Abstract:
Embodiments of innovative designs and use of switch rods are disclosed. In one particular embodiment, a method of preventing derailment of a train traveling through a previously run-through railroad switch may include installing a railroad switch rod assembly to couple a switch point of a railroad switch with a railroad switch stand. The method may also include configuring a locking mechanism in the railroad switch rod assembly such that, upon a railway vehicle trailing the railroad switch in a first direction, the locking mechanism maintains the railroad switch in a condition that accommodates safe movement of the railway vehicle through the railroad switch in a second direction opposite to the first direction.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to railway equipment. More particularly, the present invention relates to innovative designs and use of switch rods to prevent derailment of a train that reverses through a previously trailed railroad switch. 
     BACKGROUND OF THE INVENTION 
     A railroad switch is a well-known mechanical installation that enables railway trains to be guided from one set of tracks to another set of tracks. 
       FIGS. 1A-1B  show a typical railroad switch located at the intersection of main tracks  101  and secondary tracks  102 . The railroad switch has switch points  104  which are mechanically linked so that they move together when toggled from one position to another. As a train approaches the railroad switch along the main tracks  101  and in the facing-point direction, the train wheels are guided along the route determined by which of the two switch points  104  is connected to the track facing the switch. If the left point is connected, as shown in  FIG. 1A , then the left wheels of the train will be guided along the rail of that point, and the train will diverge to the right onto the secondary tracks  102 . If the right point is connected, as shown in  FIG. 1B , then the right wheels will be guided along the rail of that point, and the train will continue along the main tracks  101 . The mechanical link between the switch points  104  ensures that only one of them may be connected to the facing track at any given time. 
     In  FIG. 1A , if the train travels on the secondary tracks  102  but in the trailing-point direction, when the left point of the switch is connected, the train will continue onto the main tracks  101  without any issue. However, if the train travels on the main tracks  101  in the trailing-point direction, while the left point of the switch is connected, the train wheels will force the switch points  104  to switch to the right to allow the train to continue through on the main tracks. Such trailing of an open switch is referred to as a “run-through.” A similar run-through could occur from the secondary tracks  102  when the switch is configured to allow train movements along the main tracks  101 , as shown in  FIG. 1B . 
     After a railroad switch has been run through, it could be in one of a number of conditions. Assuming the switch is in the condition as shown in  FIG. 1A  before the run-through,  FIGS. 2A-2B  show potential conditions of the switch after the run-through. For example, the switch may return to its previous position as set before the run-through, which is shown in  FIG. 2A . For another example, the switch may be damaged by the run-through and rest in an “in-between” position that connects neither the main tracks nor the secondary tracks, as is shown in  FIG. 2B . Even if the switch remains connected in the run-through position (in this case, switched to the right side like in  FIG. 1B ), the points are usually not tightly closed or locked in that position. 
     These post-run-through switch conditions may be problematic if a train somehow moves in reverse through the switch. For example, if the switch is damaged and remains in an “in-between” position as shown in  FIG. 2B  (or otherwise not securely closed or locked in the run-through position), the train wheels moving in reverse (i.e., in facing-point direction) will not be properly guided by the switch, which could cause derailment of the train. Even if the switch has returned to its pre-run-through position as shown in  FIG. 2A , the reversing train could travel too fast for the switched curve to the secondary tracks, again potentially causing derailment. 
     In view of the foregoing, it may be understood that there are significant problems and shortcomings associated with current railroad switches. 
     SUMMARY OF THE INVENTION 
     Embodiments of innovative designs and use of switch rods are disclosed. In one particular embodiment, a method of preventing derailment of a train traveling through a previously run-through railroad switch may include installing a railroad switch rod assembly to couple a switch point of a railroad switch with a railroad switch stand. The method may also include configuring a locking mechanism in the railroad switch rod assembly such that, upon a railway vehicle trailing the railroad switch in a first direction, the locking mechanism maintains the railroad switch in a condition that accommodates safe movement of the railway vehicle through the railroad switch in a second direction opposite to the first direction. 
     In another embodiment, a detent assembly may be provided in the locking mechanism to restrict movement of a switch rod of the railroad switch rod assembly. In an alternative embodiment, at least one shear pin may be provided in the locking mechanism, the at least one shear pin configuring at least one spring to initially maintain the railroad switch in a first operating state and, when the at least one shearing pin breaks due to the run-through by the railway vehicle, to maintain the railroad switch in a second operating state. 
     In another particular embodiment, a railroad switch rod assembly may include a switch rod housing having a first end adapted to couple with a railroad switch stand, the switch rod housing further having a second end adapted to slidably receive a connecting rod into the switch rod housing. The railroad switch rod assembly may also include a detent assembly coupled to the switch rod housing, the detent assembly comprising a detent pin. The railroad switch rod assembly may further include the connecting rod, one end of the connecting rod being adapted to couple with a switch point of a railroad switch, the connecting rod having (a) a first notch to receive a tip of the detent pin in a first operating state of the railroad switch to maintain a first relative position of the connecting rod in the switch rod housing and (b) a second notch to receive the tip of the detent pin in a second operating state of the railroad switch to maintain a second relative position of the connecting rod in the switch rod housing. 
     In yet another embodiment, a railroad switch system may be made or modified to include any of the above-mentioned embodiments of the railroad switch rod assembly. 
     The present invention will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present invention is described below with reference to exemplary embodiments, it should be understood that the present invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present invention as described herein, and with respect to which the present invention may be of significant utility. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to facilitate a fuller understanding of the present invention, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present invention, but are intended to be exemplary only. 
         FIGS. 1A-1B  show a typical railroad switch known in the art. 
         FIGS. 2A-2B  show potential conditions of a railroad switch after a run-through has occurred. 
         FIG. 3  shows a diagram illustrating a desired state of a railroad switch after a run-through in accordance with an embodiment of the present invention. 
         FIG. 4  shows an exemplary switch rod assembly in accordance with an embodiment of the present invention. 
         FIG. 5  shows a switch rod housing and a spring housing of an exemplary switch rod assembly in accordance with an embodiment of the present invention. 
         FIG. 6  shows a connecting rod of an exemplary switch rod assembly in accordance with an embodiment of the present invention. 
         FIG. 7  shows a cross-sectional view of an exemplary spring detent assembly and its coupling to the rest of a switch rod assembly in accordance with an embodiment of the present invention. 
         FIG. 8  shows an exemplary spring detent pin in accordance with an embodiment of the present invention. 
         FIGS. 9A-9B  show side views of an exemplary detent pin and connecting rod in accordance with an embodiment of the present invention. 
         FIGS. 10A and 10B  show top and side views respectively of an exemplary switch rod assembly and its installation with a test stand in accordance with an embodiment of the present invention. 
         FIGS. 11A-11D  show different operating states of an exemplary switch rod assembly in accordance with an embodiment of the present invention. 
         FIGS. 12 and 13  show the design and operation of another exemplary switch rod assembly in accordance with an alternative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention provide for innovative designs and use of switch rods to prevent derailment of a train that traverses through a previously trailed railroad switch. In light of uncertain, and sometimes dangerous, conditions of the railroad switch after it has been run through by a trailing train, the inventor finds it desirable to have a switch that securely maintains or locks the switch points in the position forced by the run-through, rather than reverting to the position set before the run-through (or to any other position). A mechanism is therefore provided in the switch rod to accommodate a run-through and thereafter automatically cause the switch to remain in the same condition forced by the run-through. As a result of the design and use of the inventive switch rod assembly, the non-ideal conditions of the post-run-through railroad switch can be avoided, thereby eliminating or reducing the risk of derailment when a train attempts to traverse through a previously trailed railroad switch. 
     Other features and advantages of the present invention may be appreciated from the following illustration and description. 
     Referring to  FIG. 3 , there is shown a diagram illustrating a desired state of a railroad switch after a run-through in accordance with an embodiment of the present invention. Continuing with the example shown in  FIG. 2A , it is assumed that a train has run through a railroad switch along main tracks  101  in the trailing-point direction as shown. The railroad switch according to the present invention will be so designed and/or configured to cause the switch points to remain locked in the run-through direction such that no derailment would occur if the same train backs up or another train comes in the opposite (facing-point) direction through the switch. 
     A number of methods may be effective in causing the switch points to be locked in place after a run-through. According to embodiments of the present invention, it may be desirable to provide a locking mechanism in the switch rod that couples the switch points to the switch stand. Preferably, only the switch rod needs to be replaced or modified without making any change to the rest of the railroad switch components. 
       FIG. 4  shows an exemplary switch rod assembly in accordance with an embodiment of the present invention. The switch rod assembly  400  may comprise a switch rod housing  402 , a detent assembly  404 , and a connecting rod  406 . Details of these main components are shown in more detail in  FIGS. 5-8 . 
     As shown in  FIGS. 4 and 5 , the switch rod housing  402  may be primarily a cylindrically shaped component with a hollow cavity to receive the connecting rod  406 . The connecting rod  406  may be coupled to the switch rod housing  402  via a seal plate  407  attached to a first flange  511  at one end of the switch rod housing  402 . The detent assembly  404  may have a cylindrically shaped housing  504  that is coupled to the switch rod housing  402  via a cubic joint  508 . A top plate  405 , attached to a second flange  513 , may serve to secure the detent assembly  404  in its housing  504 . 
     The switch rod assembly  400  may be designed to replace an existing switch rod for a railroad switch assembly without requiring modifications to the rest of the railroad switch assembly or its switch stand. Accordingly, one end of the switch rod housing  402  is adapted, for example, in the shape of a fork  403  with screw or bolt holes, to couple with part of a switch assembly (not shown here); the other end ( 409 ) of the connecting rod  406  is adapted to couple with a switch stand of a railroad switch (not shown here).  FIG. 10A  shows a top view, and  FIG. 10B  shows a side view, of an exemplary switch rod assembly  1002  and its installation with a test switch stand  1006  in accordance with an embodiment of the present invention. As shown, the right end of the switch rod assembly  1002  is coupled to a railroad switch assembly  1004  while the left end of the switch rod assembly  1002  is coupled to the switch stand  1006 . 
       FIG. 6  shows a connecting rod of an exemplary switch rod assembly in accordance with an embodiment of the present invention. The connecting rod  406  may be a rigid, elongated and cylindrically shaped member. As is also well known in the art, the general dimensions of the connecting rod  406  may be so configured as to fit snuggly within and be able to slide along a corresponding switch rod housing (e.g.,  402 ). One end ( 409 ) of the connecting rod  406  may be adapted to couple with a railroad switch assembly, for example, to move its switch point. Towards the other end (i.e., the end that is inserted into the switch rod housing), two or more notches may be formed on the connecting rod  406 . A first notch,  601 , may have a first profile and be located at a first position on the connecting rod  406 . At least one second notch,  602  or  603 , may have a second profile and be located at a second position on the connecting rod  406 . The profiles and relative positions of these notches are configured to work with a detent assembly, as will be described in more detail below. Between the first notch  601  and the at least one second notch  602  or  603 , the connecting rod  406  may be contoured to provide a channel to guide the relative movement of a detent pin, as will also be described in more detail below. 
       FIG. 7  shows a cross-sectional view of an exemplary spring detent assembly and its coupling to the rest of a switch rod assembly in accordance with an embodiment of the present invention. The spring detent assembly  700  may include a detent pin  800 , a bolt  704 , and a spring  702 , which are enclosed in a detent housing  504 . The detent housing  504  may be attached to the switch rod housing  402  via the cubic joint  508  such that the center axis of the two housings are preferably perpendicular to each other. An opening in a sidewall of the switch rod housing  402  may allow at least a portion of the tip of the detent pin  800  to pass through. The spring  702  exerts a downward tension on the detent pin  800  to cause its tip to protrude through the sidewall opening of the switch rod housing  402 . 
     Inside the switch rod housing  402  is slidably positioned the connecting rod  406 . The notches  601 - 603  on the connecting rod  406  may be on the same side as the sidewall opening. As shown in  FIG. 7 , the first notch  601  is position at the sidewall opening now. The spring-tensioned detent pin  800  protrudes through the sidewall opening and has its tip engaged with the first notch  601 . As shown in  FIG. 8 , the size and contour of the tip of the detent pin  800  may be so defined as to fit within the first notch  601  and press against its sidewalls to stop relative movement of the connecting rod  406  in the switch rod housing  402 . The contours of the tip of the detent pin  800  and sidewalls of the first notch  601  may be further configured as to allow a significant force exerted along the connecting rod  406  to disengage the detent pin  800  from the first notch  601  and to cause the detent pin  800  to slide relative to the connecting rod  406 . One example of such a significant longitudinal force may be the one caused by a train trailing through an open railroad switch. That is, the run-through may “kick” the connecting rod  406  loose from the detent pin  800  and cause it to move relative to the connecting rod towards the second notch  603 . It should be noted that the specific size and contour shown in  FIG. 8  are exemplary and do not represent the only design option contemplated for the present invention. 
     According to an embodiment of the present invention, the second notch  603  may be located a distance D away from the first notch  601  wherein the distance D is approximately the same as the travel distance of the switch point of the railroad switch when it is toggled from one state to the other (e.g., from “fully open” to “fully closed”). Accordingly, when a run-through train forces the railroad switch into a different state, for example, by jerking the connecting rod  406  to the left, the detent pin  800  will be knocked out of the first notch  601  and finally land in the second notch  603 . As shown in  FIG. 7 , the sidewall of the second notch  603  on the right hand side is relatively steep and may fully stop the connecting rod  406  from traveling any further to the left. By engaging the second notch  603  with the detent pin  800 , the connecting rod  406  can securely maintain the railroad switch in the same run-through position. 
     This operation is illustrated more clearly in  FIGS. 9A-9B .  FIG. 9A  shows a side view of the exemplary detent pin  800  and connecting rod  406  when the railroad switch is in a first operating state. At this moment, the detent pin  800  engages with the first notch  601  to hold the switch in a normal condition. The first notch  601  may mark the reset (or normal operational) position of the detent pin  800 . The force applied by the train wheels during the run-through is sufficient to knock the tip of the detent pin  800  out of the first notch  601  and therefore causes the connecting rod  406  to slide to the left hand side until the detent pin  800  is stopped by the second notch  603 .  FIG. 9B  shows a side view of the exemplary detent pin  800  and connecting rod  406  when the railroad switch is locked in this second operating state after the run-through. The notch  603  may mark the right-lock position of the detent pin  800 . While, in this example, the run-through train forces the connecting rod  406  to move to the left, the same principle of operation applies when the connecting rod  406  is forced to the right hand side by a run-through train. In that case, the notch  602  located to the left side of the first notch  601  may accommodate and stop the detent pin  800 . The notch  602  may mark the left-lock position of the detent pin  800 . 
       FIGS. 11A-11D  show different operating states of an exemplary switch rod assembly in accordance with an embodiment of the present invention. In these drawings, the setup illustrated in  FIGS. 10A-10B  is presented in cross-sectional views to show how the switch rod assembly  1002  is used and operates in connection with the test switch stand  1006  and the switch assembly  1004 . 
       FIG. 11A  shows the switch rod assembly  1002  in its normal operational state when the detent pin is engaged in the reset position. The switch rod assembly  1002  now may function like a conventional switch rod. Routine toggling of the switch assembly  1004  by operating the switch stand  1006  will not affect the position of the detent pin. Thus, the entire length of the switch rod assembly  1002  remains the same during normal operations. 
       FIG. 11B  shows the switch rod assembly  1002  in what is referred to as a “detent short” state when the detent pin is dislodged from the reset position and rests in the left-lock position. This may be due to a run-through of the switch assembly  1004  which forces the connecting rod to move to the right relative to the switch rod housing. As shown in  FIG. 11B  (and in  FIG. 11D ), the maximum travel that the switch point can move is approximately five inches according to this embodiment. 
       FIG. 11C  shows the switch rod assembly  1002  after it is returned to the operational state. The notch profile at the left-lock position ( FIG. 11B ) may allow connecting rod to be pulled to the left, thereby causing the detent pin to be re-engaged in the reset position. 
       FIG. 11D  shows the switch rod assembly  1002  in what is referred to as a “detent long” state when the detent pin is dislodged from the reset position and rests in the right lock position. This may be due to a run-through of the switch assembly  1004  which forces the connecting rod to move to the left relative to the switch rod housing. 
       FIGS. 12 and 13  show the design and operation of another exemplary switch rod assembly in accordance with an alternative embodiment of the present invention. As shown in  FIG. 12 , this alternative design of switch rod assembly may include a main body tube  1  that accommodates an extension rod end  2  on the switch stand side and a compression rod end  5  on the switch point side. Spring(s)  10  may be used to configure the switch rod in a predetermined state while shear pin(s)  8  may maintain the switch rod in that (“loaded”) state. When a run-through occurs, the switch rod will experience a significant longitudinal force which causes the shear pin(s)  8  to be broken and thereby release the compressed/extended spring(s)  10 . As a result, the spring(s)  10  may cause the switch rod to stay in the run-through direction even after the train has completely passed the switch location. 
     For example, in the normal state (“loaded view”) shown in  FIG. 13 , the spring  10  on the extension rod end may by kept fully compressed (due to the corresponding shear pin  8 ), whereas the spring  10  on the compression rod end may by kept fully extended (also due to the corresponding shear pin  8 ). If the run-through train exerts a force that moves the switch point towards the switch stand (that is, compressing the switch rod overall), then at least the shear pin  8  on the compression rod end would break and cause the corresponding spring  10  to compress to its natural length, thereby causing the switch rod to stay in the broken state (“tripped view”) shown in  FIG. 13 . 
     It should be noted that the above-described switch rod assembly need not be one that is constructed complete from scratch. Where applicable, some existing switch rods could be modified (“retrofitted”) based on the operating principles described herein. 
     While the foregoing description includes many details and specificities, it is to be understood that these have been included for purposes of explanation only, and are not to be interpreted as limitations of the present invention. It will be apparent to those skilled in the art that other modifications to the embodiments described above can be made without departing from the spirit and scope of the invention. Accordingly, such modifications are considered within the scope of the invention as intended to be encompassed by the following claims and their legal equivalents.