EP4053350A1 - Load bearing semi-finished product - Google Patents

Abstract

Load-bearing semi-finished structure, in particular a grating or shaft cover for drainage channels, drain or inlet boxes or shafts, comprising lateral bearing areas (2) with longitudinal supports (3), and a plurality of transverse ribs (4) running between the longitudinal supports (3), the transverse ribs (4) have a dimensionally stable core (5) which is materially held between a top layer (6) and a bottom layer (7), characterized in that the top layer (6) and the bottom layer (7) each consist of a fiber-reinforced composite material with one or more layers of long or endless fibers aligned in the same direction and together with the dimensionally stable core (5) form a multi-layer, functionally graded multi-material composite.

Description

The present invention relates to a load-bearing semi-finished structure, in particular a cover grating or manhole cover for drainage channels, drain or inlet boxes or manholes, comprising lateral bearing areas with longitudinal beams, and a plurality of transverse ribs running between the longitudinal beams, the transverse ribs having a dimensionally stable core which is sandwiched between a cover fabric on the upper side and a non-woven cover fabric on the underside.

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

Drainage channels are used in the industrial as well as in the public or private sector. Their task 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 so that they can be driven over, because the areas to be drained, such as roads, parking lots, Courtyard and industrial areas should be available in their entirety.

Suitable covers or cover gratings are used for this task, which on the one hand completely cover the channel body embedded in the ground, but on the other hand are water-permeable so that the surface water running in can drain off. In order to prevent the covers from being unintentionally lifted off when driven over, the covers are usually firmly connected to the channel body. This is done either with a non-positive connection by screwing or with a quick-release system, in which the cover inserted in a channel frame is held back with a positive fit.

EN DIN 1433 classifies drainage systems into different load classes, starting with class A for traffic areas intended exclusively for pedestrians and cyclists through to class F for areas that can be driven on with particularly high wheel loads, such as flight 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 load-bearing structures in the form of ribs or honeycombs in a lower region, via which the loads can be absorbed. The structures are designed in such a way that due to their geometry, i.e. structure and component thickness, as well as due to the material used, considerable loads can be transferred.

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 support structure of a channel cover made of nodular cast iron. The thickness of the carrier increases in the areas where the tensile stress is highest. In areas of low tensile stress, the thickness of the beams decreases. The load is absorbed here by material-technically homogeneous support structures.

For simpler applications up to class C according to EN DIN 1433 or DIN 19580, covers are also made of plastics using the injection molding process. There are currently no known plastic covers for higher demands in terms of load-bearing capacity, such as those encountered on roads.

This is due to the poorer mechanical material properties of plastics compared to steel or cast steel. In order to get into higher load classes, significantly more material has to be used compared to steel or cast steel and therefore more solid constructions have to 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 damping, which reduces the noise that occurs during operation. Noise pollution from rattling noises is reduced or does not occur at all.

The low weight of plastic cover gratings also ensures easy handling during installation and quick and inexpensive transport. Removing the covers to allow the channel body to be cleaned is easy and can be done without great effort. Plastic covers can also be made to measure, which enables a high degree 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 is characterized by the fact that the fibers reinforce the plastics and raise them to a higher mechanical level. The decisive factor here is the interplay between the fiber and the plastic matrix. Although fibers alone can absorb high tensile forces, they are not components that are subjected to bending or pressure. Although unreinforced plastics can be components, they are sometimes brittle in the case of duroplastic reaction resins or too flexible in the case of thermoplastics. High-strength components can only be produced by combining fibers and plastic and firmly connecting the plastic matrix to the fibers.

the DE 102015101672 A1 deals with fiber-reinforced composite material and a manufacturing process for it. Two fiber-reinforced components are described that, due to the process, achieve better adhesion. the DE10105812A1 describes a method 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.

Furthermore, the prior art knows numerous descriptions of composite materials. That's on the EP 1901912 B1 , the EP 0956193 A1 and the EP 1868796 B1 to refer, in which thermoplastically deformable composite bodies are described from semi-finished products. In the EP 2791409 B1 and the WO 2010139077 A1 is 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 consists of wood; the material thickness is between 0.05 and 6.0 mm. These are thin-walled structures intended for the automotive sector. the DE10105813A1 describes a process for the production of a thermoplastically deformable, fiber-reinforced, thin semi-finished while in the DE10114553A1 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 nonwoven fabric layer made of thermoplastic fibers and optionally reinforcing fibers, and a fabric or scrim layer made of reinforcing fibers, the layers being needled together.

Also the one in the EP 1719611 A1 is a process for the production of 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 containing 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 structure, in particular a cover grating or a manhole cover for drainage channels, drain or inlet boxes or manholes, which consists of plastic and is both light and antimagnetic, but still sufficiently resilient for Traffic areas and at the same time can be produced inexpensively.

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

According to the invention, a load-bearing semi-finished product structure known from the prior art, in particular a cover grating or a Manhole cover for drainage channels, drain or inlet boxes or manholes, comprising lateral bearing areas with longitudinal members, as well as a plurality of transverse ribs running between the longitudinal members, the transverse ribs having a dimensionally stable core which is accommodated in a materially bonded manner between an upper-side cover fabric and a lower-side cover fabric.

The best mechanical properties are achieved in a composite material when its fibers are endless and aligned in the same direction, i.e. unidirectionally and isotropically. 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 produced in the pressing process. For this reason, the invention provides for creating a cover grating in which the top layer and the bottom layer are each formed from a fiber-reinforced composite material with long fibers aligned in the same direction or, particularly preferably, endless fibers. Depending on the application, the cover fabrics can be single-layer or multi-layer.

Especially in the case of structural components in construction, the materials are subject to very high static and dynamic loads and are therefore particularly required 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 cannot be compared with other materials for the channel cover and in some cases is also not resource-efficient. In particular, when a thick-walled component is subject to bending stress, the greatest compressive and tensile stresses and thus the greatest material stresses are on the outer surfaces. No tensions occur however in the so-called neutral Zone, which represents the plane of the geometric centroid 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, fiber reinforcement types and varying fiber volume contents results in a multi-layer, functionally graded multi-material composite.

Endless fibre-reinforced, unidirectional cover fabrics, together with graded core materials that are resistant to bending and buckling, enable a lighter construction while at the same time absorbing high loads. This means that the material can be used effectively in thick-walled structures.

The molding compounds are preferably made available as textile fabrics, as scrims or mats, but also in all other forms of provision such as shapeless compounds or other containers. There is a gradual reduction in the mechanical properties, especially the strength and possibly the weight of the material used, from the edge to the neutral bending zone in the core of the component. High-strength materials are found in the edge areas made of endless 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 grating 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 light material.

In a preferred embodiment, the single-layer or multi-layer cover fabrics can extend along an upper side and along an underside of the transverse ribs into the bearing areas. In addition, it can also be useful to also provide the textile fabrics on lateral 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 be thermoplastic foams or hollow glass spheres, which influence the mechanical properties and the 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 can be used as processing additives, which are used as fillers and reinforcing agents in thermoplastics. While talc and calcium carbonate improve the thermoformability of thermoplastics, aluminum hydrate, or aluminum hydroxide, is used because of its flame-retardant properties. Magnesium hydroxide can also be used instead of aluminum hydrate, particularly 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 inherently 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 firmly bonded. In a specific embodiment, the at least one intermediate layer can be formed from a fiber-reinforced matrix with non-directional short or long fibers.

The fibers used, whether in the intermediate layer or in the cover layers, 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 purpose. 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 cover fabric can be covered with a protective layer for mechanical, medial and/or thermal protection of the top cover fabric, whereby this protective layer can advantageously be a filled or unfilled, thermoplastic material, preferably polyolefins or polyamide . On the one hand, this protects the fibers worked into the upper cover fabric, on the other hand, it allows the surface of the cover grating 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 grating under pressure,

figure 2

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

figure 3

a section of a sectional view across a transverse rib of a cover grating according to the invention, and

figure 4

a detail of a sectional view along a transverse rib of a cover grating according to the invention.

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

figure 2 shows the structure of the cover grating 1 according to the invention, in which according to the figure 1 reproduced findings, a layer structure is provided as follows. In the middle of the layer model, ie in a material core of a transverse rib 4 of the cover grating 1, there is a core 5 which does not have to withstand any particular compressive or tensile stress. Materials that give the core stability are used in this low-load area. These are thermoplastic matrix systems made from polyolefins or polyamide. Optionally, these can contain fillers such as thermoplastic foams or hollow glass spheres, or they can be unreinforced 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 layered core is also possible according to the invention.

On the pressure side 11, on the other hand, a single-layer or multi-layer cover fabric 6 is provided on the upper side, 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. The same procedure is used with a single-layer or multi-layer cover fabric 7 on the underside provided on the tension side 12 , which absorbs the tension 14 . The long or particularly continuous fibers, which are able to absorb the forces acting in the longitudinal direction to a particular extent due to their longitudinal structure, are prepared in unidirectional layers, for example as fiber mats impregnated with matrix material, and are placed in a press mold, which is then further layered with the material of the core 5 is applied. In this case, the fiber mats can also be placed around the outer walls of the resulting cover grating 1, so that the in figure 3 rib cross-section shown with a peripheral scrim 6, 7 is formed. The scrim 6 on the upper side, as well as the scrim 7 on the underside, extends into a bearing area 2 in one or more layers, but can also run around the longitudinal beams 3 laterally terminating the transverse ribs 4 in order to form a complete outer skin. However, this is preferably not provided and the upper side, single or multi-layer cover fabric 6, as well as the lower side, single or multi-layer cover fabric 7 both end, as in figure 4 shown before reaching the long edge.

Additional intermediary intermediate layers 8 can be provided between the single-layer or multi-layer cover fabrics 6 and 7 and the core 5 of the transverse ribs 4, which fill out the areas of medium tensile or compressive stress. 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. Short fibers are sufficient in this area, if necessary long fibers or mixtures thereof. While the endless fibers are fibers with a length of 50 mm up to fibers that are actually continuous, the long fibers have a length of 1 to 50 mm, while the short fibers are 0.1 to 1 mm.

The layering described creates a density gradient in the cover grating 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 thickest layer, while the top layer 6 and 7, although they may be composed of one or more layers, represent the finest layers.

A load-bearing semi-finished structure is thus described above, in particular a cover grating or a manhole cover for drainage channels, drain or inlet boxes or manholes, which consists of plastic and is both light and antimagnetic, yet sufficiently resilient for traffic areas and at the same time can be produced inexpensively.

REFERENCE LIST

1

cover grid

2

bearing area

3

side members

4

cross rib

5

core

6

upper side, single or multi-layer cover scrim

7

Underside, single or multi-layer cover fabric

8th

intermediate layer

9

protective layer

10

Print

11

pressure side

12

train side

13

compressive stress

14

tensile stress

15

neutral zone

Claims (14)

Load-bearing semi-finished structure, in particular a grating or shaft cover for drainage channels, drain or inlet boxes or shafts, comprising lateral bearing areas (2) with longitudinal supports (3), and a plurality of transverse ribs (4) running between the longitudinal supports (3), the transverse ribs (4) have a dimensionally stable core (5) which is cohesively held between a cover layer (6) on the upper side and a cover layer (7) on the lower side,
characterized in that the upper-side cover fabric (6) and the underside cover fabric (7) are each formed from a fiber-reinforced composite material with one or more layers of long or endless fibers aligned in the same direction and together with the dimensionally stable core (5) a multi-layer, functionally graded multi-material composite form. Semi-finished product structure according to one or more of the preceding claims, characterized in that between the core (5) and the upper-side, single-layer or multi-layer cover scrim (6) and/or between the core (5) and the underside, single-layer or multi-layer cover scrim ( 7) at least one intermediate layer (8) is arranged, which is bonded to the surrounding layers (5, 6, 7). Semi-finished product structure according to Claim 2, characterized in that the at least one intermediate layer (8) is formed from a fiber-reinforced matrix with non-directional short or long fibers. Semifinished bonding structure according to one or more of the preceding claims, characterized in that the fibers are fibers made of glass, basalt or carbon, in particular natural fibers or synthetic fibers, or a mixture of several of the aforementioned fibers. Semi-finished structure according to one or more of the preceding claims, characterized in that the matrix is a thermoplastic material. Semi-finished product structure according to one or more of the preceding claims, characterized in that the single or multi-layer cover fabric (6, 7) extends along an upper side and along an underside of the transverse ribs (4) into the bearing areas (2). Semi-finished structure according to one or more of the preceding claims, characterized in that the dimensionally stable core (5) is formed from a matrix material with fillers. Semi-finished product structure according to Claim 7, characterized in that the fillers are thermoplastic foams or hollow glass spheres. 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. Semi-finished structure according to Claim 5 and/or 9, characterized in that the thermoplastics are polyolefins or polyamide. Semi-finished product structure according to Claim 9 and/or 10, characterized in that talcum, calcium carbonate or aluminum hydrate is added to the thermoplastics as processing additives. Semi-finished product structure according to one or more of the preceding claims, characterized in that the top-side, single-layer or multi-layer cover fabric (6) is provided with a protective layer (9) for mechanical, medial and/or thermal protection of the top-side, single-layer or multi-layer cover fabric (6 ) or whose protection against ultraviolet radiation is overcoated. Semi-finished structure according to Claim 12, characterized in that the protective layer (9) is formed from a filled or unfilled thermoplastic material. Semi-finished 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 markings.

Images