JPH04222979A - Hub for tape cassette - Google Patents

Abstract

PURPOSE:To offer a tape cassette hub having large peeling strength by two-color molding CONSTITUTION:In the two-color molding process of a hub 1 of a tape cassette, an impact-resistant polystyrene resin is used instead of polyoxymethylene. In the peeling strength test under 150gf load for 32 samples, 8 hubs using polyoxymethylene are peeled while 2 hubs using impact-resistant polystyrene resin are peeled. This results in that the latter has high peeling strength. By adding silicon resin by 2.6-2.8%, sliding property can be maintained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape cassette hub suitable for application to, for example, an audio compact cassette hub.

0002

2. Description of the Related Art Conventionally, a tape cassette hub as shown in FIG. 1 has been proposed. This hub 1 is
They are arranged side by side at symmetrical positions on the left and right sides of the tape cassette so that the tape can be wound up. This hub 1 is
Drive shaft insertion hole 1c, drive teeth 1d, boss 1e, arm 1
f, a clamp piece fitting portion 1g, a side surface 1j, a reel 1h, a sliding surface 1i, and a side surface 1j. The material of this hub 1 is polyoxymethylene (hereinafter referred to as "POM").
That's what it means. ) is used. When the hub 1 rotates during tape running, the sliding surface 1i rubs against a sheet installed in the tape cassette, but no oil or other lubricant is used on the interface. Therefore, it is natural that the material for the hub 1 should preferably have a coefficient of friction as small as possible. In this respect, POM is optimal as a material for the hub 1 because it has a small coefficient of friction and has elasticity. On the other hand, as shown in Fig. 1, this hub 1 has a colored part (
Hereinafter, it will be referred to as "primary side part 1a". ) and a part that remains white without being colored (hereinafter referred to as the "secondary side part 1b").The manufacturing method for this is to first use POM mixed with different pigments. The primary side part 1a is molded with a mold, and then the secondary side part 1b is molded using another mold while being welded to the primary side part 1a, which is a two-color molding method. The reason why two-color molding is performed in this way is due to design requirements.

0003

[Problems to be Solved by the Invention] However, as mentioned above, two-color molding involves two-step molding, and secondary molding is performed after the primary molding is finished and the temperature of the material has cooled down to a certain extent. Because of this, the temperatures of the primary side part 1a and the secondary side part 1b are different during the molding stage of the secondary side part 1b, and when both of them cool down to room temperature, there is naturally a difference in shrinkage rate, and the Residual strain occurs at the interface. Further, when welding the two, one is in a fluid state while the other is in a solidified state, so the welding strength is smaller than when both are in a fluid state. Therefore, in the case of two-color molding, the strength of the welding between the two becomes a problem. In a two-color molded hub using POM as a material,
The welding strength between the primary side part 1a and the secondary side part 1b was low, and it was observed that the primary side part 1a and the secondary side part 1b often peeled off, as shown in FIG. 2, especially when subjected to impact. In view of these points, it is an object of the present invention to provide a two-color molded hub 1 with high peel strength.

0004

[Means for Solving the Problems] The hub of the tape cassette according to the present invention is, for example, as shown in FIG. be.

[0005]

[Operation] According to the present invention, by using HI-PS as the material in the two-color molding of the hub 1, it is possible to increase the welding strength between the primary side portion 1a and the secondary side portion 1b of the two-color molded hub 1. can.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the hub of the tape cassette of the present invention will be described below. Hubs 1 are arranged side by side at symmetrical positions on the tape cassette so that the tape can be wound up. As shown in FIG. 1, this hub 1 has a substantially disk-like shape, and has a drive shaft insertion hole 1c in the center, into which a drive shaft for tape running is inserted. Six teeth 1d are provided inside the drive shaft insertion hole 1c, and when the drive shaft enters the drive shaft insertion hole 1c, six axially extending convex portions provided on the drive shaft are formed. enters between these teeth and transfers the torque generated on the drive shaft to this hub 1.
The information is transmitted to the boss 1e. Drive shaft insertion hole 1
There is a boss 1e on the outside of the boss 1e, which supports the driving tooth 1d inside the boss 1e and transmits the torque from this tooth to the arm 1f. Two arms 1f are provided between the boss 1e and a reel 1h, which will be described later, to transmit the torque of the boss 1e to the reel 1h. A notch serving as a clamp piece fitting part 1g is provided in a part of the reel 1h, and one end of the leader tape is sandwiched and fixed so that it cannot be removed. This clamp piece fitting portion 1g is narrower on the inside of the hub 1 than on the outside to prevent the clamp piece from coming off. In addition to the arm 1f, a thin plate-shaped side surface 1j is provided between the boss 1e and the reel 1h, so that the circular shape of the reel 1h can be maintained. Reel 1 is placed on the outermost circumference of hub 1.
A reel 1h is provided on which the tape is wound. Sliding surface 1 on the side of reel 1h
i is designed to rub against a sheet installed in the tape cassette when the hub 1 rotates.

As shown in FIG. 1, this hub 1 is molded in two colors, and the colored primary side 1a has drive teeth 1d.
, boss 1e, and arm 1f. In addition, the uncolored secondary side 1b has a side surface 1j and a reel 1h.
It is included. The method for manufacturing the hub 1 is to first mold the primary side part 1a using a mold using a synthetic resin mixed with different pigments, and then mold the secondary side part 1b using another mold to form the primary side part 1a. It is molded using a two-color mold, which involves welding and molding. The reason why two-color molding is performed in this way is due to design requirements.

As the material for this hub 1, it was decided to use HI-PS, which has strong welding strength even when two-color molding is performed. Table 1 shows the impact on the primary side 1a and secondary side 1b of the hub 1 when the hub 1 is manufactured using this HI-PS.
This figure shows the results of measuring the magnitude of peel strength with.

[Table 1] The leftmost vertical column in Table 1 shows the load for generating impact force, which is 50, 100, and 1, respectively.
The impact force is gradually increased to 50gf. As shown in FIG. 1, the impact force P is applied to the hub 1 in the vertical direction. The next vertical column on the right shows the drop height of the load, which is set to the same height of 19 cm under each test condition. The next vertical column shows the measurement results when Hub 1 was manufactured using POM, the number in the denominator shows the number of samples measured, and the number in the numerator shows the number of samples peeled off due to impact out of the number measured. This indicates the number of pieces. As shown in Table 1, 32 samples were used for each measurement, and there was no peeling when the loads were 50 gf and 100 gf. On the other hand, when the load was 150 gf, 8 out of 32 samples peeled off. In other words, one out of four samples peeled off, and this result shows a high result of 25% peeling off. On the other hand, the material is HI-PS
The results when changing to are shown in the rightmost column. The measurement conditions are the same as for POM, and the measurement results are as follows.
At loads of 50 gf and 100 gf, the number of peeled pieces was 0, as in the case of POM, and no difference was observed between POM and HI-SP. However, at a load of 150 gf, the number of peeled pieces was very small, 2 out of 32 test samples. The number of peeled pieces is 2, which is 1/4 of the 8 pieces peeled off in the case of POM. Also, the percentage is about 6%, which is much smaller than POM's 25%. The results show that by changing the material of the hub 1 from POM to HI-PS, the peel strength due to impact is greatly improved. The reason for this is considered to be that the welding at the interface between the primary side portion 1a and the secondary side portion 1b of the hub 1 became stronger.

Another improvement achieved by changing the material is improved moldability in two-color molding. When POM is used as shown in Figure 3, P
Since the fluidity of OM rapidly increases at 220°C, it was extremely difficult to control the temperature to obtain the optimal fluidity for molding, whereas the fluidity of Hi-PS is Since it has the characteristic that it increases almost linearly as the temperature rises, it becomes easy to control the temperature optimally for molding.

On the other hand, as mentioned above, since the hub 1 does not use lubricant during rotation, it is required to have good sliding properties. However, HI-PS itself has a high coefficient of friction,
The sliding properties were inferior to POM. Therefore,
In order to improve the sliding properties of HI-PS, 2.6 to 2.8% of silicone resin was added. Adding silicone resin to Hi-PS improves sliding properties, but if too much is added, the peel strength of two-color molding decreases. This means that the original purpose cannot be achieved. Addition within this range can satisfactorily improve sliding properties without reducing peel strength.

As described above, in the two-color molding of the hub 1, by changing the material from POM to HI-PS, the welding strength between the primary side portion 1a and the secondary side portion 1b of the two-color molded hub 1 can be increased. Ta. Furthermore, since HI-PS is a cheaper resin than POM, it has become possible to reduce the cost of the product. It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations can be adopted without departing from the gist of the present invention.

0012

According to the present invention, by using HI-PS as the material in the two-color molding of the hub 1, the welding strength between the primary side portion 1a and the secondary side portion 1b of the two-color molded hub 1 is increased. There are profits that can be made.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a two-color molded hub.

FIG. 2 is an explanatory diagram showing a state of damage caused by impact on a two-color molded hub.

FIG. 3 is a conceptual diagram showing the influence of temperature on the fluidity of HI-PS and POM.

[Explanation of symbols]

1 Hub 1a Primary side part 1b Secondary side part 1c Drive shaft insertion hole 1d Drive tooth 1e Boss 1f arm 1g Clamp piece fitting part 1h reel 1i Sliding surface 1j Side P Impact force

Claims (1)

[Claims] 1. A hub for a tape cassette, characterized in that it is two-color molded using impact-resistant polystyrene resin.