JPH087978B2 - Tape cartridge case molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for molding a case having a transparent window for observing the tape winding amount in a tape cartridge.

[Conventional technology]

As a case of this type of tape cartridge, for example, as shown in FIG. 8, a case body 1 having a window hole 2 is primarily formed by a two-color molding method, and a transparent window plate 3 is formed in the window hole 2 of the case body 1. There is a method of secondary molding.

9 (a) and 9 (b) show the general structure of the two-color molding die, FIG. 9 (a) shows the state of primary molding, and FIG. 9 (b) shows the state of secondary molding. It shows the state. In FIG. 9 (a), the slide core 7 for forming the window hole is advanced in the direction of the arrow A to abut against the upper mold 5 for molding the case body, and in this state, it is formed between the upper and lower molds 5 and 6. The primary molding material (opaque resin) is injected into the primary molding space 8 to cool and mold the case body 1 having the window hole 2. The gas generated in the primary molding space 8 at this time is discharged from a gas vent slit 9 provided on the upper surface of the lower mold 6 at the joint surface portion with the slide core 7.

Next, as shown in FIG. 9 (b), the slide core 7 is retracted to form a secondary molding space 10 between itself and the upper mold 5, and the secondary molding material (transparent resin) is placed in this space 10. The transparent window plate 3 is integrally secondary molded in the window hole 2 of the case body 1 by injecting from the secondary molding gate 11. In this secondary molding, the retracted position of the slide core 7 is set slightly above the height of the lower mold 6 or at the same height as that of the lower mold 6, so that the gas vent slit 9 is a primary molded product. It is blocked by the main body 1 and an exhaust gas defect occurs during secondary molding. Therefore, the slide core 7 and the lower mold 6 are easily damaged by gas corrosion, and the case body 1 and the transparent window plate 3 are also easily damaged.
Burrs etc. occur on the inner surface of the tape, causing problems such as damage to the tape.

As a countermeasure against exhaust gas defects at the time of such secondary molding, the applicant of the present invention has previously proposed what is shown in FIGS. 10 (a) and 10 (b) (Japanese Patent Laid-Open No. 62-219380). Where,
As shown in FIG. 10 (a), when the convex portion 20 is provided on the upper end of the lower mold 6 and the slide core 7 is retracted during the secondary molding, as shown in FIG. 10 (b), degassing is performed. 2 slits 9
It communicates with the next molding space 10. Therefore,
According to this, it is possible to prevent the occurrence of defective exhaust gas during the secondary molding.

[Problems to be Solved by the Invention]

According to what the inventors of the present invention later found out, the lower die 6
The convex portion 20 on the side is easily damaged, and the presence of the convex portion 20 reduces the joint area between the window hole 2 of the case body 1 and the transparent window plate 3, and after assembly, an external force is applied to the case body 1 or the transparent window plate 3. It has been found that the joint surface is easily disengaged when is added.

Therefore, the present invention is a case molding method in which the case main body and the transparent window plate are integrally molded by the two-color injection molding method of the core back method as described above. Another object of the present invention is to eliminate the problem of detachment of the joint surface between the window hole of the case body and the transparent window plate.

[Means for solving the problem]

In order to achieve the above object, in the tape cartridge case molding method of the present invention, upper and lower molds 5 and 6 for molding the case main body and a slide core 7 for molding a window hole in the lower mold 6 are provided.
Then, after the case body 1 having the window hole 2 is formed by the primary molding, the slide core 7 is retracted to form the transparent window plate 3 in the window hole 2 of the case body 1 by the secondary molding. By setting the retracted position of the core 7 to a position lower than the lower mold 6, the secondary molding space 10 is provided at the upper surface of the lower mold 6 at the joint surface with the slide core 7 for the primary molding. It communicates with the gas vent slit 9.

Further, in the present invention, the entire circumference or a part of the peripheral surface of the upper end portion 7a facing the inner peripheral surface of the window hole of the slide core 7 is formed in a cross-sectional shape having a plurality of steps in the thickness direction of the window plate. By retracting the slide core 7 during the secondary molding, the secondary molding space 10 communicates with the degassing slit 9 for the primary molding provided in the joint surface portion of the lower mold 6 with the slide core 7. It was done.

[Action]

In this case, the gas vent passage can be secured even during the secondary molding, and the gas in the secondary molding space 10 can be surely discharged.

Further, even when designing the lower die 6 and the slide core 7 for degassing, it is not necessary to provide the convex portion 20 which is easily damaged as in the conventional one described above, and therefore, the simple shape can be manufactured.

Further, it is possible to secure a joint area between the window hole 2 of the case body 1 and the transparent window plate 3.

[First Embodiment] FIGS. 1 to 3 show a first embodiment of the present invention.

2 and 3, C is a case of the tape cartridge, which is a case body 1 having a wide window hole 2 and a drive shaft insertion hole 4 integrally formed in the window hole 2 of the case body 1.
And the transparent window plate 3 having the above-mentioned structure. Both of them are molded by the two-color injection molding method of the core back method as follows.

First, as shown in FIG. 1 (a), the upper and lower molds 5 and 6 for molding the case main body are set, and the slide core 7 for molding the window hole is set in the lower mold 6 to form the primary molding space 8. Form. A gas vent slit 9 is provided at a position corresponding to a final resin filling portion in the primary molding space 8 at a joint surface portion of the lower die 6 with the slide core 7. Thus, by ejecting the primary molding material into the primary molding space 8 to perform cooling molding, the case body 1 having the window hole 2 can be obtained. At that time, the gas in the primary molding space 8 is discharged from the gas vent slit 9.

After the primary molding, as shown in FIG. 1 (b), when the slide core 7 is retracted to a position further below the lower mold 6, the secondary molding space is formed between the slide core 7 and the case body 1 which is the primary molded product. Ten
Is formed, and the space 10 and the gas vent slit 9 communicate with each other. Thus, by injecting the transparent secondary molding resin from the secondary molding gate 11 provided in the upper mold 5 into the secondary molding space 10, the transparent resin is injected into the window hole 2 of the case body 1 as shown in FIG. The transparent window plate 3 covers the entire inner surface 3a of the case body 1
Is formed so as to be convex downward from the inner surface 1a, and the transparent window plate 3 is integrally joined to the entire inner peripheral surface of the window hole 2. At this time, the drive shaft insertion hole 4 is formed in the transparent window plate 3 by the cores 12 and 13 set in the upper mold 5 and the slide core 7. During the secondary molding, the secondary molding space 10 communicates with the gas vent slit 9, and the gas in the space 10 is surely discharged from the slit 9.

The secondary molding gate 11 is set at a substantially central position of the transparent window plate 3 as shown in FIG.

[Second Embodiment] FIGS. 4 (a) and (b) and FIG. 5 show a second embodiment of the present invention. In this embodiment, the upper end of the slide core 7
A step drop portion 14 is provided on a part of the circumferential surface of 7a, and the upper end portion 7a
A part of the peripheral surface is formed into a cross-sectional shape having two steps in the vertical direction in the thickness direction of the window plate. Even when the retracted position of the slide core 7 is set slightly above the lower mold 6 or at the same height as shown in FIG. 4 (b), the degassing passage 15 for the secondary molding is ensured. I decided to get it. The other mold structures are the same as those in the first embodiment.

Then, in the primary molding shown in FIG. 4 (a), the case book 1 having the window hole 2 is molded as in the first embodiment. However, a protrusion 16 (see FIG. 5) is formed on a part of the inner peripheral surface of the window hole 2 of the case body 1 (the final filling portion of the resin) by the step-down portion 14 of the upper end portion 7a of the slide core 7. The point is,
The shape is different from the shape of the window hole 2 obtained in the first embodiment.

In the secondary molding shown in FIG. 4 (b), the transparent window plate 3 has the inner surface 3 a inside the window hole 2 of the case body 1 and the inner surface of the case body 1.
Except that it is integrally molded so as to be slightly above or flush with 1a, and that a part of the transparent window plate 3 in the circumferential direction is joined along the protrusion 16 of the window hole 2. ，
This is similar to the case of the first embodiment.

In this embodiment, as shown in FIG. 4 (b), by keeping the clearance α of the gas vent passage 15 below the range where burr does not occur (usually about 15 to 20 μm for polystyrene etc.), the case main body 1 Also, it becomes possible to prevent a protrusion from being formed at the relevant portion of the transparent window plate 3.

[Third Embodiment] FIGS. 6A and 6B show a third embodiment of the present invention. This embodiment is similar to the second embodiment in that a step-down portion 14 is provided on a part of the peripheral surface of the upper end portion 7a of the slide core 7 in order to secure the gas vent passage 15 at the time of secondary molding. The difference from this is that the stepped-down portion 14 is formed in a larger shape so as to make the width of the gas vent passage wider than in the second embodiment.

[Other Examples]

In both the second embodiment and the third embodiment, as shown in FIG. 5, the gas vent passage 15 is set only at the location where the protrusion 16 corresponding to the final filling location of the molding resin is formed. As shown in FIG. 7, a gas vent passage 15 may be formed at a portion 1 around the entire circumference of the transparent window plate 3, which is more effective when only the gas vent surface is considered.

In addition, in the second and third embodiments, instead of forming the cross-sectional shape of a part or the entire circumference of the upper end portion 7a of the slide core 7 in a two-step upper and lower shape, a shape of a plurality of steps more than that It is also possible to form it.

However, the present invention is effective when the transparent window plate 3 is vast, but can be similarly applied to a small window plate.

It goes without saying that the invention can be applied not only to the case of the audio tape cartridge but also to other cases such as the case of the video tape cartridge.

〔The invention's effect〕

As described above, according to the present invention, during the secondary molding, the slide core 7 for molding the window hole is retracted to a position lower than the lower mold 6 having the gas vent slit 9 for primary molding. The secondary molding space 10 communicates with the gas vent slit 9. Therefore, for the degassing during the secondary molding, the design of the lower mold 6 and the slide core 7 can be made in a simple shape without providing the easily prone to damage 20 such as the above-mentioned conventional example when manufacturing the mold. It can be free from mold failures. In addition, since the joint area between the window hole 2 of the case body 1 and the transparent window plate 3 can be secured, it is advantageous to prevent the joint surface portion from coming off due to an external force.

Further, in the present invention, the entire circumference or a part of the peripheral surface of the upper end portion 7a facing the inner peripheral surface of the window hole of the slide core 7 is formed in a cross-sectional shape having a plurality of steps in the window plate thickness direction, When the slide core 7 is retracted during the secondary molding, the secondary molding space 10 is formed between the upper end portion 7a of the slide core 7 and the gas vent slit 9.
A gas vent passage 15 communicating with the above is formed. Therefore, the slide core 7 can be manufactured by machining the peripheral surface of the upper end portion 7a and the like, and a mold can be manufactured without failure, and the window hole 2 of the case body 1 and the transparent window plate 3 are joined together. Area can be secured. Even when the entire inner surface of the transparent window plate 3 cannot be made to be convex from the inner surface side of the case in the product design, the gas vent passage 15 can be secured during the secondary molding.

[Brief description of drawings]

1 (a) and (b) to FIG. 3 show a first embodiment of the present invention. FIGS. 1 (a) and (b) are sectional views of a molding die, and FIG. 2 is a tape. FIG. 3 is a plan view of the cartridge, and FIG. 3 is an enlarged sectional view taken along the line AA in FIG. FIGS. 4 (a) and (b) and FIG. 5 show a second embodiment of the present invention. FIGS. 4 (a) and (b) are sectional views of a molding die, and FIG. 5 is a tape. It is a top view of a cartridge. 6 (a) and 6 (b) are sectional views of a molding die showing a third embodiment of the present invention. FIG. 7 is a plan view of a tape cartridge showing still another embodiment of the present invention. FIGS. 8 and 9 (a) and (b) show a conventional example, and FIG. 8 is a cross-sectional view showing an integrally joined portion of a case body of a tape cartridge and a transparent window plate, and FIG. 9 (a). -(B) is a sectional view of a molding die. 10 (a) and 10 (b) are sectional views of a molding die showing another conventional example. 1 ... Case body, 2 ... Window hole, 3 ... Transparent window plate, 5 ... Upper mold, 6 ... Lower mold, 7 ... Slide core, 7a ... Upper end of slide core, 8 ... … Primary molding space, 9… Gas vent slit, 10… Secondary molding space, 15… Gas vent passage.

Claims (2)

[Claims] 1. A step of primary molding a case body 1 having a window hole 2 with upper and lower molds 5 and 6 for molding the case body and a slide core 7 for molding a window hole in the lower mold 6. When the slide core 7 is retracted, the window hole 2 of the case body 1
It comprises a step of secondarily molding the transparent window plate 3 therein, and a degassing slit 9 communicating with the primary molding space 8 is provided at a joint surface portion with the slide core 7 at the upper end of the lower mold 6. During the secondary molding, the slide core 7 is retracted to a position lower than the lower mold 6 so that the secondary molding space
10. A method of molding a tape cartridge case, wherein 10 is formed so as to communicate with the gas vent slit 9. 2. A step of primarily molding a case body 1 having a window hole 2 with upper and lower molds 5 and 6 for molding the case body and a slide core 7 for molding a window hole in the lower mold 6. When the slide core 7 is retracted, the window hole 2 of the case body 1
It comprises a step of secondarily molding the transparent window plate 3 therein, and a degassing slit 9 communicating with the primary molding space 8 is provided at a joint surface portion with the slide core 7 at the upper end of the lower mold 6. The whole or part of the peripheral surface of the upper end 7a facing the inner peripheral surface of the window of the slide core 7 is formed in a cross-sectional shape such that it has a plurality of steps in the thickness direction of the window plate, and the secondary molding is performed. By retreating the slide core 7 in FIG. 3, a gas vent passage 15 communicating with the secondary molding space 10 is formed between the upper end 7a of the slide core 7 and the gas vent slit 9. To form a tape cartridge case.