Abstract:
A brake controller for a locomotive includes a train brake pipe, a locomotive brake pipe, a brake cylinder, a control valve and a relay valve. The first control input of the relay valve is selectively connected to one of the output of the control valve and the locomotive brake pipe; and the second control input of the relay valve is selectively connected to the locomotive brake pipe when the control valve output is a release signal. A first electro-pneumatic valve, when activated, causes the control valve to be a release signal. An electronic controller is connected to a first pressure transducer for the locomotive brake pipe, a lead/trail mode switch and the first electro-pneumatic valve; and activates the electro-pneumatic valve for brake release pressures in the locomotive brake pipe when the mode switch is in the trail mode.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   The present system relates generally to brake control systems and more specifically to a brake controller for a trail locomotive in a two pipe brake system. 
   The air braking industry has a long established control scheme of transferring braking requirement from a Lead locomotive to a Trail locomotive through a single train brake pipe or multiple unit brake pipe known as the brake cylinder equalizing or locomotive brake pipe. This is referred to as a two pipe system. This is distinguished by a three pipe brake system which has a train brake pipe, a locomotive apply and release brake pipe and a locomotive activate brake pipe. The Trailing locomotive is manually set to respond to a two pipe system through devices located within its braking system. The Trail locomotive as set does not respond to its control valve for the application of braking effort. Instead, the Trail locomotive responds directly to pressure within the brake cylinder equalizing pipe, which is controlled by the Lead locomotive, for the application of braking effort. The Lead locomotive is manually set to control the two pipe system through devices located within its braking system. The Lead locomotive then controls pressure within the brake cylinder equalizing pipe, which is a summary or cumulative affect of automatic, independent and bail braking controls and commands at the Lead locomotive. 
   A requirement in the train braking industry is to boost the independent braking request by 160% of the commanded pressure within the brake cylinder equalizing pipe. However, the commanded pressure within the brake cylinder equalizing pipe is not to be boosted for the automatic braking command pressure. An example of a prior art brake system is illustrated in  FIG. 1 , which will be discussed in detail below. A limitation in the system of  FIG. 1  is that it will not resume the 160% of independent brake application after a “bail” or independent brake release if the automatic braking signals a brake apply on the train brake pipe. The automatic brake must signal a brake release in the train brake pipe for the system to resume the 160% of independent brake application. 
   The present disclosure is a brake control for the Trail locomotive equipped with an electro-pneumatic braking control system that differentiates the independent (locomotive) braking from automatic (train) braking to determine whether to boost pressure by 160% or retain 100%. 
   A brake controller for a trail locomotive includes a train brake pipe, a locomotive brake pipe, a brake cylinder, a control valve being responsive to pressure in the train brake pipe to produce brake apply and brake release signals at an output, and a relay valve having first and second control inputs and having a source input and an exhaust input selectively connected to an output in response to the control inputs. The first control input is selectively connected to one of the output of the control valve and the locomotive brake pipe; and the second control input is selectively connected to the locomotive brake pipe when the control valve output is a release signal. A first pressure transducer is connected to the locomotive brake pipe. A mode switch having lead and trail modes is provided. A first electro-pneumatic valve is connected to the control valve which, when activated, causes the control valve to be a release signal. An electronic controller is connected to the first pressure transducer, the mode switch and the first electro-pneumatic valve, and activates the first electro-pneumatic valve for brake release pressures in the locomotive brake pipe when the mode switch is in the trail mode. 
   The control valve output remains as a release signal until a pressure is present in the train brake pipe which requires an increase brake apply signal by the control valve. A second electro-pneumatic valve may be provide which selectively connects the output of the control valve to the first control input of the relay valve. In such case, a second pressure transducer is connected to the train brake pipe. The electronic controller is connected to and controls the second electro-pneumatic valve to a) connect the output of the control valve to the first control input of the relay valve in the trail mode of the mode switch when pressure in the train brake pipe is below an emergency pressure and b) disconnect the control valve from the first control input of the relay valve in the trail mode of the mode switch when pressure in the train brake pipe is above an emergency pressure. 
   The first and second pneumatic valves may be dynamic brake interlock valves of an electro-pneumatic brake controller. Also a double check valve may be provided and has inputs connected to the output of the control valve and the locomotive pipe and an output connected to the first input of the relay valve. 
   These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a schematic of a portion of a brake controller for a two pipe system of the prior art. 
       FIG. 2  is a schematic of a portion of a brake controller for a two pipe system illustrating a first embodiment of the present system. 
       FIG. 3  is a schematic of a portion of a brake controller for a two pipe system illustrating a second embodiment of the present system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a typical prior art system as arranged for Trail braking. Only the elements that are pertinent to Trail braking are shown. The control valve  11  determines a determines a level of automatic braking by the pressure within the brake pipe trainline  10 . Pressure within the brake pipe trainline  10  is controlled by the Lead locomotive. Line  14  is the pressure output level of automatic braking determined by the Trail locomotive control valve  11  from the said brake pipe trainline  10 . When the input line  14  to the Lead/Trail selector  12  is disconnected from output line  15 , the output line  16  is connected to atmosphere or exhaust as shown. The selector  12 , when manually set to the Trail position, prevents the automatic braking level output of the control valve  11  from being connected to the brake cylinder relay  13  and thus preventing development of any braking pressure for the locomotive. 
   All braking pressure for the Trail locomotive is developed from the pressure level delivered from the Lead locomotive within the brake cylinder equalizing pipe trainline  20 . For independent braking, the Lead locomotive determines the operator request and sets the desired pressure level within the brake cylinder equalizing pipe trainline  20 . This pressure level via line  23  is delivered as inputs to each the double check valve  21  and the pilot valve  22 . When pressure within line  23  being greater than atmosphere as found in line  15 , then line  23  is connected through the double check valve  21  to line  16  as input to diaphragm ‘A’ of the brake cylinder relay valve  13 . Also, the input pressure level line  23  is connected through the deactivated pilot valve  22  to line  24  as input to diaphragm ‘B’ of the brake cylinder relay valve  13 . Diaphragm ‘A’ of the brake cylinder relay valve  13  is the 100% factor and diaphragm ‘B’ is the 60% factor. The brake cylinder relay valve  13  responds to a combined 160% factor developed output of brake cylinder pressure for the locomotive from the source, main reservoir, supply pressure. 
   For automatic braking, the Lead locomotive determines the operator request and sets the desired pressure level within the brake pipe trainline  10  and the desired pressure level within the brake cylinder equalizing pipe trainline  20 . As described in the first paragraph, the Trail locomotive control valve  11  responds to brake pipe trainline  10  to develop pressure within output line  14 . Output line  14  connection to the input line  16  of the brake cylinder relay valve  13  is prevented by the selector  12 . Output line  14  is connected to the pilot port of the pilot valve  22  thus activating the pilot valve  22 . When activated, the pilot valve  22  disconnects the input line  23  and connects line  24  to atmosphere or exhaust (EX). In this manner, during automatic brake applications, diaphragm ‘B’ or the 60% factor is removed from the pressure development of brake cylinder pressure. The brake cylinder relay valve  13  responds to the 100% factor developed output of brake cylinder pressure for the locomotive. 
   The automatic brake may be released by the Lead locomotive on operator command through the mechanics known in the industry as ‘bail.’ Release due to bail of the automatic brake does not change the pressure level within the brake pipe trainline  10  and thus the pressure developed by the control valve  11  of the Trail locomotive remains in line  14 . Pressure in line  14  maintains the pilot valve  22  to the activated position, thus maintaining a 100% factor output of the brake cylinder relay valve  13 . A subsequent independent brake application is not applied at the desired 160% factor. 
     FIG. 2  shows the improvement of the present disclosure as arranged for Trail braking. Only the elements that are pertinent within an electro-pneumatic controlled braking system to Trail braking are shown. Fundamental operation to the prior art are retained, however the pneumatic-mechanical Lead/Trail selector ( FIG. 1 ;  12 ) is omitted. The control valve  11  determines the level of automatic braking by the pressure in the brake pipe trainline  10  as controlled by the Lead locomotive. The output level of automatic braking in line  14  is connected to the input line  16  of brake cylinder relay  13 , through the double check valve  21 , when in the Trail position of operation. 100% factor automatic braking level output of the control valve  11  is developed at the output of the brake cylinder relay valve  13  for delivery to the locomotive brake cylinder. 
   For independent braking, pressure level within the brake cylinder equalizing pipe trainline  20  is delivered as inputs to each the double check valve  21  and the pilot valve  22 . When the pressure in line  23  is greater than that in line  14 , then line  23  is connected through the double check valve  21  to line  16  as input to diaphragm ‘A’ of the brake cylinder relay valve  13 . Also, the input pressure level line  23  is connected through the deactivated pilot valve  22  to line  24  as input to diaphragm ‘B’ of the brake cylinder relay valve  13 . The brake cylinder relay valve  13  responds to a combined 160% factor developed output of brake cylinder pressure for the locomotive from the source, main reservoir, supply pressure. 
   For automatic braking, the Lead locomotive determines the operator request and sets the desired pressure level within the brake pipe trainline  10  and the desired pressure level within the brake cylinder equalizing pipe trainline  20 . As described, the Trail locomotive control valve  11  responds to brake pipe trainline  10  to develop pressure within output line  14  of the control valve  11 . When the pressure in line  14  is greater than that in line  23 , then line  14  is connected through the double check valve  21  to input line  16  of the brake cylinder relay valve  13 . Conversely, pressure developed within the brake cylinder equalizing pipe trainline  20  by the Lead locomotive as the result of automatic braking is delivered to line  23  of the double check valve  21 . The higher of the pressure of line  23  or line  14  is delivered to the input line  16  of the brake cylinder relay valve  13 . Secondary, as in the prior art, output line  14  is connected to the pilot port of the pilot valve  22  thus activating the pilot valve  22 . When activated, the pilot valve  22  disconnects the input line  23  and connects line  24  to atmosphere or exhaust (EX). In this manner, during automatic brake applications, diaphragm ‘B’ or the 60% factor is removed from the pressure development of brake cylinder pressure. The brake cylinder relay valve  13  responds to the 100% factor developed output of brake cylinder pressure for the locomotive. 
   The automatic brake may be released by the Lead locomotive on operator command of ‘bail.’ Release due to bail of automatic brake does not change the pressure level within the brake pipe trainline  10  and thus the pressure developed by the control valve  11  within line  14 . The pressure developed in the brake cylinder equalizing pipe trainline  20  due to automatic brake is fully released to atmosphere. A controller  30 , as a portion of the electro-pneumatic braking control system, determines if in the Trail status by the Lead/Trail Switch (LTS)  31  as manually set by an operator. In Trail operation, the controller  30  monitors the pressure level within the brake cylinder equalizing pipe trainline  20  with the pressure level sensor (PLS)  32 . When fully released, the controller  30  activates an electro-pneumatic dynamic brake magnet valve (DBM)  33  located on the control valve  11  initially to set the control valve  11  to its ‘release’ mode, then deactivates or resets the DBM 33. In the ‘release’ mode the control valve  11  fully exhausts its output line  14  producing a release signal, thus releasing the automatic brake from the locomotive in response to brake cylinder equalizing pipe trainline bail. 
   As the controller  30  has effected the release of pressure within output line  14  of the control valve  11 , pilot valve  22  will deactivate and restore the connection to the 60% factor to the brake cylinder equalizing pipe trainline  20 . A subsequent independent brake application will apply at the desired 160% factor. 
   Subsequent automatic braking command will reinitiate the activity as described. 
     FIG. 3  shows an embellishment to  FIG. 2 . All the elements of  FIG. 2  are retained, however, an electro-pneumatic Lead/Trail selector  35  as activated by the controller  30  is added similar to that of the prior art ( FIG. 1 ;  12 ). The controller  30 , as a portion of the electro-pneumatic braking control system, determines if in the Trail status by the Lead/Trail Switch (LTS)  31  as manually set by an operator. In Trail operation, the controller  30  monitors the pressure level within the train brake pipe trainline  10  with the pressure level sensor (PLS)  34 . When determined that the train brake pressure is greater than an automatic emergency level, the controller  30  will activate the electro-pneumatic Lead/Trail selector  35 . As in the prior art, the selector  35  when activated prevents the automatic braking level output of the control valve  11  from being connected to the brake cylinder relay  13  and thus preventing development of any braking pressure for the locomotive. 
   When the train brake pipe trainline  10  pressure is determined less than an automatic emergency level, the controller  30  will deactivate the electro-pneumatic Lead/Trail selector  35  connecting the automatic braking level output of the control valve  11  to the brake cylinder relay  13 , thus development of emergency braking pressure for the locomotive. 
   This function may simply be integrated with resetting dynamic type magnet valve interlock with the controller of the electro-pneumatic braking system. 
   An example of an electro-pneumatic locomotive brake system is CCB® Locomotive Brake Control Unit available from New York Air Brake Corporation and is illustrated in U.S. Pat. No. 6,036,284, which is incorporated herein by reference. Other electro-pneumatic locomotive brake systems may be used. 
   Although the present invention has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present invention is to be limited only by the terms of the appended claims.