JP2002137265A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply mold a molded article having a notch formed to one peripheral wall extending in the rapping direction thereof and having a bead edge becoming an undercut on the side end surface of the notch. SOLUTION: The injection mold 1 is constituted of a fixed mold 2, a movable mold 3 freely movable with respect to the fixed mold 2 and the core 4 provided to the fixed mold 2 so as to be freely movable in the moving direction of the movable mold 3. The mold surface corresponding to the notch 11a is formed by half by the fixed mold 2 and the core 4. The core 4 is urged so as to move from the fixed mold 2 through an elastomer 5 and locked by the ejector pin 6 cooperating with the movement of the movable mold 3. Therefore, when the mold is opened by injection molding, the molded article 10 is ejected by the ejector pin 6 and the core 4 is pushed up in a cooperative state. Thereafter, a resin is shrunk and the undercut accompanied by the die-cut gradient of the bead edge on the side end surface of the notch 11a with the recessed part 4a of the core 4 is eliminated to take out the molded article 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die, and more particularly to an injection molding die suitable for molding a molded product having a bead on a side end face of a notch formed in a peripheral wall.

[0002]

2. Description of the Related Art An injection molding die includes a fixed die and a movable die capable of clamping and opening the fixed die, and a cavity is formed by the clamped fixed die and movable die. Is formed. Then, a molded product corresponding to the shape of the cavity is molded by injecting and filling the molten resin into the cavity and solidifying it.

As shown in FIGS. 7 and 8,
Shallow box-shaped molded article 1 having notch 11a in one peripheral wall 11
When molding 0, a ball with a substantially semicircular cross section is usually formed on the upper end surface of the peripheral wall 11 so as not to hurt even if touched by hand. In this case, there is no problem if the pair of opposed side end faces 111 of the notch 11a is flat, but when a bead is also formed on the side end face 111 of the notch 11a,
Due to the relationship of the die-cutting gradient formed on the movable side die of 1 to 3 degrees, the above-mentioned bead of the side end face 111 is undercut when the die is opened.

In order to mold the molded article 10 having such an undercut, a slide core is usually provided on a fixed mold, and a cavity (recess) corresponding to the ball of the side end surface 111 is provided in the slide core. Is formed.

[0005]

However, when a slide core is used, an angular cam or the like for operating the slide core is required, so that not only the number of parts is increased, the structure becomes complicated, but also the die cost is increased. Was expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a molded product having a bead which becomes an undercut in connection with a die-cutting gradient by utilizing shrinkage of a resin without using a slide core. And provides an inexpensive injection mold that can be easily molded.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to an injection molding method for forming a molded product having a cutout formed in at least one peripheral wall extending in the direction of a die-cutting gradient and a bead formed on a side end surface of the cutout. The injection mold is provided on a fixed mold, a movable mold movable with respect to the fixed mold, and a fixed mold movable in the moving direction of the movable mold. The fixed mold has a projection corresponding to a half shape in the thickness direction of the notch so that a mold surface corresponding to the notch is formed by the fixed mold and the nest. At the same time, the nest is formed with a concave portion corresponding to a half shape in the thickness direction of the bead of the side end surface of the cutout portion at the side edge on the joining surface side with the protruding portion.
It is urged to move from the fixed mold through the elastic body, and is locked by an ejector pin that moves in conjunction with the movement of the movable mold. When the ejector pin moves, the nest is moved along with the molded product from the fixed mold through the elastic body, and then the mold is released from the bead on the side end face of the notch and the recess of the nest due to the contraction of the resin. And the undercut accompanying the above is eliminated, and the bead on the side end face of the cutout portion is separated from the concave portion of the nest.

According to the present invention, after the molten resin is injected and filled into the cavity formed by the fixed mold, the nest, and the movable mold and solidified, and then the movable mold is opened, the movable mold is opened. The ejector pin moves in conjunction with the movement, the molded product moves from the fixed mold, and the nest moves in the same direction from the fixed mold by following the urging force of the elastic body. Therefore, the relative positional relationship between the nest and the molded product does not change, and the undercut accompanying the die-cutting gradient between the bead on the side end surface of the cutout portion of the molded product and the concave portion of the nest is maintained as it is. Thereafter, the resin shrinks and separates from the nest. Here, the molded product can be taken out without interfering with the concave portion of the nest because the shrinkage amount of the resin is larger than the undercut amount of the bead due to the drafting gradient.

When the movable mold is clamped, the ejector pin moves in conjunction with the movement of the movable mold, and the ejector pin pushes down the nest against the urging force of the elastic body, thereby forming a molded product. A cavity corresponding to the shape is formed. At this time, the mold surface corresponding to the cutout having a bead on the side end surface is formed by the protrusion of the fixed mold and the recess of the insert.

As a result, the fixed-side mold and the insert are formed on the mold surface in which the cutout portion is divided into two in the thickness direction, and the insert is movably provided on the fixed-side mold, and the elastic body for urging the insert is provided. With a simple configuration in which only an ejector pin for locking the insert is provided, it is possible to form an injection molding die of a molded product in which the bead on the side end surface of the cutout portion is undercut due to the die cutting gradient. Therefore, an inexpensive injection mold having a small number of parts can be obtained.

The present invention also provides an injection molding die for forming a molded product having a notch formed on at least one peripheral wall extending in the direction of the die-cutting gradient and a bead formed on a side end surface of the notch. Then, this injection mold has a fixed side mold,
The movable mold is movable with respect to the fixed mold, and a nest is provided on the fixed mold so as to be movable in the moving direction of the movable mold. In the fixed mold, a protrusion corresponding to half the shape of the notch in the thickness direction is formed so that a mold surface corresponding to the notch is formed. A concave portion corresponding to half the thickness of the side edge of the cutout in the thickness direction of the bead is formed at the side edge on the side of the surface, and the nest is formed in conjunction with the opening of the movable mold during injection molding. Is moved from the fixed mold with
Due to the shrinkage of the resin, the undercut due to the mold cutting gradient between the bead on the side end face of the notch and the recess of the nest is eliminated, and the bead on the side edge of the notch is detached from the recess of the nest. Is what you do.

According to the present invention, after the molten resin is injected and filled into the cavity formed by the fixed mold, the nest, and the movable mold and solidified, and then the movable mold is opened, the movable mold is opened. The ejector mechanism operates in conjunction with the movement to eject the molded product, and at the same time, the nest moves in the same direction in conjunction with the ejector mechanism. Therefore, the relative positional relationship between the nest and the molded product does not change, and the undercut accompanying the die-cutting gradient between the bead on the side end surface of the cutout portion of the molded product and the concave portion of the nest is maintained as it is. After that, the resin shrinks,
Remove from the nest. Here, the molded product can be taken out without interfering with the concave portion of the nest because the shrinkage amount of the resin is larger than the undercut amount of the bead due to the drafting gradient.

When the movable mold is clamped, the ejector mechanism moves in conjunction with the movement of the movable mold,
As the nest moves in conjunction, a cavity corresponding to the shape of the molded article is formed. At this time, the mold surface corresponding to the cutout having a bead on the side end surface is formed by the protrusion of the fixed mold and the recess of the insert.

As a result, the fixed mold and the insert are formed on the mold surface having the cutout portion divided into two in the thickness direction, and the insert is provided on the fixed mold so as to be movable in conjunction with the ejector mechanism. With such a configuration, it is possible to form an injection molding die of a molded product in which the bead on the side end surface of the cutout portion is undercut along with the drafting gradient. Therefore, an inexpensive injection mold having a small number of parts can be obtained.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the injection mold 1 of the present invention.

In the injection mold 1 of this embodiment, a notch 11a is formed in at least one peripheral wall 11, and
This is used when molding a molded product 10 having a bead on the bottom end face of the notch 11a and a pair of side end faces 111 facing each other. Movable mold 3 that moves to and closes mold.
And a nest 4 movably provided in the up and down direction with respect to the fixed mold 2. The fixed mold 2, the movable mold 3 and the nest 4 are formed by clamping the movable mold 3. During this time, a cavity having a shape corresponding to the molded product 10 is formed.

Here, as shown in FIG. 2, the fixed side mold 2 has a die cutting slope formed on each outer peripheral surface thereof and corresponds to a bead on the upper end surface of each peripheral wall 11 of the molded article 10. Recess 2
a is formed. Also, the notch 11a of the molded product 10
On one outer peripheral surface of the fixed side mold 2 corresponding to the one peripheral wall 11 in which is formed a protruding portion 21 corresponding to a half shape of the cutout portion 11a in the thickness direction. For this reason, the protrusion 21
Is formed with a recess 21a having a substantially quarter-circular cross section corresponding to half of the bead on each end face of the notch 11a. Further, a fitting notch 2b having a width corresponding to the width of the notch 11a is formed in the fixed mold 2, and a nest 4 described later can be slidably fitted therein.

The insert 4 has a width substantially equivalent to the width of the notch 11a and is formed in a rectangular parallelepiped shape which can be fitted into the fitting notch 2a of the fixed die 2. Corresponding to the projected portion 21 of the fixed mold 2, a recess 4 a having a substantially quarter-circular cross section corresponding to half of the bead on each end face of the notch 11 a.
Are formed. Therefore, when the insert 4 is fitted into the fitting notch 2 a of the fixed mold 2 and the inner surface thereof is joined to the protrusion 21, a ball is attached to each end face by the protrusion 21 of the fixed mold 2 and the recess 4 a of the insert 4. A mold surface corresponding to the notch 11a having an edge is formed.

Further, between the fixed mold 2 and the insert 4,
An elastic body 5 such as a coil spring is provided, and the nest 4 is urged to move upward with respect to the fixed mold 2 by the urging force of the elastic body 5. On the other hand, the nest 4 is provided with an ejector pin 6 having a hook-like cross section that is interlocked with the movement of the movable mold 3, and stops the nest 4 from moving upward by the urging force of the elastic body 5. are doing.

Next, the operation of the thus-configured injection mold 1 will be described.

When the movable mold 3 is clamped with respect to the fixed mold 2, as shown in FIG. 1, the ejector pin 6 is lowered in conjunction with the mold clamp of the movable mold 3, and the insert 4 is made of an elastic material. 5 is pressed down by the ejector pin 6 against the urging force of the ejector pin 5. Here, the projecting portion 21 of the fixed mold 2 and the insert 4 cooperate to form a mold surface corresponding to the notch 11a, and a cavity corresponding to the shape of the molded article 10 between the movable mold 3 and the mold surface. Is formed. That is, the recess 21a of the protrusion 21 of the fixed mold 2 and the recess 4a of the insert 4 form a recess corresponding to the bead on each end face of the notch 11a. In this clamped state, the upper surface of the insert 4 is
At a position corresponding to the bottom end surface of the notch 11a.

In this state, the molten resin is injected and filled into the cavity, and after the molten resin is solidified, when the movable mold 3 is opened, the ejector pins 6 move in conjunction with the opening of the movable mold 3. To start. When the ejector pin 6 moves, the molded product 10 protrudes from the fixed side mold 2, and the elastic body 5 pushes up the nest 4 following the movement of the ejector pin 6. Therefore, the relative position change between the molded product 10 and the insert 4 does not occur, and the molded product 10 and the insert 4 ascend with respect to the fixed mold 2 (see FIG. 3). At this time, the side end surface 11 of the notch 11a of the molded product 10
The bead 1 is separated from the recess 21 a of the protrusion 21 of the fixed mold 2.

When the molded article 11 is separated from the fixed mold 2,
Since the resin is released from the filled state, the resin starts to contract and separates from the nest 4 (see FIG. 4).

Here, when the amount of resin shrinkage is larger than the amount of undercut of the bead on the side end face 111 of the notch 11a due to the draft, the molded product 10 is inserted into the recess 4 of the insert 4.
It can be taken out without causing interference with a, that is, without undercut (see FIG. 5).

Specifically, the length is 600 mm × width 600 mm
When molding a molded article 10 having a cutout 11a having a height of 40 mm, a thickness of 2.3 mm, and a width of 80 mm x a height of 20 mm with an ABS resin, the shrinkage of the ABS resin is 5/1000.
Therefore, the shrinkage amount of the resin is 600 mm × 5/1.
000 × １ ／ = 1.5 mm. On the other hand, the undercut amount of the notch portion 11a when the mold release gradient is 3 degrees is t
an3 ° × 20 mm = 1.04 mm. Therefore, the amount of shrinkage of the resin of 1.5 mm corresponds to the amount of undercut of 1.
The molded product 10 is larger than 04 mm and the recess 4a of the nest 4
Can be taken out without causing interference.

In the above-described embodiment, the nest 4 is pressed and urged by the elastic body 5 so that the nest 4 rises following the ejector pin 6 which rises in conjunction with the opening of the movable mold 3. However, as shown in FIG.
The nest 4 may be directly moved in conjunction with an ejector mechanism (not shown) without providing an elastic body or an ejector pin.

[0028]

As described above, according to the present invention, the fixed mold and the insert are formed on the mold surface having the cutout portion divided into two in the thickness direction, and the insert is movably provided on the fixed mold. Injection molding of a molded product with a simple configuration in which an elastic body for urging the nest and an ejector pin for locking the nest are provided, and the bead on the side end surface of the notch is undercut due to the drafting gradient. A mold can be formed. Therefore, an inexpensive injection mold having a small number of parts can be obtained.

Further, according to the present invention, the fixed mold and the insert are formed on the mold surface having the cutout portion divided into two in the thickness direction, and the insert is movable on the fixed mold in conjunction with the ejector mechanism. With such a simple configuration, it is possible to form an injection molding die of a molded product in which the bead on the side end surface of the cutout portion is undercut due to the cutting gradient. Therefore, an inexpensive injection mold having a small number of parts can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view partially showing an embodiment of an injection mold according to the present invention;

FIG. 2 is a perspective view showing a part of a relationship between a fixed side mold and a nest of the injection mold of FIG.

FIG. 3 is a cross-sectional view showing a state in which the injection mold of FIG.

FIG. 4 is a cross-sectional view showing a contracted state of a molded product molded by the injection molding die of FIG. 1, cut along a cutout portion of the molded product.

FIG. 5 is a cross-sectional view showing a state in which a molded product molded by the injection mold of FIG. 1 is taken out and cut by a cutout of the molded product.

FIG. 6 is a perspective view showing a molded product.

FIG. 7 is a front view, a bottom view, and a front view taken along line XX of the cutaway portion of the shaped article in FIG. 6;

FIG. 8 is a cross-sectional view showing another embodiment of the injection mold according to the present invention with a part thereof omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding die 2 Fixed-side mold 21 Projecting part 21a Concave part 3 Movable-side mold 4 Nesting 4a Concave part 5 Elastic body 6 Ejector pin 10 Molded product 11 Peripheral wall 11a Notch 111 Side end face

Claims (2)

[Claims] 1. An injection molding die for forming a molded product having a notch formed in at least one peripheral wall extending in a direction of a mold draft and a bead formed on a side end surface of the notch. The injection molding die is composed of a fixed mold, a movable mold movable with respect to the fixed mold, and a nest provided on the fixed mold movably in a moving direction of the movable mold. As the mold surface corresponding to the notch is formed by the fixed mold and the nest, the fixed mold has a protrusion corresponding to a half shape in the thickness direction of the notch, and the nest includes A concave portion corresponding to a half shape in the thickness direction of the bead on the side end surface of the cutout portion is formed at a side edge of the joining surface side with the protruding portion, and the nest is formed from a fixed side mold via an elastic body. Eject that is urged to move and is linked to the movement of the movable side mold When the ejector pin moves in conjunction with the opening of the movable side mold during injection molding, the nest is moved along with the molded product from the fixed side mold via an elastic body, and then The feature is that the undercut due to the die-cutting gradient between the bead on the side end face of the notch and the recess of the nest due to shrinkage of the resin is eliminated, and the bead on the side end face of the notch is separated from the recess of the nest. Injection mold. 2. An injection molding die for forming a molded product having a notch formed in at least one peripheral wall extending in a direction of a drafting slope and a bead formed on a side end surface of the notch. The injection mold includes a fixed mold, a movable mold movable with respect to the fixed mold, and a nest that is provided on the fixed mold movably in the moving direction of the movable mold, and interlocks with the ejector mechanism. The fixed die is formed with a protrusion corresponding to a half shape in the thickness direction of the notch so that a mold surface corresponding to the notch is formed by the fixed mold and the insert. In the nest, a concave portion corresponding to half the shape in the thickness direction of the bead on the side end surface of the cutout is formed at the side edge on the side of the joint surface with the protruding portion. The nest moves with the molded product from the fixed mold in conjunction with the mold opening. After that, due to the contraction of the resin, the undercut due to the cutting edge between the bead on the side end face of the notch and the recess of the nest is eliminated, and the bead on the side edge of the notch is detached from the recess of the nest. An injection molding die characterized in that: