EP4053350B1 - Load bearing semi-finished product - Google Patents

Description

The present invention relates to a load-bearing semi-finished product structure, namely a cover grate or a shaft cover for drainage channels, drain or inlet boxes or shafts, comprising lateral support areas with longitudinal beams, as well as a plurality of transverse ribs running between the longitudinal beams, the transverse ribs having a dimensionally stable core which is between a is cohesively absorbed by a top layer and an underside layer.

Such a semi-finished product structure is already available WO 2017/220487 A1 previously known. A manhole cover is described there, which connects a top plate with the interposition of a ribbed plastic body to a bottom reinforcing element, although not cohesively. The load to be absorbed by the shaft cover is introduced into the reinforcing element and from there into the wall of the drainage body.

Drainage channels are used in both industrial and public or private sectors. Their job is to absorb surface water from paved surfaces and drain it away in a targeted manner. In the majority of applications, the drainage channels must be designed to be traversable because the areas to be drained, such as streets, parking lots, Farm and industrial areas should be available in their entirety.

For this task, suitable covers or cover gratings are used, which on the one hand completely cover the gutter body embedded in the ground, but on the other hand are water-permeable so that the incoming surface water can flow away. In order to prevent the covers from being unintentionally lifted out when driving over them, the covers are usually firmly connected to the gutter body. This is done either with a force-fitting screw connection or with a quick-release system, in which the cover inserted into a gutter frame is held back in a form-fitting manner.

EN DIN 1433 classifies drainage systems into different load classes, starting from class A for traffic areas intended exclusively for pedestrians and cyclists to class F for areas that can be used with particularly high wheel loads, such as aircraft operations areas. Depending on the application, the drainage systems, especially their covers, must be able to absorb very high static and dynamic loads. Covers therefore have supporting structures in the form of ribs or honeycombs in a lower area, through which the loads can be absorbed. The structures are designed in such a way that significant loads can be transferred due to their geometry, i.e. structure and component thickness, as well as the material used.

Classic materials for cover gratings are nodular cast iron, as well as hot-dip galvanized steel or stainless steel. The DE 102014104744 A1 describes the geometry of the supporting structure of a channel cover made of nodular cast iron. The thickness of the beams increases in the areas where the tensile stress is highest. In areas with low tensile stress, the thickness of the beams decreases. The load is absorbed here via support structures that are homogeneous in terms of material.

For simpler applications up to class C in accordance with EN DIN 1433 or DIN 19580, covers are also made from plastics using the injection molding process. There are currently no known plastic covers for higher requirements in terms of load capacity, such as those found in road areas.

This is due to the poorer mechanical material properties of plastics compared to steel or cast steel. In order to reach higher load classes, significantly more material must be used than steel or cast steel and therefore more massive constructions must be used. In addition, the technical plastics required for the technical solution, such as polyamide (PA) or polyphthalamide (PPA), which are also filled with short or long glass fibers, are significantly more expensive than, for example, cast steel.

Plastic covers also offer numerous advantages. First of all, they are rustproof and antimagnetic, the latter being particularly advantageous when used in the area of train platforms due to the magnetic fields that exist there. They also have a high degree of attenuation, which reduces noise that occurs during operation. Noise pollution caused by rattling noises is reduced or does not occur at all.

The low weight of plastic cover gratings also ensures they are easy to handle during installation and quick and inexpensive to transport. Removing the covers to enable the gutter bodies to be cleaned is easy and requires little effort. Plastic covers can also be manufactured with precise dimensions, which enables a high level of functional integration and high-quality designs.

In order to make plastics usable for high loads, they are combined with other components. Fiber-reinforced plastics or fiber-reinforced plastics are a subgroup of composite materials. they draw This is due to the fact that the fibers reinforce the plastics and raise them to a higher mechanical level. What is crucial is the interaction between the fiber and the plastic matrix. Although fibers alone can absorb high tensile forces, they cannot represent components subject to bending or pressure. Unreinforced plastics can be components, but are sometimes brittle in the case of thermoset reactive resins or too flexible in the case of thermoplastics. Only by combining fibers and plastic and firmly bonding the plastic matrix to the fibers can heavy-duty components be produced.

The DE 102015101672 A1 deals with fiber-reinforced composite material and a manufacturing process for it. Two fiber-reinforced components are described which, due to the process, achieve better adhesion strength. The DE 10105812 A1 describes a process for producing a flat semi-finished product. This is a fiber-reinforced component. The EP 2679377 B1 describes a computer-implemented method for determining the fiber orientations in a liquid with polymer chains for the injection molding process using simulation. The process treats short and long fibers.

The state of the art also contains numerous descriptions of composite materials. That's it EP 1901912 B1 , the EP 0956193 A1 and the EP 1868796 B1 to refer, in which thermoplastically deformable composite bodies made of semi-finished products are described. In the EP 2791409 B1 and the WO 2010139077 A1 it is about a flat composite material made of two components.

In the WO 2017009152 A1 a wood veneer-coated plastic molding is described. The top layer here is made of wood; the material thickness is between 0.05 and 6.0 mm. These are thin-walled structures intended for the automotive sector. The DE 10105813 A1 describes a process for producing a thermoplastically deformable, fiber-reinforced, thin semi-finished product, while in the DE 10114553 A1 a method for producing a thick, thermoplastically deformable, fiber-reinforced semi-finished product is described.

The EP 1714772 A1 describes a thermoplastically processable composite material made of at least one fiber fleece layer made of thermoplastic fibers and optionally reinforcing fibers, as well as a fabric or scrim layer made of reinforcing fibers, the layers being needled together.

Also those in the EP 1719611 A1 is about a process for producing a thermoplastically deformable, fiber-reinforced semi-finished product, consisting of two fiber-reinforced components. In the EP 1770115 A1 Another fiber-reinforced, flat semi-finished product is described.

The EP 1890868 B1 describes a rigid composite panel made of two fiber-reinforced components. The EP 2374611 A1 relates to a concrete formwork panel made of lightweight plastic with a core layer made of polypropylene that contains air voids and at least one cover layer made of compact polypropylene.

Against this background, the present invention is based on the object of creating a load-bearing semi-finished product structure, namely a cover grate or a manhole cover for drainage channels, drain or inlet boxes or shafts, which is made of plastic and is both light and antimagnetic, but still sufficiently resilient for Traffic areas and at the same time can be produced cost-effectively.

This is achieved through a semi-finished product structure according to the features of independent claim 1. Meaningful configurations of such a semi-finished product structure can be found in the subsequent dependent claims.

According to the invention, a load-bearing semi-finished structure known from the prior art, namely a cover grid or a Manhole cover for drainage channels, drain or inlet boxes or shafts, comprising lateral support areas with longitudinal beams, as well as a plurality of transverse ribs running between the longitudinal beams, the transverse ribs having a dimensionally stable core.

The best mechanical properties are achieved in a composite material when its fibers are introduced endlessly and aligned in the same direction, i.e. unidirectional and isotropic. There are reductions if the fibers are finite and undirected, i.e. anisotropic. The latter is usually the case with injection molding. In contrast, an isotropic state can be created during the pressing process. For this reason, the invention provides for the creation of a cover grid in which the top covering fabric and the bottom covering fabric are each formed from a fiber-reinforced composite material with long fibers aligned in the same direction or, particularly preferably, continuous fibers. Depending on the application, the covering scrims can be designed in one or more layers.

Particularly when it comes to structural components in construction, the materials are subject to very high static and dynamic loads and for this reason are particularly demanding in terms of strength and rigidity. Consequently, the use of long or continuous fiber-reinforced semi-finished structures is usually essential. In the case of a pure fiber-plastic composite construction, these high stresses can lead to very thick-walled components with wall thicknesses in the range of 20-50 mm or more, which is not comparable to other materials for the gutter cover and is sometimes also not resource-efficient. Particularly when a thick-walled component is subjected to bending stress, the greatest compressive or tensile stresses and thus the highest material stresses are present on the outer surfaces. However, no tensions occur in the so-called neutral Zone which represents the plane of the geometric center of gravity of the cross-sectional area.

Such a state of mechanical stress is the starting point for the invention. The combination of materials with different textile structures, types of fiber reinforcement and varying fiber volume content results in a multi-layer, functionally graded multi-material association.

Continuous fiber-reinforced, unidirectional cover fabrics, together with bending and dent-resistant, graded core materials, enable a lighter construction while at the same time supporting high loads. This means that materials can be used effectively in thick-walled structures.

The pressing compounds are preferably provided as textile fabrics, as scrims or mats, but also in all other forms of provision such as shapeless masses or other containers. This involves a gradual reduction in the mechanical properties, especially the strength and possibly the weight of the material used, from the edge towards the neutral bending zone in the core of the component. High-strength materials are located in the edge areas made of continuous fibers on both the compression and tension sides of the component. The core of the component contains short or long fiber reinforced and/or unfilled materials. The result is a cover grate that is particularly resilient on the pressure side and the tension side due to the composite materials with long or endless fibers inserted there, while the core of the construction can be made of inexpensive and lightweight material.

In a preferred embodiment, the single or multi-layer cover fabrics can extend along an upper side and along an underside of the transverse ribs into the support areas. In addition, it can also make sense to provide the textile fabrics on side surfaces in order to obtain a continuous surface.

Furthermore, the dimensionally stable core can preferably be formed from a matrix material with fillers. Specifically, thermoplastic matrix systems, preferably polyethylene or polyolefins, can be used for this purpose, which either have fillers or are used unfilled. If fillers are used, they can particularly advantageously be thermoplastic foams or hollow glass spheres, which influence the mechanical properties and component weight of the matrix systems.

Alternatively, the dimensionally stable core can also be formed from unreinforced thermoplastics, preferably with processing additives.

Talc, calcium carbonate or aluminum hydrate, which are used as fillers and reinforcing agents in thermoplastics, can be used as processing additives. While talc and calcium carbonate improve the thermoformability of thermoplastics, aluminum hydrate, or aluminum hydroxide, is used because of its flame-retardant properties. Instead of aluminum hydrate, magnesium hydroxide can also be used, especially at processing temperatures above 200 ° C.

In a preferred embodiment, at least one further intermediate layer can be arranged between the core and the upper, already single or multi-layer cover fabric and / or between the core and the lower single or multi-layer cover fabric, which is connected to the surrounding layers of the single or multi-layer Cover fabric is cohesively connected. In a specific embodiment, the at least one intermediate layer can be formed from a fiber-reinforced matrix with undirected short or long fibers.

The fibers used, be it in the intermediate layer or in the covering fabrics, can be fibers made of glass, basalt or carbon, in particular natural fibers or synthetic fibers, or a mixture of several of the aforementioned fibers, each in one or more layers act. Carbon and aramid fibers can also be used for this. The matrix is preferably a thermoplastic. In particular, polyolefins, polyamide, polybutylene terephthalates and polycarbonates are used as matrix materials.

In addition, with some advantage, the top covering fabric can be covered with a protective layer for mechanical, medial and / or thermal protection of the top covering fabric, whereby this protective layer can advantageously be a filled or unfilled, thermoplastic, preferably polyolefins or polyamide . On the one hand, this protects the fibers incorporated into the upper covering scrim, and on the other hand, it allows the surface of the cover grid to be designed more freely.

In this respect, the protective layer can have special features such as reflectors embedded in the surface, embossed patterns, anti-slip elements and/or markings.

The invention described above is explained in more detail below using an exemplary embodiment.

Figur 1

eine schematische Darstellung eines unter einem Druck stehenden Abdeckrostes,

Figur 2

eine schematische Darstellung des Schichtaufbaus eines erfindungsgemäßen Abdeckrostes,

Figur 3

ein Ausschnitt einer Schnittdarstellung quer durch eine Querrippe eines erfindungsgemäßen Abdeckrostes, sowie

Figur 4

ein Ausschnitt einer Schnittdarstellung längs durch eine Querrippe eines erfindungsgemäßen Abdeckrostes.

Show it

Figure 1

a schematic representation of a cover grate under pressure,

Figure 2

a schematic representation of the layer structure of a cover grate according to the invention,

Figure 3

a detail of a sectional view across a transverse rib of a cover grate according to the invention, and

Figure 4

a section of a sectional view along a transverse rib of a cover grate according to the invention.

Figure 1 shows a schematic representation of a general cover grate 1, which is placed on two supports and on which a pressure 10 is exerted. Such a pressure can act when driving over the cover grate 1, for example, by the weight of a vehicle acting on the cover grate 1. First, the cover grate 1 will bend downwards under the pressure 10. This creates a compressive stress 13 on an upper pressure side 11, so the material of the cover grate 1 is compressed in the area of the surface, since the bending of the cover grate causes compression. On the opposite underside of the cover grate 1, however, there is now the tension side 12, where the material bulges. Due to the curvature of the material on the tension side 12, it is exposed to a tensile stress 14 there. In the middle between both sides there is a core area of the cover grate 1, the exact center plane of which represents the so-called neutral zone 15. The neutral zone 15 is stress-free, the compressive stress 13 increases from the neutral zone 15 in the direction of the pressure side 11, the tensile stress 14 in the direction of the tension side 12. The different layers of the cover grate 1 are therefore exposed to different loads depending on the layer depth.

Figure 2 shows the structure of the cover grate 1 according to the invention, in which according to the in Figure 1 Based on the findings presented, a layer structure is provided as follows. In the middle of the layer model, i.e. in a material core of a transverse rib 4 of the cover grate 1, there is a core 5 which does not have to withstand any particular pressure or tensile load. In this low-stress area, materials are used that give the core stability. These are thermoplastic matrix systems made of polyolefins or polyamide. These can optionally contain fillers such as thermoplastic foams or hollow glass spheres, or from unreinforced ones Thermoplastics can be made with processing additives such as talc, calcium carbonate or aluminum hydrate. A layering of several of these possible matrix systems to form a layer core is also possible according to the invention.

On the pressure side 11, however, a top-side, single- or multi-layer cover fabric 6 is provided, which can absorb the compressive stress 13. Long or continuous fiber-reinforced, thermoplastic matrix systems made of polyolefins or polyamide with reinforcing fibers made of glass, basalt, carbon, synthetic or natural fibers, and mixtures thereof are suitable for this. Accordingly, the procedure is carried out with a single or multi-layer cover fabric 7 provided on the underside of the tension side 12, which absorbs the tension 14. The long or particularly preferably endless fibers, which due to their longitudinal structure are able to absorb the forces acting in the longitudinal direction to a particular extent, are prepared in unidirectional layers, for example as fiber mats soaked with matrix material, and are placed in a press mold, which is further layered with the material of the core 5 is applied. The fiber mats can also be placed around the outer walls of the resulting cover grid 1, so that the in Figure 3 Rib cross section shown with a circumferential cover fabric 6, 7 is created. The top covering fabric 6, as well as the bottom covering fabric 7, extend in one or more layers into a support area 2, but can also run around the longitudinal beams 3 that laterally close off the transverse ribs 4 in order to form a complete outer skin. However, this is preferably not provided for and the top-side, single- or multi-layer cover fabric 6, as well as the bottom-side, single- or multi-layer cover fabric 7 both end as shown in Figure 4 shown, even before reaching the longitudinal edge.

Between the single or multi-layer cover fabrics 6 and 7 and the core 5 of the transverse ribs 4, additional mediating intermediate layers 8 can be provided, which fill the areas of medium tensile or compressive load. These consist of thermoplastic matrix systems such as polyolefins or polyamide, which are fiber-reinforced like the single or multi-layer cover fabrics 6 and 7, but not necessarily with long or continuous fibers. In this area, short fibers are sufficient, if necessary long fibers or mixtures thereof. While the continuous fibers are fibers with a length of 50 mm up to actually continuous fibers, the long fibers have a length of one to 50 mm, while the short fibers have a length of 0.1 to 1 mm.

The described layering creates a density gradient in the cover grid 1, since the density of the material used decreases from the outside to the inside, while conversely the thickness of the layers increases in the same direction, so that the core 5 forms the strongest layer, while the covering fabric 6 and 7, although they can be made up of one or more layers, represent the finest layers.

Described above is a load-bearing semi-finished product structure, namely a cover grate or a shaft cover for drainage channels, drain or inlet boxes or shafts, which is made of plastic and is both light and antimagnetic, yet sufficiently resilient for traffic areas and at the same time can be produced inexpensively.

REFERENCE SYMBOL LIST

1

Cover grid

2

Support area

3

Longitudinal beam

4

transverse rib

5

core

6

Top-side, single or multi-layer cover fabric

7

Underside, single or multi-layer cover fabric

8th

Interlayer

9

protective layer

10

Pressure

11

Print page

12

Train side

13

Compressive stress

14

Tensile stress

15

neutral zone

Claims (14)

1. A load-bearing semi-finished product structure, namely a cover grate or a shaft cover for drainage channels, outlet or inlet boxes or shafts, comprising lateral support regions (2) with longitudinal members (3), as well as a plurality of transverse ribs (4) extending between the longitudinal members (3), the transverse ribs (4) having a dimensionally stable core (5),
   characterized in that the dimensionally stable core (5) is held in a firmly bonded manner between a top-side cover fabric (6) and a bottom-side cover fabric (7),
   wherein the top-side cover fabric (6) and the bottom-side cover fabric (7) are each formed from a fiber-reinforced composite material having one or more layers of long or continuous fibers aligned in the same direction and, together with the dimensionally stable core (5), form a multi-layer, functionally graded multi-material composite.
2. The semi-finished product structure according to claim 1, characterized in that at least one intermediate layer (8) is arranged between the core (5) and the top-side, single-layer or multi-layer covering fabric (6) and/or between the core (5) and the bottom-side, single-layer or multi-layer covering fabric (7), which is connected with the surrounding layers (5, 6, 7) in a firmly bonded manner.
3. The semi-finished product structure according to claim 2, characterized in that the at least one intermediate layer (8) is formed from a fibre-reinforced matrix having non-directional short or long fibres.
4. The semi-finished product structure according to one or more of the preceding claims, characterized in that the fibres are fibres of glass, basalt or carbon, in particular natural fibres or synthetic fibres, or a mixture of a plurality of the aforementioned fibres.
5. The semi-finished product structure according to claim 3, characterized in that the matrix is a thermoplastic material.
6. The semi-finished product structure according to claim 2, characterized in that the single-layer or multi-layer covering fabric (6, 7) extends along an upper side and along an underside of the transverse ribs (4) into the support regions (2).
7. The semi-finished product structure according to one or more of the preceding claims, characterized in that the dimensionally stable core (5) is formed from a matrix material including fillers.
8. The semi-finished product structure according to claim 7, characterized in that the fillers are thermoplastic foams or hollow glass spheres.
9. The semi-finished product structure according to one or more of claims 1 to 6, characterized in that the dimensionally stable core (5) is formed from unreinforced thermoplastics.
10. The semi-finished product structure according to claim 5 and/or 9, characterized in that the thermoplastics are polyolefins or polyamide.
11. The semi-finished product structure according to claim 9 and/or 10, characterized in that talc, calcium carbonate or aluminium hydrate is added to the thermoplastics as processing additives.
12. The semi-finished product structure according to claim 2, characterized in that the top-side, single-layer or multi-layer covering fabric (6) is coated with a protective layer (9) for mechanical, medial and/or thermal protection of the top-side, single-layer or multi-layer covering fabric (6) or its protection against ultraviolet radiation.
13. The semi-finished product structure according to claim 12, characterized in that the protective layer (9) is formed from a filled or unfilled thermoplastic material.
14. The semi-finished product structure according to claim 12 and/or 13, characterized in that the protective layer (9) has embedded reflectors, embossed patterns, anti-slip elements and/or marks.

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