JPH02134223A - Die for multi-color molding - Google Patents

Abstract

PURPOSE:To form good junction surfaces by providing in a recessed part forming member a front end which projects out from an outer wall of a slide core, and is urged by an elastic member in a projecting direction thereof to be accommodatable within the slide core. CONSTITUTION:Slide cores 40a, 40b are provided with a forming member 44 at the front ends thereof which forms a recessed part. The recessed part forming member 44 has a spreading part 46 inside a core and an end part 47 which is tapered and projects from an outer wall 42 of the core. A compression spring 45 is installed and held in an accommodating space 43 inside the core. Therefore, each recessed part forming member 44 is pressed by the compression spring 45 in such a direction that the end part 47 is projected from the outer wall 42. The end part 47 of the recessed part forming member 44 of the slide cores 40a, 40b enters deep into a primary molding 34. Subsequently, the slide cores 40a, 40b are moved in a thicknesswise direction of a case body until an upper surface 41 of the cores 40a, 40b meets an inner wall of the case. Thus, a new cavity 33 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a mold used for injection molding, and particularly to a multicolor mold used for multicolor molding more than two-color molding.

(Prior Art) Currently, products made by injection molding of plastic resin are widely used, and various improvements have been made to the molding methods. One of the most representative of these is the magnetic tape cassette used for audio and video, but in a magnetic tape cassette, the magnetic tape is usually wound inside a case body formed by an upper and lower cassette half. It has a built-in structure that rotatably holds a pair of rotated hubs. These upper and lower cassette halves are generally made by injection molding of plastic materials such as ABS resin, but they are provided with transparent or translucent windows so that the winding state of the magnetic tape can be visually confirmed from the outside. There is. In addition, even when the entire case body is made of a light-transmitting material, a window is often provided, and in this case the window has better light transmission than other parts to ensure its original function. In particular, in recent years, design has been required, and they are provided in a desired shape for the purpose of achieving a high design effect.

Conventionally, the above-mentioned window has been attached to a window member separate from the case body using adhesive or ultrasonic welding, but in this case, manufacturing of the window member and bonding process are required. Furthermore, when the case body is made of a light-transmitting material, the bonded area may be visible, resulting in an unfavorable appearance and a reduction in commercial value. Therefore,
In recent years, as a manufacturing method that does not require adhesion of the window member, a manufacturing method using two-color molding is often adopted.

However, in upper and lower cassette halves manufactured by two-color molding, the adhesive force between the joint surfaces of the two types of resin relies on the heat and injection pressure of the resin that will be injected later. There was a serious problem. In particular, in magnetic tape cassettes, which are the object of the present invention and have thin case bodies and are made of different types of incompatible resins, there are extremely important problems that affect not only product quality but also the life of the cassette. It is. For this reason, in order to increase the area of the bonding surface, a configuration has been proposed in which the bonding surface is made step-shaped to increase the area, but such a structure is insufficient to solve the above-mentioned strength problem. there were. Therefore,
In Japanese Utility Model Application Publication No. 60-60083, a convex portion is formed in one resin (the resin molded first) at the middle part in the case thickness direction of the joint surface of the window in the case body, and a convex part is formed in the other resin (the resin molded first). A magnetic tape cassette is disclosed in which the resin (resin to be injected later) corresponds concavely to the convex portion, so that the two resins engage with each other in a concave and convex manner.

However, in the case of the above-mentioned Japanese Utility Model Application Publication No. 60-60083, when forming the convex part on the opposite member side, which is the boundary part of the window part, in the mold, the slide core that slides in the thickness direction of the case body is In order to form a horizontally recessed part, when moving the slide core, the recessed part of the slide core and the convex part formed of injection resin are forcibly shifted. In addition, the convex shape formed by molded resin cannot be made very large. That is, when the uneven shape is made larger in order to increase the bonding force, there is a drawback that the formed protrusions are distorted or deformed due to the movement of the slide core.

(Object of the Invention) In view of the above-mentioned problems, the present invention has been developed to increase the bonding force of the bonding surfaces of resins that are injected at different times when performing multicolor molding with plastic resins, and to prevent distortion and deformation of the bonding surfaces. The object of the present invention is to provide a multicolor molding die that can form a good joint surface that does not occur.

(Structure of the Invention) This object of the present invention is to inject resin into a cavity having an initial shape in which at least a slide core is inserted, and then
In a multicolor mold configured to manufacture a molded product by injecting resin into a new cavity formed by moving the slide core, the slide core moves in the 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 distal end protruding from the outer wall of the slide core, and the distal end is biased in the protruding direction by an elastic member, and This can be achieved by using a multi-color mold that can be stored inside the mold.

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

First, FIG. 1 shows a magnetic tape cassette manufactured using a mold according to the present invention. This magnetic tape cassette 10 is conventionally used for audio equipment, etc., and as in the conventional case, a pair of reel shaft insertion holes 12 into which a hub 4 around which a magnetic tape 5 is wound is loosely fitted so as to rotate are formed in the upper and lower reel shaft insertion holes 12. The central opening 13 is provided in the cassette halves 3a+3b, and the front surface of the case body 2 is provided with a central opening 13 into which a recording/reproducing head is inserted. Further, a small opening 14.14 arranged at a left-right symmetrical position of the central opening 13;
．． 14, an opening 15.15 arranged symmetrically with respect to the central opening 13, a capstan insertion hole 16.16 and a positioning hole 17.17, respectively. The upper and lower cassette halves 3a and 3b constituting the case body 2 each have two windows 1ta,
11b.

The magnetic tape cassette 10 has the window 11a111b.
The cassette body 2 other than the above is made of, for example, opaque plastic resin, and the window portion 11 is made of transparent resin.
The magnetic tape 5 inside the cassette can be visually confirmed at points a and 11b, and the windows 11a and 11b are molded using a two-color mold to be described later.

Next, the manufacturing process of the case body 2 will be explained based on FIGS. 2, 3, and 4. In addition, Figures 2 and 3
The figure is a cross-sectional view of the cassette half mold at a portion corresponding to the vertical cross section along the line B-B of the magnetic tape cassette 10 shown in FIG. 1, and FIG. 4 is a main part showing the structure of the 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. Each of the slide cores 40a and 40b is 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, the slide cores 40a, 40b are provided with a recess forming member 44 at the tip. The recess forming member 44 has a core inwardly widening portion 46 and a tapered tip portion 47 protruding from the core outer wall 42, and is configured to support a compression spring 45 in the storage space 43 extending inward. is loaded. Therefore, each of the recess forming members 44 is pressed by the compression spring 45 in a direction in which the tip portion 47 protrudes from the core outer wall 42 (in the direction opposite to the direction of arrow B).

In the magnetic tape cassette 10 molded by the mold of the present invention, the portions other than the window portions 11a+11b are manufactured first.

Initially, as shown in FIG. 2, the slide cores 40a and 40b were positioned in the portions corresponding to the cavities 33 of the secondary molded product corresponding to the windows 11a and 11b, and the molten resin was poured from the submarine gate 32. is injected to form a primary molded product 34 other than the window portions 11a and 11b. At this time, since the concave molded members 44 of the slide cores 40a and 40b protrude from the core outer wall 42, the tip portions 47 enter into the next molded product 34.

Thereafter, the slide cores 4Qa, 40b are moved in the case body thickness direction (arrow A direction) to a position where their upper end surfaces 41 coincide with the inner wall of the case.
A new cavity 33 is formed. When the slide cores 40a and 4Qb move, the concave molded member 44 is pressed by the compression spring 45, which is not very strong, and the tip 47 has a tapered surface, so the tip moves almost without resistance. The portion 47 can be retracted into the core along the portion that becomes the recess 35 .

Therefore, the large recess 35 can be formed on the end surface (joint surface with the window) of the next molded product 34.

Then, resin is injected into the cavity 33 from the direct gate 23 to form the windows 11a and ilb.

Thereafter, the fixed mold 20 and the movable mold 21 can be released and the molded product (cassette half) can be taken out.

In the cassette half molded in this manner, the resin of the window portions 11a and llb enters the recess 35 and forms a convex portion. The bonding force is strong, so even when an external force is applied in the direction of the case thickness, for example,
It can be strong enough to endure.

Even if the window portions 11a, llb and the second molded product 34 (portions other than the window portions) are made of incompatible resins, the boundary line between the window portions 11a, llb and the second molded product 34 It is possible to obtain sufficient strength against external forces without separation. Moreover, according to the molding die of the present invention, the recess forming member 4 is configured to form the recess 35 having a large depth.
Even if the slide cores 40a, 4 are made to protrude greatly, the slide cores 40a, 4
Due to the movement of the recess forming member 44 due to the movement of the recess 0b, it is possible to easily increase the size of the next molded product 34 without applying any force that would damage it.

Incidentally, the recess forming member 44 can be incorporated by providing a structure in which the tip portions of the slide cores 40a, 40b can be divided, for example, at the vertical center line 50.

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

Furthermore, in the embodiment, the recess forming member 44
Although the pin-shaped configuration is adopted, by adopting the square plate-shaped configuration, the recessed portion 35 can be formed broadly at the boundary portion of the window portion 11a111b.

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

(Effects of the Invention) As described above, in the multicolor molding mold of the present invention, the slide core incorporates a recess forming member that is movable in a direction substantially perpendicular to the sliding direction of the slide core, and For example, the recess forming member has a distal end protruding from the outer wall of the slide core, and is configured such that the distal end is urged in the protruding direction by an elastic member and can be stored within the slide core. In the cassette half molded using a color molding mold, the resin of the window part formed with the post-injected resin enters the concave part of the previously formed resin and forms the convex part, so both resins are mixed during molding. In addition to the heat and injection pressure, the bonding force is strengthened by the engagement of the projections and depressions, and even when an external force is applied in the direction of the thickness of the case, it is strong enough to withstand.

According to the present invention, even if the resins that are injected one after the other are resins that are not compatible with each other, there is no separation at the boundary line between the two resins, and sufficient strength against external forces can be obtained. Even if the recess forming member is made to protrude greatly to form a deep recess for the previously injected resin, it can be retracted with a small force, thereby avoiding applying force that would damage the vicinity of the recess. This allows for a larger concave-convex engagement than in the past.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a magnetic tape cassette molded using the multicolor molding die of the present invention, and FIGS. 2 and 3 are cross sections of essential parts of an embodiment of the multicolor molding die of the present invention. FIG. 4 is an enlarged schematic cross-section of the main part of the slide core shown in FIGS. 2 and 3. 10... Magnetic tape cassette, 2... Case body, - Upper cassette half, - Lower cassette half, 11b... Window, fixed mold, 21 Top surface of movable mold, - Direct gate, 33... Cavity, - -Next molded product, 35... recess, 40b... slide core, mold recess, - upper end surface of slide core, - outer wall of core, 43... storage space, - recess forming member, - compression spring, 46... collar Part, ・Tip, 50...Parting line, Parting line.・Movable mold, a b 31. 34 ・ 40a, 0a 42 ・ 44 ・ 45 ・ 47 ・ P, L

Claims (1)

[Claims] The molded article is manufactured by injecting resin into a cavity having an initial shape into which at least a slide core is inserted, and then injecting the resin into a new cavity formed by moving the slide core. In the multi-color mold, the slide core has a built-in recess forming member that is movable in a direction substantially perpendicular to the sliding direction of the slide core, and the recess forming member has a distal end protruding from the outer wall of the slide core. What is claimed is: 1. A multicolor molding die, characterized in that the tip portion is biased in the projecting direction by an elastic member and is configured to be housed within the slide core.