JPS58130474A - Manufacture of case for tape cartridge - Google Patents

Abstract

PURPOSE:To remove moldings from deep molding cavities easily with good yields by providing steps to some of knock pin groups for ejection of moldings to press the end parts of the walls of the moldings with the stepped parts to remove the moldings. CONSTITUTION:Many knock pin groups 14, 15 are disposed freely and movably in and out to the 1st mold 16 which molds the entire part of a main wall 5 and standing wal groups (only the standing walls 6, 7 and the standing wall 9 for regulating the loose moving of a tail pulley are shown in the figure) and a mold 17 which molds the outside surface of the wall 5. A gate G for injecting raw material is disposed. Some of the groups 14, 15 are provided with steps 18 in the outside circumferential parts 5 on the forward end side as shown in figure 15 in such a way that the stepped parts 18 abut on the top end faces of the front wall 6. The flat outer side surface 19 of each knock pin 15 on the more foward side than the step 18 forms the molding surface for a part of the inside surface of the wall 6 and the step 18 forms the molding surface in a part of the top end surface of the wall 6. After the molding, the mold 17 is removed to project the knock pins and to remove the moldings easily with good yields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a top and bottom split cartridge case for various tape cartridges for video and audio by plastic injection molding. For example, in a video tape cartridge shown in Fig. 1, the upper and lower cases IA and IB are closed with lids to prevent partial cracking of the case, which tends to occur when the case is removed from the cartridge. Inside the case body 1, which is joined together with screws etc., there are tape reels 2, 2 on which tape T is wound on the left and right sides, and a front cover 3 for protecting the tape that covers the front of the case body 1 can be opened and closed. The front lid is operable and pivoted, and the tape T is led out from one reel 2 to the front of the case and wound onto the other reel 2, and the tape T led out to the front of the case is closed when the tape cartridge is not in use. 3, and when the tape cartridge is loaded into the video deck, the front cover 3 opens upward and the tape T is placed in a standby state where it can be pulled out to the front of the case. Upper and lower case IA@
IB is a plastic molded product, and its shape is as shown in FIG.

First, the upper case IA has an outer surface on the outer periphery of a flat, rectangular main wall 5 (constituting the earthen 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, which serve as tape running surfaces, are set upright, and a partially arc-shaped standing wall 9 for regulating tape reel movement and a lamp for detecting tape ends are inserted on the inner side of these peripheral walls. A cylindrical stand 910 is erected from the inner surface of the main wall 5, and a support shaft 11 that inserts and supports the tape guide member and also serves as a screw fastener, a boss 12 for screw fastening the upper and lower cases, etc. are also provided on the main wall 5. It has a shape that stands up from the inner surface of 5.

The lower case IB has a flat, square 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 walls of the upper case IA, as indicated by the same reference numerals for convenience. Standing bladders are provided which matingly abut against the groups and other standing stations.

When injection molding the upper and lower cases IA and IB having such shapes, the description will be made 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 for extracting the molded product is provided on the first mold 16 side.

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 the material injection gate during injection molding tends to be installed on the front side.
Naturally, the injection pressure near this gate is higher than in 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 with poor mold releasability, it is still not possible to completely eliminate the possibility of partial cracks occurring in the case.

(5) 512 Therefore, it is an object of the present invention to provide a method for manufacturing a case for a tape cartridge that is effective in preventing cracking of the case when such a molded product is extracted and separated.

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

Figure 3 shows the inner surface of upper case IA, and Figure 4 shows the inner surface of lower case IB.
FIG. 3 is a plan view of the inner surface of the device, viewed from above, and its basic form 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. 14 and 15 indicate dowel pins.

FIG. 5 shows the molding state taken along the line A-A in FIG. A first mold 16 for molding the entire vertical wall 9) and a second mold 17 for molding the outer surface of the main wall 5 are used.
A material injection gate G is arranged corresponding to the molding part of the front wall 6, and a large number of groups of round shaft-shaped dowel pins 14 and 15 are arranged on the (6)-l mold 16 side so that they can move in and out. .

What should be noted here is the knock pin (5th
The knock pin 15 located near the rear wall 7 in the figure) has its tip surface acting only on the inner surface of the main wall 5 as in the past, whereas the knock pin 15 on the front wall 6 side has an outer peripheral portion on the tip side. A step 18 is formed on the front wall 6, 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 has become.

In such a case, in Fig. 6, when removing the molded product after molding, after removing the second mold 17,
When the fifth group is protruded, the tip surfaces of these dowel pin groups 14 and 15 press the inner surface of the main wall 5, and at the same time, the step 18 of the stepped knock pin 15 presses the upper end surface of the front wall 6, creating a deep molding space. Since the extrusion action is applied from the inner end of the mold, even if the mold releasability is poor at this point, the mold can be reliably extruded without cracking.

FIG. 7 shows another embodiment of the present invention. In this case, a rib-like standing wall 20 is provided in advance from the front wall 6 to the main wall 5, and a stepped knock pin 15 is attached to this standing wall 2o.
is designed to function 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.

Furthermore, the case body 1 is not limited to a so-called half case that is divided into upper and lower halves. The case IA may have a form in which the lids of the case IA are joined together, and in such a case,
The method of the invention will be carried out in the manufacture of the lower case IB.

As described above, according to the method of the present invention, the stepped knock pin 15
The molded product is extracted by pressing the end face of the vertical wall 6 (represented by reference numeral 6 for convenience) at the step 18, which is effective in preventing cracking when the vertical wall 6 is extracted from a deep molding space. be.

In particular, the stepped knock pin 15 not only presses the end surface of the vertical wall 6, but also presses against the vertical wall 6 with the outer surface 19 on the tip side of the vertical wall 6.
, and simultaneously suppresses the inner surface of the main wall 5 while supporting the inner surface of the main wall 5 with the tip end surface of the pin, which is expected when only the end surface of the vertical wall 6 is pressed with a small-diameter dowel pin. There are no deep pressure marks caused by stress concentration on the end face of the vertical wall.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing -i of the tape cartridge;
The figure is a divided perspective view of the upper case and lower case that make up the case body. Figure 3 is a plan view showing the inner surface of the upper case.
The figure is a plan view showing the inner surface of the lower case, Figure 5 is a sectional view taken along line A-A in Figure 4 showing the state of mold molding of the lower case, and Figure 6 shows the state of the molded product being pulled out after molding. FIG. FIG. 7 is a plan view of essential parts showing another embodiment of the method of the present invention. 1...Case body IA...Upper case 1B...Lower case 5...Main wall 6...Front wall 7...Rear wall 8...Right and left side walls 9...Tape reel movement regulation Standing wall 10 for lamp insertion... Cylindrical standing wall 14 into which the lamp insertion hole is inserted... Dowel pin 15... Stepped knock pin 16... First mold 17... Second mold 18... Step Step 19 of the stepped knock pin...Outer surface G on the tip side of the step of the stepped knock pin...Material injection gate patent applicant Hitachi Maxell Ltd. Figure 5 19 Figure 6 Figure 7

Claims (3)

[Claims] (1) A first mold 16 for molding the inner surface of the main wall 5 and the group of vertical walls when manufacturing a tape cartridge case of a vertically split type in which a group of vertical walls are integrally connected from the inner surface of the flat main wall 5; a second mold 17 for molding the outer surface of the main wall 5;
Knock pin 1 installed on the mold 16 side for ejecting the molded product
It is equipped with 4 and 15 groups, and these dowel pins are 14 and 1.
The dowel pin 15 selected from the five groups has a step 18 formed on the outer periphery of the tip side, and the 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 the molding surface for a part of the end face of the vertical wall 6, and after injecting the plastic material into the molding space between the molds 16 and 17 and cooling and solidifying it with a saw, the molds 16 and 1 Separate the heat and then operate the dowel pins 14 and 15 to move the molded product to the first position.
A case for a tape cartridge characterized in that, when extracted from the mold 16, the tip end face 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 face of the vertical wall 6. Production method. (2) The method for manufacturing a case for a tape cartridge 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 method for manufacturing a tape cartridge case according to claim 1 or 2, wherein the stepped knock pin 15 is arranged near the material injection gate G.