Abstract:
An electronic apparatus that can be ejectably mounted in a rack mount apparatus that includes a first housing and a mechanism adapted to project from the first housing includes a second housing that is fixed onto the mechanism, and mounted in the first housing so that the second housing can be drawn from the first housing; and a provisional fixture member that is attached to the second housing and engageable with the mechanism.

Description:
[0001]     This application claims foreign priority based on Japanese Patent Application No. 2005-184760 filed on Jun. 24, 2005, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to a rack mount apparatus that accommodates plural electronic apparatuses so that each electronic apparatus can be drawn from and inserted into a housing of the rack mount apparatus, and more particularly to a mounting mechanism and method for mounting an electronic apparatus in the rack mount apparatus. The present invention is suitable, for example, for a mounting mechanism used to mount in a rack mount apparatus a disc array storage that installs plural hard disc drive (“HDD”) units.  
         [0003]     A disc array storage that removably installs plural HDD units has recently been proposed so as to realize a large-capacity external storage (see, for example, Japanese Patent Application, Publication No. 2004-54967). The disc array storage allows only a target HDD unit that requires maintenance, to be exchanged while keeping a running state of the entire apparatus, and also includes a fixing mechanism that prevents unintentional ejections of the HDD unit(s) from the disc array storage due to vibrations, etc. A rack mount apparatus that is mounted with plural disc array storages in a rack mount manner is also known (see, for example, Fujitsu Japan, Product Lineup, ETERNUS, http://storage-system.fujitsu.com/jp/products/, searched on Jun. 21, 2005). Such a rack mount apparatus requires the improved operability in mounting the disc array storage in and detaching the disc array storage from the rack mount storage.  
         [0004]     Other prior art include Japanese Patent Application, Publication No. 11-330743.  
         [0005]     The conventional disc array storage is screwed onto a rack mount apparatus, and each HDD unit is inserted into the disc array storage ejectably through a front surface of the disc array storage. However, in order to meet with the recent demand for the large capacity by increasing the installation density of the HDD units, the instant inventor has studied a structure that makes the disc array storage drawable from the rack mount apparatus, and opens the top surface of the disc array storage so that plural HDD units in a matrix can be inserted into and ejected from the disc array storage along the height direction of the disc arrays storage. In this case, if the rack mount apparatus has a mechanism that projects from and retreats into the housing of the rack mount apparatus, and the disc array storage is fixed (e.g., screwed) onto the mechanism, the disc array storage can be drawn from the rack mount apparatus. One known mechanism applicable to this purpose is a slide rail disclosed in Takachiho Koheki Co., Ltd., Products and Service, Mechanical Component Product, Slide Rail 5800 Series, http://www.takachiho-kk.co.jp/products/mechanical/slide/5800.html, searched on Jun. 21, 2005.  
         [0006]     In order to fix the disc array storage onto the above slide rails and mount the disc array storage in the rack mount apparatus, it is necessary to hold the disc array storage relative to a pair of slide rails so that the pair of slide rails are arranged in place relative to both side surfaces of the disc array storage, and then to screw the slide rails onto the disc array storage. However, it is difficult to screw the slide rails onto the disc array storage while holding the disc array storage in place relative to the slide rails. This difficulty increases, as the disc array storage is heavier than 60 kg due to the high installation density of the HDD units.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     Accordingly, it is an exemplary object to provide an electronic apparatus, a rack mount apparatus and a mounting method, in which the electronic apparatus can be easily mounted on the rack mount apparatus.  
         [0008]     An electronic apparatus according to one aspect of the present invention that can be ejectably mounted in a rack mount apparatus that includes a first housing and a mechanism adapted to project from the first housing includes a second housing that is fixed onto the mechanism, and mounted in the first housing so that the second housing can be drawn from the first housing, and a provisional fixture member that is attached to the second housing and engageable with the mechanism. According to the electronic apparatus, such as a disc array storage, the provisional fixture member holds the second housing relative to the first housing, and eliminates the necessity to support the second housing in finally fixing the second housing onto the mechanism, such as a slide rail, facilitating the operation. The provisional fixture member includes, for example, a flat spring provided near a front surface of the second housing, the flat spring being able to retreat into the second housing and project from the second housing.  
         [0009]     The electronic apparatus may further include a moving unit that enables the second housing to move relative to the first housing. The provisional fixture is automatically realized by moving the second housing relative to the first housing utilizing the moving unit, improving the workability. The moving unit includes, for example, a guide frame attached to the second housing and slidable on the mechanism.  
         [0010]     The guide frames may be attached to a pair of side surfaces that is orthogonal to a front surface of the second housing, and may have such a U-shaped section that the guide frame includes a horizontal part parallel to the side surface of the second housing, and a pair of perpendicular parts perpendicular to the side surface. This structured guide frame can be commonly used for both side surfaces of the second housing. Since it is unnecessary to produce differently structures guide frames for left and right side surfaces, the manufacturing efficiency improves. Preferably, the pair of perpendicular parts have a pair of proximal ends, and a pair of distal ends, the pair of proximal ends being closer to the front surface of the second housing than the pair of distal ends, the pair of distal ends being bent in such a direction that the distal ends approach to each other. This structure reduces the interference between the guide frame and the mechanism, and improves the workability in detaching the electronic apparatus from the rack mount apparatus.  
         [0011]     Preferably, the moving unit is adapted to displace between first and second positions, wherein when the moving unit is located at the first position, the second housing moves relative to the first housing while the moving unit contacts the rack mount apparatus, and wherein when the moving unit is located at the second position, the second housing moves relative to the first housing while the moving unit is being spaced from the rack mount apparatus. According to this structure, the moving unit is set to the first position and used in mounting the second housing in the first housing, whereas the moving unit is set to the second position so that the second housing is moved through the mechanism after the second housing is mounted in the first housing. This structure also prevents interference between the moving unit and the mechanism after the mounting is completed.  
         [0012]     The moving unit may have first and second ends, wherein the moving unit is attached to the second housing rotatably at the first end, and the moving unit is engageable with two different positions of the second housing at the second end, the moving unit including a thumbscrew at the second end. The thumbscrew does not require a tool, such as a screwdriver, and improves the workability.  
         [0013]     Preferably, the guide frame has a length of at least L/2 and covers a range from L/4 to 3L/4 from the front surface of the second housing, where L is a length of the second housing in a drawing direction. When the guide frame is too long, it is difficult to retreat the guide frame from the mechanism after mounting. When the guide frame is too short, the mounting work becomes difficult. Therefore, this range is preferable.  
         [0014]     Plural units may be attached to and ejected from the electronic apparatus along a height direction of the electronic apparatus. When the electronic apparatus has an open top surface and a unit, such as a HDD unit, is removably inserted along the height direction, the electronic apparatus can install the units with a high installation density.  
         [0015]     A rack mount apparatus according to another aspect of the present invention that is mounted with an electronic apparatus so that the electronic apparatus can be drawn from the rack mount apparatus includes a first housing and a mechanism that is adapted to project from the first housing, wherein the electronic apparatus includes a second housing that is fixed onto the mechanism, and a provisional fixture member that is attached to the second housing and engageable with the mechanism. This rack mount apparatus exhibits an operation of the above electronic apparatus.  
         [0016]     The electronic apparatus may further include a guide frame attached to the second housing and slidable on the mechanism, the guide frame enabling the second housing to move relative to the first housing, the mechanism having a first end, the guide frame having a second end, at least one of the first and second ends being inclined, wherein in inserting the second housing that has been drawn from the first housing, into the first housing, the second end of the guide frame contacts the first end of the mechanism. This structure reduces the interference between the guide frame and the mechanism, and improves the workability in detaching the electronic apparatus from the rack mount apparatus.  
         [0017]     A method according to another aspect of the present invention for mounting an electronic apparatus in a rack mount apparatus having a first housing and a mechanism adapted to project from the first housing, an electronic apparatus including a second housing includes the steps of provisionally fixing the second housing onto the mechanism, and finally fixing the second housing onto the mechanism while the second housing being moved relative to the first housing. According to this method, the provisionally fixing step provides the provisional fixture that holds the second housing relative to the first housing, eliminates the necessity to hold the second housing in finally fixing the second housing onto the mechanism, such as a slide rail, and improves the workability.  
         [0018]     The provisional fixing step may include the step of inserting the second housing into the first housing so as to effectuate provisional fixing, and the finally fixing step may include the step of drawing from the first housing the second housing with the mechanism that has been provisionally fixed onto the second housing. When the housing or moving action provides the provisional fixture, the workability improves. When the second housing is finally fixed while drawn from the first housing, the overload upon the provisional fixture member and possible dropping of the second housing from the first housing can be prevented.  
         [0019]     The inserting step may include the step of setting to a first state a moving unit that enables the second housing to move relative to the first housing, wherein the method may further include the step of setting the moving unit to a second state different from the first state after the finally fixing step, wherein when the moving unit is located at the first position, the second housing moves relative to the first housing while the moving unit contacts the rack mount apparatus, and wherein when the moving unit is located at the second position, the second housing moves relative to the first housing while the moving unit is being spaced from the rack mount apparatus. According to this structure, the moving unit is set to the first position and used in mounting the second housing in the first housing, whereas the moving unit is set to the second position so that the second housing is moved through the mechanism after the second housing is mounted in the first housing. This structure also prevents interference between the moving unit and the mechanism after the mounting is completed.  
         [0020]     Other objects and further features of the present invention will become readily apparent from the following description of the preferred embodiments with reference to accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a schematic perspective view of a rack mount apparatus according to one aspect of the present invention.  
         [0022]      FIGS. 2A and 2B  are perspective overviews showing final fixtures of the disc array storage onto the rack mount apparatus without provisional fixtures.  
         [0023]      FIG. 3  is an exploded perspective view of the disc array storage according to one aspect of the present invention.  
         [0024]      FIGS. 4A and 4B  are schematic perspective and side views, respectively, of a guide frame in the disc array storage shown in  FIG. 3 .  
         [0025]      FIG. 5  is a perspective overview for explaining a method of mounting the disc array storage shown in  FIG. 3  in the rack mount apparatus.  
         [0026]      FIG. 6  is a partially enlarged sectional view of the disc array storage and the rack mount apparatus shown in  FIG. 5 .  
         [0027]      FIG. 7  is a partially transparent perspective view showing that the disc array storage shown in  FIG. 5  is completely housed in the rack mount apparatus.  
         [0028]      FIG. 8  is a perspective overview showing that the disc array storage is partially drawn from the state shown in  FIG. 7 .  
         [0029]      FIG. 9A  is a schematic perspective view showing that the guide frame is displaced after the disc array storage is finally fixed, and  FIG. 9B  is an enlarged side view of that state.  
         [0030]      FIG. 10  is a flowchart for explaining a method of mounting the disc array storage in the rack mount apparatus according to one aspect of the present invention.  
         [0031]      FIG. 11  is an enlarged side view showing that the guide frame is displaced in order to detach the disc array storage from the rack mount apparatus.  
         [0032]      FIG. 12  is a perspective overview showing that the disc array storage is gradually inserted into the rack mount apparatus from the state shown in  FIG. 11  and the final fixture is released.  
         [0033]      FIG. 13  is a perspective overview showing that the last screws for final fixtures are detached after the state shown in  FIG. 12 .  
         [0034]      FIG. 14  is a perspective overview showing that the disc array storage is being detached from the rack mount apparatus.  
         [0035]      FIG. 15  is a flowchart for explaining a method of detaching the disc array storage from the rack mount apparatus according to another aspect of the present invention.  
         [0036]      FIGS. 16A and 16B  are schematic perspective views for explaining the operations of the rack mount apparatus shown in  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]     Referring now to the accompanying drawings, a description will be given of a rack mount apparatus  200  and a disc array storage  100  to be mounted in the rack mount apparatus  200  according to one embodiment of the present invention. Here,  FIG. 1  is a perspective overview of the rack mount apparatus  200 . The rack mount apparatus  200  serves as a large-capacity storage, and is mounted with plural stages of disc array storages  100  so that each of them can be drawn from the rack mount apparatus  200 .  FIG. 1  omits a guide frame  160  of the disc array storage  100 .  
         [0038]     The rack mount apparatus  200  includes a housing  210 , four posts or rack pillars  220 , a pair of brackets  230 , and a pair of slide rails  240  in the housing  210 . In finally (i.e., regularly, unconditionally or non-provisionally) fixing the disc array storage  10  onto commercially available slide rails  240 , such as 5800 Series manufactured by Takachiho Koheki without provisional fixtures, unlike this embodiment which will be described later, it is necessary as shown by an arrow in  FIG. 2A  to support the disc array storage  10  relative to the slide rails  240  so that both side surfaces of the disc array storage  10  are positioned to the slide rails  240 . Next, it is necessary as shown in  FIG. 2B  to support the disc array storage  10  heavier than 60 kg using a lifter of a few people from the bottom and to secure the slide rails  240  onto the disc array storage  10  using screws  190 . Here,  FIGS. 2A and 2B  are perspective views for explaining a method for finally fixing the slide rails  240  onto the disc array storage  10  without provisional fixtures. However, if the disc array storage  10  is supported by human power, the disc array storage  10  shakes and it is difficult to align it with the screws  190 . In addition, customers seldom have a lifter or similar equipment at installation sites and thus the installation is dangerous. This embodiment solves these problems as follows:  
         [0039]     Referring now to  FIGS. 3, 4A  and  4 B, a description will be given of the disc array storage  100  according to this embodiment. The disc array storage  100  is different from the disc array storage  10  in that the disc array storage  100  includes a flat spring  150  and a guide frame  160 . More specifically, the disc array storage  100  includes a housing  101 , a pair of flat springs  150 , a pair of guide frames  160 , and various fixing means (such as elements  170  and  172 ).  
         [0040]     The housing  101  has a hollow rectangular parallelepiped shape with a top plate  110 , a pair of side plates  120 , a bottom plate  130 , and a front panel  140 .  
         [0041]     The housing  101  except the front panel  140  is made by bending a sheet metal, and it may be formed like a U shape without the top plate  110 . In omitting the top plate  110 , the plate having the function of the top plate  10  (for protecting the internal electronic components) may be fixed onto the bracket  230  in the rack mount apparatus  200 .  
         [0042]     Each side plate  120  serves to support the flat spring  150  and the guide frame  160 , and is connected to the slide rail  240 . Each slide plate  120  has perforation holes  121  to  128 . The perforation hole  121  is provided in each of the left and right side plates  120  near the front panel  140 , and used for the flat spring  150  to partially project. The perforation hole  122  communicates with a perforation hole  152  in the flat spring  150 , and serves as one in which a screw (not shown) is inserted to fix the flat spring  150 . The perforation hole  124  is a screw hole with which a screw  172  is engaged. The perforation holes  126   a  and  126   b  are screw holes in which a thumbscrew  170  is inserted. A line that connects the perforation holes  124  and  126   a  to each other is parallel to the bottom surface  130 , and accords with the extending direction of the slide rail  240 . The perforation hole  126   b  is located on a circumference of a circle with a center of the perforation hole  124  and a radius of R, where R is a distance between the perforation holes  124  and  126   a.  In other words, viewed from the perforation hole  124 , the perforation holes  126   a  and  126   b  are located on the same circumference of the circle. Four perforation holes  128  are arranged at regular intervals, and a line connecting them to one another is parallel to the bottom plate  130 , and accords with the extending direction of the slide rail  240 .  
         [0043]     The bottom plate  130  supports electronic and other components, such as an HDD unit  50 , which will be described later with reference to  FIG. 16 .  
         [0044]     The front panel  140  is a plate member having a pair of grips  142 , and provided to a front surface of the housing  101 . The grips  142  are members, which a user holds and applies a force to move the disc array storage  100  relative to the rack mount apparatus  200 . A connection between the front panel  140  and another portion of the housing may use bending, welding and other techniques known in the art. If necessary, the front panel  140  may be formed detachably in the housing  101 .  
         [0045]     The flat springs  150  are attached to the housing  101 , and serve as provisional fixture parts engageable with the slide rails  240 . The disc array storage  100  and slide rails  240  are firmly fixed via eight screws  190 , as will be described later. This unconditional fixture is called “final fixture” in this specification. The “provisional fixture”, on the other hand, is a rough engagement between the disc array storage  100  and the slide rails  240  prior to the final fixture. Since the provisional fixture parts or the flat springs  150  thus serve to partially hold and position the housing  101  relative to the housing  210 , the positioning and support of the housing  101  are unnecessary in finally fixing the slide rails  240  onto the housing  101  and the workability improves.  
         [0046]     Each flat spring  150  includes, as shown in  FIG. 3 , a perforation hole  152 , a flat board part  154 , and an engagement part  156 . The perforation hole  152  communicates with the perforation hole  122 , and serves as one in which a screw (not shown) is inserted. The screw (not shown) fixes the flat spring  150  onto the side plate  120 . The flat board part  154  contacts the rear surface of the side plate  120 . The engagement part  156  protrudes from the perforation hole  121  and engages with a rectangular hole  272  in the inner rail  270 , which will be described later. The flat board part  154  bends and deforms when the engagement part  156  receives the force in a retreating direction.  
         [0047]     The flat spring  150  is provided near the front surface of the housing  101 , and can retreat from and protrude into the housing  101 . The tip of the slide rail  240  can be provided near the front surface of the housing  101  by providing each slide rail  240  with an engagement part with the flat spring  150  at the tip of the slide rail  240 , and positioning the flat spring  150  near the front surface of the housing  101 . The slide rail  240  that extends over the overall length of the housing  101  in the longitudinal direction L maintains the stable connection between the slide rail  240  and the housing  101 .  
         [0048]     The guide frames  160  enables the housing  101  to move relative to the  210 , and serve as a moving means for effectuating the provisional fixtures. Mere moving the housing  101  relative to the housing  210  using the moving means leads to the automatic provisional fixtures, and facilitates the workability.  
         [0049]     The guide frames  160  are attached to the respective side plates  120  of the housing  101 , and slidable on the slide rails  240 . The guide frame  160  includes, as shown in  FIGS. 4A and 4B , a horizontal part  162  parallel to the side plate  120 , and a pair of perpendicular parts  164  perpendicular to the side plate  120 , and has a U-shaped section symmetrical with respect to the centerline C.  
         [0050]     The symmetrical guide frame  160  is commonly used for both side plates  120  of the housing  101 , and provides better economic and productive efficiencies than a differently structured guide frame for each of the left and right side plates  120 . The lower perpendicular part  164  of the guide frame  160  shown in  FIG. 3  becomes an upper perpendicular part when attached to the backside side plate  120 .  
         [0051]     The horizontal part  162  has an elongated track shape, and has a proximal perforation hole  163   a  and a distal perforation hole  163   b.  The proximal perforation hole  163   a  is closer to the front surface of the housing  101  than the distal perforation hole  163   b.  The perforation hole  163   a  communicates with the perforation hole  124 , and the perforation hole  163   b  communicates with the perforation hole  126   a  or  126   b.    
         [0052]     One of the pair of perpendicular parts  164  slides on the corresponding slide rail  240  for the provisional fixture during mounting. The pair of perpendicular parts  164  have a pair of proximal ends  161   a  close to the front surface of the housing  101 , and a pair of distal ends  161   b  far from the front surface of the housing  101 . The distal ends  161   b  are bent and form a pair of inclined parts  165  in such a direction that they approach to each other. The inclined part  165  can easily go on the slide rail  240  and reduces the interference between the guide frame  160  and the slide rail  240 , improving the workability in detaching the disc array storage  100  from the rack mount apparatus  200 , as described later.  
         [0053]     The guide frame  160 , especially its perpendicular part  164 , has a length of about L 1 /2, where L 1  is a length of the housing  101  in the direction L. In addition, the guide frame  160 , especially its perpendicular part  164 , preferably covers a range from L 1 /4 to 3L 1 /4 from the front surface of the housing  101 . If the guide frame  160  is too long, the thumbscrew  170  does not expose and it becomes difficult to displace the guide frame  160  and retreat it from the slide rail  240  as described later with reference to  FIG. 9B . In addition, if the guide frame  160  is too short, mounting which will be described later with reference to  FIG. 5  becomes difficult. Therefore, the above range is preferable.  
         [0054]     The thumbscrew  170  is attached to the guide frame  160  while perforating through the perforation hole  163   b  in the horizontal part  162  of the guide frame  160 . The thumbscrew  170  is attached to the perforation hole  126   a  or  126   b  in the side plate  120 . The thumbscrew  170  does not require a tool, such as a screwdriver, and improves the assembly operation. The screw  172  is inserted into the perforation hole  124  after perforating through the perforation hole  163   a  via a spacer  174 . Thereby, when an engagement between the thumbscrew  170  and the housing  101  is released, the guide frame  160  becomes rotatable around the perforation holes  163   a  and  124 . The screw  172  is replaced with the thumbscrew  170 .  
         [0055]     Referring now to  FIGS. 1, 2A  and  2 B, a description will be given of the rack mount apparatus  200 . As described above, the rack mount apparatus  200  includes a housing  210 , and four internal posts or rack pillars  220 , a pair of brackets  230 , and a pair of slide rails  240 .  
         [0056]     The housing  210  has a rectangular parallelepiped shape as shown in  FIG. 1 , and can house plural disc array storages  100  in its height direction. Provided inside the housing  210  are four posts  220 , onto which a pair of brackets  230  are screwed along the direction L. The slide rail  240  is fixed onto the corresponding bracket  230 , and the brackets  230  serve to support the slide rails  240  and the disc array storage  100  screwed onto the slide rails  240 . Each bracket  230  has five perforation holes  232 , and a line connecting these perforation holes  232  to each other is parallel to the longitudinal direction L of the disc array storage  100 .  
         [0057]     The slide rails  240  serve to enables the disc array storage  100  to move relative to the housing  210  along the L direction. The slide rails  240  of this embodiment uses such a commercially available product as 5800 Series manufactured by Takachiho Koheki, but the present invention does not limit the slide rails  240  to that product.  
         [0058]     Each slide rail  240  includes an outer rail  250 , an intermediate rail  260 , and an inter rail  270 . The outer rail  250 , intermediate rail  260 , and inter rail  270  have approximately the same length in the L direction as the length L 1  of the disc array storage  100  in the direction L. When the slide rails  240  are fixed onto both the side plates  120  of the housing  101 , the user holds the grip  142  and draws the disc array storage  100  from the housing  210  or inserts the disc array storage  100  into the housing  210 .  
         [0059]     The outer rail  250  is made of a sheet metal having a U-shaped section, and extends along the longitudinal direction L of the bracket  230  over almost the overall length of the bracket  230 . The outer rail  250  has a horizontal part  252 , and a pair of perpendicular parts  256  perpendicular to the horizontal part  252 . The horizontal part  252  is arranged parallel to the bracket  230 , and the perpendicular parts  256  are formed by bending both ends of the horizontal part  252  at a right angle. The horizontal part  252  has five perforation holes  253  that are connected to five perforation holes  232 , and is fixed onto the bracket  230  via these perforation holes  232  and  253 .  
         [0060]     Although the intermediate rail  260  is made of a sheet metal having a U-shaped section similar to the outer rail  250 , the length of the intermediate rail  260  in the H direction is shorter than that of the outer rail  250  in the H direction. There are ball bearings between the outer rail  250  and the intermediate rail  260  in the H direction, and the intermediate rail  260  is arranged in the outer rail  250  so that the intermediate rail  260  can move in the L direction. As shown in  FIG. 6 , which will be described later, the U shapes of the intermediate rail  260  and the outer rail  250  face the same direction. The intermediate rail  260  has four perforation holes  262 , but they are not used for the fixture of the intermediate rail  260 . The intermediate rails  260  are not directly fixed onto the bracket  230 , and the length of the intermediate rail  260  by which the intermediate rail  260  projects from the housing  210  is half the overall length or about L 1 /2.  
         [0061]     The inner rail  270  is made of a metal sheet having a U-shaped section similar to the outer rail  250 , but the length of the inner rail  270  in the H direction is shorter than that of the intermediate rail  260  in the H direction. There are ball bearings between the inner rail  270  and the intermediate rail  260  in the H direction, and the inner rail  270  is arranged in the intermediate rail  260  movably in the L direction. As shown in  FIG. 6 , which will be described later, the U shapes of the intermediate rail  260  and the inter rail  270  face each other. The inner rail  270  is not fixed onto the bracket  230  or intermediate rail  260 , and the length of the inner rail  270  by which the inner rail  270  projects from the housing  210  is the overall length or about L 1 .  
         [0062]     Each inner rail  270  has one rectangular hole  272 , and four perforation holes  274 . The rectangular hole  272  is a portion engageable with the engagement part  156  of the flat spring  150 . The four perforation holes  274  communicate with four perforation holes  128  in the side plate  120  of the housing  101 . The inner rails  270  are fixed onto the side plates  120  of the housing  101  via the perforation holes  128  and  274  and the screws  190 .  
         [0063]     Referring now to FIGS.  5  to  10 , a description will be given of a method for mounting the disc array storage  100  into the rack mount apparatus  200 . Here,  FIG. 5  is a schematic perspective view for explaining the provisional fixture of the disc array storage  100 .  FIG. 6  is a sectional view with respect to a plane parallel to the front surface of the disc array storage  100  in the state shown in  FIG. 5 .  FIG. 7  is a partially transparent perspective view of the disc array storage  100  that has been provisionally fixed.  FIG. 8  is a schematic perspective view showing that the disc array storage  100  is gradually drawn from the rack mount apparatus  200  so as to finally fix the slide rails  240  onto the housing  101  of the disc array storage  100  that has been provisionally fixed.  FIG. 9A  is a schematic perspective view showing a change of the angle of the guide frame after the final fixtures are completed.  FIG. 9B  is an enlarged side view of that state shown in  FIG. 9A .  FIG. 10  is a flowchart for explaining a method of mounting the disc array storage  100  into the rack mount apparatus  200 .  
         [0064]     Initially, the guide frame  160  is attached parallel to the bottom plate  130  (step  1002 ). At this time, the user attaches the thumbscrew  170  to the perforation hole  126   a.  This arrangement enables the lower perpendicular parts  164  of the guide frames  160  to serve as the moving means in mounting the housing  101  into the housing  210  for provisional fixtures.  
         [0065]     Next, the user inserts the disc array storage  100  into the opening in the rack mount apparatus  200  so that the guide frames  160  are placed on the slide rails  240  (step  1004 ). This action is easy because all what is necessary is merely to place the guide frames  160  on the slide rails  240  and squeeze the housing  101  into the housing  210 . More specifically, the disc array storage  100  is inserted into the rack mount apparatus  200  so that the lower perpendicular parts  164  of the guide frames  160  are placed on the upper perpendicular parts  256  of the outer rails  250 .  FIGS. 5 and 6  show this state.  
         [0066]     Then, as shown in an arrow in  FIG. 5 , the disc array storage  100  is inserted, and the disc array storage is temporarily stored in the rack mount apparatus  200  (step  1006 ).  FIG. 7  shows this state. In step  1006  shown in  FIG. 7 , the engagement parts  156  of the flat springs  150  are engaged with the rectangular holes  272  in the inner rails  270 . More specifically, as the disc array storage  100  proceeds in the rack mount apparatus  200  after the engagement parts  156  contact the inner rails  270 , the engagement parts  156  deform and retreat in the housing  101 , then face and thus protrude into the rectangular holes of the inner rails  270 .  
         [0067]     This state is the provisional fixtures state, and the housing  101  is engaged with the slide rails  240  via the flat springs  150  and the inner rails  270 . In addition, the perforation holes  274  in the inner rails  270  communicate with the perforation holes  128  in the side plates  120  due to the provisional fixtures. In this state, the housing  101  and the slide rails  240  are not firmly coupled, and thus when the housing  101  is drawn as shown in  FIG. 2B , the weight of the housing  101  concentrates on the flat springs  150  and the disc array storage  100  would drop. In order to avoid this problem, it is necessary as shown in  FIG. 2B  to firmly couple the slide rails  240  with the housing  101  using the screws  190 .  
         [0068]     Accordingly, the slide rails  240  are next screwed onto the housing  101  while the disc array storage  100  is gradually being drawn from the rack mount apparatus  200  (step  1008 ). While the user is gradually drawing the disc array storage  100  from the rack mount apparatus  200  through the grips  142 , the flat springs  150  are engaged with the inner rails  270  and thus the inner rails  270  are gradually being drawn. Therefore, whenever the perforation holes  274  and  128  expose, the screws  190  are attached to these holes.  FIG. 8  shows this state.  
         [0069]     The provisional fixtures parts (or the flat springs  150  and the rectangular holes  272 ) position and hold the housing  101  relative to the housing  210  during the final fixtures between the housing  101  and the slide rails  240 , and improves the workability, because it is unnecessary unlike the conventional structure to use lifter etc. to position and hold the housing  101 . In addition, the final fixtures made while the housing  101  is being drawn from the housing  210  prevent overloads upon the provisional fixtures parts and a possible drop of the housing  101  from the housing  210 .  
         [0070]     When the slide rails  240  completely project, the inner rails  270  are firmly coupled with the housing  101  via the screws  190  and the slide rails  240  support the disc array storage  100  stably.  
         [0071]     After the slide rails  240  completely project and the final fixtures end, the angles of the guide rails  160  are changed (step  1010 ).  FIGS. 9A and 9B  show this state. As shown in an arrow shown in  FIG. 9B , the user displaces the thumbscrews  170  from the perforation holes  126   a  to the perforation holes  126   b.  This is because the thumbscrews  170  if remaining at the perforation holes  126   a  would cause the lower perpendicular parts  164  of the guide rails  160  to collide with the upper perpendicular parts  256  of the outer rails  250  of the slide rails  240  in again inserting the disc array storage  100  into the rack mount apparatus  200 . The displaced guide frames  160  are spaced from the slide rails  240 , and prevent the interferences between the guide frames  160  and the slide rails  240  in moving the housing  101  after the final fixtures.  
         [0072]     In operation, the disc array storage  100  that has been stored in the rack mount apparatus  200  ( FIG. 16A ) is drawn from the rack mount apparatus  200 , and the HDD unit  50  is inserted into its height direction H ( FIG. 16B ). The HDD unit  50  is, for example, a 2.5-inch HDD unit, as disclosed in Japanese Patent Applications, Publication Nos. 2004-241231 and 2005-182996.  
         [0073]     This embodiment removes the top plate  110  of the housing  101 , and the HDD unit  50  can be installed in the disc array storage  100  through the entire top surface. Therefore, plural rows of HDD units  50  in the longitudinal direction L can be installed in the disc array storage  100 , and providing the higher installation density than the conventional structure in which the HDD units are inserted and ejected only through the front panel  140 . As a result, the rack mount apparatus  200  can increase both the capacity per disc array storage  100  and its entire capacity, satisfying the recent high storage capacity demand.  
         [0074]     Referring now to FIGS.  11  to  15 , a description will be given of a method for detaching the disc array storage  100  from the rack mount apparatus  200 . Here,  FIG. 11  is a partially enlarged side view showing a change of the angle of the guide frame  160 .  FIG. 12  is a schematic perspective view showing a release of the final fixtures of the disc array storage  100 .  FIG. 13  is a schematic perspective view of the disc array storage that has been provisionally fixed.  FIG. 14  is a schematic perspective view showing that the disc arrays storage  100  is detached from the rack mount apparatus  200  after the provisional fixtures are released.  FIG. 15  is a flowchart for explaining a method of detaching the disc array storage  100  from the rack mount apparatus  200 .  
         [0075]     Initially, the disc arrays storage  100  is drawn from the rack mount apparatus  200  and the angles of the guide frames  160  are changed to be parallel to the bottom plate  130  (step  1102 ).  FIG. 11  shows this state. At this time, as shown by an arrow shown in  FIG. 11 , the user displaces the thumbscrews  170  from the perforation holes  126   b  to the perforation holes  126   a.  Then, the lower perpendicular parts  164  of the guide frames  160  are approximately level with the upper perpendicular parts  256  of the outer rails  250 , and the guide frames  160  do not contact the intermediate rails  260  or inner rails  270 .  
         [0076]     Next, the slide rails  240  are unscrewed from the housing  101  from the inner side while the disc array storage  100  is gradually inserted into the rack mount apparatus  200  (step  1104 ).  FIG. 12  shows this state.  
         [0077]     As the user inserts the disc array storage  100  into the rack mount apparatus  200  via the grips  142 , the lower inclined parts  165  contact the upper perpendicular parts  256  of the outer rails  250 . As the disc array storage  100  is further inserted into the rack mount apparatus  200 , the inclined parts  165  go on the outer rails  250 . Since the perpendicular parts  164  have the inclined parts  165  at the ends  161   b,  they easily go on the outer rails  250 . The inclined parts may be provided to the outer rails  250  instead of the perpendicular parts  164 . As a result, the guide rails  160  are placed on the slide rails  240 .  
         [0078]     After the screws  190  that are closest to the front surface are detached by repeating the above operation, the provisional fixtures between the housing  101  and the rack mount apparatus  200  or between the housing  101  and the slide rails  240  are released by squeezing the engagement parts  156  of the flat springs  150  (step  1106 ). Then, the user draws the disc array storage  100  from the rack mount apparatus  200  (step  1108 ). The inner rails  270  that project from the housing  210  are squeezed into the housing  210  in step  1106  or  1108 .  
         [0079]     Further, the present invention is not limited to these preferred embodiments, and various variations and modifications may be made without departing from the scope of the present invention. For example, the above embodiment discusses the unit as the 2.5-inch HDD unit and a 3.5-inch HDD unit and other sized units are applicable.  
         [0080]     Thus, the present invention can provide an electronic apparatus, a rack mount apparatus and a mounting method, in which the electronic apparatus can be easily mounted on the rack mount apparatus.