Mold unit for producing hydroponic panels, method for producing hydroponic panels, and hydroponic tray and conveyance method therefor

Abstract

Provided is a mold unit with which it is possible to produce multiple kinds of hydroponic panels which differ in the number of holes.　The present invention provides a mold unit for producing hydroponic panels, the mold unit comprising first and second molds configured so as to be openable and closable. The first and second molds each comprise a mold main body and have a cavity surface provided with a plurality of piece attachment holes. The piece attachment holes are configured so that either a hole formation piece for forming a hole for young-plant insertion or a closing piece for closing the piece attachment hole is attachable to each piece attachment hole. By changing the number of hole formation pieces to be attached to the piece attachment holes, it is possible to change the number of holes for young-plant insertion formed in the hydroponic panel.

Description

Mold unit for manufacturing hydroponic cultivation panels, manufacturing method for hydroponic cultivation panels, hydroponic cultivation tray and method for transporting the same

[0001] The present invention relates to a mold unit for manufacturing a hydroponic cultivation panel, a method for manufacturing a hydroponic cultivation panel, a tray for hydroponic cultivation, and a method for transporting the same.

[0002] (First Aspect) Patent Document 1 discloses a hydroponic cultivation panel having a hole formed therein into which a cultivated object is inserted, the cultivated object being planted in a seedbed member.

[0003] (Second Aspect) Patent Literature 2 discloses a cultivation device for hydroponically cultivating plants. In this cultivation device, a cultivation tank for holding a cultivation solution for growing plants is placed on a cultivation unit and transported by a conveyor device.

[0004] Japanese Patent Application Laid-Open No. 9-103203 Japanese Patent Application Laid-Open No. 2022-23725

[0005] (First Aspect) Hydroponic cultivation panels may be required to have different numbers of holes for inserting cultivated plants depending on the type of cultivated plant, the cultivation environment, etc. Hydroponic cultivation panels are usually manufactured by molding using a mold, and from the standpoint of manufacturing costs, etc., it is desirable to use a common mold to manufacture multiple types of hydroponic cultivation panels with different numbers of holes. However, since different numbers of holes require different shapes of the mold, it is not easy to standardize the mold.

[0006] The present invention has been made in view of the above circumstances, and provides a mold unit capable of manufacturing a plurality of types of hydroponic cultivation panels having different numbers of holes.

[0007] (Second aspect) In Patent Document 2, the cultivation units are transported using a conveyor device that has a built-in drive unit such as a motor, but such conveyor devices have the problem of high installation and maintenance costs, so it is desirable to transport the cultivation units horizontally using a free conveyor that does not have a built-in drive unit.

[0008] The present invention has been made in view of the above circumstances, and provides a tray for hydroponic cultivation that can be transported horizontally using a free conveyor.

[0009] (First Aspect) According to the present invention, the following inventions are provided: [1] A mold unit for manufacturing a hydroponic cultivation panel, the mold unit comprising first and second molds configured to be openable and closable, each of the first and second molds comprising a mold body, a plurality of piece mounting holes formed in a cavity surface of the mold body, the piece mounting holes configured to accommodate both hole-forming pieces for forming plant insertion holes and closing pieces for closing the piece mounting holes, and the number of plant insertion holes formed in the hydroponic cultivation panel can be changed by changing the number of hole-forming pieces attached to the piece mounting holes. [2] The mold unit according to [1], wherein the piece mounting holes of the mold body of the first mold and the piece mounting holes of the mold body of the second mold are positioned opposite each other. [3] The mold unit according to [2], wherein the hole forming pieces to be attached to the piece mounting holes of the first mold and the hole forming pieces to be attached to the piece mounting holes of the second mold have the same shape. [4] A method for manufacturing a hydroponic cultivation panel using the mold unit according to any one of [1] to [3], comprising a first manufacturing step and a second manufacturing step, in which the hydroponic cultivation panel is manufactured using the mold unit in a first state, in which the first state is a state in which the numbers of the hole forming pieces and the closing pieces to be attached to the piece mounting holes are each a first predetermined number, and in the second manufacturing step, the hydroponic cultivation panel is manufactured using the mold unit in a second state, in which the numbers of the hole forming pieces and the closing pieces to be attached to the piece mounting holes are each a second predetermined number, and the second predetermined number is a number different from the first predetermined number.

[0010] (Second Aspect) According to the present invention, the following inventions are provided. [1] A tray for hydroponic cultivation, the tray having a bottom and side portions rising to surround the bottom, the tray having an inner wall disposed inside the tray and an outer wall disposed outside the inner wall, the side portions being provided with engagement recesses formed by the outer wall being recessed upward, the engagement recesses having an inner wall and an outer wall, the inner wall and the outer wall being a pair of side walls of the engagement recess, the inner wall being disposed inside the tray relative to the outer wall. [2] The tray according to [1], the tray having a first welded portion formed on the inner wall, where the inner wall and the outer wall are welded to each other. [3] The tray according to [1] or [2], wherein, when a direction in which the inner wall and the outer wall face each other is defined as a first direction, the engagement recesses extend in a second direction perpendicular to the first direction. [4] The tray according to any one of [1] to [3], wherein, when the direction in which the inner wall and the outer wall face each other is defined as a first direction, a reinforcing recess extending in the first direction is provided at a position adjacent to the engagement recess. [5] The tray according to [4], wherein a second welded portion where the inner wall and the outer wall are welded to each other is provided at the bottom of the reinforcing recess. [6] The tray according to [4] or [5], wherein a pair of the reinforcing recesses is provided at a position adjacent to the engagement recess. [7] A method for transporting a tray according to any one of [1] to [6], wherein the tray is transported by moving a hook attached to a driving device in the direction of the inner wall or the outer wall with the tip of the hook engaged with the engagement recess.

[0011] (First Aspect) In the mold unit of the present invention, both hole-forming pieces and closing pieces can be attached to the piece mounting holes, and the hole-forming pieces can be attached to the piece mounting holes for the desired number of plant insertion holes, and the remaining piece mounting holes can be closed with closing pieces. This configuration makes it possible to manufacture multiple types of hydroponic panels with different numbers of holes. Furthermore, because the piece mounting holes are closed with closing pieces, it is possible to prevent the molding material from getting into piece mounting holes that do not have hole-forming pieces attached.

[0012] (Second Aspect) In the hydroponic cultivation tray of the present invention, a first welding portion is provided on the inner wall of the engagement recess into which the hook attached to the drive device engages, whereby the inner wall and the outer wall are welded together. With this configuration, the hook of the drive device can be engaged with the engagement recess to push and pull the tray. Therefore, for example, by arranging multiple trays in series on a free conveyor and pushing one end tray horizontally, all of the trays in the series can be moved simultaneously. Furthermore, by pulling the other end tray horizontally, the trays on the free conveyor can be removed from the conveyor. Therefore, according to the present invention, a hydroponic cultivation tray that can be transported horizontally using a free conveyor is provided.

[0013] (First View) A perspective view of a hydroponic cultivation panel 40. FIG. 2A is a cross-sectional view taken along line A-A in FIG. 1. FIG. 2B is an enlarged view of region B in FIG. 2A. FIG. 2C is a cross-sectional view corresponding to FIG. 2B, showing a state in which the panel 40, with cultivated plants 34 inserted into the cultivated plant insertion holes 31, is floating on the nutrient solution 9. A perspective view showing an example of the configuration of a hydroponic cultivation panel 40 having 16 cultivated plant insertion holes 31. A perspective view of a mold unit 20. FIG. 5A is a cross-sectional view taken along line A-A in FIG. 4. FIG. 5B is an enlarged view of region B in FIG. 5A. FIG. 5C is an exploded view of FIG. 5B. FIGS. 6A to 6C are perspective views of the mold body 23, hole forming pieces 24, and closing pieces 25, respectively. FIG. 6D is an exploded perspective view of FIG. 6B. FIG. 7A is a perspective view showing an example of the configuration of a mold body 23 having 64 piece mounting holes 23c. FIG. 7B is a plan view showing the state in which, of the piece mounting holes 23c of the mold body 23 in FIG. 7A, 16 pieces for mounting the hole forming pieces 24 are surrounded by a thick line 26. FIGS. 8A and 8B are plan views showing the state in which, of the piece mounting holes 23c of the mold body 23 in FIG. 7A, 32 pieces and 48 pieces for mounting the hole forming pieces 24 are surrounded by a thick line 26, respectively. A cross-sectional view showing the state after the first and second resin sheets 35a, 35b are placed between the first mold 21 and the second mold 22 as the parison 35. A cross-sectional view showing the state after the first and second resin sheets 35a, 35b are shaped by the first and second molds 21, 22, as shown in FIG. 9. A cross-sectional view showing the state after the first and second molds 21, 22 are closed, as shown in FIG. 10. A cross-sectional view showing the state after the molded body 8 is removed from the first and second molds 21, 22, as shown in FIG. 11. Figures 13A to 13C are respectively a perspective view, a plan view, and a front view showing a modified example of the closing piece 25. Figure 14A is a cross-sectional view corresponding to Figure 5B, showing the closing piece 25 of Figure 13A attached to the mold body 23. Figure 14B is a cross-sectional view corresponding to Figure 2B, of a panel 40 manufactured using a mold unit 20 attached with the closing piece 25 of Figure 13A attached. Figure 14C is an enlarged view of region C in Figure 14B. Figures 15A to 15C are views corresponding to Figures 14A to 14C, showing the closing piece 25 attached to the mold body 23 so that the top surface 25c of the closing piece 25 protrudes from the cavity surface 23a.(Second Perspective) Figures 16A and 16B are perspective views of a hydroponic tray 10 and a hook 4 according to one embodiment of the present invention, viewed obliquely from above and below, respectively. Figure 17A is an enlarged view of region A in Figure 16B, and Figure 17B is a perspective view of the state after the hook 4 has been engaged with the engagement recess 2f from the state in Figure 17A. The dashed-dotted lines in the figures indicate changes in curvature. The same applies to the other figures. This is a bottom view of the tray 10 and the hook 4 in Figure 16. This is an enlarged view of region A in Figure 18. Figures 20A to 20C are cross-sectional views taken along lines A-A, B-B, and C-C in Figure 19, respectively. This shows the state after the hook 4 has been engaged with the engagement recess 2f from the state in Figure 20A. Figures 22A and 22B are cross-sectional views taken along lines D-D and E-E in Figure 19, respectively. Figures 23A and 23B are plan and front views, respectively, of a conveying device 5 for conveying trays 10.

[0014] Hereinafter, embodiments of the present invention will be described. Various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently. Furthermore, in the following embodiments, elements not specified in the claims are optional elements and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400".

[0015] (First Aspect) 1. Hydroponic Panel 40 First, a hydroponic panel 40 that can be manufactured using a hydroponic panel manufacturing mold unit 20 (described later) will be described with reference to FIGS.

[0016] 1 and 2, a hydroponic panel 40 according to one embodiment of the present invention is floated on a nutrient solution 9 for use in hydroponic cultivation, as shown in Fig. 2C. The panel 40 is preferably made of a hollow resin molded body. The interior of the hollow resin molded body may be hollow, or may contain a core material such as a foam.

[0017] The panel 40 is generally rectangular, with a short side dimension of, for example, 20 to 70 cm, a long side dimension of, for example, 50 to 120 cm, and a thickness of, for example, 20 to 40 mm. The short side dimension may be, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 cm, or may be within a range between any two of the values ​​exemplified herein. The long side dimension may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 cm, or may be within a range between any two of the values ​​exemplified herein. The thickness of the panel 40 may be, for example, 20, 25, 30, 35, or 40 mm, or may be within a range between any two of the values ​​exemplified herein.

[0018] The panel 40 is provided with a plant insertion hole 31 and a closing hole 32. The closing hole 32 will be described in detail later.

[0019] The plant inserting hole 31 is a hole for inserting the plant 34. The plant inserting hole 31 is provided to penetrate the panel 40 in the vertical direction. To facilitate retention of the plant 34 in the plant inserting hole 31, the plant P is preferably planted in a plug 50. The plug 50 is preferably made of an elastically deformable and water-absorbent material such as a sponge. The elastic force of the plug 50 presses the plug 50 against the inner surface of the plant inserting hole 31, thereby enabling the plant 34 to be retained in the plant inserting hole 31.

[0020] The panel 40 is provided with a plurality of plant insertion holes 31, and preferably the plurality of plant insertion holes 31 are arranged regularly. The spacing between adjacent plant insertion holes 31 is preferably, for example, 50 mm or more. This spacing is, for example, 50 to 200 mm, specifically, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 mm, and may be in a range between any two of the numerical values ​​exemplified here or greater than any one of them.

[0021] The colors and / or visible light reflectances (hereinafter, "reflectances") of the upper surface 40a and the lower surface 40b of the panel 40 may be the same or different. For example, one of the upper surface 40a and the lower surface 40b may be white and the other black. In this case, when floating the panel 40 on water, the black surface (low reflectance) faces the underwater side and the white surface (high reflectance) faces the surface, thereby suppressing the proliferation of algae in the water and promoting the growth of plants above the water. Furthermore, in low-temperature environments such as winter, the black surface (low reflectance) faces the surface, thereby increasing the temperature of the panel 40 through light absorption and reducing utility costs.

[0022] As shown in FIG. 2A, the panel 40 is preferably symmetrical with respect to the central plane CP in the vertical direction of the panel 40. This has the advantage that the panel 40 can be easily used by turning it upside down. In this case, the plant insertion holes 31 are also symmetrical with respect to the central plane CP. The opening diameter D1 on the upper surface 40a side or the lower surface 40b side is, for example, 20 to 60 mm. In this specification, "opening diameter" refers to the diameter of a circle. Specifically, D1 may be, for example, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mm, and may be within a range between any two of the values ​​exemplified here.

[0023] The plant insertion hole 31 preferably has a shape in which its diameter tapers from the upper surface 40a or the lower surface 40b toward the interior of the panel 40. In other words, the plant insertion hole 31 preferably has a shape in which two truncated cones are connected at their tips. If the smallest diameter of the plant insertion hole 31 is D2, then D2 / D1 is, for example, 0.40 to 0.95, and preferably 0.50 to 0.80. Specific examples of this value include 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and 0.95, and may be within a range between any two of the values ​​exemplified here.

[0024] The number of plant insert holes 31 is not particularly limited, and in one example, as shown in Fig. 3, 16 plant insert holes 31 are provided. On the other hand, there may be cases where panels 40 having the same external shape but different numbers of plant insert holes 31 are required. For example, there may be cases where panels 40 having 32 or 48 plant insert holes 31 are required. In such cases, preparing a mold for each panel 40 increases the costs required for mold production and mold management, so it is desirable to use a common mold to manufacture multiple types of panels 40 having different numbers of plant insert holes 31.

[0025] 2. Mold unit 20 for manufacturing hydroponic panels Next, a mold unit 20 for manufacturing hydroponic panels according to one embodiment of the present invention will be described with reference to Figures 4 to 8. The mold unit 20 has a configuration suitable for manufacturing multiple types of panels 40 each having a different number of plant insertion holes 31.

[0026] 4, the mold unit 20 has first and second molds 21 and 22 that are configured to be openable and closable. In this embodiment, the first and second molds 21 and 22 are symmetrical about the parting surface, but they may also be asymmetrical. Each of the first and second molds 21 and 22 has a mold body 23.

[0027] Each mold body 23 has a cavity surface 23 a. The cavity surface 23 a is surrounded by a pinch-off portion 23 b. The cavity surface 23 a of the first mold 21 and the cavity surface 23 a of the second mold 22 are joined together to form a cavity having a shape corresponding to the outer shape of the panel 40.

[0028] As shown in Figures 5C and 6A, the cavity surface 23a is provided with a plurality of piece mounting holes 23c. The piece mounting holes 23c are configured to accommodate both hole forming pieces 24 for forming the plant insertion holes 31 and closing pieces 25 for closing the piece mounting holes 23c. The number of plant insertion holes 31 formed in the hydroponic cultivation panel 40 can be changed by changing the number of hole forming pieces 24 attached to the piece mounting holes 23c. In this embodiment, the plurality of hole forming pieces 24 attached to the first mold 21 or the second mold 22 have the same shape, but pieces with different shapes may also be included. Similarly, the plurality of closing pieces 25 attached to the first mold 21 or the second mold 22 have the same shape, but pieces with different shapes may also be included.

[0029] The mechanism for attaching the hole forming piece 24 and the blocking piece 25 to the piece mounting hole 23c is not particularly limited, but since it is possible that the hole forming piece 24 attached to the piece mounting hole 23c may be replaced with a blocking piece 25, or conversely, the blocking piece 25 may be replaced with another hole forming piece 24, it is preferable that the hole forming piece 24 and the blocking piece 25 be configured to be easily detachable from the piece mounting hole 23c.

[0030] The hole forming piece 24 and the closing piece 25 preferably have insertion protrusions 24a and 25a, respectively, that can be inserted into the piece mounting holes 23c. The hole forming piece 24 and the closing piece 25 are preferably attached to the piece mounting holes 23c by inserting and engaging the insertion protrusions 24a and 25a into the piece mounting holes 23c.

[0031] Preferably, the bridge mounting hole 23c includes a female thread portion 23c1 and an enlarged diameter portion 23c2. The enlarged diameter portion 23c2 is located adjacent to the cavity surface 23a. Preferably, the enlarged diameter portion 23c2 is not female-threaded. The outer peripheral surfaces of the insertion protrusions 24a and 25a are preferably provided with male thread portions 24a1 and 25a1. In this case, the hole forming piece 24 and the closing piece 25 can be attached to the bridge mounting hole 23c by threading the female thread portion 23c1 with the male thread portions 24a1 and 25a1, and the hole forming piece 24 and the closing piece 25 can be removed from the bridge mounting hole 23c by unscrewing the threads. Instead of threading the insertion protrusions 24a and 25a into the bridge mounting hole 23c, the insertion protrusions 24a and 25a may be engaged with the bridge mounting hole 23c by snap-fitting or by a strong fit that allows removal.

[0032] The hole forming piece 24 and the closing piece 25 preferably have enlarged diameter portions 24a2 and 25a2 that are larger in diameter than the male thread portions 24a1 and 25a1. The inner diameter of the enlarged diameter portion 23c2 is the same as or slightly larger than the outer diameter of the enlarged diameter portions 24a2 and 25a2, and by engaging the enlarged diameter portions 24a2 and 25a2 with the enlarged diameter portion 23c2, the positioning accuracy of the hole forming piece 24 and the closing piece 25 is improved.

[0033] The hole forming piece 24 and the closing piece 25 preferably have engaging portions 24b, 25b that can be engaged with a fastening tool such as a screwdriver or a wrench. This makes it possible to attach and detach the hole forming piece 24 and the closing piece 25 using an attachment tool. In this embodiment, the engaging portion 24b of the hole forming piece 24 is formed as a hexagonal socket, and the hole forming piece 24 can be attached and detached from the piece attachment hole 23c by engaging a hexagonal wrench with the engaging portion 24b and rotating it. Furthermore, the engaging portion 25b of the closing piece 25 is formed as a linear groove, and the closing piece 25 can be attached and detached from the piece attachment hole 23c by engaging a flathead screwdriver or a coin with the engaging portion 25b and rotating it.

[0034] The hole forming piece 24 comprises a piece main body 24c and an engaging member 24d. The outer peripheral surface of the piece main body 24c has a shape corresponding to the inner peripheral surface of the plant insertion hole 31. The engaging member 24d comprises an engaging portion 24d1 that engages with the piece main body 24c and an insertion protrusion 24a connected to the engaging portion 24d. The hole forming piece 24 can be attached to the piece mounting hole 23c by engaging the engaging member 24d with the piece main body 24c and inserting and engaging the insertion protrusion 24a into the piece mounting hole 23c.

[0035] The hole forming pieces 24 are preferably arranged in opposing positions on the first mold 21 and the second mold 22, so that when the first and second molds 21, 22 are closed, the tips 24f of the hole forming pieces 24 of the first mold 21 and the hole forming pieces 24 of the second mold 22 abut against each other. In this case, as shown in Figures 9 to 11, when the first and second molds 21, 22 are closed with the parison 35 sandwiched between them, the parison 35 is sandwiched between the tips 24f of the hole forming pieces 24 of the first mold 21 and the second mold 22, and a cut-off portion 35d can be formed by welding the opposing inner surfaces of the parison 35 together. In order to clamp the parison 35 at high pressure, it is preferable that an annular portion 24f1 be provided at the tip 24f of the hole forming piece 24, and a resin reservoir 24g that accommodates the inner portion 35e of the annular notch 35d be provided inside the annular portion 24f1. The outer peripheral surface of the combined structure of the hole forming piece 24 of the first mold 21 and the hole forming piece 24 of the second mold 22 becomes the inner peripheral surface of the plant insertion hole 31 that penetrates the panel 40.

[0036] In order to position the hole forming pieces 24 on the first mold 21 and the second mold 22 in positions facing each other, the piece mounting holes 23c are also positioned on the first mold 21 and the second mold 22 in positions facing each other, and as a result, the closing pieces 25 are also positioned on the first mold 21 and the second mold 22 in positions facing each other.

[0037] The closing piece 25 is preferably configured so that its top surface 25c protrudes from the cavity surface 23a, and the bottom of the engagement portion 25b on the top surface 25c is preferably flush with or protrudes from the cavity surface 23a. In this case, the closing mark 32 (shown in FIGS. 1 and 2B) formed by the closing piece 25 is prevented from protruding from the upper surface 40a or lower surface 40b of the panel 40. This prevents the closing mark 32 of one panel 40 from interfering with another panel 40 when the panels 40 are stacked. Furthermore, the edge 25d of the top surface 25c is preferably rounded. In this case, the rounded bottom edge 32a (shown in FIG. 2B) of the closing mark 32 prevents dirt from remaining on the bottom edge 32a of the closing mark 32 when the panel 40 is washed and reused.

[0038] As described above, the mold unit 20 of this embodiment is configured so that the hole forming pieces 24 and the closing pieces 25 can be easily replaced, so the number of hole forming pieces 24 attached to the mold unit 20 can be easily increased or decreased. Furthermore, since the closing pieces 25 are placed in the piece mounting holes 23c to which no hole forming pieces 24 are attached, resin is prevented from entering the piece mounting holes 23c. This makes it possible to prevent the mold unit 20 from malfunctioning due to resin entering the piece mounting holes 23c and to prevent protrusions from being formed on the panel 40 due to the piece mounting holes 23c.

[0039] In one example, as shown in Fig. 7A , each mold body 23 has 64 piece mounting holes 23c. When manufacturing a panel 40 with 16 plant insertion holes 31, for example, hole-forming pieces 24 are installed in the 16 piece mounting holes 23c surrounded by the thick line 26 in Fig. 7B , and closing pieces 25 are installed in the remaining piece mounting holes 23c. When manufacturing a panel 40 with 32 plant insertion holes 31, for example, hole-forming pieces 24 are installed in the 32 piece mounting holes 23c surrounded by the thick line 26 in Fig. 8A , and closing pieces 25 are installed in the remaining piece mounting holes 23c. When manufacturing a panel 40 with 48 plant insertion holes 31, for example, hole-forming pieces 24 are installed in the 48 piece mounting holes 23c surrounded by the thick line 26 in Fig. 8B , and closing pieces 25 are installed in the remaining piece mounting holes 23c. In this way, by replacing the hole forming pieces 24 and the closing pieces 25, it is possible to manufacture a plurality of types of panels 40 with different numbers of plant insertion holes 31 using a common mold unit 20.

[0040] 3. Method for Manufacturing the Hydroponic Panel 40 A method for manufacturing the hydroponic panel 40 according to one embodiment of the present invention can be carried out using the above-described mold unit 20. This method includes a first manufacturing step and a second manufacturing step.

[0041] In the first manufacturing step, the hydroponic panel 40 is manufactured using the mold unit 20 in the first state. The first state is a state in which the number of hole forming pieces 24 and closing pieces 25 to be attached to the piece mounting holes 23c is a first predetermined number. The first predetermined number is, for example, 64 piece mounting holes 23c, 16 hole forming pieces 24, and 48 closing pieces 25.

[0042] In the second manufacturing process, the hydroponic panel 40 is manufactured using the mold unit 20 in the second state. The second state is a state in which the number of hole forming pieces 24 and closing pieces 25 attached to the piece mounting holes 23c is a second predetermined number. The second predetermined number is a number different from the first predetermined number. For example, the second predetermined number is 64 for the number of piece mounting holes 23c, 32 for the number of hole forming pieces 24, and 32 for the number of closing pieces 25.

[0043] The above method may include a third manufacturing step. In the third manufacturing step, the hydroponic cultivation panel 40 is manufactured using the mold unit 20 in the third state. The third state is a state in which the number of hole forming pieces 24 and closing pieces 25 to be attached to the piece mounting holes 23c is a third predetermined number. The third predetermined number is a number different from both the first predetermined number and the second predetermined number. For example, the third predetermined number is 64 for the number of piece mounting holes 23c, 48 for the number of hole forming pieces 24, and 16 for the number of closing pieces 25.

[0044] According to the above method, a common mold unit 20 can be used to manufacture a plurality of types of panels 40 having different numbers of plant insertion holes 31 .

[0045] In each of the first to third manufacturing processes, the panel 40 can be manufactured by a method including, for example, an arrangement process, a molding process, and a post-processing process. The first to third manufacturing processes are similar except that the numbers of hole forming pieces 24 and closing pieces 25 attached to the mold unit 20 are different. The arrangement process, molding process, and post-processing process will be described in detail below.

[0046] 3-1. Placement Step In the placement step, the first and second molds 21 and 22, which are mutually openable and closable, are opened, and the parison 35 is placed between the first and second molds 21 and 22, as shown in FIG.

[0047] The parison 35 can be formed by extruding molten resin from an extrusion head (not shown). The parison 35 may be cylindrical or sheet-shaped. When the parison 35 is sheet-shaped, the parison 35 is composed of, for example, first and second resin sheets 35a and 35b. In this case, as shown in FIG. 9 , the first and second resin sheets 35a and 35b are disposed between the first and second molds 21 and 22. The first and second resin sheets 35a and 35b can have different colors and / or reflectances, thereby enabling the manufacture of a panel 40 having upper and lower surfaces 40a and 40b with different colors and / or reflectances.

[0048] The resin constituting the parison 35 is preferably a thermoplastic resin such as polyolefin, and examples of polyolefin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer, and mixtures thereof.

[0049] 3-2. Molding Process In the molding process, as shown in FIGS. 10 to 12 , the parison 35 is placed between the first mold 21 and the second mold 22. The first and second molds 21, 22 are closed, and the hole-forming pieces 24 of the first mold 21 and the hole-forming pieces 24 of the second mold 22 are butted against each other, thereby clamping the parison 35 and welding the opposing inner surfaces of the parison 35 together to form a pinch-off portion 35d. The parison 35 is then molded into a panel shape to form the molded body 8. During this process, a flash 35c is formed on the outside of the pinch-off portion 23b. Furthermore, the inner portion 35e of the annular pinch-off portion 35d is positioned in a resin reservoir 24g (shown in FIG. 5B ) provided on the hole-forming piece 24. Examples of molding methods include blow molding, vacuum molding, and a combination thereof.

[0050] When the parison 35 is made up of first and second resin sheets 35a, 35b, first, as shown in Fig. 10, the first resin sheet 35a is vacuum-suctioned in the first mold 21 to form a shape that conforms to the cavity surface 23a of the first mold 21, and the second resin sheet 35b is vacuum-suctioned in the second mold 22 to form a shape that conforms to the cavity surface 23a of the second mold 22. Next, as shown in Fig. 11, the first and second molds 21, 22 are closed, and the first and second resin sheets 35a, 35b are molded into a panel shape to form the molded body 8.

[0051] By performing the molding process with a core material such as a foam placed inside the cylindrical parison 35 or between the first and second resin sheets 35a, 35b, a panel 40 having a core material inside the resin molded body can be manufactured.

[0052] 12, in the post-processing step, the cut-out portion 35d and the inner portion 35e thereof are removed from the molded body 8 to form the plant insertion hole 31. The cut-out portion 35d and the portion 35e may be removed within the first and second molds 21, 22, or may be removed after the first and second molds 21, 22 are opened and the molded body 8 is removed. The cut-out portion 35d and the portion 35e can be removed by cutting the cut-out portion 35d using a cutter or the like.

[0053] Furthermore, various post-treatments such as removal of burrs 35c adhering to the molded body 8 are carried out, whereby the desired panel 40 shown in FIGS. 1 and 2 can be obtained.

[0054] 13 shows a modified example of the blocking piece 25. In this modified example, the engaging portion 25b of the blocking piece 25 is not a groove, but is configured as a plurality of island-shaped recesses 25b1. Since the resin of the resin sheets 35a, 35b is unlikely to penetrate into the island-shaped recesses 25b1, forming the engaging portion 25b as the island-shaped recesses 25b1 prevents the formation of marks on the panel 40 caused by the engaging portion 25b.

[0055] The island-shaped recesses 25b1 are arranged in the circumferential direction around the rotation center C of the closing piece 25. By engaging a jig with the island-shaped recesses 25b1 and rotating the closing piece 25, the closing piece 25 can be attached to and detached from the mold body 23. The number of island-shaped recesses 25b1 required to rotate the closing piece 25 may be any number. In this modified example, four island-shaped recesses 25b1 are provided at 90-degree intervals, but the intervals and number can be changed as appropriate. In one example, two island-shaped recesses 25b1 can be provided at 180-degree intervals.

[0056] Furthermore, the closing piece 25 of this modified example has a tapered surface 25a3 at the tip of the insertion protrusion 25a, which makes it easier to insert the insertion protrusion 25a into the piece mounting hole 23c.

[0057] Furthermore, the thickness of the enlarged diameter portion 25a2 of the closing piece 25 of this modification is thinner than that of the embodiment shown in Fig. 6C, and is the same as the depth of the enlarged diameter portion 23c2 of the piece mounting hole 23c. Therefore, as shown in Fig. 14A, when the closing piece 25 is attached to the mold body 23, the top surface 25c of the closing piece 25 can be flush with the cavity surface 23a of the mold body 23. In this case, as shown in Figs. 14B and 14C, the formation of marks of the enlarged diameter portion 25a2 on the panel 40 is suppressed.

[0058] On the other hand, resin from resin sheets 35a, 35b may seep into island-shaped recesses 25b1, and in that case, protrusions 32b formed due to island-shaped recesses 25b1 may protrude from upper surface 40a or lower surface 40b, as shown in Figures 14B to 14C. If protrusions 32b protrude from upper surface 40a or lower surface 40b, this may cause rattling when multiple panels 40 are stacked, so it is preferable that protrusions 32b do not protrude from upper surface 40a or lower surface 40b.

[0059] For this reason, as shown in Fig. 15A, it is preferable to mount the closing piece 25 so that the top surface 25c protrudes from the cavity surface 23a. In this case, as shown in Figs. 15B to 15C, the protrusion 32b is formed in the recess 32c formed by the enlarged diameter portion 25a2, so that the protrusion 32b is prevented from protruding from the upper surface 40a or the lower surface 40b.

[0060] The protrusion amount of the top surface 25c from the cavity surface 23a is preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1 mm or less. This protrusion amount is, for example, 0 to 5 mm, specifically, for example, 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 mm, and may be in a range between any two of the numerical values ​​exemplified here or less than any one of them.

[0061] (Second Aspect) 1. Hydroponic Cultivation Tray 10 A hydroponic cultivation tray 10 according to one embodiment of the present invention shown in Fig. 16 is used for hydroponic cultivation by storing a nutrient solution therein. The tray 10 is made of a hollow resin molded body.

[0062] The tray 10 is generally rectangular in plan view, with a short side dimension of, for example, 60 to 240 cm, preferably 80 to 160 cm, and more preferably 100 to 140 cm (120 cm in this embodiment). The long side dimension is, for example, 90 to 360 cm, preferably 120 to 270 cm, and more preferably 140 to 240 cm (180 cm in this embodiment). The thickness of the tray 10 is, for example, 5 to 20 cm, and preferably 8 to 14 cm (11.3 cm in this embodiment).

[0063] The tray 10 is shaped like a container that is open at the top and includes a bottom 1 and side portions 2 that rise up to surround the bottom 1. In the following description, terms related to directions such as "upper," "lower," and "horizontal" refer to directions when the bottom 1 is placed on the ground.

[0064] The side portion 2 has a pair of long sides 2k corresponding to the long sides of the rectangular side portion 2 and a pair of short sides 2l corresponding to the short sides, with the long sides 2k and the short sides 2l connected to each other at corners. As shown in FIGS. 20 to 22 , the tray 10 has a double-wall structure including an inner wall 10a and an outer wall 10b. The inner wall 10a and the outer wall 10b are connected to each other by a top wall 10c. The top wall 10c is preferably horizontal. The inner wall 10a is disposed inside the tray 10, and the outer wall 10b is disposed outside the inner wall 10a. The distance between the inner surface of the inner wall 10a and the outer surface of the outer wall 10b is, for example, 10 to 50 mm, and preferably 20 to 40 mm (32 mm in this embodiment).

[0065] As shown in Figures 16B, 17A, and 20A, the bottom 1 is provided with recesses 1a formed by recessing the outer wall 10b toward the inner wall 10a. The recesses 1a are conical in shape. A large number of recesses 1a are provided uniformly across the entire bottom 1. At the bottom of the recesses 1a, welded portions 1b are provided where the inner wall 10a and the outer wall 10b are welded to each other (also expressed as "joined" or "integrated"; the same applies below). The rigidity of the bottom 1 is increased by providing the recesses 1a and welded portions 1b.

[0066] As shown in FIG. 20A , in the side portion 2, the inner wall 10a includes, in order from the inner wall 10a (hereinafter referred to as the bottom inner wall 1c) side of the bottom portion 1, a lower inner wall 2a, a middle inner wall 2b, and an upper inner wall 2c. The middle inner wall 2b has a gentler slope than the lower inner wall 2a and the upper inner wall 2c and is preferably parallel to the bottom inner wall 1c. The middle inner wall 2b is preferably provided around the entire periphery of the tray 10. For example, a panel for holding plants to be hydroponically grown can be placed on the middle inner wall 2b. The lower inner wall 2a has a steeper slope than the upper inner wall 2c. This is because the upper inner wall 2c has a relatively gentle slope to make it easier to insert panels into the tray 10, while the lower inner wall 2a has a relatively steep slope to increase the amount of nutrient solution that can be accommodated in the tray 10.

[0067] As shown in FIG. 16A , the bottom portion 1 is provided with a first protrusion 1d and a second protrusion 1e that protrude upward. The first protrusion 1d is provided at the center of the bottom portion 1. The first protrusion 1d is disposed between a pair of second protrusions 1e. The first protrusion 1d and the second protrusion 1e are aligned along a second direction D2 (described later). The first protrusion 1d and the second protrusion 1e are disposed at the center of the bottom portion 1 in the first direction D1 (described later). The first protrusion 1d and the second protrusion 1e function as pillars that support a panel placed on the intermediate inner wall 2b. Therefore, the upper surfaces of the first protrusion 1d and the second protrusion 1e are substantially flush with the upper surface of the intermediate inner wall 2b. Furthermore, when multiple panels (e.g., four panels) are arranged side by side in the tray 10, the upper surface of the first protrusion 1d is wider than the upper surface of the second protrusion 1e so that the first protrusion 1d can support the corners of the panels.

[0068] The side portion 2 is provided with recesses 2d, each formed by recessing the outer wall 10b toward the inner wall 10a. The recesses 2d are provided on each of the long side portion 2k and the short side portion 2l. Examples of the recesses 2d include first to fourth recesses 2d1 to 2d4. It is preferable that each recess 2d has at least one welded portion. Examples of the welded portions include first to fifth welded portions 2e1 to 2e5, which will be described later.

[0069] As shown in Figures 18 and 19, the long side portion 2k is provided with a first recess 2d1 and a second recess 2d2. The first recess 2d1 includes an engagement recess 2f and a reinforcing recess 2g. As shown in Figures 20A and 20B, the engagement recess 2f is formed by recessing the outer wall 10b upward. The engagement recess 2f includes an inner wall 2f1 and an outer wall 2f2. The inner wall 2f1 and the outer wall 2f2 form a pair of side walls of the engagement recess 2f, and the inner wall 2f1 is positioned more inward of the outer wall 2f2 on the tray 10. The inner wall 2f1 is preferably provided with a first welded portion 2e1, where the inner wall 10a and the outer wall 10b are welded to each other. The first welded portion 2e1 is preferably formed by welding the outer wall 10b to a portion 2h that straddles the upper inner wall 2c and the middle inner wall 2b.

[0070] The engagement recess 2f is a portion that engages with the tip 4c of the hook 4 attached to the drive unit 3 (shown in FIG. 23). The hook 4 includes a base 4a, an attachment portion 4b, and a tip 4c. The attachment portion 4b and the tip 4c are disposed so as to extend upward from the base 4a. The drive unit 3 is a device for moving the hook 4. The drive unit 3 is attached to the attachment portion 4b. A gap 4d is provided between the attachment portion 4b and the tip 4c. As shown in FIGS. 17B and 21, when the tip 4c engages with the engagement recess 2f, the outer portion 2p located outside the engagement recess 2f is accommodated in the gap 4d. With the tip 4c of the hook 4 engaged with the engagement recess 2f, the hook 4 can be moved toward the inner wall 2f1 or the outer wall 2f2 (i.e., horizontally) to transport (i.e., move horizontally).

[0071] When moving the trays 10 by pulling, typically only one tray is pulled, but when moving the trays 10 by pushing, multiple trays 10 may be arranged in series and all of the trays may be moved simultaneously by pushing the endmost tray 10. For this reason, when pushing the trays 10, a large force is applied to the trays 10, which makes the trays 10 prone to deformation. On the other hand, in the tray 10 of this embodiment, the first welded portion 2e1 is provided on the inner wall 2f1, which is prone to receiving a large load from the hooks 4, and the rigidity of the inner wall 2f1 is increased, so deformation of the tray 10 when pushed can be suppressed.

[0072] If the direction in which the inner wall 2f1 and the outer wall 2f2 face each other is defined as a first direction D1, the engagement recess 2f preferably extends in a second direction D2 perpendicular to the first direction D1. In other words, the engagement recess 2f preferably has an elongated shape extending in the second direction D2. The tip 4c of the hook 4 also has an elongated shape extending in the second direction D2. The tip 4c has a shape and size that allows it to be accommodated in the engagement recess 2f with almost no gap. By accommodating the tip 4c in the engagement recess 2f, the hook 4 and the engagement recess 2f engage. This configuration facilitates dispersion of the force applied to the tray 10 from the tip 4c, thereby suppressing local deformation of the tray 10. The first direction D1 is, for example, the short side direction, and the second direction D2 is, for example, the long side direction. The hook 4 abuts against the inner wall 2f1 when pushing the tray 10 with the hook 4.

[0073] The reinforcing recesses 2g are provided adjacent to the engagement recesses 2f so as to extend in the first direction D1. That is, the reinforcing recesses 2g have an elongated shape extending in the first direction D1. By providing the reinforcing recesses 2g, deformation of the tray 10 when it is pushed can be further suppressed. It is preferable to provide a pair of reinforcing recesses 2g adjacent to each engagement recess 2f. In this case, deformation of the tray 10 when it is pushed can be further suppressed. The reinforcing recesses 2g are preferably provided so as to be continuous with the engagement recesses 2f. As shown in FIGS. 19 and 20B , the inner wall 2f1 at a portion 2q where no reinforcing recesses 2g are provided (i.e., a portion 2q1 between a pair of reinforcing recesses 2g or a portion 2q2 on the opposite side of the reinforcing recess 2g from the portion 2q1) is higher than the inner wall 2f1 at the reinforcing recess 2g. Therefore, the contact area with the hook 4 is larger at the portion 2q, making it more susceptible to load from the hook 4. On the other hand, it is preferable that the upper end of the reinforcing recess 2g does not reach the upper surface of the engaging recess 2f. In this case, as shown in Figures 20A and 21, the inner wall 2f1 of the engaging recess 2f also exists in the reinforcing recess 2g, and the load from the hook 4 can be received, and the load from the hook 4 can be effectively distributed over the entire inner wall 2f1 of the engaging recess 2f.

[0074] Additionally, a second welded portion 2e2 is preferably provided at the bottom of the reinforcing recess 2g, where the inner wall 10a and the outer wall 10b are welded to each other. The second welded portion 2e2 is preferably configured by welding the outer wall 10b to a portion 2i that straddles the bottom inner wall 1c and the lower inner wall 2a. In this case, deformation of the tray 10 when it is pressed can be further suppressed. A hollow portion 2o, where the inner wall 10a and the outer wall 10b are not welded, is preferably provided between the first welded portion 2e1 and the second welded portion 2e2.

[0075] It is preferable that a portion 2j between a pair of reinforcing recesses 2g is a convex portion when viewed from the bottom of the reinforcing recesses 2g. In this case, the side wall 2j1 (shown in FIG. 17A) of the portion 2j further increases the rigidity of the portion to which a strong force is applied when the tray 10 is pressed, thereby further suppressing deformation of the tray 10 when the tray 10 is pressed. As shown in FIG. 20B, it is preferable that the second welded portion 2e2 is not provided in the portion 2j.

[0076] 20C, first and second welded portions 2e1 and 2e2 are provided in the second recess 2d2. By providing such a recess, the rigidity of the tray 10 is further increased.

[0077] 18, two first recesses 2d1 and two second recesses 2d2 are provided on each long side 2k. Preferably, two second recesses 2d2 are provided between two first recesses 2d1.

[0078] As shown in Figures 18 and 19, a third recess 2d3 and a fourth recess 2d4 are provided in the short side portion 2l. As shown in Figure 22A, the third recess 2d3 has a third welded portion 2e3. The third welded portion 2e3 is formed by welding a corner 2m between the middle inner wall 2b and the upper inner wall 2c to the outer wall 10b. In the third recess 2d3, no portions other than the third welded portion 2e3 are welded. As shown in Figure 22B, the fourth recess 2d4 has a fourth welded portion 2e4 and a fifth welded portion 2e5. The fourth welded portion 2e4 is formed by welding the outer wall 10b to the middle inner wall 2b. The fifth welded portion 2e5 is formed by welding a corner 2n between the lower inner wall 2a and the bottom inner wall 1c to the outer wall 10b. 18, two third recesses 2d3 are provided on each short side 2l, and four fourth recesses 2d4 are provided on each short side 2l. Each third recess 2d3 is located between the two fourth recesses 2d4 from the end. This configuration increases the rigidity of the short side 2l.

[0079] The recesses provided on the long side portion 2k and / or the short side portion 2l are preferably arranged symmetrically with respect to the central plane in the first direction D1 and / or the second direction D2.

[0080] 2. Conveying Device 5 and Method for Hydroponic Cultivation Trays 10 Next, a conveying device 5 and method for conveying hydroponic cultivation trays 10 will be described with reference to FIG. 23 . The conveying device 5 of this embodiment includes a pair of bases 6 and a free conveyor 7 disposed therebetween. The free conveyor 7 may be, for example, a non-powered roller conveyor. The plant factory includes a work area where various tasks required for hydroponic cultivation are performed on the trays 10, and a cultivation shelf where the trays 10 are placed and plants are grown. Tasks performed in the work area include planting, harvesting, cleaning, and inspection. After the trays 10 have been processed in the work area, they are transported to the base 6 by a transport means (not shown), and are then transported between the base 6 and the free conveyor 7 by the conveying device 5. The free conveyor 7 serves as the cultivation shelf. The free conveyor 7 has the advantage of lower installation and maintenance costs compared to powered conveyors. On the other hand, many trays 10 are arranged in series on the free conveyor 7, and each tray 10 weighs, for example, 80 kg when filled with nutrient solution, so it is important to have a means for efficiently transporting these trays 10. The number of trays 10 arranged in series is, for example, 10 to 60, and preferably 20 to 40 (32 in this embodiment).

[0081] The base 6 may have a function of moving the tray 10 in the vertical direction, and the free conveyor 7 may be arranged in multiple stages. In this case, it becomes possible to transport the tray 10 to the free conveyor 7 in multiple stages.

[0082] In this embodiment, the trays 10 are arranged in series in the first direction D1. As shown in FIG. 17 , the tray 10 can be moved from the base 6 onto the free conveyor 7 by pushing the tray 10 with the hook 4 of the drive unit 3 engaged with the engagement recess 2f. At this time, the trays 10 already placed on the free conveyor 7 are also pushed and moved. The tray 10 can also be moved from the free conveyor 7 to the base 6 by pulling the tray 10 with the hook 4 of the drive unit 3 engaged with the engagement recess 2f. It is also possible to push one of the trays 10 at one end of the series-arranged trays 10 to push the tray 10 at the other end from the free conveyor 7 onto the base 6. In this case, the operation of pulling the tray 10 is unnecessary. The drive unit 3 can be configured, for example, as a robot arm having the number of axes capable of performing the above-described operations.

[0083] In FIG. 23, the short side direction of the tray 10 is the first direction D1, but the long side direction of the tray 10 may be the first direction D1.

[0084] 3. Manufacturing Method of Hydroponic Cultivation Tray 10 The hydroponic cultivation tray 10 can be formed by molding a parison using a split mold that can be opened and closed. The parison may be cylindrical or sheet-shaped. The resin constituting the parison is preferably a thermoplastic resin such as polyolefin, and examples of polyolefin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer, and mixtures thereof. Molding methods include blow molding, vacuum molding, and combinations thereof. During this molding, the inner surfaces of opposing portions of the parison (when the parison is composed of a pair of resin sheets, the inner surfaces of the pair of resin sheets) are welded to form welded portions 1b, 2e1 to 2e5.

[0085] 1: bottom, 1a: recess, 1b: welded portion, 1c: bottom inner wall, 1d: first protrusion, 1e: second protrusion, 2: side, 2a: lower inner wall, 2b: middle inner wall, 2c: upper inner wall, 2d: recess, 2d1: first recess, 2d2: second recess, 2d3: third recess, 2d4: fourth recess, 2e1: first welded portion, 2e2: second welded portion, 2e3: third welded portion, 2e4: fourth welded portion, 2e5: fifth welded portion, 2f: engagement recess, 2f1: inner wall, 2f2: outer wall, 2g: reinforcing recess, 2h: part, 2i: part, 2j: part, 2j1: side wall, 2k: long side part, 2l: short side part, 2m: corner part, 2n: corner part, 2o: hollow part, 2p: outer part, 2q: part, 2q1: part, 2q2: part, 3: driving device, 4: hook, 4a: base, 4b: mounting part, 4c: tip part, 4d: gap, 5: conveying device, 6: base, 7: free conveyor, 8: molded body, 9: nutrient solution, 10: hydroponic cultivation tray, 10a: inner wall, 10b: outer wall, 10c: upper wall, 20: mold unit for manufacturing hydroponic cultivation panel , 21: first mold, 22: second mold, 23: mold body, 23a: cavity surface, 23b: pinch-off portion, 23c: bridge mounting hole, 23c1: female screw portion, 23c2: enlarged diameter portion, 24: hole forming bridge, 24a: insertion protrusion, 24a1: male screw portion, 24a2: enlarged diameter portion, 24b: engaging portion, 24c: bridge body, 24d: engaging member, 24d1: engaging portion, 24f: tip, 24f1: annular portion, 24g: resin reservoir, 25: closing bridge, 25a: insertion protrusion, 25a1: male screw portion, 25a 2: enlarged diameter portion, 25a3: tapered surface, 25b: engaging portion, 25b1: island-shaped recess, 25c: top surface, 25d: edge, 26: thick line, 31: plant insertion hole, 32: closing mark, 32a: edge, 32b: protrusion, 32c: recess, 34: plant, 35: parison, 35a: first resin sheet, 35b: second resin sheet, 35c: burr, 35d: cutting portion, 35e: part, 40: hydroponic cultivation panel, 40a: upper surface, 40b: lower surface, 50: plug, C: rotation center, CP: central surface, P: plant

Claims

1. A mold unit for manufacturing panels for hydroponic cultivation, the mold unit comprising first and second molds configured to be openable and closable, the first and second molds each comprising a mold body, a cavity surface of the mold body being provided with a plurality of piece mounting holes, the piece mounting holes being configured to accommodate both hole forming pieces for forming crop insertion holes and closing pieces for closing the piece mounting holes, and the mold unit for manufacturing panels for hydroponic cultivation, wherein the number of hole forming pieces attached to the piece mounting holes can be changed to change the number of crop insertion holes formed in the hydroponic cultivation panel.

2. A mold unit as described in claim 1, wherein the piece mounting hole of the mold body of the first mold and the piece mounting hole of the mold body of the second mold are positioned opposite each other.

3. A mold unit as described in claim 2, wherein the hole forming piece attached to the piece mounting hole of the first mold and the hole forming piece attached to the piece mounting hole of the second mold have the same shape.

4. A method for manufacturing a hydroponic panel using a mold unit as claimed in any one of claims 1 to 3, comprising a first manufacturing process and a second manufacturing process, in which in the first manufacturing process, the hydroponic panel is manufactured using the mold unit in a first state, the first state being a state in which the numbers of the hole forming pieces and the closing pieces to be attached to the piece mounting holes are each a first predetermined number, and in the second manufacturing process, the hydroponic panel is manufactured using the mold unit in a second state, the second state being a state in which the numbers of the hole forming pieces and the closing pieces to be attached to the piece mounting holes are each a second predetermined number, the second predetermined number being a number different from the first predetermined number.

5. A hydroponic tray comprising: a bottom and sides rising to surround the bottom; an inner wall disposed on the inside of the tray and an outer wall disposed outside the inner wall; an engagement recess formed in the side by recessing the outer wall upward; the engagement recess comprising an inner wall and an outer wall; the inner wall and the outer wall being a pair of side walls of the engagement recess; and the inner wall disposed inside the tray relative to the outer wall.

6. A tray according to claim 5, wherein a first welding portion is provided on the inner wall, where the inner wall and the outer wall are welded to each other.

7. A tray as claimed in claim 5, wherein the direction in which the inner wall and the outer wall face each other is defined as a first direction, and the engagement recess extends in a second direction perpendicular to the first direction.

8. A tray as described in claim 5, wherein, when the direction in which the inner wall and the outer wall face each other is defined as a first direction, a reinforcing recess is provided adjacent to the engagement recess and extending in the first direction.

9. A tray according to claim 8, wherein a second welding portion where the inner wall and the outer wall are welded to each other is provided at the bottom of the reinforcing recess.

10. The tray according to claim 8, wherein a pair of the reinforcing recesses are provided at positions adjacent to the engagement recesses.

11. A method for transporting a tray as set forth in any one of claims 5 to 10, comprising the steps of: engaging a tip of a hook attached to a drive device with the engaging recess; and moving the hook in the direction of the inner wall or the outer wall to transport the tray.

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