Abstract:
A rail cover and support for mounting and insulating the rails of an electric transit system in which the rail cover is vulcanized both to the rail and outer skid support at the manufacturing site prior to delivery to the field and a rail cover completely surrounds both the base flange and web portion of each rail and terminates along the undersides of the top flange. In one form, the upper free ends of the rail cover are increased in thickness to form bumpers along opposite sides of the rail to cushion it against undue shifting or vibration. In fabricating the rail, a sheet dielectric material is vulcanized to the rail with or without a skid plate.

Description:
BACKGROUND AND FIELD OF INVENTION  
       [0001]     This invention relates to railway systems and more particularly relates to a novel and improved rail adaptable for use in electric transit systems of metropolitan areas.  
         [0002]     It has been proposed in the past to utilize resilient pads beneath the lower flanges of railroad rails as well as railroad ties for cushioning the rails and insulating them electrically from the ties and from other underlying structures. In many cases, clamps are employed on opposite sides of the lower flange which are in turn anchored into the railroad ties or rail bed. Also, in some cases an adhesive is interposed between the pad and the rail.  
         [0003]     Different considerations are involved in the construction and installation of rails for urban transit systems which are typically employed as a part of electrical transit systems and must be mounted in asphalt or concrete roadways. Instead of a gravel or dirt roadbed the rails are embedded in spaced parallel channels formed out of the existing roadway such that the top or head of the rail projects slightly above the upper end of the channel or roadway surface. In the past, rubber boots have been loosely disposed in surrounding relation to the bottom flange of the rail and typically held in place with the use of clamps extending along the entire length of the rail system. This approach has been unsatisfactory particularly from the standpoint of complete vibration and sound-proofing as well as providing the necessary resistance to corrosion resulting from stray electrical current. In stray current corrosion, an electrical current flowing in the environment adjacent to a structure causes one area on the structure to act as an anode and another area to act as a cathode. For example, in an electric railway, a pipeline or other structure may become a low resistance path for the current returning from the train to the power source. Whenever the pipeline is caused to be more positive by the stray current, corrosion occurs at a higher rate but can be avoided by proper insulation of the rail.  
         [0004]     Over extended periods of time, rail systems of the type described have been wholly inadequate to achieve the necessary vibration and sound-proofing and to avoid corrosion from stray or leakage current of the types described.  
       SUMMARY OF THE INVENTION  
       [0005]     It is therefore an object of the present invention to provide for a novel and improved insulated rail system and method of making same.  
         [0006]     It is another object of the present invention to provide for a novel and improved rail system which is rugged, durable and comprised of a minimum number of parts.  
         [0007]     It is a further object of the present invention to provide for a novel and improved insulated rail system which is vibration and sound-proof as well as capable of substantially eliminating any corrosion resulting from stray or leakage current and which enables greatly simplified installation over extended distances.  
         [0008]     It is an additional object of the present invention to provide for a novel and improved method of manufacturing insulated rail in a minimum number of steps and which results in the formation of a rubber clad rail assembly.  
         [0009]     A preferred form of the present invention resides in a transportation rail for extension along a rail bed, the rail having a bottom flange, top flange along which a train or other vehicle is advanced, and a vertical web portion interconnecting the bottom and top flanges and wherein the improvement comprises a rail cover composed of a resilient, dielectric vulcanizable material including a seat portion surrounding the bottom flange and upper side portions covering opposite sides of the web portion up to the top flange, and means for vulcanizing the cover to the seat portion and web portion of the rail. In another preferred form, a rigid skid plate surrounds the sides and underside of the bottom flange prior to placement in the guideway or channel formed in the roadway when used for electric trains, and lateral extensions of the sides of the cover may cushion the rail against lateral thrusting or shifting.  
         [0010]     A preferred method of manufacturing a rail section of the type described comprises the steps of positioning a sheet of a flexible dielectric material in surrounding relation to the base flange and opposite sides of the web portion along the substantial length of the rail section, and vulcanizing the sheet under heat and pressure to the rail section. If a skid plate is employed, the method further comprises the additional step of positioning the skid plate in surrounding relation to an underside and opposite sides of the bottom flange and vulcanizing the cover sheet and skid plate together with the rail. The cover sheet may be extruded into the desired configuration prior to vulcanization and given additional thickness along opposite sides of the web portion, or separate strips of a flexible dielectric material may be adhered to the sides of the cover sheet for additional cushioning and sound-proofing.  
         [0011]     The above and other objects, advantages and features of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of preferred and modified forms of the present invention when taken together with the accompanying drawings in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a cross-sectional view of one preferred form of rail in accordance with the present invention;  
         [0013]      FIG. 2  is a cross-sectional view of another preferred form of rail in accordance with the present invention;  
         [0014]      FIG. 3  is a cross-sectional view illustrating one step in the process of manufacturing the form of invention shown in  FIG. 2 ;  
         [0015]      FIG. 4  is a cross-sectional view of another step involved in the process of manufacturing the form of invention shown in  FIG. 2 ; and  
         [0016]      FIG. 5  is a side elevational view illustrating welded rail sections covered by a patch as a part of the insulated rail system. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]     Referring in more detail to the drawings,  FIG. 1  illustrates one preferred form of a composite rail which is made up of a standard rail  10  and a rail cover  12 . The rail  10  is of generally I-shaped cross-sectional configuration having a bottom flange  14  provided with a flat undersurface  15  and opposite sides  16  together with sloped upper surfaces  17  which merge into a vertical web portion  18 . A top flange  20  has a slightly convex top surface  22  and opposite sides  24  together with sloped undersurfaces  26  which merge into the upper end of the vertical web portion  18 . In accordance with conventional practice, the rail may be composed of various grades of steel or aluminum depending upon load requirements. As a setting for the present invention, the rail is composed of steel and is designed with a relatively broad base flange  14  in comparison to the width of the top flange  20 .  
         [0018]     In accordance with the present invention, the rail is adapted for use as a railroad track for the prevention of corrosion due to stray current leakage in electrified rail transit systems operating in metropolitan areas. To this end, the rail  10  is clad with a tough, durable elastomeric sheet or cover  30  which is vulcanized to the rail and specifically in such a way as to cover the entire base flange  14 , opposite sides of the web portion  18  and undersides  26  of the top flange  20 . One side  28  of the cover is of progressively increased thickness along the underside of the top flange and terminates in a lobe  28 ′ along one side of the top flange; whereas, the opposite side  29  is of progressively increased thickness along the underside of the top flange and terminates in a tapered end  29 ′ beneath the side of the top flange so as to leave clearance along that side for the wheel flange of each of the train wheels.  
         [0019]      FIG. 2  illustrates another preferred embodiment in which a skid plate  32  of generally channel-shaped cross-sectional configuration is mounted on the rail directly to the rail cover  30  extending along the underside  15  and opposite sides  16  of the base flange  14 . Thus, the skid plate  32  includes a substantially flat base  34  and opposite sides  36  which are bent into generally concavo-convex configuration in tightly surrounding relation to the opposite sides  16  and terminate in upper edges  38  which overlie outer ends of the sloped upper surfaces  17 .  
         [0020]     The rail cover  30  is vulcanized by subjecting to high pressure and super-heated steam so as to bond the cover both to the steel rail  10  and skid plate  32 . This procedure creates an impermeable barrier which protects the surrounding environment from the costly and often hazardous ravages of electrolytic corrosion. In the form of  FIG. 2 , the sides of the rail cover are of uniform thickness and terminate along the undersides of the top flange.  
         [0021]      FIGS. 3 and 4  illustrate the steps followed in the fabrication of one form of rail system as hereinbefore described. The rail  10  is customarily cut into  40 ′ long sections, and a bonding agent is applied to the bottom flange  14  and web portion  18  as well as the undersides of the top flange  20  throughout the entire length of the section. The sheets of rubber making up the rail cover  20  are cut into shorter lengths than the rail section so as to leave several inches at each end of the rail section exposed for welding the section ends as hereinafter described. Similarly, the skid plate  32  is formed into sections slightly shorter in length than the rail sections  10  so as not to interfere with the welding operation. At the manufacturing site, each skid plate section  34  is positioned in a steel channel jig J and, as illustrated in  FIG. 3 , each length of the rail cover  30  is placed in the skid plate  32  with opposite sides of the cover  30  extending upwardly beyond opposite sides  36  of the skid plate  34 . The upper ends  38  of the opposite sides  36  are bent or crimped over the outer ends of the rail. Again, a suitable bonding agent is placed along the inner contacting surfaces of the rail  10  as a preliminary to applying the free sides of the cover  30  into contacting relation to the upper surfaces  17  and opposite sides of the web section  18  into the configuration illustrated in  FIG. 3 , although it will be appreciated that the bonding agent may be applied to the entire inner surface of the entire cover  30  rather than the rail  10  prior to placement beneath the rail. A suitable crimping tool is then employed to crimp the upper ends  38  of the skid plate  32  over the outer ends of the upper surfaces  17 . In another preferred form, the rubber cover  30  may be extruded into the desired rail-shaped configuration as illustrated into  FIG. 2  prior to the vulcanization step now to be described.  
         [0022]     Each rail section is typically on the order of  40 ′ in length and may be vulcanized in a suitable press to subject it to the desired high pressure and super-heated steam level over a predetermined time interval depending to a great extent on the thickness of the cover  30 . For the purpose of illustration but not limitation, the rail cover  30  may be on the order of ¼″ thick for a rail which is on the order of 8″ high. The composition of the rail cover  30  is totally impervious to moisture penetration and is highly resistant to harsh chemicals, such as, street de-icers, other acids or salts and automotive exhaust gases. It can withstand severe impact and abrasion and easily endures the usual rough handling and hauling from the plant to the rail site.  
         [0023]     The skid plate  32  is useful as a means of protecting the rail cover when installed in the rail bed. For example, in an electric transit system, each rail of the railroad track is placed in a separate channel or shallow recess formed in the pavement of the roadway, as illustrated in  FIGS. 1 and 2 . As best seen from  FIG. 5 , typically the ends of the rail section are welded together as at  50  and the weld seams are cleaned, covered, sealed and insulated by on-site application of a sealant. If it should be necessary to leave a gap between the end of the cover  30  and the end of rail section  10 , a heat-cured patch  52  is applied to the exposed ends of the rail sections  10  between the terminal edges of the rail covers  30  of adjoining rail sections. Preferably, the patch  52  is molded or extruded into the same cross-sectional configuration as the rail cover  30  and cured at the factory site. Upon completion of the welding operation, the patch  52  is slipped over the rail and chemically cured or heated with the opposite edges of the patch butt-welded or cured together with the ends of the rail covers  30  as designated at  54 .  
         [0024]      FIG. 5  illustrates the rail sections welded together and patched as described without the use of skid plates  32 . In other words, the rail  10  corresponds to that shown in  FIG. 1  and may be installed in the rail channels C without adding the skid plates  32 . Whether employed with or without the skid plates  32 , a suitable filler as designated at F in  FIGS. 1 and 2  is illustrated as being placed around the rails after they have been laid and welded in the channels. In either preferred form as shown in  FIG. 1  or  2 , the filler may be a concrete filler although it will be apparent that other types of commercial fillers may be employed, taking care to leave a gap G between the filler and one side  24  of the top flange  20  so as not to interfere with the train wheel.  
         [0025]     From the foregoing, the rail cover  30  is characterized in particular by acting as an insulator to prevent electrolysis and as a corrosion-proof barrier to prevent electro-chemical attack, such as, oxidation of the steel or by exposure to corrosive chemicals, such as, street de-icers or by automobile exhaust and other acids. Thus, it is highly important to vulcanize the rail cover  30  to the entire rail surfaces other than the wear surfaces so as to act as an effective barrier against chemical attack as well as electrolytic corrosion.  
         [0026]     It is therefore to be understood that while preferred forms of invention are herein set forth and described, the above and other modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and reasonable equivalents thereof.