ZA200602610B - A sleeper with a coating on the bottom surface - Google Patents

Description

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A sleeper with a coating on the bottom surface

The invention refers to a sleeper with a coating or a footing on the bottom sur- ~ face formed by a composite plate.

Background art:

With conventional sleepers of prestressed concrete, concrete or steel, coatings (footings) on the bottom surface thereof are known with which the ballast- preserving characteristics of wooden sleepers are imitated.

With these so-called sleeper footings, bottom-face coatings of elastic materials are either applied in the production process during the concrete work or glued to the bottom faces of sleepers thereafter.

With elastic footings, in known methods, an elastic plastic material or rubber layer is provided with a grit coating already during the manufacturing thereof, the grit coating making a connection with the concrete during the production of concrete sleepers. Other methods prefer a profile in the footing that pro- vides adhesion to concrete.

It is known to join the elastic plastic material layer directly with the concrete body (FR-A-2 753 998). DE-A-4 315 215 further proposes to additionally ar- range a geotextile layer on the bottom face of the elastic plastic material layer averted from the concrete body. This arrangement serves to protect the elas- tic plastic material layer against the intrusion of sharp ballast points and re- sulting damages to the plastic material layer, but it does not serve to join the concrete sleeper and the elastic plastic material layer. With the sleeper known from EP-A-609 729, the geotextile layer is also arranged on an elastic plastic material layer which in turn is directly connected with the actual ballast sub- strate and does not contact the sleeper, but is provided beneath the ballast.

Elastic profiles (so-called footed sleepers) that are used for sclid roadbeds and enclose the sleeper partly, are not to be confused with footed sleepers accord- © ing to the present invention. ~All materials for the bottom-side coating of sleepers are required to have a surface strength that excludes an intrusion of sharp ballast points into this footing.

The elasticity of the materials, the resistance against the ballast point pres- sure, the possibility of adhesion to concrete and the service strength of the system are in conflict with each other and limit the durability and the function- ality, respectively.

Combinations of materials in which various layers of different materials are laminated and stacked upon each other in a sandwich structure are so com- plex that their implementation is questionable for financial reasons.

The disadvantage of known systems is that: - with such elastic footings, if an elastic rail fastening is used, the vibra- tion behavior is hard to define because of the natural vibration of the sleeper, and natural vibrations of the concrete sleeper are further possi- ble that cause damage to the system. - the rigidity demanded for elastic footings require materials of such soft- ness that resistance against damages caused by edges and points of the ballast can not be guaranteed. - the manufacture and the application of footings meeting the require- ments are so cost intensive that the use of elastic rail fastenings may possibly be more advantageous.

) Invention

It is an object of the invention to provide a concrete sleeper for railways, - whose footing is easily realized in terms of production technology and can be mounted elastically in a permanent manner.

The invention proposes a sleeper with a bottom-side coating or footing as de- fined in claim 1, a method as defined in claim 2 and a use mentioned in claim 3.

According to the invention, the design, the production and the application of sleeper footings are realized, while excluding the above disadvantages, by the fact that the sleeper footing is made of a multi-layered structure using a ran- domly oriented fiber material, such as a non-woven material and especially a geotextile, and at least one elastic plastic material layer having defined char- acteristics.

Non-woven materials and especially geotextiles surprisingly have excellent adhesion characteristics with respect to unset concrete, while at the same time showing plastic and elastic properties. By appropriately selecting the fiber structures, the fiber density, the fiber bonding (needling, fusion) and the layer thickness, this characteristic can be adapted to the respective requirements.

On the other hand, the fibers are suited for thermal bonding with elastic plas- tics. These plastic materials can in turn be adapted in their surface hardness, elasticity and strength to the requirements imposed by the sleeper footing.

The advantages obtained with the invention are surprising and have proven themselves in several test stand and long-term tests. These very positive test results are due to the novel connection between the elastic plastic material layer and the concrete body, which may also be called a "micro form fit". This micro form fit, i.e. the coupling or mechanical connection of the at least one elastic plastic material layer or, with a plurality of elastic plastic material lay-

Co 4 ) ers, the sandwich structure of these layers with or to the concrete body by means of the fibers of the non-woven layer results in an extremely high tear- off and shear resistance that provide for a permanent retention of the elastic - plastic material layer on the bottom side of the concrete body, even under the dynamical stresses typical for sleepers. Here, the non-woven layer causes a non-positive material pairing between the concrete and the plastic material.

The micro form fit along the above mentioned surface of the non-woven layer decisively increases the resistance of the plastics plate against being torn off of the concrete body, which is due to the fact that, due to the non-woven layer, the connection between the plastics plate and the concrete has become insensitive to shear forces and vibrations, since the plastics plate is quasi flexibly connected to the sleeper. Whereas, for manufacturing reasons, the geotextile is welded to the plastic material of the plate or at least the fiber ends of the non-woven are embedded in the material of the plastics plate, the concrete partly penetrates into the non-woven layer when the sleeper is cast, so that, after the concrete has set, the fibers get caught mechanically in the near-surface concrete layer. Instead of a geotextile, another (plastics) non- woven material or, generally speaking, a material with randomly oriented fi- bers may be used.

The following is a detailed description of the invention with reference to the drawing.

Similar to the known systems, the footings 10 are placed within the mold when the concrete sleepers 12 are made.

For example, the footing 10 is a plastic material layer 14 that is 3 mm to 5 mm thick and has a defined spring rate of, e.g.,100 kN/mm. When the plastic material layer exits from the extruder, a non-woven plastics layer, e.g. a geo- textile layer 16, is placed on the plastic material layer 14 which, for thermal reasons, is still in the plastic state, the non-woven layer being welded during the manufacture to the plastic material layer making use of the not yet cured state of the plastic material. The plastic material layer 14 may also be multi-

Co 5 ) layered instead of single-layered. The schematic illustration does not represent the welding of the fibers of the geotextile layer 16 with the plastic material layer 14, nor the embedding of the fibers in the concrete sleeper 12.

The plate obtained thus consists of a bottom elastic plastic material plate and a top geotextile layer non-positively welded thereto. The thickness of the geo- textile layer is about 3 mm to 10 mm. In the mounted state, the concrete sleeper 12 supporting the rails 18 rests on a roadbed 20.

In this embodiment, the composite plate described herein (at least one elastic plastic layer and a non-woven layer) is designed as a coating on the bottom side of a concrete sleeper. The concrete sleeper may be a sleeper of prestressed concrete or an untensioned concrete sleeper. The sleeper with the composite plate may be used for railway sections without branches or inter- sections, or for shunts, intersections or double slips. The composite plate may, however, be used on the bottom side of other concrete bodies resting on a substrate, such as soil, for example, paving stones, plates for pavements or drives, or the like. However, these applications of the composite plate are no embodiments of the present invention.

Claims (6)

Claims

1. A sleeper comprising - a concrete body (12) and - at least one elastic plastic material layer (14) arranged on the bottom side of the concrete body (12), characterized in that a layer of randomly oriented fibers, especially a non-woven layer, preferably a geotextiles layer (16) is arranged between the concrete body (12) and the at least one elastic plastic material layer (14), said layer of randomly oriented fibers adhering to the concrete of said con- crete body and being planarly connected with said at least one elastic plastic material layer (14).

2. A method for connecting a sleeper concrete body (12) with a roadbed (20) in a manner secured against shearing forces, said body having at least one elastic plastic material layer (14) arranged on the bottom side of the concrete body (12), fibers of a layer of randomly oriented fibers (16) being, on the one hand, embedded into the near-surface bottom portion of the concrete body (12) before the material thereof has set and, on the other hand, embedded into or welded to the material of the plastic material layer (14).

3. The use of a layer of randomly oriented fibers for connecting a sleeper concrete body (12) with a roadbed (20) in a manner secured against shearing forces, said body having at least one elastic plastic material layer (14) arranged on the bottom side of the concrete body (12), by, on the one hand, embedding fibers of a layer of randomly oriented fi- bers (16) into the near-surface bottom portion of the concrete body

(12) before the material thereof has set and, on the other hand, em- bedding these fibers into or welding them to the material of the plastic material layer (14).

4 A sleeper substantially as hereinbefore described with reference to and as illustrated in the accompanying schematic drawing.

A method substantially as hereinbefore described with reference to and as illustrated in the accompanying schematic drawing,

6. The use of a layer of randomly oriented fibers substantially as hereinbefore described with reference to and as illustrated in the accompanying schematic drawing. Date: 30 March 2006 John Spice DR GERNTHOLTZ INC Patent Attorneys of Applicants) P O Box 8; Cape Town 8000; South Africa Union Road; Milnerton 7441; South Africa Tel: (021) 551 2650 Fax: (021) 551 2960 DtG Ref: 652814 t:\ files\ 14\652814\652814p10.doc