TRACK SLAB FOR A RAIL TRACK, AND METHOD FOR ATTACHING IT

Abstract: A rail track system of the embedded rail type is described, wherein rails (104) are completely enclosed in a track slab (102). The track slab is attached to a support structure (12) by means of coupling members (20), which coupling members allow axial displacement of the track slab with respect to the said support structure. The track slab has side support ribs (112) which support the rails on their outer side. The attachment of the rails to the track slab is established by means of positioning blocks (120, 130) which are positioned between the rails. The positioning blocks can clamp the rails securely against the supprot ribs, but the rails may also be cast into the space between the positioning blocks and the support ribs.

Description: Title: Track slab for a rail track, and method for attaching it The invention relates in general terms to rail tracks, in particular for rail-borne vehicles and/or magnetic trains. More particularly, the present invention relates to a support structure for such a rail track, comprising a substantially plate-shaped, preferably concrete core, which will also be referred to in the following text by the term "track slab". For rail-borne vehicles, a track slab of this nature is provided on its top side with two parallel groove-like rail-holding spaces. Such a track slab has already been described in Dutch Patent 1009538 dated 22 July 1998 of the same inventor. This track slab is part of a rail track structure of the so-called "embedded rail" type, wherein a rail is enclosed over its entire length and over a certain part of its height in the groove-like rail-holding spaces, in contrast to conventional systems wherein the rail is attached at regular intervals, by means of clamping members, to a base such as railway sleepers or a flat concrete track slab. There is a need for a rail track structure wherein the rails are seamless, continuous bars over a very great length. Furthermore, it is desirable for these seamless rails to be incorporated as embedded rails in a concrete track slab. Consequently, the concrete track slab, which is composed of slab segments positioned one behind the other in the longitudinal direction and attached to one another, have to act as a single continuous, seamless concrete slab. To prevent a track slab of this nature breaking as a result of variations in length caused by temperature variations, it is known to provide the track slab, at predetermined locations with regular intervals between them, with weakened areas in the form of seams, which can be regarded as crack-initiation points. This solution has proven itself in practice, but can only be employed with success in situations wherein the track slab is laid on an earth track. If the track slab is mounted on a concrete track structure such as for example a bridge, it is customary that separate, relatively short track slab segments are rigidly connected to the rail track structure, each slab section behaving as a single unit with the bridge. In this case, variations in length of the bridge caused, for example, by temperature variations are absorbed by each slab segment moving with the bridge, the structure for attaching the rail in the track slab segments then being designed in such a manner that each rail can slide in the longitudinal direction with respect to the track slab. However, a number of drawbacks are associated with this known structure. Firstly, it is difficult in this way to absorb great local variations in length, such as those which may occur, for example, at the expansion joints of a bridge structure. Another problem is that for the comfort of the ride in a train, it is desirable that the distances between the successive clamps by means of which the rails are fixed to the track slab are equal to one another, as far as possible. In practice, it is stipulated that these distances must lie within a range of from 58 to 65 cm. In general, it is possible to state that changes in the supporting distance are undesirable. Then, in order to adapt the track slab segments, which should preferably be identical to one another in order to reduce production costs, to the pattern of the rail attachment points of the entry and exit section, the track slab segments have to be designed and made to measure specifically for each bridge, making the track slab segments relatively expensive. Further, a further problem with track slab structures in general, when they are laid on earth, is that there may be a certain amount of subsidence over the course of time. In principle, some degree of subsidence, if it is spread over a large length of track, does not present any problem. This situation changes if subsidence occurs at a part of a track laid on an earth track close to a bridge structure. The bridge structure will be very securely anchored to the fixed world and will not subside, while the adjoining earth-laid track can subside. Therefore, there will then be considerable local differences in subsidence, which can be felt in the track as a bump, which is out of the question, in particular for high-speed trains. Therefore, there is a need for the possibility of readjusting the track height. In the case of known embedded rail systems, this is difficult or altogether impossible. Similar problems arise with the positioning of track slabs for magnetic trains. In general, the present invention aims to solve the above problems . A further object of the present invention is to provide a concrete track slab which combines the advantages of an embedded rail, a relatively simple fitting of rails in the track slab, a relatively simple accessibility to the rails after they have been fitted, a derailment protection integrated in the track slab, and a sound absorption integrated in the track slab. According to an important aspect of the present invention, the track slab is installed in such a manner with respect to the ground beneath it that it can slide at least slightly with respect to this ground. The height and the width position of the track slab can be adjusted with respect to the ground, and an elastic support can be accommodated between the track slab and its support. Advantageously, standard rail clamps are used to install the track slab, of the type normally used to fit a rail to, for example, a railway sleeper, but in this case usedto attach a track slab to its support . According to another important aspect of the present invention, the rails are enclosed in the track slab by means of separate pressure blocks which also fulfil the function of protection against derailment and sound insulation. It is noted that it is already known from US-A-5.806.764 to design a rail track structure as a baseplate with upright support ribs for supporting the outer sides of the rails, the rails being held in place by a positioning block arranged between these rails. According to this known technique, there is only one single positioning block present between the rails, measured in the width direction of the track, and the rails are clamped floatingly between the said one positioning block and the upright support ribs. However, placing such a positioning block is particularly difficult, on the one hand because the rails have to be held in their floating position, and on the other hand because the side edges of the positioning block are profiled in order to fit into the profile of the rails. In the rail track structure which is proposed by the present invention, the number of positioning blocks, measured in the width direction of the track, is at least equal to three. A larger number is also conceivable, in which case the number is preferably odd. It is then possible firstly to place the rails onto the baseplate, then to place the outermost positioning blocks, and finally to place a central positioning block which secures all the other positioning blocks as well as the rails. In this context, it is particularly advantageous if this central positioning block is in the shape of a trapezium. Furthermore, it is pointed out that it is already known per se from US-A-5.464.152 to clamp the rails, at a track transition, solely for the purpose of sound insulation of the rails, between upright edges arranged on a baseplate, on one side, and clamping blocks fitted to this baseplate, on the other side. In this case, however, the number of clamping blocks, measured in the width direction of the track, is equal to two. This has the drawback that, to allow the second block to be installed, there must be a gap between the two clamping blocks, and each of the clamping blocks has to be individually anchored to the baseplate. Therefore, there is no force-fitting securing from one rail to the other. In the structure which is proposed by the present invention, the positioning blocks are supported against one another and the two rails are positioned in a force-fitting manner between the two upright support ribs . These and other aspects, characteristics and advantages of the present invention will be explained in more detail by the following description of a preferred embodiment of a track slab according to the invention, with reference to the drawing, in which identical reference numerals denote identical or similar components, and in which: figure 1 diagrammatically shows a cross section of a rail track structure according to the present invention; figures 2A-B diagrammatically show a clamping member for a track slab; figure 3 shows a cross section similar to that shown in figure 1, of a preferred embodiment of a rail track structure according to the present invention, in which positioning blocks are used; figure 4 clarifies a preferred detail from figure 3 on an enlarged scale; figure 5 shows a cross section similar to that shown in figure 3 of another preferred embodiment of a rail track structure according to the present invention, in which positioning blocks are used; figures 6A-C diagrammatically show plan views of a preferred embodiment of a rail track structure according to the present invention, with various possibilities for the configurations of positioning blocks; figures 7A-C diagrammatically illustrate an advantage of using the present invention; and figures 8A-C diagrammatically illustrate an embodiment of the present invention, used in a track which is intended for magnetic trains . Figure 1 diagrammatically shows a cross section of a rail track structure 1 according to the present invention which is particularly suitable for high-speed trains. The rail track structure 1 comprises a concrete track slab 2 which on its top side is provided with two parallel rail-holding grooves 3 (see the left- hand half of figure 1) . A rail 4 is fixed in each rail-holding groove 3 by means of a casting material 5 (see the right-hand half of figure 1) . The track slab 2 is mounted on a support structure which is denoted in general by the reference numeral 10. In the example illustrated, this support structure 10 comprises longitudinal support ribs 11 which, in turn, may be arranged on earth but, in the example illustrated, are formed on the bottom of a concrete casing 12 which is substantially U-shaped in cross section. As an alternative, the elongate support ribs 11 could be mounted on piles, resulting in considerable savings on the costs of the support structure 10. If the support structure 10 comprises a concrete casing 12, the support ribs 11 could be omitted, and the track slab 2 can be mounted directly on the bottom of the said concrete casing 12. By using support ribs 11 as shown, however, it is easier to fit the track slab 2 with a certain transverse slope with respect to a concrete casing 12 which is otherwise lying horizontal, as shown in figure 1. According to an important aspect of the present invention, the track slab 2 is not attached rigidly and in a fixed manner to the support structure 10, as is customary, but by means of clamping members 20 which allow readjustment of the attachment in the vertical and/or width direction and which, furthermore, provide vibration damping. As shown in more detail in figure 2A, the clamping members 20 comprise a sandwich structure formed by a bearing shell 21, preferably made from metal, and an elastic plate 22 positioned beneath it and preferably made from rubber or the like, beneath which there is in turn preferably a rigid baseplate 23, for example made from plastic or metal. The sandwich structure of the bearing shell 21, elastic plate 22 and baseplate 23 is rigidly fixed to the support structure 10 by means of a bolt 24. The bolt 24 extends through respective assembly holes in the bearing shell 21, in the elastic plate 22 and in the baseplate 23, which assembly holes are not shown separately in figure 2, for the sake of clarity. To make it easier to adjust the complete sandwich structure of the bearing shell 21, the elastic plate 22 and the baseplate 23 in the direction perpendicular to the longitudinal direction of the track, there is preferably provided a cylindrical adjustment sleeve placed in the said assembly holes, which at its top end has a radially projecting collar which rests on the top surface of the bearing shell 21, and which has an axially oriented bore which is eccentrically positioned and through which the said bolt 24 extends. In this case, the said sandwich structure is adjusted with respect to the fixed screwhole in the base through rotation of the adjustment sleeve, for which purpose the collar of the adjustment sleeve may be provided with a profile, such as a hexagon shape, for a tool, such as an open-end spanner, to engage on. The track slab 2 rests on the bearing shell 21, as will be described in more detail below, and is therefore coupled to the rigid support structure 10 via the bearing shell 21, the elastic plate 22 and the optional baseplate 23. By the presence of the elastic plate 22 between the track slab 2 and the support structure 10, a vibration damping between the track slab 2 and the support structure 10 is achieved. By this is achieved that a vibration- damping or resilient bearing between the rail 4 and the track slab 2 can be dispensed with or at least considerably reduced. The damping characteristic of the track slab 2 with respect to the support structure 10 can easily be adapted through replacement of the elastic plate 22; by way of example, the elastic plate 22 could be replaced by a thicker or thinner plate. Furthermore, the height of the track, that is to say the height of the rail 4 with respect to the fixed world, can easily be varied through replacement of the baseplate 23; by way of example, the track (rails 4) could be lifted relatively easily with respect to the fixed world by replacing the baseplate 23 with a thicker one. On its top side, the bearing shell 21 has a bearing surface 29 on which the track slab 2 rests. Preferably, and as shown, a plate 32 made from a hard plastic material or the like is arranged between the bearing surface 29 of the bearing shell 21 and the underside of the track slab 2. This plate 32 may be arranged in a recess in the top surface of the bearing shell 21. The bearing surface 29 adjoins an elevated rib 25 which forms a stop or lateral position-limitation for the track slab 2. The track slab 2 is held in place with respect to the bearing shell 21 by a clamping bracket 26 which, by means of a clamping bolt 27 which has been screwed into the rib 25, exerts a substantially downwardly directed clamping force on a foot 30 formed on the underside of the track slab 2. The foot 30 may be formed as an integral component of the track slab, from the same material, if this material is sufficiently strong. In the embodiment shown, the foot 30 is designed as a metal profile which is attached to the track slab 2 and has a toe 31 projecting horizontally with respect to the track slab 2. As an alternative, the track slab 2 may be provided, in its side wall, with a recessed niche for accommodating the clamping bracket 26, in which case the total width of track slab 2 plus clamping members 20 can be reduced. Figure 2B shows a diagrammatic side view of the clamping members 20. It is advantageously possible to use a standard rail- attachment bracket for the clamping bracket 26. By this clamped attachment, the track slab 2 can move in the longitudinal direction with respect to the support structure 10. As a result, the rail 4 can be installed in a fixed position with respect to the track slab 2, i.e. that the track slab 2 together with the rails 4 behaves as a continuous, integral unit. The continuous unit of track slab 2 with rails 4 thus produced may also extend over, for example, a bridge structure, since variations in the length of the bridge structure are evened out by the fact that the track slab 2 and the support structure 10, i.e. in this example the bridge structure, can slide with respect to one another, so that variations in length of this nature have no influence on the rails and the track slab. Figure 3 illustrates a further aspect of the present invention, and figure 4 illustrates a detail thereof. Figure 3 shows a diagrammatic cross section of a track slab 102 which, by means of clamping members 20, is directly attached to the base of a concrete casing 12. The clamping members 20 may be identical to those which have been discussed with reference to figure 2A and will not be described in more detail here. The track slab 102 comprises a substantially planar baseplate 110. Along the longitudinal edges of the baseplate 110 there are two support ribs 112 which extend upwards with respect to the top surface 111 of the baseplate 110. The baseplate 110 and the support ribs 112 are produced integrally as a single moulding. As will be described in more detail below with reference to figure 4, two rails 104, the outer surface of which is supported against an inner surface 113 of a respective support rib 112, are positioned on the top surface 111 of the baseplate 110. In this context and also in the following text, a direction which is directed towards the central plane M of the track slab 102 will be indicated by the term "inner", and a direction which is directed away from this centre plane M will be indicated by the term "outer". Separate positioning blocks 120, 130 and 120' are positioned on the top surface 111 of the baseplate 110, between the rails 104. These positioning blocks are in direct or indirect contact with the rails 104 and thus confine the rails 104 in the lateral direction between the positioning blocks and the support rib 112. In this case, therefore, a rail-holding space 3 (figure 1) is defined by the distance between a positioning block and a support rib. Although the rails 104 may in principle have any suitable contour, they are preferably of standardized shape with a foot 105, a central body 106 and a head 107, as shown in more detail in figure 4. The inner surface 113 of each support rib 112 has a contour which is matched to this shape, in such a manner that the outer surface of the rail 104 is in contact with the inner surface 113 of the support rib 112 over almost its entire height. More particularly, it is clearly shown in figure 3 that the entire height of the body 106 and even part of the head 107 bears against the profiled inner surface 113 of the support rib 112. In the same way, the outermost positioning blocks 120 and 120', which in principle are identical to one another but are arranged mirror- symmetrically, have an outer contour which corresponds to the inner contour of the foot 105 and the body 106 of the rail 104. By using such positioning blocks 120, 120' and 130, a surprisingly quick and easy installation of the rails 104 on the track slab 102 is possible. In brief, it boils down to putting the rails 104 down onto the baseplate 110 of the track slab 102 and pushing them outwards, the foot 105 of the rail 104 fitting into a recess in the support rib 112 intended therefor. Then, the outermost positioning blocks 120 and 120' are placed onto the top surface 111 of the baseplate 110 and are pushed outwards, so that their outer surface comes to bear against the rail 104. Finally, the central positioning block 130 is installed, which holds the two outermost positioning blocks 120 and 120' in place. Herein, it is advantageous if the central positioning block 130 has a wedge function by the fact that the central positioning block 130, in cross section, substantially has the shape of an inverted trapezium, that is to say that the side walls 131 of the central positioning block 130 form an angle greater than 0° with the vertical, so that the horizontal transverse dimension of the central positioning block 130 in the vicinity of its bottom surface 132 is smaller than its horizontal transverse dimension at its top surface 133. The innermost side walls 121 of the outermost positioning blocks 120 and 120' have a corresponding inclination. The central positioning block is preferably screwed securely onto the baseplate 110 by means of one or more attachment bolts 135. Preferably, elastic strips 136 are arranged between the central positioning block 130 and the two outermost positioning block 120 and 120'. These elastic strips 136 primarily serve to absorb variations in width caused by temperature variations. Although the elastic strips 136 may inherently be separate components, they are preferably attached to the inner side wall 121 of the outermost block 120 or to the side wall 131 of the central positioning block 130. Preferably, and as illustrated, the positioning blocks 120, 130, 120' are provided on their underside with projections 137 which may be produced as a whole with the positioning blocks, from the same material of these blocks, but which may also be made from a different material, for example from plastic or the like, and may be fixed to the bottom surface of the positioning blocks, for example by adhesive bonding. The primary purpose of these projections 137 is to prevent direct contact between the positioning blocks and the baseplate 110 and to define a horizontal gap-like space 142 between the baseplate 110 and the positioning blocks in order to enable water to flow out. Rainwater which falls onto the rail track can flow down between the positioning blocks 120 and 130 via the gap space which is defined between the positioning blocks 120 and 130 by the elastic intermediate strips 136, in order to reach the said gap-like space 142, and can be discharged from this gap-like space 142 through vertical bores 143 in the baseplate 110. The positioning blocks 120, 120' and 130 may preferably also be designed for a sound-absorbing effect. For this purpose, the positioning blocks 120, 120' and 130, which may advantageously be designed as solid concrete blocks, may be provided in their top surface with a recessed section in which sound-absorbing elements 140 are accommodated. Such sound-absorbing elements 140 may, for example, be designed in the form of a cast mass and may be made, for example, from the materials rubber, foamed plastic or cellular concrete or the like. The sound-absorbing elements 140 may also extend over the entire top surface of the positioning blocks. The outermost positioning blocks 120 and 120' are preferably also designed to fulfil the function of protecting against derailment. For this purpose, their height is such that their top surface is situated at a higher level than the top surface of the head 107 of the rail 104. This difference in height is preferably approximately 36 mm. The top surface of the outermost positioning blocks 120 and 120' has an outer edge which is situated at a distance from the inner edge of the head 107 of the rail 104, which distance preferably amounts to approximately 70 mm. The positioning blocks 120 and 120' are profiled at their outer edge, in order to define a flange-receiving space 122 for the flange (not shown) of a rail-borne wheel travelling along the rail, which flange-receiving space 122 is defined by a first, substantially vertically oriented wall section 123 of the positioning block 120, which extends downwards from the said outer edge of the top surface, and a second, substantially horizontally oriented wall section 124, which is situated at approximately the level of the bottom of the head 107 of the rail 104. By this profiling, and in particular by the inner wall of the flange-receiving space 122 which is defined by the first side face 123, protection against derailment is provided in that it is prevented that a wheel of a passing train leaves the rail 104. If desired, the positioning blocks 120 and 120' in this area may be reinforced by a profiled metal plate 125 attached to the positioning blocks, as shown. Figure 4 shows a cross section of a rail 104 and part of the track slab 102 and a positioning block 120 on an enlarged scale. In figure 4 is clearly shown that an elastic material 151 is arranged between the support rib 112 of the track slab 102 and the rail 104. Such an elastic material is also arranged between the outer surface of the positioning block 120 and the inner surface of the rail 104. This elastic material 151 has, inter alia, a sounddamping function. In principle, it is possible to apply the said elastic material in advance onto the support rib 112 and the positioning block 120 or onto the rail 104 which is to be installed. However, an option may be to first place the rail 104 and the positioning blocks 120, 120' and 130, with a gap-like space remaining between the rail 104 and the support rib 112 of the track slab 102, on the one hand, and between the rail 104 and the positioning blocks 120 and 120', on the other hand, which gap-like space can be maintained by spacer blocks or filler blocks which, for the sake of simplicity, are not shown, and which gap-like space can subsequently be filled with a casting compound 151 which sets. Preferably, and as illustrated in figure 4, the rail 104 is not supported directly on the top surface 111 of the baseplate 110 of the track slab 102, but rather the foot 105 of the rail 104 is positioned in a channel profile 152 which is preferably made from plastic and is substantially U-shaped in cross section, wherein a resilient mass 154 may be arranged on the base 153 of this profile 152. During assembly, this channel section makes it easier to slide the rail 104 horizontally in the direction of the support rib 112. The outermost upright wall 155 of the channel profile 152 may form a stop in the horizontal direction for the foot 105 of the rail 104, supported by the support rib 112, whereby said gap-like space between the support rib 112 and the rail 104 can be defined without the need for separate spacer blocks. The innermost upright wall 156 of the channel profile 152 functions as a bearing rim for the positioning block 120 and also closes off the gap-like space between the positioning block 120 and the rail 104, so that when a casting compound 151, such as for example a UV- resistant polyurethane casting compound which is known per se, is poured into said gap-like spaces on either side of the rail 104, it is effectively prevented that this casting compound, which is still in liquid form, flows away in said gap-like space 142 between the baseplate 110 and the positioning blocks 120, 130 and 120'. It will be clear that when using a casting compound 151, the positioning blocks 120 do not exert any clamping pressure on the rails 104. If appropriate, such a clamping pressure can still be applied, once the casting compound has set, by tightening the bolt 135 slightly: as a result, the central positioning block 130 is pulled downwards slightly, whereby, owing to the inclined side walls 131 and 121, a force with a horizontally outwards directed component is exerted on the outermost positioning blocks 120 and 120' . It will be clear that the rails 104 can thus be fitted relatively easily to a track slab 102 and can be held in place particularly effectively by the combination of the positioning blocks 120 and the support ribs 112. Although in the transverse direction the number of positioning blocks may in principle differ from three, with an odd number being most suitable, the discussed example of three positioning blocks represents a preferred embodiment . Figure 5 diagrammatically shows a variant of a track slab 102 with positioning blocks 120, 130, wherein the support structure 10 and the clamping members 20 are omitted. As seen in the width direction, this track slab 102 has shoulders 108 which extend outwards beyond the support ribs 112, in order to give the track slab 102 a greater degree of stability, making it more suitable for use on earth. The rails 104 here have a shape which is substantially symmetrical with respect to a horizontal plane, so that their contour is substantially 8-shaped. As can be seen clearly from the exploded view in the right-hand half of the figure, the rail 104 may be accommodated in a prefabricated, elastic body 157 of suitable profile, which fulfils the functions of casting compound 151 and installation channel 152. In figure 5 is also illustrated that the contours of the inner wall of the support rib 112 and the outer wall of the rail 104 do not have to precisely correspond to one another, but rather the casting compound 151 and/or the elastic body 157, respectively, can bring about an adjustment to the contours. The same applies to the contours of the outer wall of the outermost positioning blocks and the inner wall of the rail 104. In practice, the track slab 102, as stated, is made from separate track slab segments 102S which are attached to one another in the longitudinal direction. The longitudinal dimension of the positioning blocks 120 and 130 does not have to be equal to the length of the track slab segments 102S, although it preferably is. Figures 6A to C diagrammatically show plan views of a track slab structure, in which the segments of the track slab 102, the rails 104 and the positioning blocks 120 and 130 can be recognized. In these figures, the distance between successive segments and positioning blocks is greatly exaggerated. In figure 6A is shown that the track slab segments 102S and the positioning blocks 120 and 130 may be aligned with one another in the longitudinal direction. However, at the transition between two adjacent segments 102S of the track slab 102 there is an insufficient force-transmitting connection between the successive segments, whereby axial forces in the successive segments, caused for example by braking forces, acceleration forces and/or temperature variations, will lead to an axial load of the rails 104. Preferably, therefore, the segments 102S and the outermost positioning blocks 120 and 120' are staggered in the longitudinal direction with respect to one another, so that a transition between two track slab segments 102S substantially corresponds to the centre of an outermost positioning block 120, while the transition between two successive positioning blocks 120 substantially corresponds to the centre of a track slab segment 102S, as is diagrammatically illustrated in figure 6B . Herein, the central positioning blocks 130 may be aligned with the outermost positioning blocks 120, 120', as diagrammatically illustrated in figure 6B, but even more preferably the central positioning blocks 130 are in turn also staggered with respect to the outermost positioning blocks 120 and are thus aligned with the track slab segments 102S, as illustrated in figure 6C. In figures 6A-C is also shown that the number of bolts 135 per central positioning block 130 does not have to be great and may, for example, be equal to two, and that the outermost positioning blocks do not have to be fixed by means of bolts, since they are held in place to a sufficient extent by the central positioning blocks 130. By making use of prefabricated elastic filler pieces, such as for example the said body 157 or a prefabricated filler piece (not shown) attached to the support rib 112 and/or the rail 104, it is possible, when positioning the rail 104, to use the inner wall 113 of the support rib 112 as a reference surface. By clamping the rail 104 against the inner wall 113 of the support rib 112, the rail 104 accurately obtains a predefined position, making operations during installation easier and quicker. Moreover, readjustment is not required. This technique can also be used on bends. On straight sections of track, it is advantageous to give the track slab segments 102S a relatively great length; a length in the order of 10 m is suitable. The positioning blocks 120 and 130 may have an equal length, but if desired the length of the positioning blocks 120 and 130 may be an integer factor smaller, in order to make them easier to handle; then, suitable lengths are, for example, 5 m or 2.5 m. If only straight track slab segments 102S are used, it is advantageous, on curved sections of track, to make the track slab segments 102S of relatively short length; a length in the order of 2 m is a suitable length. The end faces of the track slab segments 102S may be perpendicular to the longitudinal direction, in which case there will be a wedge-shaped gap between two adjacent track slab segments 102S, which gap has to be bridged by the rails 104. As an alternative, the end faces of the track slab segments 102S may be slightly inclined with respect to the longitudinal direction, in order to prevent such gaps from forming. In such straight track slab segments 102S, the rail- holding space 3 will also always have a straight shape, while the rail 104 will have a curved shape with a continuous radius of curvature. Then, the rail 104 will have a position, with respect to the rail-holding space 3, whose transverse coordinate varies along the length of a segment 102S. This can be accommodated most easily by giving a rail 104 its desired curved shape in situ in the successive rail-holding spaces 3 of the successive track slab segments 102S, and then fixing it in place by installing the positioning blocks 120, 130 and then pouring in said casting compound 151, as already described. However, with reference to figure 5 it is also possible to give the prefabricated body 157 a shape in such a way that therein the desired shape of the rail 104 is expressed: then, body 157 has a contour which varies over its length. Figures 7A-C illustrate an important advantage offered by the present invention. Figure 7A shows a railway bridge, generally indicated by the reference numeral 200. One end 202 of a bridge girder 201 of the railway bridge 200 rests on a first bridge head 204, while the other end 203 rests on a second bridge head 205. The two bridge heads 204 and 205 are securely anchored with respect to the fixed world by means of piles. The two bridge heads 204, 205 are adjoined by bodies of earth 206, 207 which, on their top surface, are provided with a reinforcement slab 208, 209. At its first end 202, the bridge girder 201 is fixed with respect to the first bridge head 204 (fixed bearing) , while support elements 210 such as roll bars are accommodated between the second end 203 of the bridge girder 201 and the second bridge head 205, in order to allow horizontal movement of the second end 203 of the bridge girder 201 with respect to the second bridge head 205, as illustrated more clearly in figures 7B and 7C. Track slab segments 102S of an embedded rail structure according to the present invention are placed onto the bridge girder 201 and the reinforcement slabs 208, 209. The track slab segments 102S are attached, by means of coupling members 20 according to the present invention, to the said reinforcement slabs 208, 209, to the said bridge heads 204, 205, and to the bridge girder 201. As indicated by a dashed line at 211, the second end 203 of the bridge 200 can exert a considerable movement in the horizontal direction with respect to the second bridge head 205 as a result, for example, of thermal expansion. In a conventional track system, the track slab segments would be fixedly attached to their support, and the track slab segments fixed on the bridge girder 201 would move with the bridge girder 201 with respect to the track slab segments fixed on the second bridge head 205 and the associated earth 207. This movement exerts considerable axial forces on the rails accommodated in these track slabs. By contrast, in a track system according to the present invention, the track slab segments and the rails accommodated therein act as a single unit which does not undergo any horizontal displacement with respect to the ground, since the coupling members 20 allow displacement of the bridge girder 201 with respect to the track slab 102 and the axial forces caused by displacement of this nature are not transmitted, or are scarcely transmitted, to the rails. Thus, the present invention offers a rail track system of the embedded rail type wherein rails 104 are fully enclosed in a track slab 102. The track slab is attached, by means of coupling members 20, to a support structure 12, which coupling members allow an axial displacement of the track slab with respect to this support structure . The track slab has lateral support ribs 112 which support the rails on their outer side. The attachment of the rails to the track slab is established by means of positioning blocks 120, 130 which are placed between the rails. The positioning blocks can clamp the rails securely against the support ribs, but alternatively the rails may also be cast into the space between the positioning blocks and the support ribs. In the preceding text, the present invention has been explained specifically for the situation relating to track slabs for rail -borne vehicles. In the following text, it will be explained, with reference to figures 8A-C, that the present invention can also be used in track slabs for magnetic trains. Figure 8A shows a diagrammatic plan view of part of a railway track intended for a magnetic train, and figures 8B-C respectively show a cross section and a longitudinal section thereof. This rail track likewise comprises track slabs 302 which, as shown in figure 8B, along their longitudinal sides support the members for guiding and driving a magnetic train, such as for example stator assemblies 370. In this situation too, it is desirable for the track slabs 302 and the guide and driving members attached thereto to act as a single unit, but conventionally the track slabs are rigidly attached to a support structure which forms part of the fixed world, which, in the examples shown in figures 8B-C, is illustrated as a hollow concrete rib 310. Since the stator assemblies 370 are normally situated on the underside of the track slabs 302, a central part of the track slabs 302, as seen in the transverse direction, is attached to the support structure 310, and they project sideways with respect to the latter. In this case too, it is possible, within the scope of the present inventive idea, to attach the track slabs 302 to the support structure 310 by means of the clamping members 20 discussed above. For this purpose, each track slab 302 has a continuous opening 371 which extends from the top surface 372 to the bottom surface 373 of the track slab 302. The opening 371 has side walls 374, 375 which may be vertically oriented, and which at their bottom edges are provided with a projection 331 directed towards the centre of the opening 371. The same statements apply to this projection as those made in the preceding text with reference to the projection 31. In the example shown, the projection 331 forms part of a metal profile 330 arranged along this bottom edge. Depending on the length of the track slabs 302 there may be a plurality of such openings 371. In the example illustrated, each track slab 302 has three substantially rectangular openings 371. One of these openings 371A is situated at the centre of the track slab 302 and is thus delimited by two longitudinal side walls 374 and two transverse side walls 375. The other two openings 371B are situated at the end walls 376 of the track slab 302 and open out in these walls, and are thus delimited by two longitudinal side walls 374 and a single transverse side wall 375. In the example illustrated, the two openings 371B are each half the size of the central opening 371A. In principle, the number of openings 371, their dimensions and positions, and the number of clamping members 20 and their positions can be selected freely within reasonable limits, wherein the presence of the openings 371 obviously must not have an adverse effect on the strength and integrity of the track slabs 302. The example shown is favourable in this respect. By way of example, the track slabs 302 are approximately 2.8 m wide and approximately 3.05 m long; the openings 371 have a transverse dimension of approximately 1.05 m and a longitudinal dimension of approximately 80 cm (371A) and approximately 37.7 cm (371B) . Furthermore, it is shown by way of favourable example that at each end opening 371B there is always an attachment member 20 arranged at each of the longitudinal side walls 374, so that the track slab 302, at its two ends, is locked in the transverse direction but has freedom of movement in the longitudinal direction, while at the central opening 371A there are always two clamping members 20 at each of the transverse side walls 375, arranged symmetrically with respect to the centre, so that the track slab 302, at its centre, is locked in the longitudinal direction but has freedom of movement in the transverse direction. Hereby, the advantage is achieved that any variation in length caused, for example, by longitudinal forces generated by braking/acceleration or caused by, for example, temperature variations is active from the centre. Incidentally, the length of the track slabs 302, with a transverse section which remains the same, may be selected to be greater or less than the example described, depending, inter alia, on a bend radius: on straight segments of track, it is generally possible to use longer slabs. It is advantageous to cover the openings 371 with a cover plate 377 after the clamping members 20 have been fitted. For this purpose, each side wall 374, 375 of the openings 371 is preferably, and as shown, provided on the top side with a recessed part whereby a bearing edge 378 for the cover plate 377 is defined. These cover plates 377 contribute to the fixation of two adjacent track slabs 302 with respect to one another and, moreover, provide a soundproofing effect. In this respect, for efficiency reasons it is preferable if all the cover plates can be identical. To this end, the dimensions of the slabs 302 and the distances between them can be selected in such a manner that the gap between two successive slabs 302 has a width that is at least substantially equal to the longitudinal dimension of the central opening 371A (= 80 cm) minus the sum of the longitudinal dimensions of the two end openings 371B (= 2 x 37.7 cm = 75.4 cm), thus in the example shown 4.6 cm. It will be clear to a person skilled in the art that the scope of the present invention is not restricted to the examples which have been discussed above, but rather various amendments and modifications to these examples are possible without departing from the scope of the invention as defined in the appended claims. For example, it is possible for the attachment method discussed with reference to figures 8A-C, in which a track slab is provided with openings in which the clamping members 20 are placed, to be applied to track slabs of the embedded rail system.

Claims: CLAIMS 1. Rail track structure (1), comprising a track slab (2; 102) , preferably made from concrete or the like with a substantially planar baseplate (110) and two support ribs (112) extending upwards with respect to a top surface (111) of the baseplate (111) ; two rails (104) positioned on the top surface (111) of the baseplate (110) , parallel to one another, which are each supported, by means of their outer surface, against an inner surface (113) of a respective support rib (112) ; and a number of positioning blocks (120, 130, 120'), positioned between the rails (104) on the top surface (111) of the baseplate (110) and preferably made from concrete or the like; the number of positioning blocks (120, 130, 120'), measured in the width direction of the track, being odd and at least equal to three. 2. Rail track structure according to claim 1, wherein there are three positioning blocks (120, 130' 120') in the width direction of the track. 3. Rail track structure according to claim 1 or 2 , wherein a central positioning block (130) , in cross section, is substantially in the shape of an inverted trapezium, and wherein the adjoining positioning blocks (120, 120') have an inner side wall (121) with an angle of inclination which substantially corresponds to those of the side walls (131) of the central positioning block (130) . 4. Rail track structure according to any one of the preceding claims, wherein only the central positioning block (130) is fixed to the baseplate (110) of the track slab by means of attachment members (135) . 5. Rail track structure according to any one of the preceding claims, wherein means are provided for creating a horizontal water-drainage gap (142) between the baseplate (110) of the track slab (102) and the bottom of the positioning blocks. 6. Rail track structure according to claim 5, wherein the said means are provided in the form of projections (137) which are formed integrally on or attached to the bottom of the positioning blocks. 7. Rail track structure according to any one of the preceding claims, wherein the positioning means are provided on their top surface with sound-absorbing elements (140) . 8. Rail track structure according to claim 7, wherein the sound-absorbing elements (140) are accommodated in recessed sections in the top surface of the positioning blocks. 9. Rail track structure according to any one of the preceding claims, wherein the top surface of the positioning blocks (120, 130, 120'), at least of an outermost section of the outermost positioning blocks (120, 120'), is situated at a higher level than the top surface of the rails (104) , the difference in height preferably amounting to approximately 36 mm; and wherein an outer edge of the top surface of the outermost positioning blocks (120, 120') is situated at a distance from the inner edge of the head (107) of the corresponding rail (104) , which distance preferably amounts to approximately 70 mm. 10. Rail track structure according to claim 9, wherein an outer edge section of the outermost positioning block (120, 120') is reinforced by a profiled metal plate (125) attached to the positioning blocks. 11. Rail track structure according to any one of the preceding claims, wherein an elastic material (151) is arranged between the outer surface of an outermost positioning block (120) and the inner surface of a rail (104) . 12. Rail track structure according to any one of the preceding claims, wherein an elastic material (151) is arranged between the outer surface of a rail (104) and the inner surface (113) of a respective support rib (112) . 13. Rail track structure according to any one of the preceding claims, wherein the track slab (102) is composed of a plurality of successive track slab segments (102S) of a predetermined length, and wherein the positioning blocks (120, 130, 120') have a length which is equal to the said predetermined length of the track slab segments (102S) multiplied or divided by an integer which is preferably equal to 1; and wherein the rail track segments (102S) are staggered in the longitudinal direction with respect to the outermost positioning blocks (120, 120'), so that a transition between two successive track slab segments (102S) substantially corresponds to the centre of an outermost positioning block (120) while the transition between two successive positioning blocks (120) substantially corresponds to the centre of a track slab segment (102S) . 14. Rail track structure according to claim 13, wherein the central positioning blocks (130) are aligned with the track slab segments (102S) . 15. Rail track structure according to any one of the preceding claims, wherein a foot (105) of the rail (104) is positioned in a channel profile (152) with a substantially U-shaped cross section preferably made from plastic. 16. Rail track structure according to claim 15, wherein a resilient mass (154) is arranged on the bottom (153) of the said profile (152), beneath the foot (105) of the rail (104). 17. Rail track structure according to claim 15 or 16, wherein an outermost upright wall (155) of the channel profile (152) , in the horizontal direction, forms a stop for the foot (105) of the rail (104) , and wherein an innermost upright wall (156) of the channel profile (152) functions as a bearing rim for an outermost positioning block (120) . 18. Rail track structure, preferably according to any one of the preceding claims, comprising a track slab (2; 102; 302) provided with train-guiding means and being attached to a support structure (10; 310) by means of clamping members (20) which allow the track slab (2; 102; 302) a freedom of displacement in the plane of the track slab with respect to the support structure (10; 310) . 19. Rail track structure according to claim 18, wherein the track slab (2; 102; 302) is provided on its bottom side with a foot (30; 330), and wherein the clamping members (20) engage on the said foot (30; 330) with a clamping force which is substantially vertically directed. 20. Rail track structure according to claim 18 or 19, wherein the clamping members (20) comprise an elevated rib (25) which serves as a stop for the track slab (2; 102; 302). 21. Rail track structure according to one of claims 18-20, wherein the clamping members (20) comprise: a bearing shell (21) with a bearing surface (29) on which the track slab (2; 102; 302) rests; an elastic sheet (22) beneath the bearing shell (21); and preferably a rigid baseplate (23) beneath the elastic sheet (22) . 22. Rail track structure according to claim 21, further comprising a bolt (24) for rigidly attaching the clamping members (20) to the support structure (10; 310) . 23. Rail track structure according to claim 22, wherein the bolt (24) is accommodated in an eccentrically positioned bore of a cylindrical adjustment sleeve. 24. Rail track structure according to any one of claims 18-23, wherein the clamping members (20) are arranged along an outer edge of the track slab (2; 102). 25. Rail track structure according to any one of claims 18-23, wherein the track slab (2; 102; 302) is provided, at a central section as seen in the width direction, with an opening (371) which extends from a top surface (372) to a bottom surface (373) of the track slab, and wherein clamping members (20) are situated in said opening. 26. Rail track structure according to claim 25, wherein the clamping members (20) are situated at a longitudinal wall (374) of an opening (371B) . 27. Rail track structure according to claim 25, wherein the clamping members (20) are situated at a transverse wall (375) of an opening (371A) . 28. Rail track structure according to any one of claims 25-27, wherein the track slab is provided with a central opening (371A) at the centre of its body, and with end openings (371B) at its ends; wherein clamping members (20) are arranged at a longitudinal wall (374) of the end openings (371B) , and wherein clamping members (20) are arranged at a transverse wall (375) of the central opening (371A) . 29. Rail track structure according to any one of claims 25-28, wherein the said openings (371) are covered by means of cover plates (377) which are preferably identical to one another. 30. Rail track structure according to claim 29, wherein a cover plate (377) , which covers two end openings (371B) , which adjoin one another, of two successive track slabs, makes a constructional contribution to aligning the said two successive track slabs with respect to one another. 31. Rail track structure, preferably according to any one of the preceding claims, comprising a track slab (2; 102; 302) provided with train-guiding means and being attached to a support structure (10; 310), vibration-damping means (22) being accommodated between the track slab (2; 102; 302) and the support structure (10; 310) . 32. Track slab (102) which is suitable and intended for use in a rail track structure according to claim 1, preferably made from concrete or the like, comprising a substantially planar baseplate (110) and two support ribs (112) extending upwards with respect to a top surface (111) of the baseplate (110) and being substantially parallel to one another, of which an inner surface (113) is suitable for supporting the outer surface of a rail (104) . 33. Track slab according to claim 32, wherein said planar baseplate (110) and said support ribs (112) are produced as an integral moulding. 34. Track slab (302) which is suitable and intended for use in a rail track structure according to claim 1, preferably made from concrete or the like, which at a central section, as seen in the width direction, is provided with an opening (371) which extends from a top surface (372) to a bottom surface (373) of the track slab, and at the bottom of a side wall (374, 375) of this opening is provided with a foot (30) for a clamping member (20) to engage on.

Inventors: GRIMBERGEN FREDERIKUS ADOLF JO, GRIMBERGEN, FREDERIKUS, ADOLF, JOSEPH
Applicants: GRIMBERGEN FREDERIKUS ADOLF JO, GRIMBERGEN HOLDING B V, GRIMBERGEN HOLDING B.V., GRIMBERGEN, FREDERIKUS, ADOLF, JOSEPH
Application year: 2000
Main classification: E01B2
IPC codes: E01B1, E01B2, E01B3, E01B19, E01B25