Patent Publication Number: US-11661094-B2

Title: Reverse angled point slider

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119 of Provisional Application Ser. No. 62/674,523, filed May 21, 2018, which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a railroad switch. More specifically, the invention relates to a point slider that accounts for thermal expansion and contraction of rails and points in a railroad switch, allowing proper operation of an indicator. 
     Points are movable section of rail used to direct a rail car along one of two lines at a junction. For example, a set of points could be used at a junction between a mainline and a branch line that diverges from the mainline. To show which track has been selected and to provide confirmation that complete switching of the points has occurred, an indicator rod is connected at one end to the set of points and to a switch machine or detector at the opposite end. In this configuration, the indicator rod mirrors the movement of the points. These components are used as a point indicator, which is a critical component because if the points are not fully switched, derailment of the train can occur. 
     Indicator rods are typically connected to the points at a right angle relative to the length of the track and extend beyond the rails to a switch machine, or detector, adjacent to the track. However, the points and other section of rail can expand and contract due to fluctuations in temperature. Any increase in length of the point will cause the angle of connection between the point and indicator rod to deviate from roughly 90 degrees, since the switch machine is in a fixed location and cannot move with the expanding points. 
     Others have attempted to mitigate the potential misalignment caused by thermal expansion by providing a sliding mechanism at the connection between the point and the indicator rod. However, these attempts have failed to account for the change in the distance between the switch machine and the point as the indicator rod slides along the connection to the point or angled stock rail. That is, a change in length of the distance between the switch machine and point occurs because the point or angled stock rail are tapered and moving along the length of this taper causes the indicator rod to be wedged towards or away from the detector. The length of the indicator rod—or more specifically, the horizontal displacement of the indicator rod along a line perpendicular to the rail—is used to indicate complete switching of the point. As such, a change in length of the indicator rod not related to a horizontal movement of the set of points can become problematic. Therefore, it would be advantageous to develop a point indicator that accounts for thermal expansion while maintaining sensitivity to horizontal displacement. 
     BRIEF SUMMARY 
     According to embodiments of the present invention a point indicator mechanism comprising an angled slider at a connection between the point and the indicator rods. 
    
    
     
       BRIEF SUMMARY OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG.  1    shows the angled slider according to one embodiment. 
         FIG.  2    is an alternative view of the angled point slider. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a railroad switching apparatus  100  according to one embodiment. As shown in  FIG.  1   , the switching apparatus  100  comprises a stock rail  110 , an angled stock rail  111 , a left-hand point  112 , a right-hand point  113 , a front rod  120 , a lockrod connecting rod  121 , a point detector connecting rod  122 , a switch machine  123 , a switch rod  130 , a set of rollers  131 , and a pair of interconnecting blocks  132 ,  133 . The front rod  120  is connected to the lockrod connecting rod  121 , which can be moved in a direction roughly perpendicular to the stock rail  110  by the switch machine  123  to move both the left-hand point  112  and the right-hand point  113 . As the points  112 ,  113  move, the point detector connecting rod  122 , which is also connected to the points  112 ,  113 , moves in a similar manner. 
     Detection of the movement of the point detector connecting rod  122  in the switch machine  123  can be used to indicate the position of the points  112 ,  113  and whether complete movement of the points  112 ,  113  has occurred. For example, during a switching movement, a rock from the ballast under the rail ties can be lodged between one of the points  112 ,  113  and one of the stock rails  110 ,  111 , preventing the points  112 ,  113  from sitting flush against the stock rails  110 ,  111 . If the gap is sufficiently large, a railcar risks derailing as is passes through the switch  100 . The point detector connecting rod  122  is used to help identify such a condition before the railcar passes through the switch  100 . 
     In certain situations, thermal expansion of the points  112 ,  113  can cause misalignment of the point detector connecting rod  122 . For example, as the points  112 ,  113  move in a direction parallel to the stock rails  110 ,  111  due to thermal expansion or from the flange of train wheels pushing the points  112 ,  113 , one of the points  112 ,  113  will slide along the stock rail  110  or angled stock rail  111 . In the embodiment shown in  FIG.  2   , the right-hand point  113  is sliding on the angled stock rail  111 . As the point  113  moves along the angled stock rail  111 , it experiences a displacement towards the stock rail  110  (i.e. towards the center of the track) caused by the angle or taper of the tapered stock rail  111 . 
     In a typical switching apparatus, the switch rod, front rod, point detector connecting rod and lock rod connecting rod would be bolted directly to the points themselves; as a result, in a typical switch apparatus, when the point experiences movement in a direction parallel to the stock rail, the switch rod, front rod, point detector connecting rod and lock rod connecting rod would move wherever the point moves. This typical movement could have two negative effects on the point detector connecting rod and lock rod connecting rod. First, the rods could lose their intended angular alignment in relation to the switch machine causing a loss of “indication”; and second, the rods could displace horizontally in relation to the switch machine causing a loss of “indication”. 
       FIG.  1    shows the switch  100  with the points  112 ,  113  in a first position.  FIG.  2    shows the switch  100  with the point  113  extended along stock rail  111  due to thermal expansion, for example. As shown in  FIGS.  1 - 2   , the reverse angled point slider of the present invention eliminates both negative effects by allowing the points  112 ,  113  to move in a direction parallel to the stock rails  110 ,  111  while holding the switch rod  130 , front rod  120 , point detector connecting rod  122 , and lock rod connecting rod  121  from moving in relation to the switch machine  123  by use of guide rollers  131 , female dovetail blocks  132 , and male dovetail blocks  133 . The term ‘dovetail’ is used to describe a female slot that captures a male rail, where the male rail is adapted to slide back and forth within the female slot. While dovetail blocks  132 ,  133  are depicted in this example embodiment, block of varying shape that allow one block to slide within the other can be used. 
     Referring again to  FIGS.  1 - 2   , the female dovetail block  132  is bolted to each point  112 ,  113  and is cut or manufactured so that the sliding surface is parallel to the stock rail  110 ,  111  while the point is closed. The male dovetail block  133  is inserted inside the female dovetail  132  and allowed to slide freely. The switch rod  130  and front rod  120  are both bolted to the male dovetail block  132 . The switch rod  130  is then prevented from moving in a direction along the stock rails  110 ,  111  by way of guide roller assemblies  131 . The guide rollers  131  allow the switch rod  130  to be pushed side to side by the switch machine  123 . Since the switch rod  130  and the front rod  120  are both bolted to the male dovetail blocks  133 , the front rod  120 , point detector connecting rod  122 , and lock rod connecting rods  121  are prevented from moving in a direction along the stock rails  110 ,  111 . Preventing this movement counteracts misalignment in relation to the switch machine  123 . The reverse angle of the female dovetail block counteracts the left or right movement of the switch rod  130 , front rod  120 , point detector connecting rod  122 , and lock rod connecting rod  121 , thereby preventing horizontal displacement. 
     While the disclosure has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modification can be made therein without departing from the spirit and scope of the embodiments. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.