Abstract:
A system and method for incrementally accomplishing brake pipe reductions using an operator button, touch sensitive screen or other human machine interface. The system is preferably made available to the user when the brake handle is positioned in the ‘minimum’ brake application position and allows an operator to create a more precise target reduction value without having to manually move the brake handle to the location that the operator believes may result in the desired reduction. Using small, predetermined increments, the system allows for more precise control over brake pressure without an operator having to estimate what handle movement will accomplish the desired brake pressure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to locomotive braking systems and, more particularly, to a system and method for incrementally reducing brake pipe pressure. 
     2. Description of the Related Art 
     Locomotive operators using pneumatic or electro-pneumatic braking systems are often required to make minor reductions in brake pipe pressure beyond the minimum braking level when grade braking or in other situations. Brake control levers positioned on a locomotive mounted brake controller are used as the man machine interface for brake pipe control. These levers typically have set positions for a defined reduction of equalizing reservoir (ER) pressure, which is the pilot pressure for the brake pipe relay and thus provides the target level for the brake pipe (BP) pressure. For example, the handle position typically labelled ‘minimum’ allows for the minimum amount of brake which can be applied, while the position referred to as ‘full service’ provides for a normal, full brake application. 
     While it is easy for an operator to get the brake pipe reduction requested at the ‘set’ positions, such as ‘minimum’ or ‘full service’, often the operator would like to have a reduction of brake pipe (BP) pressure just slightly greater than afforded by the ‘minimum’ position to operate the train in certain conditions. In these cases, the operator often must carefully manipulate the lever beyond the ‘minimum’ position toward the ‘full service’ position with caution so as not to over-brake the train. While control levers are good at giving the operator quick intuitive control of the brake level, they do not allow an operator to control the brake pipe (BP) pressure between the preconfigured ‘set’ positions as precisely as they desire in some situations. Another issue with conventional braking systems is that the locomotive operators making reductions in brake pipe pressure must often prevent the locomotives brakes from applying by using a bail off feature due to operating rules or the conditions of train control. In these cases, the operator must use both hands to apply the brakes. These same issues exist in electronically controlled pneumatic (ECP) brake systems. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention comprises an incremental brake pipe reduction system that allows an operator to create an equalizing reservoir (ER) target value without having to manually move the handle to an imprecise position. By using a pushbutton, a switch, or a touchscreen on the man-machine brake control interface or through an input or communication message to the brake system from another HMI device such as a button or operator display screen on the locomotive, the operator can request incremental reductions in brake pressure to more accurately select the desired level of braking. For example, once an operator has requested a ‘minimum’ brake application, the operator may then reduce brake pipe pressure in small, predetermined increments to provide for more precise control over brake pressure without having to move the brake handle to a position that the operator guesses will accomplish the desired decrease in desired brake pressure. Optionally, an amount of BP reduction within the service zone between ‘minimum’ and ‘full service’ could also be enabled to allow for this incremental reduction to occur. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a brake controller for implementing incremental brake pressure reduction according to the present invention; 
         FIG. 2  is a diagram of an exemplary embodiment of a method of implementing incremental brake pressure reduction according to the present invention; 
         FIG. 3  is a graph of the effect of incremental brake pressure reduction on the service zone without adjustment according to the present invention; and 
         FIG. 4  is a graph of the effect of incremental brake pressure reduction on the service zone with adjustment according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein like reference numerals refer to like parts throughout, there is seen in  FIG. 1  a brake controller  10  including a system  12  for incrementally adjusting brake pressure. As seen in  FIG. 1 , system  12  is made available to an operator by a single button  14  that allows operator to incrementally reduce brake pressure without having to move brake handle  16 . It should be recognized by those of skill in the art that button  14  may instead comprise a switch, a touchscreen, or a combination thereof on brake controller  10 , and that incremental reductions may be accomplished by depressing button  14  a series of times to accomplish a series of individual, predetermined reductions or holding button  14  down while a keystroke buffer gradually and periodically cycles through a series of incremental reductions until the appropriate level is reached and the operator releases button  14 . A display  18  may also be provided to show the operator the specific brake pressure being selected, or combined with button  14  as a touchscreen. 
     System  12  further comprises a controller  22  responsive to button  14  that implements the desired incremental reduction in brake pressure in the locomotive braking system. For example, controller  20  is programmed to implement the activities seen in  FIG. 2 . Controller  22  receives signals  24  and  26  representing the state of button  14  and the position of handle  16 , respectively. When signal  26  indicates that handle  16  is in the desired position, such as ‘minimum,’ controller  22  reads the state of button  14  from signal  24 , updates the ER target pressure  28  and calculates the desired ER target pressure  30 , and then outputs a command  32  to accomplish the desired pressure reduction. As explained in more detail below, controller  22  may also reconfigure the service zone range  34  to account for the incremental reductions selected by an operator using button  14 . When handle  16  is moved back to the ‘release’ position, the service zone is reset  36  and the existing brake pressure action  38  is released. While  FIG. 2  depicts controller  22  programmed to implement system  12  when handle  16  is in the ‘minimum’ position, other appropriate positions may be used. 
     System  12  may be programmed to implement various incremental reduction scenarios. For example, in a first embodiment of the present invention, button  14  can be depressed once for each increment desired, with a predetermined increment level such as individual steps of between 0.5 and 3 psi. In another embodiment, button  14  can be pressed as above or can also be held down with the feedback on a display  18  showing the ER target as it changes on an incremental basis. Button  14  could be released at any time resulting in the incremental reduction ceasing and the desired level shown on display  18 . Alternatively, system  12  may be programmed to restrict the amount of brake pipe reduction allowed by the pressing of button  14 , such as by having a maximum amount of reduction that is possible using button  14 , such as only allowing 1 psi of additional reduction, or limiting the reduction to the full service brake pipe level. 
     To improve visibility, button  14  may include illumination, such as LEDs that are positioned internally behind button  14  or externally and directed at button  14 , to illuminate button  14  when system  12  is available for use, such as when handle  16  is moved to the ‘minimum’ position. Illumination may be turned off when system  12  is disabled, such as by further motion of handle  16  or when a predetermined maximum amount of incremental reduction is reached. 
     When the BP is reduced beyond a ‘minimum’ application via system  12  with the handle still in the ‘minimum’ position, the service zone range, or the amount of BP reduction remaining from the current level to the ‘full service’ level, is reduced. As a result, further movement of handle  16  will not reduce the pressure, thereby causing a “dead zone” where movement of the handle that is typically understood to reduce brake pipe pressure does not do so. This effect may be seen in  FIG. 3 , wherein incremental BP reductions reduce the brake pipe pressure a further five psi from minimum and thus a portion of the movement of handle  16  from the minimum to ‘full service’ position will not cause any additional reduction in pressure until the position of handle  16  moves beyond the point where the typical handle-related reduction exceeds the amount of incremental reduction previously accomplished via button  14 . For example, if an operator places the handle in the ‘minimum’ position it normally results in a BP reduction of 7 psi from normal. The operator may then use button  14  to reduce the BP a total of 12 psi from the set point pressure, such as by pressing button  14  five times if the incremental reduction is set to one psi. If the operator were then to move the handle halfway between Min and Full Service (FS), and the FS reduction was 26 psi from normal, the handle movement would not result in any appreciable change in pressure over most of the distance because the move from ‘minimum’ to the halfway position only amounts to a single psi of reduction (13 psi total) over the 12 psi reduction that has already been accomplished by moving handle  16  to “minimum” and then depressing button  14  five times for an additional five psi reduction. 
     To avoid this effect, system  12  may optionally be programmed, such as in software running in controller  22 , to adjust the amount of reduction associated with the movement of handle  16  to account for incremental reductions made via button  14 , thereby eliminating any “dead zone.” As seen in  FIG. 4 , the service range may be adjusted to change the amount of pressure reduction associated with the movement of handle  16  so that the entire range of movement of handle  16  will accomplish a reduction in pressure relative to the decremented starting pressure and the full service pressure. For example, as seen in  FIG. 4 , movement of handle  16  will reduce brake pipe pressure throughout its entire range of movement, albeit at a slower rate of reduction, thereby compensating for the fact that pressure when handle  16  is first moved from the ‘minimum’ is less than the non-decremented minimum pressure level. Stated another way, movement of handle  16  from minimum to full service will reduce the pressure at a rate that is slightly less than the rate of reduction without adjustment to compensate for the fact that the starting pressure has been decremented by the operator of system  12 , thus allowing movement of handle  16  to effect a reduction throughout its entire range of movement. 
     In the embodiment of system  12  having automatic readjustment of handle operated pressure reduction, the present invention may optionally allow for automatic bail off of the locomotive brakes similar to that in conventional systems that allow for bail off of an initial application of the brakes. In this embodiment, an operator, having bailed off an initial application for a defined period of time (with the timing adjustable to customer requirements), may have the bail off actuated for a defined period of time (also adjustable to customer requirements) for each time button  14  is pressed. The bail off may be immediately cancelled if handle  16  is moved by the operator. Thus, controller  22  may be programmed to respond to signals  24  received from button  14  to actuate a bail off operation for predetermined time period. System  12  may additionally be programmed to provide an automated bail off of a brake application according to prior bailing off performed historically, such as in one or more prior manual brake applications using handle  16 . Any automated bail off may also be cancellable by programming system  12  to cancel any automated bail off in the event that handle  16  is moved by the operator.