Patent Publication Number: US-2015070830-A1

Title: Electronic equipment housing device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-185226, filed on Sep. 6, 2013, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiment discussed herein is related to an electronic equipment housing device. 
     BACKGROUND 
       FIG. 12  is a trihedral figure illustrating a state of a disc enclosure in a conventional rack mount device and  FIG. 13  illustrates a method of cooling the disc enclosure.  FIGS. 12 and 13  illustrate a top face (at center in the drawings), a front face (at right in the drawings), and a rear face (at left in the drawings) of the disc enclosure  8 . 
     The rack mount device not depicted, such as a storage server, includes a rack  91 . A device such as the disc enclosure  8  (which will be simply referred to as enclosure  8 , hereinbelow) is mounted in the rack  91 . 
     A plurality of (24 at maximum, for instance) hard disk drives (HDDs)  801  are arranged and mounted on front side (right side in  FIG. 12 ) in a cabinet  800  of the enclosure  8 . One or more (two in an example illustrated in  FIG. 12 ) fans  802  are mounted on rear side (left side in  FIG. 12 ) in the cabinet  800  of the enclosure  8 . 
     The fans  802  produce air flow in the cabinet  800  and thereby cool the HDDs  801 . In the conventional enclosure, as illustrated in  FIG. 13 , the HDDs  801  and the like are cooled by production of the air flow from the front side toward the rear side in the cabinet  800 . 
     Japanese Laid-open Patent Publication Nos. 2005-182610, 8-203264, 2008-251067, and 2001-148589 are examples of related art. 
     Depth of the rack  91  in the rack mount device is on the order of 900 to 1,000 mm in general. By contrast, depth of the enclosure  8  mounted in the rack  91  is on the order of 650 mm. Accordingly, there is a problem in that an extra space (dead space, see shaded parts in  FIGS. 12 and 13 ) with a depth of about 300 mm is formed in rear of the enclosure  8  in the rack  91  and deteriorates space efficiency. 
     Therefore, it is conceivable to extend the housing  800  of the enclosure  8  in front-rear direction and to arrange the HDDs  801  in two rows in front and rear by arranging a plurality of HDDs  801  in another row in rear of the HDDs  801  arranged in a row along the front face of the enclosure  8 , as illustrated in  FIG. 14 . 
       FIG. 14  is a plan view illustrating another mode of the disc enclosure in the conventional rack mount device. 
     In the disks  801  arranged in front and rear in  FIG. 14 , the plurality of disks  801  arranged in the row along the front face are referred to as front disk row  801   a  and the plurality of disks  801  arranged in the row in rear of and in parallel with the front disk row  801   a  are referred to as rear disk row  801   b.    
     The enclosure  8  illustrated in  FIG. 14  has a problem in that it is difficult to carry out maintenance work on the rear disk row  801   b.    
     In the enclosure  8  illustrated in  FIG. 14 , the air flow produced by the fans  802  placed on the rear side in the cabinet  800  cools the front disk row  801   a  and thereafter reaches the rear disk row  801   b.    
     Accordingly, the air flow increased in temperature by cooling the front disk row  801   a  flows into the rear disk row  801   b . Thus another problem is caused in that decrease in cooling efficiency for the HDDs  801  of the rear disk row  801   b  results in decrease in product life. 
     SUMMARY 
     According to an aspect of the invention, an electronic equipment housing device includes: a first housing part in which first electronic equipment is housed; a second housing part in which second electronic equipment is housed; and a connecting and disconnecting mechanism that switches a spaced state in which the second housing part is spaced apart from the first housing part and a close state in which the second housing part is made close to the first housing part. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an expanded state of a storage device as an example of an embodiment; 
         FIG. 2  is a perspective view illustrating a housed state of the storage device as the example of the embodiment; 
         FIGS. 3A and 3B  are side views illustrating operations of a connecting and disconnecting mechanism in the storage device as the example of the embodiment; 
         FIG. 4  is a perspective view illustrating an appearance of the housed state of the storage device as the example of the embodiment; 
         FIG. 5  is a perspective view illustrating an appearance of the expanded state of the storage device as the example of the embodiment; 
         FIGS. 6A ,  6 B, and  6 C illustrate paths of air flow that cools a rear disk row in the housed state of the storage device as the example of the embodiment; 
         FIG. 7  is an outside drawing illustrating an example of a duct in the storage device as the example of the embodiment; 
         FIG. 8  is a perspective view illustrating an appearance of rear side of an HDD shelf in the storage device as the example of the embodiment; 
         FIG. 9  is a perspective view illustrating paths of air flow in the expanded state of the storage device as the example of the embodiment; 
         FIGS. 10A ,  10 B, and  10 C illustrate paths of air flow that cools a front disk row in the housed state of the storage device as the example of the embodiment; 
         FIG. 11  is a perspective view illustrating a housed state of the storage device as a modification of the embodiment; 
         FIG. 12  is a trihedral figure illustrating a state of a disc enclosure in a conventional rack mount device; 
         FIG. 13  illustrates a method of cooling the disc enclosure in the conventional rack mount device; and 
         FIG. 14  is a plan view illustrating another mode of the disc enclosure in the conventional rack mount device. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinbelow, an embodiment of an electronic equipment housing device will be described with reference to the accompanying drawings. The embodiment described below, however, is merely exemplary and is not intended to exclude application of various modifications and techniques that are not specified for the embodiment. That is, the embodiment may be implemented with various modifications without departing from purport of the embodiment. The drawings do not imply provision of only components illustrated in the drawings but allow inclusion of other functions and the like. 
       FIG. 1  is a perspective view illustrating an expanded state of a storage device as an example of the embodiment, and  FIG. 2  is a perspective view illustrating a housed state of the storage device. In  FIGS. 1 and 2 , depiction of a base unit cover  123 , ducts  141 ,  141 , and an HDD shelf cover  113  that are illustrated in  FIGS. 4 ,  5 , and the like is omitted for description on inner configuration of the storage device  1 . 
     The storage device (electronic equipment housing device)  1  is an electronic device that is to be mounted in a rack mount device not illustrated and is inserted into a slot formed in a rack of the rack mount device. 
     As illustrated in  FIG. 1 , the storage device  1  includes a base unit  12 , an HDD shelf  11 , and a connecting and disconnecting mechanism  13  and is configured so that the connecting and disconnecting mechanism  13  connects the base unit  12  and the HDD shelf  11 . 
     The base unit (first housing part)  12  detachably includes one or more (sixteen in the example illustrated in  FIG. 1 ) memory devices (first electronic devices)  101  on a rectangular base  121  and includes one or more (two in the embodiment) control units  16  and fans  14 ,  15 . 
     The sixteen memory devices (first electronic equipment)  101  are placed along one side of the base  121  so as to be orthogonal to the side and so as to be parallel with one another. Hereinbelow, a side on which the memory devices  101  are arranged and placed on the base  121  will be referred to as front side as illustrated in  FIG. 1 , for convenience. The plurality of memory devices  101  arranged and placed on the base  121  of the base unit  12  will be referred to as a rear disk row  101   b.    
     The memory devices  101  are hard disk drives (HDDs), solid state drives (SSDs), or the like, for instance. For the embodiment, the example in which the HDDs are used as the memory devices  101  is disclosed and the memory devices  101  will be represented as HDDs  101  hereinbelow. 
     The two control units  16  are arranged and placed in rear of the rear disk row  101   b  on the base  121 . Controller modules (CMs), power supply units (PSUs), and the like are installed in the control units  16 . The CMs control reading and writing of data on the HDDs  101 , communication with host devices not illustrated, and the like. The PSUs supply power to parts in the storage device  1 . 
     In the control units  16 , the fans (first air flow producing part, second air flow producing part)  14  are placed along a rear side of the base  121 . 
     Ventilation paths  201 ,  201  are placed along sides orthogonal to the front side described above on the base  121 . The ventilation paths  201  are pipe-like members each having a rectangular section, for instance. The fan (third air flow producing part)  15  is provided in rear end part of each of the ventilation paths  201 ,  201 . 
     Details of the fans  14 ,  15 , and the ventilation paths  201 ,  201  will be described later. 
     A backplane  17  is stood between the rear disk row  101   b  and the control units  16  on the base  121  so as to be parallel with the front side described above and so as to be orthogonal to the base  121 . The HDDs  101  on the base unit  12  are connected to connectors that are formed on the backplane  17  and that are not illustrated and are connected through the backplane  17  to the CMs and the PSUs in the control units  16 . 
     In front of the base  121 , a cable link guide  124  protrudes in parallel with the base  121 . The backplane  17  and a backplane  18  that is provided in the HDD shelf  11  and that will be described later are connected through a communication cable and a power cable that are not illustrated. The communication cable and the power cable are guided by the cable link guide  124 . 
     Side panels  122  are stood on the sides orthogonal to the front side described above on the base  121 . The connecting and disconnecting mechanism  13  that will be described later is connected to the side panels  122 . 
     The base unit cover  123  is placed on the base unit  12  so as to cover the rear disk row  101   b  and the control units  16  as illustrated in  FIGS. 4 and 5 , though depiction of the base unit cover  123  is omitted in the example illustrated in  FIGS. 1 and 2  for convenience. In the base unit  12 , in this manner, the rear disk row  101   b , the control units  16 , the fans  14 ,  15 , and the ventilation paths  201 ,  201  are placed in a space surrounded by the base  121 , the side panels  122 ,  122 , and the base unit cover  123 . 
     The HDD shelf (second housing part)  11  has one or more (twenty in the example illustrated in  FIG. 1 ) HDDs (second electronic devices)  101  on a rectangular base  111 . 
     The twenty HDDs  101  are placed along front side of the base  111  so as to be orthogonal to the side and so as to be parallel with one another. The plurality of HDDs  101  arranged and placed on the base  111  of the HDD shelf  11  will be referred to as a front disk row  101   a.    
     The backplane  18  is stood in rear of the front disk row  101   a  on the base  111  so as to be parallel with the front side described above and so as to be orthogonal to the base  111 . The HDDs  101  on the HDD shelf  11  are connected to connectors that are formed on the backplane  18  and that are not illustrated. The HDDs  101  on the HDD shelf  11  are connected through the backplane  18 , cables not illustrated, and the backplane  17  to the CMs and the PSUs in the control units  16 . 
     Side panels  112  are stood on sides orthogonal to the front side described above on the base  111 . 
     The connecting and disconnecting mechanism  13  is connected to the side panels  112 . The connecting and disconnecting mechanism  13  makes it possible to connect the base unit  12  and the HDD shelf  11 , to switch at will a spaced state (see  FIG. 1 ) in which the HDD shelf  11  and the base unit  12  are spaced apart and a close state (see  FIG. 2 ) in which the HDD shelf  11  and the base unit  12  are made close to each other, and to maintain each state. Hereinbelow, the spaced state, illustrated in  FIG. 1 , in which the HDD shelf  11  and the base unit  12  are spaced apart will be referred to as expanded state of the HDD shelf  11  or simply as expanded state. In addition, the close state, illustrated in  FIG. 2 , in which the HDD shelf  11  and the base unit  12  are made close to each other will be referred to as housed state of the HDD shelf  11  or simply as housed state. 
     When the storage device  1  with the HDD shelf  11  being in the housed state is stored into a slot of a rack not illustrated, the HDD shelf  11  and the base unit  12  are housed in the slot of the rack. That is, depth of the storage device  1  is configured so that the storage device  1  fits within the rack. When the HDD shelf  11  is brought into the expanded state, the HDD shelf  11  is protruded from the slot of the rack and the rear disk row  101   b  in the base unit  12  are exposed. 
       FIGS. 3A and 3B  are side views illustrating operations of the connecting and disconnecting mechanism  13  in the storage device  1  as the example of the embodiment.  FIG. 3A  illustrates the housed state and  FIG. 3B  illustrates the expanded state. 
     In the housed state of the HDD shelf  11 , as illustrated in  FIG. 3A , the base  111  of the HDD shelf  11  is flush with the base  121  of the base unit  12 . 
     As illustrated in  FIGS. 3A and 3B , the connecting and disconnecting mechanism  13  includes a plurality of links  131  through  135  and dampers  137 . As illustrated in  FIG. 1  and the like, the plurality of links  131  through  135  and the dampers  137  are provided in positions that are on both side faces of the HDD shelf  11  and the base unit  12  and that are opposed with the HDD shelf  11  and the base unit  12  in between. In the connecting and disconnecting mechanism  13 , namely, the links  131  through  135  and the dampers  137  that are provided on both the side faces of the HDD shelf  11  and the base unit  12  are paired and thereby perform respective functions. 
     The links  131  each have one end pivotally connected through a pivot  136   f  to the side panel  112  of the HDD shelf  11 . Thus the links  131 ,  131  hold the HDD shelf  11  from both sides of the HDD shelf  11 . The links  131  each have the other end pivotally connected through a pivot  136   a  to one end part of the link  135  and one end part of the link  132 . That is, the links  131 ,  131  pivot on the pivots  136   a  while holding the HDD shelf  11  and thereby function as a vertical moving mechanism that vertically moves the HDD shelf  11 . The links  131  have a shape bent like a letter L on a side near to the pivots  136   a.    
     The links  135  have a linear shape and are slidably guided in front-rear directions by guides  1351 ,  1351  that are arranged in the front-rear direction on the side panels  122  of the base unit  12 . The links  135  are restricted in vertical movement by the guides  1351 ,  1351  and support the links  131 ,  131  that hold the HDD shelf  11  in between as described above. 
     The links  135  that hold the HDD shelf  11  and the links  131 ,  131  in between move in the front-rear directions while being guided by the guides  1351 ,  1351 , and the HDD shelf  11  is thereby spaced apart from or made close to the base unit  12 . That is, the links  135  function as a horizontal moving mechanism that horizontally moves the HDD shelf  11  by being guided by the guides  1351 ,  1351  and that thereby changes distance from the base unit  12  to the HDD shelf  11 . 
     The links  134  each have one end pivotally connected through a pivot  136   e  to the side panel  122  of the base unit  12  and each have the other end pivotally connected through a pivot  136   d  to one end part of the link  133 . 
     The links  132 ,  133 , and the dampers  137  form a link mechanism  138  that connects the end parts of the links  135  on a side including the pivots  136   a  and end parts of the links  134  on a side including the pivots  136   d . The link mechanism  138  extensibly connects the end parts of the links  135  on the side including the pivots  136   a  and the end parts of the links  134  on the side including the pivots  136   d . By supporting the HDD shelf  11 , the link mechanism  138  distributes a load caused by the HDD shelf  11  and thus reduces concentration of the load on the links  135 . 
     In the link mechanism  138 , specifically, one end side of the link  133  is pivotally connected through the pivot  136   d  to the end part of the link  134  that is opposite to the pivot  136   e . The end part of the link  133  that is opposite to the pivot  136   d  is pivotally connected through a pivot  136   c  to one end part of the damper  137 . An end part of the damper  137  that is opposite to the end part thereof on the side including the pivot  136   c  is pivotally connected through the pivot  136   b  to one end side of the link  132 . 
     The dampers  137  are a device that reduces impact or amplitude of vibrations by dissipating vibrational energy and reduce impact and vibrations that are produced by expansion and contraction of the link mechanism  138 . The dampers  137 , which reduce the impact and vibrations that are produced by the expansion and contraction of the link mechanism  138 , make it possible to avoid transmission of the impact and vibrations to the HDDs  101  housed in the HDD shelf  11  and the base unit  12 . That is, the HDDs  101  may be protected from the impact and vibrations that are produced by switching between the expanded state and the housed state of the HDD shelf  11  in active state of the storage device  1 . The damper  137  are configured extensibly and contractibly. 
     The end part of the link  132  that is opposite to the end part thereof on the side including the pivot  136   b  is pivotally connected through the pivot  136   a  to the link  135  and the link  131 . 
     In the housed state of the HDD shelf  11 , as illustrated in  FIG. 3A , the link mechanism  138  is brought into a folded state. In the link mechanism  138 , specifically, the links  132 ,  133 , and the dampers  137  are folded by pivoting on the pivots  136   c  and  136   d . Then the dampers  137  contract. Thus the link mechanism  138  functions to decrease distance between the end part of the link  135  on the side including the pivot  136   a  and the end part of the link  134  on the side including the pivot  136   d.    
     When the HDD shelf  11  is housed, as illustrated in  FIG. 3A , the link mechanism  138  contracts and the links  135  move rearward by being guided by the guides  1351 ,  1351  in the connecting and disconnecting mechanism  13 , while the HDD shelf  11  is held from both the sides. 
     Thus the HDD shelf  11  is placed in a position in which the base  111  is flush with the base  121  of the base unit  12 , so that the housed state in which the HDD shelf  11  and the base unit  12  are close to each other is brought about. In the housed state, the HDD shelf  11  is laid on the cable link guide  124  and is thereby fixed in the state in which the HDD shelf  11  is close to the base unit  12 . 
     In the expanded state of the HDD shelf  11 , as illustrated in  FIG. 3B , the links  132 ,  133 , and the dampers  137  in the link mechanism  138  are expanded so as to be linear and support the HDD shelf  11 . Then the dampers  137  are extended. Thus the link mechanism  138  functions to increase the distance between the end part of the link  135  on the side including the pivot  136   a  and the end part of the link  134  on the side including the pivot  136   d.    
     When the HDD shelf  11  is in the expanded state, as illustrated in  FIG. 3B , the link mechanism  138  is extended and the links  135  move forward by being guided by the guides  1351 ,  1351  in the connecting and disconnecting mechanism  13 , while the HDD shelf  11  is held from both the sides. 
     Thus the HDD shelf  11  moves forward and away from the base unit  12 , so that the HDD shelf  11  and the base unit  12  are brought into the spaced state. By contact with the links  131  of stoppers not illustrated and protruding from the side panels  112 , for instance, pivoting of the HDD shelf  11  on the pivots  136   f  is blocked and the HDD shelf  11  is fixed so as to be horizontal in the expanded state. 
     In the expanded state of the HDD shelf  11 , a space that allows work such as maintenance for the HDDs  101  or the like mounted on the base unit  12  is ensured in front of the base unit  12 . 
     In the expanded state of the HDD shelf  11 , as illustrated in  FIGS. 1 and 3B , formation of an opening  12   a  on front face of the base unit  12  and exposure of the HDDs  101  mounted on the base unit  12  through the opening  12   a  make it possible to carry out work on the HDDs  101 . In the expanded state of the HDD shelf  11 , as will be described later, a state in which outside air (air) may flow through the opening  12   a  into the base unit  12  is brought about. 
     The storage device  1  as the example of the embodiment that is configured as described above is inserted in the housed state into the slot formed in the rack of the rack mount device. 
     An operator who performs maintenance work or the like draws out the HDD shelf  11  frontward in the storage device  1  inserted in the rack. 
     Then the links  132 ,  133 , and the dampers  137  of the link mechanism  138  having been in the folded state are expanded so as to be linear. Consequently, the links  135  move forward while being guided by the guides  1351 ,  1351 , and the HDD shelf  11  is thereby spaced apart from the base unit  12 . 
     The operator then makes the HDD shelf  11 , held between the links  131 ,  131 , pivot (move) downward on the pivots  136   a . Thus the HDD shelf  11  is positioned below the base unit  12  and the opening  12   a  is formed on the front face of the base unit  12  so that the rear disk row  101   b  is exposed. 
     Subsequently, a function of cooling the HDDs  101  in the storage device  1  will be described. 
       FIG. 4  is a perspective view illustrating an appearance of the housed state of the storage device as the example of the embodiment, and  FIG. 5  is a perspective view illustrating an appearance of the expanded state of the storage device. In  FIGS. 4 and 5 , illustration of some reference characters is omitted, for convenience. 
     As illustrated in  FIGS. 4 and 5 , the base unit  12  includes the base unit cover  123  that covers the rear disk row  101   b , the backplane  17 , the control units  16 , the ventilation paths  201 , and the like so as to conceal them. That is, the disk row  101   b , the backplane  17 , the control units  16 , and the ventilation paths  201  are placed in the space (base unit space) surrounded by the base  121 , the side panels  122 ,  122 , and the base unit cover  123 . 
     Similarly, the HDD shelf  11  includes the HDD shelf cover  113  that covers the front disk row  101   a  and the backplane  18  so as to conceal them. That is, the front disk row  101   a  and the backplane  18  are placed in a space (HDD shelf space) surrounded by the base  111 , the side panels  112 ,  112 , a bottom surface  1131 , and the HDD shelf cover  113 . 
       FIGS. 6A ,  6 B, and  6 C illustrate paths of air flow that cools the rear disk row  101   b  in the housed state of the storage device  1  as the example of the embodiment.  FIG. 6A  is a plan view illustrating the paths of the air flow in the storage device  1 .  FIG. 6B  is a section taken along line VIB-VIB of  FIG. 6A .  FIG. 6C  is an elevational view of the storage device  1 . 
     The HDD shelf cover  113  is shaped like a box surrounded by the bottom surface  1131 , side plates  1132 ,  1132 , a top plate  1133 , and a rear plate  1134  and is placed so that the bottom surface  1131  is over the front disk row  101   a  in the HDD shelf  11  and parallels the base  121 . The side plates  1132 ,  1132  are configured to be flush with the side panels  112 ,  112  of the HDD shelf  11 . 
     An opening  113   a  is formed on front face of the HDD shelf cover  113  and a current plate  1135  (see  FIG. 4 ) is provided in the opening  113   a.    
     In the housed state, as illustrated in  FIG. 6B , inner space of the HDD shelf cover  113  is connected to the base unit space in the base unit  12 . When the fans  14  in the base unit  12  are rotated in the housed state, accordingly, air taken in through the opening  113   a  of the HDD shelf cover  113  flows from the inner space of the HDD shelf cover  113  into the base unit space, as illustrated in  FIGS. 6A and 6B . 
     Specifically, the air taken in through the opening  113   a  of the HDD shelf cover  113  collides against the rear plate  1134 , flows downward in the inner space of the HDD shelf cover  113 , and flows into the base unit space. 
     The air having flowed into the base unit space passes through between the HDDs  101  of the rear disk row  101   b  and thereafter enters the control units  16 . When passing through between the HDDs  101 , the air cools the HDDs  101 . 
     In the housed state of the HDD shelf  11 , the inner space of the HDD shelf  11  thus functions as a guiding path that guides the air, taken in through the opening  113   a , to the rear disk row  101   b.    
     In the housed state, namely, the fans  14  produce the air flow that flows in through the guiding path and that passes through the HDDs  101  of the rear disk row  101   b.    
     After that, the air having entered the control units  16  cools the CMs and the PSUs in the control units  16 , passes through the fans  14 , and is discharged from rear side of the base unit  12 . 
     In the housed state of the HDD shelf  11 , in this manner, the rear disk row  101   b  is cooled by the air flow that is taken in through the opening  113   a  of the HDD shelf cover  113  and that is guided by the inner space of the HDD shelf  11 . 
     The HDD shelf space surrounded by the base  111 , the side panels  112 ,  112 , and the bottom surface  1131  of the HDD shelf cover  113  in the HDD shelf  11  communicates with the ducts  141 ,  141 . On rear side (side facing the base unit  12 ) of the HDD shelf space, specifically, the ducts  141  couple the HDD shelf space to the ventilation paths  201  of the base unit  12 . 
       FIG. 7  is an outside drawing illustrating an example of the duct  141  in the storage device  1  as the example of the embodiment. 
     The duct  141  is a bellows hose having a rectangular section as illustrated in  FIG. 7  and expands or contracts in accordance with the distance between the HDD shelf  11  and the base unit  12 . The duct  141  is not limited to the bellows hose, may be configured with use of members that are made of rubber, for instance, and that expand or contract through agency of elasticity, and may be implemented with various modifications. 
       FIG. 8  is a perspective view illustrating an appearance of rear side of the HDD shelf  11  in the storage device  1  as the example of the embodiment. In  FIG. 8 , only a portion is extracted and depicted, for convenience. 
     As illustrated in  FIG. 8 , a rear plate  1121  is stood along rear side of the base  111  in rear part of the HDD shelf  11 . In the rear part of the HDD shelf  11 , rear openings  11   b ,  11   b  are formed between the rear plate  1121  and the side panels  112 . Ends on one side of the ducts  141  described above are connected to the rear openings  11   b ,  11   b . In  FIG. 8 , the ducts  141  and the rear openings  11   b  in a separated state are illustrated, for convenience, for depiction of positional relation between the ducts  141  and the rear openings  11   b.    
     As illustrated in  FIG. 9 , air having entered through the front opening  11   a  on the HDD shelf  11  thus enters the ducts  141  through the rear openings  11   b ,  11   b.    
       FIG. 9  is a perspective view illustrating paths of air flow in the expanded state of the storage device  1  as the example of the embodiment. In  FIG. 9 , the paths of the air flow that cools the front disk row  101   a  are represented by arrows of chain lines, and the paths of the air flow that cools the rear disk row  101   b  are represented by arrows of dashed thick lines. In  FIG. 9 , only a portion is extracted and depicted, for convenience. 
     In the expanded state of the HDD shelf  11  in such a configuration as described above, the rear disk row  101   b  is cooled by rotation of the fans  14 ,  14  in the base unit  12 . With the rotation of the fans  14 ,  14 , namely, the air sucked through the front opening  12   a  on the base unit  12  passes through between the HDDs  101  of the rear disk row  101   b  and thereafter enters the control units  16 . When passing through between the HDDs  101 , the air cools the HDDs  101 . 
     After that, the air having entered the control units  16  cools the CMs and the PSUs in the control units  16 , passes through the fans  14 , and is discharged from the rear side of the base unit  12 . 
     In the expanded state, namely, the fans  14  produce the air flow that flows in through the opening  12   a  of the base unit  12  and that passes through the HDDs  101  of the rear disk row  101   b.    
     In the expanded state of the HDD shelf  11 , the front disk row  101   a  is cooled by rotation of the fans  15 ,  15  in the base unit  12 . With the rotation of the fans  15 ,  15 , namely, the air sucked through the front opening  11   a  on the HDD shelf  11  passes through between the HDDs  101  of the front disk row  101   a  and thereafter enters the ducts  141 ,  141 . When passing through between the HDDs  101 , the air cools the HDDs  101 . 
     In the expanded state of the HDD shelf  11 , the front disk row  101   a  is thus cooled by the air sucked through the front opening  11   a  on the HDD shelf  11 . 
     After that, the air having entered the ducts  141  passes through the ventilation paths  201 ,  201 , thereafter passes through the fans  15 , and is discharged from the rear side of the base unit  12 . 
     In the expanded state, namely, the fans  15  produce the air flow that flows in through the opening  11   a  formed on the HDD shelf  11 , that passes through the HDDs  101  of the front disk row  101   a , and that thereafter passes through the ducts  141 . 
     The air used for cooling the front disk row  101   a  passes through the rear openings  11   b ,  11   b , the ducts  141  in an extended state, and the ventilation paths  201 ,  201 , thereafter passes through the fans  15 , and is discharged from the rear side of the base unit  12 . 
       FIGS. 10A ,  10 B, and  10 C illustrate the paths of the air flow that cools the front disk row  101   a  in the housed state of the storage device  1  as the example of the embodiment.  FIG. 10A  is a plan view illustrating the paths of the air flow in the storage device  1 .  FIG. 10B  is a section taken along line XB-XB of  FIG. 10A .  FIG. 10C  is an elevational view of the storage device  1 . 
     The ducts  141  described above are contracted in the housed state and thus depiction of the ducts  141  is omitted in  FIGS. 10A ,  10 B, and  10 C. 
     The inner space (HDD shelf space) of the HDD shelf  11  is coupled through the ducts  141  to the ventilation paths  201  as described above. When the fans  15  in the ventilation paths  201  are rotated in the housed state, accordingly, the air taken in through the opening  11   a  of the HDD shelf  11  flows into the HDD shelf space, as illustrated in  FIGS. 10A and 10B . 
     The air having flowed in passes through between the HDDs  101  of the front disk row  101   a  in the HDD shelf space. When passing through between the HDDs  101 , the air cools the HDDs  101 . 
     After passing through the front disk row  101   a , the air passes through the rear openings  11   b ,  11   b  and the ducts  141  in a contracted state and flows into the ventilation paths  201 ,  201 . 
     In the housed state also, namely, the fans  15  produce the air flow that flows in through the opening  11   a  formed on the HDD shelf  11 , that passes through the HDDs  101  of the front disk row  101   a , and that thereafter passes through the ducts  141 . 
     Also in the housed state of the HDD shelf  11 , the front disk row  101   a  is thus cooled by the air taken in through the opening  11   a  on the HDD shelf  11 . The air used for the cooling passes through the rear openings  11   b ,  11   b , the ducts  141  in the contracted state, and the ventilation paths  201 ,  201 , thereafter passes through the fans  15 , and is discharged from the rear side of the base unit  12 . 
     According to the storage device  1  as the example of the embodiment, in this manner, the spaces in the storage device  1  may efficiently be used because the HDDs  101  may be housed in the base unit  12  and in the HDD shelf  11  so that a large number of HDDs  101  may be housed in the storage device  1 . 
     Besides, the HDD shelf  11  is brought into the expanded state by the connecting and disconnecting mechanism  13 , so that maintenance on the HDDs  101  of the rear disk row  101   b  may easily be performed. That is, improvement in maintainability and increase in convenience are attained. 
     The HDD shelf  11  may be spaced apart from the base unit  12  by being moved forward and horizontally by the links  135  guided by the guides  1351 ,  1351 . Thus it is made possible to easily access the rear disk row  101   b , and the space that allows performance of maintenance work on the HDDs  101  of the rear disk row  101   b  is ensured in front of the base unit  12 . 
     The HDD shelf  11  may be positioned below the base unit  12  in the expanded state by the downward movement of the HDD shelf  11  around the pivots  136   a  in the state in which the HDD shelf  11  is held between the links  131 ,  131 . Thus interference by the HDD shelf  11  with access to the rear disk row  101   b  is reduced, so that the access to the rear disk row  101   b  is further improved. 
     In addition, the front disk row  101   a  in the HDD shelf  11  and the rear disk row  101   b  in the base unit  12  may separately be cooled in the housed state of the HDD shelf  11 . As a result, shortening of life of the HDDs  101  may be reduced and reliability may be increased. 
     That is, the rear disk row  101   b  may be cooled in the housed state of the HDD shelf  11  by the air that is taken in through the opening  113   a  of the HDD shelf cover  113  and that is guided by the inner space of the HDD shelf  11 . 
     In the expanded state of the HDD shelf  11 , the rear disk row  101   b  is cooled by the air sucked through the front opening  11   a  on the HDD shelf  11 . 
     Thus the rear disk row  101   b  may be cooled in both the housed state and the expanded state of the HDD shelf  11 . 
     The front disk row  101   a  is cooled by the air taken in through the opening  11   a  of the HDD shelf  11  in both the housed state and the expanded state of the HDD shelf  11 . The air used for the cooling passes through the rear openings  11   b ,  11   b , the ducts  141 , and the ventilation paths  201 ,  201 , thereafter passes through the fans  15 , and is discharged from the rear side of the base unit  12 . 
     The ducts  141  are in the contracted state when the HDD shelf  11  is in the housed state or are in the extended state when the HDD shelf  11  is in the expanded state. Thus the air taken in through the opening  11   a  of the HDD shelf  11  may be discharged through the fans  15  in both the housed state and the expanded state of the HDD shelf  11 . 
     Thus the front disk row  101   a  may be cooled in both the housed state and the expanded state of the HDD shelf  11 . 
     Techniques disclosed herein are not limited to the embodiment described above and may be implemented with various modifications without departing from purport of the embodiment. 
     In the embodiment described above, for instance, the connecting and disconnecting mechanism  13  includes the five pairs of links  131  through  135  and the dampers  137  and is folded by the pivoting of the links  132 ,  133 , and the dampers  137  on the pivots  136   c  and  136   d  in the housed state of the HDD shelf  11 . Configuration of the connecting and disconnecting mechanism  13 , however, is not limited to above. The connecting and disconnecting mechanism  13  may include four or less pairs or six or more pairs of links and may be implemented with various modifications. 
     Though the connecting and disconnecting mechanism  13  includes the dampers  137  in the embodiment described above, the connecting and disconnecting mechanism  13  is not limited to the embodiment and may include simple links  137 ′ in place of the dampers  137 . 
       FIG. 11  is a perspective view illustrating a housed state of the storage device as a modification of the embodiment. 
     The storage device  1  illustrated in  FIG. 11  includes a connecting and disconnecting mechanism  13 ′ in place of the connecting and disconnecting mechanism  13  of the storage device  1  illustrated in  FIG. 2 . The connecting and disconnecting mechanism  13 ′ includes the simple links  137 ′ in place of the dampers  137 . Thus production costs for the connecting and disconnecting mechanism  13 ′ may be reduced. 
     Numbers of the HDDs  101  housed in the base unit  12  and the HDD shelf  11  are not limited to numbers disclosed in the embodiment described above and may be set with various modifications. 
     Though the storage device  1  that houses the memory devices  101  as electronic devices has been described for the embodiment described above, the electronic devices are not limited to above and may be implemented with various modifications. For instance, electronic devices such as information processing devices and communication devices, other than memory devices, may be housed as the electronic devices. Electronic devices stored in the base unit  12  and electronic devices stored in the HDD shelf  11  may be different. 
     According to disclosure described above, the embodiment may be implemented and produced by a person skilled in the art. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment of the present invention has been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.