JPS6336546Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is attached to the back side of a magnetic tape stretched in a position facing the playback head of the full opening of the tape cassette, and is used for motors, transformers, etc. of magnetic recording and playback devices. The present invention relates to an improvement in the structure of a magnetic shielding plate that prevents stray magnetic fields generated by a magnetic head from being reproduced through a reproduction head and increasing the level of reproduction noise.

Background Art and Problems The magnetic shielding plate used in this tape cassette is made of about 70 to 80% by weight of nickel, a small amount of special ingredients, and the balance is iron, which is so-called 78% permalloy or about 40 to 50% by weight. Metal materials such as so-called 45% permalloy, which is made of nickel, a small amount of special ingredients, and the balance iron, are used. In manufacturing this magnetic shield plate, the metal material is cast, rolled, punched into a predetermined shape, and plastically worked at approximately 1000°C to remove processing strain and improve magnetic properties. Manufactured by annealing at a temperature of , and surface treatment such as nickel plating.

The magnetic shielding plate manufactured in this manner undergoes deformation as it passes through each processing step. In particular, in the heat treatment step (annealing step), if a material with a thickness of 0.6 mm or less is used, the plate will bend and deform, making it difficult to attach it to the narrow, designated position within the cassette half and causing the attachment state of the magnetic shielding plate to become unstable.

However, with the development of materials for magnetic shielding plates, sufficient magnetic shielding effects can be obtained even with thin walls.
It is necessary to make it relatively thin, about 0.4 to 0.6 mm, to reduce material costs.

For this reason, conventionally, as shown in FIG. 1, linear rib portions 6 that fit into the grooves 7 of the cassette case body 1 are provided on opposing side edges of the magnetic shielding plate 4 so as to protrude along the longitudinal direction. Even if the wall thickness is thin, deformation such as curvature due to heat treatment is prevented, and the magnetic shielding plate 4 can always be stably fitted into the groove 7.

However, in the case of such a configuration, in order to provide the rib portions 6 that protrude in the longitudinal direction on both side edges of the magnetic shielding plate 4, the edge of the press die that cuts the material is used to punch out the magnetic shielding plate and plastically process the material at the same time. It is necessary to provide parallel protrusions along the vicinity of the die, which leads to disadvantages in press processing such as poor precision during punching and stress concentration on these protrusions, shortening the life of the press die. It was hot.

Purpose of the invention The present invention solves the above-mentioned conventional drawbacks, and prevents deformation that occurs during the manufacturing process of magnetic shielding plates by providing ribs with a structure that can be pressed without any disadvantage to the main body of the magnetic shielding plate. It is an object of the present invention to facilitate the work of attaching a magnetic shielding plate to a predetermined position of a cassette half, and to stabilize the attachment state of the magnetic shielding plate.

Summary of the invention For this reason, the present invention provides two diagonal ribs in the form of intersecting grooves extending diagonally on the surface of the magnetic shielding plate body to prevent the magnetic shielding plate from curving, and to prevent the magnetic shielding plate from curving and to A vertical rib is provided that is open near the side edge of the magnetic shield plate body and is bent and extended in a direction substantially perpendicular to the side edge, and each extension line of both side edges of the diagonal rib is provided. is formed so as to intersect with the side edges of the vertical ribs, and the strength of the magnetic shielding plate is improved to prevent deformation at the ribs and other parts consisting of the diagonal ribs and the vertical ribs.

Embodiments Embodiments of the present invention will be described below with reference to FIGS. 2 to 4.

FIG. 2 is a plan view of the tape cassette according to the present invention with the upper cassette half removed, and the lower cassette half 11 is a magnetic tape.

This magnetic tape 11 is stretched over the entire opening 12 of the tape cassette, and between the two small pillars 13 on the back side, the side wall 14 of the opening 12 and the screw-fastening column 15. A plate-shaped spring 16 and a magnetic shielding plate 17 having felt for resiliently supporting the magnetic tape from the back surface are arranged at predetermined positions.

This magnetic shielding plate 17 is a thin plate with a U-shaped cross section, and the plate-shaped springs 16 are attached at both hook-shaped ends.
is pressed against and supported by the small pillar 13, and the back surface of the magnetic shielding plate 17 is brought into contact with and supported by the screw-fastening pillar 15. In this way, the magnetic shielding plate 17 is housed in a predetermined position in the opening on the entire surface, so if the magnetic shielding plate 17 is bent or otherwise deformed, the lower cassette half 10 may be damaged during the manufacturing process of the cassette tape. This makes it difficult to mechanically drop and assemble the magnetic shielding plate 17 into a predetermined position. Therefore, the shape of the magnetic shielding plate 17 must be exactly as specified.

For this reason, the magnetic shielding plate 17 of the present invention is provided with diagonal ribs 18 as shown in FIGS. 3 and 4 to improve the strength of the magnetic shielding plate 17.

The diagonal ribs 18 are provided on the surface of the rectangular flat plate portion of the magnetic shielding plate main body 17, and are comprised of two intersecting small U-shaped grooves extending in the diagonal direction of the rectangular flat plate portion.

In order to prevent the magnetic shielding plate 17 from being deformed along the diagonal ribs 18, the vicinity of each open end on the side edge of the magnetic shielding plate body at both ends of this diagonal rib 18 is Each side edge is provided with a vertical rib 19 bent vertically.

As shown in FIG.
In order to configure the structure such that it always crosses the side edge 21 of the vertical rib 19 without directly intersecting the side edge of the flat plate portion of the magnetic shielding plate 17, the intersection of the extension line 20 and the side edge 21 and the side edge 21 of the magnetic shielding plate 17 are It shall be constructed such that the distance n from the circumferential edge thereof is equal to or greater than a predetermined amount.

By configuring in this way, the magnetic shielding plate 17
Not only does it not deform in the vertical or horizontal direction, but the force that causes it to bend along the diagonal ribs 18 is applied to the vertical ribs 19.
Since this is prevented by the structural steel of the U-shaped groove, deformation of the magnetic shield plate 17 does not occur.

Note that if the vertical ribs 19 are provided on the magnetic shielding plate main body 17 as shown by the dashed line 22, the distance h on the side edge 21 will become zero and the effect of preventing the magnetic shielding plate 17 from deforming will be lost. , at least the side edge 21
The upper distance h must be greater than a necessary predetermined amount.

The magnetic shielding plate 17 provided with ribs consisting of the diagonal ribs 18 and the vertical ribs 19 as described above is arranged along the stepped portion 23 provided at a predetermined position of the lower cassette half 10, as shown in FIG. Small pillars that do not
It is supported by a screw-fastening column and installed inside a tape cassette.

Effects of the invention As detailed above, according to the invention, even if the magnetic shielding plate is thin in order to save materials, the magnetic shielding plate is provided with ribs consisting of diagonal ribs and vertical ribs to improve its strength, so heat treatment etc. It will not be deformed during the processing and manufacturing stage. Therefore, there is no problem with the work of attaching the magnetic shielding plate to the cassette half, so that the magnetic shielding plate can be made thinner and the material used can be saved.

Furthermore, when pressing the magnetic shielding plate, since the ribs are mainly located in the center of the magnetic shielding plate, there is no risk of damaging the press mold.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional magnetic shielding plate attached to a tape cassette, Fig. 2 is a plan view showing a state in which the upper cassette half of the tape cassette equipped with the magnetic shielding plate of the present invention is removed, and Fig. 3 4 is an enlarged perspective view showing a portion of the magnetic shield plate extracted, and FIG. 4 is an enlarged front view of the magnetic shield plate. 17 is a magnetic shielding plate, 18 is a diagonal rib, and 19 is a vertical rib.

Claims (1)

[Scope of utility model registration request] A groove-shaped rib extending substantially diagonally on the surface of the magnetic shielding plate main body having a substantially rectangular shape, the rib including a diagonal rib extending close to the side edge of the magnetic shielding plate main body; Continuing with these diagonal ribs at both ends, the vertical ribs are open at the side edges of the magnetic shielding plate body and extend in a direction substantially perpendicular to the side edges, and each side of the diagonal ribs A magnetic shielding plate of a tape cassette, wherein each extension line of the edge is formed so as to intersect with the side edge of the vertical rib.