Patent Publication Number: US-2023143765-A1

Title: Combined crossing termination shunt and railroad crossing control system

Description:
BACKGROUND 
     1. Field 
     Aspects of the present disclosure generally relate to railroad crossing control systems including railroad signal control equipment such as for example a grade crossing predictor system and a crossing termination shunt. 
     2. Description of the Related Art 
     Railroad signal control equipment includes for example a constant warning time device, also referred to as a grade crossing predictor (GCP) in the U.S. or a level crossing predictor in the U.K., which is an electronic device that is connected to rails of a railroad track and is configured to detect the presence of an approaching train and determine its speed and distance from a crossing, i.e., a location at which the tracks cross a road, sidewalk or other surface used by moving objects. The constant warning time device will use this information to generate a constant warning time signal for a crossing warning device. 
     A crossing warning device is a device that warns of the approach of a train at a crossing, examples of which include crossing gate arms, crossing lights (such as the red flashing lights often found at highway grade crossings in conjunction with the crossing gate arms discussed above), and/or crossing bells or other audio alarm devices. Constant warning time devices are typically configured to activate the crossing warning device(s) at a fixed time, also referred to as warning time (WT), which can be for example 30 seconds, prior to the approaching train arriving at the crossing. 
     Typical constant warning time devices include a transmitter that transmits a signal over a circuit, herein referred to as track circuit, formed by the track&#39;s rails, for example electric current in the rails, and one or more termination shunts positioned at desired approach distances, also referred to as approach lengths, from the transmitter, a receiver that detects one or more resulting signal characteristics, and a logic circuit such as a microprocessor or hardwired logic that detects the presence of a train and determines its speed and distance from the crossing. The approach length depends on the maximum allowable speed (MAS) of a train, the desired WT, and a safety factor. 
     Termination shunts or devices include for example hardwire shunts, wide-band shunts, and narrow-band shunts. Depending on a frequency used and existing ballast conditions at a specific grade crossing, an efficacy of a termination shunt may vary. For example, lower frequencies, e.g. 86 Hz, can create situations where an approach is not fully terminated by the termination shunt, resulting in the system, e.g. predictor and/or motion system, to look beyond the intended point of termination. 
     SUMMARY 
     Briefly described, aspects of the present disclosure relate to a railroad crossing control systems including railroad signal control equipment comprising for example a grade crossing predictor (GCP) system, and a crossing termination shunt utilized within such a railroad crossing control system. 
     A first aspect of the present disclosure provides a combined crossing termination shunt comprising a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency. 
     A second aspect of the present disclosure provides a railroad crossing control system comprising a grade crossing predictor system or grade crossing motion system comprising at least one combined crossing termination shunt, the at least one combined crossing termination shunt comprising a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram illustrating a highway-rail grade crossing warning system at a grade crossing in accordance with an exemplary embodiment of the present disclosure. 
         FIG.  2    and  FIG.  3    are schematic diagrams illustrating first and second embodiments of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure. 
         FIG.  4    and  FIG.  5    are schematic diagrams illustrating third and fourth embodiments of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure. 
         FIG.  6    is a perspective view of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of crossing termination shunts, utilized for example within a railroad crossing control system. 
     The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure. 
       FIG.  1    illustrates a schematic view of a grade crossing warning system  100  at a location in which a road  20  crosses train track  22 . The train track  22  includes two rails  22   a ,  22   b  and a plurality of ties (not shown in  FIG.  1   ) that support the rails. The rails  22   a ,  22   b  are shown as including inductors  22   c . The inductors  22   c  are not separate physical devices but rather are shown to illustrate the inherent distributed inductance of the rails  22   a ,  22   b.    
     A track circuit  40  may comprise a transmitter  43  connected across the rails  22   a ,  22   b  on one side of the road  20  and a receiver  44  connected across the rails  22   a ,  22   b  on the other side of the road  20 . Although the transmitter  43  and receiver  44  are connected on opposite sides of the road  20 , those of skill in the art will recognize that the components of the transmitter  43  and receiver  44  other than the physical conductors that connect to the track  22  are often co-located in an enclosure (which is sometimes referred to in the railroad industry as a bungalow) located on one side of the road  20 . 
     The transmitter  43  and receiver  44  may be connected to a control unit  44 A, which may also be located in the aforementioned enclosure. The control unit  44 A may be connected, and may include logic, for controlling warning devices  47  at the crossing  20 . The control unit  44 A may also include logic (which may be implemented in hardware, software, or a combination thereof) for calculating train speed and constant warning time signals for controlling the warning devices  47 . 
     Also shown in  FIG.  1    are a pair of crossing termination shunts  200 , one on each side of the road  20  at a desired approach distance. The crossing termination shunts  200  may also be referred to as simply shunts. The shunts  200  may be installed in the gravel ballast of the railroad track  22 . For security purposes, the shunts  200  may be completed covered with the gravel ballast and only the connecting wires are visible. In another example, instead of installing the shunts  200  in the gravel ballast, the shunts  200  may be installed in a separate shunt enclosure that is in proximity to the railroad tracks. 
     The shunts  200  may be simple conductors or may be tuned AC circuits configured to shunt a particular frequency being transmitted by the transmitter  43 . The transmitter  43  may be configured to transmit a constant current AC signal at a particular frequency, which may be in the audio frequency range, such as between 50 Hz and 1000 Hz. The receiver  44  may measure the voltage across the rails  22   a ,  22   b , which (because the transmitter  43  generates a constant current) is indicative of the impedance and hence the inductance of the circuit formed by the rails  22   a ,  22   b  and shunts  200 . 
     When a train heading toward the road  20  crosses one of the shunts  200 , the train&#39;s wheels and/or axles act as shunts which essentially shorten the length of the rails  22   a ,  22   b , thereby lowering the inductance and hence the impedance and voltage. Measuring a change in the impedance indicates the distance of the train and measuring the rate of change of the impedance (or integrating the impedance over time) allows a speed of the train to be determined. As the train moves toward the road  20  from either direction, the impedance of the circuit will decrease, whereas the impedance will increase as the train moves away from the receiver  44 /transmitter  43  toward the shunts  200 . 
     The termination shunts  200  include for example hardwire shunts, wide band shunts, or narrow band shunts. Depending on a frequency used and existing ballast conditions at a specific grade crossing, an efficacy of a termination shunt may vary. For example, lower frequencies, e.g. 86 Hz, can create situations where an approach is not fully terminated by the termination shunt, resulting in the system, e.g. predictor and/or motion system, to look beyond the intended point of termination. 
     A not fully terminated approach circuit may be addressed by “doubling” termination shunts at the crossing, i.e. installing a second shunt with the same frequency. Depending on the location, customers either (1) use a shunt enclosure that houses the termination shunts, or (2) the termination shunts are buried in the ballast between the ties. In case of (1) the retrofit installation of a second shunt is simple, if the existing enclosure is large enough. No additional rail connections are necessary. In case of (2), the retrofit installation will require an additional set of rail connections. 
       FIG.  2    and  FIG.  3    are schematic diagrams illustrating a first and a second embodiment of a combined crossing termination shunt  200  in accordance with an exemplary embodiment of the present disclosure. The crossing termination shunt  200  is configured as combined crossing termination shunt and may be utilized in connection with the grade crossing warning system  100  as described with reference to  FIG.  1   . 
     In an exemplary embodiment, the crossing termination shunt  200  combines components and elements of multiple termination shunts, specifically into a single shunt housing or enclosure. The provided combined termination shunt  200  has the same look and feel as a regular shunt, but the improved termination efficacy of two or more discrete shunts. Thus, instead of installing multiple separate shunts, the combined termination shunt  200  provides full and reliable termination of the approach circuit. 
     With reference to  FIG.  2    and  FIG.  3   , the termination shunt  200  comprises a housing  210 , a first printed circuit board (PCB)  220  comprising first circuitry  222  and first rail terminals  224 , a second printed circuit board (PCB)  230  comprising second circuitry  232  and second rail terminals  234 . Simply put, the first PCB  220  with its components  222 ,  224  forms a first shunting device, and the second PCB  230  with its components  232 ,  234  forms a second shunting device, wherein the combined termination shunt  200  incorporates the shunting devices into one termination shunt  200 . The first PCB  220  with components  222 ,  224  and the second PCB  230  with components  232 ,  234  are positioned inside the housing  210 . It should be noted that the combined termination shunt  200  may comprise further PCB s with circuitry and rail terminals, for example a third PCB, according to for example specific requirements of the combined termination shunt  200 , i.e. multiple discrete shunts may be formed within the housing  210 . The circuitry of a termination shunt, such as circuitry  222 ,  232 , comprises a plurality of inductors and capacitors, the interconnection of which determines a nominal frequency of the shunt. 
     In another example, the termination shunt  200  may comprise one ore more header boards positioned in one end of housing. In this case, the circuitry  222 ,  232 , specifically inductors and capacitors, can be connected to a plurality of header terminals that are mounted on the header board(s). Header terminals are enclosed by a cover to seal the interior of housing from the elements. The frequency of the shunt can be determined and varied by (different) connection(s) between the header terminals. 
     The housing  210  is formed or shaped such that it appropriately encloses the shunting components in a space saving manner. The housing  210  can comprise plastic materials and can be made for example from polyvinyl chloride (PVC). 
     Further, the combined termination shunt  200  comprises wire connections  240 , wherein a pair of wire connections  240  is attached to the first rail terminals  224  and the second rail terminals  234 . The pair of wire connections  240  is attached in parallel to the first rail terminals  224  and the second rail terminals  234 . 
     In accordance with the first embodiment illustrated in  FIG.  2   , the wire connections  240  are attached to the rail terminals  224 ,  234  within the housing  210 , wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing  210 . Specifically, first sections  240 A of the wire connections are attached to the first rail terminals  224 , and second sections  240 B are attached to the second rail terminals  234 . Further, the second sections  240 B of the wire connections are coupled with the first sections  240 A internally, e.g. inside the housing  210 . 
     The ends extending outwardly through the housing  210  are configured to be attached/coupled to rails of railroad tracks. Seen from an outside, the combined termination shunt  200  looks like a regular shunting device, but includes multiple shunting components equivalent of two or more discrete shunts, and the wire connections  240 A,  240 B to the multiple discrete shunts, i.e. PCBs  220 ,  230 , are within the housing  210 . 
     In accordance with the second embodiment illustrated in  FIG.  3   , the wire connections  240  are attached to the rail terminals  224 ,  234  within the housing  210 , wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing  210 . First sections  240 A of the wire connections are attached to the first rail terminals  224 , and second sections  240 B are attached to the second rail terminals  234 . Further, the second sections  240 B of the wire connections are coupled to first sections  240 A externally, e.g. outside of the housing  210 . 
     Both embodiments according to  FIG.  2    and  FIG.  3    illustrate a combined termination shunt  200  wherein the first PCB  220  and the second PCB  230  are each embodied as a separate, individual PCB. 
       FIG.  4    and  FIG.  5    are schematic diagrams illustrating a third and a fourth embodiment of a combined crossing termination shunt  200  in accordance with an exemplary embodiment of the present disclosure. The crossing termination shunt  200  is configured as combined crossing termination shunt and may be utilized in connection with the grade crossing warning system  100  as described with reference to  FIG.  1   . 
     The third and fourth embodiment according to  FIG.  4    and  FIG.  5    illustrate a combined termination shunt  220 , wherein the first PCB  220  and the second PCB  230  are embodied as a common, single PCB. 
     Further, the combined termination shunt  200  comprises wire connections  240 , wherein a pair of wire connections  240  is attached to the first rail terminals  224  and the second rail terminals  234 . The pair of wire connections  240  is attached in parallel to the first rail terminals  224  and the second rail terminals  234 . 
     In accordance with the first embodiment illustrated in  FIG.  4   , the wire connections  240  are attached to the rail terminals  224 ,  234  within the housing  210 , wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing  210 . Specifically, first sections  240 A of the wire connections are attached to the first rail terminals  224 , and second sections  240 B are attached to the second rail terminals  234 . Further, the second sections  240 B of the wire connections are coupled to first sections  240 A internally, e.g. inside the housing  210 . 
     In accordance with the second embodiment illustrated in  FIG.  5   , the wire connections  240  are attached to the rail terminals  224 ,  234  within the housing  210 , wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing  210 . First sections  240 A of the wire connections are attached to the first rail terminals  224 , and second sections  240 B are attached to the second rail terminals  234 . Further, the second sections  240 B of the wire connections are coupled to first sections  240 A externally, e.g. outside of the housing  210 . It should be noted that many different locations/configurations of the rail terminals  224 ,  234  are possible, some of which are illustrated in  FIGS.  2 - 5    (rail terminals  224 ,  234  at different sides of the PCBs  220 ,  230 ). 
     In an exemplary embodiment of the present disclosure and with reference to the embodiments of  FIGS.  2 - 5   , the first circuitry  222  and second circuitry  232  are configured for a same frequency. In an exemplary embodiment, the first circuitry  222  and the second circuitry  232  are configured for a frequency between 50 Hz and 1000 Hz. Specifically, the circuitries  222 ,  232  may be configured for a frequency of 86 Hz. In particular lower frequencies, e.g. 86 Hz, may create situations where an approach is not fully terminated by the termination shunt. Lower frequency shunts may be embodiment as so-called narrow band shunts. However, it should be noted that the termination shunt  200  may be embodied for many different frequencies, and/or may be embodied as narrow band shunt or wide band shunt. 
       FIG.  6    is a perspective view of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure, such as for example combined termination shunt  200 . 
     The shunt  200  includes an outer housing  210  which has a cap  212  at one end through which extends the pair of electrical wire connectors  240 , each of which will be connected to one of the rails of a respective section of track. Within housing  210  are the PCBs  220 ,  230 , each of which has a pair of rail terminals  224 ,  234  at one end, wherein wire connectors  240  are coupled to the terminals  224 ,  234 . Further illustrated are a plurality of header terminals  252  each of which are mounted on header board(s)  250  positioned in one end of housing  210 . The header terminals  252  are enclosed by a cover  214  which may be formed of a rubber or rubberlike material so as to seal the interior of housing  210  from the elements. It should be noted that although only PCB  220  and terminals  224  are shown, the combined termination shunt  200  includes at least another PCB  230  with circuitry  232  and terminals  234 . Further, it should be noted that the shunt  200  as illustrated in  FIG.  6    may be embodied as described with reference to  FIGS.  2 - 5   . 
     In use, the shunt  200  may be buried in ballast between rails and the wire connectors  240  may be connected to adjacent rails. In another example, instead of burying the shunts  200  in the gravel ballast, the shunts  200  may be installed in a separate shunt enclosure that is located in proximity to the railroad tracks. Jumpers may be used to connect certain designated header terminals which will determine the nominal frequency of the shunt. The combined crossing termination shunt  200  provides full and reliable termination shunt functionality by incorporating multiple discrete shunting devices, and thus avoids installation of multiple shunts and multiple sets of track connections.