JPS649175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reel used for winding magnetic tape in recording cassettes and video cassettes equipped with magnetic tape, and its main purpose is to wind the magnetic tape uniformly and without unevenness. The purpose is to do so.

Conventional recording cassettes and video cassettes (hereinafter abbreviated as cassettes) have tape winding reels (also called take-up rollers or take-up hubs) supported on the left and right inside a cassette case C, as shown in FIG.
The ends of the magnetic tape T are respectively locked on both reels, and the tape is fed out from one reel to the front of the case and guided by a guide roller R so that it can be wound onto the other reel. A tape winding reel used for a recording cassette has six hub pawls 15 protruding from the inner peripheral surface of the peripheral wall 2 at equal intervals as shown in FIG. An axial clamp groove 18 is formed on the outer periphery, and an elastically deformable clamp piece is press-fitted into the clamp groove to sandwich the end of the tape, thereby locking the end of the tape. These reels require molding precision that does not adversely affect the tape, but the reels are integrally injection molded from a heat-shrinkable synthetic resin material, even though the wall thickness is not constant in the radial direction as mentioned above. ing. As a result, as shown in FIG. 5(b), the reel's outer circumferential surface is deformed by heat shrinkage, causing a depression 7 due to a so-called sink mark, resulting in the outer circumferential surface of the reel becoming drum-shaped, with the center being more concave than both ends. When the tape is wound with the reel's outer circumferential surface being concave in the shape of a drum as described above, the tape is wound overlapping the reel's outer circumferential surface. Wrinkles occur on the tape, and these wrinkles have a negative effect on sound quality and images, and cause problems in running and winding the tape. In order to prevent this, the outer circumferential surface of the tape reel must be finished after being molded to improve the roundness, especially the perpendicularity, of the reel outer circumferential surface.

Therefore, this invention was developed by researching whether it is possible to prevent dents from occurring on the outer circumferential surface of the tape reel even if it is made of a synthetic resin material. He discovered that a reel with good roundness and perpendicularity could be formed by using a two-layer structure surrounding the outer cylinder, and succeeded in alleviating the drawbacks of the conventional method.

Hereinafter, the structure of the tape reel according to the present invention will be explained with reference to drawings of a tape winding reel used in a recording cassette.An annular groove 6 is provided on the upper and lower inner circumferences of the inner cylinder 3, and the annular groove 6 forms a rib. 9, six hub pawls 15 are provided at equal intervals from the inner peripheral surface of the rib 9 toward the center, a bearing hole 5 is formed in the center of the reel 1, and a bearing hole 5 is formed on the outer periphery of the inner cylinder 3 in the axial direction. Parallel grooves 8 are provided, and the inner tube 3 is made into a male mold, and a thin outer tube 4 is later integrally molded with a substantially uniform thickness on the outer periphery of the inner tube 3. A clamp groove 18 is provided in the cylinder 4 to form a two-layered peripheral wall 2 consisting of an inner cylinder 3 and an outer cylinder 4, and the two-layered peripheral wall 2 is formed to have the same thickness t as the peripheral wall of a conventional reel. .

Since the thickness of the inner cylinder 3 formed first is not constant in the radial direction, a recess 7 due to a sink mark is formed on the outer circumferential surface 3a of the inner cylinder. This sink dent 7 is caused by sink marks 7 of 20 to 30 microns depending on the wall thickness deformation at the formation position of the rib 9, hub pawl 15, reinforcing wall 19, etc. where the inner cylinder 3 becomes thick. . However, in the present invention, the inner cylinder 3 that has the dent 7 due to the sink mark is made of a male type,
Since the outer cylinder 4 is later formed approximately uniformly on the outer circumference with a thickness of several millimeters, a part of the outer cylinder 4 is formed up to the inside of the recess 7 of the inner cylinder outer peripheral surface 3a. As a result, the dent 7 caused by the sink mark is formed on the outer cylinder outer circumferential surface 4a, which is the outer circumferential surface of the peripheral wall 2, by only 5 microns or less.

In other words, the smaller the change in wall thickness, the more dents caused by sink marks7
Utilizing the characteristic of synthetic resin that reduces
A depression 7 for sink marks is created on the outer peripheral surface 3a of the inner cylinder 3, and then a thin outer cylinder 4 having a substantially constant thickness is formed on the outer periphery of the inner cylinder 3, thereby forming a two-layered peripheral wall having a predetermined wall thickness. 2, almost no dents 7 due to sink marks occur on the outer cylinder outer circumferential surface 4a, which is the outer circumferential surface of the reel 1. Even if a dent 7 is formed on the outer circumferential surface 4a of the outer cylinder due to a sink mark, it will only occur by the amount corresponding to the change in the wall thickness of the outer cylinder 4, that is, the amount that has cut into the dent 7 on the outer circumferential surface 3a of the inner cylinder. The dent 7 due to sink marks is less than 3 microns, which is less than 1/10 of that of a single-layer structure. As a result, even when the tape T is wound by the reel of the present invention, wrinkles do not occur on both sides of the tape, and the tape can be wound evenly and without unevenness.

FIG. 1B shows a ring-shaped tape reel 1 in which several grooves 8 are provided at equal intervals on the outer periphery of an inner cylinder 3, and an outer cylinder 4 is later integrally formed on the outer periphery of the inner cylinder 3.

Figure 2B shows a tape reel 1 in which the outer cylinder 4 is formed slightly shorter than the inner cylinder 3, and the inner cylinder 3 slightly protrudes from both ends of the outer cylinder 4. Even if the gate G2 for forming the outer cylinder is connected and the gate mark M remains there, the gate mark M is prevented from protruding from the inner cylinder 3, and the gate mark M prevents the reel 1 from forming.
This is so that it does not interfere with the rotation of the.

Each tape reel 1 has a two-layered peripheral wall 2 formed by an inner cylinder 3 and an outer cylinder 4. Even if the welding is insufficient, a part of the outer cylinder 4 is formed so as to dig into the drum-shaped recess 7 caused by the sink mark formed on the inner cylinder outer circumferential surface 3a, and along the inner cylinder groove 8. Since the outer cylinder 4 is formed, the inner and outer cylinders 3 and 4 cannot be separated in the axial direction by the recess 7, but are locked in the rotational direction by the groove 8 and cannot rotate together. Furthermore, since the gate G1 can be connected to the rib 9 or the annular groove 6 during molding of the inner cylinder 3, the rib 9
Or, even if the gate mark M remains in the annular groove 6, the reel 1
It does not interfere with the rotation of the

The method for forming the tape reel 1 according to the present invention is to first form the inner tube 3 using an upper mold and a lower mold as shown on the left in FIG. Separate it together with the mold as shown on the left in Figure 11,
The lower mold supporting the inner cylinder 3 is rotated as shown on the right in FIG. 9 until it is directly below the upper mold for forming the outer cylinder. Next, inner cylinder 3
The outer cylinder 4 having a substantially uniform wall thickness is formed around the outer circumference of the inner cylinder 3 as shown on the right in FIG.
After secondary molding is performed to form a reel 1 consisting of a two-layered peripheral wall 2 in which an outer cylinder 4 is fused to the outer periphery of an inner cylinder 3, an upper mold and a lower mold for molding the outer cylinder are separated, and Remove the reel 1 from the upper mold or the lower mold as shown on the right in Figure 11, and move the lower mold from which the reel 1 was removed by turning it again to just below the upper mold for forming the inner cylinder as shown on the left in Figure 9. 1 is continuously molded.

Since the tape reel of the present invention has the above structure, it is preferable to form it by two-color molding or insert molding. Not only can the inner cylinder 3 be formed of a synthetic resin material that is strong against friction, but also the outer cylinder 4 can be formed of a synthetic resin material that has good contact with the tape T. Furthermore, the surrounding wall 2
It is also possible to make the peripheral wall 2 of the reel 1 colorful by forming either one of the inner cylinder 3 and the outer cylinder 4, which constitute the reel 1, in a colored color, or by forming both of them from synthetic resin materials of different colors. If the inner and outer tubes 3 and 4 are made in different colors, the design effect will be significantly improved compared to the case where the entire reel is made of a single color.

Therefore, since the tape reel of the present invention is formed with a two-layer peripheral wall consisting of an inner cylinder and an outer cylinder, the inner cylinder of the reel peripheral wall is formed of a synthetic resin material suitable for insertion of the drive shaft, and the reel is Not only can the outer cylinder of the peripheral wall be made of a synthetic resin material suitable for winding tape, but the inner and outer cylinders can be colored, or the inner and outer cylinders can be made of different colored synthetic resins to create a rotating reel. It is also possible to enhance the design effect by making the outer periphery colorful. Moreover, the outer circumferential surface of the inner cylinder is recessed mainly in the shape of a drum due to sink marks, and the grooves in the axial direction are formed on the outer circumference of the inner cylinder. Even if the outer cylinders are not sufficiently fused together, the inner and outer cylinders will not be able to separate in the axial direction due to sink marks, and will also be unable to rotate together due to the grooves in the axial direction. Furthermore, the outer cylinder is formed shorter than the inner cylinder, annular grooves are provided on the upper and lower inner peripheries of the inner cylinder, ribs are formed on the inner periphery, and a gate can be connected to the inner cylinder ribs and the upper surface of the outer cylinder. For example, even if gate marks remain, the tape reel of the present invention does not interfere with reel rotation or tape winding. This has a beneficial effect on improving tape recording, recording, and playback, and improving sound quality and image stability.

[Brief explanation of the drawing]

1A and 1B are plan views showing examples of the shape of the tape reel of the present invention, FIGS. 2A and 2B are vertical sectional views showing examples of the structure, FIG. 5A and 5B are a plan view and a longitudinal sectional view of a conventional reel, FIGS. 6A and 6B are a plan view and a longitudinal sectional view of a videotape reel, and FIG. 7 is a reel of the present invention. FIGS. 8A and 8B are enlarged sectional views of essential parts showing examples of forming the reel peripheral wall, FIGS. 9 to 11 are manufacturing process diagrams of the reel of the present invention, and FIG. 12 13 is a longitudinal sectional view thereof, and FIG. 14 is a longitudinal sectional view showing the conventional reel in use. DESCRIPTION OF SYMBOLS 1... Tape reel, 2... Peripheral wall, 3... Inner cylinder, 4... Outer cylinder, 3a, 4a... Outer peripheral surface, 5...
Bearing hole, 6... Annular groove, 7... Recess, 8... Concave groove, 9... Rib, 15... Hub pawl, 18... Clamp groove, 19... Reinforcement wall, C... Cassette, G
1, G2...gate, M...gate mark, R...guide roller, S...shaft, T...tape, t...peripheral wall thickness.

Claims (1)

[Claims] 1. The outer peripheral surface 3a of the inner cylinder 3 forms a drum-shaped depression 7,
A concave groove 8 parallel to the axial direction is provided on the outer periphery, and an outer cylinder 4 is integrally provided on the outer periphery of the inner cylinder, with the inner cylinder being a male type,
Forming a peripheral wall 2 with a two-layer structure consisting of an inner cylinder and an outer cylinder,
A magnetic tape reel in which the outer circumferential surface of the peripheral wall is made smooth within 5 microns, and the inner and outer tubes cannot be separated in the axial direction due to the recesses, and cannot rotate together due to the grooves. 2. The wall thickness of the inner cylinder 3 becomes thinner at the part where the groove 8 is formed, and the outer cylinder 4 is provided with a substantially uniform thickness around the outer periphery of the inner cylinder,
The magnetic tape reel according to claim 1, wherein a clamp groove 18 is formed in the outer cylinder on the outer periphery of the groove. 3 The outer cylinder 4 is shorter than the inner cylinder 3, annular grooves 6 are provided on the upper and lower inner circumferences of the inner cylinder, ribs 9 are formed by the annular grooves, and the inner cylinder 3 and the outer cylinder 4 are made of synthetic resins of different colors. A magnetic tape reel according to claim 1 or 2, which is formed of a material.