Panel manufacturing method

Abstract

A method for manufacturing a panel is provided, comprising an extrusion step, a shaping step, an insertion step, and a mold closing step. In the extrusion step, a first resin sheet and a second resin sheet are extruded between a first mold and a second mold, with the second resin sheet disposed between the first resin sheet and the second mold. In the shaping step, the first resin sheet and the second resin sheet are shaped along the cavity surfaces of the first mold and the second mold, respectively. In the insertion step, a foam material is disposed between the first resin sheet and the second resin sheet. In the mold closing step, the first mold and the second mold are closed. The mold, the second mold has a protrusion forming a hinge portion. At the front end of the protrusion, a groove and a first protrusion and a second protrusion corresponding to the first hinge and the second hinge are provided. The groove corresponds to the middle portion and is disposed between the first protrusion and the second protrusion. In the mold closing process, the hinge portion is formed by compressing the first resin sheet, the second resin sheet and the foam body sandwiched between the front end of the protrusion and the first mold. If the depth of the groove is set as Dg and the thickness of the second resin sheet is set as Ts2, then the value of Dg / Ts2 is 1.5 to 3.

Description

Technical Field

[0001] The present invention relates to a panel that can be used as a bathtub cover, a floor board installed in the trunk of a vehicle, etc. Background Technology

[0002] Patent document 1 discloses a panel with a hollow double-walled intermediate section (support) between a pair of hinges. Such a panel can be folded at the hinges.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-46168

[0006] Patent Document 2: WO2013 / 077198 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The panel of Patent Document 1 can be formed by vacuum molding a pair of resin sheets as disclosed in Patent Document 2. However, in this case, pressurized air may sometimes remain in the enclosed space in the middle. If pressurized air remains in this area, a bubble-like expansion may sometimes form at the boundary between the middle and the hinge due to the air.

[0009] To avoid such problems, a solution was considered: inserting a hollow pin into the middle section during molding to prevent pressurized air from remaining in the enclosed space of the middle section. However, when the size of the middle section is small, inserting a hollow pin is not easy, making it difficult to implement such a solution.

[0010] The present invention was made in view of the following situation, and provides a method for manufacturing a panel that can suppress the formation of a bubble-like expansion portion at the boundary between the middle portion and the hinge, even when the size of the middle portion is small.

[0011] means for solving problems

[0012] According to the present invention, a method for manufacturing a panel is provided. The panel has a first main body portion, a second main body portion, and a hinge portion. The hinge portion has a first hinge and a second hinge extending in parallel and an intermediate portion between the first hinge and the second hinge. The first main body portion and the intermediate portion are connected to each other in a rotatable manner via the first hinge. The second main body portion and the intermediate portion are also connected to each other in a rotatable manner via the second hinge. The method includes an extrusion step, a shaping step, an insertion step, and a mold closing step. In the extrusion step, a first resin sheet and a second resin sheet are extruded between a first mold and a second mold. The second resin sheet is disposed between the first resin sheet and the second mold. In the shaping step, the first resin sheet and the second resin sheet are separated... The molding process involves shaping along the cavity surfaces of the first and second molds. In the insertion process, a foam is placed between the first and second resin sheets. In the mold closing process, the first and second molds are closed. The second mold has a protrusion forming the hinge portion. At the front end of the protrusion, a groove and a first and a second protrusion corresponding to the first and second hinges are provided. The groove corresponds to the middle portion and is disposed between the first and second protrusions. In the mold closing process, the hinge portion is formed by compressing the first resin sheet, the second resin sheet, and the foam between the front end of the protrusion and the first mold. If the depth of the groove is set as Dg and the thickness of the second resin sheet is set as Ts2, then the value of Dg / Ts2 is 1.5 to 3.

[0013] The inventors of this application conducted in-depth research and discovered that by sandwiching a foam body between a first resin sheet and a second resin sheet and compressing it to form a hinge portion having a first hinge, a second hinge, and an intermediate portion therebetween, the formation of an expansion portion at the boundary between the intermediate portion and the hinge can be suppressed even without inserting a hollow pin into the intermediate portion, thus completing the present invention. The effect of suppressing the formation of the expansion portion can be attributed to the fact that air becomes more easily able to escape through the foam body during molding, making it difficult for pressurized air to remain in the intermediate portion.

[0014] The following examples illustrate various embodiments of the present invention. These embodiments can be combined with each other.

[0015] Preferably, in the described method, if the thickness of the foam at the portion facing the protrusion is set as Tc, then the value of Tc / Ts2 is 2 to 6.

[0016] Preferably, in the described method, if the width of the groove is set to Wg, then the value of Wg / Dg is 2.5 to 4. Attached Figure Description

[0017] Figure 1A This is the rear view of panel 1. Figure 1B yes Figure 1A CC section view in the image.

[0018] Figure 2A yes Figure 1A A magnified view of region A in the image. Figure 2B yes Figure 1B A magnified view of region B in the image.

[0019] Figure 3 This is a structural diagram of the molding machine 10 that can be used in the manufacture of panel 1 (the molds 21, 31 and the components nearby are longitudinal sectional views).

[0020] Figure 4 It is a cross-sectional view showing the state of extruding resin sheets 23 and 33 between molds 21 and 31.

[0021] Figure 5 yes Figure 4 An enlarged view of region A in the image.

[0022] Figure 6 It shows from Figure 4 The state is a cross-sectional view of the state after the resin sheets 23 and 33 are shaped along the inner surface of the cavity of the mold 21 and 31.

[0023] Figure 7 It shows from Figure 6 The cross-sectional view of the state after the foam 37 is attached to the resin sheet 23.

[0024] Figure 8 The diagram shows the state during the mold closing process, and the state of the portions 33a and 33b of the resin sheet 33 that cover the protrusions 35a and 35b just after they come into contact with the foam 37.

[0025] Figure 9 yes Figure 8 An enlarged view of region A in the image.

[0026] Figure 10 This shows the state of parts 33a and 33b just after they come into contact with resin sheet 23 during the molding process, without foam 37 between resin sheets 23 and 33.

[0027] Figure 11 This is a photograph showing the state in which a bubble-like expansion portion 9 is formed at the boundary between the middle portion 5c and the hinges 5a and 5b. Detailed Implementation

[0028] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. The various features in the embodiments shown below can be combined with each other. Furthermore, each feature can independently constitute an invention.

[0029] 1. Panel 1

[0030] First, a panel 1 that can be manufactured by a panel manufacturing method according to an embodiment of the present invention will be described. As shown in Figures 1 and 2, the panel 1 has a first main body portion 2a, a second main body portion 2b, and a hinge portion 5.

[0031] The main body parts 2a and 2b are molded bodies in the shape of a panel. The panel 1 has a surface wall 3 and a back wall 4. The surface wall 3 and the back wall 4 face each other with a gap between them. The surface wall 3 and the back wall 4 are connected by a peripheral wall 6.

[0032] The surface of the surface wall 3 is flat. The hinge portion 5 is formed by the back wall 4 being recessed toward the surface wall 3. On the back wall 4, an inclined portion 4a is provided at a position adjacent to the hinge portion 5, in which the gap between the surface wall 3 and the back wall 4 narrows toward the hinge portion 5.

[0033] A skin material 8 is provided on the surface wall 3 side of the panel 1. The skin material 8 is provided on the surface wall 3 side of the panel 1 in a manner that spans the main body 2a, the hinge part 5, and the main body 2b. The skin material 8 is preferably made of a breathable carpet-like component such as non-woven fabric, and is preferably integrally formed with the surface wall 3 during the molding of the panel 1.

[0034] The thickness of the surface wall 3 and the back wall 4 at the main body 2a and 2b is, for example, 0.5 to 2 mm, specifically, for example, 0.5, 1.0, 1.5, 2.0 mm, or it can be within any two values ​​shown in this example.

[0035] A foam 7 is provided between the surface wall 3 and the back wall 4. The foam 7 has the function of ensuring the space between the surface wall 3 and the back wall 4, thereby improving the strength and thermal insulation of the panel 1.

[0036] The hinge portion 5 has a first hinge 5a, a second hinge 5b extending in parallel, and an intermediate portion 5c between them. The first main body portion 2a and the intermediate portion 5c are connected to each other in a rotatable manner via the first hinge 5a, and the second main body portion 2b and the intermediate portion 5c are connected to each other in a rotatable manner via the second hinge 5b. Therefore, the main body portions 2a and 2b are connected to each other in a rotatable manner via the hinge portion 5.

[0037] The cross-section of the middle part 5c is approximately trapezoidal, and the thickness of the middle part 5c gradually decreases towards the end in the width direction of the middle part 5c. Therefore, the middle part 5c is smoothly connected to the hinges 5a and 5b.

[0038] The thickness of hinges 5a and 5b is, for example, 0.001 to 0.5 mm, specifically, for example, 0.001, 0.01, 0.1, 0.2, 0.3, 0.4, or 0.5 mm, or may be within the range of any two values ​​shown in this example. The width of hinges 5a and 5b is, for example, 0.5 to 3 mm, specifically, for example, 0.5, 1.0, or...

[0039] 1.5, 2.0, 2.5, 3.0 mm, or any two values ​​shown in this example.

[0040] If the thickness of the intermediate portion 5c is set to Ti, then Ti is 1.5 to 3 mm, specifically, for example, 1.5, 2.0, 2.5, or 3.0 mm, or any value between any two values ​​shown in this example. If the width of the intermediate portion 5c is set to Wi, then Wi is, for example, 4 to 8 mm, specifically, for example, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, or 8.0 mm, or any value between any two values ​​shown in this example. Furthermore, the value of Wi / Ti is, for example, 1.5 to 5, preferably 2.5 to 4, specifically, for example, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, or any value between any two values ​​shown in this example.

[0041] If the thickness of the back wall 4 at the main body 2a and 2b is set as Tr, then the value of Ti / Tr is, for example, 1.5 to 3, specifically, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, or it can be within the range of any two values ​​shown in this example.

[0042] Furthermore, in this application specification, the thickness of hinges 5a, 5b, and the intermediate portion refers to the thickness excluding the thickness of the outer skin material 8. Additionally, unless otherwise specified, the thickness and width of various components refer to average values.

[0043] 2. Molding machine 10

[0044] Next, use Figures 3-5 The molding machine 10 described above is used to implement the manufacturing method of panel 1. The molding machine 10 has a pair of resin sheet forming devices 20, a first mold 21, and a second mold 31. Each resin sheet forming device 20 has a hopper 12, an extruder 13, an accumulator 17, and a T-die 18. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the T-die 18 are connected via a connecting pipe 27.

[0045] The following is a detailed explanation of each structure.

[0046] <Hopper 12, Extruder 13>

[0047] The hopper 12 is used to feed the raw material resin 11 into the cylinder 13a of the extruder 13. The form of the raw material resin 11 is not particularly limited, and it is usually granular. The raw material resin is, for example, a thermoplastic resin such as a polyolefin; examples of polyolefins include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymers, and mixtures thereof. After the raw material resin 11 is fed from the hopper 12 into the cylinder 13a, it is melted by heating within the cylinder 13a, becoming molten resin. Furthermore, it is conveyed towards the front end of the cylinder 13a by the rotation of a screw disposed within the cylinder 13a. The screw, disposed within the cylinder 13a, mixes and conveys the molten resin while rotating.

[0048] <Accumulator 17, T-mode 18>

[0049] Molten resin is extruded from the resin extrusion port of cylinder 13a, passes through connecting pipe 25, and is injected into accumulator 17. Accumulator 17 has cylinder 17a and piston 17b that can slide inside it, and molten resin can accumulate in cylinder 17a. Moreover, after a predetermined amount of molten resin has accumulated in cylinder 17a, piston 17b is moved, thereby causing molten resin to be extruded through connecting pipe 27 from a slit provided in T-mold 18, forming a first resin sheet 23 and a second resin sheet 33 in a molten state.

[0050] <Mold 21, 31>

[0051] With the molds 21 and 31 open, resin sheets 23 and 33 are extruded between the molds 21 and 31. Figure 4 As shown, molds 21 and 31 have cavity surfaces 21a and 31a, and clamping portions 21b and 31b are provided to surround the cavity surfaces 21a and 31a. Pressure-reducing suction holes (not shown) are provided within the cavity surfaces 21a and 31a, through which pressure-reducing suction can be applied to the resin sheets 23 and 33, shaping them into shapes along the cavity surfaces 21a and 31a. The thickness of the resin sheets 23 and 33 is, for example, 0.5 to 2 mm, specifically, for example, 0.5, 1.0, 1.5, or 2.0 mm, or within any two values ​​shown herein.

[0052] A protrusion 35 forming the hinge portion 5 is provided on the mold 31. The protrusion 35 is an elongated protrusion, preferably configured such that the length direction of the protrusion 35 is not parallel to the extrusion direction of the resin sheets 23 and 33, and more preferably, the length direction of the protrusion 35 is orthogonal to the extrusion direction of the resin sheets 23 and 33. In this case, the variation in the thickness of the resin sheets 23 and 33 along the length direction of the hinge portion 5 is suppressed.

[0053] like Figure 5 As shown, a first protrusion 35a and a second protrusion 35b corresponding to hinges 5a and 5b are provided at the front end of the protrusion 35, and a groove 35c corresponding to the middle part 5c and disposed between the protrusions 35a and 35b. The width of the protrusions 35a and 35b is, for example, 0.5 to 3 mm, specifically, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mm, or it can be within the range of any two values ​​shown in this example.

[0054] The groove 35c is approximately trapezoidal. If the depth of the groove 35c is set as Dg, then Dg is 1.5 to 3 mm, specifically, for example, 1.5, 2.0, 2.5, or 3.0 mm, or any value between any two values ​​shown in this example. If the width of the groove 35c is set as Wg, then Wg is, for example, 4 to 8 mm, specifically, for example, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, or 8.0 mm, or any value between any two values ​​shown in this example. Furthermore, the value of Wg / Dg is, for example, 1.5 to 5, preferably 2.5 to 4, specifically, for example, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, or any value between any two values ​​shown in this example.

[0055] If the thickness of the resin sheet 33 is set as Ts2, then the value of Dg / Ts2 is, for example, 1.5 to 3, specifically, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, or it can be within the range of any two values ​​shown in this example.

[0056] 3. Manufacturing method of panel 1

[0057] Here, use Figures 4-9 This section describes a method for manufacturing panel 1 according to an embodiment of the present invention. The method of this embodiment includes an extrusion process, a shaping process, an insertion process, and a mold closing process. These will be described in detail below.

[0058] (1) Extrusion process

[0059] like Figure 4As shown, in the extrusion process, resin sheets 23 and 33 are extruded between molds 21 and 31. Resin sheet 33 is disposed between resin sheet 23 and mold 31. A skin material sheet 38 is disposed between mold 21 and resin sheet 23. The skin material sheet 38 can be omitted if it is not needed.

[0060] (2) Shaping process

[0061] like Figure 6 As shown, in the shaping process, resin sheets 23 and 33 are shaped along the cavity surfaces 21a and 31a of molds 21 and 31, respectively. This process can be performed by depressurizing and drawing the resin sheets 23 and 33 using molds 21 and 31. While the resin sheet 23 is being shaped, the skin material sheet 38 is also being shaped along the cavity surface 21a.

[0062] (3) Insertion process

[0063] like Figures 6-7 As shown, in the insertion process, a foam body 37 is disposed between resin sheets 23 and 33. Preferably, the foam body 37 is fused to the resin sheet 23. The foam body 37 is constructed by connecting the first main body portion 37a and the second main body portion 37b through a connecting portion 37c. The main body portions 37a and 37b are respectively housed within the main body portions 2a and 2b of the panel 1. The connecting portion 37c corresponds to the hinge portion 5. The foam body 37 is arranged such that the connecting portion 37c faces the protrusion 35. If the thickness of the connecting portion 37c is set as Tc, then Tc is, for example, 2 to 6 mm, specifically, for example, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 mm, or it can be within any two values ​​shown in this example. In addition, the value of Tc / Ts2 can be, for example, 2 to 6, specifically, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, or it can be within any range of two values ​​shown in this example.

[0064] The expansion ratio of the foam 37 is, for example, 3 to 50 times, preferably 20 to 50 times. Specifically, the expansion ratio is, for example, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 times, or may be within the range of any two values ​​shown herein. Examples of materials for the foam 37 include polyolefins, polystyrene, or alloys thereof.

[0065] (4) Mold closing process

[0066] In the mold closing process, molds 21 and 31 are closed.

[0067] Figures 8-9The diagram shows the state midway through the mold-closing process, specifically the state immediately after the portions 33a and 33b of the resin sheet 33 covering the protrusions 35a and 35b come into contact with the foam body 37. At this point, the space enclosed by the resin sheet 33 and the foam body 37 becomes a closed space S. If the mold is further closed in this state, the portions of the foam body 37 facing the portions 33a and 33b are melted, and the portions of the foam body 37 facing the closed space S enter the closed space S, attempting to compress the air within it. However, the foam body 37 has a certain degree of permeability; therefore, the air within the closed space S can pass through the foam body 37 and escape. Thus, the pressurization of the air within the closed space S can be prevented.

[0068] If molds 21 and 31 are from Figures 8-9 The mold is further closed, and the resin sheets 23 and 33 are fused together along the clamping portions 21b and 31b to obtain a panel 1 shaped along the inner surface of the cavity formed by the pair of molds 21 and 31. Between the ridge 35 and the mold 21, the resin sheets 23 and 33 and the foam 37 (more specifically, the connecting portion 37c) are compressed to form the hinge portion 5. The portions compressed by the protrusions 35a and 35b at the front end of the ridge 35 become hinges 5a and 5b, and the portions facing the groove 35c become the middle portion 5c. The skin material sheet 38 becomes the skin material 8. The portions on the outer side of the clamping portions 21b and 31b become burrs. Then, the molds 21 and 31 are opened and the panel 1 is removed, and the burrs are removed, thereby obtaining the panel 1 shown in FIG. 1.

[0069] For comparison, when there is no foam 37 between resin sheets 23 and 33, the state of parts 33a and 33b immediately after contact with resin sheet 23 during the mold closing process is as follows: Figure 10 As shown. In this configuration, there is no foam 37, therefore, a closed space S is formed by the contact between parts 33a and 33b and the resin sheet 23. If the mold is further closed in this state, parts 33a and 33b, as well as the parts of the resin sheet 23 facing parts 33a and 33b, are compressed by the protrusions 35a and 35b and the mold 21, and the parts of the resin sheet 23 facing the closed space S enter the closed space S, compressing the air in the closed space S. Since the air in the closed space S cannot escape through the resin sheets 23 and 33, the air in the closed space S is directly compressed and remains in the middle part 5c as pressurized air. Moreover, if the panel 1 is removed from the mold 21 and 31, then as Figure 11 As shown, due to the pressurized air within the intermediate portion 5c, a bubble-like expansion portion 9 is formed at the boundary between the intermediate portion 5c and the hinges 5a and 5b. In this embodiment, as described above, by distributing the foam 37 between the resin sheets 23 and 33, the residual pressurized air within the intermediate portion 5c is suppressed, and the formation of the expansion portion 9 is also suppressed.

[0070] Example

[0071] 1. Manufacturing of Panel 1

[0072] Example 1

[0073] The panel 1 with the shape shown in the above embodiment is manufactured according to the above method. Detailed manufacturing conditions are as follows.

[0074] • Thickness of resin sheets 23 and 33: 1mm

[0075] • Materials for resin sheets 23 and 33: 50% polypropylene, 30% HDPE (High Density Polyethylene), 20% talc.

[0076] • Width of protrusions 35a and 35b: 1mm

[0077] • Depth of groove 35c: 2mm, Width of groove 35c: 6mm

[0078] • Thickness of the connecting portion 37c of foam 37: 4mm

[0079] • Material of foam 37: PIOCELAN (manufactured by Sekisui Chemicals Co., Ltd.), an alloy of polyester and polystyrene.

[0080] • Foaming ratio of foam 37: 35 times

[0081] • Outer Material Sheet 38: 1mm thick non-woven fabric

[0082] Comparative Example 1

[0083] Except for the fact that the foam is not placed between the resin sheets 23 and 33, the panel 1 is manufactured in the same manner as in Example 1.

[0084] • See Example 1

[0085] Except for modifying the protrusions 35a, 35b and the groove 35c in the following ways, panel 1 was manufactured in the same manner as in Comparative Example 1.

[0086] • Depth of groove 35c: 1mm, Width of groove 35c: 2mm

[0087] 2. Evaluation of Panel 1

[0088] Visually inspecting each panel 1, it was confirmed whether an expansion portion 9 was formed. In panel 1 of Embodiment 1, no expansion portion 9 was formed. On the other hand, in panel 1 of Comparative Example 1, an expansion portion 9 was formed. Figure 11The expansion portion 9 is shown as shown. This result shows that by molding the panel 1 with the foam 37 disposed between the resin sheets 23 and 33, the formation of the expansion portion 9 can be suppressed.

[0089] Furthermore, no expansion portion 9 was formed in Reference Example 1. This result shows that when the depth of the groove 35c is less than or equal to the thickness of the resin sheet 33, even if the air in the enclosed space S is pressurized, the degree of pressurization is small, and no expansion portion 9 is formed. That is, the formation of the expansion portion 9 can occur only when the value of (depth of groove 35c / thickness of resin sheet 33) is within a specific range.

[0090] Explanation of reference numerals in the attached figures

[0091] 1: Panel; 2a: First main body; 2b: Second main body; 3: Surface wall; 4: Back wall; 4a: Inclined part; 5: Hinge part; 5a: First hinge; 5b: Second hinge; 5c: Middle part; 6: Peripheral wall; 7: Foam body; 8: Skin material; 9: Expansion part; 10: Molding machine; 11: Raw material resin; 12: Hopper; 13: Extruder; 13a: Cylinder; 17: Accumulator; 17a: Cylinder; 17b: Piston; 18: T-die; 20: Resin sheet forming device; 21: First mold, 21a: cavity surface, 21b: clamping part, 23: first resin sheet, 25: connecting tube, 27: connecting tube, 31: second mold, 31a: cavity surface, 31b: clamping part, 33: second resin sheet, 33a: part, 33b: part, 35: protrusion, 35a: first protrusion, 35b: second protrusion, 35c: groove, 37: foam, 37a: first main body, 37b: second main body, 37c: connecting part, 38: skin material sheet, S: closed space.

Claims

1. A method of manufacturing a panel, wherein the panel has a first main body portion, a second main body portion, and a hinge portion, the hinge portion has first and second hinges extending in parallel and an intermediate portion between the first and second hinges, the first main body portion and the intermediate portion are joined by the first hinge so as to be rotatable relative to each other, the second main body portion and the intermediate portion are joined by the second hinge so as to be rotatable relative to each other, the method has an extrusion process, a shaping process, an insertion process, and a mold closing process, in the extrusion process, a first resin sheet and a second resin sheet are extruded between a first mold and a second mold, the second resin sheet is disposed between the first resin sheet and the second mold, in the shaping process, the first and second resin sheets are shaped along cavity surfaces of the first and second molds, respectively, in the insertion process, a foamed body is disposed between the first and second resin sheets, in the mold closing process, the first and second molds are closed, the second mold has a ridge that forms the hinge portion, at a front end of the ridge, a groove and first and second protrusions corresponding to the first and second hinges are provided, the groove corresponding to the intermediate portion and being disposed between the first and second protrusions, in the mold closing process, the hinge portion is formed by compressing the first resin sheet, the second resin sheet, and the foamed body between the front end of the ridge and the first mold, if a depth of the groove is set as Dg and a thickness of the second resin sheet is set as Ts2, a value of Dg / Ts2 is 1.5 to 3, if a thickness of the foamed body at a portion facing the ridge is set as Tc, a value of Tc / Ts2 is 2 to 6.

2. The method of manufacturing a panel according to claim 1, wherein if a width of the groove is set as Wg, a value of Wg / Dg is 2.5 to 4.

Images