JP2534876B2 - Manufacturing method of tape cartridge - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a tape cartridge having a transparent window for visually recognizing the amount of tape winding, and more specifically, a main body case and a transparent window plate are two-color ejected. A method of integrally molding by molding.

[Conventional technology]

In a tape cartridge with a plastic body case and a transparent window plate, if the body case and the transparent window plate were separately molded and then joined together by ultrasonic welding or the like, the productivity would be significantly improved. I can't hope.
Therefore, recently, a method has been developed in which the main body case is primary-molded by the two-color injection molding method, and the transparent window plate is secondary-molded to be integrally molded. According to this two-color injection molding method, since the primary molding and the secondary molding are performed continuously, the productivity can be improved.

In adopting this two-color injection molding method, as shown in FIG. 4, the main body case 1 which is a primary molded product and the transparent window plate 2 which is a secondary molded product are integrally joined by simply abutting the thick cross-sections thereof. It is difficult to expect complete fusion just by doing so, and after a while, the butt joint between the main body case 1 and the transparent window plate 2 is subject to load from inside and outside the case and deformation due to environmental temperature change. The transparent window plate 2 may come off.

As means for solving such a problem, the present applicant has previously proposed the following two methods. One of them is the window opening 5 of the main body case 1 as shown in FIG. 5 in order to increase the butt joint strength between the main body case and the transparent window plate as shown in Japanese Utility Model Laid-Open No. 61-156074. One of the inner periphery and the transparent window plate is provided with a convex portion 10 having a rectangular cross section, and the other is provided with a concave portion 11 for receiving and fitting the convex portion 10, and by these concave and convex fitting, the main body case 1 and the transparent case are transparent. The window plate 2 is prevented from being displaced relative to the inside / outside direction (thickness direction) of the case. However, the concavo-convex portions 11 and 10 disclosed therein are of a large shape that cannot be forcibly removed, and therefore the inversion method is adopted as the two-color molding method. With this inversion method, the number of molds taken is 1/2 of the mold size.
It is not economical.

Others, as disclosed in JP-A-61-213118, form fine irregularities on the inner peripheral surface of the window opening of the main body case, which is a primary molded product, and melt it during secondary molding of a transparent window plate. This is a method of completely melting the thick cross-sections of the main body case and the transparent window plate by melting the convex portion group with the heat of the resin.

According to this, the core back method can be adopted, which has an advantage over the reversal method in terms of production efficiency and cost, but a compatible molding material for the main body case and the transparent window plate should be used. It is necessary to select the material, and the degree of freedom in selecting the material is extremely limited. That is, since it is required that the main body case has excellent rigidity and heat resistance as the shell of the tape cartridge, it is preferable to use, for example, a filler composite plastic in which a filler of calcium carbonate is combined with polypropylene. As a material for the window plate, a material that is compatible with and transparent to the window plate, that is, polypropylene alone is used. However, polypropylene is not so transparent, and it is difficult to see the tape winding amount and winding status. On the contrary, if the transparent window plate is formed of a material having excellent transparency, the molding material of the main body case that is compatible with it cannot sufficiently improve the mechanical and thermal properties. There is the disadvantage of having to select compatible resins.

Therefore, the present invention has been made in order to solve such various problems at once, and in the method of two-color injection molding the main body case and the transparent window plate, the core back method, which is superior in production efficiency and cost, to the reversal method. The purpose is to enable the adoption of.

Further, the object of the present invention is to enable resin molding of different materials without being specified as compatible molding materials for the main body case and the transparent window plate, and to freely select materials for the main body case and the transparent window plate. There is a point to try.

A further object of the present invention is to increase the butt joint strength between the main body case and the transparent window plate.

[Means for solving problems]

In the present invention, the main body case 1 is made by the two-color injection molding method.
Next, when the transparent window plate 2 is secondarily molded, the main body case 1 and the transparent window plate 2 are molded with different resin materials. In this case, a resin having excellent mechanical and thermal properties is selected as the molding material for the main body case 1, and a resin having excellent transparency is selected as the molding material for the transparent window plate 2.

Further, according to the present invention, if the main body case 1 and the transparent window plate 2 are formed of different materials, the fusion and integration of the two cannot be achieved. Therefore, in order to compensate for this, the main body case 1 and the transparent window plate 2 are strengthened. When the two are butt-joined to each other, the convex portion 8 is provided on one side.
Is provided and is integrally molded in such a manner that the other recess 9 is fitted therein.

Further, although the present invention adopts the core back method,
At this time, the uneven portion is set to a size that can be forcibly removed so that the uneven portion does not hinder the operation of the core back.

[Action]

According to the above configuration, even when the main body case 1 and the transparent window plate 2 are formed by different materials by the core back method, the transparent window plate 2 is firmly and integrally joined to the main body case 1 by concave and convex fitting. Will be obtained.

〔The invention's effect〕

According to the present invention, since the main body case 1 and the transparent window plate 2 are two-color injection-molded with different resins, the main body case 1 can be molded with a material having excellent rigidity and heat resistance, and the transparent window plate 2 is transparent. It is possible to obtain a material having excellent quality characteristics for both the main body case 1 and the transparent window plate 2 by molding with a material having excellent properties.

Further, in the present invention, the convex portion 8 or the concave portion 9 is formed on the whole or a part of the inner peripheral surface of the window opening 5 of the main body case 1 and is opposed to the inner periphery of the window opening 5 of the transparent window plate 2. Since the entire circumference or part of the edge to be fitted is fitted,
Even if the transparent window plate 2 is molded with a resin of a material different from that of the main body case 1, it is possible to reliably prevent the transparent window plate 2 from coming off the main body case 1 due to a drop impact, thermal deformation, or the like. Furthermore, since the uneven portion is set to a size that allows forcible removal,
The core back method is possible, the production efficiency is higher than that of the inversion method, and the mass production can be performed at low cost.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

In FIGS. 1 and 3, 1 is a main body case that is a primary molded product, 2 is a transparent window plate that is a secondary molded product, and both are integrally joined and molded by the two-color injection molding method as follows. .

First, as shown in FIG. 2A, the upper and lower molds 3 and 4 are set for the primary molding of the main body case 1. A core 6 for forming a window opening 5 in the body case 1 is set in the lower mold 4. A concave portion 7 is provided on the side surface of the tip of the core 6. Thus, the primary molding material is injected into the cavities in the upper and lower molds 3 and 4 to perform cooling molding. Since the concave portion 7 of the dicing core 6 faces the inner peripheral surface of the window opening 5 of the main body case 1, the primary molding resin during the primary molding enters the concave portion 7 and the inner circumference of the window opening 5 The convex portion 8 is formed on the surface. After the primary molding, when the core 6 retracts, resistance is generated by the convex portion 8, but the core 8 is forcibly punched out and retracted to a predetermined position as shown in FIG. 2 (b).

Then, as shown in FIG. 2 (b), a transparent secondary molding resin is injected from the secondary molding gate G into the cavity of the secondary molding formed between the main body case 1 as the primary molding and the retreat core 6. By this secondary molding, the transparent window plate 2 is integrally molded in the window opening 5 of the main body case 1. At this time, the concave portion 9 on the transparent window plate 2 side is fitted to the convex portion 8 on the main body case 1 side. It will be molded to fit.

As the primary molding material, filler composite plastic is used to improve the mechanical and thermal properties of the body case 1 itself. More specifically, it is a composite of polypropylene and a filler of calcium carbonate.
On the other hand, PS resin (polystyrene) or AS resin (acrylonitrile-styrene copolymer) having excellent transparency is used as the secondary molding material. Other than that, the secondary molding material may be, for example, P resin or PMMA resin.

[Another embodiment]

In the above embodiment, the convex portion 8 is formed on the inner peripheral surface side of the window opening 5 of the main body case 1, and the concave portion 9 is formed on the transparent window plate 2 side so as to be fitted thereto.
However, on the contrary, it is also possible to form a concave portion 9 on the inner peripheral surface side of the window opening 5 of the main body case 1 and a convex portion 8 fitted to it on the transparent window plate 2 side. it can.

Further, instead of partially providing the convex portion 8 or the concave portion 9 on the inner peripheral surface of the window opening portion 5 of the main body case 1, it may be formed over the entire circumference thereof.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention,
1 is an enlarged sectional view taken along the line AA in FIG. 3, FIG. 2 (a) is a die sectional view showing a primary molding state, and FIG. 2 (b).
Is a sectional view of the die showing a secondary molding state, and FIG. 3 is a plan view of the entire tape cartridge. FIG. 4 is a cross-sectional view of essential parts showing a conventional tape cartridge. FIG. 5 is a cross-sectional view of a main part showing a tape cartridge of another conventional example. 1 ... main body case, 2 ... transparent window plate, 5 ... window opening, 6 ... core, 8 ... convex, 9 ... recess.

Claims (1)

(57) [Claims] 1. A step of primary molding a main body case 1 having a window opening 5, and a transparent window plate 2 made of a transparent resin different from that of the main body case 1 in the window opening 5 of the main body case 1. The core forming method includes a secondary molding step, and a convex portion 8 or a concave portion 9 of a size that allows forcible removal is formed on the entire circumference or a part of the inner peripheral surface of the window opening 5 of the main body case 1 during the primary molding. Is formed, and the edge of the transparent window plate 2 is formed by secondary molding so as to fit into the convex portion 8 or the concave portion 9, and a method of manufacturing a tape cartridge.