JPH0676533A - Tape cartridge and manufacture of tape guide roller used therefor - Google Patents

Abstract

PURPOSE:To improve molding and dimensional accuracy of the tape guide roller for a tape cartridge. CONSTITUTION:The tape guide roller 3 is constituted of three layers such as primarily molded inner/outer peripheral layers 3a 3b and secondarily molded intermediate layer 3c. On the primary molding, a projecting pin 11 of molding article is inserted in the space 9 which is provided on a metallic mold 10 corresponding to the cylindrical shape of tape guide roller 3, so as to form a gap 12 between the inner/outer peripheries of the pin 11 and the metallic mold 10, then a thermoplastic resin is pressurized and filled into the gap 12 to mold the inner/outer peripheral layers 3a, 3b of tape guide roller 3. On the secondary molding, the intermediate layer 3c is integrally molded between the inner/outer peripheral layers 3a, 3b by pressing and filling the thermoplastic resin into the space 16 formed in accordance with the extraction of pin 11, while extracting the projecting pin 11 of the molding article. After cooling and solidifying, the molded article of tape guide roller is thrust out from the metallic mold 10 by the pin 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape cartridge having a tape guide roller and a method for manufacturing the tape guide roller.

[0002]

2. Description of the Related Art As shown in FIGS. 6 and 7, a tape guide roller 3 of this type has a slight clearance on a metal or plastic roller support shaft 2 provided upright inside a main body 1 of a tape cartridge. In order to change the tape running path without damaging the tape or giving extra tension to the tape, the tape is rotated so that the tape (not shown) is fed while contacting the outer peripheral surface. It is used.

[0003]

However, when the tape guide roller 3 is a resin injection molded product, flow marks 5, irregularities due to air entrainment, or weld marks are generated near the gate 4 as shown in FIG. Often
Often a uniform surface is not obtained. Further, as shown in FIG. 9, the inner and outer circumferences may be curved in the thickness direction or locally deformed around the central portion 6 of the tape guide roller 3, and the straightness, cylindricity, and coaxiality of the inner and outer circumferences may be increased. At present, it is not possible to easily obtain high quality products. For this reason, the tape guide roller that is required to have high rotation accuracy and high rotation speed has insufficient accuracy, and as a practical phenomenon, a high rotation sound is generated due to vibration, and in the case of a video tape cartridge, time axis fluctuation (jitter). This was one of the causes of the deterioration of the characteristics.

Therefore, when the tape guide roller is a resin molded product due to its characteristics and desired accuracy cannot be obtained, it is unavoidable to use a costly machined product. The main cause of the problems in the above-mentioned tape guide roller resin molded product is that it is difficult to keep the temperature, density, pressure and solidification speed of the resin in the mold uniform during molding. . As a result, it is considered that the mold transfer property is deteriorated and the uneven shrinkage occurs, which leads to a decrease in accuracy. SUMMARY OF THE INVENTION An object of the present invention is to solve the shortage of dimensional accuracy of a molded product, which a conventional tape guide roller has, and to provide a tape cartridge provided with a highly accurate tape guide roller and a method of manufacturing the tape guide roller.

[0005]

A tape cartridge according to the present invention is made of a cylindrical thermoplastic resin which is rotatably inserted through a roller support shaft 2 provided upright in a main body case 1 as shown in the figure. The tape guide roller 3 is integrally formed between the inner and outer peripheral layers 3a and 3b and the inner and outer peripheral layers 3a and 3b which are primarily formed.
It is characterized in that the intermediate layer 3c is formed next. However, instead of primary molding both the inner peripheral layer 3a and the outer peripheral layer 3b, only one of the inner peripheral layer 3a and the outer peripheral layer 3b is primary molded, and the other is secondary molded to form a tape with only two layers of the inner and outer peripheral layers 3a and 3b. The guide roller 3 can also be configured. The inner and outer peripheral layers 3a and 3b have different surface roughnesses, and the outer peripheral layers 3b
The surface roughness of the inner peripheral layer 3a can be made rougher than that of the inner peripheral layer 3a. Further, it is possible to form fine lines 17 substantially parallel to the circumferential direction on the respective surfaces of the inner peripheral layer 3a and the outer peripheral layer 3b.

In the method of manufacturing the tape guide roller of the present invention, the space 9 corresponding to the cylindrical shape of the tape guide roller 3 is formed.
In the space 9 of the injection-molding die 10 having the above-mentioned structure, a cylindrical molded product projecting pin 11 having a diameter smaller than that of the space 9 is provided, and a gap 1 is formed between at least one of the inner and outer peripheries thereof and the mold 10.
2. A step of inserting and removing along a shaft core so as to form 2 and a thermoplastic resin that has been heated and melted is pressure-filled into the space 12 and the inner and outer peripheral layers 3a of the tape guide roller 3a.
A primary molding step of molding both or any one of 3b, and a thermoplastic resin in the space 16 formed with the pulling out of the pin 11 while pulling out the molded product protruding pin 11 after the primary molding. It is press-fitted to fill the intermediate layer 3c between the inner and outer layers 3a and 3b, or the inner and outer layers 3
It comprises a secondary molding step of integrally molding one of a and 3b with the other, and a step of projecting the tape guide roller molded product from the mold 10 by the molded product projecting pin 11 after cooling and solidification.

[0007]

[Function] The thick section of the tape guide roller 3 is
Inner and outer peripheral layers 3a and 3b formed by filling the two stages of secondary molding and secondary molding with different filling times.
And when it is composed of three layers of the intermediate layer 3c or two layers of the inner and outer peripheral layers 3a and 3b, each layer (3a, 3b or comb 3c) can be thinned, and the resin amount at each resin injection step is small. Therefore, the temperature, pressure, density, etc. of the resin are made uniform,
Molding accuracy and dimensional accuracy can be improved, and a skin layer having a high degree of transfer can be formed especially on the inner and outer peripheral portions that require surface properties.

The inner peripheral layer 3a has a fine surface roughness, and the outer peripheral layer 3 has
By making the surface roughness b of the inner peripheral layer 3a rougher than that of the inner peripheral layer 3a, the frictional resistance between the inner peripheral layer 3a and the roller support shaft 2 can be reduced, and the tape can follow the outer peripheral layer 3b well. On the respective surfaces of the inner peripheral layer 3a and the outer peripheral layer 3b,
By forming fine lines 17 which are substantially parallel to the circumferential direction, it is possible to suppress the deviation and vibration of the tape on the outer peripheral layer 3b in the roller axis direction without hindering the rotation of the tape guide roller 3. .

When the resin is injected, first, the space 16 of the tape guide roller 3 to be secondarily molded is projected from the molded product, and the pin 1 is formed.
1 is filled and both or one of the inner and outer peripheral layers 3a and 3b of the roller 3 is first filled, solidified and primary molded,
Next, while pulling out the molded product protruding pin 11,
Resin is injected into the secondary molding space 16 formed by pulling out 1 to perform secondary molding. Therefore, since the skin layer having a high degree of transfer can be formed on the inner and outer peripheral portions requiring the surface property by the primary molding and the amount of the resin is reduced, the temperature of the resin is
The pressure and density are made uniform. In the secondary molding, the secondary molding space 16 is injected while the molded product is projected and the pin 11 is pulled out, so that a suction effect is generated, the resin inflow is made extremely smooth, and every corner of the space 16 is uniformly filled. As a result, a homogeneous layer is formed. As a result, compared with the conventional general molding method in which resin is simply injected all at once into the space of the mold,
The molding accuracy is remarkably improved, and dimensional accuracy that has never been achieved can be realized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In FIG. 1, reference numeral 1 is a main body case of a tape cartridge for video or the like. Reference numeral 2 denotes a roller support shaft that is erected in the body case 1. A tape guide roller 3 is rotatably inserted into and supported by the roller support shaft 2, and its outer peripheral surface is brought into frictional contact with a tape (not shown) such as a magnetic tape to rotate around the roller support shaft 2. The tape guide roller 3 is
As shown in FIG. 4, it is a thermoplastic resin injection-molded product formed in a cylindrical shape, and is composed of three layers in a concentric shape when viewed from the end face side thereof, and an intermediate layer between the inner and outer peripheral layers 3a and 3b in a longitudinal section. 3c is sandwiched. The roller 3 has a total length of about 17 mm and an inner diameter of about 2.5 mm,
The outer diameter is about 5 mm. The thickness of each of the inner peripheral layer 3a and the outer peripheral layer 3b is about 0.2 to 0.5 mm.

FIG. 2 shows a forming process of the tape guide roller 3. First, FIG. 2A shows a state in which a die 10 for injection molding having a space 9 corresponding to the cylindrical shape of the tape guide roller 3 is clamped. At this time, in the normal molding, the cylindrical molded product projecting pin 11 which is located outside the molded product space is provided with the outer circumference and the inner circumference thereof, the mold 10, and the mold 1.
0a (core pin) so as to form a slight gap 12 corresponding to the thickness of the inner peripheral layer 3a and the outer peripheral layer 3b of the tape guide roller 3, and the tip of the molded product protruding pin 11 and the gate 13 side. It is inserted so as to form a space 14 for resin injection between and.

Under this condition, as shown in FIG. 2B, a thermoplastic resin 15 (for example, polyacetal) that has been heated and melted is pressure-injected from the gate 13 to perform primary molding. Then, the resin 15 hits the tip of the molded product protruding pin 11 and diffuses, rapidly flows into even a few voids 12 and rapidly solidifies at the same time when it contacts the mold 10, but since the voids 12 are narrow, they are hardened. The variation in cooling is unlikely to occur, and the portion in contact with the die 10 on the outer peripheral side and the die (core pin) 10a on the inner peripheral side has an extremely uniform density and an inner peripheral layer 3a of the tape guide roller 3 having very good transferability. The outer peripheral layer 3b is molded.

Next, as shown in FIG. 1C, the thermoplastic resin 15 is pulled out from the lower portion 13a of the gate 13 which is still in a molten state while the protruding pin 11 of the molded product is rapidly retracted. By filling the space 16 formed between the inner and outer peripheral layers 3a and 3b with pressure, the intermediate layer 3c is integrally secondary-molded between the inner and outer peripheral layers 3a and 3b. At this time, there is a pressure reducing effect by pulling out the molded product projecting pin 11, and there is no overheating of the resin temperature due to compression of air in the molded product space as in the conventional case or high pressure, and burning. The resin is extremely smoothly and uniformly filled in every corner of the space 16. Also, this 2
Inner / outer peripheral layer 3 primarily formed by the intermediate layer 3c that is next formed
The a / 3b is pressed from the inside, and the molds 10 and 10a are more closely adhered to each other, and the intermediate layer 3c firmly supports the inner / outer peripheral layers 3a and 3b from the inside.

In this way, as shown in FIG. 3D, the filling of the secondary molding resin is completed, and the resin is completely cooled and solidified. Conventionally, at this time, since the cooling speed of the tape guide roller molded product near the mold and the central part were significantly different, distortion during cooling was likely to occur, which caused bending and sink marks. In the example, the inner and outer peripheral layers 3 that were primary molded
Since a and 3b play a role as a kind of heat insulating layer and the intermediate layer 3c is cooled without directly contacting the molds 10 and 10a, there is less variation in cooling, which is advantageous for solving the above-mentioned problems.

When the cooling is completed, the mold 10 is opened as shown in FIG. 7E, and the tape guide roller molded product is projected from the mold 10 by the retracted molded product projecting pin 11 for molding. finish. Normally, the molded product projecting pin 11 is retracted before the next mold clamping, but here, the molded product projecting pin 11 is positioned in the state of FIG. . Further, in order to improve the smoothness of friction and rotation with the tape, the surface roughness of the inner peripheral layer 3a is made smaller than 1 μmRz to reduce the frictional resistance with the roller support shaft 2, while the outer peripheral layer 3b is applied to the tape. In order to improve the followability, the surface roughness was made rougher than that of the inner peripheral layer 3a to be 1 μmRz or more.

Further, in order to suppress the displacement and vibration of the tape in the axial direction of the tape guide roller, the surface roughness is set by forming fine lines 17 in the circumferential direction as shown in FIG. The position of the tape can now be regulated so that it does not hinder the operation. The setting of these surface states can also be realized more accurately by improving the transferability to the mold by the above-mentioned molding method. According to the actual results, the straightness, cylindricity, and coaxiality of the tape guide roller in the axial direction have been improved to about half that of conventional products.
A surface roughness of 1 μm or less was obtained.

In this embodiment, as described above, the inner diameter is about 2.5.
mm, the outer diameter is about 5 mm and the total length is about 17 mm. The target thickness of the inner peripheral layer 3a and the outer peripheral layer 3a is 0.2-0.5 mm. By the thickness of the inner and outer peripheral layers 3a and 3b and the intermediate layer 3c,
The ratio may be set appropriately in consideration of its effect.

In the above embodiment, the inner peripheral layer 3a and the outer peripheral layer 3b were both primary-molded and the intermediate layer 3c was secondary-molded. Instead of this, as shown in FIG. 5 (A) or (B), It is also possible to perform primary molding only for the outer peripheral layer 3b or the inner peripheral layer 3a on the side that requires higher precision than either of them, and to perform secondary molding for the other. In this case, the thick section of the tape guide roller 3 is composed of only two layers of the inner and outer peripheral layers 3a and 3b, and there is no intermediate layer 3c.

[0019]

EFFECTS OF THE INVENTION According to the present invention, the thermoplastic resin can be uniformly and smoothly flowed, filled and cooled by filling the thermoplastic resin in two stages of primary molding and secondary molding at different times. It is possible to easily obtain the tape guide roller 3 having excellent properties and molding accuracy. As a means for varying the filling time, the molded product projecting pin 11 of the molding die 10 is formed in a cylindrical shape and used, so that the molding apparatus is simplified and the resin inflow during the secondary molding is extremely smooth. Since the space 16 is evenly filled in every corner, a uniform layer is formed. In this respect as well, it is possible to contribute to improvement in dimensional accuracy and molding accuracy. By extension, the tape guide roller 3
The rotational accuracy and the rotational noise are significantly improved as compared with the conventional products, and the highly accurate tape guide roller 3 can be obtained at low cost without using a high-cost cutting roller.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a tape cartridge.

FIG. 2 is a process drawing of a tape guide roller.

FIG. 3 is a cross-sectional view taken along line XX in FIG.

FIG. 4 is a perspective view showing a partially broken tape guide roller.

FIG. 5 is a perspective view showing a tape guide roller according to another embodiment in a partially broken state.

FIG. 6 is a sectional view showing a conventional tape guide roller in a semi-cut state.

7 is a sectional view taken along line YY in FIG.

FIG. 8 is an external front view showing a defective molding state of a conventional tape guide roller.

FIG. 9 is a cross-sectional view showing a defective molding state of a conventional tape guide roller.

[Explanation of symbols]

 1 Main body case 2 Roller support shaft 3 Tape guide roller 9 Space 10 Mold 11 Molded product protruding pin 12 Void 17 Streak

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsunobu Suzuishi Wataru-cho, Watari-gun, Miyagi Prefecture Aikuma Tazawa character, 42-2 Shinmei Co., Ltd. Toshin Seiko Co., Ltd. Shinmei 42-2 Toshin Seiko Co., Ltd.

Claims (6)

[Claims] 1. A cylindrical tape guide roller 3 made of a thermoplastic resin, which is rotatably inserted into a roller support shaft 2 in a main body case 1, and inner and outer peripheral layers 3a and 3b formed by primary molding,
An intermediate layer 3 integrally secondary-molded between the inner and outer layers 3a and 3b
A tape cartridge composed of c. 2. An inner peripheral layer 3a and an inner peripheral layer 3 in which a cylindrical thermoplastic resin tape guide roller 3 rotatably inserted in a roller support shaft 2 in a main body case 1 is primary molded.
A tape cartridge comprising an outer peripheral layer 3b integrally formed on the outer periphery of a. 3. An outer peripheral layer 3b in which a cylindrical thermoplastic resin tape guide roller 3 rotatably inserted through a roller support shaft 2 in a main body case 1 is formed, and an outer peripheral layer 3 is formed.
A tape cartridge constituted by an inner peripheral layer 3a which is secondarily formed integrally with the inner periphery of b. 4. The tape cartridge according to claim 1, wherein the surface roughness of the outer peripheral layer 3b is made rougher than that of the inner peripheral layer 3a. 5. The tape cartridge according to claim 1, wherein the inner peripheral layer 3a and the outer peripheral layer 3b each have fine lines 17 formed substantially parallel to the circumferential direction on their respective surfaces. 6. The space 9 of a mold 10 for injection molding having a space 9 corresponding to the cylindrical shape of the tape guide roller 3.
A molded product projecting pin 11 having a cylindrical shape smaller than the diameter of the space 9 is removably inserted along the shaft core so as to form a gap 12 between at least one of the inner and outer peripheries thereof and the mold 10. A primary molding step in which a thermoplastic resin that has been heated and melted is pressure-filled into the voids 12 to mold both or one of the inner and outer peripheral layers 3a and 3b of the tape guide roller 3; A space 16 formed by pulling out the pin 11 while pulling out the pin 11 for ejecting the molded product later.
The inner and outer peripheral layers 3a
Intermediate layer 3c between 3b or inner / outer layer 3a / 3b
A secondary molding step of integrally molding one of the two with the other, and a step of projecting the tape guide roller molded product from the mold 10 with the molded product projecting pin 11 after cooling and solidifying.
Tape guide roller manufacturing method.