Injection molding mold

Abstract

To prevent deformation, scratching or the like when injection-molding a flat plate-like molded product such as a game board.SOLUTION: There is provided a mold for injection molding, in which flat surfaces 15 and 16 for molding a flat plate-like molded product 1 are formed on a facing surface of a fixed mold 11 and a movable mold 14 which are perpendicular to an opening and closing direction of the mold. Mold members 17a to 17d and 17f for molding a peripheral edge portion 2 of the flat plate-like molded product 1 are arranged so as to slide obliquely outward with respect to the opening and closing direction of the mold. A pressing surface 27 substantially parallel to the flat surfaces 15 and 16 is formed in the mold member. When the mold member is slid obliquely outward, the pressing surfaces 27 press the peripheral edge portion 2 of the flat plate-like molded product 1 to detach the flat plate-like molded product 1 from the flat surfaces 15 and 16.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a mold for injection molding flat resin game boards to be installed inside gaming machines such as pachinko, arrange balls, and mahjong balls, or other flat resin molded products. [Background technology]

[0002] As is well known, the game board of a pachinko machine has two guide rails attached to its surface that guide game balls into the play area, and game components such as a symbol-changing display device and a prize-winning device are arranged in the play area surrounded by the guide rails. These game components are surrounded by obstacles such as nails and windmills, which function to change the path of the game balls as they fall through the play area. Plywood has traditionally been used as the material for constructing game boards. However, due to the drawbacks of plywood, which is prone to product defects due to deformation, and the difficulty of obtaining innovative designs, game boards made of synthetic resin have gradually been used in recent years. Transparent synthetic resin game boards, in particular, have the advantage that by placing symbol-changing displays and various decorative elements on the backside, players can see through these elements during play, allowing for innovative designs and a variety of presentations.

[0003] Generally, game boards require pre-formed positioning sections to be accurately fixed to the main frame. However, by molding game boards using injection molding, these positioning sections can be simultaneously formed on the game board, and the number of areas requiring post-processing such as drilling and cutting can be reduced, which has the advantage of being more suitable for mass production than game boards molded using extrusion molding.

[0004] On the other hand, since the shape of the gaming board varies depending on the manufacturer of the gaming machine, or even for each product made by the same gaming machine manufacturer, injection molding requires that a mold be made each time according to the shape of the gaming board, which results in the problem of high mold costs. To address this problem, the invention of an injection molding mold shown in Patent Document 1 below makes it possible to reduce costs by simply replacing the insert part that corresponds to the outer periphery of the gaming board, even if the outer shape of the gaming board is different, without the need to make a new mold. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-208337 Summary of the Invention [Problem to be solved by the invention]

[0006] Since a game board has a flat portion that holds a large number of game nails, the flat portion must be approximately 10 mm thick and have a flat, deformation-free surface on both sides. Transparent game boards, in particular, require a mirror-like finish without scratches to prevent diffuse reflection and maintain visibility. Therefore, when molding game boards by injection molding, it is necessary to avoid applying forces that could cause deformation, especially when removing the molded product from the mold immediately after molding. Conventional molds generally use ejector pins to eject the molded product. However, because the ejector pins only press the molded product locally, this can deform the molded product before it has fully hardened. Or, the molded product may not be cooled uniformly in the mold, resulting in uneven thermal shrinkage and deformation. Furthermore, since the tip of the ejector pin leaves a mark where it abuts the molded product (a circular mark if the abutment surface is circular, or a rectangular mark if the abutment surface is rectangular), if the molded product is transparent, the mark left by the ejector pin can be seen from the front to the back, which makes it difficult to mold high-quality flat-plate molded products. Furthermore, generally, plate-shaped molded products formed using conventional injection molds require a draft angle at the outer periphery to facilitate mold release, and therefore the outer periphery is somewhat sloped. However, when the outer periphery has a draft angle like this, when the outer periphery is used as a positioning part for post-processing such as drilling holes, nailing, or attaching parts to the molded product, a gap is created between the front and back sides of the molded product, making accurate positioning difficult. Furthermore, with the injection molding die shown in Patent Document 1, costs can be reduced simply by replacing the nesting part that corresponds to the outer periphery of the game board, but further cost reductions are required because a large nest consisting of four pieces (top, bottom, left, and right) that form the outer periphery of the game board is required every time the external shape is changed. The present invention is intended to solve such problems. [Means for solving the problem]

[0007] To this end, the present invention is characterized in that an injection molding die in which flat surfaces for molding a flat molded product are formed on opposing surfaces of a fixed die and a movable die that are perpendicular to the mold opening / closing direction, a die member that molds the peripheral portion of the flat molded product is arranged so that it can slide diagonally outward relative to the mold opening / closing direction, and the die member has a pressing surface that is approximately parallel to the flat surface, and by sliding the die member diagonally outward, the pressing surface presses the peripheral portion of the flat molded product, causing the flat molded product to separate from the flat surface. The present invention is also characterized in that the die member has a non-graded surface parallel to the die opening / closing direction. [Effects of the Invention]

[0008] The injection mold according to the present invention can produce high-quality flat-plate molded products that are free from deformation, scratches, etc. Furthermore, it is also easy to mold flat-plate molded products without draft angles, which makes it easier to position the products for post-processing. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a perspective view showing an example of a flat plate-shaped molded product molded by an injection molding die according to the present invention; [Figure 2] FIG. 2 is a perspective view of a corner portion of the rear surface of the flat plate-shaped molded product of FIG. 1. [Figure 3] FIG. 2 is a perspective view of the upper back surface of the flat plate-shaped molded product of FIG. 1. [Figure 4] Cross-sectional view taken along line AA in Figure 1. [Figure 5] Cross-sectional view of line BB in Figure 1. [Figure 6] 1 is a horizontal cross-sectional view of an injection molding die according to the present invention in a closed state. [Figure 7] Cross-sectional view of line CC in Figure 6. [Figure 8] 1 is a horizontal cross-sectional view of an injection molding die according to the present invention in an open state. [Figure 9] Cross-sectional view of line DD in Figure 8. [Figure 10] FIG. 2 is a horizontal cross-sectional view of a mold member of the injection molding die according to the present invention when sliding. [Figure 11] FIG. 11 is an enlarged view of a main part of FIG. 10 . [Figure 12] Cross section of line EE in Figure 10. [Figure 13] FIG. 13 is an enlarged view of a main part of FIG. 12. [Figure 14] FIG. 10 is a vertical cross-sectional view showing another embodiment of an injection molding die according to the present invention in a mold closed state. [Figure 15] FIG. 15 is a vertical cross-sectional view of the injection molding die shown in FIG. 14 during mold opening. [Figure 16] 15 is a vertical cross-sectional view of the injection molding die shown in FIG. 14 in an open state. [Figure 17] FIG. 16 is an enlarged view of a main part of FIG. 15 . [Example]

[0010] Next, an embodiment of the present invention will be described with reference to the drawings. An example of a flat-plate molded product molded using the injection molding die of the present invention is shown in Figures 1 to 5. This flat-plate molded product 1 is a roughly square plate with a thickness of about 10 mm, having a peripheral edge 2 consisting of four sides: side edges 1a and 1b, a bottom edge 1c, and a top edge 1d. Its front and back surfaces 1e and 1f are flat, mirror-like surfaces, and it is molded from a transparent synthetic resin such as polycarbonate resin, ABS resin, or acrylonitrile resin. Reference numeral 3 denotes a gate formed on bottom edge 1c for injecting molten resin into the mold cavity during injection molding; this gate 3 is removed after molding.

[0011] Next, the configuration of the injection molding die for molding the flat plate-like molded article 1 will be described with reference to Figures 6 to 13. This injection molding die comprises a fixed-side mounting plate 10 attached to a fixed platen (not shown) of an injection molding machine via a locating ring 30, a fixed mold 11 fixed to the front surface of the fixed-side mounting plate 10, and a movable mold 14 fixed via a beam member 13 to the front surface of a movable platen 12 so as to face the fixed mold 11. On the opposing surfaces of the fixed mold 11 and the movable mold 14, flat surfaces 15 and 16 for molding the front surface 1e and back surface 1f of the flat plate-like molded article 1 are formed so as to be perpendicular to the mold opening / closing direction, respectively. In the state shown in Figures 6 and 7, the movable mold 14 advances toward the fixed mold 11 and is closed, forming a cavity between the flat surfaces 15 and 16. Molten synthetic resin is then injected into the cavity from the sprue bushing 32 provided on the fixed side mounting plate 10 through the hot runner 31 formed in the fixed mold 11, thereby forming the flat plate-shaped molded product 1.

[0012] Storage sections 18a, 18b are recessed on the outside of both sides of the flat surface 16 of the movable mold 14, and block-shaped mold members 17a, 17b are disposed in the storage sections 18a, 18b for molding both side edges 1a, 1b, which are the peripheral portion 2 of the flat plate-shaped molded product 1. Furthermore, guide holes 19a, 19b are formed through the inner bottoms of the storage sections 18a, 18b, inclined outward at about 15 degrees with respect to the mold opening / closing direction of the movable mold 14, and guide pins 20a, 20b are slidably inserted into the guide holes 19a, 19b. Furthermore, a presser plate 21 consisting of two overlapping flat plates 21a, 21b is disposed inside the beam member 13 and in front of the movable platen 12, and engagement portions 22a, 22b formed at the base ends of the guide pins 20a, 20b are loosely fitted into fastening holes formed in the presser plate 21, and the operating shaft of a fluid pressure cylinder 23 fixed to the presser plate 21 is connected to the movable platen 12, and by extending and contracting the fluid pressure cylinder 23, the presser plate 21 can move forward and backward relative to the movable platen 12. The tip ends of the guide pins 20a, 20b are fixed to the back surfaces of the mold members 17a, 17b. In addition, inner wall surfaces 24a, 24b at the outer portions of the accommodation portions 18a, 18b are formed to be inclined at the same angle as the guide holes 19a, 19b.

[0013] 11, one of the mold members 17b is shown enlarged, and a protruding portion 26 is formed in the mold members 17a and 17b so as to protrude toward the rear surface 1f of the flat plate-shaped molded product 1, and a pressing surface 27 parallel to the flat surface 16 is formed in the protruding portion 26. In addition, the portion of the mold members 17a and 17b, excluding the pressing surface 27, that faces the peripheral edge portion 2 of the flat plate-shaped molded product 1 forms a non-graded surface 25 parallel to the mold opening / closing direction. Although not shown, the mold member for forming the lower side 1c of the flat plate-shaped molded product 1 has a pressing surface parallel to the flat surface 16 and a non-graded surface parallel to the mold opening / closing direction, similar to the mold members 17a and 17b. This mold member is also connected to the pressing plate 21 via a guide pin (not shown), similar to the mold members 17a and 17b.

[0014] 7, a storage section 18d is recessed on the outer side above the flat surface 16 of the movable mold 14, and a mold member 17d is disposed in the storage section 18d to mold the upper edge 1d, which is the other peripheral portion 2 of the plate-shaped molded product 1. A guide hole 19d is formed through the inner bottom of the storage section 18d, inclined outward at about 15 degrees with respect to the mold opening / closing direction of the movable mold 14. A guide pin 20d is slidably inserted into the guide hole 19d, and an engaging portion 22d formed at the base end of the guide pin 20d is loosely fitted into a stop hole formed in the pressure plate 21, and the tip end of the guide pin 20d is fixed to the back surface of the mold member 17d. An inner wall surface 24d at the outer portion of the storage section 18d is inclined at the same angle as the guide hole 19d. As shown enlarged in Figure 13, the mold member 17d forms a pressing surface 27 that is approximately parallel to the flat surface 16 by forming a recessed portion 28 of a constant width extending in the side length direction at the portion facing the upper edge 1d of the flat plate-shaped molded product 1, and the portion facing the peripheral portion 2 of the flat plate-shaped molded product 1 excluding the recessed portion 28 forms a non-graded surface 25 that is parallel to the mold opening and closing direction.

[0015] In an injection mold configured in this manner, molten resin injected into the cavity in the closed mold state shown in Figures 6 and 7 solidifies within the cavity to form the plate-shaped molded product 1. At this time, the protruding portions 26 form linear notches 4 on the peripheral edge of the back surface 1f of the plate-shaped molded product 1, i.e., on the back edges of both sides 1a and 1b, as also shown in Figure 2, and similar notches are also formed on the bottom side 1c of the plate-shaped molded product 1. Furthermore, on the top side 1d of the plate-shaped molded product 1, the recessed portions 28 of the mold member 17d form linear protrusions 5 of a constant width extending in the side length direction, as shown in Figure 3.

[0016] When the mold is opened as shown in FIGS. 8 and 9, the flat plate-shaped molded product 1 is attached to the flat surface 16 of the movable mold 14. When the fluid pressure cylinder 23 is operated in this mold-open state to advance the pressure plate 21, the mold members 17a to 17d are pushed by the guide pins 20a to 20d and slide diagonally outward as shown in FIGS. 10 to 13. At this time, the inner wall surfaces 24a to 24d of the storage portions 18a and 18b are inclined, so they do not interfere with the diagonally outward sliding of the mold members 17a to 17d. As the mold members 17a to 17d slide diagonally outward, the pressure surfaces 27 of the mold members 17a and 17b press the both side edges 1a and 1b of the flat plate-shaped molded product 1 while sliding them outward. The bottom edge 1c is also pressed by the pressure surfaces formed on the mold members in the same manner. Furthermore, the pressing surfaces 27 of the recessed portions 28 formed in the mold member 17d press the upper edge 1d of the plate-shaped molded product 1 via the protruding portions 5. As a result, both side edges and the top and bottom edges of the plate-shaped molded product 1, i.e., the entire peripheral edge 2 of the plate-shaped molded product 1, are simultaneously pressed by the pressing surfaces 27, and a gentle force is applied to the plate-shaped molded product 1 evenly from the periphery, causing the plate-shaped molded product 1 to smoothly separate from the flat surface 16. In this way, the pressing force applied to the plate-shaped molded product 1 is limited to the peripheral edge 2 of the plate-shaped molded product 1 and does not locally press the center of the molded product as with a conventional ejector pin, so there is no risk of the ejector pin leaving a pressing mark. Furthermore, by making the mold members 17a to 17d slide obliquely outward and forming the non-sloped surfaces 25 of the mold members 17a to 17d, both side edges 1a, 1b, bottom edge 1c, and top edge 1d of the flat plate-shaped molded product 1 are molded without any draft slope. This allows the flat plate-shaped molded product 1 to be positioned accurately and with high precision at all times when performing post-processing such as drilling, nailing, or component attachment, or when assembling. Furthermore, forming the pressing surfaces 27 of the mold members 17a to 17d parallel to the flat surface 16 is a necessary configuration to ensure that the pressing surfaces 27 can reliably press the peripheral portion 2 of the flat plate-shaped molded product 1 when the mold members 17a to 17d slide diagonally outward. However, it is sufficient that the pressing surfaces 27 are formed approximately parallel to the flat surface 16, and even a slight inclination less than the angle at which the mold members 17a to 17d slide is acceptable. In this embodiment, the pressing surface 27 is formed on the protruding portion 26, and the pressing surface 27 is formed on the recessed portion 28, but the pressing surface 27 can also be formed without forming such protruding portions or recessed portions on the mold members 17a to 17d. In such a case, the notches 4 and protruding portions 5 as described above are not formed in the flat plate-shaped molded product 1.

[0017] 14 to 17 show an example in which a mold member 17f is provided in the fixed mold 11. That is, in this example, a mold member 17f for releasing the upper edge 1d of the flat surface 15 of the fixed mold 11 from the flat surface 15 is provided on the outer upper part of the flat surface 15. Specifically, a storage section 18f is formed as a recess on the outer side above the flat surface 15, a mold member 17f for molding the upper edge 1d of the flat plate-shaped molded article 1 is disposed in the storage section 18f, a guide hole 19f inclined outward by about 15 degrees is formed in the inner bottom of the storage section 18f, a guide pin 20f formed integrally with the back surface of the mold member 17f is slidably inserted into the guide hole 19f, and a coil spring 21f is disposed in a compressed state in the storage section 18f to bias the mold member 17f in the mold opening direction. 17, the mold member 17f has a recessed portion 28 of a constant width extending in the side length direction at the portion facing the upper edge 1d of the plate-shaped molded product 1, similar to the mold member 17d, to form a pressing surface 27 approximately parallel to the flat surface 16, and the portion facing the peripheral edge 2 of the plate-shaped molded product 1 excluding the recessed portion 28 forms a non-sloped surface 25 parallel to the mold opening direction. In this embodiment, this causes the mold member 17f to slide diagonally outward due to the elasticity of the coil spring 21f as the mold opens, releasing the plate-shaped molded product 1 from the flat surface 15 as shown in FIG. 16. Therefore, in the present invention, the mold member can also be configured to slide diagonally outward due to the elasticity of the coil spring during the mold opening operation, as in this embodiment. In the present invention, as shown in these examples, the mold member for releasing the plate-shaped molded article 1 from the flat surface may be provided on either the fixed mold 11 side or the movable mold 14 side.

[0018] When the flat molded product 1 thus formed is used as a gaming board, the flat molded product 1 is first positioned using at least two surfaces of the peripheral edge 2 that have no draft angle as reference surfaces, and multiple reference holes are drilled. The periphery is then machined to a predetermined shape based on the drilled reference holes, and openings for attaching other board components are drilled. Similarly, a hard coat layer with a design layer is transferred to the surface of the gaming board based on the reference holes, if necessary, and finally, pilot holes for nails are drilled. By machining the periphery of the flat molded product 1, the notches 4 and protrusions 5 can be removed so that they do not remain. As shown in these examples, the injection mold according to the present invention can mold high-quality flat-plate molded products with excellent design, such as transparent game boards. Furthermore, when the injection mold according to the present invention is used to mold a flat-plate molded product as a game board, by going through the above-mentioned processing procedure, it is possible to accommodate game boards of any shape, which has the remarkable effect of making the mold excellent for small-lot production of a wide variety of products. [Explanation of symbols]

[0019] REFERENCE SIGNS LIST 1...flat plate-shaped molded product, 1a, 1b...both sides, 1c...lower side 1, 1d...upper side, 1e...surface, 1f...rear side, 2...periphery, 3...gate portion, 4...notch, 5...protrusion, 10...fixed plate, 11...fixed mold, 12...movable plate, 13...beam member, 14...movable mold, 15, 16...flat surface, 17a to 17d, 17f...mold member, 18a to 18d, 18f...accommodating portion, 19a to 19d, 19f...guide hole, 20a to 20d, 20f...guide pin, 21...pressure plate, 21a, 21b...flat plate, 21f...coil spring, 22a, 22b...engagement portion, 23...fluid pressure cylinder, 24a to 24d...inner wall surface, 25...Non-graded surface, 26...Protrusion, 27...Pressure surface, 28...Concave portion, 30...Locating ring, 31...Hot runner, 32...Sprue bushing

Claims

1. An injection molding die for molding a flat plate-shaped molded product of a constant thickness and flat on both sides, in which flat surfaces perpendicular to the mold opening / closing direction are formed on the opposing surfaces of the fixed and movable molds, wherein a mold member facing the peripheral edge of the flat plate-shaped molded product is arranged on the fixed or movable mold so that it can slide diagonally outward in the mold opening / closing direction, and the mold member is formed with a non-graded surface parallel to the mold opening / closing direction for molding a portion of the peripheral edge face of the flat plate-shaped molded product that has no draft slope, and a pressing surface connected perpendicular to the non-graded surface is formed on the mold member so as to be parallel to the flat surface, and when the mold member is opened, the pressing surface presses the peripheral edge of the flat plate-shaped molded product and causes the flat plate-shaped molded product to separate from the flat surface by sliding the mold member diagonally outward.

2. An injection molding mold as described in claim 1, characterized in that the flat-plate molded product is a square plate consisting of both side edges and upper and lower edges, and mold members that face the peripheral end faces of each side of the flat-plate molded product are arranged in the fixed mold or movable mold, respectively, and when the mold is opened, each mold member slides diagonally outward so that the entire peripheral edge of the flat-plate molded product is pressed simultaneously by the pressing surfaces formed on each mold member.

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