JP2000301581A - Mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for injection molding which is of a simple structure and need not use a slide core or the like. SOLUTION: This mold for injection molding is composed of a fixed half 1 and a movable half 3 and has a cavity 4 formed between both halves 1, 2 during closing the halves 1, 2. A projecting part 22 for molding an undercut part 32 is formed protruding on the movable part 22, and a movable insert 24 which juts out into the cavity 4 by the restoring force of a spring 26 is provided near the projecting part 22 of the movable half 2. Further, the wall part 31 of a molding 3 is peeled off a mold face 22 by the jutting-out action of the movable insert 24 during opening the mold and the undercut part 32 of the molding 3 is separated from the projecting part 22 for molding the undercut part 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal mold for injection molding, and more particularly, to a metal mold suitable for use in molding a molded article having an undercut portion.

[0002]

2. Description of the Related Art Conventionally, as a molded article provided with an undercut portion, for example, as shown in FIG.
When the injection molding is performed, the through hole (c) of the side wall (b) becomes an undercut portion. To form the through hole (c), as shown in FIG. One edge (d) of the through hole (c) of the molded product (a) to be detached
Must have a sharp edge shape.

[0003] Alternatively, as shown in FIG.
When the molded product (a) is deformed by utilizing the elasticity of the side wall (b) of the above, and the molded product (a) is released from the movable mold in the direction of the arrow a by so-called forced removal, the through hole (c) of the molded product (a) One edge of (d)
Is reduced, but the angle θ of the edge (d) is up to 4
It is about 5 degrees.

As an injection mold used for molding a molded article having an undercut portion, for example, a slide core is used as disclosed in Japanese Patent Application Laid-Open No. 2-107419. There is known a core in which a core pin for projecting an undercut portion of a molded product is protruded.

[0005] As such an injection molding die, for example, an inclined pin is inserted into an inclined hole provided in the slide core to move the slide core when the mold is opened. The slide core is moved by sliding the inclined pin in the inclined hole, and the core pin of the slide core is detached from the undercut portion of the molded product.

[0006]

However, the conventional mold for injection molding using a slide core has many drawbacks such as a large number of parts, a complicated structure, and many failures.

[0007] The present invention has been made in view of the above-mentioned problems in the conventional injection mold, and an object thereof is to solve the problems in the conventional injection mold. An object of the present invention is to provide an injection molding die which has a simple structure and does not require the use of a slide core or the like.

[0008]

In order to achieve the above object, an injection mold of the present invention is provided with a fixed mold and a movable mold, and a cavity is formed between both molds when the mold is closed. The movable mold has an undercut portion forming projection projecting from the movable mold, and a movable nest that projects into the cavity by the restoring force of the spring when the mold is opened near the projection of the movable mold. When the mold is opened, the movable nest projects so that the wall of the molded product is peeled off from the mold surface, and the undercut portion of the molded product is detached from the convex portion for molding the undercut portion. Things.

[Operation] In the injection molding die of the present invention, the movable die is provided with a projection for forming an undercut portion.
A movable nest that projects into the cavity by the restoring force of the spring when the mold is opened is provided near the convex part of the movable mold. Since the cut part is detached from the undercut part forming convex part, a sharp edge shape is not formed at the peripheral part of the undercut part, and the structure of the mold is simple, There are few failures and there is no need to use a slide core or the like.

[0010]

FIG. 1 is a sectional view showing an example of an injection mold according to the present invention when the mold is closed. FIG. 2 is a sectional view of a main part of the injection mold according to the present invention shown in FIG. FIG. 3 is a cross-sectional view showing a state where the movable mold of the injection molding die of the present invention shown in FIG. 1 has moved slightly, and FIG. 4 is a state where the movable die of the injection molding die of the present invention shown in FIG. 1 has further moved. FIG. 5 is a cross-sectional view showing a state where the movable mold of the injection mold of the present invention shown in FIG. 1 is further moved. FIG. 6 is a sectional view showing a movable mold of the injection mold of the present invention shown in FIG. It is sectional drawing which shows the state which moved further. In these figures, reference numeral 1 denotes a fixed mold of the injection molding die of the present invention;
Denotes a mold surface provided on the fixed mold 1, 2 denotes a movable mold, and 21 denotes a mold surface provided on the movable mold 2.

When the fixed mold 1 and the movable mold 2 are closed, a gap between the mold surface 11 of the fixed mold 1 and the mold surface 21 of the movable mold 2 corresponds to the shape of the container-like molded product 3 to be molded. The cavity 4 having the following shape is formed.

A projection 22 for forming an undercut portion protrudes from a mold surface 21 of the movable mold 2 so that a through hole 32 serving as an undercut portion can be formed in the side wall 31 of the container-shaped molded product 3 by the projection 22. It has become.

A recess 23 is provided in the vicinity of the convex portion 22 of the movable mold 2, and a base of a movable insert 24 is inserted into the recess 23 so as to be able to advance and retreat. A recess 12 is provided at a position corresponding to the movable nest 24 at the end of the mold surface 11 of the fixed mold 1,
When the mold is closed as shown in FIG.
4 is to be inserted.

A spring housing hole 25 is formed in the bottom of the recess 23 of the movable mold 2, and a coil compression spring 26 is housed in the spring housing hole 25.
4 is pushed out in the direction of arrow b, and at the same time, as shown in FIGS. 4 and 5, the shoulder 241 of the movable nest 24 projects into the cavity.

Numeral 27 denotes a stopper mounted near the concave portion 23 of the movable mold 2. When the movable nest 24 is pushed out by the restoring force of the spring 26, the step 2 of the movable nest 24 is stopped.
42 contacts the stopper 27, and the movement of the movable insert 24 is stopped.

As shown in FIG. 2, the angle θ1 between the bottom surface of the concave portion 12 of the fixed die 1 and the distal end surface of the movable nest 24 with respect to the moving direction of the movable die 2 is 3 ° to 5 °, which is the minimum cutting angle. is necessary. Inclination angle θ of side wall 31 of molded product 3
When the angle 2 is less than the angle θ1, the surface of the molded product 3 may be scratched due to friction with the mold surface 11 of the fixed mold 1. Therefore, it is preferable that the inclination angle θ2 of the side wall portion 31 of the molded product 3 be about twice the angle θ1.

The angle θ3 of the inclined surface 243 of the distal end of the movable insert 24 with respect to the moving direction of the movable mold 2 is preferably about 15 to 25 degrees, similarly to the angle of the pressure receiving portion of a normal slide core. The length of the distal end surface of the movable insert 24 and the length of the slope 243 at the distal end of the movable insert 24 are determined by the thickness of the molded product 3, draft angle, and the like. It is preferable that the movable insert 24 prevents galling trouble by nitriding or quenching.

Since the injection mold of the present invention shown in FIGS. 1 to 6 has the structure described above, as shown in FIG.
When the mold is closed, the mold surface 11 of the fixed mold 1 and the mold surface 21 of the movable mold 2
And the cavity 4 is formed, and the mold surface 21 of the movable mold 2 is formed.
The tip of the protruding portion 22 protruding from the mold surface 11 is abutted against the mold surface 11 of the fixed mold 1.

In this state, the molten resin is injected into the cavity 4, the molten resin is cooled and solidified, and the container 3 is formed.

Next, the movable mold 2 starts moving. At the start of the movement of the movable mold 2, as shown in FIG. 3, the distal end surface of the movable nest 24 slides on the bottom surface of the recess 12 of the fixed mold 1,
The movable nest 24 is pushed by the restoring force of the spring 26, but moves slightly in the direction of the arrow b.

As shown in FIG. 4, when the movable mold 2 moves and the slope 243 of the movable nest 24 reaches the slope 121 at the bottom end of the recess 12 of the fixed mold 1, the movable nest 24 moves.
Is slightly moved in the direction of the arrow b by the restoring force of the spring 26, the shoulder 241 of the movable insert 24 is protruded, the side wall 31 of the molded product 3 is slightly pushed out, and the side wall 31 is slightly moved from the mold surface 21 of the movable mold 2. Peel off.

As shown in FIG. 5, when the movable mold 2 is further moved, the movable nest 24 is further moved in the direction of arrow b by the restoring force of the spring 26, and the shoulder 24 of the movable nest 24 is moved.
1 is further pushed out, and the side wall 31 of the molded product 3 is further pushed out, and the side wall 31 is slightly peeled off from the mold surface 21 of the movable mold 2.

As shown in FIG. 6, when the movable mold 2 is sufficiently moved from the fixed mold 1, the through hole 32 of the molded product 3 is separated from the convex portion 22 of the movable mold 2 by the movement of the movable insert 24. , The molded product 3 as shown by the arrow c.
Completely released from

In this way, the molding cycle ends,
For the start of the next molding cycle, as shown in FIG.
The fixed mold 1 and the movable mold 2 are closed, and the movable nest 24 is housed in the recess 23 against the restoring force of the spring 26.

Although the embodiment of the present invention has been described with reference to the drawings, the specific configuration of the present invention is not limited to the illustrated embodiment, and the design change within a scope not departing from the gist of the present invention. Are included in the present invention.

For example, instead of applying to a so-called vertical injection mold in which the movable mold is moved vertically from the fixed mold as in the illustrated embodiment, the movable mold is moved horizontally from the fixed mold. It may be applied to a so-called horizontal injection molding die.

[0027]

According to the injection molding die of the present invention, no sharp edge is formed at the periphery of the undercut portion, the structure of the die is simple, there are few failures, and the slide is small. Since it is not necessary to use a core or the like, it is possible to reduce the manufacturing cost of the mold.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a state of an example of an injection mold according to the present invention when the mold is closed.

FIG. 2 is a cross-sectional view showing a main part of the injection mold of the present invention shown in FIG. 1 in a slightly enlarged manner.

FIG. 3 is a sectional view showing a state in which the movable mold of the injection mold of the present invention shown in FIGS. 1 and 2 is slightly opened.

FIG. 4 is a cross-sectional view showing a state in which the movable mold of the injection mold of the present invention shown in FIGS.

FIG. 5 is a sectional view showing a state in which the movable mold of the injection molding mold of the present invention shown in FIGS. 1 to 4 is further opened.

FIG. 6 is a cross-sectional view showing a state in which the movable mold of the injection mold of the present invention shown in FIGS. 1 to 5 is completely opened.

FIG. 7 is a perspective view showing a box-shaped product.

FIG. 8 is a sectional view taken along line VIII-VIII in FIG. 7;

FIG. 9 is a cross-sectional view showing another example of the periphery of the through hole of the box-shaped product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed type 11 Mold surface 12 Concavity 121 Slope 2 Movable mold 21 Mold surface 22 Convex part 23 Concave 24 Movable nest 241 Movable nest shoulder 242 Movable nest step 243 Movable nest slope 25 Spring storage hole 26 Spring 27 Stopper 3 Molded product 31 Side wall of molded product 32 Through hole 4 Cavity

Claims (1)

[Claims] 1. An injection mold having a fixed mold and a movable mold, wherein a cavity is formed between both molds when the mold is closed. A movable nest is provided near the convex portion of the movable mold and protrudes into the cavity by the restoring force of the spring when the mold is opened. When the movable nest is projected when the mold is opened, the wall of the molded product is peeled off from the mold surface. An injection molding die, wherein an undercut portion of a molded product is detached from an undercut portion forming projection.