Patent Document

FIELD OF THE INVENTION 
       [0001]    This invention relates to an apparatus used in concrete railway ties, specifically an interface pad to provide a cushion between the ties against impact and abrasion with any overlying parts. The invention also relates to simplifying installation of such interface pads in a concrete tie. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a grade crossing (also called a level crossing), gaps in the roadway around the railway tracks are filled in with large concrete, steel or polymeric 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, for example, 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. 
         [0003]    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. 
         [0004]    It may also be necessary to provide such cushioning between concrete ties and other parts overlying the ties in other railway applications. For example, in a concrete turnout or switch, the rails rest on steel plates that are then connected to the tie. It may be beneficial to provide cushioning between the plates and the ties against any impacts or abrasion. Such interface pads may also be used to cushion trackwork, rails, and/or plates in other railway applications. 
         [0005]    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 for adjustment of the height of the panels relative to the rail heads. However, not much more detail about the pad itself is provided. 
         [0006]    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 difficult to ensure that the pads stay in place as the ties are installed under the rails, or as panels or other overlying parts are installed on the ties, because these situations generally require at least the ties be moved sideways, such that the parts 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. 
         [0007]    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. 
         [0008]    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 or turnouts, which wastes money and materials. 
         [0009]    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 installation, as the rubber pad can be torn off over the fastener if it is pulled with sufficient force. In addition, placement and number of fasteners may be of concern—a fastener near or around the perimeter of the pad may be more secure and stable than a central fastener, but may then require more fastening points and therefore more time to install enough fasteners to properly secure the pad to the tie. 
         [0010]    It is therefore an object of the invention to provide an interface pad, specifically for use in a concrete tie, that overcomes one or more of the foregoing difficulties. 
         [0011]    In particular, it is an object of the invention to provide a pre-attached interface pad for a concrete tie that eliminates the need to ship loose conformal pads to the site as well as on-site handling and installation of those conformal pads. 
         [0012]    It is a further object of the invention to provide an interface pad that is mechanically attached to a concrete tie, in order to eliminate undesirable movement of the pad during shipping, installation and service. 
         [0013]    It is a further object of the invention to provide an interface pad that is manufactured and shaped for secure installation on a concrete tie. 
         [0014]    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. Note that the objects referred to above are statements of what motivated the invention rather than promises. Not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims. 
       SUMMARY OF THE INVENTION 
       [0015]    In one embodiment, 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 transport or installation and be torn or scraped off the tie. 
         [0016]    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. 
         [0017]    In another alternative embodiment, the resilient pad may be a one-piece cupped pad, which may not include a separate stiffener element. 
         [0018]    In some embodiments, 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 rails, plates or grade crossing panels sliding over the top surface of the tie. Alternatively, the interface pad may be cast directly into a concrete tie, eliminating the need for a separate fastener. This would also eliminate the time it would otherwise require to attach the fastener during manufacture or installation and minimize the chances that the pad will be pulled off of the tie during shipping, installation or maintenance. 
         [0019]    In one aspect, the invention comprises an interface pad for a concrete tie, 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 the stiffener; and at least one fastener passageway through the stiffener and the resilient pad to accommodate a fastener to secure the interface pad to the 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 the 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. 
         [0020]    In a further aspect, the resilient pad on the interface pad may comprise a plurality of sections divided by at least one channel. 
         [0021]    In a further aspect, the stiffener may comprise at least one aperture into which the resilient pad protrudes. The aperture may taper towards the upper side of the resilient pad, relative to the underside of the resilient pad. 
         [0022]    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. 
         [0023]    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. 
         [0024]    In another aspect, the invention comprises an interface pad for a concrete tie, comprising a tubular body having opposed first and second ends separated by a sidewall; and a contact pad on the second end; wherein the perimeter of the contact pad is smaller than the perimeter of the second end. The sidewall may flare outwardly from the second end to the first end. A lip may extend from the first end. 
         [0025]    In a further aspect, the contact pad may comprise a central pad at least partially surrounded by an outer pad. Each may extend out a distance from the second end, and the distance extended by the central pad may be less than the distance extended by the outer pad. One or more locking tabs may extend from the contact pad or from another portion of the second end. 
         [0026]    In yet further aspects, the interface pad may comprise a cylindrical body. The body may be solid or partially solid. 
         [0027]    In another aspect, the invention comprises a concrete tie comprising at least one interface pad as described herein. The tie may further comprise a recess in the tie to accommodate each interface pad. 
         [0028]    In yet another aspect, the invention comprises a method of installing an interface pad in a concrete tie, comprising the steps of providing at least one interface pad comprising a tubular body having opposed first and second ends separated by a sidewall and a contact pad on the second end, wherein the perimeter of the contact pad is smaller than the perimeter of the second end; placing a template over the interface pad, the template comprising at least one opening adapted to surround the pad and abut the second end; placing the template and the interface pad in a concrete tie form; casting the concrete tie over the template and the interface pad; and removing the template from the tie once the concrete has hardened. 
         [0029]    In a further aspect, the interface pad may comprise one or more locking tabs extending from the pad and the template further comprises one or more notches to accommodate the locking tabs. The step of removing the template may comprise pulling the template over the locking tabs. The step of placing a template over the interface pad may comprise inserting the interface pad into the opening and twisting the interface pad to connect the locking tabs with the notches. 
         [0030]    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. Moreover, this summary should be read as though the claims were incorporated herein for completeness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    The preferred embodiment of the invention will be described by reference to the drawings in which: 
           [0032]      FIG. 1  is a perspective view of the interface pad of the invention in place on a tie in a typical grade crossing; 
           [0033]      FIG. 2  is an elevation view of interface pad and grade crossing of  FIG. 1 ; 
           [0034]      FIG. 3  is a perspective view of a tie bearing interface pads of the invention; 
           [0035]      FIG. 4  is a perspective view of an interface pad of the invention; 
           [0036]      FIG. 5  is a sectional view of the interface pad of  FIG. 4 , taken along line A-A; 
           [0037]      FIG. 6  is a perspective view of a second embodiment of the interface pad of the invention; 
           [0038]      FIG. 7  is a sectional view of the interface pad of  FIG. 6 , taken along line B-B; 
           [0039]      FIG. 8  is a plan view of a tie bearing an alternative embodiment of the interface pads of the invention; 
           [0040]      FIG. 9  is a perspective view of an alternative embodiment of the interface pad of the invention; 
           [0041]      FIG. 10  is a sectional view of the interface pad of  FIG. 9 , taken along line C-C, installed on a tie; 
           [0042]      FIG. 11  is a perspective view of another alternative embodiment of the interface pad of the invention; 
           [0043]      FIG. 12  is a sectional view of the interface pad of  FIG. 10 , taken along line D-D, installed on a tie; 
           [0044]      FIG. 13  is a perspective view of another alternative embodiment of the interface pad of the invention; 
           [0045]      FIG. 14  is a sectional view of the interface pad of  FIG. 13 , taken along line E-E, installed on a tie; and 
           [0046]      FIG. 15  is a perspective view of an installation template for use with the interface pad of  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    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. Such placement and number of interface pads may vary depending on the specific application, such as grade crossing, turnout, switch or other, where the concrete tie is to be installed. 
         [0048]    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 segments making up stiffener plate  28 , the segments retained as stiffener  28  by connection with resilient pad  26  as described below. 
         [0049]    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 Shore A to 56 Shore D 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 any overlying parts are being installed on the ties, while still being able to cushion and support the overlying parts. It is also contemplated that resilient pad  26  may be made of a combination of one or more materials having different properties, such that the same pad may comprise different hardness or resilience properties throughout its body. This may be useful in selecting the proper pad for a given application with particular expected weight and cushioning requirements, or for adjusting pad requirements based on circumstances such as being located in different locations on a tie, or on different locations within a switch, for example. 
         [0050]    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 . 
         [0051]    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 . 
         [0052]    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 overlying parts, such as plates or 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 surrounding supporting pads  22 . 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. 
         [0053]    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 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 concrete tie in place. 
         [0054]    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. 
         [0055]    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 . 
         [0056]    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 . 
         [0057]    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 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. 
         [0058]      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 . 
         [0059]      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 shape, 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, 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. 
         [0060]      FIGS. 13 and 14  show perspective and cross-sectional views of another embodiment of interface pads  22 D which may be used without a stiffener or a fastener. In this embodiment, the fastener may be cast directly in to the upper surface of the tie  12 , by a preferred installation method which will be discussed later. 
         [0061]    Interface pad  22 D comprises an approximately tubular body  49 , having a first end  52  and an opposed second end  54  separated by a sidewall  56 . Sidewall  56  of the body  49  extends from the first end  52  to the second end  54 , at either approximately a 90 degree angle, or at an obtuse angle, such that the sidewall  56  flares between the second end  54  and the first end  52 . First end  52  may be open as shown, or may be completely or partially closed, as long as the selected material is the proper stiffness to allow for the correct amount of deflection under loading. It will also be understood that while the illustrated embodiment of the interface pad  22 D shows tubular body  49  as an approximately cylindrical shape, similar shapes, such as squares, rectangles, ovals or other shapes, may also be used. Likewise, the tubular body may be hollow, as shown, or may be partially or completely solid, as long as the selected material has the properties to perform as desired under loading. 
         [0062]    Lip  50  may be provided at first end  52 , extending outwardly of sidewall  56  as shown, or inwardly to close or partially close first end  52 . Lip  50  may also be omitted, although it may be preferable in that case to provide a sufficiently large flare in sidewall  56  to ensure that the interface pad  22 D cannot be removed from the concrete tie by pulling on second end  54 . Alternatively or in addition, one or more ribs  57  or other protrusions maybe provided within body  49  to assist in preventing body  49  from rotating within the concrete tie. 
         [0063]    Second end  54  may be provided with a contact pad  58 , defined by sidewall  60  having an outer perimeter that is preferably somewhat smaller than the perimeter of the sidewall  56 , but the perimeter of contact pad  58  could in fact be nearly the same as the perimeter of sidewall  56 . Contact pad  58  may be a unitary piece, or may include a central pad  66  at least partially surrounded by outer pad  68 . Central pad  66  may be separated from outer pad  68  by a recess  70 . Central pad  66  may be the same height as outer pad  68 , but is preferably slightly shorter. This allows outer pad  68  to act as a first compression zone, deflecting first under the weight of the overlying panels  18 ,  20  (not shown), which helps to absorb any non-uniformity in the panels, along the length of the tie, or in the tie bed depth, and therefore provides more even support, minimizing additional stresses and rocking in the panels. Under the additional weight of passing traffic, the central pad  66  engages with the panels as a second compression zone, taking its share of the weight and spreading the load out over a larger surface area. 
         [0064]    Alternatively, or in addition, central pad  66  may be provided in a different material than outer pad  68 , in order to ensure that the cushioning performance is suitable for the chosen railway application. For example, the cushioning requirements for an overlying concrete pad in a grade crossing may be different than for an overlying rail plate in a switch and it is preferable to be able to modify the cushioning properties of the interface pad  22 D for the specific application. It is also contemplated that this performance adjustment may be provided in an interface pad  22 D in which central pad  66  and outer pad  68  are made of the same material, processed or otherwise formulated differently, to provide the desired cushioning performance. 
         [0065]    Outer pad  68  is shown as a single pad, completely surrounding central pad  66 , but it will be understood that outer pad  68  may comprise one or more pieces that are capable of providing a similar effect, and that central pad  66  is not necessarily completely surrounded. 
         [0066]    As best shown in  FIG. 14 , interface pad  22 D is preferably embedded directly into a concrete tie  12 . This may be in any configuration suitable for the specific application, such as the configuration shown in  FIG. 8 , which might be used in a grade crossing application, for example. Second end  54  is generally even with the top surface of the tie  12 , and contact pad  58  extends above the tie  12  to separate it from overlying panels  18 ,  20  (not shown). Contact pad  58  is also preferably slightly separated from the tie  12 , such as by recess  72 , to allow contact pad  58  to expand laterally under the weight of the panels without being restricted by contact with the tie  12 . Recess  70  similarly allows central pad  66  to expand under pressure, without being restricted by contact with outer pad  68 . 
         [0067]    Interface pad  22 D may further comprise one or more locking tabs  74  extending from contact pad  58 , and/or outer pad  68 . 
         [0068]    Except as described above, the descriptions of the interface pad  22  assemblies and properties are applicable to the fifth embodiment  22 D, 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 D is shown with an approximately circular contact pad  58 , similar shapes, irregular or regular, such as squares, rectangles, ovals or other shapes, may also be used. For embodiments wherein contact pad  58  comprises a central pad  66  and an outer pad  68 , it will be further understood that central pad  66  and outer pad  68  need not be circular as shown, and that either or both may also be any other regular or irregular shape, as suitable. The central pad  66  and outer pad  68  need not be the same shape as each other, and, as noted above, outer pad  68  need not completely surround central pad  66 . 
         [0069]    Referring now to  FIG. 15 , template  76  may be used to install interface pads  22 D onto tie  12  (not shown). Template  76  comprises one or more central openings  78  having dimensions matching the outer dimensions of contact pad  58 , and one or more notches  80  in each central opening  78 . Notches  80  are spaced and dimensioned to match locking tabs  74 , although it is possible to provide a central opening  78  having more notches  80  than tabs  74 , which may provide increased flexibility in interface pad  22 D configurations. Template  76  is provided for a given tie, such that an appropriate number of central openings  78  are provided and located at appropriate locations on the tie. It will be understood that the number of openings  78 , and the location of those openings are shown in  FIG. 15  for illustration only and that the invention is not limited to a specific number of interface pads  22 D, or to any specific location of those pads on a tie. It is further contemplated that template  76  may be provided with a plurality of central openings  78 , but that for any particular tie only certain selected openings are used as described below, to install an interface pad  22 D. 
         [0070]    In use, template  76  is prepared by fitting the appropriate numbers of interface pads  22 D into openings  78 . Contact pad  58  of an interface pad  22 D may be inserted into a central opening  78 , with each of tabs  74  lined up with a notch  80 , then locked in place by twisting interface pad  22 D, such that each of locking tabs  74  slides over an edge of a notch  80 , mechanically connecting interface pad  22 D to template  76 . The template may then be used to define what will be the upper surface of a tie during the casting process, such that body  49  is embedded within the tie, while contact pad  58  protrudes slightly from what will be, in use, the upper surface of the tie. Once the tie casting process is complete, template  76  may be removed from the tie, such as by pulling template  76  over contact pad  58 , away from the cast tie. Locking tabs  74  are preferably flexible enough to allow the template to be removed by pulling or other force, with minimal movement of the interface pad  22 D within the tie body, and without pulling the entire interface pad  22 D out of the tie body. 
         [0071]    In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Technology Category: 0