JP2001266523A - Magnetic disk cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deformation of a shutter member when performing open movement of the shutter member in a magnetic disk cartridge which has a U-shaped section, is formed of an upper face plate, a lower face plate and of a connecting part connecting both face plates and is provided with the shutter member having a shutter window part opened communicating from the connecting part to the upper and lower face-plate parts. SOLUTION: In the shutter member 5 having the shutter window part 54 opened communicating from the connecting part 53 to the upper and lower face-plate parts 51 and 52, a reinforcement part 56 extended in a direction parallel to the connecting part 53 is formed on a bottom part 59 of the shutter window part of at least one of the upper and lower face-plate parts 51 and 52. This reinforcement part 56 can be formed of a projected line projected in the vertical direction outside the cartridge case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk cartridge in which a disk-shaped magnetic disk medium is accommodated in a case, and more particularly to a shutter member used for the magnetic disk cartridge.

[0002]

2. Description of the Related Art Conventionally, magnetic layers are formed on both sides of a disk-shaped base made of a flexible polyester sheet or the like, and magnetic recording is performed on the magnetic layers by a magnetic head while being rotated. A magnetic disk cartridge in which a so-called flexible disk (a so-called flexible disk) is housed in a flat case is provided, and is mainly used as a recording medium for a computer because of its advantages such as easy handling and low cost.

The magnetic disk cartridge is provided with a case window for inserting a magnetic head for inserting and removing a magnetic head for magnetic recording / reproducing to or from one side or both sides of a magnetic disk medium from the outside. Further, the case window is provided with an opening / closing shutter member for preventing dust and the like from entering when not in use.

By the way, the miniaturization of the computer using the above-mentioned magnetic disk cartridge has progressed, and the notebook type personal computer has become widespread. An external system without a built-in disk drive device is now being sold. The adoption of this external method is excellent in terms of portability of small personal computers, but, for example, the problem of not being able to record and reproduce large amounts of data because magnetic disk cartridges cannot be used at the destination of small computers, This causes a problem that data cannot be recorded on a plurality of magnetic disk cartridges.

[0005] In view of the above, some small personal computers are provided with a PC card slot (compliant with the PCMCIA specification) for an external interface and additional memory, and are used by mounting a PC card using an electronic circuit such as a memory card. You. Therefore, it has been proposed to configure an external storage device using a magnetic disk cartridge using the PC card slot.

A PC that can be inserted into the PC card slot
The specifications of the card are Type II and have a thickness of 5.0 mm. The external storage device is intended to constitute a magnetic disk cartridge and a disk drive device within this thickness. It is necessary to make the thickness as thin as about 2 to 3 mm.

As such an ultra-thin magnetic disk cartridge, the present inventors have a flat cartridge case for rotatably storing a disk-shaped magnetic disk medium, and the magnetic head is accessible to the cartridge case. A magnetic disk cartridge provided with a shutter member that opens and closes the case window, wherein the cartridge case is provided with a base plate having a circular recess for accommodating a magnetic disk medium, and a base plate above and below the base plate. A cover case having a substantially planar shape to be attached, the shutter member being slidably disposed between the base plate and the cover case, and upper and lower face plate portions and the face plate portion serving as the shutter member. And a connecting portion for connecting the upper and lower face plates from the connecting portion. The shutter member is used to form a shutter window that is open in communication with the shutter member, and the shutter member is always closed by, for example, a spring (in one of the sliding directions of the shutter member, In the recording / reproducing operation, a shutter opening / closing member of the disk drive device opens the opening (the sliding direction) against the urging of the spring. (The direction in which the shutter member is moved to the open position where the case window is opened) is considered.

[0008]

However, as described above, the shutter member of the magnetic disk cartridge having the above-described structure has a shutter window portion which is open from the connecting portion to communicate with the upper and lower face plate portions. Since it is shaped like a letter, the shutter member side portions (portions located on both sides in the sliding direction of the shutter window portion) located on both sides of the shutter window portion are in a cantilever shape,
When the shutter opening / closing member attempts to move the shutter member in the opening direction against the spring, both or one of the side portions of the shutter member slides the shutter member by the pressing force of the shutter opening / closing member and the urging force of the spring. There is a problem that bending deformation easily occurs in the moving direction.

Further, in the magnetic disk cartridge having the above structure, the shutter member is provided between the base plate and the upper and lower cover cases. There is also a problem that the upper and lower cover cases are in sliding contact with each other, so that the sliding resistance is increased and smooth sliding is hindered, and there is a possibility that abrasion powder is generated when the edge of the shutter member in the sliding direction hits the cover case.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a magnetic disk cartridge having the above-described magnetic disk cartridge, which is provided with a shutter member that is less likely to be bent and deformed even when a pressing force is applied by a shutter opening / closing member. Is to do.

Another object of the present invention is to provide a magnetic disk cartridge as described above,
An object of the present invention is to provide a magnetic disk cartridge capable of preventing the bending deformation and smoothly sliding a shutter member.

[0012]

In order to achieve the above object, a magnetic disk cartridge according to the present invention has a flat cartridge case for rotatably storing a disk-shaped magnetic disk medium, and the cartridge case has a magnetic disk medium. In a magnetic disk cartridge provided with a case window accessible to a head and provided with a shutter member for opening and closing the case window, the cartridge case includes a base plate having a circular concave portion for accommodating a magnetic disk medium; A cover case having a substantially planar shape attached to the upper and lower sides, wherein the shutter member is slidably disposed between the base plate and the cover case, and the shutter member includes upper and lower face plate portions and the face plate portion. Is formed in a substantially U-shaped cross section from a connecting portion for connecting the A shutter window portion that is open in communication with the face plate portion is formed, and at a root portion of at least one of the upper and lower face plate portions, the shutter member on a shutter member side portion located with the shutter window portion interposed therebetween. A reinforcing portion for increasing rigidity against bending deformation in the sliding direction.

In the magnetic disk cartridge, the reinforcing portion may be constituted by a ridge projecting outward in the vertical direction of the cartridge case.

[0014]

According to the magnetic disk cartridge of the present invention, a reinforcing portion for increasing the rigidity of the shutter member side portion against bending deformation in the sliding direction is formed at the root of the shutter window of the shutter member. Therefore, the rigidity against the bending deformation is increased by the reinforcing portion,
It is possible to suppress bending deformation of the shutter member side portion formed in a cantilever shape when the shutter member opens.

Further, in the case where the reinforcing portion is constituted by a ridge projecting outwardly in the vertical direction of the cartridge case, the tip (vertical end) of the ridge abuts on the inner surface of the cover case and slides. As a result, excessive contact between the shutter member and the cover case is avoided, the sliding resistance of the shutter member is reduced, and the sliding of the shutter member can be performed smoothly. As it can avoid contact with the edge cover case,
The generation of wear powder and the like due to the contact can be prevented.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 is a perspective view of an upper surface side of the magnetic disk cartridge according to this embodiment, FIG. 2 is a perspective view of a lower surface side, and FIG. 1 shows a state in which a shutter member is closed, and FIG. Is shown. FIG. 3 is an exploded perspective view of the magnetic disk cartridge. In addition, in each figure, in order to clarify the structure, the thickness and the like of each part are shown in a ratio different from the actual size.

The magnetic disk cartridge 1 has a flat disk case 10 (see FIG. 3) rotatably housed in a flat cartridge case C. The cartridge case C includes a base plate 2 serving as a central member,
An upper cover case 3 and a lower cover case 4 are attached to the upper and lower sides of the base plate 2 and have a substantially planar shape. The magnetic disk medium 10 has a disk-shaped base made of a flexible polyester sheet or the like, on both sides of which magnetic layers are formed.
(Center core) is fixedly integrated.

On the lower surface of the cartridge case C, there is provided a hub hole 7 capable of chucking a drive motor of a disk drive device (hereinafter referred to as a drive device) and the rotary drive hub 11. The magnetic disk medium 10 is accommodated in the cartridge case C such that the bottom of the hub 11 faces. Further, the insertion direction D of the cartridge case C with respect to the drive device (arrow in FIG. 1)
Is formed at the front end portion thereof with a case window 8 accessible by the recording / reproducing magnetic head. Case window 8
The front end portions of the base plate 2 and the upper and lower cover cases 3 and 4 are opened, and a portion communicating with the upper and lower surfaces is subsequently opened vertically in a rectangular shape (see FIG. 2). A shutter member 5 for opening and closing the case window 8 is built inside the upper and lower cover cases 3 and 4 so as to be slidable in the left-right direction.

The horizontal direction in which the shutter member 5 slides, that is, the sliding direction is also referred to as the opening / closing direction. In this opening / closing direction, the shutter member 5 closes the case window 8 (shown in FIG. 1). The direction toward the open position (the position shown in FIG. 2) is referred to as the opening direction.

With the structure of the case window 8 as described above,
The recording / reproducing magnetic head can be inserted into the case window 8 from the front side without opening and closing greatly, and the built-in shutter member 5 is employed, and the shutter member 5 comes off due to insufficient strength due to miniaturization. Is prevented, the toughness against dropping and the like is improved, and the assembling property is also improved.

The structure of each component will be specifically described with reference to FIG. First, the base plate 2 is made of, for example, an acrylonitrile-butadiene-styrene copolymer (ABS resin)
Alternatively, it is a substantially rectangular flat plate formed of a synthetic resin such as a POM resin or the like. A circular recess 21 for accommodating the magnetic disk medium 10 is provided at the center of the upper surface. A hub hole 7 is opened in the portion. Further, the front side portion of the bottom plate is removed in a substantially rectangular shape, and a movement space 2 for receiving a lower surface plate portion 52 of the shutter member 5 described below and allowing the lower surface plate portion 52 to move in the opening and closing direction.
2 are formed. At the front end of the base plate 2, a central portion is removed in the front-rear direction and a case window 8 penetrating vertically is opened, and the case window 8 communicates with the moving space 22. One of the front ends of the front end of the base plate 2 has a front surface retracted from the other front wall to form a spring housing portion 23, and a shutter spring 6, which will be described later, is disposed in this portion. Further, a tapered portion 24 is provided at a front corner portion of the front wall opposite to the spring storage portion 23 facing the case window portion 8 so that the shutter member 5 is guided when the shutter member 5 closes. 5, so that the base plate 2 is not scraped off by interference. The moving space 22 may be formed in a thin groove shape from the bottom surface side when there is a margin in the thickness direction of the base plate 2.

Further, four corners 25 of the four corners of the base plate 2 are provided so as to protrude in the vertical direction, have a large thickness, and protrude outwardly. When the upper and lower cover cases 3 and 4 are fitted to the base plate 2, the corners 25 of the base plate 2 are exposed to the outside. Each corner portion 25 is provided in such a shape that its surface protrudes flush or outward with the surface of the upper and lower cover cases 3 and 4.

The corner portion 25 of the base plate 2 is exposed to the outside, so that when a shock or the like at the time of a drop is applied, the corner portion 25 can absorb the shock and at the time of insertion and removal operations with respect to the drive device. , Which prevents it from getting stuck and ensures stable operation. Also, holes 26 penetrating in the vertical direction are provided in each corner 25.
(It may be a hole of intermediate depth without penetrating),
Greater buffering action at the time of a drop impact is obtained. The base plate 2 is a magnetic disk medium 1
0 has a strength that allows deformation that does not hinder recording and reproduction. It is preferable that the base plate 2 is made of an elastic plastic from the viewpoint of absorbing the impact, and it is preferable that the base plate 2 contains a lubricant from the viewpoint of sliding with the shutter member 5 to improve dimensional accuracy. From the viewpoint of assembling with the cover cases 3 and 4, it is preferable to include a filler material.

Further, as shown in FIG. 1, a notch-shaped concave portion 15 is provided on the side surface of the corner portion 25 on both sides of the front portion of the base plate 2, and this concave portion 15 is used for positioning when mounted on the drive device, or Are formed to prevent erroneous insertion in the front-back direction or the front-back direction. The recess 15 may be provided only on one side surface or on the side surface of the rear corner portion 25. In the case shown in the figure, the corner of one of the front corners 25 is formed in the oblique cutout 16 to serve as an erroneous insertion prevention part.

Further, a part of the side surface of the cartridge case C is located at a position different from the concave portion 15, for example, as shown in FIG.
An identification unit 17 for identifying the type of the disk (for example, the type of recording capacity) from the drive device side is provided on the side wall portion 4. This identification unit 17 has a detection function on / off.
An identification piece that can be turned off may be provided so as to be fitted or inserted / removed. By forming the concave portion 15 and the identification portion 17 on the side surface, a detection mechanism or the like on the drive device side that does not have a vertical installation space can be arranged on the side. It is to be noted that a write protector section can be provided at the position of the identification section 17. The upper and lower cover cases 3 and 4 are formed of a high-strength material such as a pressed stainless metal plate, and the upper cover case 3 and the lower cover case 4 are substantially symmetrical, and the corners of the four corners are removed in a rectangular shape. , A flat rectangular case window 8 is opened in the center of the front part,
The front, rear, left and right edges are bent at right angles, and the front walls 31, 41, both side walls 32, 42, and the rear walls 33, 43 are respectively provided.
Becomes One of the front wall portions 31 and 41 is lower than the case window portion 8, and when the upper and lower cover cases 3 and 4 are attached to the base plate 2, as shown in FIG.
A slit groove 18 is formed between 1 and 41, and a shutter opening / closing member 60 of a drive device can be inserted and moved into the slit groove 18. A notch is provided at an end portion of the opposite front wall portion 31, 41, that is, a portion located in front of the spring storage portion 23, and the front wall portions 31, 41 of the upper and lower cover cases 3, 4 are fitted together. And a rectangular spring insertion port 1
9 (see FIG. 1), which is used for mounting the shutter spring 6.

In the center of the upper cover case 3, a concave portion 35 serving as a label attaching portion is formed on the upper surface, and the bottom surface of the concave portion 35 projects downward. In the assembled state, the concave portion 35 has the magnetic disk medium 10 at the center in the thickness direction.
The upper space is reduced in accordance with the thickness of the bottom plate of the base plate 2 so that the upper and lower spaces are equal, and the rotational stability of the magnetic disk medium 10 is improved. A hub hole 7 is opened at the center of the lower cover case 4.

When the upper and lower cover cases 3 and 4 are assembled to the base plate 2, the front surface of the base plate 2 and the upper and lower cover cases 3 and 4
The dimension is set so that a thin space in which the shutter member 5 can slide is formed extending in the left-right direction between the inner surface of the shutter 4 and the inner surface of the shutter 4. The method of fixing the base plate 2 to the upper and lower cover cases 3 and 4 may be such that the contact portions of the upper and lower cover cases 3 and 4 are mutually joined by spot welding, bonding, caulking, or the like. This is performed by fixing the cases 3 and 4 by caulking, bonding or the like.

The shutter member 5 is inserted into a moving space 22 opened in the base plate 2 between the base plate 2 and the upper and lower cover cases 3 and 4 and on the lower surface side so as to be slidable in the left and right sliding direction (opening and closing direction). Be attached. The shutter member 5 is made of metal and is formed in a substantially U-shaped cross section from, for example, a stainless steel plate or an aluminum plate. The upper plate 51 and the lower plate 52 are connected so as to extend parallel to the sliding direction of the front end. The height of the connecting portion 53 is substantially equal to the thickness of the front portion of the base plate 2. From the connecting portion 53 to the upper plate 51 and the lower plate 52
The cartridge window C is provided with a shutter window portion 54 having a rectangular shape and communicating with the cartridge window C. The shutter window portion 54 has a size substantially corresponding to the case window portion 8 of the cartridge case C and can communicate with this.
The shutter window 54 is provided at a position offset from the center of the shutter member 5 in the sliding direction.

On the inner surface of one front end of the shutter window 54, a spring receiving projection 5 bent from the connecting portion 53 is provided.
A shutter spring 6 made of a coil spring is contracted on its back in the sliding direction, and the shutter 6 urges the shutter member 5 in the closing direction. Although not shown, at least one of the upper surface plate portion 51 and the lower surface plate portion 52 is cut and raised, and is engaged with a guide groove provided in the base plate 2 so as to extend in the sliding direction. Get the prevention of coming off. Further, a reinforcing portion 56 is formed on the upper plate portion 51 and the lower plate portion 52 of the shutter member 5. The reinforcing portion 56 will be described later in detail.

The hub member 7 on the bottom surface may be opened and closed by the shutter member 5. In this case, the lower plate 52 of the shutter member 5 is extended to the portion of the hub hole 7 so that the hub hole 7 is closed by the lower plate 52 during the closing movement, and the hub hole 7 is opened according to the opening movement. It is formed.

On the upper and lower sides of the magnetic disk medium 10, protective sheets 12 made of a plastic sheet or the like having a PET sheet surface subjected to a sliding process (Teflon (registered trademark) process) are interposed. The protective sheet 12 is formed in a substantially C shape in which a portion corresponding to the case window 8 is removed in a radial direction, and an opening 12a is formed in a portion opposite to the case window 8, and a cleaning member 13 is formed in this portion. Are fixed to the inner surface of the upper cover case 3 and the bottom surface of the base plate 2 from the magnetic disk medium 10 side, and the protective sheet 12 is fixed at the same time when the cleaning member 13 is fixed. The cleaning member 13 includes the magnetic disk medium 1.
The brushed side is provided on the side facing 0, and is in contact with the surface of the magnetic disk medium 10 to remove dust on the surface.
An adhesive is provided on the opposite surface.

The magnetic disk cartridge 1 as described above
Is assembled by fixing the protection sheet 12 to the circular recess 21 of the base plate 2 and the lower surface of the upper cover case 3 in advance by fixing the cleaning member 13, and setting the magnetic disk medium 10 in the circular recess 21 of the base plate 2. The shutter member 5 is mounted from the front.
Subsequently, the upper cover case 3 is fitted to the base plate 2 from above and the lower cover case 4 is fitted and held from below to integrate them. Thereby, the base plate 2
The upper surface of the circular concave portion 21 is covered with the upper cover case 3 and the circular concave portion 21 is defined by the bottom surface of the upper cover case 3.
Is a storage space for the magnetic disk medium 10, and the magnetic disk medium 10 is rotatably stored. Thereafter, the coiled shutter spring 6 is inserted into the internal spring accommodating portion 23 while bending the coiled shutter spring 6 from the spring insertion opening 19 in the front wall portion of the upper and lower cover cases 3, 4. , And pushed into the storage portion 23 while shrinking the rear end to complete the assembly. The shape of the spring insertion opening 19 prevents the assembled shutter spring 6 from coming off.

The magnetic disk cartridge 1 as described above
When the shutter opening / closing member 60 of the drive device is loaded into the drive device, the shutter opening / closing member 60 is inserted into the slit groove 18 at the front end, engages with the end of the shutter member 5, and rotates in the direction of arrow E shown in FIG. Then, the shutter member 5 is slid in the opening direction, and the case window 8 is opened.
The drive unit has a magnetic head at the back, and a drive unit is provided at the bottom so as to be able to move up and down, and the spindle is locked by the rotation drive hub 11 of the magnetic disk medium 10 of the inserted magnetic disk cartridge 1. It is configured to be driven to rotate.

With the structure of the cartridge case C as described above, the strength of the magnetic disk
Is formed within a predetermined thickness, and the thickness of the magnetic disk cartridge 1 can be reduced while ensuring operation reliability, so that an external storage device that can be mounted in a PC card slot can be configured. . In particular, sufficient strength is secured by integrating the base plate 2 and the cover cases 3 and 4. The cover cases 3 and 4 are made of a thin metal and are likely to be deformed in a single piece state, and the base plate 2 is also made of plastic and easily torsionally deformed. However, the combination of the two sufficiently satisfies the requirements as the magnetic disk cartridge 1. Strength can be secured and dimensions can be maintained.

The overall structure of the magnetic disk cartridge is as described above. Next, regarding the reinforcing portion 56, FIG. 4 is an enlarged perspective view of the shutter member 5 and FIG. This will be described in detail with reference to a certain FIG.

When the case window 8 is opened, the shutter opening / closing member 60 pushes the closing-side end of the connecting portion 53 in the opening direction and slides in the opening direction. At this time, the pressing force of the shutter opening / closing member 60 and the urging force of the shutter spring 6 act on the shutter member 5 in directions that face each other in the sliding direction. However, as shown in FIG. 4, the shutter member 5 has a shutter window 54 that opens from the connecting portion 53 to communicate with the upper and lower face plates 51 and 52. None, shutter member side portions 57, 5 located on both sides in the sliding direction with shutter window portion 54 interposed therebetween.
8 have a free cantilever shape at their front end sides and are easily bent and deformed in the sliding direction, so that the sliding direction is determined by the force of the shutter opening / closing member 60 and the force of the shutter spring 6. There is a problem that bending deformation tends to occur inward. In particular, in the case where the side portion 57 on the shutter opening / closing member 60 side has a shorter width in the sliding direction than the side portion 58 on the spring 6 side as in the above-described embodiment, the shorter side portion 57 has a smaller width. However, there is a problem that bending deformation tends to occur in the closing direction as shown by a two-dot chain line in FIG.

Therefore, the shutter member 5 includes a shutter portion 59 at the root portion (the rear portion of the shutter window portion 54, that is, the portion opposite to the connecting portion 53) of the shutter window portion 59 of the upper surface plate portion 51 and the lower surface plate portion 52. A reinforcing portion 56 for increasing rigidity against bending deformation of the shutter member side portions 57 and 58 in the sliding direction due to the force of the opening / closing member 60 and the spring 6.
Are formed. In the present embodiment, a reinforcing rib 56 extending in a direction substantially parallel to the connecting portion 53 is formed as the reinforcing portion. The reinforcing rib 56 is formed of a ridge projecting outwardly in the vertical direction of the cartridge case, extends parallel to the connecting portion 53, and corresponds to the root portion 59 at least in the sliding direction with the shutter window portion 54. Formed over a range wider than the range 59a;
In addition, the protrusions 56 are formed such that their vertical ends contact the inner surfaces of the upper and lower cover cases 3 and 4 and slide. The protruding ridge 56 is a squeezing ridge, and its protruding height is 0.1 mm from the viewpoint of improving rigidity against the bending deformation and restricting the thickness of the magnetic disk cartridge.
mm to 0.3 mm is desirable, and 0.2 mm is more desirable.

In the present embodiment, the reinforcing ribs composed of the ridges 56 as described above are formed at the root portions 59 of the shutter windows of the upper and lower plate portions 51, 52, and thus the above-described portions of the shutter member side portions 57, 58 are formed. The rigidity against bending can be improved, and the side portion 5 when the shutter member opens moves.
7, 58 bending deformation can be suppressed. In addition, the reinforcing rib 56 is formed as a ridge projecting outward in the vertical direction,
Since the top end in the vertical direction slides in contact with the inner surfaces of the upper and lower cover cases 3 and 4, the edges in the sliding direction of the upper and lower plate portions 51 and 52 slide in contact with the upper and lower cover cases 3 and 4. And the contact area between the shutter member 5 and the upper and lower cover cases 3 and 4 is reduced, the frictional resistance when the shutter member slides is reduced, and the stability of the opening and closing movement is secured. .

The reinforcing portion of the present invention may be of any type as long as it can increase the rigidity of the shutter member side portion against bending deformation. Further, the reinforcing portion may be formed on only one of the upper and lower plate portions. Further, when using a ridge as the reinforcing portion, it is not necessarily required to be a linear ridge as in the above embodiment,
Although ridges of various shapes can be used, those formed over a range of a predetermined length in a direction parallel to the connecting portion are preferable from the viewpoint of increasing rigidity against the bending deformation and reducing frictional resistance during sliding. Can be adopted.

[Brief description of the drawings]

FIG. 1 is a perspective view of an upper surface side of a magnetic disk cartridge according to an embodiment of the present invention.

FIG. 2 is a perspective view of the lower surface side of the magnetic disk cartridge of FIG. 1 in a state where a shutter member is opened.

FIG. 3 is an exploded perspective view of the magnetic disk cartridge of FIG. 1;

FIG. 4 is an enlarged perspective view of a shutter member.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic disk cartridge C cartridge case 2 Base plate 3 Upper cover case 4 Lower cover case 5 Shutter member 8 Case window 10 Magnetic disk media 51 Top plate 52 Lower plate 53 Connecting part 54 Shutter window 56 Reinforcement part 57 Shutter member side Part 58 Shutter member side 59 Root

Claims (2)

[Claims] 1. A cartridge having a flat cartridge case rotatably accommodating a disk-shaped magnetic disk medium, a case window portion accessible to a magnetic head is formed in the cartridge case, and a shutter for opening and closing the case window portion. In the magnetic disk cartridge provided with the member, the cartridge case includes: a base plate having a circular concave portion for accommodating the magnetic disk medium; and a substantially planar cover case which is attached to the upper and lower sides of the base plate. The shutter member is slidably disposed between the case and the case. The shutter member is formed to have a substantially U-shaped cross section from upper and lower face plate portions and a connection portion connecting the face plate portions. A shutter window that is open in communication with the upper and lower face plate portions is formed, and at least the upper and lower face plate portions are formed. At the root of the shutter window, a reinforcing portion is formed to increase the rigidity of the shutter member side portion located on both sides of the shutter window with respect to bending deformation in the sliding direction of the shutter member. Characteristic magnetic disk cartridge. 2. The magnetic disk cartridge according to claim 1, wherein the reinforcing portion is formed by a ridge projecting outward in a vertical direction of the cartridge case.