Hollow structure and luggage board

Abstract

To efficiently improve impact resistance.SOLUTION: The side walls 23 located between the adjacent first cell side walls of the first cell row side walls are formed of two layers, and have the first joining portions where the surfaces of the side walls 23 are joined to each other at the end portions on the top S1a side 21a side, and have the folded portions at the end portions on the side opposite to the top S1 side 21a side, and the side walls 23 located between the adjacent second cell side walls of the second cell row side walls are formed of two layers, and have the second joining portions where the surfaces of the side walls 23 are joined to each other at the end portions on the bottom S2a side 21b side. S2, A folded portion is provided at an end portion opposite to the bottom wall 21b side, and a joining force of the first joining portion is larger than a joining force of the second joining portion.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present disclosure relates to a hollow structure and a luggage board. [Background technology]

[0002] Patent Document 1 describes a hollow structure used for protective materials and the like. As shown in Figure 11, this hollow structure comprises a core layer obtained by folding a sheet material 50 having projections and recesses, and two skin layers bonded to both sides of this core layer. A plurality of cells are arranged inside this hollow structure. The partition walls located between adjacent cells have a two-layer structure. One of the ends of this partition wall has a joint where the two layers are bonded to each other, and the other end has a folded portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4368399 Summary of the Invention [Problem to be solved by the invention]

[0004] The hollow structure described above is required to have further improved impact resistance. An object of the present disclosure is to provide a hollow structure having efficiently improved impact resistance. [Means for solving the problem]

[0005] A hollow structure according to one embodiment of the present disclosure has a plurality of cells. The hollow structure comprises a core layer having a plurality of first walls, a plurality of second walls, and a plurality of partition walls, and first and second skin layers respectively bonded to both sides of the core layer. The plurality of cells includes a plurality of first cells and a plurality of second cells. Each of the first cells is partitioned by the first wall, a plurality of the partition walls extending from the first wall, and the second skin layer. Each of the second cells is partitioned by the second wall, a plurality of the partition walls extending from the second wall, and the first skin layer. The plurality of first cells aligned in one direction constitute a first cell row, and the plurality of second cells aligned in the one direction constitute a second cell row. The plurality of partition walls include a plurality of first partition walls having a two-layer structure located between adjacent first cells in the first cell row, and a plurality of second partition walls having a two-layer structure located between adjacent second cells in the second cell row. The first partition wall has a first joint at an end closer to the first wall where two layers constituting the first partition wall are joined together, and a first folded portion at an end farther from the first wall. The second partition wall has a second joint at an end closer to the second wall where two layers constituting the second partition wall are joined together, and a second folded portion at an end farther from the second wall. The joining strength of the first joint is greater than the joining strength of the second joint. [Brief explanation of the drawings]

[0006] [Figure 1A] FIG. 1 is a perspective view of a hollow structure according to an embodiment. [Figure 1B] FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A. [Figure 1C] FIG. 1C is a cross-sectional view taken along line 1C-1C in FIG. 1A. [Figure 2A] FIG. 1B is a schematic diagram showing the state of the sheet material constituting the core layer of the hollow structure of FIG. 1A before folding. [Figure 2B] FIG. 2B is a perspective view of the sheet material of FIG. 2A. [Figure 2C] FIG. 2C is a perspective view showing the sheet material of FIG. 2B in a folded state. [Figure 3] FIG. 10 is a perspective view of a hollow structure according to a first modified example. [Figure 4] FIG. 10 is a perspective view of a core layer according to a second modified example. [Figure 5] FIG. 10 is a perspective view of a core layer according to a third modified example. [Figure 6] FIG. 10 is a top view of a core layer of a fourth modified example. [Figure 7] FIG. 2 is a cross-sectional view of the sheet material and mold immediately after vacuum forming. [Figure 8] 8 is an end view taken along line 8-8 of FIG. 6. [Figure 9] 9 is an end view taken along line 9-9 of FIG. 6. [Figure 10] FIG. 10 is a cross-sectional view of a core layer of a fifth modified example. [Figure 11] FIG. 10 is a perspective view of a sheet material that constitutes a core layer in a conventional hollow structure. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the hollow structure will now be described. In the specification and claims, terms such as "first," "second," etc. are used to distinguish between similar elements and do not necessarily denote a particular sequential or chronological order.

[0008] All features disclosed in the specification and / or claims are intended to be disclosed separately and independently from one another for purposes of the original disclosure and for purposes of limiting the claimed invention independently of the combination of features in the embodiments and / or claims.

[0009] The disclosed embodiments should not be construed as limiting the scope of the invention, and features of separate embodiments performing equivalent or the same function may be interchanged between the disclosed embodiments within the scope of the amended claims. The recitation of numerical ranges by endpoints includes all numbers within that range. For example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5.

[0010] As shown in FIG. 1A, the hollow structure 10 includes a core layer 20 and first and second skin layers 30, 40 bonded (e.g., welded) to both sides of the core layer 20. The core layer 20 has a plurality of first walls 21a, a plurality of second walls 21b, and a plurality of partition walls 23, and defines a plurality of cells S having a hexagonal prism shape. The plurality of cells S includes a plurality of first cells S1 and a plurality of second cells S2. Each first cell S1 is defined by the hexagonal first wall 21a, a plurality of partition walls 23 extending from the first wall 21a toward the second skin layer 40, and the second skin layer 40. Each second cell S2 is defined by the hexagonal second wall 21b, a plurality of partition walls 23 extending from the second wall 21b toward the first skin layer 30, and the first skin layer 30.

[0011] The core layer 20 has a plurality of first cell rows S1a in which a plurality of first cells S1 are aligned along one direction (X-axis), and a plurality of second cell rows S2a in which a plurality of second cells S2 are aligned along the same direction (X-axis). The X-axis, Y-axis, and Z-axis are mutually perpendicular axes, and the thickness direction of the hollow structure 10 is along the Z-axis. The first and second cell rows S1a, S2a extend in a direction perpendicular to the thickness direction Z.

[0012] 1B and 1C, the plurality of partition walls 23 includes a plurality of first partition walls 23a, a plurality of second partition walls 23b, and a plurality of third partition walls 23c. The first and second partition walls 23a and 23b have a two-layer structure. The third partition wall 23c has a single-layer structure.

[0013] The first partition wall 23a is located between adjacent first cells S1 in the first cell row S1a. The first partition wall 23a has a first joint portion 24a at a first end in the thickness direction Z (the end closer to the first wall 21a) where the surfaces of two layers constituting the first partition wall 23a are joined to each other by welding, and a first folded portion 25a at a second end in the thickness direction Z (the end farther from the first wall 21a). The two layers constituting the first partition wall 23a are not joined to each other between the first joint portion 24a and the first folded portion 25a.

[0014] The second partition wall 23b is located between adjacent second cells S2 in the second cell row S2a. The second partition wall 23b has a second joint portion 24b at a second end in the thickness direction Z (the end closer to the second wall 21b) where two layers constituting the second partition wall 23b are joined to each other by welding, and a second folded portion 25b at a first end in the thickness direction Z (the end farther from the second wall 21b). The two layers constituting the second partition wall 23b are not joined to each other between the second joint portion 24b and the second folded portion 25b.

[0015] The two layers constituting the first partition wall 23a are not joined to each other near the center in the thickness direction Z. Therefore, a first communication portion 26a that connects the first cells S1 to each other may be formed between the first cells S1 adjacent to each other in the Y direction. Similarly, the two layers constituting the second partition wall 23b are not joined to each other near the center in the thickness direction Z. Therefore, a second communication portion 26b that connects the second cells S2 to each other may be formed between the second cells S2 adjacent to each other in the Y direction. Specifically, the first communication portion 26a is a gap that may be formed between two adjacent or abutting first partition walls 23a. Similarly, the second communication portion 26b is a gap that may be formed between two adjacent second partition walls 23b. In other words, even if the unjoined portions of the two layers appear to be in contact with each other, fluid may flow between the two layers.

[0016] The third partition wall 23c is located between the first cell S1 and the second cell S2. The first cell row S1a and the second cell row S2a share multiple third partition walls 23c and are alternately arranged along the Y axis perpendicular to the X axis. The six partition walls 23 that define each first cell S1 include two first partition walls 23a and four third partition walls 23c, and the six partition walls 23 that define each second cell S2 include two second partition walls 23b and four third partition walls 23c.

[0017] The core layer 20 and the skin layers 30, 40 are made of a thermoplastic resin. The thermoplastic resins constituting the core layer 20 and the skin layers 30, 40 are conventionally well known, and the materials thereof are not particularly limited. Examples of thermoplastic resins include polypropylene resin, polyamide resin, polyethylene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylic resin, polybutylene terephthalate resin, etc. The thermoplastic resins constituting the core layer 20 and the skin layers 30, 40 may be the same material or different materials. The core layer 20 and the skin layers 30, 40 of this embodiment are both made of a polypropylene resin.

[0018] The thicknesses of the first wall 21a, the partition wall 23, and the second wall 21b of the core layer 20 are not particularly limited, but are, for example, 0.1 mm to 0.5 mm. The thicknesses of the skin layers 30, 40 are not particularly limited, but are, for example, 0.3 mm to 0.6 mm.

[0019] The thickness of the first wall 21a may be greater than the thickness of the second wall 21b. A method for manufacturing the hollow structural body 10 will be described. The manufacturing method of the hollow structure 10 includes a folding step, a heating step, and a laminating step.

[0020] (Folding process) In the folding step, a core layer is produced by folding and forming a flat sheet material 200 as shown in Fig. 2A. The sheet material 200 is vacuum formed so as to have predetermined concaves and convexes.

[0021] The sheet material 200 has first and second bulging portions 210, 220 in strip shapes extending in the X direction. The first bulging portions 210 and the second bulging portions 220 have a width in the Y direction and are arranged alternately along the Y axis. The first bulging portions 210 and the second bulging portions 220 protrude in opposite directions along the Z axis. When the sheet material 200 is viewed in a plan view, the first bulging portions 210 and the second bulging portions 220 have the same shape and are arranged at positions shifted by ½ pitch along the X axis.

[0022] The first bulging portion 210 has a first bulging surface 210a, two partition surfaces 210b, and two end surfaces 210c. The cross-sectional shape of the first bulging portion 210 cut along a plane including the Y-axis and Z-axis is a trapezoid formed by bisecting a regular hexagon by its longest diagonal. The two end surfaces 210c are located at the boundary line P' shown in FIG. 2A. The angle between the end surface 210c and the first bulging surface 210a is approximately 90°.

[0023] The second bulging portion 220 has a second bulging surface 220a, two partition surfaces 220b, and two end surfaces 220c. The cross-section of the second bulging portion 220 cut along a plane including the Y-axis and Z-axis is a trapezoid formed by bisecting a regular hexagon along its longest diagonal. The two end surfaces 220c are located at the boundary line Q' shown in FIG. 2A. The angle between the end surface 220c and the second bulging surface 220a is approximately 90°. The length of the second bulging portion 220 along the X-axis, i.e., the length between the two end surfaces 220c, is the same as the length of the first bulging portion 210 along the X-axis, i.e., the length between the two end surfaces 210c. The end surface 220c of the second bulging portion 220 is located at the center of the first bulging portion 210 in the X-direction. The partition surface 210b of the first bulging portion 210 and the partition surface 220b of the second bulging portion 220 have the same shape. The core layer 20 is formed by folding the sheet material 200 sequentially along the boundary lines P' and Q'.

[0024] As shown in FIG. 2B, the sheet material 200 is mountain-folded along the boundary line P' and valley-folded along the boundary line Q'. As shown in FIG. 2C, the first bulging portion 210 is valley-folded at the boundary line Q' located in the center in the X direction, and the first bulging surfaces 210a divided by the boundary line Q' abut against each other. In the first bulging portion 210 folded in this manner, the abutting first bulging surfaces 210a form the first partition wall 23a, and the partition surface 210b forms the third partition wall 23c. At a first end (the upper end in FIG. 2C) of the first partition wall 23a, two end surfaces 210c aligned along the X axis form the first wall 21a having a single-layer structure. A second end (the lower end in FIG. 2C) of the first partition wall 23a defines a first opening 27a.

[0025] The second bulging portion 220 is mountain-folded at a boundary line P' located in the center in the X direction between adjacent boundary lines Q', and the second bulging surfaces 220a divided by the boundary line P' abut each other. In the second bulging portion 220 folded in this manner, the abutting second bulging surfaces 220a form the second partition wall 23b, and the partition surface 220b forms the third partition wall 23c. At the second end (the lower end in FIG. 2C ) of the second partition wall 23b, two end surfaces 220c aligned along the X axis form the single-layer second wall 21b. The first end (the upper end in FIG. 2C ) of the second partition wall 23b defines a second opening 27b.

[0026] In this way, in the folding process, a first cell S1 having a first opening 27a is defined by the first wall 21a and the partition wall 23 extending from the first wall 21a, and a second cell S2 having a second opening 27b is defined by the second wall 21b and the partition wall 23 extending from the second wall 21b. The surfaces of the first wall 21a and the second wall 21b are smooth. A "smooth surface" means a flat surface with no irregularities when visually observed.

[0027] When the sheet material 200 is vacuum-formed into an uneven shape, the thickness of the portion that has been significantly deformed by the vacuum is thinner than the thickness of the other portion. Therefore, when the sheet material 200 is vacuum-formed, by vacuuming the second bulging portion 220 more strongly in the bulging direction, the thickness of the second wall 21b becomes thinner than the thickness of the first wall 21a. As a result, the thickness of the first wall 21a can be made relatively thicker than the thickness of the second wall 21b.

[0028] Specifically, in FIG. 2A , when the back surface (lower surface, not shown) of the sheet material 200 is placed facing a vacuum forming mold and molded, the two end surfaces 210c arranged on either side of the boundary line P′ become the first surface of the core layer 20 (the upper surface in FIG. 1B ), and the end surface 220c arranged on either side of the boundary line Q′ become the second surface of the core layer 20 (the lower surface in FIG. 1B ). Therefore, the thickness of the first wall 21a defining the first surface (end surface 210c) of the core layer 20 is thicker than the thickness of the second wall 21b defining the second surface (end surface 220c) of the core layer 20. The thickness of the first wall 21a is not particularly limited, but may be, for example, twice or more the thickness of the second wall 21b. The thickness of the partition wall 23 gradually increases from the second surface of the core layer 20 toward the first surface.

[0029] On the first surface of the core layer 20, the multiple cells S are neatly aligned along the X-axis and Y-axis. Near the second surface of the core layer 20, the thickness of the partition walls 23 is thinner than near the first surface. Therefore, on the second surface of the core layer 20, the multiple cells S aligned along the Y-axis are aligned in a slightly meandering pattern. Near the second surface of the core layer 20, the two layers constituting the partition walls 23 can be compressed more to bring the two layers into close contact with each other. Therefore, in the heating process described below, the two layers constituting the partition walls 23 can be more reliably welded together near the second surface. Depending on the thickness of the partition walls 23, the multiple cells S aligned along the Y-axis on the first surface of the core layer 20 may be aligned in a meandering pattern, as shown in FIG. 6 .

[0030] (Heating process) In the heating step, the core layer 20 produced in the folding step is pressed while being heated, thereby heat-welding (hereinafter simply referred to as "welding") the first end of the first partition wall 23a and heat-welding the second end of the second partition wall 23b.

[0031] As a method for heating the core layer 20, for example, a method in which the core layer 20 is heated by a heating device while being transported by a conveyor (not shown) can be employed. For example, the first and second surfaces of the core layer 20 are sandwiched between first and second conveyors, respectively, and the core layer 20 is heated by heaters arranged inside the first and second conveyors. At this time, the core layer 20 is transported along the X-axis. By pressing the core layer 20 with the first and second conveyors, a load is applied to the core layer 20 along the X-axis. A load may also be applied to the core layer 20 along the Z-axis by sandwiching the core layer 20 between first and second conveyors aligned along the Z-axis.

[0032] By pressing the core layer 20 while heating it, the two layers that make up the first partition wall 23a are welded together near the first wall 21a, thereby forming a first joint 24a. Also, the two layers that make up the first partition wall 23a are welded together near the second wall 21b, thereby forming a second joint 24b.

[0033] When pressing the core layer 20 from both sides, a load along the X-axis is unlikely to be applied near the centers of the first and second partition walls 23a, 23b. Therefore, the two layers constituting the first and second partition walls 23a, 23b are not welded to each other near the centers in the Z direction. As a result, a first communication portion 26a that connects the first cells S1 adjacent to each other along the Y-axis is formed near the center of the first partition wall 23a. Similarly, a second communication portion 26b that connects the second cells S2 adjacent to each other along the Y-axis is formed near the center of the second partition wall 23b.

[0034] The thickness of the partition wall 23 near the first wall 21a is greater than the thickness near the second wall 21b. Therefore, when pressing the core layer 20 from both sides, a relatively greater load is applied near the first wall 21a than near the second wall 21b. That is, the length dimension along the X axis of the core layer 20 obtained by the folding process is longer at the position where it contacts the first wall 21a than at the position where it contacts the second wall 21b. Therefore, the load applied to the core layer 20 by the first and second conveyors is greater at the first end of the first partition wall 23a. Welding under a greater load results in a greater bonding force. Therefore, the bonding force of the first bonding portion 24a is greater than the bonding force of the second bonding portion 24b.

[0035] (Lamination process) In the lamination process, first and second sheets (first and second skin layers 30, 40) are bonded to the first and second surfaces of the core layer 20, respectively. More specifically, the first and second sheets that will become the skin layers 30, 40 are heated and brought into contact with both surfaces of the core layer 20 for a predetermined time. This causes the first and second skin layers 30, 40 to be bonded (welded) to both surfaces of the core layer 20, respectively.

[0036] Through the above manufacturing steps, a flat hollow structural body 10 including a plurality of cells S is fabricated. The use of the hollow structure 10 is not particularly limited. Because the hollow structure 10 has a honeycomb structure, it has excellent impact resistance, sound insulation, and heat insulation. Therefore, the hollow structure 10 can be used appropriately for applications requiring these properties. Examples of uses of the hollow structure 10 include luggage boards, shelves, containers, etc.

[0037] When the hollow structure 10 is used for an application requiring a distinction between a front and a back, such as a luggage board or a shelf board, the first skin layer 30 may be the front surface, or the second skin layer 40 may be the front surface. Furthermore, of the first and second surfaces of the core layer 20, the one on which the multiple cells S are neatly aligned may be joined to the skin layer that becomes the front surface, or the one on which the multiple cells S are arranged in a slightly meandering pattern may be joined to the skin layer that becomes the front surface.

[0038] The operation and effects of this embodiment will be described. (1) Because the bonding strength of the first bonding portion 24a is greater than the bonding strength of the second bonding portion 24b, the two layers constituting the first partition wall 23a can be more effectively prevented from peeling off from each other at the first bonding portion 24a. Therefore, the hollow structure 10 can improve impact resistance from one side, i.e., the side where the first bonding portion 24a is provided in the thickness direction. Therefore, impact resistance can be efficiently improved.

[0039] Furthermore, the bending strength of the hollow structure 10 can be improved compared to an embodiment in which the joining strength of the first joining portions 24a is the same as the joining strength of the second joining portions 24b. (2) The thickness of the first wall 21a is relatively thicker than the thickness of the second wall 21b. This is because the thickness of the end surface 210c of the sheet material 200 that becomes the core layer 20 is relatively thicker than the thickness of the end surface 220c. Therefore, the strength of the first wall 21a can be relatively increased. As a result, the hollow structure 10 has improved impact resistance from the first surface side in the thickness direction, i.e., the side where the first bonding portion 24a is provided.

[0040] (3) The thickness of the first end (the end intersecting with the first wall 21a) of the partition wall 23 is relatively thicker than the thickness of the second end (the end intersecting with the second wall 21b). This allows the intersection between the partition wall 23 and the first wall 21a to be slightly crushed, more reliably joining (e.g., welding) this intersection to the first skin layer 30. That is, even if the partition wall 23 is slightly crushed near its first end, the strength of the partition wall 23 itself is ensured, and excessive crushing of the partition wall 23 can be suppressed. Furthermore, as shown in FIGS. 8 and 9 , the thickness of the partition wall 23 continuously decreases from the first end to the second end. The thickness of the first end of the partition wall 23 is thicker than the thickness of the second end. Therefore, for example, when the core layer 20 is heated from both sides, the amount of resin melted near the first end of the partition wall 23 is greater than the amount of resin melted near the second end. This ensures a large amount of resin melted by heating, more reliably welding the first end of the partition wall 23. On the other hand, the second end of the partition wall 23 is relatively thin and therefore easily heated by the heat from the heating device, so that the second end of the partition wall 23 can be efficiently heated and more reliably welded.

[0041] (4) The first cell rows S1a and the second cell rows S2a are arranged alternately, which makes it possible to make the impact resistance more uniform on both sides of the hollow structure 10. (5) The first joint 24a is a portion where two layers constituting the first partition wall 23a are welded together, and the second joint 24b is a portion where two layers constituting the second partition wall 23b are welded together. Therefore, the configurations of the first joint 24a and the second joint 24b can be simplified.

[0042] (6) A first communication portion 26a is formed between the first cells S1 adjacent to each other in the Y direction, and a second communication portion 26b is formed between the second cells S2 adjacent to each other in the Y direction. Therefore, when the hollow structure 10 is heated and bent, the heated air in the first cells S1 and the second cells S2 passes through the first communication portion 26a and the second communication portion 26b and spreads throughout the hollow structure 10. This makes it possible to suppress expansion of the first wall 21a and the second wall 21b.

[0043] This embodiment can be modified as follows: The configurations included in this embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0044] The first and second bonding portions 24a and 24b may be formed by applying an adhesive between the two layers that make up the first partition wall 23a or between the two layers that make up the second partition wall 23b. In this case, the bonding strength of the first and second bonding portions 24a and 24b can be changed by adjusting the type of adhesive and the state in which the adhesive is applied.

[0045] The core layer 20 may not have at least one of the first communicating portion 26a and the second communicating portion 26b. The two layers constituting the first partition wall 23a may be bonded to each other over their entire surfaces. Similarly, the two layers constituting the second partition wall 23b may be bonded to each other over their entire surfaces.

[0046] The hollow structure 10 does not have to be flat. At least a portion of the hollow structure 10 may be curved so that the outer surface defined by the first skin layer 30 is convex and the outer surface defined by the second skin layer 40 is concave. The hollow structure 10 can be curved as described above by press molding after the lamination process. This improves the impact resistance of the hollow structure 10 from the convex side. In such a curved portion of the hollow structure 10, the outer surface defined by the first skin layer 30 may be concave and the outer surface defined by the second skin layer 40 may be convex.

[0047] As in the first modified example shown in Figure 3, by press-molding a portion of the hollow structure 10 after the lamination process, a curved portion can be formed at any position. The height dimension of the convex surface 31 and the depth dimension of the concave surface 41 may be greater than the thickness dimension of the flat portion of the hollow structure 10. The hollow structure 10 may have multiple curved portions. In this case, the hollow structure 10 may have multiple curved portions that curve in different directions.

[0048] At least one of the first wall 21a and the second wall 21b may have an uneven shape or an uneven pattern on its outer surface. Such an uneven shape can create an anchor effect when joining (e.g., welding) the sheets that will become the skin layers. This can increase the bonding strength of the skin layers 30, 40. Increasing the bonding strength of the skin layers 30, 40 can improve the impact resistance of the hollow structure 10.

[0049] For example, as in a second modified example shown in Fig. 4, the first wall 21a (end surface 210c) of the core layer 20 may have a linear recess 28a extending along the Y axis. This recess 28a is recessed in the direction of pulling during vacuum forming. The recess 28a can increase the welding area between the core layer 20 and the skin layers 30, 40.

[0050] Alternatively, as in a third modified example shown in Fig. 5, the second wall 21b (end surface 220c) of the core layer 20 may have a plurality of wrinkle-like recesses 28b extending along the Y axis. The end surface 220c is relatively thin, and therefore easily softened by heating in the heating step. The recesses 28b can be formed by setting the heating temperature in the heating step higher.

[0051] As in a fourth modification shown in Figure 6, one of the first and second openings 27a, 27b (second opening 27b in Figure 6) may not be a regular hexagon. In Figure 6, the position of the first cell row S1a along the X axis is shifted, distorting the shape of the second opening 27b and making it no longer a regular hexagon. In this case, the cells S1 and S2 arranged alternately along the Y axis appear to meander.

[0052] The cause of the meandering of the cells S1 and S2 will be described with reference to FIG. 7 schematically shows a mold 251 for vacuum-forming the sheet material 200, and the sheet material 200 immediately after vacuum-forming. The mold 251 has a plurality of suction holes 252 that suck the sheet material 200. The mold 251 may be a cylindrical drum. By transporting the sheet material 200 while wrapping it around the cylindrical mold 251, it is possible to continuously form a long sheet material 200.

[0053] The second bulging portion 220 is stretched by being sucked into the mold 251 through the suction holes 252 as shown by the white arrows in FIG. 7 . This makes the second bulging portion 220 relatively thinner than the first bulging portion 210. At this time, the intersections between the second bulging surface 220a and the two partition surfaces 220b and the two end surfaces 220c may not form sharp corners. In this case, the second bulging surface 220a, the two partition surfaces 220b, and the two end surfaces 220c of the second bulging portion 220 are curved so as to bulge outward toward the mold 251, and the second bulging portion 220 has four rounded corners. At this time, the first bulging surface 210a, the two partition surfaces 210b (partition surfaces 220b), and the two end surfaces 210c of the first bulging portion 210 are curved so as to be recessed inward toward the mold 251, and the first bulging portion 210 has four sharp corners. In this case, the two first bulging surfaces 210a constituting the first partition wall 23a are curved so that their outer edges approach each other.

[0054] When the first walls 21a and the first openings 27a are regular hexagons, the second walls 21b and the second openings 27b are distorted hexagons. Alternatively, when the second walls 21b and the second openings 27b are regular hexagons, the first walls 21a and the second openings 27b are distorted hexagons.

[0055] In this way, the meandering state of the cells S changes depending on whether the first wall 21a or the second wall 21b becomes a regular hexagon. Even if distortion and meandering occur in multiple cells S, each cell S maintains its hexagonal columnar shape, so impact strength and bending strength are unlikely to decrease.

[0056] The distortion and meandering of the multiple cells S can occur, for example, because the first bulging surface 210a is curved or the second bulging portion 220 has rounded corners. In other words, even with a sheet material 200 having such characteristics, the core layer 20 can be formed while the cells S are distorted and meandering. This makes it possible to increase the molding speed of the sheet material 200 and the core layer 20, thereby improving work efficiency, and to suppress the occurrence of molding defects in the sheet material 200 and the core layer 20.

[0057] The two second bulging surfaces 220a that form the second partition wall 23b may be curved so that the centers of the surfaces approach each other, which improves the impact resistance of the second partition wall 23b. As in a fourth modified example shown in Figures 8 and 9, at least one of the first wall 21a and the second wall 21b may have a protrusion. As shown in Figure 8, the protrusion 110 of the first wall 21a is a portion that melts and protrudes from the first wall 21a by increasing the heating temperature or the pressing force in the heating process. The protrusion 110 may protrude in the direction in which the first surface 20a of the core layer 20 (the surface that is bonded to the first skin layer 30) extends, or may protrude in a direction intersecting with the first surface 20a. The protrusion 110 allows the core layer 20 to be more reliably welded to the first skin layer 30.

[0058] Similarly, the first folded portion 25a may be heated or pressed to form a protrusion 111 protruding from the first folded portion 25a. The protrusion 111 serves as a portion that welds the first partition wall 23a (first folded portion 25a) to the second skin layer 40. This increases the welding area of ​​the core layer 20 to the second skin layer 40, thereby increasing the strength of the weld.

[0059] 9, the protrusions 113 of the second wall 21b are portions that protrude due to melting of the second wall 21b. The protrusions 113 may protrude in the direction in which the second surface 20b of the core layer 20 (the surface to be joined to the second skin layer 40) extends, or may protrude in a direction intersecting with the second surface 20b. The protrusions 113 enable the core layer 20 to be welded to the second skin layer 40 more reliably.

[0060] Similarly, the second folded portion 25b may be heated or pressed to form a protrusion 112 protruding from the second folded portion 25b. The protrusion 112 serves as a portion that welds the second partition wall 23b (second folded portion 25b) to the first skin layer 30. This increases the welding area of ​​the core layer 20 to the first skin layer 30, thereby increasing the strength of the weld.

[0061] By making the protrusions 111 and 112 protrude from the folded portions 25a and 25b, respectively, the opening areas of the first and second openings 27a and 27b can be narrowed, thereby improving the welding strength of the skin layers 30 and 40.

[0062] The skin layers 30, 40 may be attached to both sides of the core layer 20 with an adhesive. In this case, the adhesive may be applied to the sheets that will become the skin layers 30, 40, or to the core layer 20.

[0063] The skin layers 30, 40 may be made of, for example, nonwoven fabric. Alternatively, nonwoven fabric may be attached to the outer surface of the skin layers 30, 40. The hollow structure 10 may have through-holes that penetrate at least one of the core layer 20 and the skin layers 30, 40 in the thickness direction (Z direction).

[0064] The shape of the cells S of the hollow structure 10 is not limited to a hexagonal prism, but may be, for example, any polygonal prism, a circular prism, or an elliptical prism. As in a fifth modified example shown in FIG. 10 , the outer edge of the hollow structure 10 may be crushed so as to bring the first skin layer 30 closer to the second skin layer 40. At this time, the outer edge of the first skin layer 30 and the outer edge of the first wall 21a curve so as to approach the first skin layer 30. At the crushed outer edge portion 105, the first skin layer 30, the first wall 21a, and the partition wall 23 are integrated and become solid. At this time, the first partition wall 23a is crushed near the first end, where it is thickest. Therefore, the strength of the solid outer edge portion 105 is higher and the surface of the outer edge portion 105 is smoother than when the first partition wall 23a is crushed near the second end, where it is relatively thinner.

[0065] The technical concepts that can be understood from the above embodiment are listed below. (1) A hollow structure having a plurality of cells, the hollow structure comprising: a core layer having a plurality of first walls, a plurality of second walls, and a plurality of partition walls; First and second skin layers bonded to both sides of the core layer, respectively; Equipped with the plurality of cells includes a plurality of first cells and a plurality of second cells; each of the first cells is defined by the first wall and a plurality of the partition walls extending from the first wall; Each of the second cells is defined by the second wall and a plurality of the partition walls extending from the second wall, the plurality of first cells arranged in one direction constitute a first cell row, and the plurality of second cells arranged in the one direction constitute a second cell row; The plurality of partition walls are a plurality of first partition walls having a two-layer structure positioned between adjacent first cells in the first cell row; a plurality of second partition walls having a two-layer structure located between adjacent second cells in the second cell row, the first partition wall has a first joint portion at an end closer to the first wall where two layers constituting the first partition wall are joined to each other, and a first folded portion at an end farther from the first wall; the second partition wall has a second joint portion at an end closer to the second wall where two layers constituting the second partition wall are joined to each other, and a second folded portion at an end farther from the second wall; The bonding strength of the first bonding portion is greater than the bonding strength of the second bonding portion, the thickness of the first wall is greater than the thickness of the second wall; the first cell rows and the second cell rows are alternately arranged along a direction intersecting the one direction, the two layers constituting the first partition wall are welded to each other at the first joint, The two layers constituting the second partition wall are welded to each other at the second joint. hollow structure.

[0066] (2) The plurality of cells arranged along a direction intersecting the one direction are arranged in a serpentine manner, and each of the cells arranged in a serpentine manner maintains a hexagonal prism shape. The hollow structure according to (1) above.

[0067] (3) The second partition wall has a protruding portion protruding from the second folded portion along the first skin layer, and the protruding portion is welded to the first skin layer. The hollow structure according to (1) above.

[0068] (4) the thickness of the first wall is at least twice the thickness of the second wall; The thickness of the partition wall gradually increases from the second wall toward the first wall. The hollow structure according to (1) above.

[0069] (5) At least a portion of the hollow structure is curved such that the outer surface defined by the first skin layer is a convex surface and the outer surface defined by the second skin layer is a concave surface. The hollow structural body according to any one of (1) to (4) above.

[0070] (6) A luggage board having the hollow structure described in any one of (1) to (5) above.

Claims

1. A hollow structure having a plurality of cells, the hollow structure comprising: a core layer having a plurality of first walls, a plurality of second walls, and a plurality of partition walls; first and second skin layers bonded to both sides of the core layer, respectively; Equipped with the plurality of cells includes a plurality of first cells and a plurality of second cells; Each of the first cells is defined by the first wall and a plurality of the partition walls extending from the first wall, each second cell is defined by the second wall and a plurality of the partition walls extending from the second wall; the plurality of first cells aligned in one direction constitute a first cell row, and the plurality of second cells aligned in the one direction constitute a second cell row; The plurality of partition walls are a plurality of first partition walls having a two-layer structure positioned between adjacent first cells in the first cell row; a plurality of second partition walls having a two-layer structure located between adjacent second cells in the second cell row, the first partition wall has a first joint portion at an end closer to the first wall, where two layers constituting the first partition wall are joined to each other, and a first folded portion at an end farther from the first wall; the second partition wall has a second joint portion at an end closer to the second wall where two layers constituting the second partition wall are joined to each other, and a second folded portion at an end farther from the second wall; a bonding strength of the first bonding portion is greater than a bonding strength of the second bonding portion; The thickness of the first wall is greater than the thickness of the second wall; the first cell rows and the second cell rows are alternately arranged along a direction intersecting the one direction, the two layers constituting the first partition wall are welded to each other at the first joint, the two layers constituting the second partition wall are welded to each other at the second joint, the thickness of the first wall is at least twice the thickness of the second wall; The thickness of the partition wall gradually increases from the second wall toward the first wall. hollow structure.

2. The plurality of cells arranged along a direction intersecting the one direction are arranged in a serpentine manner, and each of the cells arranged in a serpentine manner maintains a hexagonal prism shape. The hollow structure according to claim 1 .

3. The second partition wall has a protrusion protruding from the second folded portion along the first skin layer. and the protrusion is welded to the first skin layer. The hollow structure according to claim 1 .

4. At least a portion of the hollow structure is curved such that an outer surface defined by the first skin layer is convex and an outer surface defined by the second skin layer is concave. The hollow structure according to any one of claims 1 to 3.

5. A luggage board comprising the hollow structure according to any one of claims 1 to 4.

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