application with a desired magnitude, said method comprising the steps of:

(a) formulating a flow rate curve according to which air within a rear end of said brake pipe will be expected to exhaust when said quick service pulse is detected thereat;

(b) monitoring said rear end of said brake pipe for said quick service pulse;

(c) reacting to said quick service pulse by commencing to exhaust air from said rear end of said brake pipe;

(d) monitoring continuously a flow rate at which air is exhausting from said rear end of said brake pipe; (e) calculating regularly, using values of said flow rate previously discerned, an actual quantity of air that has been exhausted from said rear end of said brake pipe;

(f) comparing said actual quantity of air with an expected quantity as time passes, said expected quantity being the total amount of air that should have exhausted from said rear end of said brake pipe at any given time if both ends of said brake pipe were exhausting air according to said flow rate curve currently in effect; and

(g) responding to results of said comparison such that if after a preset time said actual quantity of air:

(i) has failed to accrue to within a prefigured amount of said expected quantity, then increase the amount of air being exhausted from said rear end of said brake pipe until said actual quantity of air equals or exceeds said expected quantity according to an elevated flow rate curve;

(ii) is nearly equal to said expected quantity, then continue to exhaust air from said rear end of said brake pipe until said actual quantity of air starts to exceed said expected quantity according to said flow rate curve currently in effect; and

(iii) exceeds said expected quantity, then continuously reduce the flow of air from said rear end of said brake pipe until said actual quantity of air equals said expected quantity or exhaustion of air has ceased according to a lowered flow rate curve; thereby aiding in implementing said service application of said brakes of said rail vehicles with said desired magnitude.

2. The method claimed in claim 1 wherein said monitoring step comprises:

(a) employing a table in which for each value of pressure measured within said rear end of said brake pipe is correlated a particular flow rate at which air will exhaust from said brake pipe when said rear end thereof is opened;

(b) matching each of said values of pressure read while air is exhausting from said rear end of said brake pipe to said particular flow rate corresponding thereto in said table; and (c) storing said flow rates read from said table for use in said calculating step.

3. The method claimed in claim 1 wherein said monitoring step comprises: (a) employing a flow meter to measure continually said flow rate at which air is being exhausted from said rear end of said brake pipe; and

(b) storing said flow rates read from said flow meter for use in said calculating step.

4. An apparatus for assisting a brake control system in a locomotive in implementing a service application of brakes on rail vehicles of a train, said train having a brake pipe along which said brake control system conveys a quick service pulse as a precursor to conveying a service brake command, said service brake command being used to order said brakes of said rail vehicles to implement said service application with a desired magnitude, said apparatus comprising: (a) a pressure transducer for measuring pressure within a rear end of said brake pipe;

(b) a valve for exhausting air from said rear end of said brake pipe when said valve is open;

(c) a means for measuring a rate at which air exhausts from said rear end of said brake pipe via said valve; and

(d) a microprocessor unit for controlling said valve in response to readings taken from at least one of said pressure transducer and said means for measuring such that said microprocessor unit responds to a reading from said pressure transducer indicative of said quick service pulse by (i) opening said valve thereby allowing air to exhaust from said rear end of said brake pipe; (ii) calculating regularly, using values of said rate previously read from said means for measuring, an actual quantity of air that has been exhausted through said valve; (iii) comparing said actual quantity of air with an expected quantity as time passes; and (iv) manipulating said valve based on results of said comparison such that if after a preset time said actual quantity of air:

(A) is nearly equal to said expected quantity, air continues exhausting from said rear end of said brake pipe until said actual quantity of air starts to exceed said expected quantity according to a flow rate curve currently in effect; (B) fails to accrue to within a prefigured amount of said expected quantity, air exhausts from said rear end of said brake pipe until said actual quantity of air equals or exceeds said expected quantity according to an elevated flow rate curve; and

(C) exceeds said expected quantity, air exhausts from said rear end of said brake pipe until said actual quantity of air equals said expected quantity or exhaustion of air has ceased according to a lowered flow rate curve; and thereby aiding in implementing said service application of said brakes of said rail vehicles with said desired magnitude.

5. The apparatus claimed in claim 4 wherein said means for measuring flow rate comprises: (a) said pressure transducer for measuring pressure within said rear end of said brake pipe;

(b) memory for storing a table in which for each value of pressure measured within said rear end of said brake pipe is correlated a particular value of flow rate at which air is known to exhaust from said brake pipe when said valve is opened; and

(c) said microprocessor unit for matching each of said readings taken from said pressure transducer while said valve is open to said particular value of flow rate corresponding thereto in said table, with said values of flow rate to be used in calculating regularly said actual quantity of air that has been exhausted from said rear end of said brake pipe via said valve.

6. The apparatus claimed in claim 4 wherein said means for measuring flow rate comprises: (a) a flow meter to measure said flow rate at which air is being exhausted from said rear end of said brake pipe; and

(b) said microprocessor unit for reading from said flow meter each of said values of flow rate, with said values of flow rate so read to be used in calculating regularly said actual quantity of air that has been exhausted from said rear end of said brake pipe via said valve.

7. A method of assisting a brake control system in a locomotive in implementing a service application of brakes on rail vehicles of a train, said train having a brake pipe along which said brake control system conveys a quick service pulse as a precursor to conveying a service brake command, said service brake command being used to order said brakes of said rail vehicles to implement said service application with a desired magnitude, said method comprising the steps of:

(a) preselecting an amount by which pressure within a rear end of said brake pipe can be allowed to drop when said quick service pulse is detected thereat; (b) monitoring said rear end of said brake pipe for said quick service pulse;

(d) monitoring continuously a flow rate at which air is exhausting from said rear end of said brake pipe;

(e) calculating regularly, using values of said flow rate previously discerned, an actual quantity of air that has been exhausted from said rear end of said brake pipe;

(f) comparing said actual quantity of air with an expected quantity as time passes, said expected quantity being the total amount of air that should have exhausted from said rear end of said brake pipe at any given time if both ends of said brake pipe were exhausting air according to a predetermined flow rate curve ; and (g) responding to results of said comparison such that if after an expected time said actual quantity of air:

(i) has failed to accrue to within a prefigured amount of said expected quantity, then increase the amount of air being exhausted from said rear end of said brake pipe according to an elevated flow rate curve until said actual quantity of air equals or exceeds said expected quantity;

(ii) is nearly equal to said expected quantity, then continue to exhaust air from said rear end of said brake pipe according to said flow rate curve currently in effect until said actual quantity of air starts to exceed said expected quantity; and