Abstract:
The invention relates to an interface pad comprising a stiffener supporting a resilient pad to cushion the panels in a grade crossing between and around the rails from impact with the underlying ties and to prevent the panels from moving. The pad may be flat or a cupped shape and may be of varying size to accommodate varying tie widths. The invention further comprises means to securely fasten such an interface pad to a railroad tie and minimize the possibility that the interface pad will be forcibly removed from the tie during installation of the rails or panels in the grade crossing.

Description:
FIELD OF THE INVENTION 
     This invention relates to an apparatus used in railway grade crossings, specifically an interface pad to cushion the panels between and around the rails against impact and abrasion with the underlying ties and to provide uniform panel support. The invention also relates to simplifying installation of such interface pads in a railway grade crossing. 
     BACKGROUND OF THE INVENTION 
     In a grade crossing (also called a level crossing), gaps in the roadway around the railway tracks are filled in with large panels, which rest on wood or concrete ties and are approximately flush with the railheads. As vehicles pass over the crossing, the panels experience significant loading and will deflect downwardly. If a panel is not resting directly on a tie, which happens in situations where tie dimensions are not uniform, that deflection may push the panel sharply against the top surface of the tie, possibly damaging the panel, the tie or both. Repeated uncushioned impacts can eventually cause failure of the panel or tie. 
     It is therefore preferable to have a protective cushioning means between the panels and the ties, to act as both a shock absorber and to help absorb normal support surface variations. An interface pad is designed to cushion and support the panels and to compensate for any irregularities in the top surface of the tie that might otherwise provide a point of impact when the panels deflect against the ties as vehicles pass over. 
     U.S. Pat. No. 5,626,289 to Demers Jr. et al. discloses a grade crossing, and briefly refers to “known” interface pads for use between the tie and the panels, without providing any real details of the pads. Similarly, U.S. Pat. No. 4,449,666 to Hales et al. discloses a layer of elastomeric compound to separate the panels of a grade crossing from the ties, to provide flexibility to the panels and allow to adjustment of the height of the panels relative to the rail heads. However, not much more detail about the pad itself is provided. 
     It is known to simply place an elongated (i.e. covering substantially all of the exposed areas of the tie) interface pad over a tie once the tie is in place under a track. The drawback to this is that it creates an additional step in the installation process, as each pad, known as a conformal pad, must be hand-placed on each tie during installation. Further, because there is no physical connection between the pad and the tie, it is is difficult to ensure that the pads stay in place as the ties are installed under the rails, or as panels are installed on the ties because these situations generally require the ties or panels to be moved sideways, such that the rails or panels slide over the top surface of the ties. These sliding motions will tend to scrape any loose pads off the top of the tie. 
     These drawbacks have been addressed by creating shaped interface pads that interact with multiple surfaces of the tie, providing an improved fit between the tie and the pad. For example, U.S. Pat. No. 6,422,478 to Lucas Jr. and Canadian Patent No. 2281110 to Bruyn both show tie pads that are carefully shaped and engineered not only to provide cushioning pockets within the body of the interface pads, but also to fit over the top chamfers of a concrete tie, keeping the pad in place through friction and cooperation with the tie. Similarly, US Pat. App. No. 2007/0200005 to Corbett Jr. et al. describes several means to attach the pads to the tie, such as wrapping around the chamfered edges of the tie, direct attachment to the panels, and physical abutment with rail attachment hardware, ballast or roadway, but does not discuss mechanically fastening the pads to the ties. The main drawback to these shaped interface pads is that they do not address the issues of increased installation time for placing one or more pads on each tie during installation or of potential loss of the unsecured pads during or after installation. 
     In order to directly deal with this issue, it is known to glue an elongated interface pad, or one or more smaller interface pads, on top of the tie before shipping the tie to the installation site. However, glued-on interface pads are still highly susceptible to displacement during shipping or at any one of several points in the process involved in constructing grade crossings, which wastes money and materials. 
     More secure methods of connecting interface pads to ties have not gained widespread use, possibly because of the difficulties or costs associated with placing mechanical fasteners, such as bolts, into the top of a concrete tie. Further, simply bolting a flat rubber pad into the top of a tie still may not ensure that the pad stays in place during is installation, as the rubber pad can be torn off over the fastener if it is pulled with sufficient force. 
     It is therefore an object of the invention to provide an interface pad, specifically for use at grade crossings that overcomes one or more of the foregoing difficulties. 
     In particular, it is an object of the invention to provide a pre-attached interface pad for a grade crossing that eliminates the need to ship loose conformal pads to the site as well as on-site handling and installation of those conformal pads. 
     It is a further object of the invention to provide an interface pad that is mechanically attached to a tie, in order to eliminate undesirable movement of the pad during shipping, installation and service. 
     It is a further object of the invention to provide an interface pad that is manufactured and shaped for secure installation on a tie in a grade crossing. 
     These and other objects of the invention will be appreciated by reference to the summary of the invention and to the detailed description of the preferred embodiment that follow. 
     SUMMARY OF THE INVENTION 
     The interface pad of the invention is a two-piece system comprising a stiffener supporting a resilient cushioning pad made of a durable, elastic material. Preferably the stiffener is manufactured first, and then the resilient pad is molded onto the stiffener. The resilient pad may be divided into discrete quarters or other fractions, which helps to eliminate undesirable pad deformation during manufacture. The outer edges and corners of the resilient pad are preferably given a chamfered, beveled or rounded shape, or any shape suitable to minimize sharp or protruding parts, in order to minimize the chance that a corner or edge of the interface pad will catch on something during is transport or installation and be torn or scraped off the tie. 
     In an alternative embodiment, the stiffener may be encompassed substantially within the resilient pad. Preferably the stiffener is manufactured first, and then the resilient material is molded around the stiffener. In this embodiment, the stiffener may be a plate, in which case the features and functions of this embodiment of the invention are similar to those described in relation to the first embodiment. Alternatively, the stiffener may be shaped, such as in a cupped piece substantially within the resilient pad, to provide different footprints for the interface pad, which may be useful in different grade crossing situations. 
     The interface pad is designed to be easily mechanically attached to a tie, such as with a fastener through a hole in the pad. The fastener hole is preferably located to accommodate a fastener that can be recessed substantially or completely within the interface pad to prevent the installed fastener from interfering with the panel. The tie itself preferably has a slight recess to accommodate the interface pad, reducing the overall profile of the interface pad once it is in place on a tie, thereby minimizing the potential for displacement of the pad during handling and installation, particularly by the rails or the grade crossing panels sliding over the top surface of the tie. 
     In one aspect, the invention comprises an interface pad for a tie in a railway grade crossing, the interface pad having an underside to be located proximate the tie and an upper side opposed to the underside, and further comprising a stiffener; a resilient pad supported by said stiffener; and at least one fastener passageway through said stiffener and said resilient pad to accommodate a fastener to secure said interface pad to said tie, wherein the passageway may be shaped to allow the fastener to recede substantially below the upper surface of the resilient pad. The stiffener may comprise a substantially flat plate, although the passageway may extend below the underside of the plate. The stiffener may comprise a plurality of pieces, each of the pieces comprising a substantially flat plate. Alternatively, the stiffener may be cupped and located proximate the fastener passageway in a smaller pad. The overall interface pad may be substantially flat, or may be convex in shape. At least one outside edge of said resilient pad may be chamfered, beveled or rounded, and if the interface pad is a shape, such as a quadrilateral, comprising edges separated by corners, the corners may be chamfered, beveled or rounded. 
     In a further aspect, the resilient pad on the interface pad may comprise a plurality of sections divided by at least one channel. 
     In a further aspect, the stiffener may comprise at least one aperture into which the resilient pad protrudes. The aperture may be taper towards the upper side of the resilient pad, relative to the underside of the resilient pad. 
     In another aspect of the invention, the resilient pad of the interface pad may substantially surround the stiffener. In an embodiment wherein the stiffener comprises a substantially flat plate, the resilient pad may comprise layers of resilient material on opposed sides of the plate. The underside of the passageway extending below the substantially flat plate may not be completely within the resilient material. In an embodiment wherein the stiffener is cupped proximate said fastener passageway, the underside of the stiffener may not be completely within the resilient pad. 
     In yet another aspect, the invention comprises a grade crossing tie comprising at least one interface pad as described herein, and further comprising a recess in the tie to accommodate each interface pad. 
     The foregoing was intended as a broad summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiment of the invention will be described by reference to the drawings in which: 
         FIG. 1  is a perspective view of the interface pad of the invention in place on a tie in a typical grade crossing; 
         FIG. 2  is an elevation view of interface pad and grade crossing of  FIG. 1 ; 
         FIG. 3  is a perspective view of a tie bearing interface pads of the invention; 
         FIG. 4  is a perspective view of an interface pad of the invention; 
         FIG. 5  is a sectional view of the interface pad of  FIG. 4 , taken along line A-A; 
         FIG. 6  is a perspective view of a second embodiment of the interface pad of the invention; 
         FIG. 7  is a sectional view of the interface pad of  FIG. 6 , taken along line B-B; 
         FIG. 8  is a plan view of a tie bearing an alternative embodiment of the interface pads of the invention; 
         FIG. 9  is a perspective view of an alternative embodiment of the interface pad of the invention; 
         FIG. 10  is a sectional view of the interface pad of  FIG. 9 , taken along line C-C; 
         FIG. 11  is a perspective view of another alternative embodiment of the interface pad of the invention; and 
         FIG. 12  is a sectional view of the interface pad of  FIG. 10 , taken along line D-D. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-3 , a grade crossing typically includes rails  10  supported on ties  12 . Each rail  10  is fastened to the ties  12  in a standard way, such as with any suitable fastener  14 , and may be seated on a supporting area, such as tie plate  16 . In order to allow vehicular traffic to cross the tracks without damage, one or more panels  18  are placed on each of the field sides of the rails between the roadway and the rails, and one or more gauge side panels  20  are placed between the rails. Preferably the edges of the panels  18 ,  20  are shaped to fit closely around the rails  10 , preventing excessive moisture and debris from penetrating the crossing. Suitable gauge and field seals (not shown) may be placed between the rails  10  and panels  18 ,  20  to further prevent unwanted debris from penetrating the crossing. The panels  18 ,  20  are also preferably similar in height to the rails  10 , minimizing the shock felt by a vehicle passing over the crossing. One or more interface pads  22  are placed at suitable intervals along the tie  12 , providing cushion and support for panels  18 ,  20 . Each interface pad  22  is preferably located in a recess  24  in tie  12 . It will be understood that the number of interface pads  22 , and the location of those pads are shown in  FIGS. 1-3  for illustration only and that the invention is not limited to a specific number of interface pads, nor to any specific location of those pads on a tie. 
     Referring now to  FIGS. 4 and 5 , interface pad  22  is shown as approximately rectangular, although any suitable shape may be chosen. The interface pad  22  as shown includes a resilient cushioning pad  26  supported by a stiffener  28 . The stiffener  28  is preferably made of a suitable material such as steel, glass reinforced nylon, or similar material, such that the composite assembly is stiff enough to resist being pulled off the tie. The stiffener  28  is illustrated and described in these figures as a unitary plate, although it will be understood that an interface pad  22  may alternatively comprise two or more is segments making up stiffener plate  28 , the segments retained as stiffener  28  by connection with resilient pad  26  as described below. 
     Preferably resilient pad  26  is made of a material such as rubber, artificial rubber, polyurethane, or any similarly durable and resilient material of approximately a 60-90 Shore A durometer hardness, such that the resilient pad  26  is durable enough to withstand scraping and pulling that might occur as the tie is being installed and as the grade crossing panels are being installed on the ties, while still being able to cushion and support the panels. 
     To manufacture the interface pad  22 , the stiffener  28  may be produced first, in dimensions corresponding to the width of the rail tie  12  on which it will be disposed. The dimensions may further be selected based on the approximate shape and approximate depth of a recess  24  (shown in  FIG. 2 ) in the tie  12 . The resilient pad  26  may then be molded onto the stiffener  28 . The resilient pad  26  may comprise one relatively smooth, even layer, or it may comprise two or more sections  30 , which may be separated such as by channels  32 . Molding resilient pad  26  in multiple sections  30  may provide advantages during the molding process, such as preventing undesirable curling or buckling of the interface pad  22 . 
     To ensure durable contact between the resilient pad  26  and the stiffener  28 , an adhesive or other suitable bonding agent may be applied between the resilient pad  26  and stiffener  28 . Additionally or alternatively, the stiffener  28  may comprise apertures  34 , best seen in  FIG. 5 , into which the warm resilient material will flow while it is being molded, mechanically interlocking the resilient pad  26  and stiffener  28 , such as with plugs  35 . It will be understood, although  FIG. 5  shows plugs  35  extending completely through apertures  34  and under a portion of stiffener  28 , plugs  35  may or may not extend completely through aperture  34 , and/or may or may not flow underneath the bottom of stiffener  28 . Further, aperture  34  may be tapered or stepped, such that the end  42  of the aperture  34  on the resilient pad  26  side of the stiffener  28  is narrower than the end  44  of the aperture  34  away from the resilient pad  26 . This provides a wedge-shaped plug  35  that is difficult to remove from the aperture  34 . 
     Interface pad  22  may be provided with a passageway  36  to accommodate a fastener at or near the centre of the interface pad, or at any point or points suitable to sufficiently fasten the interface pad  22  on a tie. Preferably the upper portion of the passageway  36  at the top of the resilient pad  26  has a somewhat larger diameter than the lower portion  40  of the passageway  36  where it passes through the stiffener  28 . This change in diameter may be accomplished by any suitable method, such as the shoulder shown in  FIG. 5 , or a taper through the length of passageway  36 . Providing a wider passageway  36  allows room to insert a fastener (not shown), such as a bolt or any other suitable fastening means, through the interface pad  22  and into a tie, such that the fastener head is accommodated substantially within the thickness of the resilient pad  26  and does not protrude substantially above the top surface of the interface pad  22 . Alternatively or additionally, passageway  36  may extend below the level of the rest of the stiffener  28 , again providing a space to accommodate a fastener substantially completely below the upper surface of the interface pad  22 . Combined with the recess  24  (shown only in  FIGS. 1-3 ), this arrangement secures the interface pad  22  to the tie while preventing the fastener from interfering with the grade crossing panels. Further, fastening the interface pad  22  onto the tie with a removable fastener allows for easy replacement of a single pad  22  if necessary, without disrupting the other pads  22  supporting the grade crossing panels. It will be understood that, instead of or in addition to providing the central fastener passageway  36 , a fastener passageway may be provided in one or more of the sections  30 . This may increase the overall strength of the connection between the interface pad  22  and the tie. 
     The recess  24  also allows a slightly thicker interface pad  22  to be installed, for example a ½″ pad instead of a more typical ¼″, providing better cushioning through the grade crossing without significantly increasing the overall height of a tie bearing the installed interface pads  22 . This arrangement minimizes the chances that an interface pad  22  will be scraped off of a tie during shipping or installation of the grade crossing rails or is panels. 
     In an interface pad  22  shaped like a rectangle, as show in the figures, the corners separating the outer edges of the resilient pad  26  are preferably shaped to minimize or eliminate sharp or protruding edges, such as by providing chamfered, beveled or rounded corners, in order to minimize the chances that a corner of the interface pad  22  will catch on something during shipping or installation and be torn off the tie. It will be understood that an interface pad of a shape having corners, such as a triangle, or a square, rectangle or other quadrilateral shape, may preferably have similarly shaped corners. Further, it is preferred that all outer edges of the resilient pad  26  be similarly shaped, also in order to minimize the chances that the resilient pad  26  will catch on something. 
     A second embodiment of the interface pad  22 A is shown in  FIGS. 6 and 7 . This embodiment is structurally similar to that shown in  FIGS. 4 and 5 , except that stiffener  28  is positioned between resilient pad  26  and a second resilient pad  38 . Otherwise, the foregoing description of the interface pad  22  assembly and properties is applicable to the second embodiment  22 A, and similar parts are shown with the same reference numbers as those in  FIGS. 4 and 5 . 
     In any of the foregoing embodiments, the interface pad  22  may be provided with some small degree of curvature, such that the pad  22  itself is slightly convex on the upper side, as best shown in  FIG. 6 . When the pad  22  is installed on a tie using a fastener inserted into passageway  36 , the central portion of interface pad  22  is forced to flatten out, ensuring good contact with the tie  12  in recess  24 . Alternatively or in addition, the upper surface of recess  24  may be formed with some degree of curvature, such that it is convex and more likely to closely fit with the underside of the interface pad  22 . 
     In some situations, it may be preferable to use an interface pad  22  having a smaller footprint. For example, a narrower tie would require a smaller interface pad. An is interface pad with a smaller footprint relative to the size of the fastener has less pad material located some distance away from the fastener. This can increase the inherent stability of the pad, making it more difficult to remove from the tie.  FIG. 8  shows a tie  12  including several smaller interface pads  22 B. Again, it will be understood that the number of interface pads  22 B, and the location of those pads are shown in  FIG. 8  for illustration only and that the invention is not limited to a specific number of interface pads  22 B, nor to any specific locations or configuration of those pads on a tie. 
       FIGS. 9 and 10  show perspective and cross-sectional views of an embodiment of interface pads  22 B having a smaller footprint. In this embodiment, the resilient pad is molded above and below  26 ,  38  stiffener  28 , which is a small plate  28 . Fastener passageway  36  accommodates fastener  46 , which is shown as a bolt, but which may be any suitable fastener. Recess  24  is preferably relatively deep compared to the amount of resilient pad  26  extending above the top surface of tie  12 , in order to accommodate and stabilize the interface pad  22 . Additional support may be provided by concrete anchor  48 , which further assists in retaining fastener  46  against any lateral external forces that might try to remove the interface pad  22  from the tie  12 . 
       FIGS. 11 and 12  show perspective and cross-sectional views of another embodiment of interface pads  22 C having a smaller footprint. In this embodiment, the stiffener  28  has a cupped shaped, positioned around the fastener passageway  36 , providing support and stability directly to the fastener  46  as well as to the interface pad  22 C as a whole. Otherwise, the foregoing descriptions of the interface pad  22  assemblies and properties are applicable to the fourth embodiment  22 C, and similar parts are shown with the same reference numbers as those in the other figures. It will be understood that while the embodiment of the interface pad  22 C is shown as an approximately circular pad, that similar shapes, such as squares, rectangles, ovals or other shapes, particularly pads having rounded, chamfered or beveled edges and/or corners, may also be used. 
     It will be appreciated by those skilled in the art that other variations to the preferred embodiments described herein may be practised without departing from the scope of the invention, such scope being properly defined by the following claims.