JPH07276445A - Rib structure of molded piece - Google Patents

Abstract

PURPOSE:To provide a rib structure of a molded piece which satisfies mechanical strength by eliminating thinning tendency of a parent wall of the molded piece and preventing generation of sink marks in ribs and bosses. CONSTITUTION:Ribs 3 to be formed on a parent wall 1 of a molded piece are made of a cross rib. Around the cross of the base of the ribs, thickness relief parts are provided. Only end parts 31 of the rib base are to be connected to the parent wall. Further, a direction of a longer side 32 of a connecting cross section relating to each of the end parts 31 at the rib base to be connected to the parent wall 1 is conformed to a flowing direction of a resin material at the time of molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rib structure of a molded product formed by injection molding, flow stamping molding or the like. In addition to the rib alone, it is also used for the rib structure supporting the boss.

[0002]

2. Description of the Related Art In injection molding, flow stamping molding or the like, when mounting and reinforcing ribs are provided, sink marks are likely to appear on the opposite side of the ribs. Especially, it is remarkable for materials with large molding shrinkage such as polyethylene, polypropylene and polyacetal. Conventionally, the following methods have been adopted as measures against such sink defects. For example, it is a method of ensuring a thickness three times or more the thickness t of the rib 3. Mother wall thickness a
When the wall thickness a is three times or more (prior art 1) or the wall thickness a is thin, the wall thickness a1 near the rib 3 is limited to 2 as shown in FIG.
-3 times the thickness is ensured with a gentle gradient (prior art 2). Alternatively, as shown in FIG. 7, the rib base wall thickness a2 may be thinned to 0.8 to 1.0 times the rib thickness t (prior art 3), or as shown in FIG. This is a method of reducing the wall thickness t1 of (prior art 4).

[0003]

However, the conventional countermeasures against sink marks have been insufficient. Prior art 1 has not been able to meet the demand while the wall thickness a of the general part tends to be thinned in order to reduce the cost of the molded product. In addition, the prior arts 2 and 3 were not direct measures to prevent sink marks, but were rather close to methods of making them inconspicuous even if there were sink marks for the purpose of blurring. There were some sink marks and gloss. Then, in Conventional Technique 3, the root of the rib 3 is thin and the mechanical strength is reduced.
In the prior art 4, the root of the rib 3 is thin, the mechanical strength of the rib itself is lowered, and the rib is prone to collapse. The boss provided on the mother wall 1 also faced the same problem as the rib 3 described above.

The present invention is intended to solve the above-mentioned problems, and in response to the tendency of the wall thickness of a molded product to be thin, a molded product satisfying mechanical strength while taking measures to prevent sink marks on ribs and bosses is provided. It is intended to provide a rib structure.

[0005]

The rib structure of a molded article according to the first aspect of the present invention is a rib formed on a mother wall of a molded article, wherein the rib is a cross rib, and the rib is formed around the intersection of the rib roots. It is characterized in that a sluice is provided and only the end of the rib root is connected to the base wall. Here, “meat slime” refers to a through hole formed by a slide core or the like at the root of the rib. The "cross ribs" are formed by crossing two or more flat pieces and integrally formed with the mother wall. Specifically, the cross-sectional shape means a cross shape, a Y shape, or the like. The rib structure of the molded article according to the second aspect of the present invention provides a plurality of ribs on the side wall of the boss, supports the boss so that the rib separates the bottom surface of the boss from the mother wall, and further, only the end of the rib root is It is characterized by being connected to the mother wall. The rib structure of the molded product of the third invention is the first invention or the second invention, wherein the long side direction of the coupling cross section relating to the end of the rib root coupled to the mother wall is the flow direction of the resin material during molding. The feature is that they are matched.

[0006]

According to the rib structure of the molded product according to the first aspect of the present invention,
Since the ribs are crossed with each other and a meat thin portion is provided at the base of the ribs and the ribs are joined to the mother wall at the ends, the ribs are supported at multiple points. By this multi-point support, the mechanical strength can be maintained, and further, the rib thickness can be set to about 1/3 of the mother wall thickness,
No sink marks. Further, as in the second aspect of the present invention, when a plurality of ribs are provided on the side wall of the boss and the ribs support the boss so that the bottom surface of the boss is separated from the mother wall, the occurrence of sink marks due to the formation of the boss does not occur. Disappear. Since only the end of the rib root is connected to the base wall, no sink mark is produced as in the first aspect of the present invention. Further, as in the third aspect of the present invention, in the rib structure of the molded article of the first and second aspects of the invention, the long side direction of the coupling cross section related to the end of the rib root is made to coincide with the flow direction of the resin material during molding. Then, the flow of the resin material at the time of molding is improved, the pressure is smoothly transmitted, and the occurrence of sink marks can be more reliably prevented.

[0007]

EXAMPLES The present invention will be described in detail below based on examples. (1) Rib Structure of Molded Product Example 1 FIG. 1 shows an example of a rib structure of a molded product according to this example, which is applied when a boss is formed on a thin wall. Reference numeral 1 indicates a mother wall that forms a flat portion in the mother body of a molded product made of polypropylene resin. The wall thickness a of the mother wall is thin to reduce the cost. Reference numeral 2 denotes a cylindrical boss provided for the purpose of reinforcement around the hole or fitting margin when combined with other parts. A rib 3 is provided on the side wall of the boss 2.

Four ribs 3 are provided so as to cross each other at right angles, and prevent the boss 2 from falling. Boss 2
The rib 3 is centered on the intersection axis formed by the ribs 3 intersecting each other.
It is integrated with. The rib 3 supports the boss 2 in a state where the bottom surface of the boss 2 is separated from the base wall 1 and the boss 2 is floated. At the root of the rib, only the outer end 31 is connected to the base wall 1. Such a shape can be formed by molding using a slide core of a known technique. The wall thickness t of the rib 3 is about 1/3 times the wall thickness a of the mother wall and is 0.7 mm. Further, the length of the long side 32 of the coupling cross section related to the end portion 31 is 3 mm.

Embodiment 2 As shown in FIG. 2, this embodiment has a cross rib structure having a Y-shaped cross section. FIG. 2 is a perspective view of the rib 3 as seen from the root side, and the mother wall 1 is omitted. In the figure, the hatched portion indicates a connecting portion with the mother wall 1. A slime is provided around the intersection of the roots of the ribs 3 and is cut out in an arch shape. Only the end portion 31 (hatched portion) at the base of the rib is connected to the base wall 1. The length of the long side 32 of the connecting cross section related to the end 31 is 0.5 to 1.0 times the wall thickness a of the mother wall. Also,
The wall thickness t of the rib 3 is about 1/3 times the wall thickness a of the mother wall.
Similar to Example 1, it is a polypropylene resin molded product.

Embodiment 3 In this embodiment, as shown in FIGS. 3 and 4, a rib structure of a molded product using cross ribs having a cross-shaped cross section is used, but the mother wall 1 is supported at three points. FIG. 3 is a perspective view as seen from the root side of the rib 3 like FIG. 2, and the mother wall 1 is omitted. Figure 4
[Fig. 4] is a front view showing how ribs 3 are attached to the mother wall 1. The wall thickness a of the mother wall 1 is 2 mm, and the wall thickness t of the rib 3 is 0.7.
mm, the length 32 of the long side of the joint cross section according to the end 31 of the rib 3 is 2 mm. By the way, the height H of the rib 3 is 9 m.
The width m is 6 mm.

Embodiment 4 This embodiment is shown in FIG. A cross rib similar to that of the third embodiment is used, and a boss 2 having a cross axis as a central axis is integrally provided with the rib 3. In addition, in the present embodiment, the direction of the long side 32 of the connecting cross section of the rib base end 31 that is connected to the base wall 1 is made to coincide with the flow direction of the resin material during molding (arrow in the figure). Therefore, the three ends 31 are oriented in a fixed direction. By setting the flow direction of the resin material, sink marks are less likely to appear. Long side 32
The length is extended in the flow direction of the resin material as needed. The rib thickness t is preferably about ⅓ times the base wall thickness a. However, since the rib is required to have strength, a preferable range is 0.33 a or more and 1.2 mm or less. In the fourth embodiment, the structure of the rib 3 holding the boss 2 is described. However, with the rib 3 alone, the direction of the long side 32 of the connecting cross section related to the end 31 of the rib root is the flow direction of the resin material during molding. It can also be adjusted to

(2) Effects of the Embodiments According to the rib structure of the molded product having the above-described aspect, the rib 3
Since the wall thickness t of the rib 3 is set to about 1/3 of the wall thickness a and the meat sluice is provided at the base of the rib 3, the sink mark is not generated. Therefore, sink preventive measures can be taken without increasing the wall thickness a of the mother wall. Further, since the rib structure supports multiple points, the mechanical strength can be maintained. In addition, Example 1,
In No. 4, since the boss 2 is supported by the rib 3 of this kind in a state of being separated from the mother wall 1, the sink mark due to the formation of the boss 2 does not occur. Furthermore, in the fourth embodiment, since all the long sides 32 of the cross section of the rib root end 31 connected to the mother wall 1 are made to coincide with the flow direction of the resin material during molding, the flow of the resin material is good. And, the sink mark has disappeared. Rib 3
When the ribs 3 are installed at right angles to the direction of the long side 32 with respect to the flow direction of the resin material, sink marks are likely to appear. It is hard to get a sink because it is along.
Thus, it is not necessary to change the molding conditions such that the shrinkage is reduced by increasing the injection and pressure holding time or the cooling time to eliminate sink marks, and the quality can be maintained without lowering the productivity.

The present invention is not limited to those shown in the above embodiments, but can be variously modified within the scope of the present invention depending on the purpose and application. Rib 3, boss 2, base wall 1 shape, dimensions,
The material and the like are appropriately selected according to the application.

[0014]

As described above, in the rib structure of the molded product according to the present invention, the thickness of the base wall of the molded product is not increased and the mechanical strength is maintained, and the rib and boss sink measures are taken. Therefore, it exerts an excellent effect on quality improvement.

[Brief description of drawings]

FIG. 1 is a perspective view of a rib structure of a molded product of Example 1.

FIG. 2 is a perspective view of a rib structure of a molded product of Example 2.

FIG. 3 is a perspective view of a rib structure of a molded product of Example 3.

FIG. 4 is a front view of a rib structure of a molded product of Example 3.

5 is a perspective view of a rib structure of a molded product of Example 4. FIG.

FIG. 6 is a front view of a rib structure of a conventional molded product.

FIG. 7 is a front view of a rib structure of a conventional molded product.

FIG. 8 is a front view of a rib structure of a conventional molded product.

[Explanation of symbols]

 1 Mother Wall 2 Boss 3 Rib 31 End 32 Long Side

Claims (3)

[Claims] 1. A rib formed on a mother wall of a molded product, wherein the rib is formed by intersecting ribs, and a meat sushi is provided around the intersection of the rib roots, and only the end of the rib root is the mother wall. A rib structure of a molded product, characterized in that the ribs are joined together. 2. A plurality of ribs are provided on a side wall of the boss, the ribs support the boss so that the bottom surface of the boss is separated from the mother wall, and only the end portion of the rib root is the mother wall. The rib structure of the combined molded product. 3. The rib of a molded article according to claim 1, wherein a long side direction of a coupling cross section of an end portion of a root of the rib coupled with the mother wall is made to coincide with a flow direction of the resin material during molding. Construction.