JP2010120186A - Injection molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the variation of molding dimension by reducing the draft angle of a mold and prevent a bulge of a corner generated in mold-releasing from jumping out on the flat surface. <P>SOLUTION: A jumping-out prevention means of a concaved notch 37 for preventing the bulge of the resin generated on the corner part in mold-releasing from the mold from jumping out on the flat surface 32 is provided on the corner part of four corners of the flat surface 32 on the side pushing with an ejector pin in the mold-releasing from the mold by reducing the draft angle of the injection mold and suppressing the variation of the dimension of the inside diameter in the molded article 30 of the rectangular frame 31. The bulge is prevented from jumping out on the flat surface 32 so that the bulge is settled into the concaved notch 37. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plastic injection-molded product molded using a mold, and more particularly to a molded product having a corner and requiring a flat surface.

  One example of an injection molded product having a corner and requiring a flat surface is a molded product having a shape such as a rectangular frame shape or a rectangular bowl shape. Such molded products are used for parts in various fields. For example, the holder shown in Patent Document 1 and the resin locking part shown in Patent Document 2 are one of them.

  The surface on the upper surface side (surface side on which the liquid crystal cell is disposed) of the holder shown in Patent Document 1 and the resin locking portion shown in Patent Document 2 is a flat surface for mounting the optical sheet and the liquid crystal cell. Is required.

  Incidentally, when such a component is formed by a plastic injection molding method, for example, the holder 24 of Patent Document 1 shown in FIG. 6 will be described as an example. Molded with

FIG. 7 is a cross-sectional view of a main part schematically showing a pin gate type mold structure. In FIG. 7, molten resin is injected from the gate 5 into a vacant space provided between the fixed cavity 1 provided with the gate 5 and the movable core 2, and the holder 24 is molded. The movable side core 2 is fixed to the movable side mold plate 4, and a plurality of ejector pins 3 are slidably provided at required portions of the movable side core 2. PL is a parting line and indicates a mating surface of a fixed type and a movable type. The mold shown in FIG. 7 is a pin gate type three plate mold, and the runner and gate are removed by the action of a runner stripper plate (not shown).
Although FIG. 7 shows a pin gate type mold structure, the side gate type mold can also be molded.

  The holder 24 formed by filling the vacant chamber with molten resin is released from the fixed-side cavity when the fixed mold and the movable mold are opened, and remains on the movable core 2 side. Then, the upper surface 24a, which is a flat surface of the holder 24, is pushed out by the ejector pin 3, so that the holder 24 is released from the movable core 2, and a molded product as the holder 24 is obtained.

JP 2008-34241 A (FIGS. 1 and 2) JP 2006-12507 A (FIGS. 2, 5, 6)

In general, an injection molded product is provided with a draft (taper) of 2 ° to 3 ° in the mold, that is, in the fixed mold cavity or the movable side core, in order to improve the releasability from the mold. Therefore, the slope angle is transferred to the molded product, and an inclined surface having an inclination angle of 2 ° to 3 ° appears. Taking the holder 24 as an example, inclined surfaces appear on the inner wall surface and the outer wall surface.
In addition, in order to improve the releasability from the mold, R is particularly applied to the corners.

  In the configuration in which the inclination angle is provided on the inner wall surface of the holder 24, the inner diameter dimension in the inner wall surface greatly varies depending on the position of the inclined surface. Therefore, there arises a problem that it is difficult to set a reference such as positioning. For example, considering the cited document 1, a reflection sheet, a first light guide plate, a second light guide plate, a prism sheet, and the like are stacked and housed inside the holder 24, but there is a problem in positioning accuracy thereof. Will occur and play will occur, and misalignment will appear during installation.

  Where the dimensional accuracy is strictly required, such as the inner diameter of the holder 24, the draft angle of the mold is set to 0 °, or the minute angle close to 0 ° is set to eliminate the inclined surface of the molded product, There is a method for minimizing variations in the inner diameter. In this way, the positioning accuracy of each component to be stored is improved, there is no backlash with each built-in component, and positional deviation at the time of assembly can be eliminated.

  However, when the draft angle of the mold is set to 0 ° or a minute angle close to 0 °, a phenomenon as shown in FIG. 8 occurs. That is, as shown in the enlarged view, at the corners sandwiched between the two sides indicated by a circle A (five places in the figure), a phenomenon that the bulge B occurs and the surface protrudes toward the upper surface 24a appears.

This bulge B appears only at the corner and at the corner that is the included angle, and does not appear at the side away from the corner. In addition, the bulge B appears larger near the inner corner and becomes smaller from the inner corner toward the outer side. Further, this bulge appears larger as the angle of the corner (inner angle) is smaller, and the bulge is smaller as the angle is larger.
The reason why the bulge B appears only at the corners is that the resin shrinks due to cooling of the molten resin, but the resin filled in different directions shrinks while pulling each other at the corners. Since there is no gradient, the release resistance is greatly applied to the resin, and when the mold is released, the resin is still soft, so it is pulled and deformed by the mold in the release direction. Is done.

  The upper surface 24a is required to be a flat surface in order to improve the calm state of the optical sheet or the liquid crystal cell. However, when the bulge B appears on the upper surface 24a at the corner, the optical sheet or the liquid crystal cell becomes less settled, resulting in a problem that the stability is impaired.

  Further, in the configuration in which the corner portion is rounded in order to improve the releasability, for example, when the holder 24 is considered, the size of the holder itself becomes large. A backlight unit used in a mobile phone or the like is required to be thin and short. Therefore, it is not desired that the size of the holder 24 be increased. In addition, the amount of play with built-in parts increases by the amount of R.

  This invention is made | formed in view of said subject, The objective is to obtain the molded article which can ensure flatness without being influenced by the swelling.

  As a means for solving the above-mentioned problems, the feature of the injection molded product of the present invention is that it has a flat surface on the surface side to be pushed out by the ejector pin when released from the mold, and is sandwiched between at least two sides. In an injection-molded product having an open corner and on the side having the flat surface, the inside surrounded by the two sides is open, and the corner of the surface forming the flat surface is separated from a mold. The present invention is characterized in that a pop-out preventing means for preventing a bulge generated at the time of releasing from popping out from the flat surface is provided.

  Flatness of the flat surface can be ensured by providing a protrusion preventing means for preventing the bulge from protruding from the flat surface. Therefore, as described in the background art, the stability of the components placed on the flat surface can be obtained.

  The injection molded product of the present invention is characterized in that the pop-out preventing means is a concave notch provided at the corner.

  Since the bulge generated at the corner can be accommodated in the concave notch, the flat surface is not affected. Further, the concave notch does not protrude from the outside of the corner portion, so that it cannot be seen from the outside. That is, the appearance is not impaired.

  The injection molded product according to the present invention is characterized in that the pop-out preventing means is a notch that is a slope provided at the corner.

  Since the bulge is large on the inside of the corner and decreases as it goes to the outside of the corner, the bulge can be accommodated in the notch if the notch is a slope having a deep inside and a shallow outside. Since the notch that is a slope is not visible from the outside, the appearance is not impaired.

  Further, the injection molded product of the present invention is characterized in that the pop-out preventing means is a slit groove provided in the corner portion.

  A bulge can be stored in the slitting groove. However, since the slitting groove can be seen from the outside, it can be applied to a molded product that does not hinder the appearance even if it can be seen, or a molded product that does not have a functional problem.

  In summary, a molded product that can ensure flatness can be obtained by providing means for preventing bulge and protrusion to a flat surface such as a concave notch, a notched slope, and a slit groove at the corners.

(First embodiment)
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, an injection molded product according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a perspective view of an injection molded product according to the first embodiment of the present invention. 2 is a plan view and an enlarged cross-sectional view of the main part of the injection-molded product in FIG. 1, FIG. 2 (a) is a plan view, and FIG. 2 (b) is a cross-sectional view taken along line EE in FIG. An enlarged view is shown. FIG. 3 is a perspective view showing a main part of another shape of the pop-out preventing means.

The injection molded product according to the first embodiment is a molded product having a rectangular frame shape. In FIG. 1, an injection molded product 30 is a frame 31 having a rectangular shape. The rectangular frame 31 has opposed frame plates 31a, 31b, 31c, and 31d, and these frame plates 31a, 31b, 31c, and 31d are connected and integrated.
Further, the frame 31 has a flat upper surface 32 (in FIG. 1, it is drawn as a surface facing upward). This flat upper surface 32 is in contact with the ejector pin of the mold during injection molding, and the frame 31 is released from the mold by the ejector pin pushing this surface during release. Further, the flat upper surface 32 is a surface on which other assembly parts can be placed stably and stably.
Each frame plate 31a, 31b, 31c, 31d has an inner surface inside. In FIG. 1, only the inner surface 34a of the frame plate 31a and the inner surface 34b of the frame plate 31b are displayed.

Next, in FIG. 2A, each frame plate 31a, 31b, 31c, 31d has a side inside. This side is indicated by side 33a on the frame plate 31a, side 33b on the frame plate 31b, side 33c on the frame plate 31c, and side 33d on the frame plate 31d. These sides represent the sides indicating the respective inner surfaces.
Further, a corner C is provided at a portion where two adjacent sides intersect. For example, there are corners C at the intersections of the sides 33a and 33b, and in FIG.
Further, the inner sides of the respective sides 33a, 33b, 33c, and 33d on the upper surface 32 side are open, and the lower surface side has a shape of an open frame.

  Each corner C has a concave notch 37. As shown in FIG. 2B, the notch 37 has a depth h and a depth m.

  In the injection molded product comprising the frame of the first embodiment, the draft angle of the mold is suppressed to 0 ° in order to reduce the variation in the inner diameter dimension in the frame. Therefore, each inner surface of the frame 31 formed by transfer is erected at a right angle with respect to the upper surface 32.

As described in the background art, when the draft angle of the mold is set to 0 ° or a minute angle close to 0 °, a resin bulge (swell) appears at the corner of the ejector pin on the extrusion surface side. This occurs only at the corners. In particular, when the corners become a narrow angle, the bulge appears large, and when the corners become a wide angle, the bulge is small.
The reason why swelling appears only at the corners is that the resin shrinks due to the cooling of the molten resin, but the resin filled in different directions shrinks while pulling each other, and the draft angle of the mold is It is assumed that there is a large amount of swell due to the fact that there is a great deal of resistance to release from the resin, and the resin is still soft at the time of release and is pulled and deformed by the mold in the release direction. .

In FIG. 2B, B represents the swelling of the resin. In this way, the bulge B appears at the portion where the notch 37 is provided, but the bulge B is housed inside the notch 37, so that it does not jump out to the upper surface 32 which is a flat surface. That is, if the bulge B is accommodated in the notch 37, the flatness of the upper surface 32 is not affected at all.
This notch 37 functions as a pop-out preventing means for preventing the bulge B from popping out from the flat upper surface 32.

The depth h and depth m of the notch 37 are set according to the size of the bulge B. The depth h and the depth m of the notch 37 are appropriately set within a range where the bulge B does not affect the flatness of the upper surface 32.
Since the inner peripheral surface of the notch 37 may be rough in terms of dimensional accuracy, the draft angle of the mold at this portion is set large in consideration of releasability. Further, the inner peripheral surface of the concave notch is preferably formed into a curved shape with no corners. This is because the pulling force between the adjacent resins is reduced due to the shrinkage during cooling of the molten resin.

  In the first embodiment, the concave notch 37 is provided as a protrusion preventing means for preventing the bulge B from jumping out to the flat upper surface 32. However, the protrusion preventing means is not limited to the concave notch. Absent. For example, even the shape as shown in FIG. 3 can serve as a pop-out prevention means. And the same effect can be acquired.

The shape shown in FIG. 3A is a notch 38 that is a slope. The inside of the corner is deep and has a shallow notch as it goes outward.
This is because the bulge is larger on the inner side and the bulge is smaller toward the outer side. What is necessary is just to set the magnitude | size of a slope in the range in which a swelling is fully settled in the notch 38. FIG.

  Also, the shape shown in FIG. The groove width and depth may be set so that the bulge is sufficiently accommodated in the sliding split groove 39.

  As described above, the flatness of the flat upper surface 32 can be improved by providing a bulge-out prevention means having a concave notch 37, a sloped notch 38, a slit groove 39, etc. at the corner C. It can be secured. And even if other flat assembly parts are placed on the upper surface 32, a stable calm state can be obtained.

(Second Embodiment)
Next, an injection molded product according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a perspective view of an injection molded product according to the second embodiment of the present invention.
In FIG. 4, the injection molded product 40 of 2nd Embodiment has shown the support frame 41 which makes | forms a rectangular collar shape. The support frame 41 has frame plates 41a, 41b, 41c, and 41d facing each other, and a bottom plate 41e on the bottom. These are connected together to form a bowl-like shape.

  Each frame plate 41a, 41b, 41c, 41d has two steps on the upper surface side, and the first (upper) upper surface 42 is an ejector pin at the time of mold release in injection molding. Extruded surface. Further, the second step surface 44 is a mounting surface for other assembly parts, and is a flat surface having the same height over the entire circumference except for the corners.

The inner surface of the second step surface 44 has an inner surface (only 46a and 46b are shown in the figure). The inner surface of the step surface 44 is an inner surface with an inclination angle of 0 ° and is perpendicular to the step surface 44. It has a standing surface.
45a and 45b represent sides indicating the inner surfaces 46a and 46b. In the figure, only the side 45a on the frame plate 41a side and the side 45b on the frame plate 41b side are shown, but there are similar sides on the frame plates 41c and 41d side.
In addition, a concave notch 47 is provided at a corner where adjacent sides (for example, side 45a and side 45b) intersect. This notch 47 has four corners.

  In addition, an inner surface (only 43a and 43b are shown in the figure) is provided inside the upper surface 42. This inner surface forms an inclined surface with an inclination angle that is easy to release during injection molding.

  Strict dimensional accuracy is required for the inner diameter dimensions surrounded by the four inner surfaces indicating the inner surfaces 46a, 46b, etc., in view of the arrangement of the assembly parts housed therein. Therefore, the draft angle of the mold is suppressed to 0 ° to be a vertical surface, and the variation in the inner diameter is kept small.

  As described above, when the draft angle of the mold is set to 0 °, the corner portion bulges. However, since the bulge is accommodated in the concave notch 47 also in the second embodiment, it does not jump out on the second step surface 44. Therefore, the flatness of the second step surface 44 is maintained, and the function as a mounting surface for the assembly component can be sufficiently achieved.

As one example of use of the support frame having the above-mentioned shape, for example, a backlight unit of a liquid crystal cell used for a mobile phone or the like can be cited.
In this backlight unit, a liquid crystal cell is disposed on the second step surface 44 of the support frame 41 via an adhesive or the like.
Since the second step surface 44 forms a parallel surface with parallelism maintained, the liquid crystal cell is held under stable calmness.
In addition, an LED, a light guide plate, a reflection sheet, a diffusion sheet, a prism sheet, and the like are positioned and stacked in the interior surrounded by the arranged liquid crystal cell, the four frame plates 41a, 41b, 41c, 41d and the bottom plate 41e. Arranged.

In the backlight unit having such a structure, the inner diameter dimension surrounded by the four inner surfaces 46 indicating the inner surfaces 46a, 46b and the like is a surface formed with a draft angle of 0 °. Therefore, the positioning reference for each component to be stored can be clearly set. And the backlash when arranging each part is suppressed small, and the position gap etc. after an assembly do not occur easily.
Moreover, since the notch 47 is provided inside the inner surface shown by 43a, 43b, etc., light does not leak outside from the notch 47.
Also, the corners of the four corners are not given R. Therefore, the area of the bottom plate 41e can be reduced to the limit of the required space of each component to be arranged, and the overall size of the support frame 41 can be suppressed to a size that is not wasted. That is, shortening is possible.

  As described above, the molded product that is a rectangular frame in the first embodiment and the molded product that is a support frame having a rectangular bowl shape in the second embodiment have been described. However, the configuration of the present invention can be applied to molded products having various other shapes. Is also applicable. For example, as an example, a molded product having a shape as shown in FIG. 5 can also be applied. FIG. 5 is a perspective view showing another shape of the injection molded product.

  5A is a molded product having an L shape, FIG. 5B is a molded product having a U shape, and FIG. 5C is a molded product having an E shape. FIG. 5D shows a molded product having a shape in which a rectangular frame is provided with one opening.

  The configuration of the present invention can be suitably applied to an injection molded product having a corner portion of around 90 ° or less and requiring flatness. FIG. 5 shows a very simple shape product, but a complicated shape product having the above-described conditions can also be applied.

  Further, the shape of the pop-out preventing means described in the first embodiment and the second embodiment can be easily coped with by changing the shape of the mold (movable side core). The structure of the mold is not complicated, and the manufacturing cost of the mold can be kept small.

1 is a perspective view of an injection molded product according to a first embodiment of the present invention. FIG. 2A is a plan view and FIG. 2B is an enlarged cross-sectional view taken along line EE in FIG. 2A. FIG. It is a principal part perspective view which shows the other shape of a pop-out prevention means. It is a perspective view of the injection molded product which concerns on 2nd Embodiment of this invention. It is the perspective view which showed the other shape of the injection molded product. It is a perspective view of the holder shown by patent documents 1. It is principal part sectional drawing which showed typically the metal mold | die structure which shape | molds the holder shown by FIG. It is a perspective view of the holder explaining a problem.

Explanation of symbols

30, 40 Injection-molded product 31 Frame 31a, 31b, 31c, 31d, 41a, 41b, 41c, 41d Frame plate 32, 42 Upper surface 33a, 33b, 33c, 33d, 45a, 45b Side 34a, 34b, 43a, 43b, 46a 46b Inner surface 37, 38, 47 Notch 39 Sliding groove 41 Support frame 41e Bottom plate 44 Step surface B Swelling

Claims (4)

On the surface side that is pushed out by the ejector pin when released from the mold, it has a flat surface, has a corner portion sandwiched between at least two sides, is on the side having the flat surface, and is surrounded by the two sides In the injection molded product where the inside is opened,
An injection-molded article, wherein a projection preventing means for preventing a bulge generated at the time of releasing from a mold from jumping out of the flat surface is provided at the corner portion of the surface forming the flat surface.   The injection molded product according to claim 1, wherein the pop-out preventing means is a concave notch provided in the corner portion.   The injection molded product according to claim 1, wherein the pop-out preventing means is a notch that is a slope provided in the corner portion.   The injection molded product according to claim 1, wherein the pop-out preventing means is a slit groove provided in the corner portion.

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