Abstract:
A recording disk cartridge has a plurality of flexible recording disk media integrally rotatably housed within a cartridge case which comprises a lower plate for configuring a lower wall parallel to said plurality of the recording disk media, at least one inner plate that is stacked and fixed on said lower plate and partitions said plurality of the recording disk media, a shutter that opens and closes a case opening which is formed in a portion of a side wall configured by the lower plate and the inner plate and the upper plate, wherein the shutter comprises a lower rotor which is rotatably supported in an inner side of the lower plate, an upper rotor which is rotatably supported in an inner side of the upper plate and a shutter plate that couples both the lower rotor and the upper rotor and shuts off the case opening.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a recording disk cartridge comprising a plurality of flexible recording disk media.  
         [0003]     2. Description of the Related Art  
         [0004]     Conventionally, as a recording disk medium a flexible recording disk medium is known where a magnetic layer is formed on both faces of a disc-form support body consisting of a flexible material such as a polyester sheet. Although the magnetic disk medium has a merit of speedily accessing data in comparison with a magnetic tape, on the other hand, it has a demerit of a memory capacity being small because a recording area thereof is small.  
         [0005]     In order to solve the demerit of the flexible magnetic disk medium, it is conventionally disclosed a magnetic disk cartridge for housing a plurality of magnetic disk media in one cartridge case (for example, see JP 2004-22011A).  
         [0006]     In this connection, because a flexible magnetic disk medium is low in rigidity thereof, there is a problem that the medium tends to vibrate in a vertical direction for a recording face when rotated. Therefore, in an invention of JP 2004-22011A each magnetic disk medium is made a configuration of being pinched by shutters. Thus by arranging plate members of high rigidity such as the shutters in a vicinity of the magnetic disk medium, the recording face can be stabilized because the medium becomes along the plate members, accompanied with a rotation of the medium.  
         [0007]     However, because a magnetic disk cartridge of JP 2004-22011A is configured of movable shutters arranged by four for one magnetic disk medium, there is a problem that the cartridge is complicated in a structure thereof and is difficult to keep a parallelism to the medium. In addition, because the magnetic disk cartridge is mass produced goods, it is preferable to be excellent in assembling capability and productivity. Furthermore, the magnetic disk cartridge is preferable to be high in a degree of freedom in a design change so as to easily set a plurality of kinds thereof where number of magnetic disk media is made three, five and the like.  
         [0008]     Considering the function of the shutter in the invention taught by JP 2004-22011A (called as the reference 1, hereinafter), every magnetic disc is adjoined with a different shutter and therefore the outer dimension of the physical thickness of the cartridge increases more than the simple increment of the number of recording disk media.  
         [0009]     In order to solve the deficiency of the exiting invention taught by the reference 1, the present invention provides a simple cartridge structure with easy assembling capability and high producible capability that facilitate to change the quantity of the installed disc media. These result in a compact and simple structure of the recording disc cartridge with a shutter.  
       SUMMARY OF THE INVENTION  
       [0010]     A recording disk cartridge of the present invention is one where a plurality of flexible recording disk media is integrally rotatably housed within a cartridge case comprising: a lower plate for configuring a lower wall parallel to the plurality of the recording disk media; at least one inner plate that is stacked and fixed on the lower plate and partitions the plurality of the recording disk media; and an upper plate that is stacked and fixed on the inner plate, a case opening formed in the side wall and a shutter that opens and closes the case opening wherein the shutter comprises a shutter plate that shuts off the case opening of which edges are configured with the lower plate and the upper plate both of which insides a lower rotor and an upper rotor are, respectively, coupled.  
         [0011]     In accordance with such the configuration, in the recording disk cartridge of the present invention the cartridge case is configured in a form of stacking up the lower plate, the inner plate and the upper plate. Therefore, a pair of the inner plate and the recording disk medium is made one unit, all inner plates can be made a same part and therefore, the recording disk cartridge is excellent in productivity. And because the recording disk medium in an assembling process can also be carried by making a lower plate and an inner plate as a substitute of a tray, the recording disk cartridge is excellent also in assembling capability without damaging and staining the medium. In addition, in a case that it is intended to make a specification of changing a number of recording disk media, it is easy to change the specification because it suffices to mainly change a number of inner plates. Furthermore, because an inner plate of a partition plate is fixed as part of the cartridge case, the recording disk cartridge is easy to realize accuracy such as a parallelism to the recording disk media and can heighten a rotational stability especially at a high speed such as 2000 to 8000 rpm. Since a single shutter plate can open and close the case opening, the construction of the shutter can be simplified and therefore contribute to compactization of the physical dimensions of the recording disk cartridge. Since the shutter is formed with the lower rotor and coupled with the upper rotor to be integrally rotatable, the open/close of the shutter can behave in a good repeatable manner.  
         [0012]     Since the shutter plate is formed with either the lower rotor or the upper rotor, it is possible to shorten the assembly process of the shutter. It is also possible to be flexible in changing of the quantity of the media set in the recording disk cartridge by independently assembling the lower rotor, the upper rotor and the shutter so that the height of the shutter plate is changed in accordance to the quantity of media set in the recording disk cartridge.  
         [0013]     At least either the lower rotor or the upper rotor has a shutter guiding groove wherein the shutter guiding groove has a wider opening in the mating surface to the shutter plate, the shutter plate has the edges wherein the shutter plate has a thin thickness at the mating edge against the shutter guiding groove or both configurations of such shutter guiding groove and the shutter plate have the forms as described are adopted. Then it is easily to mate the shutter plate with the shutter guiding groove so that the improvement of assembly can be obtained.  
         [0014]     The shutter has a mating portion which mates with shutter open/close supporting portion formed in the disk drive so that the mating portion transmits a rotation force to the shutter mechanism. Therefore it is possible to transmit the linear force of setting and ejecting the recording disk cartridge in a rotation force to and from the disk drive and to simplify the structure of the shutter.  
         [0015]     In order not to de-guide the upper rotor from the upper plate, the upper rotor is stopped by a stopper which is formed with the upper plate. Then the upper plat and the upper rotor are unified and the positioning of these parts can be easy when the rotor and the shutter plate are assembled. The upper rotor and the upper plate are not de-guided even when they are downwardly held and therefore it is easy to assemble the recording disk cartridge. Moreover, the upper plate is the upper position in many cases when the recording disk cartridge is used and then it is possible to rotate the shutter as far as the upper rotor is stopped against the upper plate in a good repeatable manner.  
         [0016]     In accordance with such the configuration, in the recording disk cartridge of the present invention the cartridge case is configured in a form of stacking up the lower plate, the inner plate and the upper plate. Therefore, a pair of the inner plate and the recording disk medium is made one unit, all inner plates can be made a same part and therefore, the recording disk cartridge is excellent in productivity. And because the recording disk medium in an assembling process can also be carried by making a lower plate and an inner plate as a substitute of a tray, the recording disk cartridge is excellent also in assembling capability without damaging and staining the medium. In addition, in a case that it is intended to make a specification of changing a number of recording disk media, it is easy to change the specification because it suffices to mainly change a number of inner plates.  
         [0017]     Furthermore, it is possible to obtain a recording disk cartridge with a shutter in a simple structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is an exploded perspective view of a magnetic disk cartridge related to an embodiment of the present invention.  
         [0019]      FIG. 2A  is an external perspective view of a magnetic disk cartridge with a shutter closed related to an embodiment of the present invention  
         [0020]      FIG. 2B  is an external perspective view with the shutter opened related to the magnetic disk cartridge.  
         [0021]      FIG. 3  is a perspective view showing an inner face of an upper plate.  
         [0022]      FIG. 4  is a section view taken along a line IV-IV in  FIG. 2B  of the magnetic disk cartridge loaded on a magnetic disk drive.  
         [0023]      FIG. 5  is a partially enlarged drawing of  FIG. 4 .  
         [0024]      FIG. 6  is an exploded perspective view showing a stack structure of magnetic disk media.  
         [0025]      FIG. 7  is a section view showing mating status of a shutter and an upper rotor regarding an embodiment.  
         [0026]      FIG. 8  is a section view showing mating status of a shutter and an upper rotor regarding another embodiment.  
         [0027]      FIG. 9  is a section view of mating status of parts composing a shutter regarding another embodiment.  
         [0028]      FIG. 10  is an external perspective view of recording disk cartridge which is closed, particularly, shows another embodiment of a mating portion of a shutter open/close mechanism.  
         [0029]      FIG. 11A  is a perspective view showing inside of an upper plate, especially, shows an embodiment of mating status of an upper rotor and an upper plate.  
         [0030]      FIG. 11B  is a perspective view showing inside of an upper plate, especially, shows another embodiment of mating status of an upper rotor and an upper plate. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     Here will be described an embodiment of the present invention in detail, referring to drawings as needed. In the embodiment will be described a case of adopting a magnetic disk medium as an example of a recording disk medium.  
         [0032]     Meanwhile, in a description below, with respect to up/down directions, making it a standard a typical use state of the magnetic disk cartridge, vertical directions for faces of magnetic disk media are called the up/down directions for convenience.  
         [0033]     As shown in  FIG. 1 , in a magnetic disk cartridge  1  of an example of a recording disk cartridge are stacked a lower plate  10  for configuring a lower wall thereof; a plurality of, for example, four inner plates  20  and an upper plate  30  for configuring an upper wall thereof in this order; these are fastened and fixed with four screws  91  and thereby a cartridge case  2  (see  FIG. 2A ) is configured. Between the lower plate  10  and the lowermost inner plate  20 , between any adjacent two of the four inner plates  20  and between the uppermost inner plate  20  and the upper plate  30  is arranged a magnetic disk medium  41 , respectively. Each magnetic disk medium  41  is a disc form having an opening  41   a  at center thereof and a center core  42  made of metal is affixed at rim of the opening  41   a . It is designed that any adjacent two center cores  42  are engaged by spacers  43 ,  43 ′ and that five magnetic disk media  41  (the magnetic disk media  41  stacked and integrated are assumed to be a disk stack  40 ) are integrally rotated.  
         [0034]     In each of the inner plates  20  is formed a rib  22  for abutting with upper/lower plates at a peripheral rim of a flat main plate  21 . Part of a right near side of each of the inner plates  20  in  FIG. 1  forms a notch  23  so that magnetic heads  63  (see  FIG. 4 ) can easily move onto the magnetic disk media  41 . At the portion of the notch  23  is not formed the rib  22  and therefore, when the inner plates  20  are stacked up, an opening  3  is formed on a side face of the cartridge case  2  as shown in  FIG. 2A .  
         [0035]     The opening  3  is opened/closed by a shutter  4  that coaxially rotates with the disk stack  40 . As shown in  FIG. 1 , the shutter  4  is configured by combining a lower rotor  51  and an upper rotor  52 .  
         [0036]     Next will be described each member in more detail.  
         [0037]     The lower plate  10  is designed at a peripheral rim of a main plate  11  of a substantially square to mainly form a side wall  13  and a rib  12  for abutting with a lower face of the rib  22  of the lowermost inner plate  20 . The side wall  13  is vertically provided in a predetermined range, for example, around one third range of one edge, from one corner of the main plate  11  (near side corner in  FIG. 1 ) and is formed approximately in height of the inner plates  20  stacked.  
         [0038]     A sector portion toward a center of the main plate  11  from one edge  11   a  (one edge of right near side in  FIG. 1 ) continuing into the side wall  13  of the main plate  11  is designed to form a depression  14   a  lowered by one step, not to form the rib  12  at the peripheral rim of the main plate  11  and to become an opening  14 . Thus it becomes easy for the magnetic heads  63  to proceed into the cartridge case  2 .  
         [0039]     An approximately central one third range of the other edge  11   b  (one edge of left near side in  FIG. 1 ) continuing into the side wall  13  of the main plate  11  is designed not to form the rib  12  but to become an opening  15  so that a gear  51   f  of the lower rotor  51  described later can be exposed. In addition, outside the side wall  13  of the other edge  11   b  is formed a groove  13   a  along a periphery of the lower plate  10 , continuing into the opening  15 . The groove  13   a  is designed to be a passage where a shutter open gear  67  (see  FIG. 2A ) of a magnetic disk drive proceeds in a direction shown in an arrow of  FIG. 2A  and enters in the opening  15  in order to engage in the gear  51   f.    
         [0040]     The rib  12  is formed so as to protrude upward across all periphery except the side wall  13  and the openings  14 , 15  out of a peripheral rim of the main plate  11 . At center of the main plate  11  is formed a circular opening  16  for exposing the center core  42  provided inside the lowermost magnetic disk medium  41 . At upper rim of the opening  16 , across all periphery thereof is formed a rib  17  outside which a central opening  51   c  formed at center of the lower rotor  51  fits. The rib  17  rotationally freely supports the lower rotor  51 .  
         [0041]     In addition, on an upper face (inner face) of the main plate  11  is formed a circular lower rotor support groove  18  at a position corresponding to peripheral rim of the lower rotor  51 . The lower rotor support groove  18  rotationally freely supports the lower rotor  51  coaxially with the magnetic disk media  41  by engaging in a rib  51   d  (see  FIG. 4 ) formed downward at a peripheral rim of the lower rotor  51 .  
         [0042]     In addition, at four corners of the main plate  11  are formed screw holes  19  where female threads are formed, respectively, with penetrating through the up/down directions.  
         [0043]     The main plate  21  of each of the inner plates  20  is substantially a square and a portion corresponding to one of four corners of the square is designed to be an arc (arc portion  24 ) one size larger than the magnetic disk medium  41 . At one edge (right near side in  FIG. 1 ) continuing into the arc portion  24  is formed the notch  23  into a sector. The rib  22  protrudes the up/down directions and is formed across all periphery except the arc portion  24  and the notch  23  out of periphery rim of the main plate  21 . At center of the main plate  21  is formed a central opening  21   c  for enabling the upper center core  42  to be exposed and to be coupled with the lower center core  42 .  
         [0044]     In addition, at three corners of the main plate  21 , with penetrating through the three corners in the up/down directions, are formed holes  29  through which screw shaft portions  91   a  of the screws  91  are inserted, respectively.  
         [0045]     The upper plate  30  is formed substantially symmetric to the lower plate  10 . As shown in  FIG. 3 , in the upper plate  30 , on a substantially square main plate  31  are formed a depression  34  corresponding to the depression  14   a , a rib  37  corresponding to the rib  17  and an upper rotor support groove  38  corresponding to the lower rotor support groove  18 . Meanwhile, at center of the main plate  31  are not formed an opening and a side wall corresponding to the side wall  13 .  
         [0046]     In addition, at a peripheral rim of the main plate  31 , across all periphery except the depression  34  is formed a rib  32  protruding downward.  
         [0047]     In addition, at four corners of the main plate  31  are respectively formed holes  39  that enables the screw shaft portions  91   a  of the screws  91  to be penetrated therethrough.  
         [0048]     The lower rotor  51  is designed so that: a central opening  51   c , a notch  51   e , a rib  51   d  and the gear  51   f  are formed on a ring-form lower rotor plate  51   a  substantially same as the magnetic disk media  41 ; and a shutter plate  51   b  is vertically provided at the peripheral rim of the lower rotor plate  51   a . The central opening  51   c  is formed as a circle fitting outside the rib  17 , the notch  51   e  is formed as a sector corresponding to the depression  14   a . In addition, the rib  51   d  is provided downward at a peripheral rim of a lower face of the lower rotor plate  51   a , corresponding to the lower rotor support groove  18 .  
         [0049]     The shutter plate  51   b  is a blocking member for blocking the opening  3  (see  FIG. 2A ) and the disk stack  40 , is vertically provided along the peripheral rim of the lower rotor plate  51   a  with neighboring the notch  51   e  and is formed in a single block with the lower rotor  51  along the outer peripheral of the lower rotor plate  51   a.    
         [0050]     The gear  51   f  is an engaged portion for opening/closing the shutter  4  (see  FIG. 2A ) from outside of the magnetic disk cartridge  1  and is formed at a peripheral rim of the lower rotor plate  51   a  within a predetermined range with neighboring the shutter plate  51   b . The gear  51   f  matches with the shutter open gear  67  (see  FIG. 2A ) which is an example of the shutter open/close supporting portion  68  and has a function to transmit a motion by changing the linear motion of setting or ejecting the recording disk cartridge  1  to a magnetic disk drive which is not depicted in figures in a rotational motion for the shutter  4 .  
         [0051]     The upper rotor  52  is designed to be substantially symmetric to the lower rotor  51 : the upper rotor  52  comprises an upper rotor plate  52   a  similar to the lower rotor plate  51   a ; on the upper rotor plate  52   a  are formed a central opening  52   c  fitting outside the rib  37  of the upper plate  30 , a notch  52   e  corresponding to the depression  34  and a rib  52   d  corresponding to the upper rotor support groove  38 . In addition, at a portion adjacent to the notch  52   e  of a peripheral rim of the upper rotor plate  52   a  is formed a shutter groove  52   b , corresponding to the shutter plate  51   b  of the lower rotor  51 . The shutter guiding groove  52   b  has a fitted portion  52   f  and receiving opening portion  52   g  as shown in  FIG. 7 . The fitted portion  52   f  has substantially same shape as the edge portion  51   h  of the shutter plate  51   b  which is particularly a rectangular shape. The receiving opening portion  52   g  is formed in a shape that the enter direction for the shutter guiding groove has the wider groove than the reverse direction and particularly has a chamfer cutting shape of the opening portion  52   g . By mating the shutter guiding groove  52   b  with the edge portion  51   h  of the shutter plate  51   b , the lower rotor  51  and the upper rotor  52  is coupled via the shutter plate  51   b  and is integrally rotated by a shutter open/close mechanism as discussed later.  
         [0052]     The upper rotor  52  is rotationally freely supported by the upper plate  30  by the central opening  52   c  fitting outside the rib  37  of the upper plate  30  and the rib  52   d  engaging in the upper rotor support groove  38 . Meanwhile, the upper rotor  52  is prevented from dropping from the upper plate  30  by a stop member  53 . The stop member  53  comprises a cylindrical portion  53   a  inserted in the rib  37  (see  FIG. 3 ) and a flange  53   b  formed at one end of the cylindrical portion  53   a ; the cylindrical portion  53   a  is inserted in the central opening  52   c  from a lower side of the upper rotor  52  and is fixed at the rib  37  by ultrasonic welding, adhesion and the like.  
         [0053]     As an enlarged section drawing shown in  FIG. 5 , an upper face of the lower rotor  51 , upper and lower faces of the inner plates  20  and a lower face of the upper rotor  52  are faces opposing the magnetic disk media  41 , where liners  49  are affixed across portions opposing the media  41 , respectively.  
         [0054]     The liners  49  consist of, for example, a non-woven cloth such as a polyester fiber and a blended fabric fiber of rayon and polyester.  
         [0055]     Next will be described a stack structure of the lower plate  10 , the inner plates  20  and the upper plate  30 .  
         [0056]     In the rib  12  of the lower plate  10 , as shown in  FIG. 5 , an inside thereof is formed higher by one step than an outside thereof and thereby a male type step portion  12   a  is formed; each rib  22  of the inner plates  20  forms a female type step portion  22   a  protruding downward at outermost periphery and thus a periphery of the male type step portion  12   a  and an inner perimeter of the female type step portion  22   a  become able to be fitted. In addition, when the lower plate  10 , the inner plates  20  and the upper plate  30  are fastened by the screws  91  (see  FIG. 1 ), an upper face of the male type step portion  12   a  and a corresponding portion of a lower face of the lowermost inner plate  20  are designed to be contacted. Thus, because the rib  12  of the lower plate  10  and the rib  22  of the inner plate  20  are sealingly abutted and fitted each other, an invasion of dust into the cartridge case  2  from outside is prevented.  
         [0057]     Similarly, any adjacent two of the inner plates  20  and the uppermost inner plate  20  and the upper plate  30  are stacked by being sealingly abutted and fitted each other. In other words, on an upper face of each of the inner plates  20  is formed a male type step portion  22   b  where an inside of the upper face is formed higher by one step; at a rib  32  of the upper plate  30  is formed a female type step portion  32   a  of which outermost periphery protrudes downward by one step. And the male type step portion  22   b  of one inner plate  20  and the female type step portion  22   a  of an upper adjacent inner plate  20  are sealingly abutted and fitted each other; the male type step portion  22   b  of the uppermost inner plate  20  and the female type step portion  32   a  of the upper plate  30  are sealingly abutted and fitted, and stacked. Thus any adjacent two of the ribs  12 ,  22 ,  32  are sealingly abutted and fitted each other and dust from outside is prevented from invading into the cartridge case  2 . In addition, as soon as the lower plate  10 , the inner plates  20  and the upper plate  30  are stacked, the side wall  13  of the cartridge case  2  is configured.  
         [0058]     In addition, both of the female type step portion  22   a  and the male type step portion  22   b  protrude from the main plate  21  beyond a thickness of the liner  49 . Therefore, after affixing the liners  49  on the inner plates  20  and making an assembly, then even if placing it on a work bench, the liners  49  do not contact the work bench and accordingly, are not contaminated with dust and the like.  
         [0059]     Such the configuration of the cartridge case  2  by stacking the inner plates  20  facilitates a change of a number of the magnetic disk media  41 ; although a height change of the side wall  13  and that of the shutter plate  51   b  are requested, a number of housing units of the magnetic disk media  41  formed within the cartridge case  2  can be changed only by mainly changing a number of the inner plates  20 .  
         [0060]     Next will be described the magnetic disk media  41  and a stack structure thereof. The magnetic disk media  41  are ones where magnetic paint is coated on both faces of a resin sheet, for example, such as polyester.  
         [0061]     As shown in  FIG. 6 , each of the center cores  42  is one substantially made a hat form with draw forming a metal plate by press: the center core  42  is mainly configured of a circular bottom plate  42   a , a low cylindrical side wall  42   b  rising from peripheral rim of the bottom plate  42   a  and a flange  42   c  widening in an outer diameter direction from an upper end of the side wall  42   b . At center of the bottom plate  42   a  is formed a center hole  42   d  and at rim of the plate  42   a  are formed six small holes  42   e  at a distance of 60 degrees, making the center hole  42   d  a center thereof.  
         [0062]     A spacer  43  is provided between adjacent center cores  42 , keeps a distance of each of the center cores  42 , stops a rotation between each of the center cores  42 , and functions so that the stacked magnetic disk media  41  integrally rotate. The spacer  43  is mainly configured of a main body portion  43   a  shaped like a ring from a resin and metallic pins  43   b  pressed into the main body portion  43   a . In the main body portion  43   a  are formed six penetration holes h at positions corresponding to the small holes  42   e  of the center core  42 , wherein each of the penetration holes h consists of a small diameter hole portion  43   c , where the pin  43   b  is pressed and a large diameter hole portion  43   d  that is coaxial with and slightly larger in diameter than the small diameter hole portion  43   c . The six penetration holes h are designed to be upside down in any two adjacent ones. In other words, penetration holes h 2  of both adjacent penetration holes h 1 , where each the large diameter hole portion  43   d  is positioned at an upper side thereof, are arranged so that the large diameter hole portion  43   d  is positioned at a lower side thereof.  
         [0063]     Into each of the small diameter portions  43   c  is pressed each one pin  43   b  from upper/lower sides thereof, one end of the pin  43   b  is positioned at a boundary of the large diameter hole portion  43   d  and the small diameter hole portion  43   c  and the other end thereof protrudes outside the small diameter portion  43   c . The large diameter hole portion  43   d  serves a function of a clearance at ends of pins  43   b  of adjacent spacers  43 .  
         [0064]     As shown in  FIG. 5 , such the spacers  43  are provided between adjacent center cores  42 , respectively. One pin  43   b  protruding toward a lower side of each of the spacers  43  enters in a small hole  42   e  of one center core  42  at the lower side of the spacer  43  and stops a rotation relative to the center core  42  at the lower side. If there is another spacer  43  at a still lower side than the center core  42  at the lower side, a floating-up of the spacer  43  for the center core  42  is prevented by the pin  43   b  entering the large diameter hole portion  43   d  in the spacer  43  at the lower side. The other pin  43   b  protruding toward an upper side of the spacer  43  enters in a small hole  42   e  of the other center core  42  at the upper side of the spacer  43  and stops a rotation relative to the center core  42  at the upper side. If there is another spacer  43  at a still upper side than the center core  42  at the upper side, the top end of the pin  43   b  enters in the large diameter hole portion  43   d  in the spacer  43  at the upper side.  
         [0065]     Meanwhile, because at an upper side the uppermost center core  42  has no center core  42  to stop a rotation thereof, at the upper side is arranged a thin top spacer  43 ′ in thickness where the pin  43   b  is protruded only downward.  
         [0066]     The magnetic disk media  41  thus stacked, namely, the disk stack  40 , are stably supported in rotation by a coupling shaft  44 , a bearing ball  45 , a compression coil spring  46  and a center plate  47 .  
         [0067]     As shown in  FIG. 5 , the coupling shaft  44  lessens a central fluctuation between the center cores  42  stacked, holds the bearing ball  45  and the compression coil spring  46  and comprises a shaft portion  44   a , a ball holding portion  44   b  and a spring holding portion  44   c . The shaft portion  44   a  is a columnar form that can be inserted through the center holes  42   d  of the center cores  42 . At an upper end of the shaft portion  44   a  the ball holding portion  44   b  is formed into a cylindrical form with a bottom opening to an upper side thereof. A depth of the ball holding portion  44   b  is larger than a radius of the bearing ball  45  and therefore, the bearing ball  45  is stably held at the ball holding portion  44   b . The spring holding portion  44   c  consists of a form where a cylindrical form with a bottom is turned down at a side of an outer diameter of the ball holding portion  44   b  and the compression coil spring  46  is arranged in a cylindrical space between the shaft portion  44   a  and the spring holding portion  44   c . Meanwhile, although a length of the coupling shaft  44  is arbitrary, in the embodiment it is one reaching the second center core  42  from the lowermost one; the center hole  42   d  of the lowermost center core  42  is opened so that a spindle  65  of a magnetic disk drive can proceed.  
         [0068]     The center plate  47  is a slide member affixed at the center of an inner face of the upper plate  30 , that is, on a flat face of an inside of the rib  37 . The center plate  47  can be composed of, for example, a material excellent in sliding ability and abrasion resistance such as polyoxymethylene and ultra high molecular weight polyethylene.  
         [0069]     Although the bearing ball  45  consists of a sphere made of, for example, steel used for a ball bearing, it may also be composed of a material excellent in sliding ability and abrasion resistance, for example, such as polytetrafluoroethylene and polyoxymethylene. The bearing ball  45  is arranged within the ball holding portion  44   b  of the coupling shaft  44 , abuts with the bottom face of the ball holding portion  44   b ; and a center of an inner face of the upper plate  30 , that is, the center plate  47  by a point contact and rotationally supports the disk stack  40 .  
         [0070]     In the compression coil spring  46  one end (upper end) is held by the spring holding portion  44   c  of the coupling shaft  44 ; the other end (lower end) abuts with an upper face of the uppermost center core  42  and energizes the stacked center cores  42  to the side of the lower plate  10 , that is, to the side of the spindle  65  of the magnetic disk drive. Thus the center cores  42  do not jounce within the cartridge case  2  and the fluctuation of the magnetic disk media  41  is prevented in rotation thereof.  
         [0071]     A magnetic disk drive for recoding/reproducing data for the magnetic disk cartridge  1  rotates, as shown in  FIG. 4 , the disk stack  40  by the spindle  65 . The spindle  65  attracts the lowermost center core  42  by magnetic force, enters in the center hole  42   d  of the center core  42  and thereby matches an axis thereof with that of the disk stack  40 . At this time, because the spindle  65  slightly lifts up the center cores  42  with resisting an energizing force of the compression coil spring  46 , as shown in  FIGS. 4 and 5 , each of the magnetic disk media  41  is positioned at center of a space formed between the lower rotor  51  and the lowermost inner plate  20 , between upper and lower inner plates  20  and between the uppermost inner plate  20  and the upper rotor  52 . The magnetic heads  63  are provided at top ends of swing arms  62 . Each of the magnetic heads  63  is arranged on both faces of each of the magnetic disk media  41 .  
         [0072]     The magnetic disk cartridge  1  thus described can prevent, in no use thereof as shown in  FIG. 2A , an invasion of dust thereto by closing the opening  3  with rotating the shutter  4  in a counterclockwise direction of the drawing; in use thereof as shown in  FIG. 2B , when loaded on the magnetic disk drive, the shutter open gear  67  fits in the groove  13   a , is guided thereby, engages in the gear  51   f  and rotates the shutter  4  in a clockwise direction of the drawing.  
         [0073]     Since the lower rotor  51  on which a gear  51   f  is formed is coupled with the upper rotor  52  via shutter plate  51   b  in this particular case, the shutter  43  integrally rotates in a clockwise in  FIG. 2B . According to this rotation, the shutter plate  51   b  that shuts off the case opening  3  and disk stack  40  moves away from the case opening  3  and then the disk stack  40  is opened.  
         [0074]     In addition, the disk stack  40  rotates by the spindle  65  rotating. After then, the swing arms  62  rotate by being driven with an actuator  61  and each of the magnetic heads  63  are moved onto each face of the magnetic disk media  41 .  
         [0075]     On the other hand, when the recording disk cartridge  1  is ejected from the magnetic disk drive, the shutter open gear  67  to which the gear  51   f  matches moves in a reverse direction to the time of inserting the recording disk cartridge and makes the gear  51   f  rotate counter clockwise in the figure. According to this rotation, the shutter  4  rotates in counter clockwise and the case opening  3  is shut off.  
         [0076]     When recording data on the magnetic disk media  41  with the magnetic heads  63 , the data is recorded thereon by sending a signal to the magnetic heads  63  by a control circuit not shown; when reproducing data from the magnetic disk medium  41 , a signal is output by detecting a change of a magnetic field on the medium  41  with the magnetic heads  63   a.    
         [0077]     At this time, dust on the magnetic disk media  41  is removed by the liners  49  appropriately touching respective media  41 .  
         [0078]     After the use of the magnetic disk cartridge  1 , the magnetic heads  63  are retracted from the cartridge case  2 , thereafter ejects the magnetic disk cartridge  1 ; thereby the gear  51   f  is driven by the shutter open gear  67  and the shutter  4  closes the opening  3 .  
         [0079]     Thus because the magnetic disk cartridge  1  has a plurality of the magnetic disk media  41 , data transfer can be performed at a higher speed by simultaneously accessing data with a plurality of magnetic heads  63 .  
         [0080]     In addition, because the cartridge case  2  is configured by stacking up the inner plates  20 , it is easy to perform a specification change of making a number of magnetic disk media  41  a different one. Then, in assembling the magnetic disk cartridge  1 , because the magnetic disk media  41  can be handled with being placed on the inner plates  20  and the lower rotor  51  built in the lower plate  10 , an occasion of touching the magnetic disk media  41  can be reduced and a quality of the cartridge  1  can be further stabilized.  
         [0081]     In addition, because each of the inner plates  20  is stacked on the lower plate  10  or another inner plate  20  and is fixed, the magnetic disk cartridge  1  can make it higher a parallelism to the magnetic disk media  41 , can stabilize a rotation of the media  41  and enable a higher speed rotation of the media  41 , furthermore a higher speed of a data transfer.  
         [0082]     Another embodiment of the present invention is discussed with the figures.  FIG. 7  and  FIG. 8  shows cross sectional views of the matching of the shutter plate and the upper rotor.  FIG. 7  shows the embodiment previously provided and  FIG. 8  shows another embodiment.  
         [0083]     The shutter plate  51   b  in this embodiment has a sealing off portion  51   i  that shuts off between the case opening  3  (see  FIG. 2A ) and the disk stack  40  and has an edge portion  51   h  mating with the shutter guiding groove  52   b  formed in the upper rotor  52 . The edge portion  51   h  has a shape of sharpening towards the edge, which is a chamfer cutting shape for this particular case. It is preferable that the shutter guiding groove  52   b  has wider groove in the enter portion  52   g  to the edge portion  51   h  in addition.  
         [0084]      FIG. 9  shows a section view of the mating of the parts composing the shutter regarding another embodiment. As shown in  FIG. 9 , the shutter  4  is composed of the lower rotor  51 , the upper rotor  52  and the shutter plate  51   b  which are all independent components but are mutually mating. On the lower rotor  51 , a shutter guiding groove  51   m  is formed at the position facing against the shutter guiding groove  52   b  formed in the upper rotor  52 . The edge portion  51   k  of the shutter plate  51   b  and the shutter guiding groove  51   m  formed in the lower rotor  51  are fitted, the edge portion  51   h  of the shutter plate  51   b  and the shutter groove  52   b  are fitted and ultimately construct the shutter  4 . The shutter guiding grooves  51   m  and  52   b  are preferred to have wide opening at the enter portion and it is preferred that the edges  51   h  and  51   k  are formed in a sharpen shape as shown in  FIG. 8 .  
         [0085]      FIG. 10  shows an external perspective view of the recording disk cartridge which is closed, particularly, another embodiment of the mating portion of the shutter open/close mechanism. As shown in  FIG. 10 , the mating portion of another embodiment is not confined in the gear  51   f  as previously described but can be formed with high friction material such as rubber material as a rubber piece  51   g . In this particular embodiment, a rubber piece  51   g  is fixed with an adhesive in the predetermine range adjacent to the shutter plate  51   b  in the peripheral of the lower rotor plate  51   a  (see  FIG. 1 ). When the mating portion is made of the rubber piece  51   g  as shown in  FIG. 10 , a shutter open/close supporting portion  68 ′ of which surface is roughed at the part with which the rubber piece  51   g  mates the shutter open/close supporting portion  68  formed in the disk drive is preferably used. The present embodiment has the mating portion in the lower rotor  51  but can have it in the upper rotor  52 .  
         [0086]      FIG. 11A  and  FIG. 11B  are perspective views that show the inner surface of the upper plate.  FIG. 11A  shows the relation between the upper rotor and the upper plate.  FIG. 11B  shows another embodiment wherein the upper rotor is stopped on the upper plate. As shown in  FIG. 11A  and  FIG. 11B , a stopping salient  54  which is another embodiment of the stopper is formed in a single block. The rib, called a stopping salient  54  in these particular embodiments, is a variation of the rib and can be an alternative technology to the ribs  17  and  37 . The stopping salient  54  is a projected portion of an annular which has an insertion portion  54   a , a stopper portion  54   b  and a notch portion  54   c  that has no insertion portion  43   a  or stopper portion  54   b  therein. The insertion portion  54   a  is formed in a taper shape such that the outer diameter gradually becomes large against the upper plate  30  and the insertion portion  54   a  is easily fitted to the central opening  52   c . The stopping salient  54  is easily deformed when the central opening  52   c  is pressed to the insertion portion  54   a  since the notch  54   c  is made. The central opening is fitted to the stopping salient  54  so that the upper rotor  52  is not dropped off from the upper plate  30 .  
         [0087]     Thus, although the embodiment of the present invention is described, the invention is not limited thereto and can be embodied with being changed as needed. For example, although in the embodiment the magnetic disk medium  41  is applied to a recording disk medium, an optical recording medium where data is recorded by light can also be applied thereto.  
         [0088]     In addition, although in the embodiment the lower plate  10 , the inner plates  20  and the upper plate  30  are fastened and fixed by the screws  91 , they can also be integrally fixed by any of adhesion and deposition.