Patent Publication Number: US-2007109685-A1

Title: Recording disk cartridge

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims the foreign priority benefit under Title 35, United States Code, §119(a)-(d) of Japanese Patent Application No. 2005-331723, filed on Nov. 16, 2005 in the Japan Patent Office, the disclosure of which is herein incorporated by reference in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to a recording disk cartridge, and more specifically, to a recording disk cartridge including a recording disk medium and a cartridge case which contains the recording disk medium.  
      2. Description of the Related Art  
      Conventionally, a recording disk cartridge is well-known which contains a recording disk medium such as a flexible magnetic disk medium with magnetic layers on both surfaces of a discoid support medium made of a polyester sheet or the like, an optical recording disk medium, a phase change disk medium, and so on in a cartridge case.  
      For instance, a conventional recording disk cartridge described in U.S. Pat. No. 6,256,168 is well known.  
      As shown in  FIGS. 10A and 10B , the recording disk cartridge  800  described in U.S. Pat. No. 6,256,168 mainly includes a cartridge case  810 , a rotary shutter  820  turnably provided inside the cartridge case  810 , and a recording disk medium  830  rotatably provided inside the rotary shutter  820 . The recording disk medium  830  includes a discoid flexible disk  831  and a hub  832  which supports the flexible disk  831 . The recording disk cartridge  800  is mounted in a dedicated drive unit (not shown) before use.  
      The cartridge case  810  includes an upper shell  811  and a lower shell  812 . An opening for access  813 , which is wedge-shaped in a plane view, is formed so that a head of the drive unit can access the recording disk medium  830  when the recording disk cartridge  800  is mounted in the drive unit.  
      Moreover, a hub hole  815  is formed in the lower shell  812  so that a spindle of the drive unit can chuck the hub  832  when the recording disk cartridge  800  is mounted in the drive unit.  
      The rotary shutter  820  includes an upper shutter  823  and a lower shutter  824  which are discoid in shape. In each of the upper shutter  823  and the lower shutter  824 , a notch  821  is formed so as to cause the recording disk medium  830  to be exposed outside through an opening for access  813 .  
      Moreover, the rotary shutter  820  is turnably attached to the upper shell  811  of the cartridge case  810  so as to turn between a close position and an open position. When the rotary shutter  820  is located in the close position, the opening for access  813  of the cartridge case  810  is covered by a portion of the rotary shutter  820  except the notch  821 . Therefore, the recording disk medium  830  is not exposed outside. When the rotary shutter  820  is located in the open position, the notch  821  of the rotary shutter  820  matches and aligns with the opening for access  813  of the cartridge case  810 . Therefore, the recording disk medium  830  is exposed outside through both of the opening for access  813  and the notch  821 . The rotary shutter  820  is pushed by a spring, which is not shown, to be located in the close position when the recording disk cartridge  1  is not mounted in the drive unit and in the open position when the recording disk cartridge  1  is mounted in the drive unit.  
      In addition, the rotary shutter  820  has a shutter hub hole  822  to cause the hub  832  to be exposed outside thorough the hub hole  815  of the cartridge case  810 . The shutter hub hole  822  of the rotary shutter  820  matches and aligns with the hub hole  815  of the cartridge case  810 . Therefore, a lower surface of the hub  832  is exposed outside through the shutter hub hole  822  and the hub hole  815 .  
     SUMMARY OF THE INVENTION  
      In the above-mentioned recording disk medium  830 , as recording density increases year by year, a recording track width is getting narrower while a recording length is getting shorter. Therefore, in the magnetic disk cartridge, a read error easily occurs due to a very little dust between the magnetic disk medium and the magnetic head.  
      In view of the above, in the conventional recording disk cartridge  800 , the opening for access  813  of the cartridge case  810  is covered by the rotary shutter  820  so that dust is prevented from entering the cartridge case  810  through the opening for access  813  when the recording disk cartridge  800  is not mounted in the drive unit.  
      The hub hole  815  of the cartridge case  810  is formed larger than the hub  832  of the recording disk medium  830  so that the hub  832  can move inside the hole  815 . Accordingly, position of the hub  832  can be easily adjusted corresponding to position of the spindle of the drive unit when the spindle chucks the hub  832 .  
      Thus, in the conventional recording disk cartridge  800 , there is a space S between the hub hole  815  and the hub  832  since the hub hole  815  is larger than the hub  832 . As a result, there is a problem that dust enters the cartridge case  810  through the space S.  
      In view of the above, it is an object of the present invention to provide a recording disk cartridge which minimizes dust entering a cartridge case.  
      To solve the problem, in one aspect of the present invention, there is provided a recording disk cartridge including a recording disk medium, a cartridge case which contains the recording disk medium and has a case opening to cause the recording disk medium to be exposed outside, and a rotary shutter which turns between the recording disk medium and the cartridge case in order to open and close the case opening. In the cartridge case, a hub hole is formed so as to cause a hub which supports the recording disk medium to be exposed outside. Moreover, a hub hole shutter includes a shutter in which one edge is pivoted on an inner surface of the cartridge case and a fitting portion is formed on another edge to fit with the hub. The shutter of the hub hole shutter engages with the rotary shutter and turns in synchronization with turning of the rotary shutter so as to open and close a space between the hub hole and the hub.  
      As described above, the recording disk cartridge includes the hub hole shutter having a shutter which turns in synchronization with turning of the rotary shutter to open and close the space between the hub hole of the cartridge case and the hub of the recording disk medium. The shutter closes the space between the hub hole and the hub when the rotary shutter closes the case opening. On the other hand, the shutter opens the space when the rotary shutter opens the case opening. As a result, when the recording disk cartridge is not mounted in the drive unit, the space between the hub hole and the hub can be covered by the hub hole shutter. Therefore, it is possible to prevent dust from entering the cartridge case through the space.  
      In the recording disk cartridge, the hub hole shutter may include a plurality of shutters. The one edge of each of the shutters is respectively pivoted on the cartridge case. In addition, the other edges of the shutters together surround the hub so as to close the space between the hub hole and the hub.  
      Thus, the plurality of shutters can together surround the hub so as to exactly close the space between the hub hole and the hub. In addition, each of the shutters is individually pivoted on the cartridge case. Therefore, shutters can be supported without overlap to open and close the space between the hub hole and the hub. As a result, the hub hole shutter can be thin so as to be employed for a thin recording disk cartridge.  
      In the recording disk cartridge, a slot in which a protrusion of the rotary shutter is inserted and engaged is formed in the shutter of the hub hole shutter.  
      Thus, the protrusion on the rotary shutter is inserted and engaged in the slot formed in the shutter so that the shutter can easily and exactly engage with the rotary shutter and the shutter can turn exactly in synchronization with turning of the rotary shutter.  
      In the recording disk cartridge, in the shutter of the hub hole shutter, a side of the other edge may be inclined toward the rotary shutter.  
      Thus, the side of the other edge in the shutter is inclined toward the rotary shutter so as to cause the side of the other edge in the shutter to approach the rotary shutter. Accordingly, the protrusion of the rotary shutter is inserted deep in the slot in the side of the other edge. Therefore, it is possible to prevent the protrusion of the rotary shutter from being detached from the slot in the side of the other edge which is free and shaky. Accordingly, the shutter can exactly turn.  
      In the above-mentioned recording disk cartridge, in the shutter of the hub hole shutter, an axis hole is formed in the one edge. An axis is protruded from an inner surface of the cartridge case by means of a burring process and inserted into the axis hole. Then, an end of the axis is crimped.  
      Thus, the shutter is supported by the cartridge case. Therefore, it is not required to attach an axis as a separate part to support the shutter. As a result, the shutter can be easily attached.  
      In the recording disk cartridge, the hub hole shutter may include a first shutter and a second shutter. The slots of the first shutter and the second shutter may be shaped in an arc whose centers are displaced from the turn center of the rotary shutter. In the slot of the first shutter, a side of the other edge may curve in a direction from the turn center of the rotary shutter toward outside.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other aspects, other advantages and further features of the present invention will become more apparent by describing in detail illustrative, non-limiting embodiments thereof with reference to the accompanying drawings, in which:  
       FIG. 1A  is a perspective view from the upper front side showing a recording disk cartridge according to the present embodiment;  
       FIG. 1B  is a perspective view from the lower rear side showing the recording disk cartridge according to the present embodiment;  
       FIG. 2  is an exploded perspective view of the recording disk cartridge according to the present embodiment;  
       FIG. 3A  is a perspective view from the upper front side showing a rotary shutter according to the present embodiment;  
       FIG. 3B  is a perspective view from the lower rear side showing the rotary shutter according to the present embodiment;  
       FIG. 4  is a plan view from the lower side showing the recording disk cartridge according to the present embodiment;  
       FIG. 5  is a perspective view showing the recording disk cartridge according to the present embodiment inserted in the drive unit;  
       FIG. 6A  is a plan view from the lower side showing a closed hub hole shutter in the recording disk cartridge according to the present embodiment;  
       FIG. 6B  is a plan view from the lower side showing an open hub hole shutter in the recording disk cartridge according to the present embodiment;  
       FIG. 7A  is a side sectional view showing a hub hole shutter in the recording disk cartridge according to the present embodiment;  
       FIG. 7B  is a side sectional view showing how the hub hole shutter is attached in the recording disk cartridge according to the present embodiment;  
       FIG. 8  is a plan view from the lower side showing how the hub hole shutter opens in the recording disk cartridge according to the present embodiment;  
       FIG. 9  is a side sectional view showing the hub hole shutter in the recording disk cartridge according to another embodiment;  
       FIG. 10A  is a perspective view from the upper front side showing a conventional recording disk cartridge; and  
       FIG. 10B  is a perspective view from the lower rear side showing a conventional recording disk cartridge. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Here will be described embodiments of the present invention in detail, referring to the accompanying drawings as needed.  
      In the embodiment, directions will be described in accordance with front, rear, right, left, upper, and lower directions shown in  FIGS. 1A and 1B .  
      &lt;&lt;Constitution of Recording Disk Cartridge  1 &gt;&gt; 
      As shown in  FIGS. 1A, 1B , and  2 , a recording disk cartridge  1  according to the present embodiment mainly includes a cartridge case  10 , a rotary shutter  20  provided turnably inside the cartridge case  10 , a recording disk medium  30  provided rotatably inside the rotary shutter  20 , a hub hole shutter  40  provided under the rotary shutter  20  inside the cartridge case  10 . Thus, the recording disk cartridge  1  is inserted in a dedicated drive unit D (See  FIG. 5 ) from the front side before use.  
      &lt;Cartridge Case  10 &gt; 
      As shown in  FIGS. 1A and 1B , a cartridge case  10  is a thin box case to contain the recording disk medium  30 . In the cartridge case  10 , a front edge  10   a  is formed in an arc (an arch) shape in a plane view while a rear edge  10   b , a right edge  10   c , and a left edge  10   d  are formed substantially linearly in a plane view. The center of the rear edge  10   b  bulges backward a little compared with the right and left sides so that the recording disk cartridge  1  can be easily held when it is taken out of the drive unit D (See  FIG. 5 ).  
      Moreover, the cartridge case  10  has an opening for access  101  (a case opening) which is a notch formed in a wedge shape (a substantial sector with central angle of substantially 90°) in a plane view. Through the opening for access  101 , the recording disk medium  30  in the cartridge case  10  is exposed outside. The opening for access  101  is formed in a shape which does not interfere with operation of a swing arm SA of the drive unit D (See  FIG. 5 ).  
      As shown in  FIG. 2 , the cartridge case  10  includes a metal upper shell  11  and a metal lower shell  12  which face each other, and plastic frame members  13  placed between the upper shell  11  and the lower shell  12 .  
      [Upper Shell  11  and Lower Shell  12 ] 
      The upper shell  11  mainly forms an upper wall of the cartridge case  10  while the lower shell  12  mainly forms a lower wall of the cartridge case  10 . For instance, a metal plate such as a stainless steel is punched out and bent as described later to form the upper shell  11  and the lower shell  12  in predetermined shapes.  
      An opening for access  111  which is a wedge-shaped notch in a plane view is formed in the front left side in the upper shell  11 .  
      Similarly, an opening for access  121  which is a wedge-shaped notch in a plane view is formed in the front left side in the lower shell  12 . Thus, the opening for access  111  and the opening for access  121  together form the above-mentioned opening for access  101  of the cartridge case  10 .  
      On the right side of the upper shell, a bent portion  112   c  which is bent linearly in a plane view is formed integrated with the upper shell by means of a bending process of a metal plate. Also, on the left side of the upper shell, a bent portion  112   d  is formed. Similarly, bent portions  122   c  and  122   d  are respectively formed on the right and left sides of the lower shell  12 .  
      Thus, when the cartridge case  10  is assembled, the bent portions  112   c  and  122   c  overlap to form a part of a peripheral wall on the right edge  10   c  of the cartridge case  10 . Similarly, the bent portions  112   d  and  122   d  overlap to form a part of a peripheral wall on the left edge  10   d.    
      In addition, an engaging hole  113  is formed in the center of the upper shell  11  to engage with a center pin  50  which pivots the rotary shutter  20  turnably.  
      On the other hand, a hub hole  123  is formed in the center of the lower shell  12  to cause the hub  32  of the recording disk medium  30  to be exposed outside. Thus, when the recording disk cartridge  1  is mounted in the drive unit D, a spindle (not shown) of the drive unit D chucks (engages in) the hub  32  through the hub hole  123 .  
      Moreover, the lower shell  12  has a guide hole  124  which is formed along a path of the shutter knob  24  of the rotary shutter  20 , and two turn axes  125   a  and  125   b  which protrude inside (toward the side of the recording disk medium  30 ) to pivot the hub hole shutter  40 .  
      [Frame Members  13 ] 
      As shown in  FIG. 2 , the frame members  13  includes an arch frame  131  which mainly forms a peripheral wall on the front edge  10   a  (See  FIG. 1 ), a base frame  132  which mainly forms a peripheral wall on the rear edge  10   b  (See  FIG. 1 ), a V notch member  133  which mainly forms a part of the front side in the peripheral wall on the left edge  10   d.    
      A wall&#39;s inner surface  131   a  (a surface in the side of the recording disk medium  30 ) of the arch frame  131  is formed in an arc shape along a contour of the rotary shutter  20 . Meanwhile, a wall&#39;s outer surface  131   b  (an outer surface of the recording disk cartridge  1 ) of the arch frame  131  is formed in an arc shape in a plane view along a contour of the front edge  10   a  of the cartridge case  10 .  
      Similarly, a wall&#39;s inner surface  132   a  (a surface in the side of the recording disk medium  30 ) of the base frame  132  is formed in an arc shape along a contour of the rotary shutter  20 . Meanwhile, a wall&#39;s outer surface  132   b  (an outer surface of the recording disk cartridge  1 ) of the base frame  132  is formed substantially linearly in a plane view along a contour of the rear edge  10   b  of the cartridge case  10 .  
      Moreover, the arch frame  131  has an engaging groove  131   e  (See  FIG. 4 ) which opens downward and links inside and outside of the cartridge case  10 . A lock piece  70 , which will be described later, engages in the engaging groove  131   e.    
      The V notch member  133 , which is placed in the front side in the left edge  10   d , serves as a stopper to stop the rotary shutter  20  in the close position (See  FIG. 4 ), as well as an engaging portion to engage with the drive unit D. The rotary shutter  20  is pushed to the closing direction as described later.  
      The upper shell  11  and the lower shell  12  are respectively fixed to the frame members  13  by means of a publicly known technology. For instance, the following methods are used to attach the upper shell  11  and the lower shell  12  to the frame members  13 . (1) Bosses are provided in the frame members  13 ; boss holes are provided in the upper shell  11  and the lower shell  12 ; the bosses are inserted into the boss holes; and ends of the bosses are crimped. (2) The upper shell  11  and the lower shell  12  are bonded with the frame members  13  using adhesive.  
      &lt;Rotary Shutter  20 &gt; 
      The rotary shutter  20 , which is formed in a hollow substantially cylindrical shape, opens and closes the opening for access  101  (See  FIG. 1 ). Thus, the recording disk medium  30  is rotatably provided inside the hollow in the rotary shutter  20  (See  FIGS. 3A, 3B , and  7 A).  
      As shown in  FIGS. 2, 3A , and  3 B, the rotary shutter  20  has a notch  201  which causes the recording disk medium  30  to be exposed outside (See  FIGS. 3A and 3B ). The notch  201  is formed in the substantially same shape with the opening for access  101  of the cartridge case  10 .  
      Moreover, the rotary shutter  20  is rotatably attached near a center of the upper shell  11  with a center pin  50 .  
      More specifically, as shown in  FIGS. 5 and 6 A, when the rotary shutter  20  is located in the close position, the notch  201  of the rotary shutter  20  circumferentially shifts from the opening for access  101  of the cartridge case  10 . Therefore, the rotary shutter  20  closes the opening for access  101  of the cartridge case  10 .  
      On the other hand, as shown in  FIGS. 5 , and  6 B, when the rotary shutter  20  is located in the open position, the notch  201  matches and aligns with the opening for access  101  in the thickness direction of the recording disk cartridge  1  (the axial direction of the recording disk medium  30 ). Accordingly, the rotary shutter  20  opens the opening for access  101 . When the opening for access  101  is opened in this way, the recording disk medium  30  is exposed outside.  
      The rotary shutter  20  is pushed to the closing direction (See Arrow A 1  in  FIG. 4 ) by a pushing means (for instance, a spring), which is not shown. Then, in a normal state before the recording disk cartridge  1  is inserted in the drive unit D, the rotary shutter  20 , which is pushed to the closing direction, touches the V notch member  133  in the circumferential direction. Therefore, the rotary shutter  20  is located in the close position so as to close the opening for access  101  (See  FIGS. 1A, 1B ,  4 , and  5 ). By the way, the pushing means is not always necessary in the invention. As described later, a stopping means (a shutter knob stopper D 1 ) to stop the shutter knob  24  may be provided in the drive unit D. Then, when the recording disk cartridge  1  is taken out of the drive unit D (See  FIG. 5 ), the rotary shutter  20  turns in the closing direction A 1 . Therefore, the pushing means can be omitted.  
      As shown in  FIGS. 2, 3A , and  3 B, the rotary shutter  20  includes an upper shutter  21  and a lower shutter  22  which are made of a metal plate, and a plastic shutter wall  23  between the upper shutter  21  and the lower shutter  22 .  
      [Upper Shutter  21  and Lower Shutter  22 ] 
      The upper shutter  21  which forms an upper wall of the rotary shutter  20  has a wedge-shaped notch  211 . The lower shutter  22  which forms a lower wall of the rotary shutter  20  has a wedge-shaped notch  221 .  
      In addition, the notch  211  and the notch  221  form a notch  201  of the rotary shutter  20  (See  FIG. 3 ).  
      The upper shutter  21  has in the center an insert hole  212  through which the center pin  50  is inserted.  
      The lower shutter  22  has in the center a shutter hub hole  222  so as to cause the hub  32 , which will be described later, of the recording disk medium  30  to be exposed outside.  
      Moreover, an engaging protrusion (a protrusion)  223   a  which engages in an engaging slot (a slot)  413  of the hub hole shutter  40 , and an engaging protrusion (a protrusion)  223   b  which engages in an engaging slot (a slot)  423  of the hub hole shutter  40 , are formed in a side of a lower shell in the lower shutter  22 . Thus, the hub hole shutter  40  turns in synchronization with turning of the rotary shutter  20  since the engaging protrusions  223   a  and  223   b  respectively engage in the slots  413  and  423 .  
      A shutter knob  24  which turns the rotary shutter  20  is attached to a lower surface of the lower shutter  22  (See  FIG. 3B ). The shutter knob  24  (See  FIG. 1B ) protrudes from the lower surface of the recording disk cartridge  1  through the guide hole  124  formed in the lower shell  12  of the cartridge case  10 . Thus, when the recording disk cartridge  1  is inserted in the drive unit D, the shutter knob stopper D 1  of the drive unit D stops the shutter knob  24  (See  FIG. 5 ).  
      Moreover, as shown in  FIGS. 3A, 3B , and  4 , the lower shutter  22  includes a lock piece  70  (a lock mechanism) which is integrated with the lower shutter  22  and a part of which is bent toward upper side. The lock piece locks the rotary shutter in the close position in the normal state before the recording disk cartridge is inserted. More specifically, the lock piece  70  is a long metal piece which extends from a side surface of the lower shutter  22  getting gradually further in an outer radial direction. An end  71  of the lock piece  70  is a little bent in an inner radial direction.  
      Accordingly, as shown in  FIG. 4 , in the normal state before the recording disk cartridge  1  is inserted in the drive unit D, the rotary shutter  20  is located in the close position and the end  71  of the lock piece  70  engages in an engaging groove  131   e  of an arch frame  131  so that the rotary shutter  20  cannot turn.  
      Moreover, the end  71  of the lock piece  70  faces the right side of the recording disk cartridge  1  through the engaging groove  131   e . Therefore, when the recording disk cartridge  1  is inserted in the drive unit D (See  FIG. 6 ), an unlock pin (not shown) in the drive unit D pushes the end  71  of the lock piece  70  in the inner radial direction (See Arrow A 6  in  FIG. 4 ). Then, the lock piece  70  is released from the engaging groove  131   e  so that the rotary shutter  20  can turn.  
      [Shutter Wall  23 ] 
      The shutter wall  23  forms a peripheral wall of the rotary shutter  20 . As shown in  FIG. 2 , the shutter wall  23  is a resinous component which is formed in C-shape in a plane view and in which a portion corresponding to the notch  201  of the rotary shutter  20  is cut out. Moreover, the upper shutter  21  and the lower shutter  22  are respectively attached on upper and lower sides of the shutter wall  23  by an appropriate means similarly to the cartridge case  10 . Thus, the shutter wall  23  is placed between the upper shutter  21  and the lower shutter  22  so as to form a space to contain the recording disk medium  30 .  
      &lt;Recording Disk Medium  30 &gt; 
      In the embodiment, as shown in  FIG. 2 , the recording disk medium  30  is a recording medium which stores data and includes a flexible disk  31  and a hub  32  to support the flexible disk  31 .  
      The flexible disk  31  includes a discoid support medium made of, for instance, a polyester sheet or the like and recording layers such as magnetic layers formed on both surfaces of the support medium.  
      As shown in  FIG. 7A , the hub  32  is a metallic cylindrical component which supports the flexible disk  31 . Moreover, the hub  32  includes an attachment  322  in the upper surface to attach the flexible disk  31  and a chuck  321  in the lower surface to chuck the spindle (not shown) of the drive unit D (See  FIG. 5 ). The lower portion of the hub  32  protrudes outside through the hub hole  123  which is formed in the lower shell  12 .  
      &lt;Liners  60 &gt; 
      As shown in  FIG. 2 , liners  60  and  60 , which are formed of, for instance, nonwoven fabric or the like, clean up and protect the recording disk medium  30 . The liners  60  and  60  are respectively placed on sides of the flexible disk  31  (the recording disk medium  30 ) of the upper shutter  21  and the lower shutter  22  and bonded with the upper shutter  21  and the lower shutter  22  through adhesive layers (not shown).  
      &lt;Hub Hole Shutter  40 &gt; 
      As shown in  FIGS. 6A and 6B , the hub hole shutter  40  opens and closes a space S (See  FIG. 5 ) between the lower shell  12  and the hub  32  in synchronization with opening and closing of the opening for access  101  by the rotary shutter  20 . The hub hole shutter  40  includes a first shutter (a shutter)  41  and a second shutter (a shutter)  42  provided on the both sides of the hub  32  between the lower surface of the rotary shutter  20  and the inner surface of the lower shell  12 . The first shutter  41  and the second shutter  42  turn in synchronization with turning of the rotary shutter  20  so as to open and close the space S between the lower shell  12  and the hub  32 .  FIG. 6A  shows a state where the first shutter  41  and the second shutter  42  close while  FIG. 6B  shows a state where the first shutter  41  and the second shutter  42  open.  
      As shown in  FIG. 6A , the first shutter  41  and the second shutter  42  are tabular components shaped in a semicircle in a plane view. The first shutter  41  has an axis hole  411  on one edge  41   a . Similarly, the second shutter  42  has an axis hole  421  on one edge  42   a . Thus, the turn axis  125   a  provided in the inner surface of the lower shell  12  is inserted in the axis hole  411 . Similarly, the turn axis  125   b  provided in the inner surface of the lower shell  12  is inserted in the axis hole  421 .  
      Accordingly, the first shutter  41  and the second shutter  42  are respectively pivoted on the turn axes  125   a  and  125   b  of the cartridge case  10 . Thus, the first shutter  41  and the second shutter  42  are individually pivoted on the cartridge case  10 .  
      The turn axes  125   a  and  125   b  are cylindrical axes which are protruded from the inner surface of the lower shell  12  by means of a burring process and formed in the right rear side in the lower shell  12  (See  FIG. 2 ).  
      As shown in the left half in  FIG. 7B , to attach the first shutter  41 , the turn axis  125   a  of the lower shell  12  is inserted into the axis hole  411  formed in the one edge  41   a . Then, as shown in the right half in  FIG. 7B , the end of the turn axis  125   a  is crimped so that the first shutter  41  is loosely supported by the turn axis  125   a . Similarly, the second shutter  42  shown in  FIG. 6A  is also supported by the turn axis  125   b  of the lower shell  12 .  
      Heights of the turn axes  125   a  and  125   b  before a crimping-process are preferably 1.5-3 times, and more preferably 1.5-2 times of mean thicknesses of the first shutter  41  and the second shutter  42  to attain sufficient crimping area and strength.  
      Moreover, as shown in  FIG. 6A , in the other edge  41   b , the first shutter  41  has a fitting portion  412  which is a hemicycle notch and fits with the lower portion (See  FIG. 7A ) of the hub  32  protruding through the hub hole  123  of the lower shell  12 . Similarly, the second shutter  42  has a fitting portion  422  in the other edge  42   b . Thus, in the normal state before the recording disk cartridge  1  is inserted in the drive unit D, the first shutter  41  and the second shutter  42  together surround the hub  32  from both sides to close the space S.  
      In addition, in the first shutter  41 , an engaging slot  413  in which an engaging protrusion  223   a  in the lower surface of the lower shutter  22  engages is formed along from the one edge  41   a  to the other edge  41   b.    
      Similarly, in the second shutter  42 , an engaging slot  423  in which an engaging protrusion  223   b  in the lower surface of the lower shutter  22  engages is formed along from the one edge  42   a  to the other edge  42   b.    
      Shapes in a plane view of the engaging slots  413  and  423  are designed so that the engaging protrusions  223   a  and  223   b  turn integrally with the rotary shutter  20  so as to cause the first shutter  41  and the second shutter  42  to turn to cause the hub hole shutter  40  to open and close the space S.  
      To be concrete, in the state in  FIG. 6A  where the first shutter  41  and the second shutter  42  are closed, the engaging protrusion  223   a  engages in the end in the side of the other edge  41   b  in the engaging slot  413  of the first shutter  41  while the engaging protrusion  223   b  engages in the end in the side of the one edge  42   a  in the engaging slot  423  of the second shutter  42 .  
      As shown in  FIG. 8 , when the rotary shutter  20  turns in the direction of Arrow A 3  to open the opening for access  101 , the engaging protrusion  223   b  moves along a path concentric with the rotary shutter  20  in the direction of Arrow A 4 . At this time, the engaging protrusion  223   b  slides from the side of the one edge  42   a  to the side of the other edge  42   b  in the engaging slot  423  of the second shutter  42  pushing the second shutter  42  outside. For this purpose, the engaging slot  423  of the second shutter  42  is shaped in an arc whose center is displaced from the turn center of the rotary shutter  20 .  
      Accordingly, when the rotary shutter  20  turns in the direction of Arrow A 3  to open the opening for access  101 , the second shutter  42  is pushed outside by the engaging protrusion  223   b . Thus, the second shutter  42  turns in the direction of Arrow A 5  around the turn axis  125   b  as a center so that the second shutter  42  opens.  
      The outer peripheral of the second shutter  42  is shaped in an arc so that the second shutter  42  does not interfere with the base frame  132  until the rotary shutter  20  stops turning.  
      In the first shutter  41 , when the rotary shutter  20  turns in the direction of Arrow A 3  to open the opening for access  101 , the engaging protrusion  223   a  moves along a path concentric with the rotary shutter  20  in the direction of Arrow A 4 . At this time, the engaging protrusion  223   a  slides from the side of the other edge  41   b  to the side of the one edge  41   a  in the engaging slot  413  of the first shutter  41  pushing the first shutter  41  outside. For this purpose, the engaging slot  413  of the first shutter  41  is shaped in an arc whose center is displaced from the turn center of the rotary shutter  20 .  
      Accordingly, when the rotary shutter  20  turns in the direction of Arrow A 3  to open the opening for access  101 , the first shutter  41  is pushed outside by the engaging protrusion  223   a . Thus, the first shutter  41  turns in the direction of Arrow A 5  around the turn axis  125   a  as a center so that the first shutter  41  opens.  
      The outer peripheral of the first shutter  41  is shaped in an arc so that the first shutter  41  does not interfere with the base frame  132  until the rotary shutter  20  stops turning.  
      Here, in the state shown in  FIG. 6A  where the first shutter  41  and the second shutter  42  are closed, the engaging protrusion  223   a  engages in the end in the side of the other edge  41   b  in the engaging slot  413  of the first shutter  41 . Therefore, a distance from the turn axis  125   a , which is the turn center of the first shutter  41 , to the engaging protrusion  223   a  is long. On the other hand, a distance from the turn axis  125   b , which is the turn center of the second shutter  42 , to the engaging protrusion  223   b  is short.  
      As a result, when the rotary shutter  20  starts turning, an angular velocity of the engaging protrusion  223   a  with respect to the turn axis  125   a  is smaller than an angular velocity of the engaging protrusion  223   b  with respect to the turn axis  125   b.    
      Therefore, in a case where the engaging slot  413  of the first shutter  41  is shaped in a predetermined arc similar to the engaging slot  423  of the second shutter  42 , a pushing velocity of the first shutter  41  (an opening velocity of the shutter) by the engaging protrusion  223   a  is smaller than a pushing velocity of the second shutter  42  (an opening velocity of the shutter) by the engaging protrusion  223   b . In other words, the first shutter  41  opens more slowly than the second shutter  42 .  
      For this reason, in the first shutter  41  of the embodiment, the side of the other edge  41   b  in the engaging slot  413  curves in a direction from the turn center toward outside. Moreover, in the side of the other edge  41   b  in the engaging slot  413 , the engaging protrusion  223   a  which turns in the direction of Arrow A 4  supplementarily pushes the first shutter  41 . Thus, the first shutter  41  and the second shutter  42  start opening at the same opening velocity.  
      &lt;&lt;Operation-Effect of Recording Disk Cartridge&gt;&gt; 
      Next, operation-effect of the recording disk cartridge  1  will be described. At first, operation of the rotary shutter  20  will be described. After that, operation and operation-effect of the hub hole shutter  40  will be described.  
      &lt;Operation of Rotary Shutter  20 &gt; 
      As shown in the right half in  FIG. 5 , the rotary shutter  20  is located in the close position in the normal state of the recording disk cartridge  1  (before being inserted in the drive unit D) so that the opening for access  101  is closed. More specifically, in the normal state, the opening for access  101  of the cartridge case  10  does not match or align with the notch  201  of the rotary shutter  20  so as to cause the opening for access  101  to be closed. Therefore, it is possible to prevent dust from entering the cartridge case  10  through the opening for access  101 . As a result, the recording disk medium  30  and so on are protected.  
      Moreover, when the rotary shutter  20  is thus located in the close position, the shutter knob  24  is located in a front side in the guide hole  124  of the lower shell  12 .  
      Then, when the recording disk cartridge I is inserted in the cartridge slot DS of the drive unit D, the unlock pin of the drive unit D (not shown) pushes the end  71  of the lock piece  70  in the inner radial direction. Thus, after lock of the rotary shutter  20  by the lock piece  70  is released (See Arrow A 6  in  FIG. 4 ), the shutter knob  24  is caught and stopped by the shutter knob stopper D 1  of the drive unit D. Therefore, when the recording disk cartridge  1  is further inserted keeping the shutter knob  24  stopped by the shutter knob stopper D 1 , the shutter knob  24  slides along the guide hole  124  (See Arrow A 2  in  FIG. 4 ).  
      Accordingly, the rotary shutter  20  with the stopped shutter knob  24  turns around the center pin  50  as an axis inside the cartridge case  10  (See Arrow A 3  in  FIG. 4 ). In other words, the rotary shutter  20  turns relatively to the cartridge case  10 . The opening for access  101  opens gradually in the drive unit D in synchronization with turning of the rotary shutter  20 .  
      As shown in the left half in  FIG. 5 , when the recording disk cartridge  1  is completely inserted and mounted in the drive unit D, the notch  201  of the rotary shutter  20  matches and aligns with the opening for access  101  of the cartridge case  10 . Therefore, the rotary shutter  20  is located in the open position so that the opening for access  101  completely opens. As a result, the recording disk medium  30  is exposed outside through the notch  201  and the opening for access  101  from inside of the drive unit D. Accordingly, the head of the swing arm SA of the drive unit D can read/write data from/to the recording disk medium  30 .  
      In a case where the rotary shutter  20  is located in the open position, the shutter knob  24  fixed to the rotary shutter  20  is located in the rear side in the guide hole  124  of the lower shell  12 .  
      Moreover, when the recording disk cartridge  1  is taken out of the drive unit D, the rotary shutter  20  is pushed in the closing direction by the pushing means (not shown) so as to return to the close position and close the opening for access  101 . Thus, when the rotary shutter  20  returns to the close position, the lock piece  70  locks the rotary shutter  20  (See  FIG. 4 ).  
      &lt;Operation and Operation-Effect of Hub Hole Shutter  40 &gt; 
      Next, the hub hole shutter  40  which operates in synchronization with the operation of the rotary shutter  20  will be described. As shown in the right half in  FIG. 5 , and  FIG. 6A , the hub hole shutter  40  covers the space S between the lower shell  12  of the cartridge case  10  and the hub  32  in the normal state of the recording disk cartridge  1  (before being inserted in the drive unit D, in the case where the rotary shutter  20  is located in the close position).  
      More specifically, the first shutter  41  and the second shutter  42 , which form the hub hole shutter  40 , together surround the hub  32  from the both sides between the lower shell  12  and the recording disk medium  30  so as to cover the space S.  
      Accordingly, it is possible to prevent dust from entering the cartridge case  10  through the space S. As a result, the recording disk medium  30  and so on are protected so that a read error can be prevented in the recording disk medium  30 .  
      Moreover, the first shutter  41  and the second shutter  42  together surround the hub  32  from the both sides. Therefore, the hub hole shutter  40  can completely cover the whole peripheral of the space S between the hub hole  123  and the hub  32 .  
      As shown in the left half in  FIG. 5 , and  FIG. 8 , when the recording disk cartridge  1  is inserted in the drive unit D and the rotary shutter  20  turns as described above, the engaging protrusion  223   a  turns in the direction of Arrow A 4 . The engaging protrusion  223   a , which engages in the slot  413  of the first shutter  41 , turns and slides in the engaging slot  413  pushing the first shutter  41 . Therefore, the first shutter  41  turns around the turn axis  125   a  of the lower shell  12  as an axis in the direction of Arrow A 5  so as to move away from the hub  32 .  
      Similarly, when the engaging protrusion  223   b  turns in the direction of Arrow A 4  in synchronization with turning of the rotary shutter  20 , the engaging protrusion  223   b , which engages in the engaging slot  423  of the second shutter  42 , turns and slides in the engaging slot  423  pushing the second shutter  42 . Therefore, the second shutter  42  turns around the turn axis  125   b  of the lower shell  12  as an axis in the direction of Arrow A 5  so as to move away from the hub  32 .  
      As described above, when the rotary shutter  20  starts turning, an angular velocity of the engaging protrusion  223   a  with respect to the turn axis  125   a  which pivots the first shutter  41  is smaller than an angular velocity of the engaging protrusion  223   b  with respect to the turn axis  125   b  which pivots the second shutter  42 . However, in the first shutter  41 , the side of the other edge  41   b  in the engaging slot  413  curves in the direction from the turn center toward outside. In addition, in the side of the other edge  41   b  in the engaging slot  413 , the engaging protrusion  223   a  which turns in the direction of Arrow A 4  supplementarily pushes the first shutter  41 . Therefore, the first shutter  41  and the second shutter  42  start opening at the same opening velocity.  
      Moreover, the engaging protrusions  223   a  and  223   b  in the lower surface of the rotary shutter  20  are respectively inserted and engaged in the engaging slots  413  and  423  formed in the first shutter  41  and the second shutter  42  of the hub hole shutter  40  so that the rotary shutter  20  can easily and exactly engages with the hub hole shutter  40 . Therefore, the first shutter  41  and the second shutter  42  exactly turn in synchronization with turning of the rotary shutter  20 .  
      Thus, as shown in  FIG. 6B , when the first shutter  41  and the second shutter  42  respectively turn and move away from the hub  32 , the hub hole shutter  40  opens the space S. At the same time, the hub  32  is released from the surrounding hub hole shutter  40  (See the left half in  FIG. 5 ). As a result, the hub  32  can move in the hub hole  123 . Therefore, when the hub  32  is chucked by the spindle (not shown) of the drive unit D, position of the hub  32  can be easily adjusted corresponding to position of the spindle. Thus, the spindle (not shown) of the drive unit D, which chucks the hub  32  can appropriately turn the hub  32  and the recording disk medium  30  including the hub  32 .  
      When the recording disk cartridge  1  is taken out of the drive unit, the hub hole shutter  40  closes the space S in synchronization with the rotary shutter  20  which turns and returns to the close position.  
      Thus, the hub hole shutter  40  turns in synchronization with turning of the rotary shutter  20  which opens and closes the opening for access  101  of the cartridge case  10  so as to open and close the space S between the hub hole  123  of the cartridge case  10  and the hub  32  of the recording disk medium  30 . Therefore, dust is prevented from entering the cartridge case  10  through the space S so that the recording disk medium  30  and so on inside the cartridge case  10  can be protected.  
      Moreover, in the hub hole shutter  40  of the embodiment, the first shutter  41  and the second shutter  42  are respectively pivoted to the lower shell  12  of the cartridge case  10 . Thus, the first shutter  41  and the second shutter  42  are supported without overlap to open and close the space S between the hub hole  123  and the hub  32 . Therefore, the hub hole shutter  40  can be thin and employed for a thin recording disk cartridge  1 .  
      In addition, the turn axes  125   a  and  125   b , which are protruded from the inner surface of the lower shell  12  of the cartridge case  10  by means of a burring process, are respectively inserted through the axis holes  411  and  421  formed in the first shutter  41  and the second shutter  42 . Then, the ends of the turn axes  125   a  and  125   b  are crimped. Thus, the hub hole shutter  40  is supported by the lower shell  12  (See  FIG. 7B ). Therefore, axes do not need to be attached as separate parts to support the first shutter  41  and the second shutter  42 . As a result, the hub hole shutter  40  can be easily assembled.  
      Description has been given to a preferred embodiment of the present invention, above. The invention is not limited to the embodiment, but may be modified as described below, for instance, within the spirit of the invention.  
      For instance, the recording disk medium is not limited to a magnetic disk medium. An optical disk medium such as a magnet-optical disk medium and a phase change disk medium may be used as the recording disk medium. In addition, the recording disk medium is not limited to a flexible disk medium either. A rigid disk medium such as a DVD-RAM may be used as the recording disk medium.  
      Moreover, as shown in  FIG. 4 , in the embodiment, the hub hole shutter  40  has two shutters, that is, the first shutter  41  and the second shutter  42 . However, the number of the shutters included in the hub hole shutter  40  is not limited to this. Two or more shutters may be included as long as a sufficient space for the shutters is available inside the cartridge case  10 . Furthermore, only one shutter may be included in the hub hole shutter. In this case, the space S between the hub hole  123  and the hub  32  cannot be entirely covered by the hub hole shutter. However, dust which enters the cartridge case  10  through the space S can be dramatically reduced.  
      Moreover, as shown in the side sectional view in  FIG. 9 , a side of the other edge  41   b  (or  42   b ) in the first shutter  41  (or the second shutter  42 ) is inclined to the lower surface of the rotary shutter  20  so as to cause the side of the other edge  41   b  (or  42   b ) to approach the lower surface of the rotary shutter  20 .  
      In this case, the engaging protrusions  223   a  and  223   b  in the lower surface of the rotary shutter  20  are deeply inserted in the engaging slots  413  and  423  in the sides of the other edges  41   b  and  42   b . Therefore, the engaging protrusions  223   a  and  223   b  can be prevented from detaching from the engaging slots  413  and  423  even in the sides of the other edge  41   b  and  42   b  which are free and shaky so that the first shutter  41  and the second shutter  42  can exactly turn.  
      Inclination angles in the sides of the other edges  41   b  and  42   b  are preferably small, for instance, about 1°, so as to prevent the other edges  41   b  and  42   b  from strongly rubbing the lower surface of the rotary shutter  20 .  
      According to the present invention, the hub hole shutter can turn in synchronization with turning of the rotary shutter which opens and closes the case opening of the cartridge case so as to open and close the space between the hub hole of the cartridge case and the hub of the recording disk medium. Therefore, dust can be prevented from entering the cartridge case through the space so that the recording disk medium and so on inside the cartridge case can be protected.  
      While the described embodiments represent the preferred forms of the present invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the spirit and scope of the following claims.