JP2001243742A - Magnetic tape cassette and metallic mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape cassette provided with a cassette half having no fear of generating shrinkage at a position corresponding to a required objective hole even when the cassette half is not provided with required objective hole such as a discrimination hole and to provide a metallic mold for molding the cassette half. SOLUTION: The magnetic tape cassette is distinguished by making the position corresponding to the required objective hole of the cassette half to a rugged shape generating no shrinkage and constituting a flat surface at an upper face of the projected part. The metallic mold for the magnetic tape cassette is distinguished by providing an insert for forming the rugged shape with plural layer structure having a boundary part capable of degassing along a mold-releasing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape cassette such as a digital video cassette (DVC) and a mold for the magnetic tape cassette.

[0002]

2. Description of the Related Art In general, in audio equipment, video equipment and the like, a magnetic tape cassette for recording / reproducing a magnetic tape wound around a pair of tape reels so as to be able to run in a cassette half is often used. .

[0003] Referring to FIG. 4, a pair of tape reels 31 wound with a magnetic tape t is mounted in a lower cassette half 33 paired with an upper cassette half 32 as a magnetic tape cassette 30 conventionally used for DVC, for example. To
Some are rotatably supported.

Tape guides 35 are provided on both sides of the opening 34 in the lower cassette half 33 on the near side in FIG. Each tape guide 35 is sent from one tape reel 31 to the other tape reel 31.
And guides the magnetic tape t to pass through a predetermined position in the opening 34.

On the rear side of the lower cassette half 33, a reel lock member 39 having a tape reel locking arm 38 is provided. Reel lock member 39
Is urged by a compression coil spring 40 to move the tape reel locking arm 38 to each tape reel 3.
The tape reel 31 is engaged with the engaging teeth 41 formed on the outer circumference of the tape reel 1 to prevent the tape reels 31 from being accidentally rotated. This prevents loosening of the magnetic tape t.

An outer lid 50, a top lid 52, and an inner lid 51 that cover the opening 34 of the lower cassette half 33 are respectively attached to the upper cassette half 32 so as to be freely opened and closed.

A lock pin 54 projects from the side plate 53 of the outer lid 50. The lock pin 54 is provided with a lid lock 55 rotatably provided on the lower cassette half 33.
Is locked. Reference numeral 56 denotes a lid spring that biases these lids to a closed state.

[0008]

As for the usage of the magnetic tape cassette, it is possible to use a common cassette half for different types of magnetic tapes so that it can be adapted to different recording systems. In this case, for example, it is conceivable to form a hole for identifying the magnetic tape in the cassette half. FIG. 5 shows the lower cassette half 33 configured as described above.
FIG.

For example, as shown in FIG. 5A, an identification hole 70 is formed in the lower cassette half 33 for accommodating the type A magnetic tape, and the lower cassette half 33 for accommodating the type B magnetic tape. By not forming the identification holes 70 as shown in FIG. 5B, a common lower cassette half 33 can be used to accommodate the two types of magnetic tapes A and B, respectively.

When the lower cassette half 33 having the identification hole 70 and the lower cassette half 33 having no identification hole 70 are formed by the same die, the identification die 70 can be formed by forming the identification hole 70 by nesting. In addition, the mold configuration is simple. Such a mold is shown in FIGS.

FIG. 6 shows a mold for forming an identification hole, and FIG.
Denotes a mold that does not form an identification hole. In the drawing, the upper mold is the fixed side, and the lower mold is the movable side. As the fixed mold 80, a nest 82 for forming an identification hole and a nest 83 without an identification hole are used interchangeably.
Can be used in common, thereby reducing the cost and simplifying the mold.

However, if the movable mold 84 is made common and the portion 72 corresponding to the identification hole 70 remains thick, the lower cassette half 33 moves integrally with the movable mold 84 in the mold opened state after the completion of molding. Therefore, since the cooling is not uniform, sink marks 74 are generated in the portions 72 corresponding to the identification holes 70 as shown in FIG. Then, in the recording / reproducing apparatus, the part of the sink mark 74 may be erroneously detected as the identification hole 70 even though the identification hole 70 is not provided.
In this case, correct operation of the magnetic tape cassette cannot be guaranteed. In particular, when the portion 72 corresponding to the identification hole is near the positioning hole 6, the accuracy of the positioning hole 36 itself is adversely affected.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and to provide a cassette half which does not have a required hole such as an identification hole and which does not cause sink marks at a portion corresponding to the required hole. An object of the present invention is to provide a magnetic tape cassette having halves and a mold for molding the cassette halves.

[0014]

The above object of the present invention is achieved by the following constitution. A magnetic tape cassette having a cassette half that is formed by using a mold and a cassette half having a required target hole and does not have the required target hole formed in a portion corresponding to the required target hole, wherein the cassette half has a required purpose. A magnetic tape cassette, wherein a portion corresponding to a hole has an uneven shape so as not to cause sink marks, and has a shape in which a flat portion is formed on an upper surface of the convex portion.

[0015] A mold provided with a nest for forming the concave and convex shape for producing the cassette half described above, wherein the nest has a boundary portion capable of degassing along a releasing direction. The mold for a magnetic tape cassette having a layer structure.

According to the present invention, since the portion corresponding to the required target hole of the cassette half has an uneven shape, the surface area is large, and even in the mold opened state after molding, cooling is promoted and sink is greatly reduced. I do. Therefore, a flat surface is accurately formed on the upper surface of the convex portion, and the recording / reproducing apparatus accurately detects that there is no required target hole. For example, if the required hole is a tape type identification hole as described above, the recording / reproducing device accurately detects that there is no identification hole in the cassette half, and in the recording / reproducing device, correct operation of the magnetic tape cassette is guaranteed. Is done.

In the present invention, examples of the required target hole include a hole for identification and a hole for exerting a specific function by itself when the cassette is operated.

Further, in the present invention, the convex portion forming the unevenness has a flat upper surface and the upper surface is set at the same height as the outer surface of the cassette half. It is preferable that the height of the convex portion is not less than the outer diameter. According to the experience of the present inventor, if the height of the convex portion is not less than the outer diameter, even if the convex portion has sink marks,
It does not occur on the upper surface but occurs on the side surface. Therefore, the height position of the upper surface does not change, and the recording / reproducing apparatus accurately detects that there is no required target hole.

[0019]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a bottom view of the lower half case of the magnetic tape cassette according to the embodiment of the present invention. The configuration of the present embodiment is basically the same as that of the conventional magnetic tape cassette shown in FIG. 4, so that the description of the configuration other than the lower half case is omitted.

The magnetic tape cassette has a pair of positioning holes 36 on the front side of the lower half 33 as an index of positioning in the recording / reproducing apparatus. Then, in the recording / reproducing device,
The cassette is positioned by inserting the positioning pins into the positioning holes 36 from below the cassette.

In the case of the lower half case 33 accommodating the type A magnetic tape, for example, an identification hole for identifying the type of the accommodated magnetic tape is provided near the positioning hole 36. In the recording / reproducing apparatus, the identification hole is used to identify the type of the magnetic tape, such as the recording density and the recording method. At the time of identification, for example, a mechanical method by inserting a pin into an identification hole, or an optical method of irradiating light and detecting the reflected light can be adopted.

On the other hand, in the case of the lower half case 33 accommodating the type B magnetic tape, as shown in FIG. 1, an uneven portion 76 is formed at a portion 72 corresponding to the identification hole 70.

FIG. 2A is a perspective view of a portion 72 corresponding to the identification hole of the lower cassette half 33 having no identification hole 70, FIG. 2B is a plan view, and FIG. A)
It is -A sectional drawing.

The part 72 corresponding to the identification hole has the identification hole 7
0 is not formed, and instead, an uneven portion 76 for preventing sink is formed. The uneven portion 76 includes a central pillar portion 76a, an outer groove 76b, an outer annular rib 76c, and an outer groove 76d. Column 76
a and the upper surfaces of the annular ribs 76 c are flush with the outer surface of the lower cassette half 33. In the recording / reproducing device, the convex portion 76
By detecting the upper surface of “a”, it is detected that there is no identification hole.

According to the present embodiment, since the uneven portion 76 is formed in the portion 72 corresponding to the identification hole, the portion 72 corresponding to the identification hole has a larger surface area than a flat surface. . Therefore, even if the mold is opened after injection molding and the lower cassette half 33 moves integrally with the movable mold 84,
The portion 72 corresponding to the identification hole radiates heat well and does not cause sink marks. In particular, since the column portion 76a radiates heat well from the upper surface and the peripheral surface, sink does not occur on the upper surface. As described above, since heat is radiated in the portion 72 corresponding to the identification hole mainly in the column portion 76a, the outer groove 76d may be omitted.

It is preferable that the height h of the column portion 76a is not less than the diameter d. If the height h is equal to or greater than the diameter d, the column portion 76a has sink marks even on the peripheral surface of the column portion 76a and does not occur on the upper surface of the column portion 76a even if sink marks may occur.

The column portion 76a and the annular rib 76c are
Although formed perpendicular to the bottom surface of the lower cassette half 33, a draft angle may be formed in these for easy release.

As in the present embodiment, the half case 3 having a portion 72 corresponding to the identification hole near the positioning hole 36.
In the case of No. 3, if a sink occurs in the portion 72 corresponding to the identification hole, the sink also affects the neighboring positioning hole 36, and the molding accuracy of the positioning hole 36 is reduced. But,
In the present embodiment, since there is no sink mark in the portion 72 corresponding to the identification hole, the portion 72 corresponding to the identification hole can be accurately molded, and as a result, there is also an effect that the molding accuracy of the neighboring positioning hole 36 does not decrease. .

Next, a description will be given of a nest used to form the concave and convex portions 76 used in the dies 80 and 84 for forming the lower half case 33. FIG. 3 is a longitudinal sectional view of the nest 90 forming the uneven portion 76. The insert 90 includes a central core 92, a first sleeve 94 fitted outside the core 92, and a second sleeve 96 fitted outside the first sleeve 94. Core 92 and first sleeve 94
A column portion 76a of the uneven portion 76 is formed at the lower end of the first sleeve 94 and the lower end of the second sleeve 96.
Is formed. The grooves 76b and 76d are formed at the lower ends of the first sleeve 94 and the second sleeve 96, respectively.

Since the nest 90 has a multi-layer structure in which the core 92 and the first and second sleeves 94 and 96 are fitted, the boundary 1 between the core 92 and the first sleeve 94, The boundary S2 between the first sleeve 94 and the second sleeve 96 is along the releasing direction. These boundaries S1,
In S2, the entire area is not in close contact with each other, and an extremely small gap is partially generated microscopically. As a result, the molten resin does not enter the boundaries S1 and S2, but the gas generated from the molten resin can pass through the boundaries S1 and S2.

Therefore, each of the members 92, 9 as described above
Boundary parts S1, S along the release direction by fitting of 4,96
By forming the concave and convex portions 76 using the nest 90 having two, each member 92, 94, 96 at the time of filling the molten resin.
The gas can satisfactorily escape from the boundary portions S1 and S2 between them, and a short shot can be prevented.

The nest 90 has two grooves 7 shown in FIG.
Although the uneven portion 76 having 6b and 76d is formed, when forming the uneven portion 76 in which the outer groove 76d is omitted, the nest 90 has a configuration in which the second sleeve 96 is omitted.

It should be noted that the present invention is not limited to the above-described embodiment, but can be appropriately changed and improved based on the gist of the present invention. For example, as the shape of the uneven portion, any shape can be adopted as long as there is a flat portion on the upper surface of the convex portion. Further, for example, the portion corresponding to the identification hole does not have to be near the positioning hole, and may be an arbitrary portion of the half case.

The function of the identification hole may be a mechanical identification or an optical identification. In the above-described embodiment, the portion corresponding to the identification hole is formed. However, the same effect can be obtained when a flat portion is formed not in the identification hole but in a portion corresponding to another target hole.

Although the above embodiment is a DVC, the present invention is not limited to the DVC, but can be applied to any magnetic tape cassette. The recording / reproducing method, magnetic tape width, cassette size, and the like are not limited.

[0036]

According to the present invention, when the required target hole is not formed in a portion corresponding to the required target hole using the same half case as the magnetic tape cassette having the required target hole, the required target hole is used instead of the required target hole. Since the portion corresponding to the required target hole is formed as a flat surface by the upper surface of the convex portion having the uneven shape which does not cause sink marks, a half case which is not erroneously detected as having the required target hole can be accurately formed. Therefore, the magnetic tape cassette can be accurately identified, and correct operation of the magnetic tape cassette in the recording / reproducing apparatus is guaranteed.

[Brief description of the drawings]

FIG. 1 is a bottom view of a lower half case of a magnetic tape cassette.

FIGS. 2A and 2B show an uneven portion formed at a portion corresponding to an identification hole, where FIG. 2A is a perspective view, FIG. 2B is a plan view, and FIG.
It is AA sectional drawing of.

FIG. 3 is a longitudinal sectional view of a nest forming an uneven portion.

FIG. 4 is an exploded view of the magnetic tape cassette.

5A and 5B are bottom views of a lower half case of a conventional magnetic tape cassette, FIG. 5A is a bottom view of a lower half case having an identification hole, and FIG. 5B is a bottom view of a lower half case without an identification hole. .

FIG. 6 is a sectional view of a mold for forming a lower half case having an identification hole.

FIG. 7 is a sectional view of a mold for forming a lower half case without an identification hole.

FIG. 8 is a cross-sectional view illustrating sink marks generated in a lower half case having no identification hole.

[Explanation of symbols]

 31 Tape Reel 32 Upper Half Case 33 Lower Half Case 35 Tape Guide 36 Positioning Hole 72 Location Corresponding to Identification Hole 74 Sink 76 Irregularity 76a Column 76b, 76d Groove 76c Annular Rib 80 Fixed 82,90 Nest 84 Movable 92 Core 94 First sleeve 96 Second sleeve S1, S2 Boundary part

Claims (2)

[Claims] 1. A magnetic tape cassette comprising a cassette half having a required target hole and a cassette half formed as a mold and not having the required target hole at a portion corresponding to the required target hole. A magnetic tape cassette, wherein a portion corresponding to the required target hole of the half has an uneven shape so as not to cause sink marks, and has a shape in which a flat portion is formed on an upper surface of the convex portion. 2. A mold for forming the cassette half according to claim 1, further comprising a nest for forming the concave-convex shape, wherein the nest is a boundary capable of degassing along a mold releasing direction. A mold for the magnetic tape cassette, wherein the mold has a multi-layer structure having a portion.