Themoformable panel

Abstract

A thermoformable panel for shelves includes at least one core plate having honeycomb structure consisting of a plurality of contiguous cells; a coating layer, or optionally two or more coating layers, having at least one thermoplastic material coupled to the core plate on at least one face of said core plate. Further includes are stiffening elements provided as at least one or more metal strips and/or braided plastic material such as straps, spread over the surface extension of at least one face of the honeycomb core, the metal strip or strips being restrained against or inside the honeycomb core with the at least one coating layer coupled by physical chemical adhesion against the at least one face of the honeycomb core.

Claims

1. A thermoformable panel comprising: at least one core plate having honeycomb structure with cells having axes arranged substantially parallel to each other and oriented substantially perpendicularly to faces of said core plate; at least one coating layer coupled to said core plate on at least one face of said core plate, wherein the at least one coating layer comprises a film or skin of a thermoplastic material coupled to the at least one core plate by chemical/physical coupling; and one or more stiffening elements comprising at least one or more strips made from metal or plastic, wherein the one or more strips are spread on a surface extension of the at least one face of said panel, to which said at least one coating layer is coupled, and wherein the one or more strips are restrained so as to be locked in the panel structure due to at least one coating layer of the panel.

2. The thermoformable panel according to claim 1, wherein the coating layer consists of a thermoplastic skin or film high-temperature coupled to a nonwoven fabric so that a ratio of film weight to nonwoven weight prevents a cold flow of the fibers while the finished panel is under stress.

3. The thermoformable panel according to claim 1, wherein the one or more strips are made from plastic and are shaped as a strap-type or the like.

4. The thermoformable panel according to claim 1, wherein the strips are one or more spread on the surface extension of the at least one face of said honeycomb core, to which the at least one coating layer is coupled, the one or more strips being restrained to be locked to the honeycomb core by said at least one coating layer coupled by chemical-physical adhesion against the at least one face of the honeycomb core.

5. The thermoformable panel according to claim 1, wherein the one or more strips are at least partially embedded in a thickness of the honeycomb core.

6. The thermoformable panel according to claim 5, wherein at least some or all of the strips are embedded in housings shaped as accommodating cut-outs or slits obtained in the thickness of the honeycomb core at least partially along a width of said strips.

7. The thermoformable panel according to claim 5, wherein at least some or all the strips are embedded, substantially along their entire width, in corresponding housings obtained in the thickness of the honeycomb core.

8. The thermoformable panel according to claim 5, wherein at least some of the housings or all housings are oriented substantially perpendicular to at least one face of the honeycomb core and at least part of at least some of the strips are positioned sideways or edgewise, that is, perpendicularly to said at least one face of the honeycomb core.

9. The thermoformable panel according to claim 4, in which the housings and the strips extend to almost the entire thickness of the honeycomb core and end at a distance from the face opposite to the face where the strips are inserted, without passing through the honeycomb core from one side thereof to the other.

10. The thermoformable panel according to claim 4, wherein the strips have an angled, preferably L-shaped, cross-section.

11. The thermoformable panel according to claim 1, wherein the coating layer comprises additional strips of reinforcing material which extend each along an extension of a corresponding metal strip and which, when coupled, are incorporated into a thickness of the coating layer, at least partially merging therewith.

12. The thermoformable panel according to claim 11, wherein said reinforcing strips are applied in a position between the honeycomb core and the coating layer and coincident with a corresponding metal stiffening strip, or on an outer face of the coating layer still in a position coincident with a corresponding strip.

13. The thermoformable panel according to claim 1, wherein the housings in which the flat or L-shaped strips are inserted are sealed by high pressure/high temperature lamination of thermoplastic strips.

14. The thermoformable panel according to claim 1, wherein the reinforcing strips, as regards either at least some of said strips or all of said strips and either at least part of the width of their widest side or the whole widest side, are arranged in a position where said widest side is in contact with the surface of at least one face of the panel or honeycomb core, said strips being locked in a structure of said panel or against the honeycomb core with a coating layer which, when coupled to the panel or the honeycomb core, overlaps also said r strips.

15. The thermoformable panel according to claim 14, wherein at least some of the stiffening strips are arranged in a contact position against at least one face of the honeycomb core along an entire length and width extension of their widest side.

16. The thermoformable panel according to claim 14, wherein at least part or the entire widest side of the stiffening strips adhere against the face of the honeycomb core, one or more stiffening strips being coupled to both the opposite faces of the panel or the honeycomb core.

17. The thermoformable panel according to claim 1, wherein all the stiffening strips are oriented in a same direction and parallel to each other, preferably arranged in a straight line.

18. The thermoformable panel according to claim 17, wherein the stiffening strips or at least some of the stiffening strips are oriented parallel to a longitudinal length of the honeycomb core or panel, or along a direction of a longest side of the honeycomb core or panel.

19. The thermoformable panel according to claim 1, wherein the stiffening strips have thicknesses of less than a millimeter, preferably not more than 0.5 mm.

20. The thermoformable panel according to claim 19, wherein the stiffening strips have thicknesses between 0.05 mm and 0.3 mm.

21. The thermoformable panel according to claim 1, wherein the stiffening strips have a width comprised between a width less than a thickness of the honeycomb core, when they are arranged edgewise, and a width between 0.5 and 10 cm, when the strips are arranged in flat position, that is, parallel to the faces of the panel and/or the honeycomb core.

22. The thermoformable panel according to claim 1, wherein the strips are made of steel.

23. The thermoformable panel according to claim 1, wherein at least some of the strips are at least partially embedded in a thickness of the panel or honeycomb core, and wherein some of the strips are arranged with at least part or an entire widest side thereof either in contact with or parallel to the faces of the honeycomb core.

24. The thermoformable panel according claim 1, wherein the coating layer consists of at least one plate of thermoplastic material filled with vegetable and/or mineral inerts, for example polypropylene or other thermoplastic materials.

25. The thermoformable panel according to claim 25, wherein a thickness of the coating layer ranges between 0.2 and 2 mm, preferably between 0.2 and 0.6 mm.

26. A method of manufacturing a thermoformable panel according to claim 1, wherein at least some of the strips are at least partially embedded in the thickness of the honeycomb core, the method comprising the following steps: step a) generating in the thickness of the honeycomb core a number of cut-outs or housings partially extending into said thickness, the cut-outs being open only to one face of said panel and/or honeycomb core and having a predetermined pattern; step b) inserting into each of said cut-outs a corresponding metal stiffening strip; or step c) coupling at least one coating layer to one or two opposite faces of the panel or honeycomb core with physical-chemical adhesion.

27. The method according to claim 26, further comprising providing reinforcements of the coating layer coinciding with at least some of the stiffening strips, the step c) being preceded by a step of b2) arranging reinforcing strips of a thermoplastic material, preferably a material equal to that of the reinforcing layer, to be directly overlapped along at least some of the stiffening strips, or alternatively b3) arranging reinforcing strips of a thermoplastic material, preferably a material equal to that of the reinforcing layer, to be directly overlapped to the coating layer on an opposite side with respect to the side in contact with the honeycomb core and, when coupled to the honeycomb core, in a position coincident with at least some of the stiffening strips before step c) is carried out.

28. The method according to claim 26, wherein at least some of the stiffening strips have part of their widest side, preferably their widest side, adherent against at least one of the faces of the honeycomb core, further comprising the following steps: step a1) arranging one or more stiffening strips on one or both sides of the panel or the honeycomb core; step c) coupling, with physical chemical adhesion, at least one coating layer to two opposite faces of the panel or honeycomb core, each of the coating layers adhering against both the corresponding face of the panel or honeycomb core and the one or more metal strips adhering against said faces.

29. The method according to claim 26, wherein, in step c, the coupling takes place in a rolling mill at a heating temperature preferably between 180 C. and 300 C., in particular between 210 C. and 240 C., preferably about 230 C. and optionally further comprising a concurrent thermoforming step of the panel in a mold according to a pattern of a three-dimensional panel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0112] These and other advantages of the present invention will be more apparent from the following description of some exemplary, non limiting embodiments depicted in the accompanying drawings, wherein:

[0113] FIGS. 1A to 1D show a first embodiment respectively in cross section and in different manufacturing steps and in a partially sectional plan view, respectively.

[0114] FIGS. 2A to 2D show, similar to the previous figures, a first embodiment variation of the embodiment according to FIGS. 1A to 1D.

[0115] FIGS. 3A to 3D show, similar to the previous figures, a second embodiment variation of the embodiment according to FIGS. 1A to 1D.

[0116] FIGS. 4A to 4D show a second embodiment respectively in cross section and in different manufacturing steps and in a partially sectional plan view.

[0117] FIGS. 5A to 5D show, similar to the previous FIGS. 4A to 4D, an embodiment variation of the embodiment according to FIGS. 4A to 4D.

[0118] FIGS. 6A to 6D show, similar to the previous figures, an embodiment variation in which the strips have L-shaped section.

[0119] FIGS. 7A to 7D show, similar to the previous figures, an embodiment variation in which the strips have T-shaped section.

[0120] FIGS. 8A to 8D show, similar to the previous figures, an embodiment variation in which the strips have rectangular section, open to one side, i.e. without one side or shaped as a staple.

[0121] FIG. 9 shows a flow diagram of the manufacturing method of a panel according to the present invention and according to the embodiments of FIGS. 1 to 3 and 6, 7 and 8.

[0122] FIG. 10 shows a flow diagram illustrating the steps for preparing the strip according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0123] The following description will illustrate various embodiments of the panel according to the present invention. These variations should not be considered as restrictive, but only exemplifying the inventive conception which consists in providing metal strip-shaped stiffening elements incorporated in the panel structure between the honeycomb core and at least one of the coating layers that are on one of the faces of the panel.

[0124] Although the examples show coating layers on both sides of the honeycomb core plate, even only one of the faces can be coupled to a coating layer or else the two faces can be coupled to different coating layers according to the various embodiments thereof provided in the present description.

[0125] FIGS. 1C and 1D show a first embodiment in which a honeycomb core plate 1 is provided with a foil or a thin metal stiffening strip 4 each embedded in a housing 101 in the form of pocket or cut-out.

[0126] Any number of housings 101, and thus of metal stiffening strips 4, is possible. This number varies depending on the mechanical strength in relation to the overall weight of the panel.

[0127] The housings 101 are made so that their depth is less than the overall thickness of the honeycomb core plate 1 and, in the illustrated embodiment, the metal stiffening strips 4 are substantially completely embedded within the corresponding housing 101.

[0128] Alternatively, said metal strips 4 can be provided so that only a part of their width is embedded.

[0129] A first non-illustrated embodiment variation may provide that all said metal strips 4, or some of them, protrude only by a band along the peripheral longitudinal side edge, by a small amount with respect to their overall width, and such a protrusion, when the honeycomb core plate 1 is coupled by heating or compression to the coating layer or layers 2, is partially incorporated in the outer coating layer 2 or in the remaining thickness of the honeycomb core plate 1 on the bottom side of the housings 101.

[0130] Alternatively or in combination, it is also possible that at least some, if not all metal strips 4 protrude by a substantial portion of their overall width from the housings 101, and that said protruding part is bent against the surface of the honeycomb core plate 1 on the side of the housing openings 101.

[0131] This variation is not specifically illustrated, but it is clear from this description that in this case the cross-section of the strip would be L-shaped or possibly even T-shaped.

[0132] In the preferred example shown, the housings 101 and the metal strips 4 housed therein take an orientation perpendicular to at least one face of the finished panel or honeycomb core plate 1.

[0133] However, it is to be understood that according to a variation, at least some of said housings 101 and/or the corresponding metal strips 4 may have orientations more or less tilted with respect to the direction perpendicular to at least one face of the finished panel or honeycomb core plate 1 and/or also may have a possible profile non-straight in cross-section but always such as to allow the metal strip 4 and/or sheet to be inserted in the housings 101 themselves. This applies to all the above described variations.

[0134] FIGS. 1A and 1B show exploded conditions of the exemplary embodiment according to FIGS. 1C and 1D, which conditions relates to steps of the panel manufacturing process.

[0135] In FIG. 1, after the cut-outs 101 have been made in the thickness of the honeycomb core plate 1, to a depth such that they do not pass from one side to the other of the honeycomb core plate 1, but they leave the bottom end covered by a layer of material 201, the individual metal strips 4 are inserted into each of the housing 101 provided for them.

[0136] The cut-outs can be made by various working techniques, for example by means of knives or saws or by laser cutting.

[0137] FIG. 1B shows the step of applying the coating layers 2 to the top and bottom faces of the laminated core plate 1 provided with metallic stiffening strips 4 embedded in the housings 101.

[0138] According to a non-limiting example, the honeycomb core plate is preferably made of cardboard or similar materials and is obtained according to known techniques.

[0139] According to an example, the coating layer or layers 2 are made of thermoplastic material, such as polypropylene or the like, filled with inert fillers such as vegetable fibers and/or mineral fibers.

[0140] According to still another variation, the coating layer or layers 2 may be constituted by at least two layers, preferably three layers, among which at least one layer consists of a nonwoven material of fibers of a first thermoplastic polymer and at least one second layer consisting of a film of a second thermoplastic polymer other than the thermoplastic polymer constituting the fibers of the nonwoven material and having a softening temperature (viscoelastic transition) lower than that of the thermoplastic polymer constituting the fibers of the nonwoven material.

[0141] In particular, the second thermoplastic polymer has the lowest softening temperature that ranges from about 80 C. to 120 C., while the first thermoplastic polymer constituting the fibers of the nonwoven material has higher softening temperature that ranges from about 180 to 300, particularly from about 210 to 250 C., preferably about 230 C.

[0142] In a variation, the coating layer 2 comprises two films constituted by the second thermoplastic polymer, the nonwoven material layer of fibers of the first thermoplastic polymer being provided in-between these two films.

[0143] For example, the nonwoven material may consist of PET fibers and can be coated with two films having a double effect, namely to stop the sliding of the fibers when they are subjected to a resulting force also obtained by using a mix of two fibers having different molecular weights and therefore different softening temperatures, as described above.

[0144] The coupling of the coating layer or layers 2 to the honeycomb core plate 1, according to the above described various variations, is carried out for example by hot rolling.

[0145] Preferably, the coupling takes place in a rolling mill at a heating temperature between 180 C. and 300 C., in particular between 210 C. and 240 C., preferably about 230 C.

[0146] In these conditions, referring to the embodiment in which the coating layer 2 is made of at least one film and at least one nonwoven material layer, the polymer with lower viscoelastic transition temperature penetrates the interstices of nonwoven fibers. The latter remain substantially intact since they are made up of a polymer having higher softening temperature. Therefore, the mass of the polymer having lower softening temperature surrounds and swallows up the fibers thereby forming a reinforcing grid that, upon cooling, remains firmly anchored in the polymer material having lower softening temperature. At the same time, the pressure applied during the lamination against the honeycomb core plate 1 is such as to cause the coupling to the honeycomb core plate 1 as described in document WO2015/125023 and, at the same time, the sealing and locking of the metal strips inside the housings and/or against the honeycomb core plate 1.

[0147] The thickness of the coating layer 2 may range between 0.2 and 0.6 mm, preferably between 0.3 and 0.4 mm.

[0148] As regards the metal stiffening strips or sheets 4, their size and number and arrangement on the surface of the panel or honeycomb core plate 1 may vary depending on the mechanical strength effects, in relation to the overall weight of the panel, required by the use specifications of the panel itself.

[0149] FIGS. 2A to 2D and 3A to 3D show two embodiments of an embodiment variation in which the opening area of the housings 101 of the metal strips 4 is further reinforced to effectively restrain and lock in place said strips or said sheets 4. In fact, in case of panel bending, the sideways edges of the sheets or strips act against the coating layer and may cut the layer thereby jeopardizing both the mechanical constraint to the panel and the stiffening effect.

[0150] In this case, in the embodiment of FIGS. 2A to 2D, there is not only the coating layer 2 coupled to the honeycomb core 1 but also reinforcing strips 3 of coating material which are made of thermoplastic material compatible with that of the coating layers 2, preferably of the same material, and which extend each along at least part of the length of each housing 101 and therefore of each metal strip 4. The strips have width such as to overlap to a certain extent the two longitudinal edges of the housings 101 and, in the example shown in FIGS. 2A to 2D, are arranged on the outer face of the coating layer before the latter is coupled to the honeycomb core 1 provided with the housings 101 and the metal strips 4.

[0151] The hot-rolling coupling process swallows up the reinforcing strips 3 into the material mass of the coating layer 2, generating, at the end of hot rolling, a reinforced zone coincident with each metal strip 4 and at the same time an outer surface of the coating layer without protrusions at said reinforcing strips 3 and wherein said strips are no longer visible.

[0152] The embodiment of FIGS. 3A to 3D differs from the previous one because the reinforcing strips 3 are arranged directly on the honeycomb core plate 1 and are overlapped by the coating plate 2.

[0153] The hot rolling action causes a similar effect to that described in the previous variation of FIGS. 2A to 2D.

[0154] FIGS. 4C and 4D show a further embodiment of the panel according to the present invention which differs from the previous one in that the metal strips 4 or the metal stiffening sheets are not arranged as embedded in the thickness of the honeycomb core 1 and substantially oriented edgewise with respect to its face, but are arranged so as to have at least part, preferably their entire widest side, against at least one face of the honeycomb core 1.

[0155] As previously mentioned, the width of the strips or sheets and the thickness thereof, as well as their number and the spreading pattern, i.e. the spreading pattern on the overall surface of the panel or honeycomb core 1, may vary according to specifications of mechanical strength of the panel in relation to the overall weight thereof.

[0156] Since in case of a bending of the panel, when the concavely deformed side is the one combined with the metal strips 4 or metal sheets, these strips tend to detach from the honeycomb core and therefore they also act in decoupling way to decouple the coating layer 2 from said honeycomb core 1, the variation of FIGS. 5C and 5D is provided, wherein the metal strips or sheets 4 are coupled to the two opposed faces of the honeycomb core 1.

[0157] This solution is based on the fact that when the metal strips or sheets are in their flat coupling state against the honeycomb core 1, they apply an action that increases the resistance to tensile stresses thereon, whereas in the compression state they are not effective in absorbing these stresses.

[0158] The compression action on the metal strips occurs when these are on the concave side of the panel, while the tensile action on the sheets is applied on those sheets on the convex side of the panel when the latter is subjected to bending stress. The concave side, or the side that tends to be deformed in such condition, is the one on which the stress force is applied while the convex side is the opposite one.

[0159] By providing metal stiffening strips on the two sides of the honeycomb core 1, there is always a set of strips operating under tensile stress regardless of which side of the panel the stress force acts on and therefore regardless of which side of the panel is subjected to a strain stress to be deformed to a concave shape.

[0160] As for the coating layer or layers 2, what described above for the previous embodiments of FIGS. 1A to 3D is true also in these two exemplary embodiments.

[0161] FIGS. 4A and 4B and 5A to 5B show various states of the manufacturing process similar to FIGS. 1A, 1B, 2A, 2B, 3A, 3B with the obvious variations due to the different position of the metal strips 4.

[0162] As regards the variation according to FIGS. 5A to 5D, both the position and the number and possibly also the size of the metal strips on the two sides of the honeycomb core 1 may be different from each other.

[0163] It is to be noted that one or more of the above described variations can be provided for at least one or a part of the metal stiffening strips 4, whereby the panel has at least one of the stiffening strips made according to the variations of FIGS. 1A to 1D and/or at least one of the stiffening strips made according to the variation of FIGS. 2A to 2D and/or at least one of the stiffening strips made according to the variation of FIGS. 3A to 3D and/or at least one of the stiffening strips made according to the variation of FIGS. 4A to 4D and/or at least one of the stiffening strips made according to the variation of FIGS. 5A to 5D and/or at least one of the stiffening strips made according to one of the variations described and not shown.

[0164] With regard to the metal strips, being understood that their size, material and number may anyway vary according to the desired mechanical strength as well as depending on the desired maximum weight, according to a further characteristic that can be provided in combination with any one of the previous embodiments, the metal strips are relatively thin and may have thicknesses less than a millimeter, preferably not more than 0.5 mm.

[0165] A preferred embodiment provides that the strips have thickness between 0.05 mm and 0.3 mm.

[0166] The width of the strips may range between a width less than the thickness of the honeycomb core and a width between 0.5 and 10 cm, and preferably, when the strips are arranged so as to be flat against the honeycomb core, the width is less than 10 cm and roughly from 2 to 6 cm.

[0167] When the strips are arranged so that their widest side adheres against the faces of the honeycomb core, the width may vary also depending on mechanical features, in relation to the weight, desired for the panel and therefore depending on the number of strips and the density thereof in relation to the size of the panel faces.

[0168] With regard to the material, several metal materials are possible, but a preferred embodiment provides steel metal strips.

[0169] In relation to the above described embodiments, it should be noted that in any of the described variations, the metal stiffening strips are always directly coupled to the honeycomb core and are locked to the same and in the panel structure thanks to the coating layers coupled to the faces of the honeycomb core and/or to strips that seal the slits and may be additional to the reinforcing strips or be constituted by said reinforcing strips themselves.

[0170] Advantageously, according to an embodiment, the slits are sealed by high pressure/high temperature lamination, for example at 230 C. and 40 N/cm2, of thermoplastic strips possibly TNT-reinforced.

[0171] Depending on the application to either the edgewise strip or L-shaped strip, the width may vary although being always kept very limited.

[0172] In an embodiment, it is possible to provide that the width of the sealing strips is between about 10 and about 20 mm. This sizing is enough to structurally contain the transversal weakening of the structure of the panel and to limit its increase in weight.

[0173] Such examples, however, should not be considered as restrictive, since the described and claimed characteristics may also apply to a panel core consisting of any lightened core, including also a honeycomb core covered by coating layers on either or both of the two faces. In this case, the housings are also open along the thickness of one of said coating layers forming the core, i.e. the metal strips are in contact with the outer surface of either or both the two coating layers forming one or two opposite faces of the core, while being locked to said core by applying an additional locking layer which may be a coating layer similar to the one already present on the core or a finishing layer having further different surface characteristics.

[0174] Basically, in this case, the panel core is a multilayer core rather than consisting only of the honeycomb core.

[0175] Referring to FIGS. 6A to 6C these show, similar to FIGS. 1A to 1C, an embodiment variation of the panel.

[0176] In FIGS. 6A to 6C, same reference numbers have been used for equal parts or parts having the same functions with respect to the embodiment of FIGS. 1A to 1C.

[0177] As evident, the only difference is the shape of the strips 4 having L section, a branch of the L being intended to be inserted into a corresponding slit 101, while the other branch remains outside the slit and lies flat against the surface of the panel, i.e. the honeycomb core 1.

[0178] Therefore, not only the strip has a ribbing providing it with greater stiffness, but also operates simultaneously according to the first embodiment of FIGS. 1A to 1D and the respective variations 2A to 2D and 3A to 3D, as well as according to the variations of FIGS. 4A to 4D and 5A to 5D.

[0179] Similarly, stiffening and/or sealing strips of the slits can be provided, as in the variation according to FIGS. 3A to 3D.

[0180] According to still another characteristic, in place of metal strips or in place of at least some of the metal strips, strips made of high-Tf plastic material can be used, i.e. having high heat-softening temperature and woven fibers such as of strap type or the like.

[0181] FIGS. 7A to 7D show, similar to the previous figures, an embodiment variation in which the strips have T-shaped section.

[0182] In this variation, if the shaping of the strips was to be obtained by folding, it would be more complex, whereas when the strips are obtained, for example, by extrusion, which is the case of plastic strips, or by lamination, the T-shape can be directly obtained in a simple manner.

[0183] FIGS. 8A to 8D show, similar to the previous figures, an embodiment variation in which the strips have rectangular section open to one side, i.e. without one side or shaped as a staple.

[0184] The advantage of this variation is that it doubles the number of stiffening strips oriented perpendicularly to the panel or core and, at the same time, it provides a flat strip combined with the two perpendicular strips and in combination two ribs consisting of the folding edges.

[0185] From the strip manufacturing point of view, this variation is simpler than the T-shaped variation since it can be obtained by continuously folding a flat strip which is unwound for example from a reel and passes through a folding station having folding walls that gradually lift the two longitudinal side flaps of the strip and, in combination with central sliding blocks, form a longitudinal folding edge along each area connecting the longitudinal side flap and a central band.

[0186] Referring to the flow diagram of FIG. 9, this shows the main steps for manufacturing a panel according to the above described examples involving at least one cut-out in the thickness of the panel and/or the honeycomb core thereof.

[0187] At step 900 a panel or a honeycomb core of said panel is prepared and at step 910 one or more cut-outs are made in the thickness of the panel or honeycomb core. The cut-outs extend only partially in the thickness of the panel or honeycomb core, thus being open only at one face of said panel or said honeycomb core.

[0188] At step 920, each strip is introduced in a corresponding cut-out. The stiffening strips can be either flat and angular, i.e. with L-shaped, T-shaped, or rectangular or square section and without one side.

[0189] After inserting the stiffening strips, at step 930 it is possible to choose whether to provide a reinforcing strip of thermoplastic material for at least some of the cut-outs where a corresponding strip is housed. If so, at step 940, these reinforcing strips are arranged in coincidence with each cut-out or part of them.

[0190] At step 950 it is required to choose between the variation in which at least part of the cut-outs, or all of them, are sealed with thermoplastic material or if this is not necessary. In the former case, then a strip of thermoplastic material having high heat-softening temperature is arranged at all the cut-outs or part of them. This strip can be provided in addition to the reinforcing strips or be the reinforcing strip itself. In this case, this step 950 and 960 is a repeat and can be omitted.

[0191] Once the sealing strips are applied and sealing is carried out by hot rolling as described above, the coating layer or layers can be coupled to the panel or to the honeycomb core, as depicted in step 980, for example by hot rolling.

[0192] In case of manufacturing a panel according to the embodiments of FIGS. 4 and 5, in which the strips are arranged flat against one or both faces of the panel or honeycomb core, the process substantially follows the diagram of FIG. 9, obviously omitting the steps 910 950 and 960, and the step 920 being modified as regards the simple arrangement of the strips on the surface or surfaces of the panel or core.

[0193] Also for the manufacture of the variations in FIGS. 4 and 5, there are still the other steps involving the reinforcing strips and the application of the coating layers.

[0194] In an embodiment variation, the strips may be combined not directly with the core layer but with an intermediate structure panel having a laminate layer on either or both of the two faces of the core layer. In this case, of course, the method according to FIG. 9 and the above-mentioned variations provides, upstream of the depicted steps, a laminating step to laminate said layer or layers on the face or faces of the core layer.

[0195] FIG. 10 shows a flow diagram relating to the steps to prepare the stiffening strips. These steps precede, directly or at different preceding times, the steps according to FIG. 9 and the described variations.

[0196] At step 1100 a strip of stiffening material, which can be metal or plastic material, is provided.

[0197] The plastic strip or metal strip can be obtained by extrusion or drawing and in this case they may already have the selected shapes or profiles.

[0198] When, as in the case of the process of FIG. 10, at the beginning there is a flat strip preferably wound in the form of a coil, the process initially requires the selection of the sectional shape of the strip. When the flat strip is selected, as shown at step 1120, then the process directly passes to the cutting-out step 1160 and then to the panel application according to modes of the example described with reference to the variation of FIG. 9.

[0199] On the contrary, when an angled strip is selected as in step 1130, the process includes the steps 1140 in order to define the sectional shape and, as a result, the corresponding shaping of the strip 1150. Once the strip is shaped, at step 1160 it is also cut to size and then delivered to the application 1170 to the panel and/or core.

[0200] If there is no selection between a flat strip and a shaped strip, the process continues with the formation of the panel without strips, as depicted at step 1180.