Technical Field
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The invention relates to a solution of a cover of a railway or tram track that addresses problems associated with providing load bearing capacity, noise and vibration damping, while also stabilizing the cover, and, further, with assembling individual layers during implementation of installation of the cover on the track.
Background of the Invention
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A cover of a tram or railway track is a protective layer or structure positioned above the track intended to protect the track and the surrounding infrastructure from external influences such as dirt and weather conditions. Especially in cities, the cover also provides a suitable surface and safety for pedestrians or vehicle crossing, noise reduction, and maintaining cleanliness and integrity of the track, wherein it allows easy access to the track for maintenance and inspection purposes.
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In the current state of the art, a number of covers of a railway or tram track are known, which are adapted to a particular application and use of the surface of the cover. For example, the document
RU141701 U1 describes a structure of a tram track with a noise protection cover between rails, wherein the cover is placed on sleepers and comprises a sound insulation layer made of extruded polystyrene, a geotextile, a gravel layer, and a surface layer comprising a plastic grid filled with soil and planted with grass. A disadvantage of this solution is the low load-bearing capacity of the cover, which is not walkable and does not allow, e.g., the movement of machines between the rails. Another disadvantage is the complicated execution of repairs, e.g., replacement of rails, as the load-bearing gravel layer is not defined or bound in any way.
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Another solution is described in the document
US4804293 , which describes a structure of a set of layers for modification and reinforcement of the subgrade, e.g., for a railway track, wherein this set of layers comprises a geotextile mat with a water-impermeable film and, further, a spatial geotextile mesh filled with gravel, wherein the surface of the structure is grassed. However, this document is primarily focused on issues associated with drainage, wherein it does not address the issue of increasing the load-bearing capacity and noise and vibration damping of the track at all.
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The document
EP3408448 discloses a railway or tram cover that comprises concrete elements inserted between tracks or on the sides of the tracks, wherein the concrete elements comprise a water permeable noise protection insert. A disadvantage of this solution is the necessity of handling bulky and heavy elements, wherein concrete elements are also unsuitable for subsequent installation of soil and natural vegetation. The concrete elements also cannot be easily repaired and recycled.
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A disadvantage of the above solutions is that they address the issues of the load-bearing capacity, drainage, and soundproofing of the tram or railway track only individually and not comprehensively, wherein each of these cover solutions is designed individually and specifically for the given purpose. These solutions therefore do not allow universal use for cases where all of the above functions of the cover need to be provided. Another disadvantage of the existing cover solutions is the handling complexity and time required for the installation thereof, wherein the individual elements of the cover cannot be easily disassembled, repaired, or replaced, and recycled.
Summary of the Invention
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The above shortcomings are to a certain extent eliminated by a cover of a railway or tram track adapted to be placed between rails and/or on the sides of rails of the railway or tram track, wherein the cover comprises a drainage layer, a load-bearing layer adjoining the drainage layer, and a surface layer placed above the load-bearing layer. The load-bearing layer comprises at least one plastic grid with a honeycomb structure, and a filler at least partially filling the honeycomb structure of the at least one plastic grid. The at least one plastic grid adjoins the drainage layer and is firmly connected to the adjoining drainage layer by ultrasonic welding.
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Said arrangement of the cover between the rails or on the sides of the rails fulfills a number of functions, in particular the load-bearing function, then the function of drainage or water retention of the cover, and also the function of damping the noise and vibrations arising from the operation of the tram track. The cover of the track is placed, e.g., directly on the structure of the railway superstructure or on the subbase or leveling layer. The cover comprises a drainage layer, wherein the drainage layer means a permeable filter layer that facilitates drainage of water and protects the cover and in particular the load-bearing layer of the cover from clogging with dirt, e.g. clay, particularly from the space below the drainage layer (e.g., in a direction from the bedrock and subbase or leveling layer). The drainage layer may be, e.g., a mat, non-woven geotextile, or another similar permeable material made of synthetic fibers, the drainage layer is preferably made of a material that is suitable for ultrasonic welding. At least one plastic grid is firmly connected to the drainage layer by ultrasonic welding.
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Preferably, the drainage layer is positioned underneath the plastic grid or plastic grids, where it forms a sort of a bottom of the set of layers of the plastic grids, and even more preferably, the drainage layer is connected by ultrasonic welding to the plastic grid placed on the drainage layer. The cover of the track may also comprise multiple drainage layers, e.g., one drainage layer positioned below the plastic grids filled with the filler and another drainage layer placed above these plastic grids. Thus, the first drainage layer prevents the filler from the plastic grids from sinking into the leveling or subbase layer and clogging the filler in the plastic grids above the drainage layer, and the second drainage layer can prevent clogging the filler in the plastic grids below the drainage layer, especially if the cover comprises the upper surface layer as a living cover with soil and vegetation.
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The cover may further comprise a retention film that is preferably positioned below the drainage layer and below the load-bearing layer, e.g., directly on the subbase/leveling layer.
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The load-bearing layer comprises at least one plastic grid, therefore, there may be multiple plastic grids, wherein they may be placed in layers above each other. The load-bearing layer preferably comprises a total of at least two plastic grids, wherein the plastic grids are placed in layers above each other. Therefore, the plastic grids may be placed above each other or directly on top of each other, wherein adjacent plastic grids may adjoin each other. Thus, each plastic grid may adjoin at least one adjacent element (the drainage layer and/or an adjacent plastic grid), wherein the plastic grid may be firmly connected to that at least one element by ultrasonic welding. Thus, at least one plastic grid may be connected by ultrasonic welding to the drainage layer and/or another plastic grid.
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The connection of the plastic grid to an adjacent plastic grid and/or to the drainage layer may be direct, i.e., as ultrasonic welding directly connecting these elements. The connection of the plastic grid to an adjacent plastic grid and/or the drainage layer may be indirect, i.e., for example, the plastic grid and the adjacent plastic grid and/or the drainage layer are connected to each other by an additional auxiliary element. In other words, one plastic grid may be connected to the auxiliary element and the other plastic grid may also be connected to this auxiliary element, wherein both of these connections may be provided by ultrasonic welding. Direct and indirect connections can be combined such that the plastic grid can be connected directly to the drainage layer on one side thereof and indirectly to the adjacent plastic grid on the other side by means of the auxiliary element. Only every two adjacent elements, e.g., adjacent plastic grids, can be connected by the auxiliary element with ultrasonic welding. If there are multiple plastic grids above each other, all plastic grids in this set of layers may preferably be interconnected using one auxiliary element, e.g., by passing through the plastic grids and simultaneously by ultrasonic welding to each of these plastic grids. If the auxiliary element connecting this set of layers also adjoins the drainage layer, it can also be connected thereto. Thus, the plastic grid may also be indirectly connected by the auxiliary element to another (non-adjacent) plastic grid, even though these plastic grids are not in direct contact and do not adjoin each other.
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If the load-bearing layer comprises, e.g., exactly two plastic grids, both of these plastic grids may, e.g., be connected to the drainage layer such that the drainage layer is sandwiched between the two plastic grids, wherein each of the two plastic grids adjoins the drainage layer. Thus, one (first) plastic grid is connected by ultrasonic welding to the drainage layer on one side of the drainage layer, and the second plastic grid is connected by ultrasonic welding to the drainage layer on the other (opposite) side of the drainage layer than the first plastic grid. Alternatively, only one of these two plastic grids can be firmly connected to the drainage layer. The plastic grid under the drainage layer, i.e., the plastic grid placed on the subbase or leveling layer, may comprise water retention elements, e.g., retention cups, instead of the filler.
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At least two plastic grids may preferably be positioned in layers on top of each other and above the drainage layer. Even more preferably, these at least two plastic grids are connected to the drainage layer such that the first plastic grid is connected to the drainage layer by ultrasonic welding, wherein the second plastic grid is connected to the first plastic grid by ultrasonic welding. The drainage layer and the adjoining plastic grid and/or the adjacent plastic grids, i.e., plastic grids adjacent to each other, are thus preferably in contact with each other. The stacking of the plastic grids on each other is preferable especially for tram covers that require a greater thickness of the load-bearing layer, wherein the height of the load-bearing layer may be individually adjusted for the given cover of the track. The required height of the load-bearing layer, i.e., the set of layers of the plastic grids with the drainage layer or drainage layers, can be adapted to the type and height of the rail. For example, if the thickness of the plastic grid is 40 mm, the thickness of the load-bearing layer above the drainage layer may be, e.g., 40 to 300 mm. The plastic grids provide stiffness to the load-bearing layer, but are simultaneously lightweight and easy to handle. Working with plastic grids of a smaller thickness provides more variability in stacking layers on each other to achieve the desired thickness of the set of layers.
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Preferably, at least one plastic grid is firmly connected to the adjoining adjacent plastic grid by ultrasonic welding. The plastic grids may therefore also be connected by ultrasonic welding to each other. In other words, the drainage layer and the adjacent plastic grid placed on the drainage layer, and/or the two adjacent and adjoining plastic grids, are connected by ultrasonic welding. An advantage of ultrasonic welding is a firm connection of elements while maintaining the original properties of the materials being connected. Ultrasonic welding does not cause chemical modification of the materials being connected as in the case of chemical connection using adhesives, nor does it cause degradation of the material due to heating during thermal connection of materials. For ultrasonic welding, partially crystalline polymers (e.g., PP, PET, PE, PA), amorphous polymers (e.g., PC, PS, ABS, and butadiene styrenes), or combinations thereof are most suitable. Thus, the materials of the drainage layer and the plastic grid can be the same, but they can also be different, as long as both materials are suitable and mutually compatible for connection by ultrasonic welding.
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The honeycomb structure of the plastic grid means a structure with a number of cells separated by thin walls, which is similar to a honeycomb. The individual eyes or cells of the honeycomb may have a regular or irregular shape, e.g., they may be in the shape of a hexagon or other polygon. The honeycomb structure can be hollow and not comprise a bottom, therefore, if multiple plastic grids are placed on top of each other and there is no drainage layer sandwiched between them, then all the layers of the plastic grids above the drainage layer can be filled with the filler in one step, thereby interconnecting and stabilizing these layers. The honeycomb structure may be closed on one side, i.e., comprise a solid bottom and be used for water retention for the cover, which is preferable for a plastic grid positioned below the drainage layer. The retention function of the cover can thus be provided by a closed honeycomb structure of the plastic grid instead of the retention film. The load-bearing layer may be water permeable and provide drainage of the cover, wherein the water permeability may be provided, e.g., by the water permeability of the plastic grids and/or the properties of the filler placed in the plastic grids. The load-bearing layer may be water retentive, wherein the water retention may be provided, e.g., by a special absorbent filler.
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The honeycomb structures of the plastic grids may be aligned with each other. In other words, the cells of the honeycomb structures of the plastic grids may form a continuous cavity along the height of the load-bearing layer and the walls of the cells of the individual plastic grids may together form continuous walls along the height of the load-bearing layer. The honeycomb structures of the plastic grids can be aligned with each other only for a selected pair or pairs of adjacent plastic grids, for a selected group of plastic grids (e.g., for three plastic grids placed on top of each other), or for all the plastic grids. Thus, every two adjacent plastic grids with an aligned honeycomb structure may be connected by ultrasonic welding along the entire length of the edges of the walls of the honeycomb structure, wherein the edges surrounding the cells of the honeycomb structure of the first plastic grid are in contact with the corresponding edges surrounding the cells of the honeycomb structure of the second plastic grid. An advantage of the aligned honeycomb structures is the ease of filling the load-bearing layer with filler even with a higher number of plastic grids placed on top of each other.
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The honeycomb structures of, e.g., adjacent and adjoining plastic grids may be offset, e.g., by half of the maximum dimension of a cell of the honeycomb structure. The offset of the honeycomb structures may be preferable, e.g., to increase the load-bearing capacity of the load-bearing layer but may complicate the connection of the plastic grids by ultrasonic welding, as the connection of adjacent plastic grids with the offset honeycomb structure may only be point-based, i.e., at the intersection of the edges of the walls surrounding the cells of the honeycomb structure. The offset of the honeycomb structures may also complicate filling of the plastic grids with the filler. The filling with the filler is more difficult especially in the case of small cells of the honeycomb structure or filler with large grains, high viscosity, etc.
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The offset and aligned honeycomb structures may be combined in the load-bearing layer in any arrangement. The load-bearing layer may comprise, e.g., one plastic grid below the drainage layer and four plastic grids above the drainage layer, wherein the honeycomb structures of all the plastic grids may be aligned with each other. Alternatively, the honeycomb structures of only the plastic grids above the drainage layer may be aligned with each other, wherein the honeycomb structure of the plastic grid below the drainage layer is offset relative to the honeycomb structure of the four plastic grids above the drainage layer. Alternatively, all adjacent, i.e., adjoining honeycomb structures of this set of layers of the plastic grids may be offset relative to each other, i.e., the first honeycomb structure (of the first plastic grid, below the drainage layer) is aligned with the honeycomb structure of the third and, further, the fifth (uppermost) plastic grid, wherein the honeycomb structure of the second plastic grid is aligned with the honeycomb structure of the fourth plastic grid. Further, relative to the first and fifth honeycomb structure, the honeycomb structures between them, i.e., the honeycomb structures of the second, third, and fourth plastic grid, may be offset. The number of the plastic grids and the mutual offset or alignment of the individual honeycomb structures of the plastic grids is optional, wherein each honeycomb structure may be aligned and/or offset relative to at least one honeycomb structure. The load-bearing layer may comprise stabilizing elements that pass through the cells of the honeycomb structures of the plastic grids, wherein these honeycomb structures may be aligned or offset. The stabilizing elements may also serve as auxiliary elements for indirect connection of the plastic grids and/or drainage layers.
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The filler of the load-bearing layer may be, e.g., an unbound loose material, e.g., an aggregate of optional fraction such as sand, gravel, crushed stone, etc. The filler may be natural or artificial. An artificial filler may be, e.g., brick or concrete rubble, expanded artificial aggregate, expanded synthetic recyclate, fibrous synthetic recyclate, etc., the filler of the synthetic recyclate may be based on, e.g., glass, polymers, or composite materials. The filler may be bound, e.g., in the form of aggregate bound with cement or polymer or pervious concrete. The filler may also be wood chips or other lightweight material, but a disadvantage thereof is the lower load-bearing capacity of the layer filled in this manner. The plastic grids may only be partially filled with the filler. The plastic grids may be completely filled with the filler. The individual plastic grids or groups of plastic grids may also be filled with multiple different types of filler. The load-bearing layer may thus comprise, e.g., four plastic grids placed on top of each other, wherein the three bottom plastic grids may be filled with aggregate and the last upper plastic grid below the surface layer may be filled with lightweight material. Preferably, the filler filling the plastic grids is water permeable, e.g., pervious, to ensure drainage of water from the cover. Preferably, the filler of the load-bearing layer is water retentive, e.g., absorbent, to ensure stable moisture of the cover. The filler is preferably adapted for damping of noise and vibrations arising from the operation of the tram or railway track. Both the bound and unbound filler in the plastic grids may be compacted by commonly available means.
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The surface layer of the cover may be generally composed of, e.g., asphalt, stone or mosaic paving, cover panels, gravel, grassy area, rubber materials, etc., wherein the surface layer is selected according to the intended use of the surface of the track between the rails.
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The firm connection between the drainage layer and the adjoining plastic grid or plastic grids of the load-bearing layer ensures that no filler penetrates between the drainage layer and/or plastic grids, which could cause unevenness or deformations of the load-bearing layer of the cover. The solution further provides a high strength and stability of the drainage layer and the load-bearing layer, wherein the surface layer of the cover may also be driven on and allow the movement of heavy vehicles including vehicles of the integrated rescue system (IRS). The drainage layer together with the load-bearing layer (excluding the filler) may form a single solid piece thanks to ultrasonic welding, wherein this solid piece may be removed from the site, repaired, replaced, or recycled if necessary. If the filler is, e.g., loose unbound material, then the disassembly of the load-bearing layer and possible recycling of the plastic grids with the drainage layer is even easier.
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Preferably, each plastic grid is firmly connected to the adjoining adjacent plastic grid and/or the adjoining drainage layer by ultrasonic welding. Therefore, each plastic grid is firmly connected to all adjoining elements, i.e., to one element adjoining the plastic grid from the first side (upper or lower), or both elements adjoining the plastic grid, where one element is adjoining from the first side and the other element is adjoining from the second side. Even more preferably, the drainage layer is also firmly connected by ultrasonic welding to the adjoining element or elements. For example, if the first plastic grid is positioned between the drainage layer and the second plastic grid, then the first plastic grid is connected to the drainage layer by ultrasonic welding on the one side thereof and is connected to the second plastic grid by ultrasonic welding on the other (opposite) side thereof. The first and second sides of the grid mean the opposite upper and lower sides of the grid. If the load-bearing layer comprises multiple plastic grids, each plastic grid is preferably firmly connected to all adjacent plastic grids, or alternatively to the drainage layer. The firm connection of all the plastic grids to the drainage layer increases the cohesion of the set of layers and prevents the layers from being displaced in the horizontal and vertical direction. Preferably, all plastic grids and all drainage layers that the cover comprises may be interconnected by ultrasonic welding. Preferably, all plastic grids and all drainage layers that the cover comprises may be interconnected by ultrasonic welding, with the exception of a plastic grid sandwiched between two drainage layers. This plastic grid is preferably left open on one side and not connected to one of the adjacent elements, e.g., for easy filling with filler or, conversely, for emptying the filler.
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Preferably, at least one plastic grid is connected to the adjoining adjacent plastic grid and/or the adjoining drainage layer by a surface connection. The surface connection of the drainage layer and the plastic grid placed on the drainage layer, and/or the plastic grids between each other, provides higher connection strength of the two elements compared to point-based connections and better prevents possible displacements of the individual layers in the horizontal and vertical direction.
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The plastic grid and the adjoining adjacent plastic grid and/or the adjoining drainage layer are preferably made of the same material. The advantage of unifying the materials of the elements being connected is an easier implementation of the ultrasonic weld. Another advantage is that if the whole assembly of the elements being connected is made of the same and recyclable material, and simultaneously the load-bearing layer is filled with unbound material, the whole assembly may be recycled without problems. Even more preferably, all drainage layers and all plastic grids of the cover are made of the same material. The drainage layers and the plastic grids may be made of, e.g., PP, which is easy to recycle and has a high chemical resistance. If the drainage layers and plastic grids are made of the same material, it is easy to connect all these elements to each other and then recycle the entire drainage layer and plastic grids of the load-bearing layer.
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Preferably, a total of at least two plastic grids adjoin each other, wherein the honeycomb structures of at least two plastic grids are aligned with each other. In other words, the cells and the walls of the honeycomb structure of two plastic grids placed above each other or on top of each other are aligned with each other, wherein the honeycomb structures of both adjoining grids are connected by ultrasonic welding (point-based or surface-based). When stacking the plastic grids on each other and aligning their honeycomb structures, one or multiple stabilizing elements may pass through the aligned cells. The stabilizing elements may also perform a retention function, wherein the stabilizing elements may be adapted to retain water. The stabilizing elements may be, e.g., hollow and comprise a solid bottom for water retention.
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Preferably, the load-bearing layer further comprises at least one stabilizing element, where each stabilizing element passes through mutually aligned cells of the honeycomb structures of at least two plastic grids. Even more preferably, there are at least two stabilizing elements to stabilize the plastic grids in at least two places. The stabilizing elements preferably pass through, e.g., the edge cells, i.e., the cells on the perimeter of the plastic grids at the sides or in the corners of the plastic grids. The stabilizing elements may be distributed in the plastic grids in a regular grid. The stabilizing elements may only freely pass through the plastic grids, or they may be firmly or removably connected to at least one plastic grid and/or to the drainage layer. The stabilizing elements may preferably be made of the same material as the plastic grids and/or the drainage layer. The stabilizing elements may also be made of another material. The stabilizing element may take, e.g., the form of a hollow tube inserted into the cells of the plastic grids, a durable rod inserted into the cells of the plastic grids and attached to the walls of the honeycomb structures of the grids, a tube with a solid bottom for simultaneous water retention, etc. The stabilizing element may also take the form of concrete or other similar filling of the cells of the honeycomb structure, wherein this filling firmly stabilizes the mutual position of the plastic grids. Preferably, the stabilizing element is also the auxiliary element, wherein the plastic grids and/or the drainage layers are indirectly interconnected by the auxiliary element. Even more preferably, the plastic grids and/or drainage layer are connected to the stabilizing element by an ultrasonic weld or multiple ultrasonic welds.
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The filler of the load-bearing layer preferably comprises unbound loose dense or lightweight material. An advantage of the unbound and loose dense filler (e.g., natural or artificial aggregate of fraction 4/8 or 8/16 mm, synthetic recyclate, etc.) can be a high load-bearing capacity, water drainage capability, and ease of installation. Unbound and loose lightweight filler (e.g., natural or artificial expanded or fibrous filler, wood material, etc.) may have a lower load-bearing capacity, but its advantage may be better water retention, noise damping, etc. A loose filler generally also saves the costs on the binding component such as cement mortar or polymer resin and the installation of the filler is easier, as it is not limited by the setting time of the binding component.
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The surface layer preferably comprises live vegetation or a synthetic finish, wherein the synthetic finish comprises rubber and/or artificial grass. The cover of the railway track is preferably designed for a track with natural live vegetation or with a surface imitating natural live vegetation, for which the load-bearing layer described above will provide sufficient load-bearing capacity. Even more preferably, the surface layer with the live vegetation comprises a substrate of natural fibers (e.g., coconut fiber). An advantage of a substrate made of natural or artificial fibers is that this substrate is durable, essentially maintenance-free and does not clog the filler of the load-bearing layer like soil, as it is also more resistant to wash-off by rain.
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The essence of the method of manufacture of the cover of a railway or tram track according to this invention lies in the fact that it comprises the steps of:
- placing the drainage layer between the rails and/or on the sides of the rails,
- placing at least one plastic grid with a honeycomb structure between the rails and/or on the sides of the rails,
- firmly connecting the plastic grid to the adjoining drainage layer by ultrasonic welding,
- filling at least one plastic grid with a filler, and
- installing the surface layer,
wherein the step of firmly connecting and the steps of placing are mutually time-independent.
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The advantage of the above procedure is that the step of placing the drainage layer, the step of placing the plastic grid or plastic grids, and the step of firmly connecting the adjoining elements can be performed in any order depending on the chosen composition of the cover, i.e., depending on the chosen number and arrangement of the plastic grids and their intended connection to the drainage layer or to the plastic grids. The plastic grids and the filler form the load-bearing layer, which may preferably be firmly connected also to the drainage layer. The manufacture of the cover also means its installation at a selected location of the tram or railway track. The above steps are preceded by a conventional modification of the subbase, e.g., installing a subbase/leveling layer (between the rails or on the sides of the rails) and, if necessary, the installation of noise and vibration absorbers.
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The plastic grids may be placed above each other, i.e., for example directly on each other such that the adjacent plastic grids adjoin each other, or they may be placed on top of each other such that another element is inserted or sandwiched between them, e.g., a drainage layer. Ultrasonic welding may be performed in advance, wherein only placing a weldment between the rails or on the sides of the rails is performed at the cover installation location, followed by filling with the filler. The advantage of welding in advance is that it can be performed in the internal space of a building, where suitable conditions for welding (e.g., ambient temperature, etc.) can be more easily provided, and simultaneously, there is no need to transport the device to perform the welds and transport the device to the installation location.
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The ultrasonic welding of all layers may be performed entirely at the installation location, if allowed by the surrounding conditions. The ultrasonic welding may be performed partially in advance and partially at the installation location, i.e., only some selected elements may be welded in advance. If the cover comprises, e.g., one drainage layer and four plastic grids to be placed above the drainage layer, only the plastic grids can be welded in advance outside the installation location, wherein the drainage layer is then placed at the installation location and a weldment of four plastic grids is placed in-situ on this drainage layer and welded thereto, which is then filled with the filler. The order of welding and placing of the individual layers is suitably selected such that the required plastic grids may be filled with the filler.
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The step of filling the at least one plastic grid with the filler preferably follows after the steps of placing the drainage layer, placing the plastic grids, and firmly connecting the adjoining elements. Filling the load-bearing layer with the filler after placing and firmly connecting the drainage layer and the plastic grids is advantageous for handling during the installation, since the drainage layers, the plastic grids, and the filler may be transported to the site separately, wherein the filler is placed directly into the plastic grids already placed between the rails or on the sides of the rails. A loose unbound filler, which can be emptied out of the plastic grids when replacing the load-bearing layer, allowing the plastic grids or the drainage layer to be repaired or replaced, is particularly advantageous. The advantage is that the filler itself may also be replaced in this case, e.g., with a denser and stronger filler, if the requirements for the load-bearing capacity of the cover change during the life. Optionally, the filling of the plastic grid or grids may be performed before the installation. Especially in the case of filling with bound filler, this filling may be performed in advance, but the disadvantage is the greater weight of the entire load-bearing layer during transport and subsequent installation of the cover.
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Preferably, the manufacture and installation of the cover is carried out by ultrasonically welding the drainage layer and the plastic grids outside the installation location in advance. A weldment of the drainage layer and the plastic grids is installed on the track with the prepared subbase and possibly installed absorbers, wherein this weldment is subsequently filled with the filler. Finally, the surface layer is installed.
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Preferably, the step of placing the at least one plastic grid with the honeycomb structure comprises placing a total of at least two plastic grids on each other, wherein the honeycomb structures of the plastic grids adjoin each other. Layering the plastic grids with the honeycomb structure in layers directly on each other is preferable in order to adjust the height of the load-bearing layer for different types of covers and different heights of rails. Even more preferably, the honeycomb structures of the adjoining plastic grids are aligned with each other. Even more preferably, the honeycomb structures of the adjoining plastic grids are connected to each other by ultrasonic welding.
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Preferably, the step of placing the plastic grids with the honeycomb structure in layers on each other is followed by the step of inserting at least one stabilizing element, where each stabilizing element passes through the cells of the honeycomb structures of at least two plastic grids. The honeycomb structures of the two plastic grids may be mutually aligned or offset, both of these options allowing the stabilizing element to be passed through both plastic grids. After stacking the plastic grids on each other, e.g., one or even multiple stabilizing elements may pass through the cells of the honeycomb structures. The implementation and function of the stabilizing elements are described above, wherein the stabilizing elements may be installed in advance during the manufacture of the cover, e.g., in an already prepared weldment of the plastic grids with the drainage layer, wherein this weldment and the stabilizing elements are subsequently transported to the cover installation location. The stabilizing elements may be installed on site, e.g., before the plastic grids are filled with the filler. The stabilizing elements may be firmly connected to the plastic grids, the drainage layer, etc., preferably also by ultrasonic welding.
Description of Drawings
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A summary of the invention is further clarified using exemplary embodiments thereof, which are described with reference to the accompanying drawings, in which:
Fig. 1 represents the composition of the cover of a tram track according to the first exemplary embodiment.
Exemplary Embodiments of the Invention
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The invention will be further clarified using exemplary embodiments with reference to the respective drawings. One exemplary embodiment is a composition of a tram cover that comprises a total of five plastic grids 5 and a surface layer 4 with live vegetation in the form of stonecrops, as shown in Fig. 1.
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In this embodiment, the cover is positioned between the rails 1 of the tram track, wherein the rails 1 are placed on the body of the railway superstructure 6, i.e., on the track bed, and attached by means of fastening elements 8. Each rail 1 is adjoined by an external absorber 10 oriented towards the outside of the tram track and, further, an internal absorber 11 oriented towards the inside of the tram track (between the rails 1), wherein the absorbers are made of a recycled material based on rubber, plastic, or textile. The internal and external absorbers 10, 11 serve to attenuate noise and differ only in their shape. The internal absorbers 11 are thus located between the two rails 1 of the tram track, where a leveling subbase layer 7 is further placed, which is formed by a gravel layer. A set of layers of the drainage layer 2 and the load-bearing layer 3 of the cover is placed on the leveling layer 7.
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The cover comprises a retention film 9, the drainage layer 2, the load-bearing layer 3, and the surface layer 4. The drainage layer 2 and the load-bearing layer 3 are positioned above the retention film 9, wherein the load-bearing layer 3 comprises a total of five plastic grids 5, where one of the plastic grids 5 is positioned below the drainage layer 2 and four plastic grids 5 are positioned above the drainage layer 2. The surface layer 4 comprises live vegetation comprising stonecrops.
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The retention film 9 is placed directly on the leveling subbase layer 7. The first bottommost plastic grid 5 is placed on the retention film 9, wherein this grid 5 is filled with water retention elements in the form of retention cups. To this first plastic grid 5, the drainage layer 2 is connected by ultrasonic welding. The drainage layer 2 comprises a non-woven permeable geotextile of synthetic polypropylene (PP) fibers, wherein a set of layers of four plastic grids 5 with the honeycomb structure filled with loose aggregate is placed on the geotextile. In addition to the drainage function, the geotextile also has a separation function, i.e., it separates the material of the subbase leveling layer 7 from the filler filling the load-bearing layer 3 and thus prevents their mixing. The bottommost of these four plastic grids 5 is firmly connected to the drainage layer 2 by ultrasonic welding.
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Each plastic grid 5 has the shape of a rectangle with a thickness (height) of 32 mm and is made of durable polypropylene, where the thickness of the walls of the honeycomb structure is approximately 0.8 to 1.4 mm. The honeycomb structure comprises conventional cells in the shape of a hexagon, wherein the largest diameter of the cell is 42 mm, wherein each separate plastic grid 5 is manufactured by injection molding the material into a mold. The honeycomb structure of each plastic grid 5 is aligned relative to the honeycomb structure of each adjacent plastic grid 5 that adjoins it, wherein the edges of adjacent plastic grids 5 are welded by ultrasonic welding. The alignment of the individual honeycomb structures of the plastic grids 5 can be seen in Fig. 1. All four plastic grids 5 above the drainage layer 2 are thus connected to each other and also to the drainage layer 2 by ultrasonic welds, wherein all these elements are made of the same material and connected in a point-based manner. The ultrasonic welds are thus implemented only at selected locations and not over the entire contact surface of the elements. All four plastic grids 5 above the drainage layer 2 are interconnected by ultrasonic welds indirectly by means of stabilizing elements, which are described below.
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The load-bearing layer 3 further comprises a total of twelve stabilizing elements (not shown in the figure), wherein the stabilizing elements are inserted into the cells of the honeycomb structures at the corners, side edges and the center of the plastic grids 5. The stabilizing elements are arranged in a regular grid of 4 × 3 such that on each longer side of a plastic grid 5, four stabilizing elements are regularly positioned, on each shorter side of a plastic grid 5, three stabilizing elements are regularly positioned, and other two stabilizing elements are positioned in the center of the plastic grid 5. Each stabilizing element passes through all four plastic grids 5 above the drainage layer 2. The stabilizing element is implemented as a hollow tube of a circular cross-section made of durable polypropylene, wherein the wall of the tube adjoins the walls of the hexagonal cells of the plastic grids 5. Each stabilizing element is connected by the wall of the tube to each of the four plastic grids 5 above the drainage layer 2by ultrasonic welding.
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The entire set of layers of the four plastic grids 5 above the drainage layer 2 is filled with loose unbound crushed aggregate of fraction 8/12 mm, which provides load-bearing capacity to the load-bearing layer 2, drainage function, and noise protection element function. The stabilizing elements (hollow tubes) are also filled with the aggregate. The surface layer 4 is laid on the last (uppermost) plastic grid 5, which is shown in Fig. 1 only schematically, wherein in the first exemplary embodiment, the surface layer 4 comprises live vegetation comprising stonecrops, wherein the stonecrops are supplied as pre-planted on a substrate layer made of natural coconut fibers. Thus, in this case the surface layer 4 does not comprise soil. The aggregate (filler) is not shown in the figure.
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In the following section, a method of manufacture of the tram cover to be laid according to the first exemplary embodiment will be described. The cover is laid in place when the rails, internal and external absorber, and the leveling layer are installed on the railway superstructure. In the first option of the method, the manufacture and installation of the tram cover occurs in two main stages, wherein the first stage takes place outside the installation location of the cover and the second stage takes place directly at the installation location.
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The first stage takes place where the plastic grids 5 themselves are manufactured and involves the preparation of the weldment of the plastic grids 5 with the drainage layer. The first bottommost plastic grid 5 is first filled with retention cups for water retention of the cover, wherein the retention cups are made of the same material as the plastic grids 5 and the stabilizing elements, i.e., durable polypropylene. The retention cups are inserted into the honeycomb structure of the plastic grid 5 in bulk. The drainage layer 2, i.e., synthetic geotextile, is then ultrasonically welded onto the first plastic grid 5. Subsequently, the remaining plastic grids 5 are also successively welded onto the drainage layer 2, wherein the cells of all honeycomb structures of the plastic grids 5 are aligned with each other. The ultrasonic welding of the elements is point-based. For welding the plastic grids 5 to the drainage layer 2 and for welding the plastic grids 5 to each other, the stabilizing elements are inserted into the selected cells of the honeycomb structures, which are ultrasonically welded to the drainage layer 2 and also to the walls of the cells of the honeycomb structure of each of the four plastic grids 5 to ensure cohesion of the drainage layer 2, the plastic grids 5, and the stabilizing elements for the joint transport of these elements to the cover installation location. This weldment is thus prepared in advance.
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The cover is installed directly at the location of the tram track, which already comprises the rails 1 fastened on the railway superstructure 6. First the subbase leveling layer 7 is placed between the rails 1, and subsequently, the internal and external absorbers 10, 11 are placed. The retention film 9 is then laid on the subbase layer 7 followed by the weldment, which comprises the first (bottommost) plastic grid 5 filled with retention cups for water retention, the drainage layer 2, and four plastic grids 5 with the placed stabilizing elements. After the correct and firm placing of the weldment, all plastic grids 5 as well as the stabilizing elements above the drainage layer 2 are filled with loose crushed aggregate. Therefore, the aggregate is poured through all plastic grids 5 and subsequently compacted, wherein after the surface is leveled, the surface layer 4 is installed on the upper surface of the aggregate, which is formed by an unfolded substrate of coconut fibers with the planted stonecrops.
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In the second option of the method, all the steps of manufacturing and installing the cover take place directly at the location of the tram track, which already comprises the rails 1 fastened on the railway superstructure 6. First the subbase leveling layer 7 is placed between the rails 1, and subsequently, the internal and external absorbers 10, 11 are placed. Subsequently, the drainage layer 2 is placed on the first plastic grid 5 in one step. Then the second plastic grid 5 is placed and ultrasonically welded onto the drainage layer 2, wherein subsequently, all remaining plastic grids 5 are successively placed and ultrasonically welded onto this second plastic grid 5. The filling of the plastic grids 5 with the aggregate and the installation of the surface layer 4 is the same as in the first option of the method of manufacture of the cover.
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The second exemplary embodiment is a composition of the cover that comprises a surface layer 4 with artificial grass. The structure of the cover is the same as in the first exemplary embodiment and differs only in that the surface layer 4 comprises a synthetic finish, wherein the synthetic finish comprises rubber and artificial grass. The artificial grass is made of synthetic fibers that imitate grass. The other features of the tram cover are identical to the features of the first exemplary embodiment, wherein the method of manufacture of the cover is identical to that of the first or second option.
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The third exemplary embodiment of the cover comprises the load-bearing layer 3 that comprises one plastic grid 5 below the drainage layer 2 and four plastic grids 5 above the drainage layer 2, wherein all these elements are interconnected by ultrasonic welds similar to the first exemplary embodiment. However, the honeycomb structure of each plastic grid 5 in the set of layers above the drainage layer 2 is offset with respect to the honeycomb structure of the adjacent plastic grid 5. Thus, this embodiment also comprises a framework composed of five mutually connected plastic grids 5, wherein the offset of the honeycomb structures of the plastic grids 5 increases the stiffness of the load-bearing layer 3 and eliminates possible buckling of the walls of the interconnected plastic grids 5, unlike an embodiment where the honeycomb structures are aligned. The other features of the tram cover are identical to the features of the first or second exemplary embodiment, wherein the method of manufacture of the cover is identical to that of the first or second option.
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The fourth exemplary embodiment of the cover comprises the load-bearing layer 3 that comprises one plastic grid 5 below the drainage layer 2 and four plastic grids 5 above the drainage layer 2, wherein all these elements are interconnected by ultrasonic welds similar to the first exemplary embodiment. In this embodiment, the honeycomb structure of the plastic grid 5 below the drainage layer 2 is closed, i.e., the honeycomb structure comprises a solid bottom with the retention function. Thus, this embodiment of the cover does not comprise the retention film or filling of the plastic grid 5 under the drainage layer 2 with retention cups. The other features of the tram cover are identical to the features of the first or second exemplary embodiment, wherein the method of manufacture of the cover is identical to that of the first or second option.
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The fifth exemplary embodiment of the cover comprises the load-bearing layer 3 that comprises only one plastic grid 5 with a hollow honeycomb structure, wherein this plastic grid 5 is placed on the drainage layer 2 and firmly connected to the drainage layer 5 by ultrasonic welding. The retention film 9 is positioned under the drainage layer 2. The other features of the tram cover are identical to the features of the first or second exemplary embodiment, wherein the method of manufacture of the cover is identical to that of the first or second option. This embodiment is preferred for covers of a tram or railway track with a low height of the rail.
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In the following section, alternative embodiments of the cover of a tram or railway track according to this invention will be provided.
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In an alternative embodiment, all of the aforementioned embodiments of the cover may be positioned only on the sides of the rails 1 or between the rails 1 and simultaneously on the sides of the rails 1.
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In an alternative embodiment, the cover may comprise the surface layer 4 with soil and live vegetation, wherein this embodiment may further comprise a second drainage layer 2 placed on the upper surface of the aggregate or other filler, i.e., between the uppermost plastic grid 5 and the surface layer 4. Thus, soil with live vegetation is layered on the second drainage layer 4, wherein in this case this second drainage layer 2 protects the filler of the load-bearing layer 3 from being clogged by the soil from the surface layer 4.
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In an alternative embodiment, the cover may comprise one, two, three, or five or more plastic grids 5 above the drainage layer 2, wherein the honeycomb structures of the plastic grids 5 may be aligned or offset in any combination. Arbitrary pairs of the plastic grids 5 may also be freely placed next to each other without performing ultrasonic welding. Arbitrary pairs of the plastic grids 5 may also be firmly connected to each other by surface ultrasonic welding.
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In an alternative embodiment, e.g., crushed concrete or brick may be used as the filler of the load-bearing layer 3. In addition, a lightweight filler, e.g., porous or fibrous natural or artificially manufactured material, e.g. expanded recyclate, wood material, etc. may be used. In another embodiment, pervious concrete or bound aggregate may be used, wherein the aggregate may be bound, e.g., with cement, asphalt, polymer binder, etc. The bound filler may have, e.g., a greater load-bearing capacity, but the disadvantage is that then the load-bearing layer 2 cannot be easily disassembled and repaired or replaced, wherein then the plastic grids 5 cannot be recycled.
List of Reference Signs
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- 1 -
- rail
- 2 -
- drainage layer
- 3 -
- load-bearing layer
- 4 -
- surface layer
- 5 -
- plastic grid
- 6 -
- railway superstructure
- 7 -
- leveling layer
- 8 -
- fastening of the rail
- 9 -
- retention film
- 10 -
- internal absorber
- 11 -
- external absorber