Rotational molding die

Abstract

The present invention provides a rotational molding die for rotational molding, capable of molding a plurality of molded products, and comprising: a frame body having a plurality of fitting frames; and a plurality of molding dies each having a molding portion for molding a molded product, and being respectively fitted such that the molding portion faces the inner space of the rotational molding die. An adiabatic portion is provided which covers portions other than the molding portion of the inner surface of each molding die facing the inner space of the rotational molding die and the inner surface of each fitting frame facing the inner space of the rotational molding die.

Description

Technical Field

[0001] The present disclosure relates to a mold for rotational molding, which is capable of molding a plurality of molded products. Background Art

[0002] Japanese Patent Application Laid-Open No. 2008-62399 discloses an injection molding die capable of molding a plurality of molded products at once. In this die, the runner length is adjusted by a separately provided adjustment mechanism, thereby achieving a filling balance of the resin in each cavity and equalizing the quality of the molded products formed through each cavity. Summary of the Invention

[0003] However, since the above-mentioned die has an adjustment mechanism, its structure is complex, so the manufacturing cost of the die increases. Moreover, the adjustment operation using the adjustment mechanism becomes a labor- and time-consuming operation. Therefore, a technique is desired that can mold a plurality of molded products at once using a die with a simple mold structure.

[0004] The present disclosure can be implemented in the following manner.

[0005] (1) According to one aspect of the present disclosure, there is provided a rotational molding die for rotational molding, which is capable of molding a plurality of molded products. The rotational molding die includes: a frame having a plurality of mounting frames; and a plurality of molding dies each having a molding portion for molding a molded product, and being respectively mounted with the molding portion facing the internal space of the rotational molding die.

[0006] The rotational molding die of this aspect is a die with a simple mold structure, including: a frame having a plurality of mounting frames; and a plurality of molding dies mounted on the plurality of mounting frames. When rotational molding is performed using the rotational molding die of this aspect, a molded product can be molded by the molding portion of each molding die. Therefore, according to this rotational molding die, a plurality of molded products can be manufactured at once using a die with a simple mold structure. Moreover, in rotational molding, it is possible to easily equalize the quality of the molded products.

[0007] (2) The rotational molding die of the above aspect may further include a heat insulating portion that covers a portion other than the molding portion of the inner surface of each molding die facing the internal space and the inner surface of each mounting frame facing the internal space.

[0008] According to the rotational molding die of this aspect, during rotational molding, the molding material does not melt and adhere to a portion other than the molding portion of the inner surface of each molding die facing the internal space of the rotational molding die and the inner surface of each mounting frame, and it is possible to avoid useless molding in a portion other than the molding portion. As a result, post-treatment processes such as cutting off useless portions molded around each molded product can be omitted.

[0009] (3) The plurality of molding dies of the rotational molding die in the above manner may be composed of one type of molding die or two or more different types of molding dies.

[0010] According to the rotational molding die of this manner, when the plurality of molding dies are composed of one type of molding die, a plurality of molding products of one type can be molded simultaneously, and when the plurality of molding dies are composed of two or more different types of molding dies, a plurality of molding products of different types can be molded simultaneously.

[0011] The present disclosure is not only the rotational molding die in the above manner, but can also be implemented in various ways such as a rotational molding device equipped with the rotational molding die. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the drawings, in which the same reference numerals denote the same components, where:

[0013] Figure 1 is a perspective view showing a schematic structure of a rotational molding die as a first embodiment;

[0014] Figure 2 schematically shows Figure 1 a cross-sectional view of the II-II section;

[0015] Figure 3 schematically shows Figure 1 a schematic cross-sectional view of the III-III section;

[0016] Figure 4 is an explanatory view showing an assembly step of the rotational molding die;

[0017] Figure 5 is a perspective view showing a schematic structure of a rotational molding die as a second embodiment;

[0018] Figure 6 is an explanatory view showing an assembly step of the upper die frame with the molding die assembled. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] A. First Embodiment:

[0020] Figure 1 is a perspective view showing a schematic structure of a rotational molding die 10 as a first embodiment. Figure 2 schematically shows Figure 1 a cross-sectional view of the II-II section, Figure 3 schematically shows Figure 1 a schematic cross-sectional view of the III-III section.

[0021] The rotational molding die 10 includes: a frame 20 having six fitting frames 21; and six plate-shaped molding dies 30 fitted to the six fitting frames 21. The frame 20 has a structure in which the six fitting frames 21 are arranged in a rectangular parallelepiped shape such that the three-dimensional contour formed by the six fitting frames 21 is substantially a rectangular parallelepiped. In each fitting frame 21, there is provided a fitting groove 22 into which an end portion of the molding die 30 is inserted. The rotational molding die 10 has a structure in which, by fitting the end portions of the molding dies 30 into the fitting grooves 22 of the respective fitting frames 21, the contour is substantially a rectangular parallelepiped and has a hollow shape.

[0022] The frame 20 is composed of a lower die frame 210 and an upper die frame 220. The lower die frame 210 is composed of five fitting frames 21 corresponding to four side surfaces and a lower surface among the six rectangular parallelepiped-shaped fitting frames 21 excluding the upper surface. The upper die frame 220 is composed of one fitting frame 21 corresponding to the upper surface of the rectangular parallelepiped among the six fitting frames 21. The frame 20 having a rectangular parallelepiped shape in contour is formed by connecting the upper die frame 220 to the upper part of the lower die frame 210.

[0023] Each fitting frame 21 of the lower die frame 210 is respectively composed of four columnar frame structure portions 211 that surround the rectangular-shaped molding die 30. On the surface of each frame structure portion 211 that surrounds the molding die 30, there is provided a groove 213 that constitutes the fitting groove 22. Moreover, the fitting frame 21 of the upper die frame 220 is also composed of four columnar frame structure portions 221 that surround the molding die 30. On the surface of each frame structure portion 221 that surrounds the molding die 30, there is provided a groove 223 that constitutes the fitting groove 22.

[0024] Flanges 212 are provided on the upper four frame structure portions 211 of the lower die frame 210, and connection holes 214 for connecting the upper die frame 220 are provided in the flanges 212. Moreover, flanges 222 are provided on the four frame structure portions 221 of the upper die frame 220, and connection holes 224 for connecting the lower die frame 210 are provided in the flanges 222. The lower die frame 210 and the upper die frame 220 are connected by connection bolts and connection nuts (not shown) inserted into the connection holes 214 and the opposing connection holes 224.

[0025] On the inner surface of the molding die 30 fitted to each fitting frame 21 and facing the inner space side of the rotational molding die 10, there is provided a molding portion 32. The molding portion 32 is a portion having a surface shape corresponding to the surface shape of the molded molded product MP.

[0026] An adiabatic part 42 is provided on the inner surface 23 of the fitting frame 21 facing the inner space side of the rotational molding die 10 so as to cover this surface. Further, an adiabatic part 44 is also provided on a part other than the molding part 32 of the molding die 30 so as to cover this part. The adiabatic part 42 can be formed by pasting an adiabatic material or coating an adiabatic agent. Further, the adiabatic part 44 can also be formed in the same manner by pasting an adiabatic material or coating an adiabatic agent. The adiabatic parts 42 and 44 are parts whose surface temperature is lower than the melting temperature of the molding material when heated to a temperature higher than the melting temperature of the molding material. As the adiabatic material or adiabatic agent, a material having heat resistance higher than the heating temperature of the die can be used, such as super engineering plastics such as PTFE, PEEK, and PI, silicone resin, and ceramics.

[0027] Figure 4 FIG. is an explanatory view showing the assembling steps of the rotational molding die 10. As described below, after the lower die frame 210 of the molding die assembly is formed and the upper die frame 220 of the molding die assembly is formed, the molding material is filled into the lower die frame 210, and the lower die frame 210 and the upper die frame 220 are connected, whereby the rotational molding die 10 is formed.

[0028] The lower die frame 210 is composed of three divided lower die frame parts 210a, 210b, and 210c. The first lower die frame part 210a is a part composed of four frame structure parts 211 provided with upper flanges 212 among the 12 frame structure parts 211 forming the cubic outline of the lower die frame 210, and five frame structure parts 211 other than three frame structure parts 211 on one side. The second lower die frame part 210b is a part composed of three frame structure parts 211 on one side excluded from the first lower die frame part 210a. The third lower die frame part 210c is a part of four frame structure parts 211 provided with upper flanges 212 excluded from the first lower die frame part 210a and the second lower die frame part 210b.

[0029] Regarding the first lower die frame part 210a, the molding die 30 is inserted into three molding die insertion positions formed by three frame structure parts 211 along the vertical direction, and the molding die 30 is inserted into one molding die insertion position formed by two frame structure parts 211 along the horizontal direction, whereby four molding dies 30 can be assembled.

[0030] Further, the second lower die frame part 210b is the same as the first lower die frame part 210a, and the molding die 30 is inserted into one molding die insertion position formed by two frame structure parts 211 along the vertical direction, whereby one molding die 30 can be assembled.

[0031] Further, for the first lower mold frame part 210a after the molding die is assembled, the second lower mold frame part 210b after the molding die is assembled is inserted and connected from the side where it is exposed from the end of the molding die 30, and the third lower mold frame part 210c is inserted and connected from above where it is exposed from the end of the molding die 30, whereby the lower mold frame 210 after the molding die is assembled can be formed. It should be noted that the connection between the respective lower mold frame parts can be performed using connection members (not shown), such as spring locks.

[0032] The upper mold frame 220 is composed of two divided upper mold frame parts 220a and 220b. The first upper mold frame part 220a is a part composed of three of the four frame structure parts 221 provided with flanges 222 in the upper mold frame 220, excluding one of the frame structure parts 221. The second upper mold frame part 220b is a part composed of the frame structure part 211 provided with one flange 222 excluded from the first upper mold frame part 220a.

[0033] The first upper mold frame part 220a is inserted into the molding die insertion position at one place composed of three frame structure parts 221, whereby one molding die 30 can be assembled.

[0034] Further, for the first upper mold frame part 220a after the molding die is assembled, the second upper mold frame part 220b is inserted and connected from the side where it is exposed from the edge of the molding die 30, whereby the upper mold frame 220 after the molding die is assembled can be formed. It should be noted that the connection between the respective upper mold frame parts can also be performed in the same manner as the connection between the respective lower mold frame parts, using connection members (not shown), such as spring locks.

[0035] Regarding the lower mold frame 210 after the molding die is assembled and the upper mold frame 220 after the molding die is assembled configured as described above, they are arranged such that the connection hole 214 of the lower mold frame 210 faces the connection hole 224 of the upper mold frame 220, and the upper mold frame 220 after the molding die is assembled is connected to the upper part of the lower mold frame 210 after the molding die is assembled by connection bolts and connection nuts (not shown), whereby the rotational molding die 10 can be formed.

[0036] While heating the rotational molding die 10 having the above-described structure with a heating device (not shown), it is rotated by a rotating device, whereby the molding material filled in the internal space of the rotational molding die 10 is melted and adheres to the molding parts 32 of the respective molding dies 30, and a non-hollow shaped molded product MP having a surface shape corresponding to the molding parts 32 of the respective molding dies 30 is molded. It should be noted that as the molding material, various thermoplastic resin materials such as PP and PE can be used as the resin material for forming the molded product MP to be molded.

[0037] In the case where rotational molding is performed using the rotational molding die 10 described above, multiple molded products MP can be molded respectively by the multiple molding dies 30 that are assembled, and thus multiple molded products MP can be produced at once. Moreover, the rotational molding die 10 is a die with a simple die structure, and it includes: a frame body 20 having multiple mounting frames 22; and multiple molding dies 30 mounted on the multiple mounting frames 22. Therefore, according to the rotational molding die 10, compared with the injection molding dies and the like described in the prior art, it can have a simple and inexpensive structure, can produce multiple molded products at once, and thus can produce molded products inexpensively.

[0038] In addition, regarding rotational molding, multiple molded products MP can be produced by the multiple molding dies 30 in an environment that can be adjusted by easy adjustments such as the rotational speed and the heating temperature, and thus the uniformity of quality can be easily achieved.

[0039] In addition, the rotational molding die 10 can be constituted by respectively mounting the molding dies 30 on multiple mounting frames 21, and thus if the molding die to be mounted is changed, the molded product to be produced can be easily changed.

[0040] In addition, a heat insulating portion 42 is provided so as to cover the inner surface 23 of each mounting frame 21 facing the inner space side of the rotational molding die 10, and a heat insulating portion 44 is provided so as to cover the portion other than the molding portion 32 of each molding die 30. Therefore, during rotational molding, in the portions where the heat insulating portion 42 and the heat insulating portion 44 are provided, the molten molding material does not adhere, and it is possible to avoid useless molding in portions other than the molding portion 32. Thus, post-processing steps such as cutting off the useless portions generated around the molded product can be omitted.

[0041] B. Second Embodiment:

[0042] Figure 5 FIG. 16 is a perspective view showing a schematic structure of a rotational molding die 10B as a second embodiment. The rotational molding die 10B includes: a frame body 20B having eight mounting frames 21B; and eight plate-shaped molding dies 30B mounted on the eight mounting frames 21B. The frame body 20B has a structure in which the eight mounting frames 21B are arranged in an octahedron state such that the three-dimensional contour formed by the eight mounting frames 21B becomes a substantially octahedron. An assembly groove 22B for embedding the molding die 30B is provided in each mounting frame 21B.

[0043] The frame 20B is composed of a lower mold frame 210B and an upper mold frame 220B. The upper mold frame 220B is composed of four of the eight octahedron-shaped fitting frames 21B corresponding to the four side faces on the upper side. Similarly, the lower mold frame 210B is composed of four of the eight octahedron-shaped fitting frames 21B corresponding to the four side faces on the lower side. The frame 20B with an octahedron-shaped contour is formed by connecting the upper mold frame 220B to the upper part of the lower mold frame 210B.

[0044] Each fitting frame 21B of the upper mold frame 220B is respectively composed of three columnar frame structure parts 221B surrounding the triangular-shaped molding die 30B. Moreover, each fitting frame 21B of the lower mold frame 210B is also respectively composed of three columnar frame structure parts 211B surrounding the molding die 30B.

[0045] Flanges 222B are provided on the four lower frame structure parts 221B on the lower mold frame 210B side of the upper mold frame 220B, and connection holes 224B are provided on the flanges 222B. Flanges 212B are provided on the four upper frame structure parts 211B on the upper mold frame 220B side of the lower mold frame 210B, and connection holes 214B for connecting to the upper mold frame 220B are provided on the flanges 212B. The lower mold frame 210B and the upper mold frame 220B are connected by connection bolts and connection nuts (not shown) inserted into the connection holes 214B and the corresponding connection holes 224B.

[0046] A molding part 32B is provided on the inner surface of the molding die 30B assembled in each fitting frame 21B facing the inner space side of the rotational molding die 10B. The shape of the molding part 32B is a part having a surface shape corresponding to the surface shape of the molded product to be molded, and it can be the same as or different from the molding part 32 of the molding die 30 in the first embodiment.

[0047] Although not shown in the figure, in the rotational molding die 10B, similar to the rotational molding die 10, a heat insulating part is provided so as to cover the surface of the fitting frame 21B facing the inner space side of the rotational molding die 10B and the part other than the molding part 32B of the molding die 30B.

[0048] Figure 6This is an explanatory diagram showing the assembly steps of the upper mold frame 220B after the molding die is assembled. The upper mold frame 220B is composed of one first upper mold frame part 220Ba and four second upper mold frame parts 220Bb that are divided. The first upper mold frame part 220Ba is a part composed of five of the eight frame structure parts 221B that form the pyramid-shaped contour of the upper mold frame 220B, excluding the four frame structure parts 221B provided with the lower flange 222B. The second upper mold frame part 220b is a part of the frame structure part 221B provided with the lower flange 222B.

[0049] Insert the molding die 30B into the four molding die insertion positions of the first upper mold frame part 220Ba formed by the four frame structure parts 221B. Embed and connect the four second upper mold frame parts 220Bb to the first upper mold frame part 220Ba after the molding die is assembled, whereby the upper mold frame 220B after the molding die is assembled can be formed. It should be noted that the connection between the respective upper mold frame parts can be performed using a connection member (not shown), such as a spring lock.

[0050] Although not shown in the figure, the lower mold frame 210B after the molding die is assembled can also be formed in the same manner as the upper mold frame 220B.

[0051] The rotational molding die 10B of the second embodiment described above can also produce multiple molded products at one time in the same manner as the rotational molding die 10 of the first embodiment. Moreover, compared with the rotational molding die 10, the rotational molding die 10B can be assembled with more molding dies, so that more molded products can be produced at one time. Moreover, compared with other molds such as injection molding, it can have a simple and inexpensive structure, can produce multiple molded products at one time, so that the molded products can be produced inexpensively. Moreover, it can easily achieve the homogenization of the quality of the multiple molded products produced. Moreover, it can easily change the molded products to be produced. Moreover, it can avoid useless molding in parts other than the molding part 32B, so that post-treatment processes such as cutting off the useless parts generated around the molded product can be omitted.

[0052] C. Other Embodiments:

[0053] (C1) The rotational molding die 10 of the first embodiment is described by taking as an example a die having a structure in which six rectangular mounting frames 21 arranged in a rectangular parallelepiped shape in the frame body 20 are fitted with rectangular molding dies 30, and the rotational molding die 10B of the second embodiment is described by taking as an example a die having a structure in which eight mounting frames 21B arranged in an octahedron shape in the frame body 20B are fitted with triangular molding dies 30B. However, it is not limited thereto, and it may be a die having a structure in which a plurality of molding dies are fitted in a plurality of mounting frames arranged in various polyhedron shapes in the frame body. Moreover, it is not necessary to limit to a die using a frame body having a structure in which one mounting frame is arranged along each surface of the polyhedron, and any die using a frame body having a plurality of mounting frames and becoming a hollow shape by fitting molding dies in each mounting frame may be used.

[0054] (C2) In the above embodiment, a structure in which a heat insulating portion is provided so as to cover the surfaces of the mounting frames facing the inner space side of the rotational molding die and portions other than the molding portions of the molding dies is described as an example, but the heat insulating portion may be omitted. In the case where the heat insulating portion is omitted, useless portions may be molded around the molded product, and a process of removing the generated useless portions may sometimes be required. However, except for this point, the same effects as those of the embodiment can be obtained.

[0055] (C3) In the above embodiment, the plurality of fitted molding dies are described by taking as an example molding dies all having the same-shaped molding portions. However, it is not limited thereto. For example, in the rotational molding die 10 of the first embodiment, as the six fitted molding dies, three molding dies of two types having different molding portions may be used, or two molding dies of three types having different molding portions may be used, or one molding die of six types having different molding portions may be used. Moreover, three of one type among the three different molding dies may be used, two of another type may be used, and one of the remaining type may be used. That is, as the plurality of fitted molding dies, they may be composed of one type of molding die or two or more different types of molding dies. In the case where the plurality of molding dies are composed of one type of molding die, a plurality of one type of molded product can be molded simultaneously, and in the case where the plurality of molding dies are composed of two or more different types of molding dies, a plurality of different types of molded products can be molded simultaneously. Thereby, an increase in cost can be suppressed, and production in small quantities and of multiple varieties can be carried out. Moreover, during the development process, for design changes, it is possible to respond in a short period of time, and it is possible to achieve suppression of cost increase and shortening of the development period.

[0056] The present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from its gist. For example, the technical features of the embodiments corresponding to the technical features in each of the embodiments described in the Summary of the Invention can be appropriately replaced or combined in order to solve part or all of the above problems, or to achieve part or all of the above effects. Moreover, as long as the technical feature is not described as an essential feature in this specification, it can be appropriately deleted.

Claims

1. A rotational molding die for rotational molding, capable of molding multiple molded products, wherein, the rotational molding die includes: a frame having a plurality of fitting frames; and a plurality of molding dies each having a molding portion for molding a molded product, and being respectively assembled such that the molding portion faces the inner space of the rotational molding die, the rotational molding die further includes a heat insulating portion that covers portions of the inner surfaces of the respective molding dies facing the inner space other than the molding portions and the inner surfaces of the respective fitting frames facing the inner space, the heat insulating portion is a member whose surface temperature is less than the melting temperature of the molding material when heated to a temperature above the melting temperature of the molding material.

2. The rotational molding die according to claim 1, wherein the plurality of molding dies are composed of one type of molding die or two or more different types of molding dies.

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