Patent Application
20070034705
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.
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.
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.
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.
It is therefore an object of the present invention to provide for a novel and improved insulated rail system and method of making same.
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.
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.
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.
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.
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.
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:
Referring in more detail to the drawings,
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.
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
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.
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
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.
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.
