Patent Publication Number: US-7707945-B2

Title: Safety system for a locomotive walkway

Description:
FIELD OF THE INVENTION 
   This field of the invention relates generally to safety systems for locomotives, and more particularly to safety systems for locomotive walkways. 
   BACKGROUND OF THE INVENTION 
   In a conventional diesel-electric locomotive, drive traction motors provide the motive force to move the train. Typically, a diesel engine drives an alternator, which supplies current to drive traction motors, which, in turn, propel the locomotive forward or backward. When propelled as such, a locomotive is said to be motoring. 
   The traction motors, however, perform an additional function. Once the locomotive is in motion, traction motors may be configured to generate electricity instead of consuming it. As generators, the traction motors convert the locomotive&#39;s kinetic energy into electrical energy, thereby slowing the locomotive. Using the traction motors to reduce speed is called dynamic braking. Because there is no suitable storage medium for the generated electrical energy, an electrically resistive grid is used to convert the electrical energy into heat energy, which is vented to the atmosphere through a resistive grid exhaust on one side of the locomotive. The resistance grid exhaust is adjacent to an operator cabin and a walkway used by the operator during regular maintenance when the locomotive is stationary. 
   While the locomotive is stationary, during a self-load mode, the resistive grid may be used to test load a locomotive&#39;s power alternator and diesel engine. The resistive grid is disconnected from the traction motors and connected to the locomotive&#39;s alternator, and continues to convert electrical energy to heat energy, which is vented out through the resistive grid exhaust, as in the dynamic braking mode. When the locomotive is stationary, such as in the self-load mode, the operator may walk on the walkway to perform regular maintenance, and thus be positioned in the vicinity of the resistive grid exhaust. Accordingly, there is a need to provide additional safety in the walkway area to address these circumstances. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one embodiment of the present invention, a safety system is provided for a walkway of a locomotive. The safety system includes an operator cabin adjacent to the front end of the locomotive, and a walkway extending from the operator cabin along a first side of the locomotive to facilitate a locomotive operator performing regular locomotive maintenance. A resistive grid exhaust is positioned in a sidewall of the first side of the locomotive to direct hot air along a path from a resistive grid within the sidewall to external the locomotive during a self-load mode of the locomotive. More particularly, a barrier bar is positioned adjacent to the base of the resistive grid exhaust to extend to an extended position over the walkway during the self-load mode and prevent the operator from walking into the path of hot air from the resistive grid exhaust. Additionally, the barrier bar retracts from the extended position over the walkway to switch the locomotive out of the self-load mode into a normal mode to shut off the supply of hot air from the resistive grid through the resistive grid exhaust to permit the operator to safely walk in front of the resistive grid exhaust. 
   In another embodiment of the present invention, a locomotive control system is provided for a locomotive. The locomotive includes a normal mode for supplying electrical current from an engine and alternator to drive traction motors to propel the locomotive. The locomotive also includes a self-load mode for supplying electrical current from the engine and alternator to a resistive grid while the locomotive is stationary. The locomotive control system includes a controller coupled to a barrier bar switch for selectively isolating the resistive grid from the engine and alternator and switching out of the self-load mode into the normal mode based upon receiving an engaged signal from the barrier bar switch upon the barrier bar engaging the barrier bar switch. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1  is a perspective view of a locomotive in a self-load mode. 
       FIG. 2  is a perspective view of a locomotive in a normal mode. 
       FIG. 3  is an exemplary partial side view of a locomotive. 
       FIG. 4  is a partial cross-sectional view of the locomotive of  FIG. 1  along the line  4 - 4 . 
       FIG. 5  is a block diagram of the locomotive control system for the locomotive of  FIG. 1 . 
       FIG. 6  is a plan view of an exemplary locomotive control system including a control circuit related to a resistive grid coupled to a locomotive controller. 
       FIG. 7  is a partial block diagram of an exemplary locomotive control system including a locomotive controller coupled to a barrier bar switch. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a locomotive  10  including an embodiment of a safety system  16  for a walkway  18  of the locomotive. The safety system  16  illustratively includes an operator cabin  20  adjacent to a front end  12  of the locomotive  10 . A walkway  18  extends from the operator cabin  20  along a first side  14  of the locomotive  10  to facilitate a locomotive operator  22  performing regular maintenance on the locomotive. As shown in  FIG. 3 , the locomotive operator  22  may perform such regular maintenance on the walkway  18 , or may descend a ladder  19  to perform the regular maintenance of the locomotive while standing on the ground. The second side of the locomotive (not shown) opposite from the first side  14  may not include a ladder to provide such ground access. 
   A resistive grid exhaust  24  is illustratively positioned within the sidewall  15  of the first side  14  of the locomotive  10 . The resistive grid exhaust  24  directs hot air along a path  26  ( FIG. 4 ) from a resistive grid  28  within the sidewall  15  to external the locomotive  10  during a self-load mode of the locomotive. As illustrated in  FIG. 1 , the hot air directed away from the resistive grid exhaust  24  during the self-load mode passes over the walkway  18 . A barrier bar  30  is positioned adjacent to the base  38  of the resistive grid exhaust  24 , and is extendable to an extended position  40  ( FIG. 1 ) over the walkway  18  during the self-load mode. By extending to the extended position  40  during the self-load mode, the barrier bar  30  prevents the operator  22  from walking into the path  26  of the hot air from the resistive grid exhaust  24 , which may cause personal injury to the operator. The barrier bar  30  may retract from the extended position  40  ( FIG. 2 ) over the walkway  18  to switch the locomotive  10  out of the self-load mode and into a normal mode to shut off the supply of the hot air from the resistive grid  28  through the resistive grid exhaust  24 . By retracting from the extended position  40  and switching the locomotive  10  to the normal mode, the barrier bar  30  permits the operator  22  to safely walk down the walkway  18  and in front of the resistive grid exhaust  24 .  FIG. 2  illustrates the barrier bar  30  in a fully retracted position  41 , such that a negligible amount of the barrier bar extends over the walkway  18 . However, the fully retracted position may be any position of the barrier bar such that there is no substantial obstruction to the operator  22  walking down the walkway  18  and passing the resistive grid exhaust  24 . The barrier bar  30  may be retracted from the extended position  40  by the operator  22  physically shifting the barrier bar inward toward the sidewall  15 , or automatically upon the locomotive shifting from the self-load mode to the normal mode, based upon a locomotive controller. 
   The barrier bar  30  is illustratively centered with the resistive grid exhaust  24  upon extending to the extended position  40  and retracting to the fully retracted position  41 , as shown in respective  FIGS. 1 and 2 . The overall width of the barrier bar  30  is at least equal to the width of the resistive grid exhaust  24 . Since the hot air passing out of the resistive grid exhaust  24  would be felt by an operator  22  standing at the respective sides of the resistive grid exhaust, the overall width of the barrier bar is preferably larger than the resistive grid exhaust, as shown in  FIGS. 1 and 2 . As best illustrated in  FIG. 4 , the barrier bar  30  in the extended position  40  is substantially perpendicular to the sidewall  15  of the first side  14  of the locomotive  10 . However, the barrier bar in the extended position may be oriented other than substantially perpendicular with the sidewall  15  of the first side  14  of the locomotive  10 , provided that the barrier bar in such extended position prevents the operator  22  from walking into the path of the hot air from the resistive grid exhaust  24  during the self-load mode. Although  FIGS. 1 and 2  illustrate one resistive grid exhaust and barrier bar on the first side of the locomotive, the safety system embodiment of the present invention would accommodate a plurality of resistive grid exhausts and corresponding barrier bars along the first side, or both sides of a locomotive, as appreciated by one of skill in the art. 
   As illustrated in  FIG. 4 , a barrier bar switch  44  engages the barrier bar  30  when the barrier bar retracts from the extended position  40 . The barrier bar switch  44  further disengages the barrier bar  30  when the barrier bar extends to the extended position  40 . The barrier bar  30  illustratively extends from a respective slot  50  within the sidewall  15  of the first side  14 . The slot  50  slidably receives the barrier bar  30  when the barrier bar retracts from the extended position  40 , and slidably receives a portion  54  of the barrier bar switch to engage an adjacent portion  52  of the barrier bar upon the barrier bar retracting from the extended position. The safety system embodiment of the present invention includes other coupling structures between the barrier bar and the barrier bar switch from the extended position to retracting from the extended position, in addition to the slot structure illustrated in  FIG. 4 , for example. Such coupling structures are arranged such that the barrier bar switch disengages the barrier bar when the barrier bar extends to the extended position, and engages the barrier bar when the barrier bar retracts from the extended position. 
   The barrier bar  30  illustratively forms a u-shape with a hollow center. The barrier bar  30  includes a first bar  32  and a second bar  34 , aligned mutually parallel and substantially perpendicular to the sidewall  15  of the first side  14  when the barrier bar  30  is in the extended position  40 . The first and second parallel bars  32 , 34  are separated by a distance at least equal to the width of the resistive grid exhaust  24 . A third bar  36  is illustratively aligned substantially perpendicular with the first and second bars  32 , 34  and substantially parallel with the sidewall  15  of the first side  14 . The third bar  36  has a length at least equal to the width of the resistive grid exhaust  24 . The third bar  36  is integrated with the first and second bars  32 , 34  at a first end of the first bar and a first end of the second bar opposite from the sidewall  15  of the first side  14  when the barrier bar  30  is in the extended position  40 . The barrier bar may take any form which prevents the operator  22  from walking into the path of the hot air from the resistive grid exhaust  24  during the self-load mode when the barrier bar is in the extended position. 
   The barrier bar  30  may be comprised of a metallic substance, or any material appreciated by one of skill in the art. The barrier bar  30  in the extended position  40  is capable of supporting the weight of the operator  22 , particularly in the event that the operator needs to use the barrier bar for stability in avoiding the hot path of air from the resistive grid exhaust  24 . In an exemplary embodiment of the barrier bar  30 , the barrier bar in the extended position may be capable of supporting the weight of a 400 lb operator. 
   Another embodiment of the present invention includes a locomotive control system  116  for a locomotive  10  having a normal mode for supplying electrical current from an engine and alternator (ie. current source  60 ) to drive traction motors to propel the locomotive.  FIG. 5  illustrates an exemplary embodiment of a locomotive system  116  of the present invention. The locomotive control system  116  further includes a self-load mode for supplying electrical current  58  from the engine and alternator (ie. current source  60 ) to a resistive grid  28  while the locomotive is stationary. The braking switches  64 , 66 , and  68  are configured for the normal mode, but the motor/brake switches  70 , 72  have opened to disconnect the traction motor from the current source  60 . A self-load switch  74  is closed to connect the resistive grids  28  to the current source  60 . The current source  60  and the resistive grids  28  may now be tested without moving the locomotive  10 . The locomotive control system  116  includes the resistive grid exhaust  24  continuous with the resistive grid  28  and the barrier bar  30 , as discussed above. 
   As illustrated in the exemplary embodiment of  FIG. 5 , the locomotive control system  116  further includes a controller  46  coupled to the barrier bar switch  44  for selectively isolating the resistive grid  28  from the engine and alternator (ie. current source  60 ) and switching out of the self-load mode into the normal mode based upon receiving an engaged signal from the barrier bar switch upon the barrier bar  30  engaging the barrier bar switch  44 . As illustrated in  FIGS. 5 and 7 , the controller  46  permits the hot air to be directed along the path  26  through the resistive grid exhaust  24  and maintains the self-load mode based upon receiving a disengaged signal  48  from the barrier bar switch  44  at a digital input  47 . An exemplary embodiment of a resistive grid  28  coupled to a controller  46  is illustrated in  FIG. 6 . 
   This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.