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BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention lies in the railway technology filed. More specifically, the invention relates to a device for setting symmetry in a railway switch system which is installed in particular in a rail sleeper and which has a drive rod and in each case a cam rod connected to a switch blade. The cam rod and the drive rod can be fixedly connected to one another with locking means. 
     Railway switches are subjected to severe stresses due to influences of the weather and as a result of trains traveling over them. This can result in changes in the adjustments and settings made at the time of mounting. In particular, uniform coverage of closure catches which are assigned to the switch blades are to be ensured by means of an adjustment. In the text which follows, the term adjustment as used here is understood to also refer to the setting of symmetry in a railway switch system. 
     U.S. Pat. No. 5,620,156 (international PCT publication WO 94/27853) describes a modular railway switch system which is integrated into a hollow sleeper and which is composed of individual modules, which can to a certain extent be optionally replaced. 
     A railway switch system typically has at least one drive rod which transmits the longitudinal movement generated by a railway switch drive to the switch blades. Switch blades are themselves generally connected to one cam rod each in this context. Because most railway administrations demand a further electrical insulation means between the left-hand and right-hand switch blades as well as further insulation from the drive rod, an attachment part which is arranged in an insulated fashion and which permits force to be transmitted from the drive rod to the cam rod is provided. The spatial conditions are very limited in a hollow sleeper. As a result, the accessibility of the components is made much more difficult. Necessary re-adjustments are consequently associated with the removal of individual components or modules and with tedious manual work. However, the initial mounting and adjustment can also be considerably adversely affected by the tight spatial conditions. In such a context, it should be possible to make the settings to a resolution of approximately 1 mm. 
     It is also desirable to be able to use parts of railways switch systems repeatedly, and function components should thus be independent of the respective design and dimensions. In particular it is desirable for parts to be capable of being used independently of the track gauge. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a device for setting the symmetry in a rail point switch, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which permits adjustment and setting of symmetry in the railway switch system to be carried out flexibly and easily and with the required resolution. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a device for setting symmetry in a railway switch system, comprising: 
     a drive rod; 
     a cam rod connected to a switch blade of a railway switch system; and 
     a locking device releasably locking said cam rod and said drive rod to one another; 
     wherein, with said locking means released, said cam rod and said drive rod are displaceable relative to one another in grid steps, and said locking device is configured to lock said cam rod and said drive rod with a positive lock. 
     In other words, by virtue of the fact that the cam rod and the drive rod can be displaced relative to one another in a grid when the locking device is released and can be fixedly connected to one another using the locking means by means of a positive lock, the setting of symmetry in a railway switch system can easily be performed with the grid corresponding to the required resolution. 
     In this way, the following advantages can be additionally be obtained: 
     i) With an attachment flange embodied as a center attachment or as a side attachment it is possible for the device according to the invention to be applied for standard gauge, wide gauge and even narrow gauge railway switch systems. 
     ii) Coarse adjustment can be achieved with two bore holes and/or by means of an asymmetrical arrangement of the bore holes in the attachment element, and permits flexible adaptation to the respective gauge. 
     iii) A taper in the bearing bolt prevents rotary application of force to parts of a railway switch system, said rotary application of force being brought about by a change in length of the switch blades owing to temperature fluctuations over the years. 
     iv) The positive lock formed by means of key tracks and associated adjustment keys and a main key ensures frictional coupling between the drive rod and cam rod even when the locking screws are partially released. 
     v) The protection plate forms a double protection function: it prevents the locking screws being released and prevents lateral displacement of the adjustment keys and of the main key. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a device for setting symmetry in a railway switch system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
    
    
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the device according to the invention for setting symmetry in a railway switch system in the mounted state; 
     FIG. 2 is an enlarged perspective detail of the device according to the invention in the released state; 
     FIG. 3 is a perspective view of the device according to the invention for setting symmetry in an embodiment for relatively small gauges; 
     FIG. 4 is a sectional view through an attachment element with bearing bolts and a drive rod being illustrated; and 
     FIG. 5 is a perspective detail view of the device according to the invention in the embodiment for relatively small gauges with the protection plate removed. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a device according to the invention for setting symmetry in a railway switch system in the mounted and operational state, installed in a hollow rail sleeper  100 . The embodiment is preferably provided for the standard gauge, i.e., for the standard gauge of 1435 mm. Cam rods  5  which are each connected to a switch blade  22  (see FIG. 3) are coupled to what is referred to as an attachment flange  2  by means of screwed connections—each formed from a connection screw  15  and connection nut  16 —via insulating plates  14 . The attachment flange  2  is referred to below in this embodiment as a center attachment  2 . The center attachment  2  is of the symmetrical design with respect to the axis of the track and has a significantly greater cross section in the center part. A penetrating locking slit  4  is milled into the center part and has two plan-parallel faces. An attachment element  1  with the center attachment  2  is connected to locking screws  13 , the attachment element  1  being displaceable relative to the center attachment  2  in the released state. Details of this are found in FIG.  2 . 
     A bearing bolt  11  is guided through a bore hole  9  or  10  and is guided in the slit S 1  by means of a drive rod  20  (see FIG. 4) and thus permits force to be transmitted from the drive rod  20 , via the attachment element  1 , the center attachment  2 , and the cam rods  5 , to the switch blades  22 . In order to prevent the locking screws  13  being released as a result of vibration, the protection plate  12  is provided which in this embodiment has openings which are fitted over the hexagonal heads of the locking screws  13  and over the center part of the center attachment on each side. In order to be able to bring about a connection which is defined by means of a torque key, for example, such an opening is formed by punching a hexagon twice in such a way that before the second punching operation a rotation of the tool through 30° relative to the protection plate is performed. As a result, the tightening of the screws can be performed with a resolution of approximately 30° and the locking screws  13  can be reliably protected against spontaneous release. As a result of the fact that the locking screws  13  are easily accessible from above, adjustment can easily be performed at the time of the first mounting or when maintenance is performed on the railway switch. 
     FIG. 2 shows a detailed view of the device according to the invention in a released and partially disassembled state. In order to ensure a stable connection between the center attachment  2  and the attachment element  1 , a clamping plate  6  is provided. The locking slit  4  is dimensioned, for example, in such a way that in each case a displacement of, for example, 16 mm can be achieved as a desired relative position from a symmetrical center position. The bore holes  9  and  10  through which in each case a securing bolt  11  is plugged in order to connect to the drive rod  20 , are arranged asymmetrically. As a result, a relatively large grid-like displacement, as a first, so-called coarse setting of for example 32 mm, can be achieved only by arranging the attachment element  1  offset through 180°. 
     A positive lock (i.e., a form lock) is provided between the center attachment  2  and attachment element  1  in accordance with the illustration in FIG. 1 as follows: the center attachment  2  has, transversely with respect to its direction of movement in the railway switch system, a continuous key track  19 , for example with a width of 8 mm, in the lower part of the center attachment  2 . The attachment element  1  itself also has, on its upper part between the threads provided for the locking screws, a key track  18 . The latter is, however, considerably wider than the key track  19  of the center attachment  2 . By way of example, the key track may have a width of 32 mm. These two key tracks permit a grid-like displaceability by means of the connections (shown in FIG. 1) of attachment element  1  and relative to the cam rod  5 , by means of a key part  7  and a plurality of adjustment keys  8  (also referred to as intermediate bearings). In other words, the displacement is in discrete steps, i.e., the adjustability is discrete instead of infinite. The adjustment keys  8  are configured in various widths. In the dimensioning example here having the width 8 mm for the center attachment  2  and 32 mm for the attachment element  1 , the remaining 32 mm−8 mm=24 mm are configured as follows: 
     Three (3) attachment keys with a width of 8 mm each. 
     Eight (8) attachment keys with a width of 1 mm each (illustrated “filled-in” in FIGS.  2  and  5 ). 
     As a result of this dimensioning of the adjustment keys  8  which is given by way of example it is possible to set symmetry in a railway switch system in a range of 32 mm with a resolution of 1 mm, i.e., in finite steps of 1 mm. Together with the asymmetrical arrangement of the bore holes  9  and  10  relative to the center of the key track  18 , this thus results in additional stepped displaceability in a range of 64 mm relatively between the drive rod and switch blade. Further displaceability is obtained by the use of bore hole  9  or bore hole  10  for receiving the bearing bolt  11 . In this way, it is possible to provide just one bore hole for receiving the bearing bolt  11  in the drive rod  20 , and this also has advantageous effects for the maintenance of the bearings. 
     FIG. 3 shows a view of the device according to the invention for setting symmetry in an embodiment for relatively small gauges, for example 1000 mm. With relatively small gauges, the center attachment  2  can, in particular, no longer be placed using standardized components. The attachment flange  2  for the connection between the drive rod  20  and cam rod  5  is instead arranged outside the region defined by the two rails  23  and switch blades  22 . In this advantageous embodiment, a side attachment  3  is provided as attachment flange. In this embodiment, the attachment element  1  is modified with respect to the asymmetric arrangement of the bore holes  9  and  10  for receiving a bearing bolt  11  in comparison with the attachment element  1  in accordance with the embodiments shown in FIG. 1 in two ways: the bore holes  9  and  10  are still arranged asymmetrically but the attachment element  1  according to FIG. 3 has, in contrast with the illustration in FIGS. 1 and 2, no oblique rib  28 . The second modification relates to the width of the key tracks  18  in the attachment element  1  and a key track  19  in the side attachment or center attachment  2 . This embodiment of the key tracks can be seen in the illustration in FIG.  5 . The key track of the side attachment has, according to the abovementioned dimensioning example, a width of 32 mm, while the key track in the attachment element  1  is provided merely for receiving the main key  7  with a width of 8 mm. Consequently, in the embodiment according to FIG. 3, the locking slot  4  is milled into the attachment element  1 . However, preferably just one embodiment of the attachment element for various gauges is used, and correspondingly it only needs in each case just one corresponding embodiment of the center attachment  2  or of the side attachment  3 , which are referred to in this document by the term attachment flange. The insulated connection between the two cam rods  5  is illustrated on the right in FIG.  3  and embodied in a comparable way as can be inferred in particularly from the description in FIG.  1 . 
     The protection plate  12  has, in addition to the already mentioned protection function for the locking screws  13 , a further function: the main key  7  and adjustment keys  8  are thus protected against lateral displacement. The protection plate  12  is preferably of identical design for the side attachment  3  and center attachment  2 . The protection plate is U-shaped in cross section with an indent toward the end of the U. It is fitted over the attachment flange  2 ,  3  and protected against inadvertent release with frictional locking thanks to the indent. 
     Railway switches, in particular the switch blades, are subjected to considerable changes in length due to seasonal temperature fluctuations. The structure of railway switch systems must therefore take into account a change in length of the order or magnitude of 150 mm to 200 mm depending on the radius of the deflecting direction of the railway switches. With a rigid design—in particular with a design with a center attachment—such a change in length can exert a considerable application of force to the center attachment  2 , and thus also to the drive rod  20 . In both designs with a center attachment  2  or side attachment  3 , there is therefore provision, in a further particularly advantageous embodiment of the invention, to make the bearing bold  11  tapered. FIG. 4 illustrates a double taper, i.e. arranged in pairs, of the bolt diameter with the reference symbol S 2  in a sectional view through an attachment element. The taper relates in this embodiment to that region of the bearing bolt  11  which engages in the drive rod  20 . As a result, a small degree of rotatability of the drive rod  20  relative to the attachment element  1  transversely to its direction of activation is ensured. This taper can be embodied in a precisely circular shape or only in a substantially circular shape, for example with a radius of 75 mm. Where the two tapers meet a preferably convex shape (in section) is selected which is formed, for example, with a radius of 25 mm. This position is in each case the main attachment point of the application of force between the bearing bolt  11  and drive rod  20 . 
     FIG. 4 also shows a threaded bolt  24  for the disassembly—also referred to as removal—of the bearing bolt  11 . As a result of the mechanical stress and as a result of contamination effects, the bearing bolt  11  may be capable of being pulled off only under the effect of the force. In such a case, the bearing bolt  11  can be removed by means of a screw which is to be screwed into the threaded hole  24 . FIG. 4 also shows the head  25  and a hole  26  in the bearing bolt. The head  25  can be cylindrical or in the form of a hexagon. The hole  26  is used to receive a detent spring  27  or a cotter pin  27 . When dimensioning the width of the attachment element  1  and the length of the bearing bolts  11 , the restricted width of the hollow sleeper is to be taken into account in such a way that removal by hand is easily possible, in particular it is necessary for sufficient clearance to be present on both sides for the bearing bolt  11  and the main key and the adjustment keys  8  to be capable of being inserted and extracted easily. The bolt  11  projects through a bore  21  formed in the rod  20 . 
     The positive lock described for the side attachment  3  and center attachment  2  by means of the key tracks has the advantage that in the event of the protection plate being lost and the locking screws  13  having already been released, force can still be transmitted between the drive rod  20  and cam rods  5 . 
     The positive lock described above between the attachment element  1  and attachment flange  2  or  3  is not restricted to this embodiment with the aforementioned key track, main key  7  and adjustment keys  8 . Other positive locks which are embodied in a rib-like fashion are also conceivable. Such a positive lock can be embodied, for example, as also referred to as an indented connection, for example the areas of the attachment element  1  and attachment flange  2  or  3  which bear one against the other have a saw-tooth shape in cross section, two successive peaks of the saw tooth being spaced apart by the distance required for the resolution, this distance being typically 1 mm. 
     The structural implementation is also possible in such a way that certain of the abovementioned parts are embodied as a single component; in this way the attachment element  1  and drive rod  22 , for example, can thus be provided as a single component.

Summary:
Railway switches are subjected to a high degree of stress due to the influences of weather and as a result of trains traveling over them. This may result in changes in adjustments and settings made at the time of mounting. In order to permit, in particular in the case of hollow sleepers, simple re-adjustment of a drive rod relative to the cam rods, an attachment element can be connected to an attachment flange by a positive lock, formed by various adjustment keys and a main key, and using locking screws in such a way that fine adjustment by appropriately selecting the arrangement of the adjustment keys is possible. Coarse adjustment is made by an asymmetric arrangement of the bore holes for connecting to a drive rod as well as by selecting one of the two bore holes.