DK2678490T3

DK2678490T3 - SUSTAINABLE OR CARRIING LIGHT WEIGHT ELEMENT

Info

Publication number: DK2678490T3
Application number: DK11794641.8T
Authority: DK
Inventors: Harry Klein; Peter Meyer
Original assignee: Meyer Yvonne; Wolter Antje; Wolf Thomas
Priority date: 2011-02-25
Filing date: 2011-11-28
Publication date: 2019-04-23
Also published as: EP2678490A1; WO2012113423A1; EP2678490B1; HRP20190636T1

Description

The invention relates to a load-bearable or load-bearing lightweight construction element according to the preamble of Claim 1.

From DE 100 18 710 Al there is already known a lightweight construction element of the aforementioned kind as a wall element, having a support structure consisting of tubular hollow bodies arranged alongside each other and/or one above the other, and carrying a coating to form the wall surfaces. The elongated tubular hollow bodies are made from paper, cardboard, plastics or the like. Recycling paper is especially preferred as a cheap starting material for making the hollow bodies, since the rough surface in this case improves the adherence of the coating, formed preferably as a plaster layer. However, the plaster layer increases the weight of the lightweight construction elements, without improving the load bearing ability of the support structure. Moreover, untreated tubular hollow bodies made of paper or cardboard have only a limited load bearing ability in their longitudinal direction, unless they have very thick boundary walls, which once again increases the weight of the lightweight construction elements. A further drawback of the known lightweight construction elements is that tubular hollow bodies made of paper can easily take up water from the environment or from the plaster layer, so that their load bearing ability greatly diminishes. DE 2836418 A already discloses lightweight construction elements of the aforementioned kind, in which cylindrical paper tubes impregnated with synthetic resin form a multichamber hollow profile, wherein both the tubes and the spandrels between the tubes may be filled with a hardened foam plastic for stiffening or improving the force transmission. EP 1522648 Al, CH 323528 A, WO 2007/123398 A2 and DE 2117794 A disclose sheetlike lightweight construction elements of paper or cellulose, while WO 2009/045095 Al and GB 2341619 A disclose panels with a honeycomb structure.

Starting from this, the problem which the invention proposes to solve is to improve a load-bearable or load-bearing lightweight construction element of the kind mentioned above so that its load bearing ability is further improved.

This problem is solved according to the invention by the combination of features of Claim 1.

The hard foam used is a hard foam having a large total pore volume and thus a low specific weight, yet in which the individual pores are very small and according to the invention they have cross section dimensions of less than 0.5 mm. The hard foam is a hardening reaction foam plastic, namely a highly crosslinked hard polyurethane foam, also known as PIR foam. When using such a hard foam, two or more components of the starting material are placed in a mould containing the tubular hollow bodies and they are cross-linked or hardened in the mould.

It has been established by experiments that a coating or impregnation which is water repellent and which increases the bending and/or compressive strength of the paper can increase the load bearing ability of the multichamber hollow profile by a multiple, and thus also the load bearing ability of the overall lightweight construction element, as compared to that of the tubular hollow bodies of untreated paper as per DE 100 18 710 Al, arranged alongside each other and provided with a plaster layer, for corresponding cross section dimensions and wall thickness. At the same time, the water repellent coating prevents moisture from getting into the paper after the lightweight construction element has been installed over the course of the lifetime of the lightweight construction element, such as might impair the strength of the hollow profile and thus the load bearing ability of the lightweight construction element.

One preferred embodiment of the invention calls for applying the hard foam on at least one outer side of the multichamber hollow profile facing away from the chambers. Thanks to the use of the hard foam as top layer or alternatively as intermediate layer between the outside of the hollow profile and an additional top layer, the weight can be further reduced as compared to the known lightweight construction element and on the other hand the strength can also be increased, since the hard foam despite a very low specific weight has a higher strength than plaster or gypsum. The load bearing ability can be further boosted by the mutual connection of the boundary walls of the chambers, since in this way a buckling of individual boundary walls or wall sections is hindered.

In this case, the boundary walls of the neighbouring chambers are advisedly joined together by the water repellent coating applied to the outer surfaces of the boundary walls, which glues together the boundary walls lying against each other. In places where the hard foam is applied to the outside of the multichamber hollow profile, the boundary walls of the neighbouring chambers are advisedly joined together by the hard foam, which likewise acts as a glue or bonding agent and holds the boundary walls together .

With the combination of features according to the invention, sheetlike lightweight construction elements can be produced with a weight per unit area of less than 2 kg/m2 for a thickness of around 50 mm, which are able to bear loads of more than 10 t parallel to the direction of the longitudinal central axes of the chambers in a width of 1000 mm.

In order to prevent moisture from getting in to the paper, the boundary walls of the chambers are provided with the coating and/or impregnation on both their inner and outer circumference, so that moisture cannot get in to the paper either from the inside or the outside and thereby impair the bending and/or compressive strength of the boundary walls of the chambers and thus that of the lightweight construction element. Furthermore, a two-sided inner and outer coating and/or impregnation can achieve a greater increasing of the bending and/or compressive strength than in the case of a single-sided coating and/or impregnation and thus a further increasing of the load bearing ability of the lightweight construction elements.

Preferably, the coating and/or impregnation consists of a resin which is applied in liquid state to the inner and outer circumferential surfaces of the tubular hollow bodies either after or during the manufacturing of the tubular hollow bodies from paper and then hardened. Advisedly, a resin is used which hardens quickly with or without adding heat, preferably a thermosetting reaction resin in the form of a binary system, comprising besides the reaction resin an accelerant or catalyst to accelerate the hardening. One preferred embodiment of the invention calls for the use of a poly- or epoxy isocyanurate resin, such as a poly- or epoxy isocyanurate resin available from the firm Bayer MaterialScience under the brand name Blendur. Alternatively, however, other resins may also be used, such as epoxy resins or phenolic resins which are likewise water repellent in the hardened state and increase the bending and/or compressive strength of the tubular hollow bodies made of paper.

According to the invention, the hollow profile consists of one or more rows of tubular hollow bodies alongside each other, resting by their outer circumference against the outer circumference of adjacent tubular hollow bodies and being bonded to the adjacent hollow bodies, wherein each hollow body bounds one of the parallel chambers. In order to facilitate the introducing of hard foam into the intermediate spaces or spandrels between adjacent hollow bodies, as an alternative the hollow profile may consist of one or more rows of tubular hollow bodies which are spaced apart and placed next to each other, so that the fluid hard foam can be introduced from one side into a mould previously outfitted with the hollow bodies, where it penetrates through the gaps between the adjacent hollow bodies and thus fills up the entire mould. This alternative is especially well suited to wall elements having only one or two rows of elongated hollow bodies embedded in hard foam. In particular, such wall elements may be readily used to make walls of freight containers, railroad cars, or other means of transportation where a low weight per unit of surface is of special advantage.

In order to facilitate the manufacture of such tubular hollow bodies made from paper, these advantageously possess cylindrical outer and inner circumferential surfaces or a circular ring cross section, so that they can be produced on existing machines, such as those which are used in the fabrication of winding cores made of paper or cardboard from kitchen towel or toilet paper rolls. These winding cores are made by winding two or more striplike layers of paper on a mandrel in a helix and overlapping each other, while a glue is applied to one or both paper strips in the overlapping regions. Alternatively, however, the tubular hollow bodies can also be made by winding broader sheets or webs of paper in several layers on top of each other in the circumferential direction of the tubular hollow bodies. This alternative of the invention has an especially large load bearing ability.

If the tubular hollow bodies according to this alternative lie by their outer circumferential surfaces against the outer circumferential surfaces of adjacent tubular hollow bodies and are bonded to each other by the coating and/or the hard foam, the load-bearing lightweight construction element can be further stiffened and, if it is used as a sheetlike wall element or as a columnar support element, its compressive strength in the vertical direction can be further increased, since the adjacent tubular hollow bodies mutually brace each other and mutually hold each other in their position, which prevents a buckling of individual tubular hollow bodies under loading. Thanks to the mutual bearing of adjacent tubular hollow bodies, the volume of the chambers on the inside of the tubular hollow bodies can also be increased as compared to the total volume of the lightweight construction element and hence the weight of the latter can be further decreased, without impairing the load bearing ability, since the latter is provided in large measure by the tubular hollow bodies.

The paper used in this case is preferably paper of low quality, advisedly a recycling paper, which need only have a slight bending and/or compressive strength without the coating and/or impregnation, yet which should preferably have a rough surface and a certain absorbency in order to ensure that a sufficient quantity of the applied liquid coating and/or impregnation remains sticking to the surface of the paper and advantageously penetrates at least somewhat into the paper.

It has been established by experiments that already a relatively slight wall thickness of the boundary walls of the chambers is enough to give the lightweight construction element a very large load bearing ability, so that the boundary walls according to another advantageous embodiment of the invention consist of fewer than eight overlapping coats or layers, preferably fewer than five coats or layers, and at best only two to three coats or layers of paper, so that the wall thickness of the boundary walls is less than 4 mm, preferably less than 2 mm, and at best less than 1 mm. With this wall thickness of the boundary walls, the chambers may advisedly have cross section dimensions of around 50 mm, so that the ratio between the wall thickness of the tubular hollow bodies and the cross section dimensions is advisedly less than 1:25, preferably less than 1:50 and at best around 1:100. With such dimensions, load-bearing lightweight wall elements can be produced which require no supporting construction when building single-storey houses with a roof.

If the lightweight construction element is supposed to be used as a sheetlike wall element or as a columnar support element, the hollow profile will be oriented such that the longitudinal axes of the parallel chambers have a vertical orientation. In this way, the boundary walls possess their greatest compressive strength in the direction in which the weight of structural parts placed on top of the load-bearing wall or support element is acting, so that the wall or support element achieves a maximum load bearing ability. The hollow profile in this case advantageously extends continuously from an upper to a lower end of the lightweight construction element.

If the wall or support element is supposed to have a relatively small thickness, the hollow profile advisedly comprises only a single row of chambers arranged alongside each other, whose longitudinal central axes advisedly lie on the same line in cross section.

On the other hand, in the case of larger wall thicknesses two or more rows of chambers can be placed alongside each other, the chambers of neighbouring rows advisedly having longitudinal central axes set off from each other in order to ensure the tightest possible packing of the chambers and a low weight per unit of surface. If the hollow profile consists of parallel cylindrical hollow bodies, the hard foam fills the spandrels between the tubular hollow bodies, whereby it joins adjacent hollow bodies to each other and prevents a mutual shifting or displacement of adjacent hollow bodies under loading.

An additional reinforcement of the lightweight construction element can be achieved in that one or more coats of a fibre-reinforced resin, such as polyurethane, with a fibre fabric or fibre laying embedded therein, are applied to one or both of the broad sides, preferably directly onto the flat surface of the hard foam. On top of the fibre-reinforced resin coat, a surface top coat can be applied as a finish.

At the upper and lower ends of each wall or support element there are preferably placed finishing elements, which close the open upper and lower ends of the chambers. The finishing elements of lightweight wall elements are preferably elongated and extend along the upper and lower end, being provided with protrusions on one side, which can be introduced into the open ends of the parallel chambers. The finishing elements on the one hand ensure that the upper and lower end of the chambers is closed and the wall or support elements have no openings at the upper and lower ends, and on the other hand they also improve the cohesion of the wall or support elements when they consist of tubular hollow bodies. The finishing elements are advisedly joined by the hard foam to the rest of the lightweight construction element, for example by applying them prior to the hardening of the hard foam.

If the lightweight construction element is supposed to be used as a sheetlike floor or ceiling element, the parallel chambers likewise have vertical longitudinal central axes, but then a plurality of short tubular hollow bodies are arranged in rows and set off from each other, so that they are oriented perpendicular to the broad side faces of the floor or ceiling element and jointly form a honeycomb structure. In this case, the upper and the lower ends of the chambers or the honeycomb structure can be closed by boards, which lie against the flush upper or lower end faces of the hollow profile.

Alternatively, the upper and lower ends of the chambers or the honeycomb structure may also be closed by one or more layers of a fibre-reinforced resin or synthetic resin, for example, in that the fibre reinforcement is a fleece, a weaving, or a laying of fibres and is placed on the respectively upward-turned or oriented broad sides of the honeycomb structure, so that the fleece, weaving or laying entirely covers the open ends of the chambers, and it is then impregnated with the resin and the resin is hardened. The resin may preferably be a thermosetting synthetic resin which becomes cross-linked and hardened by the supplying of heat or UV radiation, or a binary resin. The fibre reinforcement, depending on the required strength, may consist of glass, carbon, aramid or artificial fibres. If needed, one or more further layers of fibre-reinforced resin and possibly an additional surface top coat may be applied as finishing. Alternatively, the honeycomb structure may also be placed with its respectively down-turned broad sides on a resin-impregnated layer of the fibre fleece, weaving, or laying, in order to close the ends of the chambers. In both instances, the ends of the boundary walls of the chambers are joined to the resin as it hardens, so that they are then firmly bonded to the layers of fibre-reinforced resin and form a floor or ceiling element with high bending stiffness.

This kind of lightweight construction element can be used with advantage as a floor or ceiling element for a freight or residential container, such as a marine or transport container, since the floor and ceiling of the latter still consist of so-called multiplex boards at the moment, which are made of a tropical wood that is no longer available.

If the load-bearing lightweight construction elements are used in the construction of buildings or the like, they must have an adequate fire resistance, there being demanded in Germany at least fire protection class BIS-DO, although fire protection class A is preferred. In order to heighten the fire resistance of the lightweight construction elements, on the one hand a material with a relatively high temperature resistance is used advantageously for the coating or impregnation of the tubular hollow bodies, such as the already mentioned poly- or epoxy isocyanurate resin, and on the other hand a temperature resistant hard foam is used which has shape stability at higher temperatures, such as the already mentioned PIR foam of fire protection class BIS-DO or Al. This hard foam has a specific weight of 40 kg/m3 and is thus very light, but on the other hand it has such hardness that it can be bored or otherwise machined.

This makes it possible to form the hard foam on the mutually facing narrow sides of the adjacent lightweight construction elements in a tongue and a groove during their manufacture, so that the adjacent lightweight construction elements can be plugged together and thus easily joined to each other. Basically, it is also possible to mill the tongues and grooves in the hard foam at their narrow sides after the manufacture of the lightweight construction elements. Alternatively, the tongues and grooves can also be formed by metal or plastic profiles on the mutually facing narrow sides of adjacent lightweight construction elements, which are glued by the hard foam to the hollow profile. Fire protection class Al can also be achieved in that the hard foam is composed of microscopic hollow glass beads embedded in a nonflammable matrix, such as a water glass glue.

Since a lightweight construction element with a hollow profile of cylindrical tubular hollow bodies arranged alongside each other has an irregular surface structure, unsuitable for a wall surface, a further advantageous embodiment of the invention especially in the case of wall elements calls for the hard foam to form at least one and preferably two flat broadside surfaces. However, the lightweight construction element may also be provided with one or two additional top layers, which are formed by a sheet lying by one broad side against the hard foam and/or the hollow profile.

Preferably, in the latter case, sheets of a mineral material are used to increase the fire resistance, preferably mineral boards made of magnesium oxide and magnesium chloride with a fibre glass reinforcement, available commercially under the brand name of Megapan, which are applied in a thickness of a few millimetres as a cover layer on the lightweight construction element, so that they form the visible outer surfaces. The boards are preferably connected by the hard foam to the hollow profile or are glued to it.

In the following, the invention shall be explained more closely with the aid of an exemplary embodiment shown in the drawing. There are shown:

Fig. 1 a partly cutaway perspective view of parts of two lightweight wall elements;

Fig. 2 an enlarged cross section view of one of part of the lightweight wall elements of Fig. 1;

Fig. 3 a partly cutaway perspective view of parts of two modified lightweight wall elements;

Fig. 4 an enlarged cross section view of part of one of the lightweight wall elements of Fig. 3;

Fig. 5 a partly cutaway perspective view of parts of two further modified lightweight wall elements;

Fig. 6 an enlarged cross section view of part of one of the lightweight wall elements of Fig. 5;

Fig. 7 a partly cutaway perspective view of part of a still further modified lightweight wall element;

Fig. 8 an enlarged cross section view of part of the lightweight wall element of Fig. 7;

Fig. 9 an enlarged side view of a segment of a finishing strip for the upper or lower end face of the lightweight wall element of Fig. 1;

Fig. 10 an enlarged bottom view of the segment of finishing strip from Fig. 4;

Fig. 11 an enlarged cross section view of part of a further lightweight wall element not according to the invention;

Fig. 12 an enlarged cross section view of part of another lightweight wall element not according to the invention;

Fig. 13 an enlarged cross section view as per Fig. 12, but with a thermal insulation granulate in a portion of the chambers of a lightweight wall element not according to the invention;

Fig. 14 a cross section view of a columnar lightweight construction element;

Fig. 15 a cross section view of a lightweight construction element designed as a floor or ceiling board;

Fig. 16 a partly cutaway enlarged perspective view of the lightweight construction element of Fig. 15.

Fig. 17 a partly cutaway enlarged perspective view of another lightweight construction element designed as a floor or ceiling board.

The load-bearable or load-bearing lightweight construction elements 2 represented in the drawing each comprise a multichamber hollow profile 4, which encloses one or more rows of chambers 6 with parallel longitudinal central axes 8 and an opening cross section which remains constant in the direction of the longitudinal central axes 8.

In the lightweight construction elements 2 of Figures 1 to 10 as well as 14 to 17, the multichamber hollow profile 4 consists of multiple interconnected cylindrical hollow bodies 12 made of paper, whose outer and inner circumferential surfaces 14, 16 are coated with a resin 10 and which together with the coating of resin 10 form the boundary walls of the chambers 6. In the lightweight construction elements 2 of Figures 1 to 10 as well as 14 to 16, the hollow bodies 12 are embedded in a hard foam 18, which fills the spandrels 20 between the neighbouring tubular hollow bodies 12 and likewise joins the hollow bodies 12 to each other.

When the lightweight construction element 2 is a wall element, as shown in Figures 1 to 8, or a support element, such as a column, as shown in cross section in Fig. 14, the tubular hollow bodies 12 are arranged next to each other inside the lightweight construction element 2 in a parallel and vertical orientation. The hollow bodies 12 of the lightweight construction elements 2 in Figures 1 to 8 and 14 to 17 rest by their outer circumferential surfaces 14 against the outer circumferential surfaces 14 of adjacent hollow bodies 12, so that the hollow bodies 12 brace each other.

In the lightweight wall elements 2 in Figures 1 to 8, depending on the thickness of the wall element 10 and the diameter of the tubular hollow bodies 12 used, a single row of tubular hollow bodies 12 arranged alongside each other may be provided between two opposite broad sides 22, whose longitudinal central axes 8 subtend a vertical plane, as in Figures 1 to 4, 7 and 8, or several rows may be so arranged, as shown in Figures 5 and 6. If the lightweight wall element 2 contains several rows of tubular hollow bodies 12, the longitudinal central axes 8 of the hollow bodies 12 in adjacent rows of hollow bodies 12 are set off from each other by the diameter of the hollow bodies 12, so that the rows are interlocked and the hollow bodies 12 brace each other not only parallel and perpendicular to the broad sides 22 of the lightweight construction element 2, but also at an acute angle of 45 degrees to these directions. Furthermore, in this way the volume of the interstices or spandrels 20 between the adjacent hollow bodies 12 that are filled with hard foam 18 is minimized.

The tubular hollow bodies 12 consist of multiple layers or coats of wrapped recycling paper partly or entirely glued together. The layers or coats may each consist of spiral paper strips that are wrapped continuously on a mandrel, so that they overlap with adjacent windings or strips, and are glued together at the overlap sites. However, the layers or coats may also consist of broader sheets or webs that are wound in the circumferential direction of the hollow body 12. No special quality requirements are placed on the recycling paper.

For lightweight construction elements 2 in the form of wall or support elements, the tubular hollow bodies 12 have a length corresponding to the height of the wall or support element 2, and they are open at their opposite ends. The ratio between the outer diameter and the wall thickness of the tubular hollow bodies 12 is greater than 25:1, preferably greater than 50:1 and at best it is between around 50:1 and around 100:1. In the latter instance, the wall thickness of the hollow bodies 12 is around 0.5 mm for a diameter of around 50 mm. The weight of the hollow bodies 12 coated with resin 10 prior to being embedded in the hard foam 18 is less than 100 g, preferably less than 50 g and at best less than 25 g per metre of length.

The resin 10 used for the coating is an epoxy or polyisocyanurate reaction resin based on MDI or a modified epoxy or polyisocyanurate reaction resin, both of which are commercially available under the brand name of Blendur from the firm Bayer MaterialScience. Depending on the composition, these resins trimerise either after adding a catalyst and supplying heat or without the need for a catalyst, simply by supplying heat, to form a highly cross-linked thermosetting resin or plastic with excellent thermal stability. The cross-linking or curing of the resin occurs after the resin 10 is applied to the outer and the inner circumferential surfaces 14, 16 of the hollow bodies 12, which occurs preferably immediately after the winding of the hollow bodies 12 made of paper.

After the trimerisation or curing of the resin 10, the finished tubular hollow bodies 12 are placed in the desired number and arrangement into a sealable mould with a mould cavity corresponding to the shape and dimensions of the lightweight construction elements 2, so that the open ends of the chambers 6 at the opposite end faces of the hollow bodies 12 are closed by walls of the mould. After this, the interstices or spandrels 20 between the adjacent hollow bodies 12 are filled with the hard foam 18, which consists of a PIR foam and is cured in the mould.

In order to avoid any air being trapped between the foam and the hollow bodies 12 when the fluid foam is introduced into the mould, it is preferable to arrange adjacent hollow bodies 12 at a distance from each other, as shown in Fig. 7 and 8, so that the fluid foam can be introduced into the mould at one side of the lightweight construction elements 2 and from here it can fill up the entire mould cavity through the gaps between the adjacent hollow bodies 12. After the curing, the hard foam 18 ensures a solid connection between the hollow bodies 12 embedded in it.

The lightweight wall elements 2 in Figures 1, 2, 5, 6, 7 and 8 are not provided with one or two additional top layers at their two opposite broad sides 22, so that they substantially consist of only the tubular hollow bodies 12 and the hard foam 18 which fills up the interstices or spandrels 20 between the outer circumference 14 of the adjacent hollow bodies 12 and in this case also forms the surfaces of the two broad sides 22 of the lightweight construction elements 2. A so-called integral foam can be used advantageously as the hard foam here, in which the hardness of the cured foam increases in the direction of the surfaces of the broad sides 22.

The lightweight construction elements 2 in Figures 1 and 2 as well as 7 and 8, each having a single row of cylindrical tubular hollow bodies 12 with an outer diameter of 50 mm, possess a weight per unit area of less than 3 kg/m2 and preferably less than 2 kg/m2. Best of all, the weight per unit area of these lightweight construction elements 2 is around 1.5 to 2 kg/cm2, while the weight per unit area of the untreated paper is 0.45 to 0.55 kg/m2, the weight per unit area of the resin 10 used for the coating is 0.55 to 0.60 kg/m2, and the weight per unit area of the hard foam 18 is 0.55 to 0.65 kg/m2, so that these three components therefore provide around a third of the weight per unit area.

On the other hand, the surfaces of the opposite broad sides 22 of the lightweight wall elements 12 in Fig. 3 and 4 and the outer circumference 26 of the lightweight support element 2 in Fig. 3 are formed by a top coat 28 of a fibre-reinforced resin, parallel to the broad sides, which is applied for the stiffening of the wall elements 12. This resin may be polyurethane, for example, in which a fabric or laying of glass fibres, synthetic fibres or carbon fibres is embedded. Alternatively or additionally, however, top layers of other materials can also be used, such as mineral fibre cover sheets, which consist of a mixture of magnesium oxide and magnesium chloride reinforced with glass fibres, resting by their inner surfaces against the adjacent row of hollow bodies 12 and glued by the hard foam 18 to the tubular hollow bodies 12. Optionally, the top coat or top layers may also be joined by screws to the core of the lightweight construction elements 2 composed of the hollow bodies 12 and the hard foam 18.

The hard foam 18 is a PIR foam, that is, polyurethane foam which is cross-linked more than the typical PUR foam and thus being shape-stable even at higher temperatures. Thanks to the shape stability and the relatively small pore dimensions of less than 1 mm, the hard foam 18 can be shaped into a groove 30 and a tongue 32 on the two opposite vertical narrow sides of each wall element 2 during the fabrication of the lightweight wall elements 2 in Figures 1 to 8, so that adjacent wall elements 2 can be connected together by means of a tongue and groove joint 30, 32.

In order to close the openings of the tubular hollow bodies 12 at the upper and lower end of the lightweight wall elements 2 and provide a flat termination, the lightweight wall elements 2 are each provided with a finishing strip 34 at their upper and lower end. As is best shown in Fig. 9 and 10, the finishing strip 34 has a flat broad side 36 facing away from the ends of the hollow bodies 12. Along the opposite broad side 38 facing toward the ends of the hollow bodies 12 stands a row of cylindrical protrusions 40, whose outer diameter is slightly less than the inner diameter of the tubular hollow bodies 12, so that they can be introduced into the open ends of the chambers 6 at the end faces of the hollow bodies 12 and thereby improve the cohesion of the hollow bodies 12 at the upper and lower end. In order to facilitate the introducing of the protrusions 40 into the opposite openings, the free ends of the protrusions 40 are tapered or bevelled. The finishing strips 34 have a length and width corresponding to the length and width of the lightweight wall elements 2 and can be put in place during the fabrication of the lightweight wall elements 2 or during their installation. In the latter case, the strips 34 can be placed at the joints of adjacent lightweight wall elements 2, set off from the tongue and groove joints 30, 32, so that they bridge over the joints.

It has been found by experimentation that lightweight wall elements 2 with a height of 980 mm, a width of 250 mm and a thickness of 56 mm, consisting of a row of cylindrical tubular hollow bodies 12, which are coated on their inner and outer circumferential surfaces 14, 16 with an epoxy or polyisocyanurate reaction resin 10, as well as two top layers 28 of mineral fibre cover sheets with a thickness of 3 mm on both broad sides and a filling of PIR hard foam 18 in the interstices or spandrels 20 between the tubular hollow bodies 12 and the top layers 28, as per Fig. 4, can sustain a compressive loading of more than 2.5 t in the direction of the longitudinal central axes 8 of the hollow bodies 12 before the wall elements 10 break. In bending tests with the same lightweight wall elements 2, but with a PUR hard foam 18 in the interstices 20 between the hollow bodies 12, it was found that the wall elements 2 withstand a sideways compressive loading of 0.4 t, applied at two spaced-apart places in one of the broad sides 22, before a bending fracture occurs in the lightweight construction elements 2.

The high load bearing ability of the lightweight construction elements 2 in the direction of the longitudinal central axes 8 of the tubular hollow bodies 12 is achieved by the coating of the outer and inner circumferential surfaces 14 and 16 of the hollow bodies 12 with the resin 10, which after becoming crosslinked and cured increases the compressive strength of the hollow bodies 12 in the direction of their longitudinal central axes 8 by a multiple. In the lightweight construction elements 2 shown in Figures 11 to 13 in cross section, the multichamber hollow profile 4 consists not of one or more rows of individual, interconnected hollow bodies 12, but rather of two or more sheets 42 lying against each other and joined together, each of them having a cross section in the shape of a sine wave with alternating protrusions in the form of wave peaks 44 and depressions in the form of wave valleys 46. The wave peaks 44 and the wave valleys 46 of adjacent sheets 42 are set off from each other by a half-wave, so that each time the wave peaks 44 and the wave valleys 46 of the two sheets 42 face each other, and each time opposite wave peaks 44 lie against each other by their vertices 50 and are glued to each other at the vertices 50. In this way, a row of chambers 6 arranged alongside each other is formed between two adjacent sheets 42, having the same cross sections, which remain constant in the direction of the longitudinal axes of the chambers 6. The adjacent chambers 6 are separated from each other by the bonding 50 at the vertices 50. The sheets 42, like the hollow profiles 6, consist of one or more paper layers and are provided with a coating of the resin 10 on their inner surfaces 52 facing toward the chambers 6 and on their outer surfaces 54 facing away from the chambers 6, as previously described for the hollow bodies 12. The resin 10 used for the coating is the same as described before. The wall thicknesses of the sheets 42 and the ratio of the cross section dimensions of the chambers 6 to the wall thickness of the sheets 42 forming the boundary walls of the chambers 6 are similar to those described above for the hollow bodies 12.

The lightweight construction elements 2 in Figures 11 to 13 are wall elements. The wall element 2 in Fig. 11, like the wall element 2 in Fig. 3 and 4, is provided with two flat top layers 28 in the form of thin mineral fibre boards or a fibre-reinforced resin, lying against the vertices 56 of the wave peaks 46 and being glued firmly between them with hard foam 18 to the multichamber hollow profile 4, the hard foam 18 filling the spandrels 20 between the outer surfaces 54 of the sheets 42 facing away from the chambers 6 and the top layers 28.

While the multichamber hollow profile 4 of the wall element 2 in Fig. 11 consists of two sheets 4 lying on top of one another, the multichamber hollow profile 4 of the wall element 2 in Fig. 12 and 13 consists of a total of four sheets 42 with corrugated cross section, placed on top of one another and bounding off between them three rows of chambers 6. The chambers 6 of adjacent rows are set off from each other in the sideways direction by half the chamber width, so that only chambers 6 are formed between the sheets 42, but no spandrels 20 filled with hard foam 18. The inner sheets 42 lie with the vertices 50 of their wave peaks 44 against one of the two neighbouring sheets 42 and with the vertices 56 of the wave valleys 46 against the other neighbouring sheet 42 and are glued there to the neighbouring sheets 42. The hard foam 18 fills the spandrels 20 between the outer surfaces 54 of the outermost sheets 42, facing away from the chambers 6, and forms the surfaces of the two broad sides 22 of the wall element 2.

The lightweight construction element 2 shown in Fig. 15 and 16 in the form of a sheetlike ceiling or floor element consists of multiple short tubular hollow bodies 12, which are embedded in the hard foam 18 (only shown in Fig. 15). The hollow bodies 12 are vertically oriented and each time lie with their outer circumference 14 against the outer circumference 14 of adjacent hollow bodies 12, to which they are once again bonded by the hard foam 18 in the interstices or spandrels 20. Here, however, it is also possible to leave out the hard foam 18 and to join together the adjacent hollow bodies 18 with the aid of the resin coating 10 to the outer circumferential surface 16 of the hollow bodies 12. The hollow bodies 12 each have the same length and are braced by their opposite flush end faces against parallel flat sheetlike top layers 28, which close the openings of the hollow bodies 12 at the top and bottom of the sheetlike ceiling or floor element 2 and furthermore increase its bending stiffness, especially if the end faces of the hollow bodies 12 are bonded by the hard foam 18 to the inside of the adjacent top layers 28. The top layers 28 may consist of any suitable material. On the narrow sides of the lightweight construction elements 2 once again there are provided grooves (not shown) and tongues 32, so that adjacent elements 2 can be connected to each other by tongue and groove joints 30, 32.

Fig. 17 shows a cross section through a portion of another lightweight construction element 2 in the form of a sheetlike ceiling or floor element, in which the open ends of the chambers 6 are closed not by sheetlike top layers 28, but instead by coats 60 of a fibre-reinforced synthetic resin 62. For this purpose, the hollow bodies 12 as in the case of the ceiling or floor element 2 in Fig. 15 are arranged in a dense array of rows set off from one another, in which each hollow body 12 rests by its outer circumferential surface 14 against the outer circumferential surfaces 14 of six neighbouring hollow bodies 12. The mutually touching hollow bodies 12 are then bonded together by means of the coating consisting of the resin 10 at the outer circumferential surfaces 14 to form a rigid honeycomb structure, for example by adding heat in an oven. After this, the upper and the lower ends of the chambers 6 are closed at the broad sides of the honeycomb structure by one or more coats 60 of the fibre-reinforced synthetic resin 62, whereby a fleece 64, fabric or laying of synthetic resin, glass or carbon fibres is placed on the respective upturned broad side of the honeycomb structure so that it completely covers the open ends of the chambers 6. The fleece 64, fabric or laying is then impregnated with the curable synthetic resin 62, which is poured in a thin coat onto the top side of the fleece 64, fabric or laying, and penetrates through the fleece 64, fabric or laying to the ends of the hollow bodies 12, to which it adheres upon hardening. After the hardening of the resin 62, the two ends of all hollow bodies 12 forming the boundary walls of the chambers 6 of the multichamber hollow profile 4 are firmly bonded to the fibre-reinforced resin 60 and form a lightweight construction element 2 with high bending stiffness.

In all instances, the tubular chambers 6 surrounded by the multichamber hollow profile 4 may either be empty or they may contain a thermal insulating or sound-deadening material, such as a polystyrene granulate 56, paper flakes, or sand, as is shown for example in a portion of the chambers 6 in Fig. 11. In the lightweight construction element in Fig. 9, the chambers are filled with the hard foam 18.

Claims

Sustainable or load-bearing lightweight element (2) with one or more rows of parallel chambers (6), each surrounded by tubular boundary walls, wherein said restriction walls are at least partially made of paper, wherein said boundary walls of adjacent chambers (6) are connected forming a multi-chamber hollow profile (4) which has a constant cross-section (8) in the direction of the longitudinal center axes (8) of the chambers (6), with the inner surfaces (52) facing the chambers (6) and the faces facing away from the chambers (6) outer surfaces of the restriction walls are provided with a coating (10) and / or water-repellent and increase the bending and / or pressure resistance of the paper, the multi-chamber hollow profile (4) comprising one or more rows of cylindrical hollow bodies (12), each of the cylindrical hollow bodies (12) limits one of the chambers (6), and the chambers (6), like the spaces or wedges (20) between the adjacent hollow bodies (12), are filled with a hard foam (18). ) which interconnect the boundary walls of the adjacent chambers (6), characterized in that the hard foam (18) is one, two or more components of curing reaction foam, more specifically a higher crosslinked hard polyurethane foam, and that the individual pores of the hard foam are very small and have cross-sectional dimensions of less than 0.5 mm.

Lightweight element according to claim 1, characterized in that the hard foam (18) is applied to at least one outer surface of the multi-chamber hollow profile (4) facing away from the chambers (6).

Lightweight element according to claim 1 or 2, characterized in that the limiting walls consist of less than four interlaced paper layers and have a wall thickness of less than 2 mm.

Lightweight element according to one of the preceding claims, characterized in that the coating and / or impregnation consists of a liquid state applied to the surfaces and then cross-linked duroplastic resin (10) or synthetic resin.

Lightweight element according to claim 4, characterized in that the coating and / or impregnation consists of a poly or epoxy isocyanurate resin.

Lightweight element according to one of the preceding claims, characterized in that the multi-chamber hollow profile (4) comprises one or more rows of adjacent tubular hollow bodies (12), which with their outer circumference (14) abut the outer perimeter (14) of adjacent tubular hollow bodies (12) and is bonded to the adjacent hollow bodies (12) by the coating and / or hard foam (18).

Lightweight element according to one of the preceding claims, characterized in that the multi-chamber hollow profile (4) extends throughout the entire height of the lightweight element (10).

Lightweight element according to any one of the preceding claims, characterized in that the ratio of the cross-sectional dimensions of the chambers (6) to the wall thickness of the restriction walls (12, 42) is greater than 25: 1 and preferably greater than 50: 1 and is best approx. 100: 1.

Lightweight element according to one of claims 2 to 8, characterized in that the hard foam (18) forms at least one surface (22) of the lightweight element (10).

Lightweight element according to one of claims 2 to 9, characterized by an additional cover layer (28).

Lightweight element according to one of claims 2 to 10, characterized in that a groove (30) and a spring (32) formed on two opposite narrow sides formed in the hard foam (18) or milled by the hard foam (18) .

Lightweight element according to one of the preceding claims, in the form of a floor or ceiling plate, characterized in that the multi-chamber hollow profile (4) consists of a plurality of short tubular hollow bodies (12), the opposite open ends of which each define a flat surface. and is closed by at least one layer (60) of a fiber-reinforced resin (62, 64) adhered to the ends (12) of the hollow bodies.

Freight or housing container with a floor, side walls and a ceiling, characterized in that the floor and / or at least part of the side walls and / or ceiling consists of lightweight elements (2) according to one of the preceding claims.

Railroad or truck structure with a floor, side walls and a ceiling, characterized in that the floor and / or at least part of the side walls and / or ceiling consists of lightweight elements (2) according to one of claims 1 to 12.