EP2991822B1 - Method for making ductile honeycomb cores - Google Patents

Description

The invention relates to a method for the production of moldable honeycomb cores according to the preamble of claim 1.

Plate-shaped sandwich composites usually consist of two cover layers, which are shear-resistant connected with a light core layer. Based on this structure, advantageous mechanical properties of the composite result with comparably low weight.

Cores for sandwich composites, especially cores having a void structure (e.g., honeycomb structure) typically have a significantly lower density than the liners.

A variant of a core with a cavity structure are hexagonal honeycomb cores. For the first time, such a structure has been described in the patent document DRP 133165. Today, hexagonal honeycomb cores are produced as unexpanded paper honeycomb cores for the field of furniture and interior design as well as for related areas and are only expanded immediately prior to the production of the sandwich panels, which entails the advantage of a very low transport volume. Among other things, sandwich panels with such cores enable high specific compressive strengths across the board plane, an enormous weight saving and a reduced consumption of raw materials.

Conventional hexagonal honeycomb cores consist of a honeycomb-like, hexagonal structure, which is formed by the gluing of paper strips k of defined thickness s and subsequent expansion, expansion. The direction of production X is the direction in which it is expanded. A three-dimensional view of a clipping is going in Fig.2 and a single cut out cell as a top view Fig. 3 shown.

The regions of the bond are referred to as double webs a1 and the non-bonded regions as simple webs a2. With most production plants a variety of core heights h can be produced.

Due to their structure, conventional expanded honeycomb cores are strong in theirs Moldability limited. In the case of two-dimensional forming, there is usually the problem of so-called saddle formation. A production of any two- and three-dimensionally shaped sandwich components with expandable honeycomb core has previously been possible only by the destruction of the core structure in the areas of heavy forming. With very thin components, the uncontrollable buckling or tearing of webs of the honeycomb structure is sometimes deliberately accepted.

There are already different three-dimensionally formable honeycomb cores. Such a honeycomb core is for example from the EP 0 955109 A2 known. Such structures are complex in their production and also do not offer the possibility of transport to the final processor in the unexpanded state. Thus, such three-dimensionally deformable cores are expensive and are used only for a few applications. They consist, for example, of aramid fiber paper, which is impregnated with resin after being formed, or of aluminum.

In the publication DE 10 2009 005 869 A1 describes an expandable honeycomb core that is shapeable in the transverse and longitudinal directions without damage to the structure and thus allows a three-dimensional shaping of sandwich components without affecting the honeycomb core (3-d expansion honeycomb). A three-dimensional view of a clipping is going in Figure 4 and a single cut out cell as a top view Fig. 5 shown. Similar to the conventional expandable honeycomb cores, the 3-d expansion honeycomb consists of individual web layers / folded paper strips of thickness s, which are connected to one another by alternately following double webs b1 and simple webs b2, so that upon expansion a honeycomb-like structure is formed. The connection is made by the strip sections are glued together in the region of the double webs. According to the invention, the simple webs b2 of the 3-d expansion honeycomb additionally have predetermined bending lines which divide the simple webs into three regions b2.1, b2.2, b2.3. This structure allows the defined folding of the honeycomb core formed in the transverse and / or longitudinal direction and at the same time increases the compressive strength of the sandwich composite. In addition to the three-dimensional shaping, it is also possible to produce one-dimensional and two-dimensional sandwich composites. In addition to paper as starting material for the 3-d expansion honeycomb other raw materials such as aramid fiber paper with subsequent impregnation of resin or aluminum can be used. The 3-d expansion honeycomb can be manufactured in any desired core heights h.

Components with conventional honeycomb cores have significantly reduced strength values due to the buckling or tearing of webs in the case of two- or three-dimensional deformation on. Therefore, such honeycomb cores are rarely used for two-dimensionally or three-dimensionally shaped components. A variant of the application is the use of petroleum-based foams (eg polyurethane foams) as the core layer of three-dimensional sandwich elements, which in some cases is also combined with the use of conventional honeycomb cores. However, the production of such a sandwich composite is relatively expensive and disadvantageous for later recycling.

Sandwich composites of the type discussed here can be implemented as a one-dimensional plate as well as a two-dimensional or three-dimensionally shaped component. Specifically two- and three-dimensionally shaped components are increasingly used in industries such as aircraft, automotive, caravan construction, ship and boat building, but also in furniture and exhibition construction and in immobile interior design. The cover layers usually consist of correspondingly deformable materials such as plastic, metal, wood and wood-based material or (natural) fibers.

Already existing in shape three-dimensional honeycomb cores are already available, but these are very expensive, so that they are used only in a few applications. In addition, due to the already existing expanded form, comparably high storage and transport costs follow. Low-cost three-dimensionally shaped sandwich components with expandable honeycomb core can not be produced because of the lack of an industrially producible deformable core layer.

The US 2012 / 0205035A1 describes a method for producing a honeycomb core. In this case, a planar web is moved by a pair of rollers that converts the web into a ribbed web. The ribbed web has flat valley sections and also flat cover sections, which are connected to one another by connecting sections of the web. The ribbed web is cut and folded to obtain the desired honeycomb core. Subsequently, this can be provided with a cover and a base.

That in the patent ( DE 10 2009 005 869 A1 ) presented method for producing the 3-d expansion honeycomb provides, the predetermined bending lines in the areas of the free webs by folding, embossing o. The like. To introduce. In the practical implementation shows that a purposeful buckling machine-made honeycomb cores in the protected manner is technically extremely complicated to implement.

Object of the invention

The object of the present invention is to provide an industrially applicable method for producing the 3-d expansion honeycomb with improved technology.

In the method sheet or sheet-shaped flat product, consisting mostly of paper, alternatively, from other starting materials such as aramid fiber paper with subsequent resin impregnation or aluminum processed. In addition, connecting elements or means for joining the individual web layers / folded paper strips, such as e.g. Adhesive used.

The complex transformation required for the production of the 3-d expansion honeycomb is achieved in several successive substeps. The possibly present fiber orientation of the material to be processed as well as the deflections and fold lines introduced during processing lie parallel to the machine direction of rotation (MLR).

• 1.1 Umformen eines flachen , bogen- bzw. bahnförmigen Verarbeitungsgutes, dem Rohbogen bzw. der Rohbahn, zu einem mäanderförmigen Gebilde mit im Wesentlichen horizontalen und vertikalen Flächen,
• 1.2 Einbringen eines Faltmusters in die vertikalen Flächen des mäanderförmigen Gebildes durch Längsfalzen entlang der Maschinenlaufrichtung, wobei die horizontalen Flächen um einen Teil der zuvor vertikalen Flächen vergrößert werden und die restlichen vorherigen vertikalen Flächen im Zickzack-Muster umgeformt werden,
• 1.3 Komprimieren des eingebrachten Musters zum Falzbogen, bzw. zur Falzbahn,
• 1.4 Weiterverarbeiten des Falzbogens, bzw. der Falzbahn zur 3-d-Expansionswabe

The process according to the invention for producing the 3-d expansion honeycomb is carried out by the following steps:

• 1.1 forming a flat, sheet-like or sheet-like material to be processed, the raw sheet or the raw sheet, to a meander-shaped structure with substantially horizontal and vertical surfaces,
• 1.2 inserting a folding pattern into the vertical surfaces of the meander-shaped structure by longitudinal folding along the machine direction, wherein the horizontal surfaces are increased by a part of the previously vertical surfaces and the remaining previous vertical surfaces are formed in a zigzag pattern,
• 1.3 compressing the introduced pattern to the folded sheet, or to the folding path,
• 1.4 Further processing of the signature, or the folding path to the 3-D expansion honeycomb

In an advantageous variant of the method, the folded sheet or the fold path is alternately cut from above and below at a distance of the later core height h to the whereabouts of only one paper thickness transverse to the machine direction and the coherent blocks thus formed by folding around the remaining processing material and the 3rd -d expansion honeycomb pressed. The application of adhesive can take place before or after the cutting.

In a further advantageous variant of the method, webs / folded paper strips are separated from the folding sheet or the folding web transversely to the machine direction and lined up by pressing them about the longitudinal axis in the correct position to form double webs of the 3-d expansion honeycomb and compressed. The application of adhesive can take place before or after the separation. The distance between the two cuts gives the core height h.

In a further advantageous variant of the method, a plurality of folded sheets or folding webs are adhesively bonded to one another in the correct position to form double webs. The processing takes place further in that at the same time several, already bonded web layers / folded paper strips are separated transversely to the machine direction and these aligned in the same direction to form double webs of the 3-d expansion honeycomb and pressed to the 3-d expansion honeycomb. The second application of adhesive may take place before or after the separation of the already glued folded sheets or folding paths. The distance between the two cuts gives the core height h.

In a further advantageous variant of the method, a plurality of signatures or folds are glued together in the correct position assignment to form double webs. From the resulting block, the 3-d expansion honeycomb in any core height h is separated.

Advantageously, the meander-shaped structure is formed with substantially horizontal and vertical surfaces in a pronounced Zinnenfriesform or with larger radii at the transitions, to a complete curvature of the horizontal sections.

Further advantageous is the introduction of a folding pattern in the vertical surfaces of the meander-shaped structure in zig-zag shape by the action of corresponding web guiding elements, designed as a mold rail arrangement, achieved during the advance of the sheet or the web.

Advantageously, the mold rails are designed in such a way that all required deflections of the folded sheet or the fold web are introduced into the processed good by multiple, parallel longitudinal folding. The mold rails can be correspondingly shaped individual parts or assemblies with correspondingly shaped individual elements. A form of rail is characterized in that it introduces the required deflections in the processed material during conveyance through the mold rail assembly. For this vertical elevations of the form rail of the meandering shape along the Increase the rail to the folded sheet or to the folding path and reduce the height of the rail, so that the deformation can take place without unwanted mechanical impairment of the processed material. Vertical indentations of the mold rail, which increase along the mold rail, provide the space needed for the forming.

Further advantageously, for the conveyance of the material to be processed and for the deformation of the deflections to form sharp folding lines Zugwalzenpaare find application.

Further advantageously, individual mold rails can be moved relative to the rest to reduce the required conveying forces. Likewise, by supplying compressed air, a flow around the mold rails with air and thus a reduction of the conveying forces can be achieved. But it can also find other lubricants application.

Fig. 1

einen möglichen Verfahrensablauf,

Fig. 2

eine dreidimensionale Sicht auf einen Ausschnitt eines herkömmlichen Hexagonalwabenkerns,

Fig. 3

eine Draufsicht auf eine Zelle eines herkömmlichen Hexagonalwabenkerns,

Fig. 4

eine dreidimensionale Sicht auf einen Ausschnitt der 3-d-Expansionswabe,

Fig. 5

eine Draufsicht auf eine Zelle der 3-d-Expansionswabe,

Fig. 6

eine dreidimensionale Sicht auf einen Ausschnitt auf das Ergebnis des ersten Umformvorganges, eine Mäanderform,

Fig. 7

eine dreidimensionale Sicht auf einen Ausschnitt des zweiten Umformvorganges, welcher die Mäanderform in einen Falzbogen bzw. eine Falzbahn überführt,

Fig. 8

eine dreidimensionale Sicht auf einen Ausschnitt des Ergebnisses des zweiten Umformvorganges, welches den Ausgangszustand für mehrere Möglichkeiten der Weiterverarbeitung zur 3-d-Expansionswabe darstellt,

Fig. 9

eine dreidimensionale Sicht auf einen Ausschnitt des Ergebnisses eines leicht abgewandelten ersten Umformvorganges, mit veränderter Mäanderform,

Fig. 10

eine Seitenansicht einer möglichen Weiterverarbeitung, bei der der Falzbogen bzw. die Falzbahn wechselnd von oben und unten eingeschnitten und danach zur 3-d-Expansionswabe umgeformt wird,

Fig. 11

eine dreidimensionale Sicht auf eine mögliche Weiterverarbeitung bei der der Falzbogen bzw. die Falzbahn in Abschnitte geteilt wird, welche wiederum entsprechend mit Klebstoff beaufschlagt werden und entsprechend angeordnet die 3-d-Expansionswabe bilden,

Fig. 12

eine dreidimensionale Sicht auf eine mögliche Weiterverarbeitung bei der der Falzbogen bzw. die Falzbahn, mehrfach mittels Klebstoff zusammengefügt wird, in Abschnitte getrennt wird und diese abschließend mit Klebstoff zur 3-d-Expansionswabe zusammen gefügt werden,

Fig. 13

eine dreidimensionale Sicht auf eine mögliche Weiterverarbeitung bei der der Falzbogen bzw. die Falzbahn, vielfach mittels Klebstoff zu einem Block zusammengefügt werden, von dem die 3D-Expansionswabe in gewünschter Kernhöhe abgetrennt wird.

The invention will be explained in more detail below with reference to exemplary embodiments. In the accompanying schematic representations show:

Fig. 1

a possible procedure,

Fig. 2

a three-dimensional view of a section of a conventional hexagonal honeycomb core,

Fig. 3

a plan view of a cell of a conventional hexagonal honeycomb core,

Fig. 4

a three-dimensional view of a section of the 3-d expansion honeycomb,

Fig. 5

a top view of a cell of the 3-d expansion honeycomb,

Fig. 6

a three-dimensional view of a section on the result of the first forming process, a meandering shape,

Fig. 7

a three-dimensional view of a section of the second forming process, which converts the meandering shape into a folded sheet or a fold sheet,

Fig. 8

a three-dimensional view of a section of the result of the second forming process, which represents the initial state for several possibilities of further processing to the 3-d expansion honeycomb,

Fig. 9

a three-dimensional view of a section of the result of a slightly modified first forming process, with modified meandering shape,

Fig. 10

a side view of a possible further processing in which the folded sheet or the Falzbahn be alternately cut from above and below and then converted to 3-d expansion honeycomb,

Fig. 11

a three-dimensional view of a possible further processing in which the folded sheet or the folding path is divided into sections, which in turn are applied accordingly with adhesive and arranged according to the Form 3-d expansion honeycomb,

Fig. 12

a three-dimensional view of a possible further processing in which the folded sheet or the fold sheet, is repeatedly joined together by means of adhesive, is separated into sections and these are finally joined together with adhesive to the 3-d expansion honeycomb,

Fig. 13

a three-dimensional view of a possible further processing in which the folded sheet or the fold path, are often joined together by means of adhesive to a block from which the 3D expansion honeycomb is separated at the desired core height.

The respective conveying or machine running directions of the method are marked with arrows.

A basic procedure of the method according to the invention is in the Fig.1 shown.

In the first step, a flat, bow-shaped or web-shaped processing material is conveyed into or through a die. The resulting shape consists of alternating vertically and horizontally contiguous surfaces. Transverse to the machine direction Y thus creates a meandering, in the example Fig. 6 a pinnacle frieze shape. However, the result of this first parting process can also be a cross section that is slightly different from the Zinnenfries form. Thus, the deflections between vertical 5 and horizontal surfaces 4 can also be performed with a larger radius. In extreme cases, up to the complete curvature of the horizontal surfaces, Fig. 9 ,

By this first step, the required for further processing web or sheet width reduction and thus a targeted concentration of the processed material is achieved. In the process flow Fig. 1 the result of this first transformation is shown to the left of section 1.1.

In the following step, between section 1.1 and 1.2, the existing meandering shape is further formed by Längsfalzen to the folded sheet or Falzbahn. For this forming step special tools, mold rails are necessary, which bring in all the required fold lines during conveying of the processing material by a multiple, parallel Längsfalzen. During forming, the horizontal surfaces 4, Figure 7 extended to a part of the previously vertical surfaces 5a. The remaining area is formed in a zigzag pattern 5b, c, d. A section of the processed material during the Forming provides Fig. 7 It is not absolutely necessary that the bending lines be introduced with sharp-edged tools. The tools may, for example, also be designed so that the edges required for the forming are designed with a radius 5r decreasing along the tool.

After forming, the resulting folding pattern is compressed by means of suitable aids, such as a roller pair, whereby the fold lines are finally formed on the deflections, Fig. 8 , In the process, Fig. 1 , this form exists between section 1.2 and 1.3. The introduced fold lines act in the later honeycomb core like hinges between the surfaces. The enlarged horizontal surfaces 4 + 5a, Figure 8 form the double webs b1 in the expanded state of the 3-d expansion honeycomb, Figure 4 and the zigzag folded surfaces 5b, c, d, Figure 8 the simple webs b2.1, b2.2, b2.3, Figure 4 , As a result, in cross-section to the MLR, a kind of constantly changing ornament emerges from one long and three shorter lines. The lines are connected via deflections, transferred to the room these are the fold lines. Vertically, the pattern can be mirrored by half of the long lines, as exemplified in Fig. 8 is illustrated with the mirror image plane 5s and the sections a and a '.

For the further processing of the folding sheet or the folding path to the 3-D expansion honeycomb there are several possible embodiments. One is in Fig.1 exemplified with. A side view of this process is in Fig. 10 shown. It is the folded material to be processed in the area of the later double webs first adhesive on one side. This is done between section 1.2 and 1.3. Next, the folding pattern is cut to the last layer of the processed material and hinged around 180 °. The previously applied adhesive layer on the double webs causes the material connection of the individual hitherto only hinge-like sections to the 3-d expansion honeycomb.

Another way to make the 3-expansion honeycomb from the fold sheet or the fold path is to separate strips from the folding pattern, apply these before or after the separation with adhesive and handle the individual folding pattern strips so that they glued and accordingly compressed form the 3-d expansion honeycomb, Fig. 11 , In this case, the folding pattern can be previously glued together already in several versions Fig. 12 ,

It is also possible to glue together a multiplicity of folded sheets or folding trays, to compress them and finally to separate the 3-d expansion honeycombs from the resulting block in the desired core height, Fig. 13 ,

Finally, the unexpanded honeycomb core can be expanded in two directions to the 3-d expansion honeycomb. In order to reduce storage and transport costs, the expansion can be temporally and spatially offset, similar to the expansion of conventional hexagonal honeycomb cores, carried out only at the user.

Another way to inexpensively transport and store the 3-d expansion honeycomb is to fully expand the 3-d expansion honeycomb already in the manufacturing process and repress the machine direction in just one dimension. In this form, the 3D expansion honeycomb is transported and stored in a space-saving and cost-effective manner. The advantage of this design is that expanders for conventional honeycomb cores can also be used to expand the 3D expansion honeycomb and so the user does not need to provide new machine technology.

Depending on the design, the presented method for producing the 3d expansion honeycomb can work continuously or discontinuously. Depending on the method of operation, sheets or webs can be processed.

Claims (7)

1. A method for making ductile honeycomb cores by

   1.1 forming a flat sheet-type or web-type material to be processed into a meander-shaped structure with surfaces that essentially extend horizontally (4) and vertically (5),

   1.2 further processing into a 3-d expansion honeycomb,

   characterized by the following additional steps:

   1.3 producing a folding pattern in the vertical surfaces (5) of the meander-shaped structure by longitudinal folding along the machine running direction, wherein the horizontal surfaces (4) are enlarged by a section (5a) of the previously vertical surfaces (5) and the remaining previously vertical surfaces (5) are shaped into a zigzag pattern (5b, c, d),

   1.4 producing sharp-edged folding lines in order to respectively form a folded sheet or folded web.
2. The method according to claim 1, characterized in that the respective folded sheet or folded web is alternately cut from above and below transverse to the machine running direction in the interval of the subsequent core height until only a paper thickness remains, wherein the thusly formed connected blocks are positioned upright by being respectively folded over relative to the remaining material to be processed and pressed together into a 3-d expansion honeycomb, wherein the cohesion is realized with an adhesive applied prior or subsequent to the separation.
3. The method according to claim 1, characterized in that web layers/folded paper strips are separated from the respective folded sheet or folded web transverse to the machine running direction, as well as correspondingly turned about the longitudinal axis in order to be strung and pressed together in the correct position for forming double webs (b1) of the 3-d expansion honeycomb, wherein the application of adhesive may take place prior or subsequent to the separation.
4. The method according to claim 1, characterized in that web layers/folded paper strips are separated from several adhesively connected folded sheet or folded webs transverse to the machine running direction, wherein these web layers/folded paper strips are provided with adhesive prior or subsequent to the separation and subsequently joined in the correct position for forming double webs (b1) of the 3-d expansion honeycomb.
5. The method according to claim 1, characterized in that a plurality of folded sheets or folded webs is glued together in the correctly positioned allocation for forming double webs (b1) and the 3-d expansion honeycombs are separated from the thusly formed block.
6. The method according to one of claims 1-5, characterized in that the meander-shaped structure, which has surfaces that essentially extend horizontally (4) and vertically (5), is realized with a distinct crenellated frieze shape or with a curvature in the horizontal section.
7. The method according to one of claims 1-6, characterized in that the folding pattern is produced in the surfaces of the meander-shaped structure under the influence of corresponding web guiding elements during the advance of the respective sheet or web.

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