JP2002120262A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold which makes it unnecessary to enlarge the size thereof on injection molding of a resin product having an undercut part and can minimize the restriction on a product design, and the like. SOLUTION: Recess shapes 8 and 9 being along each other are provided in the respective runner forming portions of a film 6 and the mold 2 wherein the film is set. While a space K is present among the bead shape 8, the mold 2 and the covering film 6 in a runner 5 in a state wherein molds 1 and 2 are opened, the covering film 6 is held between and flattened by upper and lower mold parting lines of the runner 5 when the molds 1 and 2 are closed. Therefore the covering film 6 is stretched and the space K becomes small. A molten resin M is prevented from flowing in between the covering film 6 and the mold 2 and the film can be molded integrally on a predetermined surface. By a means of changing the moving speed of extruding rods which is provided for the product extruding rods 8, an insert die for forming the undercut part of the resin product is rotated to process the undercut part, the connecting part of one extruding rod and the insert die being used as a fulcrum and the connecting part of the other extruding rod and the die being used as a point of action.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold for molding a molded article having an undercut.

[0002]

2. Description of the Related Art When a resin product having an undercut portion is formed by injection molding, when the mold is opened after completion of molding, the product is taken out so that the undercut portion of the product does not interfere with the undercut portion of the product. Is required. As means for achieving this object, a tilted nest type and an unforced type have conventionally been adopted.

With reference to FIG. 9, a description will be given of the processing of the undercut portion by the inclined nesting type. FIG. 9 shows a mold for injection-molding a product 21 having an undercut portion using a cavity mold 22, a core mold 23, and a nest 24. As a mold structure, the nest 24 is held by an inclined rod 26 that can freely slide on a guide unit 27 fixed on an ejector plate 25. The undercut portion is processed by moving the ejector plate 25 so that the nest 24 slides in a direction perpendicular to the mold opening relative to the product 21.

[0004] Referring to FIG. 10, the processing of the undercut portion by the forcible removal type will be described. FIG. 10 shows a product 21 having an undercut portion using a cavity mold 22, a core mold 23, a movable core 28, and a slide block 29.
Shows a mold for injection molding. As the mold structure, the slide block 29 and the movable core 28 can slide in the y direction in FIG. When the slide block moves in the y direction by the cylinder and moves a predetermined amount L, the movable core and the cylinder move synchronously by the action of the block 31. After opening the mold, the undercut portion releases the surface forming the undercut portion of the product 21 by moving the slide block,
Thereafter, the product 21 is processed by being forcibly deformed by moving the movable core.

[0005]

The inclined nest type described above has a structure in which the sliding amount of the nest is determined by the inclination angle between the ejector plate and the rod. Therefore, when the amount of undercut is large, the inclination angle of the rod becomes large. If the inclination angle of the rod is large, the rod may not be smoothly slid so that the rod may be damaged in some cases. In particular, if the overall length of the mold in the mold opening direction is reduced to reduce the weight of the mold,
Because the stroke of the ejector plate becomes smaller,
The inclination angle of the rod increases, and the possibility of rod breakage increases. Also, the nested guide unit forming the undercut portion must be set at a position deviating from immediately below the nest when projected from the mold opening direction, and the ejector plate becomes large accordingly. In this case, the layout on the ejector plate becomes complicated due to the problem such as the increase in the mold weight and the relationship with other units.
Interference with other units is assumed. On the other hand, the nest slides relative to the product on the back side of the product,
In order to achieve this type of undercut processing, there is a condition that there should be no interference such as a rib on the back surface of the product in the sliding direction of the nest. This will be specifically described with reference to FIG. The nest slides from the two-dot dashed line to the position of the solid line. Since interference with nesting occurs, in the former case, restrictions on the product design are imposed, and in the latter case, the product performance may not be satisfied.

Further, in the case of the forcible removal type, since the undercut is processed by forcibly deforming the product, it is necessary to keep the amount of deformation within an elastic range in order to prevent permanent deformation from remaining. It is difficult to mold a product having a large size.

[0007]

SUMMARY OF THE INVENTION The present invention has been developed to effectively solve the above-mentioned conventional problems.
The described invention comprises a core mold and a cavity mold, and has an ejector plate movably provided in a direction relatively approaching and separating from the core mold, and after molding in order to take out a product from the mold, the core is formed. The mold and the cavity mold are opened, and then the ejector plate moves in a direction approaching the core mold and is placed on the core mold side in an injection molding mold for a resin product having an undercut portion for extruding the product. A nest with an undercut,
One end is connected to the ejector plate, the other end is connected to the back surface of the nest, and the connecting portion of the nest is rotatable.A plurality of extruding rods are provided on at least one of the extruding rods. Moving speed changing means for changing a speed of moving toward and away from the core mold, wherein at least one of the pushing rod and the nest is connected by the moving speed changing means provided on the pushing rod at the time of product extrusion. The injection molding die is characterized in that the nest rotates and the undercut portion of the resin product is processed with the portion as a fulcrum and the connecting portion between the other extrusion rod and the nest as an operation point. According to the first aspect of the present invention, it is possible to reduce the size of the mold and to avoid a failure such as a broken rod. On the other hand, it also has the effect of reducing restrictions on product design and contributing to ensuring product performance.

According to a second aspect of the present invention, a projection provided on at least one of the push rods as the moving speed changing means and a back surface of the core mold are provided, and the ejector plate is provided with respect to the core mold. 2. The injection molding die according to claim 1, further comprising a stopper that comes into contact with said projection when approached. According to the second aspect of the present invention, the product insert rod provided with the moving speed changing means at the time of product extrusion stops relative to the product extrusion rod not provided with the means, whereby the nest rotates. The same effect as described above can be obtained.

According to a third aspect of the present invention, there is provided a cam which engages with at least one of the pushing rods as the moving speed changing means, and a back surface of a mold, wherein the ejector plate moves closer to the core mold. 2. The injection molding die according to claim 1, further comprising an abutment pin that comes into contact with said cam. According to the third aspect of the present invention, the product insert rod provided with the moving speed changing means at the time of product extrusion has a longer product extrusion stroke relative to the product extrusion rod not provided with the means, so that the nest rotates. The same effect as the first aspect can be obtained.

According to a fourth aspect of the present invention, the moving speed changing means has an elastic body, and after the undercut portion is processed, when the ejector plate separates from the core mold, the moving speed is changed when the product is extruded. The injection molding die according to any one of claims 1 to 3, wherein the changed extrusion rod returns to its original state when the die is closed due to the elastic force of the elastic body. According to the fourth aspect of the present invention, after the molding is completed by the elastic body, it is possible to produce an effect that the resin product returns to the original state when the mold is closed, that is, returns to the same state as before molding and can continuously mold the resin product.

[0011]

1 to 3 show a first embodiment of the present invention.

FIG. 1 shows a part of a mold for molding a resin product having an undercut portion in a mold opening direction, and shows a mold closed state. This mold forms a cavity mold 2 that forms the front side of the resin product 1, a core mold 3 that forms the back side of the product 1, and an undercut 1a of the product. It is configured. The nest 4 comprises an ejector plate 5 for extruding the product and a plurality of rods 6,8.
Are connected via a pin 7a.

One end of the rod 6 is connected to the insert 4 and the pin 7a, and the other end is fixed to the ejector plate 5. One end of the rod 8 is connected to the nest 4 and the pin 7b.

A connecting portion between the nest 4 and the rod 6 (I in FIG. 1)
-I section) is shown in FIG. The nesting end of the rod 6 is 2
It has two plane portions P1. A slit 4 b is provided on the rod side of the nest 4, and the end of the rod 6 having the plane portion P <b> 1 is inserted. Hole 4c provided in nest 4
And the hole 6a provided in the plane portion P1 of the rod 6 communicate with each other,
They are connected by inserting the pin 7a. Rod 8
In the case of, the hole 4c provided in the flat portion P1 of the rod 8 is a circle, whereas the groove 4d provided in the nest is an elongated hole. Therefore, when the moving speed of the rod 6 becomes relatively faster than the moving speed of the rod 8, the pin 7b slides in the groove, and the nest 4 can be rotated.

The rod 8 is provided with a moving speed changing means which becomes different from the ejector plate 5 when the ejector plate 5 approaches the core mold 3 at a moving speed, and the means comprises a flange portion projecting so as to cover the outer periphery thereof. 10
The collar portion 3 comes into contact with a stopper 11 fixed to the back surface of the core mold 3 when the product is pushed out. The other end of the rod 8 is in contact with the ejector plate 5 in a state in which the mold 9 is in a closed state, and a spring 9 which is an elastic body applies a certain tension to the rod 8 and is fixed to the ejector plate 5 by a block 12.

The operation will be described with reference to FIGS. After the molding is completed, the mold is opened, that is, after the cavity mold 2 is separated from the product 1, the product 1 is extruded by the ejector plate 5. FIG. 2 shows this state. Ejector plate 5
Moves in a direction (direction A shown in FIG. 2) relatively approaching the core mold 3, the flange 10 provided on the rod 8 comes into contact with the stopper 11. As shown in FIG. 3, when the ejector plate 5 further moves, the rod 8 compresses the elastic body 9 so that the rod 8 does not push out the product 1, but the rod 6 keeps the ejector even after the rod 8 has finished moving. The product 1 is extruded with the movement of the plate 5.
At this time, the insert 4 rotates in the direction B shown in FIG. This operation enables the processing of the undercut portion 1a of the product 1. Specifically, as shown in FIG. 3, when the moving amount β in the portion 4a, which is the maximum amount of undercut after rotation of the nest 4, is larger than the amount of undercut α of the nest 4, the product 1 can be removed from the mold without being damaged. Can be taken out.

After the product is taken out, the ejector plate 5 moves in a direction away from the core mold 3. While the rod 6 moves synchronously, at the beginning of the movement, the rod 8 does not follow the movement of the ejector plate 5 due to the action of the elastic body 9, so that the nest 4 rotates in the opposite direction to B and the state shown in FIG. It is in the same state as. Thereafter, when the ejector plate 5 further moves, the nest 4 is housed in the core mold 3 and returns to the original state. When the cavity mold 2 is closed, the process proceeds to the next molding cycle, and the molding can be continuously performed. it can.

FIG. 5 shows a second embodiment. While the first embodiment relatively stops the movement of the rod 8 during the movement of the ejector plate 5 and rotates the nest 4, the second embodiment
In the above, the nest 4 is rotated by the rod 8 having a longer stroke amount with respect to the rod 6, and the undercut portion is processed.

The first embodiment described above with reference to the second embodiment will now be described.
The difference from the embodiment is mainly described. Note that the same reference numerals are given to portions having the same functions as the configuration, and redundant description will be omitted. The structure of the second embodiment is the same as that of the first embodiment.
Has two rods 6 and 8 and is common in that each rod is connected to the nest 4 via pins 7 a and 7 b, but the other end of the rod 8 is in contact with the cam unit 13. Is different. The cam unit is mounted on the side of the ejector plate 5 opposite to the product 1. The cam unit has a cam 14 and a pin 15, and the cam 14 rotates about the pin 15.

FIG. 6 is an enlarged view of the cam, and FIG. 7 is a view of the cam as viewed from a direction C in FIG. The distal end side of the cam 14 is formed in a forked shape by forming an engagement groove 14a opened on the distal end side, and is formed in an arc shape. In the engagement groove 14a of the cam 14, a flat plate-shaped portion 8q formed by forming a cut-shaped concave portion 8p on both sides of the rod 8 is engaged. That is, the cam 1
4 have concave portions 8p formed on both sides of the rod 8.
The cam 14 swings up and down around the pin 15 to move the rod 8 up and down.

When the ejector plate 5 is moving to push out the product 1 after the mold is opened, the rod 8, the cam 14 and the like are moved by the action of the spring 9, which is an elastic body, as shown in FIG.
The state shown in FIG. After moving by a predetermined amount, the end of the abutting pin 16 provided on the back surface of the core mold 3 abuts against the abutting surface of the cam 14, and the cam 14 swings about the pin 15, so that the rod 8 pushes the product. The ejecting speed is faster than the moving speed of the ejector plate 5. This is rod 6
On the other hand, the product pushing stroke of the rod 8 means that the nest 4 rotates around the pin 8 in the direction c in FIG. 5 to process the undercut portion.

After the product is taken out, when the ejector plate 5 moves, the rod 6 moves synchronously as in the first embodiment, but the cam separates from the abutment pin 16 so that the cam 14 is actuated by the action of the spring 9. As a result, the nest 4 rotates in the direction opposite to the direction c in FIG. 5 and is in a state similar to the state shown in FIG. The subsequent operation is the same as in the first embodiment.

[0023]

According to the first aspect of the present invention, unlike the conventional inclined nesting type, a nest having an undercut portion directly below the ejector plate can be set, so that the design layout becomes easy and the amount of undercut is large. Even in this case, since the ejector stroke is not increased, the size of the mold can be made compact, and since the nesting does not incline the pushing rod, the sliding of the rod is smooth and the rod can be prevented from being damaged.

Further, as described above, the nest slides from the position of the solid line to the position of the two-dot dashed line in the conventional inclined nesting type. If the ribs are present, they may interfere with the nesting. However, in the case of the present invention, the nesting locus can avoid beads or ribs as shown in FIG. The above constraint can be reduced, and in the latter case, product performance can be ensured.

On the other hand, in the case of the unremovable type, since the product is forcibly deformed and the undercut is processed, it is necessary to keep the shape within the elastic range in order to prevent permanent deformation. This has the effect that the product can be taken out of the mold without deformation.

According to the second aspect of the present invention, the product insert rod provided with the moving speed changing means at the time of product extrusion stops relatively to the product extrusion rod not provided with said means, so that the nest rotates. The same effect as the first aspect can be obtained.

According to the third aspect of the present invention, the product extruding rod provided with the moving speed changing means at the time of product extruding has a longer product extruding stroke relative to the product extruding rod not provided with the means. The nest rotates, and the same effect as the first aspect can be obtained.

According to the fourth aspect of the present invention, after the molding is completed by the elastic body, it is possible to produce an effect that when the mold is closed, the mold returns to the original state, that is, returns to the same state as before molding, and the resin product can be continuously molded. .

[Brief description of the drawings]

FIG. 1 is a view showing a state in which a mold is closed according to a first embodiment of the present invention.

FIG. 2 is a view showing a state in which an ejector plate moves and pushes a product according to the first embodiment of the present invention.

FIG. 3 is a view showing a state in which a nest having an undercut portion is rotated according to the first embodiment of the present invention;

FIG. 4 is an enlarged view of a connecting portion between a nest and a product pushing rod (a cross section taken along line II in FIG. 1).

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is an enlarged view of a cam unit.

FIG. 7 is a view of the cam unit as viewed from a direction c in FIG. 6;

FIG. 8 is a view showing a rotation locus of a nest according to the present invention.

FIG. 9 is a view showing a mold structure of an inclined nesting type.

FIG. 10 is a diagram showing a mold structure of a forcible removal type.

FIG. 11 is a diagram showing a rotation locus of a nest in the inclined nest type.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Resin product, 2 ... Cavity type, 3 ... Core type, 4 ... Nesting, 5 ... Ejector plate, 6, 8 ... Product extrusion rod, 9 ... Elastic body

Claims (4)

[Claims] An ejector plate provided with a core mold and a cavity mold so as to be movable in a direction relatively approaching and separating from the core mold, and after molding to take out a product from the mold, The core mold and the cavity mold are opened, and then the ejector plate moves in a direction approaching the core mold and in a resin product injection molding mold having an undercut portion for extruding the product, placed on the core mold side, A nest formed with the undercut portion, a plurality of push rods having one end connected to the ejector plate, the other end connected to the back surface of the nest, and a connecting portion of the nest being rotatable; Moving speed changing means provided at at least one of them, for changing a speed of moving toward and away from the core type of the ejector plate. When the product is extruded, the moving speed changing means provided on the extruding rod causes the nesting with the connecting portion between at least one of the extruding rod and the nest as a fulcrum and the connecting portion between the other extruding rod and the nest as an operating point. Characterized by rotating and processing an undercut portion of the resin product. 2. The apparatus according to claim 2, wherein the moving speed changing means is at least
A projection provided on one of the push rods; and a stopper provided on the back side of the core mold and abutting on the projection when the ejector plate moves closer to the core mold. The injection mold according to claim 1, wherein 3. A cam that is engaged with at least one of the push rods as the moving speed changing means, and is provided on a back surface of a mold, and the cam is provided when the ejector plate approaches and moves with respect to the core mold. 2. The injection mold according to claim 1, further comprising an abutment pin that abuts. 4. An extruding rod whose speed is changed at the time of extruding a product when the ejector plate separates from the core mold after processing of an undercut portion, wherein the moving speed changing means has an elastic body. 4. The injection mold according to claim 1, wherein the mold returns to its original state when the mold is closed by the elastic force of the elastic body.