JPH0454630Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a VHS video cassette case, and particularly to a video cassette case that can improve the molding balance during injection molding.

"Prior art" Figures 4 to 6 show conventional VHS technology, respectively.
This is an example of a video cassette case.

This video cassette case is composed of an upper case 1, a lower case 2, and a guard panel 3, and a pair of tape reels 4, 4 are housed inside the video cassette case.

The outer bottom of the upper case 1 has windows 5, 5 for checking the remaining amount of tape, and a recess 6 with a depth of 0.5 mm (indicated by diagonal lines in the figure) into which the upper panel with the product name etc. written is fitted. part) is formed. Since the thickness of the bottom surface of the upper case 1 is defined by the standard to be 2.0 to 2.2 mm, the thickness of the portion where the recess 6 is formed is 1.5 to 1.7 mm. In the upper case 1, a gate during injection molding is set in the recess 6, and reference numeral 7 indicates the remains of the gate.

On the other hand, the bottom of the lower case 2 has openings 8, 8 for exposing the lower ends of the tape reels 4, 4.
is formed. The wall thickness of this bottom surface is set to 2.0 to 2.2 mm similarly to the upper case 1. Also,
The gate for molding the lower case 2 is set at the center of the outer bottom surface, similar to the upper case 1.
Reference numeral 9 is the remains of that gate.

"The problem that the invention attempts to solve" By the way, the above-mentioned upper case 1 and lower case 2 are as follows:
Usually, multiple pieces are injection molded at the same time using the same mold. However, during injection, resin may not be injected into the upper case molding cavity sufficiently, causing sink marks on the upper case 1 after molding, or excessive resin may be injected into the lower case cavity, causing burrs on the lower case 2. It has been pointed out for some time that the problem is that it is difficult to improve dimensional accuracy due to the formation of thick parts (poor molding balance).

The applicants believe that the reason why the resin filling rate in each cavity of the mold is not uniform is that the flow resistance of the molten resin is different in each cavity, so they changed the opening area of the gate that opens into each cavity. An attempt was made to equalize the flow resistance. However, it is difficult to change the opening area of the gate without disturbing the injection and mold release cycles, and satisfactory results have not been obtained.

Therefore, the present applicants reexamined the cause of the non-uniformity of the liquid flow resistance and found that the wall thickness of the gated part of the upper case was greater than that of the lower case part where the gate was set. It was found that the flow resistance was increased because the wall thickness was 0.5 mm thinner due to the depth of the recess for fitting the panel.

``Purpose of the invention'' This invention was made in view of the above circumstances, and it makes it possible to equalize the resin filling rate into the cavities of the upper case and lower case during upper molding, improve the molding balance, and improve dimensional accuracy. The purpose is to provide a video cassette case that allows for

``Means for Solving the Problems'' The video cassette case of the present invention has a structure in which the wall thickness of the upper case where the gate is set is equal to the wall thickness of the lower case where the gate is set. It is characterized by what it did.

"Embodiments" Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 each show a video cassette case of one embodiment, with FIG. 1 being a plan view of the lower case 10, and FIG. 2 being a sectional view taken along the line --. Note that the same parts as the conventional one include:
The same reference numerals are used to omit the explanation.

The lower case 10 of this embodiment is characterized by a recess 1 having the same depth (0.5 mm) and the same area as the recess 6 for fitting the panel of the upper case 1 in the center of its inner bottom surface.
1 is formed. This recess 11 is
Its peripheral edge is slightly spaced apart from the openings 8, 8 and ribs etc. 10A formed on the inner wall of the case, and is formed so as to face the gate mark 9 for molding the lower case.

According to the video cassette case having such a configuration, the recessed portion 11 is formed at a position facing the gate mark 9 of the lower case 10, and the thickness of this portion is made smaller than that of the upper case 1.
In addition to making the area of the recesses 6 and 11 the same as that of the gate trace 7, the areas of the recesses 6 and 11 are made to be the same, thereby reducing the flow resistance of the resin flowing into the lower case molding cavity of the mold during injection molding and the upper part. The flow resistance to the case molding cavity can be made approximately equal. Therefore, it is possible to equalize the resin filling rate into each cavity, prevent uneven thickness or sink marks from occurring in the molded product, and improve the molding accuracy of the case.

Note that the shape of the recess 11 is not limited to that shown in FIG. 1, and it does not necessarily have to be the same as the recess 6 as long as the area is not extremely different. Further, in the above embodiment, the recess 11 is formed on the inner bottom surface of the lower case 10, but a similar recess may be formed on the outer bottom surface of the lower case 11 instead.
Moreover, instead of forming the recess 11 in the lower case 10, as shown in FIG. 21 (about 0.5 mm in height), thereby forming an upper case 20 and a lower case 2.
It is also possible to make the wall thickness of each gate pressure portion 7 and 9 the same. In that case, since the wall thickness of each gate mark 7, 9 is thicker (2.0 mm) than in the previous embodiment, there is an advantage that the flow resistance of the resin can be reduced.

"Effects of the Invention" As explained above, according to the video cassette case of the present invention, by making the wall thickness of the portions of the upper case and lower case where the injection molding gates are the same, it is possible to The flow resistance of the resin flowing into the case molding cavity,
The flow resistance to the upper case molding cavity can be made equal. Therefore, the resin filling rate in each cavity can be made uniform, and uneven thickness or sink marks can be prevented from occurring in the molded product.
It is possible to improve the molding accuracy of the case.

[Brief explanation of the drawing]

1 and 2 show a video cassette case according to an embodiment of the present invention; FIG. 1 is a plan view of the lower case, and FIG. 2 is a cross-sectional view taken along the line -2. Further, FIG. 3 is a longitudinal sectional view of a case of another embodiment of the present invention. On the other hand, Figures 4 to 6 show conventional video cassette cases, with Figure 4 being a plan view of the upper case, Figure 5 being a plan view of the lower case viewed from below, and Figure 6 being a plan view of the - line. FIG. 6... Recess for fitting the panel, 7... Gate trace on the upper case, 9... Gate trace on the lower case, 10
... Lower case, 11 ... Recess for adjusting wall thickness, 20
... Upper case, 21 ... Convex part for adjusting wall thickness.

Claims (1)

[Claims for Utility Model Registration] Consisting of an upper case and a lower case, the upper case has a recess formed in the center of its outer bottom surface into which the upper label is fitted. A video cassette case in which a gate is set, characterized in that the wall thickness of the portion of the upper case where the gate is set is equal to the wall thickness of the portion of the lower case where the gate is set. Video cassette case.