Abstract:
A T-shaped electrically insulated member for securing to rails having electric current passing therethrough. The electrically insulated rail member includes a metallic core and an electrically insulating material encasing the metallic core. The electrically insulated rail member can be used as a gauge plate or a switch plate. Bushings are received by the electrically insulated rail member for receipt of fasteners secured to adjacent rail members. Also disclosed is a method for manufacturing the electrically insulated rail member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 09/089,958 filed Jun. 3,1998 now U.S. Pat. No. 6,170,756 entitled “Gauge Plate and Switch Rod Insulators”. 
     This application claims the benefit of United States Provisional Patent Application Ser. No. 60/065,519, filed Nov. 12, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an insulating joint for use in a rail system to electrically isolate parts of the rail system from each other. 
     2. Description of the Prior Art 
     A rail system is generally divided into sections or blocks to be able to detect trains which permits more trains to travel on one stretch of track or rail. Each section is electrically isolated from all other sections so that when no train is present in the section, a high electrical resistance can be measured over the parallel railbars in the section. When a train enters a section, the train short circuits adjacent railbars and the electrical resistance drops. 
     Railbars are generally welded to each other or attached to each other by a steel joint. High performance non-metallic joints are used for electrically isolating two railbars in order to build an electrically isolated section. Switches are insulated in the same way by dividing both gauge plate and switch rods into two parts and by joining the respective parts with a non-metallic joint. 
     Known non-metallic joints are very expensive because of the special high performance material which has to endure high tensile and flexural forces. One such non-metallic material used for the joints is a laminated SCOTCHPLY® material manufactured by 3M of St. Paul, Minn. In addition, a separate insulating plug must be utilized between ends of the gauge plate or switch rod to prevent material buildup of debris which would then cause an electrical short. 
     An object of the present invention is to provide an insulating joint whereby the above drawbacks are eliminated. 
     SUMMARY OF THE INVENTION 
     According to the present invention, an insulating joint is provided, including a metallic core body having at least one hole formed in the body and a first insulating layer covering the outer surface of the body. A second insulating layer can be arranged in the holes. Preferably, the insulating layer is made of polyurethane. Alternatively, a rubber layer can be used. 
     An advantage of the present invention is that it is less expensive to manufacture than the prior art SCOTCHPLY® arrangements. 
     A preferred embodiment of the present invention further includes bushings in the holes to account for pressure forces exerted by the bolts used for joining, for example, two switch rods or gauge rods. 
     Preferably, a second insulating layer is arranged on an outer surface of the bushing. This will enable the simple exchange of new bushings when the bushing or the second insulating layer becomes worn. 
     Preferably, the insulating joint is T-shaped, wherein the core is likewise T-shaped. The core includes a flat base and a ridge or leg depending from the base. The T-shaped core is covered with the insulating layer. 
     Further, the present invention is an electrically insulated rail member to be secured to rails having an electric current passing through the rails that includes a metallic core and an electrically insulating material encasing the metallic core. The metallic core can be flat or T-shaped. Further, the metallic core can be made of steel. The electrically insulating material can be molded about the metallic core. The T-shaped cross section is defined by a flat body and a depending leg. The metallic core can be flat and the depending leg can be completely defined by the electrically insulating material. The present invention can be used as a switch plate or a gauge plate. 
     The metallic core encased with the electrically insulating material defines a body having a hole adapted to receive a fastener for securing the electrically insulated rail member to an adjacent metallic member for maintaining a gauge of two adjacent rails, wherein the fasteners are electrically insulated from the metallic core. A plurality of holes can be defined in the body for receiving fasteners for maintaining a gauge of two adjacent rails, wherein the fasteners are electrically insulated from the metallic core. 
     The present invention is an arrangement for maintaining the gauge between a first rail and a second rail to form a track having a current passing therethrough and includes a first member extending from the first rail toward the second rail, a second member extending from the second rail toward the first rail and a gauge plate secured to the first member and the second member. The gauge plate includes a metallic core and an electrically insulating material encasing the metallic core whereby the electrically insulating material electrically insulates the first member from the second member. The arrangement includes a gap defined between the first member and the second member, wherein the gauge plate further includes a body having a leg depending therefrom, wherein the leg is received within the gap. 
     The present invention is also an arrangement for coupling a first rail and a second rail to form a track having an electric current passing therethrough and includes a first member extending from the first rail toward the second rail and a second member extending from the second rail toward the first rail. A first plate is secured to the first member and the second member and includes a metallic core and an electrically insulating material encasing the metallic core. A second plate is provided having an electrically insulating material encasing a metallic core. The first plate and the second plate sandwich ends of the first member and the second member which are secured thereto. The first plate and the second plate can be T-shaped having legs depending therefrom which are received within a gap defined by the first member and the second member. The legs can abut against each other. Holes are defined in the first plate and the second plate that align with holes defined in the first member and the second member, respectively, and fasteners pass through the respective holes. The holes can be defined by bushings received by the plates. 
     The present invention is also a method for manufacturing a T-shaped electrically insulating plate for use in coupling two rails having electric current passing therethrough, comprising the steps of: providing a metallic core; and encasing the metallic core with an electrically insulating material and forming a T-shaped electrically insulating plate. The method can further include providing bushings in the plate for receipt of fasteners. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a first embodiment according to the present invention in a switch rod joint; 
     FIG. 2 is a sectional view of a bushing shown in FIG. 1; 
     FIG. 3 is a sectional view of a second embodiment according to the present invention in a gauge plate joint; 
     FIG. 4 is a sectional view of a bushing shown in FIG. 3; 
     FIG. 5 is an exploded view, partially in section, of a third embodiment according to the present invention of a switch rod insulator plate; 
     FIG. 6 is a top plan view of the gauge plate shown in FIG. 3; 
     FIG. 7 is a elevational view of the gauge plate shown in FIG. 6; and 
     FIG. 8 is an elevational view of a gauge plate similar to that shown in FIG. 7 with a modified steel core. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a first embodiment according to the present invention used to connect a first part or first member  10  and a second part or second member  12  of a switch rod. The switch rod is attached by brackets  14  to the movable laterally spaced apart railbars of a switch which are used to maintain the gauge between movable railbars. 
     Two parts  10  and  12  are connected to each other by two T-shaped insulating joints or switch plates  16  having T-shaped cross sections. Each insulating joint  16  includes a metallic core encased with an electrically insulating material. Each core is T-shaped with a flat body  17   a  having a leg or ridge  17   b  depending therefrom. Likewise, the insulating joint  16  includes a flat body  17   c  and a depending leg  17   d . The depending leg  17   d  is received within a gap G defined between the first part  10  and the second part  12 . Ends of the depending legs  17   d  abut against each other. Alternatively, it is believed that the metallic core can be a flat plate encased with an electrically insulating material replacing the depending leg or ridge  17   b  completely with insulating material as shown in FIG.  8 . Alternatively, the insulating joints can be flat as opposed to T-shaped and an electric insulative filling can be provided between the insulating joints in the gap G defined by the opposed ends of the first part  10  and the second part  12  for electrically insulating these two parts  10  and  12  from each other. The insulating joints  16  are secured to the first part  10  and the second part  12  by a fastening arrangement of bolts  20 , nuts  22  and washers  24 . 
     More specifically, the insulating joint  16  includes a steel core  26  with a plurality of holes defined therein through which bolts  20  extend, an insulating layer  28  encasing the steel core  26  and a plurality of bushings  30  provided in the holes. FIG. 2 shows the bushings  30 , which are electrically insulated from the steel core  26 . Either the bushings  30  can have a separate bonded insulating layer or the insulating layer can be provided by the insulating layer  28 . 
     The steel core  26 , not the insulating layer  28 , withstands tensile forces applied to the insulating joint  16  through parts  10  and  12 . The bushings  30  protect the steel core  26  and the insulating layer  28  from wear caused by the bolts  20 . As is evident, the installed T-shaped insulating joint  16  sandwiches ends E and E′ of the two parts  10  and  12  and are secured thereto. 
     FIGS. 3,  6  and  7  show a second embodiment according to the present invention of an insulating joint or gauge plate  40  for insulating a first part or first member  42  and a second part or second member  44  for maintaining the gauge of two rails  46  of a switch. The first part  42  and the second part  44  extend from respective laterally spaced apart rails  46 . 
     The insulating joint or gauge plate  40  is T-shaped, i.e., has a T-shaped cross section, such that a part of the insulating joint  40  prevents the ends of the first part  42  and the second part  44  from making electrical contact. The insulating joint  40  includes a steel T-shaped core  48 , a first electrically insulating layer  50 , which encases the core  48 , and steel bushings  52 . As shown in FIG. 4, outer surfaces of each of the steel bushings  52  are covered with a second electrically insulating layer  54 . The T-shaped core  78  of the insulating joint  40  likewise includes a flat body  47   a  and a depending leg  47   b . The insulating joint  40  includes a flat body  47   c  and a depending leg  47   d . The depending leg  47   d  is received within a gap G′ between the first part  42  and the second part  44 . 
     Bolts  56 , nuts  58  and washers  59  secure the insulating joint  40  to the first part  42  and the second part  44 . 
     An advantage of this second preferred embodiment is the T-shape of the joint which makes a separate insulating plug redundant. Because of this, the installation of the insulating joint  40  is easier than installing a joint of the prior art, and there is no need for a supplemental filling. 
     Another advantage is that the steel bushings  52  can be replaced whenever the steel bushings  52  or the second electrically insulating layer  54  are worn. In this manner, the dimensions of the hole defined in the core  48  will not vary due to wear. 
     FIG. 8 shows another embodiment of an insulating joint  40 ′ made in accordance with the present invention that is similar to the insulating joint  40  shown in FIGS. 3,  6  and  7 , where like reference numerals are used for like parts. The only difference between insulating joint  40 ′ and insulating joint  40  is that the core  48  of insulating joint  40  is replaced with a flat plate core  48 ′ of the insulating joint  40 ′ and the “T” is formed totally by the first electrically insulating layer  50 . 
     FIG. 5 shows another preferred embodiment of an insulating joint  60  made in accordance with the present invention. This embodiment is similar to the insulating joint  16  described above and can be used in a switch rod in lieu of insulating joints  16 . 
     The insulating joint  60  includes a T-shaped steel core  62 , a first insulating layer  64  and the steel bushings  52  having a second electrically insulating layer  54  shown in FIG.  4 . The insulating joint  60  is T-shaped such that, by mounting two insulating joints  60  on a switch rod, the insulating joints  60  abut and entirely fill the space between the two ends of the switch rod parts. Holes  66  are provided for receipt of the steel bushings  52 , which are used to receive fasteners. Similar holes are provided in the other embodiments disclosed herein. As should be evident, the bushings  52  and  30  define holes H that align with respective holes H′ defined in the first parts  10  and  42  and second parts  12  and  44  for receipt of the bolts  20  and  56 , respectively, and the bolts  20  and  56  are electrically insulated from the respective metallic cores  26 ,  48  and  62 . 
     All of the insulating joints are made by placing or providing the steel core in a mold and molding around the steel core electrically insulating material, such as polyurethane, rubber or other polymeric material, thereby forming a T-shaped electrically insulating plate. The metallic core can be flat or T-shaped. The bushings at that time can be cast in place. After the polyurethane hardens, the insulating rail joint is removed from the mold and if the bushings for receipt of fasteners, such as bolts  20  and  56 , are not cast in place during molding, they can then be received by the insulating joint holes. 
     It will be understood by those of ordinary skill in the art that modifications may be made without departing from the spirit and scope of the present invention.