JPS6353634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a vertically divided cartridge case for various tape cartridges for video and audio using plastic injection molding. The purpose is to reliably prevent partial cracking of the case that tends to occur when the case is extracted from the mold.

For example, in a video tape cartridge as shown in FIG. 1, a tape reel 2, on which tape T is wound on the left and right sides of a case body 1, which is formed by connecting upper and lower cases 1A and 1B with screws or the like, with lids fitted together;
2 is installed inside the case body 1, and a front cover 3 for tape protection that covers the front side of the case body 1 is pivotally supported so as to be operable to open and close.
The tape T is led out from one reel 2 to the front of the case and wound onto the other reel 2. When the tape cartridge is not in use, the tape T led out to the front of the case is protected by the front lid 3 in the closed position, and the tape is When the cartridge is loaded into the video deck, the front cover 3 is opened upward and the tape T is put into a standby state where it can be pulled out to the front of the case.

The upper and lower cases 1A and 1B, which are divided into halves and constitute the case body 1, are molded plastic products, and have the shape shown in FIG. 2.

First, the upper case 1A has an outer surface on the outer periphery of a flat, rectangular main wall 5 (constituting the upper wall of the case body 1), which has transparent windows 4 on the left and right sides for visually checking the amount of tape wound on each tape reel 2. A front wall 6, a rear wall 7, and left and right side walls 8, each of which serves as a tape running surface, are erected.
On the inner side of these peripheral walls, a partially arc-shaped standing wall 9 for regulating tape reel movement and a cylindrical standing wall 10 into which a tape end detection lamp is inserted are erected from the inner surface of the main wall 5, and a tape guide member A support shaft 11 that inserts and supports the case and also serves as a screw fastener, a boss 12 for screw fastening the upper and lower cases, etc. are also attached to the main wall 5.
It has a shape that stands up from the inner surface.

The lower case 1B has a flat, rectangular main wall 5 (constituting the bottom wall of the case body) having drive shaft insertion holes 13 on the left and right sides, and various vertical wall groups of the upper case 1A and others, as indicated by the same reference numerals for convenience. An upright object is provided that corresponds to the upright object and is butted against the upright object.

When injection molding the upper and lower cases 1A, 1B having such a shape, a first mold for molding the inner surface of the main wall 5 and various groups of vertical walls will be explained based on FIGS. 5 and 6, which will be described later. 16 (which has a deep molding space) and a second mold 17 for molding the outer surface of the main wall 5.
A knock pin is provided on the side for extracting the molded product.

However, the conventional knock pin is indicated by the reference numeral 14 in FIGS. 5 and 6, and has a configuration in which the tip end surface of the knock pin comes into contact only with the inner surface of the main wall 5.

Therefore, when extruding a molded product using such a dowel pin, if there is a part of the vertical wall group with poor mold releasability, cracks tend to occur in that part.

In particular, in this type of cartridge case, the standing walls are concentrated on the front side and high precision is required, so there is a tendency for the material injection gate during injection molding to be installed on the front side. However, the injection pressure is higher than other parts, and the degree of adhesion to the inner surface of the mold is also stronger, resulting in poor mold releasability.
Of course, the mold releasability is also likely to deteriorate in areas where other groups of standing walls are crowded, regardless of the material injection gate. Although a large number of dowel pins are placed in areas where mold release is poor, it is still not possible to completely eliminate the possibility of partial cracks occurring in the case.

Therefore, the present invention seeks to provide a method for manufacturing a tape cartridge case that is effective in preventing cracking of the case during extraction and separation of such molded products.

The details will be explained below by taking as an example the case where the cases 1A and 1B of the video tape cartridge mentioned above are injection molded.

FIG. 3 is a plan view of the inner surface of the upper case 1A, and FIG. 4 is a plan view of the inner surface of the lower case 1B, viewed from above, and the basic form thereof is as already described.
However, the reference numeral G in the figure indicates a material injection gate, which is provided on the front vertical wall 6 in the figure. 1
4 and 15 indicate knock pins.

FIG. 5 shows the molding state taken along the line A-A in FIG. 9), and a second mold 17 that molds the outer surface of the main wall 5 are used. A material injection gate G is correspondingly arranged, and a large number of groups of round shaft-shaped knock pins 14 and 15 are arranged on the first mold 16 side so as to be movable in and out.

What should be noted here is that the tip of the knock pin (located near the rear wall 7 in FIG. 5) indicated by the reference numeral 14 acts only on the inner surface of the main wall 5, as in the conventional case. The stepped knock pin 15 on the front wall 6 side has a step 18 formed on the outer periphery of the tip side, and this step 18 partially overlaps the upper end surface of the front wall 6.

In this stepped knock pin 15, a flat outer surface 19 on the tip side of the step 18 serves as a molding surface for a part of the inner surface of the front wall 6, and the step 18 serves as a molding surface for a part of the upper end surface of the front wall 6. It's summery.

In such a case, as shown in FIG. 6, when the second die 17 is removed and the groups of dowel pins 14 and 15 are made to protrude when the molded product is extracted after molding, the tip surfaces of these groups of dowel pins 14 and 15 touch the main wall 5. At the same time as pressing the inner surface, the step 18 of the stepped dowel pin 15 presses the upper end surface of the front wall 6, giving an extrusion action from the inner end of the deep molding space, so even if the mold release property is poor at this location, It can be extruded reliably without cracking.

FIG. 7 shows another embodiment of the present invention, in which a standing wall 20 in the form of a rib is provided in advance from the front wall 6 to the main wall 5, and a stepped knock pin is attached to this standing wall 20. 15 operates in the same manner as described above. This is advantageous because no knock pin marks remain on the upper end surface of the front wall 6, that is, the lid mating surface.

Further, in the present invention, the stepped knock pins 15 selectively act on the rear wall 7 instead of the front wall 6, the left and right side walls 8, the vertical wall 9 for regulating tape reel movement, the cylindrical vertical wall 10 for inserting a lamp, etc. Needless to say, it may be arranged as such.

In addition, the case body 1 is not limited to a so-called half case that is divided into upper and lower halves, and a flat plate-shaped upper surface is formed on the opening upper surface of the lower case 1B with a group of vertical walls protruding from the main wall 5. Case 1
A may be of a form in which the lids are brought together and integrally connected, and in such a case, the method of the present invention would be carried out when manufacturing the lower case 1B.

As explained above, according to the method of this invention,
A stepped knock pin 15 is used for the group of knock pins for extracting the molded product, and the stepped knock pin 18 presses the end face of the vertical wall 6 (represented by reference numeral 6 for convenience) to extract the molded product, allowing deep molding. This is effective in preventing cracking when the vertical wall 6 is extracted from the space.
In particular, the stepped knock pin 15 not only presses the end surface of the standing wall 6, but also supports the inner surface of the standing wall 6 with the outer surface 19 on the tip side of the step 18, and supports the inner surface of the main wall 5 with the tip end surface of the pin. Since the inner surface of the main wall is pressed at the same time, there is no occurrence of deep pressure marks due to stress concentration on the end face of the upright wall, which would be expected if only the end face of the upright wall 6 was pressed with a small-diameter dowel pin.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a tape cartridge, Fig. 2 is a divided perspective view of an upper case and a lower case that constitute the case body, Fig. 3 is a plan view showing the inner surface of the upper case, and Fig. 4 5 is a plan view showing the inner surface of the lower case, FIG. 5 is a sectional view taken along the line A-A in FIG. It is a diagram. FIG. 7 is a plan view of essential parts showing another embodiment of the method of the present invention. 1...Case body, 1A...Upper case, 1B...
... lower case, 5 ... main wall, 6 ... front wall, 7 ... rear wall, 8 ... left and right side walls, 9 ... standing wall for regulating tape reel movement, 10 ... cylinder into which the lamp insertion hole is inserted 14...Knock pin, 15...Stepped knock pin, 16...First mold, 17...Second mold, 18...Step of stepped knock pin, 19...More than step of stepped knock pin Outer surface on the tip side, G...
...Material injection gate.

Claims (1)

[Scope of Claims] 1. When manufacturing a case for a tape cartridge of a vertically split type in which a group of vertical walls are integrally connected from the inner surface of a flat main wall 5, a first step is performed to form the inner surface of the main wall 5 and the group of vertical walls. It is equipped with a mold 16, a second mold 17 for molding the outer surface of the main wall 5, and a group of knock pins 14 and 15 for ejecting the molded product provided on the first mold 16 side. A selected knock pin 15 of the 15 groups has a step 18 formed on the outer periphery of the tip side, and an outer surface 19 on the tip side of the step 18 becomes a molding surface for a part of the inner surface of the selected vertical wall 6. At the same time, the step 18 becomes a molding surface for a part of the end surface of the vertical wall 6, and both molds 1
After the plastic material is injected into the molding space between 6 and 17 and cooled and solidified, both molds 16 and 17 are separated, and then the groups of dowel pins 14 and 15 are operated to project and the molded product is removed from the first mold 16. A method for manufacturing a case for a tape cartridge, characterized in that when pulling out the tape cartridge case, the tip surface of the stepped dowel pin 15 presses the inner surface of the main wall 5, and at the same time, the step 18 presses the end surface of the vertical wall 6. 2. The method for manufacturing a tape cartridge case according to claim 1, wherein the stepped knock pins 15 are arranged in a densely packed area of the group of vertical walls. 3 The stepped knock pin 15 is the material injection groove G
A method for manufacturing a tape cartridge case according to claim 1 or 2, wherein the tape cartridge case is disposed near the tape cartridge case.