Abstract:
Fixed carriageway for rail vehicles having sleepers embedded in a carriageway panel and a reinforcement includes plural longitudinal and transverse rods disposed parallel and transverse to the sleepers, wherein the longitudinal rods and transverse rods are electrically isolated from one another.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a fixed carriageway for rail vehicles having sleepers embedded in a carriageway panel and a reinforcement, which comprises plural longitudinal rods and transverse rods disposed in the carriageway panel parallel and transverse to the sleepers. 
     The term “fixed carriageway” refers to a section of rail with a superstructure, in which the ballast is replaced by another material such as concrete or asphalt for example. In the construction of the fixed carriageway, the sleepers are adjusted and embedded in a casting compound, creating a carriageway panel. The substructure of the carriageway panel may comprise a hydraulically bonded support layer, a ballast support layer, a frost-protection layer, a foil or a geotextile. 
     In the operation of rail sections, it is necessary to determine whether a certain section of track is clear or whether a train is located thereon. To this end, track circuits can be used in which a transmitter feeds an audio frequency signal into the track in such a manner that the rails act as to-and-fro conductors. At a remote site, the signal is evaluated by a receiver and by means of the signal level received, it is decided whether the section of track between the transmitter and receiver is clear. 
     One of these track circuit systems, which is available under the reference UM71 and is used in various countries, operates with four carrier frequencies of between 1.7 and 3.1 kHz. 
     Due to the impedances of rails and track connectors, the signal levels of the track circuits are damped or energy is drained from the track circuits as the distance between transmitter and receiver increases. Since the system is impressed particularly by inductive voltage drops due to the frequencies used, this component of damping can be compensated by the regular arrangement of specified transverse capacitances between the two rails. On a clear section, with compensation, maximum track circuit lengths of 1500 meters can be achieved. In non-compensated realisations, on the other hand, only track circuit lengths of 450 meters maximum are possible. Conventional track circuit systems, such as the above-mentioned system UM71, have hitherto been used predominantly with ballast carriageways. 
     A reason for not using such track circuits in fixed carriageways, however, is the fact that in these carriageways transverse rods and longitudinal rods are present in the concrete support panel as reinforcement. In the reinforcing rods extending longitudinally to the track axis, due to the magnetic fields of the audio frequency rail currents, a voltage is induced. Closed short-circuit current paths can form via the transverse reinforcements. The losses thus occurring in the reinforcement rods cause additional damping of the track circuit signals or to additional energy depletion. A possible consequence of this is that the receiver of the track circuit no longer measures a sufficient level in spite of a clear section of track and thus signals that the track is occupied, which is not in fact the case. 
     SUMMARY OF THE INVENTION 
     An object of the invention is therefore to indicate a fixed carriageway in which a track circuit system can be used in a trouble-free manner. 
     To achieve this, in a fixed carriageway of the type mentioned in the introduction, it is provided that the longitudinal rods and the transverse rods are electrically isolated from one another. 
     By means of electrical isolation, the formation of closed short-circuit current paths is prevented, and accordingly damping of the track circuit signals does not occur. The receiver of the track circuit then only measures a low level if a train is in fact on the section of track. 
     In a further embodiment of the invention, it can be provided that longitudinal rods extending parallel to one another and/or coupled together are isolated from one another in the overlap region. Electrical interruption of the longitudinal rods is a particularly effective way of reducing damping. The length of the continuous longitudinal rods of the reinforcement is thus shortened to a specified value, so that the desired reduced damping is set. 
     Trouble-free operation of the track circuit can be achieved in the fixed carriageway according to the invention in that a spacer is disposed between two rods to be isolated from one another. A spacer of this type can be assembled with virtually no cost or complication in the construction of the fixed carriageway. By means of the spacer, the rods to be isolated from one another are held at a specified distance from one another before being embedded in the casting compound, so that no electrical connection forms between the longitudinal rods and the transverse rods. In this case, it may be considered a particularly great advantage that the static properties of the fixed carriageway are not affected by the spacers, since in the carriageway according to the invention, the same longitudinal and transverse rods are used as before, lying virtually in the same place as in conventional fixed carriageways. 
     It is also within the scope of the invention that the spacer comprises a first section at least partially engaging round the first rod and a second section at least partially engaging around the second rod. A spacer so constructed is characterised by particularly good grip on the rods, so that slipping off or displacement is virtually impossible. An even better grip and particularly safe fixing are achieved if the first and second section of a spacer are formed in the shape of segments of a circle and are adapted to the outer diameter of the rods. In the case of spacers which are used at points of intersection of a longitudinal rod with a transverse rod, the first and second section of the spacer can be offset with respect to one another by 90°. 
     Spacers can be particularly easily mounted on the fixed carriageway if the two sections are formed as clips. In this case, it can be provided that the spacers consist of a resilient material, in particular a plastics material. Such spacers can be manufactured economically and can be clipped easily on to the normally round rods. 
     It is within the scope of the invention that longitudinal rods are isolated by spacers from transverse rods which are formed for example as lower booms of a grid support of a sleeper. Sleepers for a fixed carriageway may for example have two sleeper blocks, which are connected together by two grid supports extending in parallel. The grid support(s) conventionally comprises or comprise plural grid rods extending transversely and acting as transverse rods. By means of the isolation provided according to the invention of the longitudinal rods from the transverse rods by spacers, problem-free functioning of the track circuit system is ensured. 
     In a further embodiment of the invention, it can be provided that in a sleeper having two grid supports of the fixed carriageway according to the invention, spacers are only mounted on one lower boom of a grid support. Thus the other lower booms of the grid support are automatically kept at a distance from the longitudinal rods, so that the desired electrical isolation is achieved. 
     According to an alternative, also particularly effective modification of the fixed carriageway according to the invention, in the case of rods to be isolated from one another, at least one rod may have an insulating coating. The coating serves the same purpose as the spacer, as it prevents contact between a transverse rod and a longitudinal rod, so that short-circuit current paths do not form. Accordingly, an additional energy drain or damping of the track circuit signals is also prevented. 
     Advantageously, a transverse rod having the insulating coating may be formed as the lower boom of a grid support of a sleeper. A lower boom of this type can be provided with the insulating coating all over, so that at no point can there be unwanted contact with a longitudinal rod. 
     In order to minimise the construction cost, it is sufficient in the fixed carriageway according to the invention that in the case of a sleeper having plural grid supports, only one lower boom of a grid support has the insulating coating. It is particularly advantageous that the lower boom having the insulating coating has a different height position, in particular a lower height, than the other lower booms. The longitudinal rods can then rest on the shallower lower boom without contact being formed between them, and in addition the longitudinal rods are also isolated from the same lower booms, which have a normal height. 
     It can be provided that in the fixed carriageway according to the invention, additionally the sections of the grid support adjoining the lower boom may have an insulating coating. Thus also, contact between the longitudinal rods and/or vertically extending sections of the grid support of the sleeper is prevented. 
     In addition, the invention relates to a method of manufacturing a fixed carriageway for rail vehicles with sleepers embedded in a carriageway panel and reinforcement, which comprises plural longitudinal rods and transverse rods disposed in the carriageway panel parallel and transversely to the sleepers. 
     In the method according to the invention it is provided that the longitudinal rods and the transverse rods are installed electrically isolated from one another. 
     Further embodiments of the invention are indicated in the subclaims. 
     Further advantages and details of the invention are explained by means of embodiments with reference to the Figures, which are diagrammatic representations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a plan view of a fixed carriageway according to the invention in a first embodiment; 
         FIG. 1B  is a side view of the fixed carriageway shown in  FIG. 1A ; 
         FIG. 1C  is an enlarged detail from  FIG. 1B ; 
         FIG. 1D  is a section through the fixed carriageway in the region of a sleeper; 
         FIG. 2A  shows a spacer; 
         FIG. 2B  shows the spacer shown in  FIG. 2A  in a view rotated through 90°; 
         FIG. 3A  is a plan view of a fixed carriageway according to the invention in a second embodiment; 
         FIG. 3B  is a side view of the fixed carriageway shown in  FIG. 3A ; 
         FIG. 3C  is an enlarged detail from  FIG. 3B ; and 
         FIG. 3D  is a section through the fixed carriageway in the region of a sleeper. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fixed carriageway  1  shown in  FIGS. 1A ,  1 B and  1 D consists essentially of a carriageway panel  2  composed of concrete, which in the embodiment shown rests on a hydraulically bonded support layer as a substructure  3 . The substructure  3  rests on a frost-protection layer  17 . Sleepers  4 , which are formed as dual block sleepers and support the rails  5 , are embedded in the carriageway panel  2 . Each sleeper  4  comprises two parallel grid supports  6 ,  7  which are connected to concrete sleeper blocks  8 ,  9 . 
     As can be best seen from  FIG. 1A , between two adjacent sleepers, a respective transverse rod  10  is disposed as part of the reinforcement. In addition, the transversely extending booms of the grid supports  6 ,  7  act as transverse rods of the reinforcement. 
     Additionally, the reinforcement comprises longitudinal rods  11  disposed at right angles to the transverse rods and extending parallel to the rails  5 . As can be best seen from  FIG. 1D , in the embodiment shown, sixteen longitudinal rods  11  are used, which are inserted through the grid supports  6 ,  7 . Additionally, longitudinal rods  12 ,  13  are disposed at the outer ends of the sleepers  4 . 
     At points of intersection between the transverse rods  10  and longitudinal rods  11  or transverse rods  10  and longitudinal rods  12  or  13 , spacers  14  are inserted, which are clipped on to the reinforcement rods having a circular cross-section. 
       FIGS. 2A and 2B  show the spacer  14  in two views rotated through 90°. The spacer  14  consists of a first circle-segment-shaped section  15  and a second circle-segment-shaped section  16 , which is rotated through 90° with respect to the first circle-segment-shaped section  15 . The circle-segment-shaped sections  15 ,  16  can easily be clipped with their open section on to the reinforcement rods. After mounting of the spacers  14 , the two reinforcement rods, e.g. a transverse rod  10  and a longitudinal rod  11 , are kept at a fixed distance from one another. The spacers  14  are mounted before casting of the carriageway panel  2  and effect the desired electrical isolation between the longitudinally and transversely extending reinforcement rods. Two different spacers  14  are used. The spacer shown in  FIGS. 2A and 2B  is for connecting rods of different diameters, possibly for connecting a grid support to a longitudinal rod. In addition, for connecting transverse rods to longitudinal rods, spacers  14  are used in which the circle-segment-shaped sections are the same size. 
       FIG. 1C  shows an enlarged detail from  FIG. 1B  in the region of the connection of a grid support to a longitudinal rod. 
     By means of the spacer  14 , the longitudinal rod  11  is kept at a specified distance from the transversely extending lower boom  21  of the grid support, and contact and the formation of an electric circuit between the transverse rods  10  and the longitudinal rods  11  is prevented. It is sufficient if the spacers  14  are clipped on to one transverse rod  10  or to one lower boom of a grid support, since thus the other lower booms are electrically isolated from the longitudinal rods. 
     The two outer longitudinal rods  12 ,  13  resting on the transverse rods are likewise separated and isolated from the transverse rods  10  by the spacers  14 . Two spacers are used per gap between sleepers. The transverse rods in each sleeper gap are likewise isolated by spacers from the longitudinal reinforcement extending below, four spacers being used per transverse rod  10 , as can be seen in  FIG. 1A . 
     In addition, the longitudinal rods are also separated from one another in the overlap region by two spacers  14  respectively. The overlap region in the example shown is about 1.2 meters, the individual longitudinal rods  11  being in this case 14 meters long, so that sections having this length are produced which are electrically isolated from one another. The measurements indicated are not to be considered limiting, however, but may be varied depending on the particular requirements. 
     In  FIGS. 3A to 3D , a second embodiment is shown. Where the components correspond to those of the first embodiment, the same references are used. 
     Corresponding to the first embodiment, the sleepers  4  are embedded in the carriageway panel  2 . The reinforcement comprises transverse rods  10  and longitudinal rods  11 , which are passed through the grid supports  7 ,  22 . 
     At some points of intersection between transverse rods  10  and longitudinal rods  11 , spacers  14  are clipped on. The same applies to the overlap region of the longitudinal rods  11 . 
     Unlike in the first embodiment, the grid support  22  of the sleeper has a lower boom  18  with a low height, i.e. this lower boom  18  in the installed state lies higher than the other three lower booms  19  of the sleeper. As can be seen in  FIG. 3C , the lower boom  18  has a continuous coating, which extends obliquely upwards along the obliquely extending grid rods  20  of the grid support  22 . The coating consists of a plastics material, in this case an epoxy resin. In other embodiments, the coating may consist of a thermoplastic material or another suitable material. As can be seen in  FIG. 3C , the longitudinal rod  11  rests on the lower boom  18  and can touch the coated region of the grid rod  20  laterally. By means of the coating, the lower boom  18  and the grid rod  20  connected thereto are electrically isolated from the longitudinal rod  11 , and accordingly the formation of short-circuit paths is prevented. 
     In the embodiment shown, the shortened lower boom  18  of the grid support  22  has a grid support height of 100 mm, whereas the other lower booms are 110 mm high, so that the longitudinal rods  11  only rest on the shortened lower boom  18 . 
     In the method of manufacturing the fixed carriageway, the sleepers are positioned as usual with their grid supports and the transverse rods and longitudinal rods of the reinforcement, and then the spacers are mounted. The other steps in the sequence of the method of construction are not altered, but only the modified grid support  22  is used, which is shown in  FIGS. 3A to 3D .