JP3027121B2 - Guide roller for tape cartridge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guide roller for a tape cartridge formed of a polyolefin resin.

[0002]

2. Description of the Related Art In a tape cartridge such as a video tape, an audio tape, a digital tape, and a cleaning tape, it is essential to provide a guide roller in a tape running path. FIG. 1 is an exploded perspective view of a conventional VHS type video tape cartridge.
The front lid 2 is pivotally mounted on the front surface of a case in which the lower half 7 is vertically assembled, and a pair of reels 3 and 3 are provided inside the case. Tape wound around these is transferred from one reel to the other reel. At the time of winding, a guide roller 4 is provided at one or more locations on the tape running path. 5 is a front lid lock mechanism, 6
Is a reel brake mechanism.

As a material for the guide roller 4, a polyacetal resin (POM) has been used in many cases. This material is mainly made of formaldehyde, and when the resin is heated to a high temperature during molding, the resin is decomposed to generate gas. Due to the influence of this gas, the adhesion between the resin and the mold surface is hindered, and the surface properties and transferability of the molded product (accurate transfer of the mold surface) are reduced, and the shape accuracy is reduced. Also had a problem with tape running. Also, when the amount of generated gas is large, discoloration and tape deterioration (generation of rust, etc.) may occur in a tape or the like using metal powder even when the tape cartridge is stored at a high temperature. On the other hand, although the polyolefin-based material has no problem due to the generation of gas, for example, even if the guide roller is formed using a conventional general-purpose polypropylene (PP) material, the melt flow is as low as 5 g / 10 min. Therefore, it takes time to fill the resin, and the molded product is solidified in an incompletely filled state, resulting in a defective product shape. Further, the conventional general-purpose polypropylene material has a large tensile elongation at break of, for example, 200%, so that the gate break after molding is poor, and a protruding gate residue occurs on the product, so that the product requires secondary processing of the gate treatment. became. Therefore, the guide roller made of polyolefin was not practical.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to form a guide roller for a tape cartridge which does not generate gas at the time of molding, has good moldability, and has good shape accuracy.

[0005]

In order to solve the above-mentioned problems, the present invention provides a tape cartridge using a material having a melt index of 10 to 30 g / 10 min and a tensile breaking elongation of 100% or less among polyolefin resins. To form a guide roller.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A polyolefin resin is used as a resin material employed in the present invention. By selecting a resin of this type which does not generate gas and has a specific melt index and tensile elongation at break, resin flow is improved and gate breakage is improved. In particular, polyolefins suitable for the purpose of the present invention are polyethylene resins and polypropylene resins, with polypropylene resins being particularly preferred.

The required characteristics of the polyolefin resin are materials having a melt index (MI) of 10 to 30 g / 10 min and a tensile elongation at break of 100% or less.
MI is JI as a test method for testing these characteristics.
SK7210, JIS K711 for elongation at break
It is preferable to conform to the method described in JIS standard as No. 3. For this product, since the development of molding cycle up (shortening of molding time per molding) can be considered and considered, the tensile elongation at break is particularly 50%.
The following are preferred. The MI value is about 10
If it is less than g / min, the resin flow tends to be poor, and the shape of the molded product is not stable. On the other hand, if it exceeds about 30 g / min, the resin flow tends to be too good, and burrs tend to be formed on the molded product. On the other hand, the tensile elongation at break was approximately 1
If it is more than 00%, there is a tendency that a problem that the cut of the gate becomes poor tends to occur.

A resin material satisfying the above characteristics was actually molded, and the results are shown in Table 1 in comparison with a conventional resin. As far as the inventor knows, there is no resin that satisfies the requirements of the present invention among the commercially available polyethylene and polypropylene resins. The resins used in the examples of the present invention were prepared by changing the resin production conditions.

[0009]

【Example】

Examples and Comparative Examples Polypropylene resin having a melt index of about 10 g / 10 min and a tensile elongation at break of about 100% (PP of the present application)
A guide roller indicated by 4 in FIG. 1 was manufactured from polyethylene and polyethylene (PE of the present application). For comparison, guide rollers having the same dimensions were manufactured using POM and a general-purpose polypropylene resin (general PP). When various characteristics were measured, the results shown in Table 1 were obtained. The evaluations in the table are as follows. 1. Gas ○ Generated, × No generated 2. Moldability Indicates moldability under normal molding conditions. ○ good, △ resin flow somewhat bad Transferability Whether or not the mold surface is accurately transferred to the guide roller. When the gas is generated, the transfer is inhibited and irregularities are formed. ○ good, △ somewhat poor ４. Out of gate Indicates whether the remaining gate of the product becomes longer. ○ short × too long and bad 5. Shape accuracy ○ Good roundness × Poor roundness High-temperature preservability A rust was observed using a metal tape as a magnetic tape at a temperature of 40 ° C. and a relative humidity of 80%. ○ No effect, × rusting Running torque The running load was measured with a VTR device. ○ Small, ◎ Very small

[0010]

[Table 1]

As shown in Table 1, the PP material of the present invention has no bad smell, has good moldability and transferability, and has good reliability as a product. As for the running torque, since the specific gravity of the PP material is 35% lighter than that of the POM material, the load on the tape when the cartridge is inserted into the VTR and played or rewound is smaller than that of the POM material. The reliability of the VTR is also improved. In addition, although this experiment was a test result using a PP material, a similar result was obtained with a test result using a PE resin. It should be noted that the general PP material is not preferable because it has poor fluidity and gate breakage, and is not considered as a product to be evaluated when inserted into an actual tape cartridge.

[0012]

According to the present invention, a guide roller for a tape cartridge is formed from a polyolefin resin having a melt index of 10 to 30 g / 10 min and a tensile elongation at break of 100% or less. Occasionally no gas is generated, good molding with broken gates is possible, and products with improved shape accuracy can be obtained.As a result, they do not react with magnetic tape even at high temperature storage,
Since no gas is generated and the specific gravity is smaller than that of polyacetal, the rotation load is reduced and the torque is also reduced. As described above, it is possible to provide a guide roller which is excellent in formability and shape accuracy and has high reliability even for tape.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a general video tape cartridge.

[Explanation of symbols]

 1: Upper half 2: Front lid 3: Reel 4: Guide roller 5: Front lid lock mechanism 6: Reel brake mechanism 7: Lower half

Claims (2)

(57) [Claims] 1. A polyolefin resin having a melt index of 10 to 30 g / 10 min and a tensile breaking elongation of 1
A guide roller for a tape cartridge formed from a material of not more than 00%. 2. The guide roller for a tape cartridge according to claim 1, wherein the polyolefin resin is selected from polyethylene and polypropylene.