Mold equipment
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- INOAC CORP
- Filing Date
- 2025-03-28
- Publication Date
- 2026-07-02
Smart Images
Figure 0007884109000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a mold device and a vehicle seat cushion.
Background Art
[0002] There is known a mold device including a first mold and a second mold, in which a hole forming protrusion of the first mold is abutted against a protrusion facing portion of the second mold in a cavity to form a through hole in a molded product (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] The present application discloses a novel technique related to a molded product.
Means for Solving the Problems
[0005] One aspect of the invention is a mold device including a first mold and a second mold that have a cavity therebetween and are opened and closed, a hole forming protrusion provided on the first mold, and a protrusion facing portion provided on the second mold against which the hole forming protrusion abuts, for forming a through hole in a molded product formed in the cavity, wherein at least one of the contact portions of the hole forming protrusion and the protrusion facing portion is provided with an elastic member that is elastically compressed when the mold is closed.
Brief Description of the Drawings
[0007] [First Embodiment] Figure 1 shows the mold apparatus 10 of this embodiment. The mold apparatus 10 is used to mold the molded product 50 shown in Figure 2. The molded product 50 has through holes 51. For example, the molded product 50 has a flat shape such as a plate, and the through holes 51 extend in the direction of its thickness.
[0008] Examples of molded articles 50 include those made of resin or elastomer. The resin constituting the molded article 50 may be a thermosetting resin or a thermoplastic resin. Examples of such resins include polyurethane resins and polyolefin resins (e.g., polyethylene resin and polypropylene resin). Examples of elastomers constituting the molded article 50 include rubber and thermoplastic elastomers.
[0009] The molded product 50 may be a foam or a non-foamed material. The foam may have a closed-cell structure or an open-cell structure. In this embodiment, the molded product 50 is a foamed polyurethane resin. The polyurethane resin may be a flexible polyurethane resin or a rigid polyurethane resin.
[0010] The molded product 50 may be used, for example, in vehicles or other vehicles, or in buildings. In this embodiment, the molded product 50 is used in a vehicle seat cushion 90, for example, as a pad that constitutes the seat portion that supports the buttocks of the sitter. The through-hole 51 is used, for example, as a ventilation hole in the seat cushion 90's ventilation system (for example, communicating with a duct built into the seat). The foamed molded product 50 may also be a pad for a seat cushion applied to the backrest portion that supports the sitter's back. The use, shape, and material of the molded product 50 are not limited to the examples described above.
[0011] As shown in FIG. 3, the mold device 10 is divided into a first mold 71 and a second mold 72 (vertically divided in this embodiment), and can be arranged in a mold-closed state where they are combined (see FIG. 1) and a mold-open state where they are separated (see FIG. 3). In the mold device 10, the molded product 50 is foam-molded in a cavity 73 formed between the first mold 71 and the second mold 72 in the mold-closed state (see FIG. 4).
[0012] As shown in FIG. 1, in the first mold 71, a hole-forming protrusion 21 for forming the through-hole 51 of the molded product 50 in the cavity 73 is protrudingly formed. In the second mold 72, a protrusion opposing portion 22 that abuts against the hole-forming protrusion 21 of the first mold 71 in the mold-closed state is provided. In the example of this embodiment, the protrusion opposing portion 22 is a portion that protrudes like the hole-forming protrusion 21 (see FIG. 3), and the protruding tip surface of the hole-forming protrusion 21 and the protruding tip surface of the protrusion opposing portion 22 are abutted in the mold-closed state (see FIG. 1). Note that the protrusion opposing portion 22 does not have to protrude as long as it is a portion that abuts against the hole-forming protrusion 21 in the mold-closed state. For example, it may be a flat surface or a concave portion that receives the protruding tip of the hole-forming protrusion 21.
[0013] An elastic member 30 is provided on at least one of the contact portions between the hole-forming protrusion 21 and the protrusion opposing portion 22 (see FIGS. 5A and 5B). In the example of this embodiment, the elastic member 30 is provided at the protruding tip portion of the hole-forming protrusion 21 and is not provided on the protrusion opposing portion 22. In addition to or instead of providing the elastic member 3 on the hole-forming protrusion 21, it can also be provided on the protrusion opposing portion 22 (for example, it can also be provided at the protruding tip portion of the protruding protrusion opposing portion 22).
[0014] When the mold device 10 changes from the mold-open state (see FIG. 5A) to the mold-closed state (see FIG. 5B), the hole-forming protrusion 21 and the protrusion opposing portion 22 are abutted, and the elastic member 30 is elastically compressed. Then, when the foamed resin injected into the cavity 73 foams and the molded product 50 is molded, the through-hole 51 is molded (see FIG. 6).
[0015] ]The elastic member 30 may be made of, for example, an elastomer or a foamed resin. Examples of the elastomer constituting the elastic member 30 include rubber and thermoplastic elastomer. When the elastic member 30 is a foam, it preferably has a closed-cell structure from the viewpoint of sealing performance.
[0016] In the example of the present embodiment, the main body portion excluding the elastic member 30 and the protrusion facing portion 22 of the hole forming protrusion 21 are columnar (for example, cylindrical), and the protruding tip end surfaces thereof are configured to have substantially the same cross-sectional shape and substantially the same cross-sectional area, and are coaxially arranged. Further, in the example of the present embodiment, the elastic member 30 is configured to have substantially the same cross-sectional shape and substantially the same cross-sectional area as those when it is sandwiched and compressed between the main body portion of the hole forming protrusion 21 and the protrusion facing portion 22 in the mold closed state (see FIG. 5B). In this case, the elastic member 30 has a size that fits inside the outer peripheral surface of the main body portion of the hole forming protrusion 21 before being compressed (see FIG. 5A). Note that the elastic member 30 may have a size that protrudes outward with respect to the main body portion or the protrusion facing portion 22 of the hole forming protrusion 21 in the mold closed state (in this case, it may have a size that does not protrude in the mold open state), or may have a size that retracts inward. In the former case, an annular recess is formed on the inner peripheral surface of the through hole 51 of the molded product 50. In the latter case, an annular protrusion is formed on the inner peripheral surface of the through hole 51 of the molded product 50.
[0017] Here, in a conventional mold device for manufacturing a molded product having a through hole, due to wear caused by repeated use of the hole forming protrusion for forming the through hole, or due to the resin pressure in the cavity, etc., a gap may occur between the hole forming protrusion 21 and the protrusion facing portion 22. Then, when the resin of the molded product enters the gap, there may occur a problem that the hole formed by the hole forming protrusion is blocked halfway without penetrating the molded product.
[0018] In contrast, the mold device 10 is equipped with an elastic member 30 that is elastically compressed when the mold is closed, on at least one of the hole-forming projection 21 of the first mold 71 and the projection-facing projection 22 of the second mold 72. Therefore, even if the hole-forming projection 21 wears down or resin pressure is applied during molding, the elastic force of the elastic member 30 keeps the hole-forming projection 21 and the projection-facing projection 22 pressed against each other (see Figure 5B), making it easy to form a through hole 51 that penetrates the molded product 50 (see Figure 6). Furthermore, conventionally, resin would easily enter the gap between the hole-forming projection 21 and the projection-facing projection 22, forming burrs inside the through hole 51 of the molded product. As a result, removing the burrs was time-consuming. In contrast, with the mold device 10 of this embodiment, the elastic force of the elastic member 30 presses the hole-forming projection 21 and the projection-facing projection 22 against each other, making it difficult for gaps to form between them, thus suppressing the generation of burrs and reducing the effort required to remove them. Furthermore, by using, for example, an elastomer-based elastic member 30, it becomes possible to reduce costs and also make replacement easier.
[0019] [Second Embodiment] Figure 7A shows a mold apparatus 10 of the second embodiment. In this embodiment, a recess 23 is formed on the surface (protruding tip) of the hole-forming projection 21 that faces the projection-facing portion 22, into which an elastic member 30 is fitted and fixed. The elastic member 30 is positioned so that its base end is fitted into the recess 23 and its tip protrudes from the recess 23 toward the tip side of the hole-forming projection 21. A recess 24 is also formed on the surface of the projection-facing portion 22 that faces the hole-forming projection 21. When the mold apparatus 10 is in the closed state and the hole-forming projection 21 and the projection-facing portion 22 come into contact, the elastic member 30 is received in the recess 24 of the projection-facing portion 22 and is elastically compressed between the bottom surface of the recess 23 and the bottom surface of the recess 24 (see Figure 7B).
[0020] In this embodiment, in the closed mold state, the opening edge of the recess 23 of the hole-forming projection 21 and the opening edge of the recess 24 of the projection-facing portion 22 are arranged with a gap between them. Therefore, when the molded product 50 is formed in the cavity 73 (see Figure 8A), an annular projection 51T is formed on the inner circumferential surface of the through hole 51 (see Figure 8B). The size (thickness) of the annular projection 51T in the through-direction of the through hole 51 may be large, equal to, or small relative to its projection amount (amount of projection into the through hole 51). The annular projection 51T may have a rectangular cross-section or other shapes. For example, when the elastic member 30 is compressed in the closed state and bulges laterally between the opening edge of recess 23 and the opening edge of recess 24, a concave surface, such as an arc-shaped cross-section, is formed on the protruding tip surface of the annular projection 51T toward the inside of the through hole 51 (a concave surface is formed in which the middle portion of the through hole 51 in the penetrating direction is recessed from both ends).
[0021] The other configurations of this embodiment are the same as those of the first embodiment described above. This embodiment can also achieve the same effects as the first embodiment. In this embodiment, since the elastic member 30 is fitted into the recess 23 and fixed, it is possible to suppress the elastic member 30 from coming off. In addition, since the elastic member 30 is fitted into the recess 23 of the hole-forming projection 21 and the recess 24 of the projection-facing portion 22 when the mold is closed, it is possible to suppress displacement of the elastic member 30 when compressed. This makes it possible to sufficiently maintain the pressing state between the hole-forming projection 21 and the projection-facing portion 22. Furthermore, by simply providing the elastic member 30 so that a gap is provided between the opening edge of the recess 23 of the hole-forming projection 21 and the opening edge of the recess 24 of the projection-facing portion 22 when the mold is closed, it is possible to easily form an annular projection 51T on the inner circumferential surface of the through hole 51 of the molded product 50. Note that in this embodiment, it is also possible to omit either the recess 23 or the recess 24.
[0022] [Third Embodiment] Figure 9A shows a mold apparatus 10 of the third embodiment. In this embodiment, a recess 23 is formed on the surface (protruding tip) of the hole-forming projection 21 that faces the projection-facing portion 22, into which the elastic member 30 is fitted and fixed. In this embodiment, however, no recess is formed on the surface of the projection-facing portion 22 that faces the hole-forming projection 21.
[0023] In this embodiment, the elastic member 30 has its base end fitted into the recess 23, and its tip protrudes from the recess 23 toward the tip of the hole-forming projection 21, and is positioned outside the recess 23. The tip of the elastic member 30 has a larger cross-sectional area than the base end, and a flange portion 32 that protrudes laterally is formed thereon. When the mold device 10 is in the closed state, the flange portion 32 is sandwiched between the opening edge of the recess 23 of the hole-forming projection 21 and the projection-facing portion 22, and protrudes outward from the outer circumferential surfaces of the hole-forming projection 21 and the projection-facing portion 22 (see Figure 9B).
[0024] Then, when the mold device 10 is closed and the molded product 50 is formed in the cavity 73 (see Figure 10A), the flange portion 32 of the elastic member 30 forms an annular recess 51U on the inner circumferential surface of the through hole 51 of the molded product 50 (see Figure 10B).
[0025] Other configurations of this embodiment are the same as those of the first embodiment described above. This embodiment can also achieve the same effects as the first embodiment. In this embodiment, the flange portion 32 of the elastic member 30 is provided outside the recess 23, and when the elastic member 30 is compressed in the closed mold state, there is room for the flange portion 32 to bulge outward and escape. This makes it possible to compress the elastic member 30 more easily compared to the case where substantially the entire elastic member 30 is fitted inside the recess 23. Therefore, it is possible to reduce the force pressing the hole-forming projection 21 and the projection-facing portion 22, and to reduce the load on the hole-forming projection 21 and the projection-facing portion 22.
[0026] Furthermore, in this embodiment, by simply providing a flange portion 32 on the elastic member 30, it becomes possible to easily form an annular recess 51U on the inner circumferential surface of the through hole 51 of the molded product 50. Generally, when forming an annular recess 51U on the inner circumferential surface of the through hole 51 of the molded product 50, the portion in which the recess 51U is formed becomes an undercut shape (see Figure 10A), which can make it difficult to demold the molded product 50. In contrast, in the mold device 10 of this embodiment, when the mold is opened, the compressed elastic member 30 recovers, and the lateral bulge of the flange portion 32 decreases, making it easier to remove the hole-forming projection 21 from the through hole 51 of the molded product 50. In this way, by forming the annular recess 51U on the inner circumferential surface of the through hole 51 with the elastic member 30, which is elastically compressed and bulges laterally when the mold is closed, and recovers and the lateral bulge decreases when the mold is open, it becomes possible not only to easily form the annular recess 51U but also to easily demold the product. For example, if the elastic member 30 is sized such that it does not protrude on the outer surface of the hole-forming projection 21 when uncompressed (in the open mold state), demolding can be made easier. In the case of a molded product 50 used in a seat cushion, it is conceivable that the inner surface of the through hole 51 may bulge inward and narrow the through hole 51 when subjected to a load by a seated person. However, by providing an annular recess 51U on the inner surface of the through hole 51 (especially in the center in the direction of penetration), it is possible to suppress the inward bulging of the inner surface of the through hole 51 and thus prevent the through hole 51 from narrowing.
[0027] [Fourth Embodiment] Figure 11A shows a mold apparatus 10 of the fourth embodiment. The mold apparatus 10 is equipped with a movable mechanism 60 that has at least a portion of the hole-forming projection 21 of the first mold 71 and the projection-facing portion 22 of the second mold 72 as a movable part 61 that can reciprocate in the mold closing direction of the mold apparatus 10. The movable mechanism 60 is equipped with an elastic member 30 that biases one of the movable parts 61 of the hole-forming projection 21 and the projection-facing portion 22 toward the other side. In this embodiment, the elastic member 30 is a compression coil spring, but as in the first embodiment, it may be made of elastomer or foamed resin.
[0028] In this embodiment, the movable part 61 of the movable mechanism 60 is provided only on the hole-forming projection 21 of the hole-forming projection 21 and the projection-facing projection 22, but it may be provided on both, or only on the projection-facing projection 22.
[0029] In this embodiment, the movable mechanism 60 includes a support projection 62 provided on the first mold 71 and a movable sleeve 63 as a movable part 61 that is linearly movable and fitted to the outside of the support projection 62. The movable sleeve 63 has a bottomed cylindrical shape at one end, and the open end of the cylindrical shape is fitted to the outside of the support projection 62. The elastic member 30 is positioned between the tip surface of the support projection 62 and the inner surface of the bottom wall of the movable sleeve 63. Note that the support projection 62 does not need to be provided if the first mold 71 is provided with a recess into which the movable sleeve 63 is fitted. In this case, a compression coil spring (elastic member 30) is sandwiched between the bottom surface of the recess and the inner surface of the bottom wall of the movable sleeve 63.
[0030] In this embodiment, when the mold device 10 is closed, the elastic member 30 is elastically compressed, and one of the movable parts 61 of the hole-forming projection 21 and the projection-facing part 22 (in this example, the movable sleeve 63 of the hole-forming projection 21) is pressed against the other (see Figure 11B). Then, when the molded product 50 is formed in the cavity 73, the through hole 51 is formed.
[0031] Other configurations of this embodiment are the same as those of the first embodiment described above. This embodiment can also achieve the same effects as the first embodiment. In this embodiment, since the elastic member 30 is housed in the movable sleeve 63, deterioration of the elastic member 30 can be suppressed. Furthermore, by using a metal compression coil spring for the elastic member 30, for example, durability can be improved compared to an elastomer or foamed resin elastic member 30.
[0032] [Fifth Embodiment] Figure 12A shows a mold apparatus 10 of the fifth embodiment. In this embodiment, the elastic member 30 in the first embodiment is a compression coil spring, and for example, one end of the compression coil spring is welded to the projection-facing portion 22. In this embodiment as well, when the mold apparatus 10 is in the closed state, the hole-forming projection 21 and the projection-facing portion 22 come into contact and the elastic member 30 is elastically compressed (see Figure 12B). Then, when the molded product 50 is formed in the cavity 73, the through hole 51 is formed (see Figure 13A).
[0033] In this embodiment, since the elastic member 30 is a compression coil spring, it is conceivable that the resin of the molded product 50 may enter the inside of the compression coil spring during molding. Therefore, it is preferable that the gap into which the resin enters is small when the compression coil spring is compressed in the closed mold state, for example, it is preferable that it is in a state of maximum compression or close to maximum compression. For example, if the molded product 50 is a foam, even if some resin enters the inside of the compression coil spring, it is easy to pull the compression coil spring out of the molded product 50 when the mold is opened. Also, if some resin of the molded product 50 enters the inside of the compression coil spring, for example, a helical projection 51R extending in the axial direction of the through hole 51 is formed on the inner circumferential surface of the through hole 51 of the molded product 50 (see Figure 13B). In the examples shown in Figures 12 and 13, the compression coil spring (elastic member 30) is provided on the projection-facing portion 22 of the second mold 72, but it may also be provided on the hole-forming projection 21 of the first mold 71.
[0034] When removing the molded product 50 from the mold device 10, the following operation can be performed. For example, in the example shown in Figure 13A, after the molded product 50 is molded in the closed state, the first mold 71 located on the upper side is removed upwards to open the mold, and the molded product 50 remains in the second mold 72 located on the lower side. Then, the molded product 50 is removed from the second mold 72 while removing the compression coil spring from the through hole 51 of the molded product 50. This allows the molded product 50 to be removed from the mold device 10. If there is a risk that the compression coil spring may come off the protruding part 22 as it tries to follow the molded product 50 when removing the molded product 50 from the second mold 72, for example, a jig may be inserted through the through hole 51 of the molded product 50 from above, and the molded product 50 may be removed from the second mold 72 while the compression coil spring is pressed down from above by the jig.
[0035] The other configurations of this embodiment are the same as those of the first embodiment described above. This embodiment can also achieve the same effects as the first embodiment. In this embodiment, since the elastic member 30 is a compression coil spring (for example, a metal compression coil spring), it is possible to improve durability compared to when it is an elastomer. According to the mold apparatus 10 of this embodiment, by simply providing a compression coil spring as the elastic member 30 in the hole forming projection 21, it is possible to easily form a helical projection 51R on the inner circumferential surface of the through hole 51 of the molded product 50. In this embodiment, it is possible to reinforce the inner circumferential surface of the through hole 51 of the molded product 50 (for example, a seat cushion, etc.) with the helical projection 51R (it is also possible to make the helical projection 51R function as a reinforcing rib).
[0036] <Note> The following describes the features extracted from the above embodiment, explaining their effects and other aspects as needed.
[0037] For example, the following set of features of this disclosure, relating to a mold apparatus and a vehicle seat cushion, can be considered to have been conceived with the objective of "disclosing a novel technology related to molded products," given the background technology that "a mold apparatus comprising a first mold and a second mold is known, wherein a hole-forming projection of the first mold is abutted against a projection-opposing part of the second mold within a cavity to form a through hole in a molded product (see, for example, Japanese Patent Application Publication No. 2022-26386 (Figure 6C, etc.))." There has been a long-standing need for the development of novel technologies related to mold apparatus, molded products, and methods for manufacturing molded products.
[0038] [Feature 1] A first mold and a second mold, having a cavity between them and being openable and closable, In order to form a through hole in the molded product formed within the cavity, the first mold is provided with a hole-forming projection, A mold apparatus comprising: a second mold provided with a projection-facing portion against which the hole-forming projection abuts; A mold apparatus in which at least one of the contact portions between the hole-forming projection and the projection-facing portion is provided with an elastic member that is elastically compressed when the mold apparatus is closed.
[0039] [Feature 2] A first mold and a second mold, having a cavity between them and being openable and closable, In order to form a through hole in the molded product formed within the cavity, the first mold is provided with a hole-forming projection, A mold apparatus comprising: a second mold provided with a projection-facing portion against which the hole-forming projection abuts; A movable mechanism having at least a portion of the hole-forming projection and the portion opposite the projection as a movable part that can reciprocate in the mold closing direction of the mold device, A mold apparatus comprising: an elastic member provided in the movable mechanism, which biases one of the movable parts of the hole-forming projection and the projection-facing part toward the other side of the hole-forming projection and the projection-facing part.
[0040] [Feature 3] The movable mechanism is provided in the first mold, The aforementioned movable mechanism includes: The support projection provided on the first mold, The movable part includes a movable sleeve having a cylindrical shape with a bottom at one end, and the open end of the cylindrical shape being linearly movable and fitted to the outside of the support projection, The mold apparatus according to feature 2, wherein the elastic member is positioned between the tip surface of the support projection and the inner surface of the bottom wall of the movable sleeve.
[0041] [Feature 4] Recesses are formed on the opposing surfaces of the hole-forming projection and the projection-opposing portion, respectively. The mold apparatus according to feature 1, wherein the elastic member is an elastomer, and is fixed by fitting a portion of it into the recess of one of the hole-forming projection and the projection-facing portion, and is sandwiched between the bottom surfaces of both the hole-forming projection and the projection-facing portion when the mold apparatus is closed.
[0042] [Feature 5] A recess is formed on the surface of the hole-forming projection that faces the portion opposite to the projection. The elastic member is an elastomer, and is fixed by fitting a portion of it into the recess. The mold apparatus according to feature 1, wherein the portion of the elastic member located outside the recess is provided with a flange portion that protrudes laterally and is sandwiched between the opening edge of the recess and the portion facing the projection when the mold apparatus is closed, forming an annular recess in the through hole.
[0043] [Feature 6] A vehicle seat cushion comprising a foamed molded product having through holes, A vehicle seat cushion having an annular recess, an annular projection, or a spiral projection extending in the axial direction of the through hole on the inner surface of the through hole.
[0044] According to the above features, novel technologies related to molded products are provided. With the mold apparatus according to the above features, the hole-forming projection and the projection-opposing part can be pressed together by the elastic force of the elastic member, making it possible to easily form through holes in molded products. In the configuration of Feature 3, the elastic member is housed in a movable sleeve, so deterioration of the elastic member can be suppressed. In the configurations of Features 4 and 5, the elastic member is fitted and fixed in a recess, so it is possible to suppress the elastic member from coming off. According to the configuration of Feature 6, it is possible to provide a vehicle seat cushion with a through hole having an unprecedented inner surface shape.
[0045] While this specification and drawings disclose specific examples of the technology included in the claims, the technology described in the claims is not limited to these specific examples, but also includes various modifications and changes to these examples, as well as parts of the examples taken individually. [Explanation of symbols]
[0046] 10. Mold equipment 21 Hole forming protrusion 22 Opposing part of the projection 23 Recess 24 recesses 30 Elastic members 32 Flange section 50 Molded products 51 Through hole 51 Molding hole 51R protrusion 51T protrusion 51U recess 60 Movable mechanism 61 Moving parts 62 Support protrusion 63 Movable sleeve 71 First mold 72. Second mold 73 Cavity 90 Seat Cushion
Claims
1. A first mold and a second mold, having a cavity between them and being openable and closable, In order to form a through hole in the molded product formed within the cavity, the first mold is provided with a hole-forming projection, A mold apparatus comprising: a second mold provided with a projection-facing portion against which the hole-forming projection abuts; At least one of the contact portions between the hole-forming projection and the projection-facing portion is provided with an elastic member that is elastically compressed when the mold device is closed. Recesses are formed on the opposing surfaces of the hole-forming projection and the projection-opposing portion, respectively. The elastic member is an elastomer, and is fixed by fitting a portion of it into the recess of one of the hole-forming projection and the projection-facing portion, and is sandwiched between the bottom surfaces of both the hole-forming projection and the projection-facing portion when the mold device is closed.
2. A first mold and a second mold having a cavity between them and being openable and closable, In order to form a through hole in the molded product formed within the cavity, the first mold is provided with a hole-forming projection, A mold apparatus comprising: a second mold provided with a projection-facing portion against which the hole-forming projection abuts; At least one of the contact portions between the hole-forming projection and the projection-facing portion is provided with an elastic member that is elastically compressed when the mold device is closed. A recess is formed on the surface of the hole-forming projection that faces the portion opposite to the projection. The elastic member is an elastomer, and is fixed by fitting a portion of it into the recess. The mold apparatus is provided with a flange portion in the part of the elastic member located outside the recess that protrudes laterally and is sandwiched between the opening edge of the recess and the part facing the projection when the mold apparatus is closed, forming an annular recess in the through hole.