Abstract:
A conductor rail fishplate for the electrical and mechanical connection of successive conductor rails has two symmetrical plates, which encompass the exterior of the conductor rail. The two plates are tensioned against one another using screws. Contact strips are arranged in the contact zone between the conductor rail and the respective plates, the strips coming into contact with the respective surfaces by means of a large number of spring-loaded contacts.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to a conductor rail fishplate. 
   Increasing demands on overhead contact line systems in terms of safety, reliability, current carrying capacity, short-circuit resistance, and minimal installation height have led to the use of conductor rails holding a contact wire that does not carry a tensile load. Fields of application are tunnels and maintenance workshops for electric motor vehicles since work-hindering contact lines can be swung to the side. 
   Conductor rails are usually molded in lengths of about 12 meters. Conductor rail systems are assembled from successive conductor rails, which must be connected mechanically and electrically. On one hand, the connection requires mechanical strength, maintenance of positive fit, and also transmission capacity for electrical current, which can reach up to 5000 A in current spikes. The positive fit demands that under the load of its own weight, no bends will occur at the joint of two successive conductor rails. 
   Deformation-free joints of two conductor rail were previously achieved using two plates at the inside of the crosspieces of the conductor rail. These fishplates must be inserted into the hollow spaces of the conductor rails. Then they are pushed against the crosspieces from the outside with screws. The mechanical and positive-fit strength is achieved through wedge-shaped edges on the fishplates and counter shapes in the interiors of the crosspieces. The electrical transmission of current is realized through linear contact between the fishplates and the crosspieces inside of the profile. The linear contacts are achieved through pressure from the tightening of the screws. 
   A disadvantage for this known conductor rail joint is that two plates must be inserted, holes must be bored in the crosspiece and the plates, and a corresponding number of screws must be tightened. In practice, 16 holes or even threaded holes are bored in each plate and the threads cut. The known conductor rail joint is thus not assembly-friendly. It is also not practical when a conductor rail section must be replaced, because access to the hollow space on the conductor rail is possible only with a narrow object at the lower clamp opening for the contact wire. The linear, not clearly defined electrical contacts limit current transmission. 
   SUMMARY OF THE INVENTION 
   An object of this invention is to improve the known conductor rail joint such that it is easy to assemble, it has a defined current transmission for high electrical currents, it features high mechanical strength at least equal to that of the known conductor rail and it can be detached on demand. 
   In one aspect, the conductor rail fishplate for joining two adjacent conductor rails consists of two symmetric plates, which overlap the exterior of the conductor rails and which are attached to the conductor rail by a fastener outside a cross-section of the conductor rail, and additionally, spring-loaded contact strips are arranged between the plates and the conductor rail. Therefore, no holes are necessary in the conductor rail. Assembly is easy because the plates are attached to the conductor rail on the outside and overlap the conductor rail. The mechanical strength is achieved by the pre-tensioning of the two plates with screws. The pre-tensioning of the conductor rail fishplates achieves defined point contacts between the fishplate and the conductor rail due to the contact strips. The crosspieces of the conductor rail are not impaired in their elasticity, so that a contact wire pull-in car can also straddle the profile unimpaired. The conductor rail joint can be detached easily from its outside. Also, repeated loosening and tightening is possible without additional means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a cross section of a conductor rail having a conductor rail fishplate according to the invention; 
       FIG. 2  shows a side view of the conductor rail joint and plate of  FIG. 1 , 
       FIG. 3   a  shows a top view of one embodiment of a contact strip; 
       FIG. 3   b  shows a cross section of the contact strip of  FIG. 3   a.    
       FIG. 4   a  shows a top view of another embodiment of a contact strip; 
       FIG. 4   b  shows a cross section of the contact strip of  FIG. 4   a.    
       FIG. 5  shows a side view of a conductor rail fishplate; and 
       FIG. 6  shows a section along the line VI—VI of FIG.  5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a conductor rail  1  holding contact wire  2 . Referring to  FIGS. 1 and 2 , two symmetrical conductor rail fishplate  4  (in the following called “plates”), which are extrusion molded or milled, are attached at a joint ( 3  in  FIG. 2 ) of two adjacent conductor rails. These plates  4  overlap the exterior of the conductor rail and each have a groove  5 , in which a top, horizontal crosspiece  6  of the conductor rail projects. Each plate  4  has a head  7  with a hole  8 , a center part  9 , and a bottom crosspiece  10 , which connects to the center part  9 . The mentioned groove  5  is located between the head and center part. The head  7  overlaps the conductor rail  1  almost up to its center  11 , while the inside  12  of the center part  9  and the crosspiece  10  pointing towards the conductor rail  1  are shifted outwards and feature a spacing  13  relative to the conductor rail, so that it is possible to widen or bend the conductor rail  1  in order to insert the contact wire  2 . The crosspiece  10  is thus shaped like a plate and is used to guarantee the mechanical flexural strength in the longitudinal direction of the conductor rail  1 . 
   The transition region between the groove  5  and the inside  12  is provided with a rounded section  14 , which comes into contact with a diagonal section  15  of the conductor rail in the transition region between the horizontal crosspiece  6  and the vertical crosspiece  16  of the conductor rail when the plates are assembled. This provides a linear contact in the contact region. If the two symmetrical plates  4  are tensioned against each other by a fastener (i.e. screw) through the hole  8 , then the two plates  4  are not only pushed against each other, but are also pressed with the top, downwards pointing surface  17  of the head  7  against the top side of the conductor rail  1  due to the rounded section  14  in connection with the diagonal section  15 . In the surface  17 , the two plates each have a recess, in each of which a set of spring-loaded contact strips  18  is inserted. Through the vertical tightening of the plates, the contact strips are pressed with defined force against the conductor rail  1  and the plates  4  over the entire length of the plates, so that a very good multiple contact is produced, which bridges the joint  3 . 
   In the depicted embodiment, the horizontal extent of the groove  5  in the cross section of  FIG. 1  is longer than that of crosspiece  6  so that the free ends of the crosspieces do not come into contact with the base of the groove  6 . This has the effect that the rounded section  14  in contact with the diagonal section  15  always comes into use. 
   The section of the center part  9  directed downwards towards the contact wire  2  is provided with a bevel  19 . Furthermore, a bevel  20  is formed in the transition region between the center part  9  and the crosspiece  10 . Incidentally, all other edges are provided with a rounded section. 
   The length of the plates in the travel direction depends on the desired mechanical and electrical properties and in practice equals between 200 mm and 400 mm according to current transmission capacity. According to the length and mechanical strength, two to four screws are used. There is a corresponding number of holes a in the head part. For another embodiment, four screws are always used, independent of the length of the plates. 
   In the side view of  FIG. 2 , above all the joint  3  between two adjacent conductor rail can be seen, as well as several holes  8 . The selected center separating line indicates that the length of the plates can be varied in the travel direction. 
     FIGS. 3 and 4  show two variants of contact strips.  FIG. 3   a  shows a top view and  FIG. 3   b  a schematic cross section. Overall, the contact strips have two parallel connecting pieces  20  and  21 , between which there is a plurality of spring contacts  22 , which are connected to the two crosspieces  20  and  21 . The contacts  22 ′ and  22 ″ curve outwards alternately from a center plane  23 . In addition, the two crosspieces  20  and  21  can be bent outwards from this plane  23 . If the plates  4  of  FIG. 1 and 2  are pressed against the conductor rail, then primarily the contacts  22  and in the case of the bent crosspieces  20  and  21  also the crosspieces come into contact with the conductor rail  1  and the plates  4  and thus form an electrical connection. 
     FIG. 4  shows another variant, for which the contacts  22  bulge out only to one side like an arc. Obviously, other shapes of contact strips are also possible. However, the essential advantage is that a plurality of contact points are always available and the individual contacts are pressed with defined spring force against the corresponding surfaces, so the desired electrical connection is produced. 
   In addition to the holes  8 , the plates  4  can also have threaded holes  24  or  25 , which simplify disassembly. The threaded holes  24  or  25  thus go through only one plate of a pair of opposing plates, so that when screwing in one screw into one of the threaded holes  24  or  25 , its front end then supports at the opposing plate and thus the two plates  4  and  4 ′ are pressed apart. The threaded holes  24  and  25  can be symmetric about a centerline  26 . Obviously, it would also be possible to form the threaded holes only on one side, i.e., in one plate. The formation in the two opposing plates has the advantage of better accessibility of at least one of the threaded holes in the installed state. 
   When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
   As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.