JPH0688289B2 - Multicolor mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold used for injection molding, and more particularly to a multicolor molding mold used for multicolor molding of two or more colors.

(Prior Art) Currently, products made by injection-molding plastic resins are widely used, and various molding methods have been devised. One of the typical ones is a magnetic tape cassette used for audio and video, etc., but this magnetic tape cassette usually has a magnetic tape wound inside a case body formed by upper and lower cassette halves. It is a structure in which a pair of rotated hubs are rotatably incorporated and held. The upper and lower cassette halves are generally made by injection molding a plastic material such as ABS resin, but a transparent or semi-transparent window is provided so that the winding state of the magnetic tape can be visually confirmed from the outside. There is. In addition, even if the entire case body is made of a light transmissive material, a window portion is often provided. In this case, the window portion has better light transmissivity than other portions to ensure the original function. It is provided in a desired shape for the purpose of achieving it, or in particular, designability is required in recent years, and a high design effect is obtained.

Conventionally, the above window portion is also attached to the main body of a window member different from the case main body by an adhesive agent or ultrasonic welding, but in this case, the window member must be manufactured and adhered. Further, when the case body is made of a light-transmissive material, there are some drawbacks such as the adhesive portion being visible and the appearance being unfavorable, which lowers the commercial value. Therefore,
As a manufacturing method that does not require adhesion of the window member, a manufacturing method by two-color molding is often adopted in recent years.

However, in the upper and lower cassette halves manufactured by two-color molding, the adhesive force between the joint surfaces of the two types of resins depends on the heat and injection pressure of the resin that is injected later. There was a strength problem. In particular, in the case of a magnetic tape cassette using a resin having a small case body and a different type of incompatible resin, which is a target of the present invention, a very important problem that affects the product quality and the cassette life. Is. Therefore, in order to increase the area of the joint surface, a structure is proposed in which the joint surface is stepped to increase the area, but such a structure is not sufficient to solve the strength problem. there were. In view of this, in Japanese Utility Model Laid-Open No. 60-60083, a convex portion is formed on one resin (the previously molded resin) at the middle portion of the joint surface of the window portion of the case body in the case thickness direction, and the other portion is formed. A magnetic tape cassette is disclosed in which a resin (a resin that is injected later) corresponds to the convex portion in a concave shape so that the two resins are engaged with each other due to unevenness.

However, in the case of Japanese Utility Model Laid-Open No. 60-60083, a slide core that slides in the thickness direction of the case body is used when forming a convex portion on the side opposite to the window member, which is the boundary portion of the window portion in the mold. Since the case day is formed by forming a concave portion in the horizontal direction, when the slide core is moved, the concave portion of the slide core and the convex portion formed of the injection resin are forcibly displaced from each other. Moreover, the convex shape of the molding resin cannot be so large. That is, when the uneven shape is increased in order to increase the bonding force, there is a defect that the formed convex portion is distorted or deformed due to the movement of the slide core.

(Object of the invention) In view of the above problems, the present invention can increase the joining force of the joining surfaces of resins with different injection timings and can prevent the joining surfaces from being distorted or deformed when multi-color molding is performed with a plastic resin. It is an object of the present invention to provide a multicolor molding die capable of forming a good joining surface that does not occur.

(Structure of the Invention) An object of the present invention is to inject a resin into a cavity having an initial shape in which at least a slide core is inserted,
In a multicolor molding die configured to inject a resin into a new cavity formed by moving the slide core to manufacture a molded product, the slide core is arranged in a sliding direction of the slide core. A recess forming member movable in a substantially orthogonal direction is built in, and the recess forming member has a tip portion protruding from the outer wall of the slide core, and the end portion is urged by an elastic member in the protrusion direction and the slide core is formed. This can be achieved by a multi-color molding die characterized in that it can be housed inside.

An embodiment of a two-color molding die for a magnetic tape cassette to which the present invention is applied will be described below.

First, FIG. 1 shows a magnetic tape cassette manufactured using the mold according to the present invention. This magnetic tape cassette 10
Conventionally, it has been generally used for audio and the like, and as in the conventional case, a pair of reel shaft insertion holes 12 into which the hub 4 around which the magnetic tape 5 is wound are loosely fitted are provided in the upper and lower cassette halves 3a and 3b. Further, a central opening 13 for inserting the recording / reproducing head is provided on the front surface of the case body 2. Further, the foreheads 14 and 14 arranged at the left and right symmetrical positions of the central opening 13, and the opening 1 arranged at the left and right symmetrical positions with respect to the central opening 13 on the outside of the small openings 14 and 14.
5,15, capstan insertion holes 16,16 and positioning holes 17,17
Are provided respectively. The upper and lower cassette halves 3a and 3b forming the case body 2 have two windows 11a and 11b, respectively.

In the magnetic tape cassette 10, the cassette body 2 other than the windows 11a and 11b is made of, for example, an opaque plastic resin, and the magnetic tape 5 inside the cassette is visually observed at the window portions 11a and 11b made of transparent resin. This is a structure that can be confirmed, and the windows 11a and 11b are molded by a two-color molding die described later.

Next, the manufacturing process of the case body 2 will be described with reference to FIGS. 2, 3, and 4. 2 and 3
1 is a sectional view of a cassette half molding die in a portion corresponding to a vertical section taken along line BB of the magnetic tape cassette 10 shown in FIG. 1, and FIG. 4 is a main part showing a structure of a slide core. FIG.

This mold has a structure that can be divided into a fixed mold 20 and a movable mold 21 corresponding to the fixed mold 20. The movable mold 21 is provided with two slide cores 40a and 40b. The slide cores 40a, 40b are configured to be movable in the thickness direction of the case body 2 by, for example, an air cylinder (not shown) installed below the movable mold 21.

As shown in FIG. 4, each of the slide cores 40a and 40b has a recess forming member 44 at the tip thereof. The recess forming member
Reference numeral 44 denotes a structure having a splayed portion 46 inside the core and a tapered tip end portion 47 protruding from the core outer wall 42, and is loaded so as to sandwich the compression spring 45 in a storage space 43 splayed inward. .
Therefore, each recess forming member 44 is pressed by the compression spring 45 in the direction in which the tip 47 projects from the core outer wall 42 (the direction opposite to the arrow B direction).

The magnetic tape cassette molded by the mold of the present invention
As for 10, the parts other than the windows 11a and 11b are first manufactured.

Initially, as shown in FIG. 2, the slide cores 40a and 40b are placed in the portions corresponding to the cavities 33 of the secondary molded product corresponding to the windows 11a and 11b, respectively, and the submarine gate is set.
Molten resin is injected from 32 to form a primary molded product 34 other than the windows 11a and 11b. At this time, since the recess molding member 44 of the slide cores 40a, 40b is projected from the core outer wall 42, the tip end portion 47 is formed by the primary molding 34.
It's getting inside.

After that, the slide cores 40a and 40b have their upper end surfaces
A new cavity 33 is formed by moving 41 in the thickness direction of the case body (direction of arrow A) to a position where it coincides with the inner wall of the case. When the slide cores 40a and 40b are moved, the recess forming member 44 is pressed by the compression spring 45, which is not so strong, and the tip 47 has a tapered surface, so that the tip 47 has almost no resistance.
Can be recessed into the core along the portion that becomes the recess 35.

Therefore, the large concave portion 35 can be formed on the end surface (bonding surface to the window portion) of the primary molded product 34. Then, resin is injected into the cavity 33 from the direct gate 23 to mold the window portions 11a and 11b.

Then, the fixed mold 20 and the movable mold 21 can be released from each other to take out a molded product (cassette half).

In the cassette half molded in this way, the resin of the window portions 11a and 11b enters the concave portion 35 to form a convex portion.Therefore, in addition to heat and injection pressure at the time of molding, engagement of the concave and convex portions As a result, the joining force is increased, and for example, it is possible to provide sufficient strength to withstand even when an external force in the thickness direction of the case acts.

Even if the windows 11a and 11b and the primary molded article 34 (portions other than the windows) are incompatible resins, the windows 11
Sufficient strength against external force can be obtained without separation at the boundary line between a and 11b and the primary molded product 34. Moreover, according to the molding die of the present invention, the recess having a large depth can be obtained.
Even if the recess forming member 44 is largely projected to form 35, the movement of the recess forming member 44 due to the movement of the slide cores 40a, 40b gives a force for damaging the primary molded product 34. It can be easily enlarged without.

It should be noted that the recess forming member 44 can be incorporated by making the tip portions of the slide cores 40a, 40b into a structure that can be divided by, for example, the vertical center line 50.

In the above-described embodiment, the recess forming members 44 are configured so as to face in mutually opposite directions, but the present invention is not limited to this, and they may be provided separately one by one, and the number is larger. Of course, the effect of the recess 35 can be increased. Further, the shape of the tip portion 47 is, of course,
It goes without saying that the overall shape of the recess forming member 44 can be changed in various ways.

Further, in the above-described embodiment, the recess forming member 44 has a pin-shaped configuration, but by having another plate-shaped configuration, the recess 35 is formed at the boundary between the windows 11a and 11b.
Can be formed widely.

In the above embodiment, the two-color molding was described,
The present invention can naturally be applied to multicolor molding of two or more colors.

(Effects of the Invention) As described above, in the multicolor molding die of the present invention, the slide core has a built-in recess forming member that is movable in a direction substantially orthogonal to the sliding direction of the slide core. Since the recess forming member has a tip portion protruding from the outer wall of the slide core, and the tip portion is biased in the protrusion direction by an elastic member so that it can be housed in the slide core, for example In the cassette half molded by the color molding die, the resin of the window part formed by the post-injection resin enters the concave part of the resin formed earlier to form the convex part, so both resins are molded during molding. In addition to the heat and the injection pressure, the joining force is increased by the engagement of the unevenness, and it is possible to provide the strength that can sufficiently withstand the external force in the thickness direction of the case. .

According to the present invention, even if the resins injected back and forth are incompatible resins, sufficient strength against external force can be obtained without separation at the boundary line between the two resins, and Even if the recess forming member is largely projected so as to form a recess having a large depth of the resin injected earlier, it can be retracted with a small force and it is possible to avoid giving a force that damages the vicinity of the recess. The concave-convex engagement can be configured to be larger than in the conventional case.

[Brief description of drawings]

FIG. 1 is a perspective view of a magnetic tape cassette molded by using the multicolor molding die of the present invention, and FIGS. 2 and 3 are cross-sectional views of an essential part of one embodiment of the multicolor molding die of the present invention. FIG. 4 is an enlarged schematic sectional view of an essential part of the slide core shown in FIGS. 2 and 3. 10 …… Magnetic tape cassette, 2 …… Case body, 3a …… Upper cassette half, 3b …… Lower cassette half, 11a, 11b …… Window part, 20 …… Fixed mold, 21 …… Movable mold, 21a ...... Upper surface of movable mold, 23 ...... Direct gate, 31, 33 …… Cavity, 34 …… Primary molded product, 35 …… Recess, 40a, 40b …… Slide core, 40a …… Mold recess, 41… … Sliding core upper end surface, 42 …… Core outer wall, 43 …… Storing space, 44 …… Recess forming member, 45 …… Compression spring, 46 …… Brim part, 47 …… Tip part, 50 …… Division line, PL …… Parting line.

Claims (1)

[Claims] 1. A molded product is manufactured by injecting a resin into a cavity of an initial shape in which at least a slide core is inserted, and then injecting a resin into a new cavity formed by moving the slide core. In the multi-color molding die configured as described above, the slide core has a built-in recess forming member that is movable in a direction substantially orthogonal to the sliding direction of the slide core, and the recess forming member is formed from an outer wall of the slide core. A multi-color molding die, which has a projecting tip portion, is elastically biased in the projecting direction by the elastic member, and can be housed in the slide core.