JPS62287492A - Manufacture of tape reel - Google Patents

Abstract

PURPOSE:To make the shape and accuracy excellent by providing a gate part in an extent enclosed by an extension line in an inner tube connecting the center of a tape reel and both ends of fitting place of a clasp of a winding core and the outer periphery of the inner tube, and molding by injecting a resin from the gate part. CONSTITUTION:The extent of a gate part in which the accuracy of a tape reel becomes best is a part 10 enclosed by an extension line in an inner tube connecting the center of the tape reel and both ends 9 of fitting place of a clasp of a winding core 4 and the outer periphery of the inner tube 2. When a caulking boss is in this extent, it is enough to drop the gate at the tip. However, when there is a problem of defective caulking with another side plate due to influence of remaining gate, etc., a projection part 11 is provided in the outer peripheral part of the inner tube 2 and the gate is dropped in this part. If the caulking boss is not available, a recess part 5' is provided on a top plate 5 considering the remaining gate, and the gate is dropped in this part, or a dummy boss 12 is provided, and the gate is dropped at the tip.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a videotape reel and a mold used for molding the same, and particularly relates to a gate having an improved position and structure. The present invention relates to a method for manufacturing a tape reel that can form a tape reel with high precision, and a mold used for molding the same.

[Conventional technology and problems]

The widespread use of home video tape recorders in conjunction with the remarkable development of the electronics industry in recent years is truly astonishing.
be. Along with this, the demand for video tapes and the parts used therein is increasing, and it is extremely important that these parts be manufactured accurately and efficiently.

However, among such parts, tape and reel parts in particular are required to have high precision. In other words, a video tape recorder stores or reproduces image and audio signals on tape, but tape reel components directly wind this tape, and even slight deviations in accuracy can cause problems such as twisting or twisting of the tape. Wrinkles, resulting in image distortion,
This is because it causes noise and the like.

By the way, tape reel components have the following structure, for example. That is, the outline is shown in FIG. 8 showing a plan view of the tape reel component, and FIG.
- A circular side plate 1 and a cylinder 2 located in the center thereof, as seen in the accompanying drawing in which a cross-sectional view along the line A” is shown.
and a tape winding core 4 surrounding the outer periphery of the cylinder 2 via ribs 3, and a projection 6 serving as a center of rotation and a plurality of caulking posts 7 surrounding the projection 6 are provided on the top surface of the top plate portion 5 of the cylinder 2. It is being The other side plate (not shown) (having a hole into which the boss fits) is joined to such a tape reel component, and the boss is caulked to form a tape reel. FIG. 10 shows a cross-sectional view of a runner mold for tape reel molding using the front gate method. In other words, the mold 15 is provided with a gate 16 and a hot tip 17, and the resin is poured from the gate 16 over the entire surface. The tape and reel parts are molded by uniform injection. When making such tape reel parts by injection molding, in order to improve accuracy, it goes without saying that the mold itself must have good precision, but the gate for injecting the resin must be placed in the mold. Where it should be installed is also an extremely important issue. This is because, although sufficient cylindricity is particularly required for the tape core 4 (and cylinder 2) described above, if the resin is not injected uniformly, the tape core etc. may be distorted due to different degrees of shrinkage. This is because the cylindricity is not sufficiently satisfied. This phenomenon is particularly noticeable when the cooling time is shortened to increase the molding cycle, and therefore the selection of the gate position is an issue that also affects productivity.

Therefore, in order to solve this problem, the present inventor has conducted various studies on the gate position in the front gate method, and has developed the first method.
As shown in Fig. 1, it was proposed to provide the gate position at a position corresponding to the tip of the caulking post 7 (publication of Utility Model Publication No. 58-42108). However, these gate positions have the following problems.

In other words, in order to avoid problems when winding the tape, it is necessary to have a cylindricity value of 30μ or less.
The gate is formed on the boss 8 of the caulking post 7 in Fig. 11, and the cylindricity of the manufactured tape reel is about 50 to 80μ, and in some cases, the tape may twist during tape winding. There are problems such as wrinkles and damage to the tape, resulting in distorted images, and phenomena such as the tape breaking when being wound at high speeds have also been observed.

c. Means for Solving Problems] Therefore, the present inventors conducted further research in order to improve the shape accuracy of the tape winding core, and as a result, they completed the present invention.

That is, the present invention provides a tape reel side plate, a cylinder with a lid arranged so as to have an open end in the center of the side plate, a tape winding core on the outer periphery of the cylinder with a lid, and a top plate portion of the cylinder with a lid. When injection molding a tape reel component consisting of a protrusion that serves as the center of rotation and a plurality of caulking bosses, etc.,
The gate part is within the area surrounded by the extension line inside the inner cylinder connecting the center of the tape reel and both ends of the attachment point of the tab on the core, and the outer periphery of the inner cylinder (the shaded area in Figures 1 and 2). The present invention provides a method for manufacturing a tape reel with good shape and precision, which is characterized by forming a tape reel in a shape and injecting resin from the gate portion, and molding the reel, and a mold used therein.

Hereinafter, a tape reel mold used in the manufacturing method of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic view showing the range of gate positions in tape-reel molding used in the present invention.

In injection molding as described above, the range of the gate part where the shape accuracy of the tape reel is the best is the area between the center of the tape reel (the position of the center boss 6) and the attachment of the tab of the core 4, as shown in Figure 1. is an internal cylindrical extension line connecting both ends 9 of the part,
This is a portion 10 (the shaded portion in FIG. 1) surrounded by the outer periphery of the inner cylinder 2. As for the position to drop the gate, if there is a caulking boss within this range, you can drop the gate at the tip of the boss, but if there is a problem with the gate not being properly caulked with the other side plate due to the remaining gate, etc. Convex portion 1 as shown in Figure 2
1 on the outer periphery of the inner cylinder 2 and a gate placed in this area.

In addition, if there is no caulking boss in this range, as shown in FIG.
Alternatively, a dummy boss 12 may be provided as shown in FIG. 4, and a gate may be placed at the tip of the dummy boss 12, as shown in FIG.

The height of the dummy boss 12 needs to be lower than the center boss 6, and preferably the height of the dummy boss 12 is lower than the height of the other side plate 13 (see FIG. 5), as shown in FIG. It is best to set it at the same position as (center, position a) or slightly lower than that.

Regarding the number of gates, either one gate or multiple gates may be used, and is determined as appropriate in consideration of the position of the caulking boss, the shape of the top plate, etc.

The molding method used in the method for manufacturing the tape reel used in the present invention may be either a hot runner type or a cold runner type, and is not particularly limited. Further, the resin used in the present invention may be a commonly used thermoplastic resin.

Examples include ABS, polyacecool (homo or copolymer), polypropylene, polyethylene, polyalkylene terephthalates such as polybutylene terephthalate,
Known fillers such as polyamide can be mixed and used depending on the desired physical properties. A particularly preferred resin is polyacetal.

〔Effect of the invention〕

As is clear from the above description and examples, by installing the gate at an appropriate position as in the present invention in the tape reel injection molding method, the shape accuracy of the molded tape reel can be improved.

〔Example〕

The method for manufacturing a tape reel of the present invention will be further explained below with reference to Examples.

Example 1 A tape reel was formed by dropping a gate onto the tip of a caulking boss shown at 14-1-14-6 in FIG. In order to investigate the relationship between the gate position and the shape accuracy of the tape core,
The roundness and cylindricity were measured and shown in Table 1. The measurement positions were three, s, c, and d in Figure 7. Roundness,
Cylindricity was measured according to JIS' BO621. The molding conditions are injection pressure 700kg/cm! , injection speed:
1 m/min, cycle: injection 10 seconds + cooling 5 seconds.

Table = 1 Here, the smaller the numerical values of roundness and cylindricity, the better. Therefore, it can be seen that the accuracy of the tape reel according to this example is better than that of the comparative example.

Example 2 The relationship between the gate position and the shape accuracy of the tape winding core was investigated using a perforated reel as shown in FIG. 12, and the results are shown in Table 2. In addition, the gate position was the same as in Example 1, and in addition to dropping it on the tip of the caulking boss, as shown in Fig. 6, the gate was placed in the recess (14-9, 14
-10) was also measured. The measurement conditions and molding conditions were the same as in Example 1.

Here, a perforated reel is defined as having a through hole in the side plate of the tape reel (although there are no particular limitations on the shape,
The reel used in this embodiment is a tape reel in which a tape reel side plate is formed of radial ribs 19 extending from a strip 18 and outer peripheral ribs 20.

In addition, in FIG. 12, 21 indicates a retaining tooth.

[Brief explanation of drawings]

1 and 2 are plan views showing preferred gate positions according to the present invention, FIGS. 3 and 4 are schematic cross-sectional views showing the positions where the gates are dropped, and FIG. A schematic cross-sectional view showing the state in which the other side plate is placed on the plate, FIG. 6 is a plan view showing the gate position of the tape reel component molded in the example, and FIG. 7 shows the shape accuracy of the tape reel component. Figure 8 is a plan view of a tape reel component molded by a conventional mold; Figure 9 is a sectional view taken along the line A-^° of Figure 9; Figure 10 is a diagram showing the measurement points of the test. FIG. 11 is a plan view showing an example of a conventional gate position; FIG. 12 is a plan view of a tape reel component according to another embodiment of the present invention. be. l...Side plate 2...Cylinder 3...Reinforcement rib 4...Tape winding core 5...Top plate 5''...Concavity 6...Central boss 7...Boss for caulking

Claims (1)

[Scope of Claims] 1. A tape reel side plate, a cylinder with a lid arranged to have an open end at the center of the side plate, a tape winding core on the outer periphery of the cylinder with a lid, and a top plate of the cylinder with a lid. When injection molding a tape reel component consisting of a protrusion that serves as the center of rotation and a plurality of bosses for caulking, etc., the gate part is connected between the center of the tape reel and both ends of the attachment point of the toe piece of the core. Within the area surrounded by the inner cylinder extension line connecting the inner cylinder and the outer circumference of the inner cylinder (
1 and 2), and injecting resin from the gate portion to form the tape reel. 2. The method for manufacturing a tape reel according to claim 1, wherein the tape reel side plate has a through hole. 3. The method for manufacturing a tape reel according to claim 1 or 2, wherein the tape reel side plate is formed of radial ribs and outer circumferential ribs in the radial direction.