Abstract:
There is provided a power supply system including: a first busbar provided to extend in a predetermined direction on a first member, the first busbar being conductive and supplied with electricity; a second busbar provided to extend in the predetermined direction on a second member relatively movable with respect to the first member in the predetermined direction, the second busbar being conductive and spaced apart facing the first busbar; two rollers provided between the first busbar and the second busbar facing each other, the two rollers being aligned with respect to each other in the predetermined direction; and a belt configured to wind and rotate around the two rollers so as to contact with the first busbar and the second busbar with a surface contact thereof, the belt being conductive.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-231413, filed on Nov. 7, 2013, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a power supply system and a rack mount apparatus. 
       BACKGROUND 
       [0003]    As a form of mobile electrical apparatus that receives electric signals such as a control signal, Japanese Laid-open Utility Model Publication No. 01-77292 discusses a known signal transmission device that includes a mobile electrical apparatus that transmits and receives a control signal to and from a signal transmission conductor via a current collecting roller. 
       SUMMARY 
       [0004]    According to an aspect of the invention, a power supply system includes: a first busbar provided to extend in a predetermined direction on a first member, the first busbar being conductive and supplied with electricity; a second busbar provided to extend in the predetermined direction on a second member relatively movable with respect to the first member in the predetermined direction, the second busbar being conductive and spaced apart facing the first busbar; two rollers provided between the first busbar and the second busbar facing each other, the two rollers being aligned with respect to each other in the predetermined direction; and a belt configured to wind and rotate around the two rollers so as to contact with the first busbar and the second busbar with a surface contact thereof, the belt being conductive. 
         [0005]    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. 
         [0006]    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 
         [0007]      FIG. 1  is a perspective view illustrating a device according to a first embodiment; 
           [0008]      FIG. 2  is a perspective view of the device illustrated in  FIG. 1 , which illustrates a state in which the tray is drawn out; 
           [0009]      FIG. 3  is a perspective view of an example in which the device is mounted in a rack; 
           [0010]      FIG. 4  is an exploded perspective view illustrating a power supply system according to an embodiment; 
           [0011]      FIG. 5  is a perspective view illustrating the power supply system in an assembled state; 
           [0012]      FIG. 6  illustrates three orthographic views of a relay mechanism; 
           [0013]      FIG. 7  is a perspective view of components of the relay mechanism that have been picked out; 
           [0014]      FIG. 8  is a diagram illustrating an exemplary state in which a first busbar is mounted in a housing; 
           [0015]      FIG. 9  is a diagram illustrating an exemplary state in which the relay mechanism is mounted in the housing; 
           [0016]      FIG. 10  is an enlarged view of portion X of  FIG. 9 ; 
           [0017]      FIG. 11  is a perspective view illustrating an exemplary state seen from the front side in which a second busbar is mounted to the tray; 
           [0018]      FIG. 12  is a perspective view illustrating an exemplary state seen from the rear side in which the second busbar is mounted to the tray; 
           [0019]      FIGS. 13A and 13B  are each a diagram illustrating the manner in which the relay mechanism is connected to each of the first busbar and the second busbar; 
           [0020]      FIGS. 14A and 14B  are each a top view illustrating the manner in which the relay mechanism moves upon movement of the tray; 
           [0021]      FIG. 15  is a perspective view illustrating a device according to a second embodiment; 
           [0022]      FIG. 16  is a perspective view of the device illustrated in  FIG. 15 , which illustrates a state in which the tray is drawn out; 
           [0023]      FIG. 17  is an exploded perspective view illustrating a power supply system according to the second embodiment; 
           [0024]      FIGS. 18A and 18B  are diagrams each illustrating an exemplary state in which a first busbar is mounted in the housing; 
           [0025]      FIGS. 19A and 19B  are perspective views each illustrating an exemplary state seen from the front side in which a second busbar is mounted to the tray; 
           [0026]      FIG. 20  is a perspective view illustrating an exemplary state seen from the rear side in which the second busbar is mounted to the tray; 
           [0027]      FIG. 21  illustrates three orthographic views of a relay mechanism; 
           [0028]      FIG. 22  is a perspective view of components of the relay mechanism that have been picked out; 
           [0029]      FIGS. 23A and 23B  are each a diagram illustrating connection portions between the relay mechanism and each of the first busbar and the second busbar; 
           [0030]      FIGS. 24A and 24B  are each a top view illustrating the manner in which the relay mechanism moves upon movement of the tray; and 
           [0031]      FIG. 25  is an explanatory drawing of a protective cover and a protective flange of the tray. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0032]    In the configuration described in BACKGROUND, the current collecting roller and the signal transmission conductor are in line contact with each other; accordingly, when the configuration is applied to a power supply system, since the contact area is small, the contact resistance becomes high making it difficult to distribute a high current. 
         [0033]    Hereinafter, embodiments of a power supply system and a rack mount apparatus that are capable of supplying electric power in a stable and efficient manner will be described in detail with reference to the accompanying drawings. 
       First Embodiment 
       [0034]      FIG. 1  is a perspective view illustrating a device  1  according to the first embodiment.  FIG. 2  is a perspective view of the device  1  illustrated in  FIG. 1 , which illustrates a state in which a tray  200  is drawn out.  FIG. 3  is a perspective view of an example in which the device is mounted in a rack. 
         [0035]    In  FIGS. 1 and 2 , a portion of the interior of the device  1  is illustrated in a transparent view depicted with dotted lines. Note that in the following description, in order to facilitate the description, the Y1 side of  FIG. 1  in the Y direction is the front side of the device  1  and the Y2 side is the rear side of the device  1 . Furthermore, the Z1 side of  FIG. 1  in the Z direction is the upper side of the device  1  and the Z2 side is the lower side of the device  1 . 
         [0036]    The device  1  is mounted in a rack  70  as illustrated in  FIG. 3 , and the rack  70  is able to mount a plurality of devices  1 . 
         [0037]    As illustrated in  FIGS. 1 and 2 , the device  1  includes a housing  100  (an example of a first member) and the tray  200  (an example of a second member). The tray  200  may be drawn out from or pushed into the housing  100  by being translated in the Y direction with respect to the housing  100 .  FIG. 1  illustrates a state in which the housing  100  is housed in (pushed in) the tray  200  and  FIG. 2  illustrates a state in which the housing  100  is drawn out from the tray  200 . 
         [0038]    The housing  100  takes a form of a case and houses therein the tray  200  and electronic components mounted on the tray  200 . The housing  100  is fixed to the rack  70 . Accordingly, the housing  100  is an element of the rack  70 . As illustrated in  FIGS. 1 and 2 , a single housing  100  may house a single tray  200  or may house a plurality of trays  200 . The front side of the housing  100  is open. The tray  200  may be drawn out or pushed in through the front side of the housing  100  by being translated in the Y direction with respect to the housing  100 . Note that the lateral sides of the housing  100  may be closed and the rear side may be open or closed. 
         [0039]    As schematically illustrated with the dotted lines in  FIGS. 1 and 2 , the housing  100  may be equipped with a power source  20 . In the examples illustrated in  FIGS. 1 and 2 , the power source  20  takes a form of a power supply unit (PSU). The power source  20  may be mounted inside any portion of the housing  100  and, as illustrated in  FIGS. 1 and 2 , may be mounted inside the housing  100  on the rear lateral side. Note that the power source  20  may be mounted inside the rack  70  and outside of the housing  100 , alternatively, the power source  20  may be mounted outside the rack  70 . 
         [0040]    Various electronic components according to the function of the device  1  are mounted on the tray  200 . The various electronic components typically include hot-swap parts. Hot-swap parts are, for example, parts and electronic equipment that are in an active state (operating state) up to the point when the parts and the electronic equipment are removed for replacement (hot-swap). The hot-swap parts may include, for example, a hard disk drive, a fan, a Peripheral Component Interconnect (PCI) cassette, and a memory. Furthermore, the tray  200  may take a form of a blade server in which the entire tray  200  is a hot-swap part. In the examples illustrated in  FIGS. 1 and 2 , a plurality of hard disk drives  10  and a plurality of fans  12  are mounted on the tray  200 , as examples of the hot-swap parts. 
         [0041]    Note that as described above, the tray  200  may be drawn out from the housing  100 . When the tray  200  is drawn out, an operator may access not only the hot-swap parts on the front side of the tray  200  (the hard disk drives  10 , for example) but also the hot-swap parts on the rear side (the fans  12 , for example). Accordingly, during maintenance work, the operator may draw out the tray  200  and gain access to any of the hot-swap parts. With only the space on the front side of the housing  100 , the number of hot-swap parts that may be mounted will be limited; however, by providing the drawer type tray  200 , more hot-swap parts may be mounted in the housing  100 . 
         [0042]    An example of the power supply system of the device  1  will be described next. 
         [0043]      FIG. 4  is an exploded perspective view illustrating a power supply system  300  according to an embodiment.  FIG. 5  is a perspective view illustrating the power supply system  300  in an assembled state. Note that a portion of a first busbar  310  and a portion of a second busbar  320 , more specifically, for example, a first busbar  311  on the upper side and a second busbar  321  on the upper side, respectively, are not shown in  FIGS. 4 and 5  in order to facilitate visual understanding. 
         [0044]    As illustrated in  FIGS. 4 and 5 , the power supply system  300  includes the first busbar  310 , the second busbar  320 , and a relay mechanism  330 . 
         [0045]    In the present embodiment, the first busbar  310  includes, as illustrated in  FIG. 1 , the first busbar  311  on the upper side and a first busbar  312  on the lower side and the second busbar  320  includes, as illustrated in  FIG. 2 , the second busbar  321  on the upper side and a second busbar  322  on the lower side. Meanwhile, the relay mechanism  330  includes a relay mechanism  330 A on the upper side and a relay mechanism  330 B on the lower side in an integrated manner. The first busbar  311  on the upper side, the second busbar  321  and the upper side, and the relay mechanism  330 A on the upper side are provided for a ground voltage, for example. The first busbar  312  on the lower side, the second busbar  322  on the lower side, and the relay mechanism  330 B on the lower side are provided for a source voltage, for example. That is, the power supply system  300  integrally includes a mechanism that separately supplies a ground voltage and a source voltage for supplying electric power from the power source  20  to the hot-swap parts on the tray  200 . However, a mechanism that supplies the ground voltage and a mechanism that supplies the source voltage may be provided in the power supply system  300  in a separate manner. Furthermore, the power supply system  300  may only include the mechanism that supplies the source voltage, and another component may be adopted as for the mechanism that supplies the ground voltage. 
         [0046]    The first busbar  310  is formed of a conductive material such as a conductor metal (copper, for example). Different from a cable, the first busbar  310  typically includes a planar contact surface (a surface described later that is in contact with a belt  336 ). Corresponding to the direction in which the tray  200  is drawn out, the first busbar  310  extends in the Y direction. When the line normal to the first busbar  310  extends in the X direction, the contact surface of the first busbar  310  is formed on the X1 side of the first busbar  310 . Note that as described above and as illustrated in  FIGS. 1 and 2 , the first busbar  310  may include the first busbar  311  on the upper side and the first busbar  312  on the lower side. In such a case, the first busbar  311  on the upper side and the first busbar  312  on the lower side are electrically insulated with each other. 
         [0047]    The second busbar  320  is formed of a conductive material such as a conductor metal (copper, for example). Different from a cable, the second busbar  320  typically includes a planar contact surface (a surface described later that is in contact with the belt  336 ). Corresponding to the direction in which the tray  200  is drawn out, the second busbar  320  extends in the Y direction. When the line normal to the second busbar  320  extends in the X direction, the contact surface of the second busbar  320  is formed on the X2 side of the second busbar  320 . The contact surface of the second busbar  320  is spaced apart from and faces the contact surface of the first busbar  310  in the X direction. A width (a length in the Z direction) of the contact surface of the second busbar  320  may be the same as a width of the contact surface of the first busbar  310 . Note that the second busbar  320  is preferably provided at the same position as the first busbar  310  in the Z direction. Note that as described above and as illustrated in  FIG. 2 , the second busbar  320  may include the second busbar  321  on the upper side and the second busbar  322  on the lower side. In such a case, the second busbar  321  on the upper side and the second busbar  322  on the lower side are electrically insulated with each other. 
         [0048]    The relay mechanism  330  is provided between the first busbar  310  and the second busbar  320  in the X direction and relays the electrical connection between the first busbar  310  and the second busbar  320 . In other words, the relay mechanism  330  electrically connects the first busbar  310  to the second busbar  320 . Note that as described above and as illustrated in  FIGS. 4 and 5 , the relay mechanism  330  may include the relay mechanism  330 A on the upper side and the relay mechanism  330 B on the lower side. In such a case, the relay mechanism  330 A on the upper side and the relay mechanism  330 B on the lower side are electrically insulated with each other. 
         [0049]      FIG. 6  illustrates three orthographic views of the relay mechanism  330 .  FIG. 7  is a perspective view of components of the relay mechanism  330  that have been picked out. Note that among first rollers  332  and second rollers  334 , only the first rollers  332  are illustrated in  FIG. 7  as a representative example. Note that in the present embodiment, the relay mechanism  330  includes the relay mechanism  330 A on the upper side and the relay mechanism  330 B on the lower side as described above and the components of the relay mechanism  330 A and those of the relay mechanism  330 B are basically the same and the same reference numerals are attached thereto. 
         [0050]    The relay mechanism  330 A includes the first roller  332 , the second roller  334 , and the belt  336 . Furthermore, the relay mechanism  330 A preferably includes an elastic member  338  as illustrated in  FIG. 6 . 
         [0051]    In a similar manner, the relay mechanism  330 B includes the first roller  332 , the second roller  334 , and the belt  336 . Furthermore, the relay mechanism  330 B preferably includes the elastic member  338  as illustrated in  FIG. 6 . 
         [0052]    The first rollers  332  are rotatable about a shaft portion  332   a.  The first rollers  332  each have a cylindrical shape with a predetermined height. The predetermined height is preferably slightly greater than a width (a length in the Z direction) of the belt  336 . The first rollers  332  may be formed of any material such as resin or metal. The shaft portion  332   a  may be formed of resin, for example. As illustrated in  FIGS. 6 and 7 , a single shaft portion  332   a  that is shared by the upper and lower first rollers  332  may be provided. As illustrated in  FIGS. 6 and 7 , the shaft portion  332   a  may include an enlarged diameter portion at each of the upper and lower ends thereof. Note that a bearing  333  may be provided around the shaft portion  332   a.  Note that when the first rollers  332  are formed of metal, the bearing  333  may be formed of an insulating material. Similar to the shaft portion  332   a,  a single bearing  333  that is shared by the upper and lower first rollers  332  may be provided. Furthermore, when the first rollers  332  are formed of a nonconductive material such as resin and when electrical insulation between each first roller  332  and the corresponding belt  336  is secured, a single first roller  332  that is shared by the upper and lower relay mechanisms  330 A and  330 B may be provided. 
         [0053]    Similarly, the second rollers  334  are rotatable about a shaft portion  334   a.  The second rollers  334  each have a cylindrical shape with a predetermined height (a length in the Z direction). The predetermined height is preferably slightly greater than the width (the length in the Z direction) of the belt  336 . The outer diameter of each second roller  334  may be the same as the outer diameter of each first roller  332 . The second rollers  334  may be formed of any material such as resin or metal. The shaft portion  334   a  may be formed of resin, for example. As illustrated in  FIGS. 6 and 7 , a single shaft portion  334   a  that is shared by the upper and lower second rollers  334  may be provided. As illustrated in  FIGS. 6 and 7 , the shaft portion  334   a  may include an enlarged diameter portion at each of the upper and lower ends thereof. Note that a bearing  335  may be provided around the shaft portion  334   a.  Note that when the second rollers  334  are formed of metal, the bearing  335  may be formed of an insulating material. Similar to the shaft portion  334   a,  a single bearing  335  that is shared by the upper and lower second rollers  334  may be provided. Furthermore, when the second rollers  334  are formed of a nonconductive material such as resin and when the electrical insulation between each second roller  334  and the corresponding belt  336  is secured, a single second roller  334  that is shared by the upper and lower relay mechanisms  330 A and  330 B may be provided. 
         [0054]    The first rollers  332  and the second rollers  334  are preferably aligned in the Y direction with respect to one another such that the linear portions (contact surfaces) of the belts  336  extend in the Y direction. In other words, a line connecting the rotation center of a first roller  332  and the rotation center of a corresponding second roller  334  is parallel to the Y direction. 
         [0055]    The belts  336  are each formed of a conductive material, such as copper or conductive rubber. As illustrated in  FIG. 6 , each of the belts  336  is provided around the corresponding first roller  332  and second roller  334 . The belts  336  are each an endless belt that is wound around (open belted) the corresponding first roller  332  and second roller  334 . The belts  336  may each rotate the corresponding first roller  332  and second roller  334  while rotating around the corresponding first roller  332  and second roller  334 . The width (the length in the Z direction) of each belt  336  substantially corresponds to the width (the length in the Z direction) of the first busbar  310  and the second busbar  320 . The width of each belt  336  may be slightly smaller than those of the first busbar  310  and the second busbar  320 . 
         [0056]    The elastic members  338  are each formed of an elastic material such as rubber or soft resin (nylon elastomeric resin, for example). The elastic members  338  are each provided between the corresponding first roller  332  and second roller  334  in the Y direction. The elastic members  338  are each provided in a space formed on the inner peripheral surface side of the corresponding belt  336 . The elastic members  338  each push the corresponding belt  336  towards the first busbar  310  and the second busbar  320 . In other words, the elastic members  338  are each disposed on the inner peripheral surface side of the corresponding belt  336  in an elastically deformed manner and pushes the corresponding belt  336  towards the outside in the X direction (the X1 direction and the X2 direction, see  FIG. 6 ). As will be described later, the outside in the X direction corresponds to directions that increase the contact force between the belts  336 , and the first busbar  310  and the second busbar  320 . The elastic members  338  may each take a form of a gasket or a cushion material that exerts the same elastic function as the elastic members  338 . Note that in the example illustrated in  FIGS. 6 and 7 , the elastic members  338  are separately provided in the upper and lower relay mechanisms  330 A and  330 B; however, similar to the shaft portions  332   a  and  334   a,  a single elastic member  338  that is shared by the upper and lower relay mechanisms  330 A and  330 B may be provided. 
         [0057]      FIG. 8  is a diagram illustrating an exemplary state in which the first busbar  310  is mounted in the housing  100 . Note that in  FIG. 8 , in order to facilitate the view of the interior, illustration of an upper surface member of the housing  100  is omitted. 
         [0058]    The first busbar  310  is provided in the housing  100  so as to extend in the Y direction. The first busbar  310  may be fixed or supported with any method. For example, as illustrated in  FIG. 8 , the first busbar  310  may be fixed to a substrate  30  and a wall member  102  with a screw or the like. In such a case, the first busbar  310  may be electrically connected to the power source  20  through a circuit on the substrate  30 . Note that the first busbar  310  may be directly connected to the power source  20  or may be connected to the power source  20  through another component such as a cable. 
         [0059]      FIG. 9  is a diagram illustrating an exemplary state in which the relay mechanism  330  is mounted in the housing  100 .  FIG. 10  is an enlarged view of portion X of  FIG. 9 . 
         [0060]    As illustrated in  FIG. 9 , the relay mechanism  330  may be mounted in the housing  100  with a pair of guide rails  120 . In the examples illustrated in  FIGS. 9 and 10 , the guide rails  120  are each provided above and below the relay mechanism  330 . The guide rails  120  extend in the Y direction so as to correspond to the moving range of the relay mechanism  330  in the Y direction (see  FIG. 14 ). The guide rails  120  may guide the movement of the relay mechanism  330  in the Y direction described later, which is caused upon movement of the tray  200  in the Y direction, in any manner. In the examples illustrated in  FIGS. 9 and 10 , the guide rails  120  include guide grooves  122  that extend in the Y direction. The shaft portions  332   a  and  334   a  of the relay mechanism  330  are passed through the guide grooves  122 . In such a case, the end portions (the enlarged diameter portions) of the shaft portions  332   a  and  334   a  that are larger than the width (the length in the X direction) of the guide grooves  122  may function to position the relay mechanism  330  in the up-down direction with respect to the guide rails  120 . The relay mechanism  330  may be moved (translated) in the Y direction by moving the shaft portions  332   a  and  334   a  along the guide grooves  122  in the Y direction. 
         [0061]    Note that the guide rails  120  may be fixed to the housing  100  in any manner. The guide rails  120  may be, for example, fitted into or screwed to the housing  100 . Furthermore, the guide rails  120  may be fixed to the housing  100  through the first busbar  310 . For example, the upper and lower guide rails  120  may be integrally formed with the upper and lower first busbars  311  and  312 , respectively. However, in such a case, in order to avoid the upper and lower first busbars  311  and  312  from becoming short-circuited to each other, the shaft portions  332   a  and  334   a  are provided to the upper and lower relay mechanisms  330 A and  330 B in a separate manner. 
         [0062]      FIGS. 11 and 12  are each a perspective view illustrating an exemplary state in which the second busbar  320  is mounted to the tray  200 .  FIG. 11  is a perspective view seen from the front side and  FIG. 12  is a perspective view seen from the rear side. 
         [0063]    The second busbar  320  is provided to the tray  200  so as to correspond to the first busbar  310  and extends in the drawing-out direction (the Y direction) of the tray  200 . The second busbar  320  is provided at a position that faces the first busbar  310  in the X direction (see  FIGS. 1 and 2 ). The second busbar  320  may be fixed or supported with any method. For example, as illustrated in  FIGS. 11 and 12 , the second busbar  320  may be fixed to the substrate  32  and a wall member  202  with a screw or the like. In such a case, the second busbar  320  may be electrically connected to the hot-swap parts (for example, the hard disk drives  10  and the fans  12 ) on the tray  200  through a circuit on the substrate  32 . Note that the second busbar  320  may be directly connected to the hot-swap parts on the tray  200  or may be connected to the hot-swap parts through another component such as a cable. 
         [0064]      FIGS. 13A and 13B  are each a diagram illustrating connection portions between the relay mechanism  330  and each of the first busbar  310  and the second busbar  320 .  FIG. 13A  is a top view and  FIG. 13B  is a front view. 
         [0065]    As illustrated in  FIG. 13B , the relay mechanism  330  is disposed so that the belts  336  are in contact with both the first busbar  310  and the second busbar  320  in the X direction. In the above, as illustrated in  FIG. 13A , the belts  336  are in surface contact with both the first busbar  310  and the second busbar  320 . In other words, the belts  336  are each in surface contact with both the first busbar  310  and the second busbar  320  at sections of each belt  336  between the center of the corresponding first roller  332  and the center of the corresponding second roller  334  in the Y direction. Accordingly, the contact areas between the relay mechanism  330  and each of the first busbar  310  and the second busbar  320  may be increased in an efficient manner such that the relay mechanism  330  may relay electric power from the power source  20  to the tray  200  side in a stable and efficient manner. Note that each of the elastic members  338  preferably exerts an elastic force that reliably allows the relay mechanism  330  to come in contact with each of the first busbar  310  and the second busbar  320 . 
         [0066]      FIGS. 14A and 14B  are each a top view illustrating the manner in which the relay mechanism  330  moves upon movement of the tray  200 .  FIG. 14A  illustrates a state in which the tray  200  is housed in the housing  100  and  FIG. 14B  illustrates a state in which the tray  200  is drawn out from the housing  100 . Note that in  FIGS. 14A and 14B , in order to facilitate the view of the interior, illustration of the upper surface member of the housing  100  is omitted. 
         [0067]    As illustrated in  FIGS. 14A and 14B , when the tray  200  is drawn out from the housed state, the relay mechanism  330  moves in the Y2 direction with respect to the tray  200  and moves in the Y1 direction with respect to the housing  100 . During the movement, the relay mechanism  330  maintains surface contact with the first busbar  310  and the second busbar  320 . In other words, the relay mechanism  330  maintains surface contact with the first busbar  310  and the second busbar  320  throughout the section between where the tray  200  is totally stored and where the tray  200  is fully drawn out (that is, throughout the whole stroke). Accordingly, the supply of electric power from the power source  20  to the hot-swap parts on the tray  200  is maintained while the drawing-out operation of the tray  200  (during the movement of the relay mechanism  330 ) is carried out. Note that during the storing operation as well, the relay mechanism  330  moves while maintaining surface contact with the first busbar  310  and the second busbar  320  in a similar manner to the drawing-out operation. 
         [0068]    During the movement of the relay mechanism  330 , the belts  336  of the relay mechanism  330  rotate around the first rollers  332  and the second rollers  334  with the friction between the belts  336  and each of the first busbar  310  and the second busbar  320 . In such a case, the belts  336  rotate around the first rollers  332  and the second rollers  334  while the friction generated between the belts  336 , and the first rollers  332  and the second rollers  334  rotates the first rollers  332  and the second rollers  334  (see  FIG. 6 ). In other words, while the belts  336  rotate around the first rollers  332  and the second rollers  334 , the belts  336  relatively move with respect to the first busbar  310  and the second busbar  320  without any sliding against the first busbar  310  and the second busbar  320 . Accordingly, wear of the belts  336 , the first busbar  310 , and the second busbar  320  due to the drawing-out and storing of the tray  200  may be reduced. Note that “without any sliding” does not imply that a slight sliding due to looseness (clearance) or tolerance is not tolerated. In other words, “without any sliding” implies that sliding that actually creates wear of the belts  336 , the first busbar  310 , and the second busbar  320  does not occur. 
         [0069]    As described above, according to the present embodiment, the belts  336  of the relay mechanism  330  maintains surface contact with the first busbar  310  and the second busbar  320  during the drawing-out and storing operation of the tray  200 . Accordingly, electric power from the power source  20  may be supplied to the hot-swap parts in a stable and efficient manner even during the drawing-out and storing operation of the tray  200 . Specifically, since the portions between the belts  336  and each of the first busbar  310  and the second busbar  320  are in surface contact with each other, compared with a case in which the portions are in line contact with each other, the possibility of separation between the belts  336  and each of the first busbar  310  and the second busbar  320  due to disturbance such as vibration is small. Accordingly, electric power may be supplied in a stable manner. Furthermore, since the portions between the belts  336  and each of the first busbar  310  and the second busbar  320  are in surface contact with each other, compared with a case in which the portions are in line contact with each other, the contact area is larger (accordingly, the contact resistance is smaller) and electric power may be supplied in an efficient manner. 
         [0070]    Furthermore, according to the present embodiment, during the drawing-out and storing operation of the tray  200 , the belts  336  rotate around the first rollers  332  and the second rollers  334  without sliding against the first busbar  310  and the second busbar  320 . Accordingly, wear of the belts  336 , the first busbar  310 , and the second busbar  320  due to the drawing-out and storing of the tray  200  may be reduced. 
       Second Embodiment 
       [0071]      FIG. 15  is a perspective view illustrating a device  2  according to a second embodiment.  FIG. 16  is a perspective view of the device  2  illustrated in  FIG. 15  in which the tray  200  is drawn out. 
         [0072]    The device  2  of the present embodiment is generally different in that the power supply system  300  of the device  1  according to the first embodiment described above is replaced with the power supply system  400 . In other words, the device  2  of the present embodiment is generally different in that the first busbar  310 , the second busbar  320 , and the relay mechanism  330  of the device  1  according to the first embodiment described above are replaced with a first busbar  410 , a second busbar  420 , and a relay mechanism  430 , respectively. Hereinafter, the configuration of the first busbar  410 , the second busbar  420 , and the relay mechanism  430  will be mainly described. Other components that may be similar to those described above in the first embodiment will be denoted with the same reference numerals and descriptions thereof will be omitted. 
         [0073]      FIG. 17  is an exploded perspective view illustrating the power supply system  400  according to the second embodiment.  FIGS. 18A and 18B  are each a diagram illustrating an exemplary state in which the first busbar  410  is mounted in the housing  100 .  FIG. 18A  is a general view and  FIG. 18B  is an enlarged view of portion XVIIIB.  FIGS. 19A and 20  are each a perspective view illustrating an exemplary state in which the second busbar  420  is mounted to the tray  200 .  FIG. 19A  is a perspective view seen from the front side and  FIG. 20  is a perspective view seen from the rear side.  FIG. 19A  is a general view and  FIG. 19B  is an enlarged view of portion XIXB. Note that a portion of the first busbar  410  and a portion of the second busbar  420  (a first busbar  411  and a second busbar  421  on the upper side) are not shown in  FIG. 17  in order to facilitate visual understanding. Furthermore, note that in  FIG. 18A , in order to facilitate the view of the interior, illustration of the upper surface member of the housing  100  is omitted. 
         [0074]    As illustrated in  FIG. 17 , the power supply system  400  includes the first busbar  410 , the second busbar  420 , and the relay mechanism  430 . 
         [0075]    In the second embodiment as well, similar to the first embodiment described above, the first busbar  410  includes the first busbar  411  on the upper side and a first busbar  412  on the lower side and the second busbar  420  includes the second busbar  421  on the upper side and a second busbar  422  on the lower side. Meanwhile, the relay mechanism  430  includes a relay mechanism  430 A on the upper side and a relay mechanism  430 B on the lower side in an integrated manner. However, similar to the first embodiment described above, the power supply system  400  may be provided with a mechanism that supplies the ground voltage and a mechanism that supplies the source voltage in a separate manner. Furthermore, the power supply system  400  may only include the mechanism that supplies the source voltage, and another component may be adopted as for the mechanism that supplies the ground voltage. 
         [0076]    The first busbar  410  is different from the first busbar  310  according to the first embodiment described above in that a plurality of fitting holes  411   a  and  412   a  that are aligned with respect to one another in the Y direction are provided. Other configurations of the first busbar  410  may be similar to those of the first busbar  310  according to the first embodiment described above. As illustrated in  FIGS. 18A and 18B , the plurality of fitting holes  411   a  are formed in the first busbar  411  on the upper side and the plurality of fitting holes  412   a  are formed in the first busbar  412  on the lower side. The spaces of the plurality of fitting holes  411   a  correspond to the spaces of a plurality of projections  432   b  (see  FIG. 21 ) of the relay mechanism  430  that are described later and to the spaces of a plurality of projections  434   b.  The spaces of the plurality of fitting holes  412   a  correspond to the spaces of the plurality of projections  432   b  of the relay mechanism  430  that are described later and to the spaces of the plurality of projections  434   b.  Furthermore, the fitting holes  411   a  and  412   a  are formed at positions corresponding to the positions of the projections  432   b  and  434   b  in the Z direction. 
         [0077]    The second busbar  420  is different from the second busbar  320  according to the first embodiment described above in that a plurality of fitting holes  421   a  and  422   a  that are aligned with respect to one another in the Y direction are provided. Other configurations of the second busbar  420  may be similar to those of the second busbar  320  according to the first embodiment described above. As illustrated in  FIGS. 19A and 19B , the plurality of fitting holes  421   a  are formed in the second busbar  421  on the upper side and the plurality of fitting holes  422   a  are formed in the second busbar  422  on the lower side. The spaces of the plurality of fitting holes  421   a  correspond to the spaces of the plurality of projections  432   b  (see  FIG. 21 ) of the relay mechanism  430  that are described later and to the spaces of the plurality of projections  434   b.  The spaces of the plurality of fitting holes  422   a  correspond to the spaces of the plurality of projections  432   b  of the relay mechanism  430  that are described later and to the spaces of the plurality of projections  434   b.  Furthermore, the fitting holes  421   a  and  422   a  are formed at positions corresponding to the positions of the projections  432   b  and  434   b  in the Z direction. 
         [0078]    The relay mechanism  430  is provided between the first busbar  410  and the second busbar  420  and relays the electrical connection between the first busbar  410  and the second busbar  420 . Note that similar to the relay mechanism  330  according to the first embodiment described above, as illustrated in  FIG. 17 , the relay mechanism  430  may include the relay mechanism  430 A on the upper side and the relay mechanism  430 B on the lower side. In a similar manner to the relay mechanism  330  according to the first embodiment described above, the relay mechanism  430  may be mounted in the housing  100  with the guide rails  120 . 
         [0079]      FIG. 21  illustrates three orthographic views of the relay mechanism  430 .  FIG. 22  is a perspective view of components of the relay mechanism  430  that have been picked out. Note that among first rollers  432  and second rollers  434 , only the first rollers  432  are illustrated in  FIG. 22  as a representative example. Note that in the present embodiment, the relay mechanism  430  includes the relay mechanism  430 A on the upper side and the relay mechanism  430 B on the lower side as described above and the components of the relay mechanism  430 A and those of the relay mechanism  430 B are basically the same and the same reference numerals are attached thereto. 
         [0080]    The relay mechanism  430 A includes the first roller  432 , the second roller  434 , and a belt  436 . Furthermore, the relay mechanism  430 A preferably includes an elastic member  438  as illustrated in  FIG. 21 . The relay mechanism  430 B may have a similar configuration. 
         [0081]    As illustrated in  FIG. 22 , the first rollers  432  are different from the first rollers  332  according to the first embodiment described above in that the plurality of projections  432   b  are provided on the outer peripheral surface of each of the first rollers  432  in the circumferential direction. Other configurations of the first rollers  432  may be similar to those of the first rollers  332  according to the first embodiment described above. The plurality of projections  432   b  may be formed on the whole circumference of each of the first rollers  432  in the circumferential direction at equal spaces. As described later, the plurality of projections  432   b  are formed with heights that allow the plurality of projections  432   b  to fit into the fitting holes  411   a  and  412   a  of the first busbar  410  and the fitting holes  421   a  and  422   a  of the second busbar  420 . The plurality of projections  432   b  may be formed in the middle of each of the first rollers  432  in the axial direction (the Z direction). Note that a shaft portion  432   a  and a bearing  433  that rotatably support the first rollers  432  may have configurations similar to those of the shaft portion  332   a  and the bearing  333 , respectively, according to the first embodiment described above. 
         [0082]    As illustrated in  FIG. 21 , the second rollers  434  are different from the second rollers  334  according to the first embodiment described above in that the plurality of projections  434   b  are provided on the outer peripheral surface of each of the second rollers  434  in the circumferential direction. Other configurations of the second rollers  434  may be similar to those of the second rollers  334  according to the first embodiment described above. The plurality of projections  434   b  may be formed on the whole circumference of each of the second rollers  434  in the circumferential direction at equal spaces. As described later, the plurality of projections  434   b  are formed with heights that allow the plurality of projections  434   b  to fit into the fitting holes  411   a  and  412   a  of the first busbar  410  and the fitting holes  421   a  and  422   a  of the second busbar  420 . The plurality of projections  434   b  may be formed in the middle of each of the second rollers  434  in the axial direction (the Z direction). Note that a shaft portion  434   a  and a bearing  435  that rotatably support the second rollers  434  may have configurations similar to those of the shaft portion  334   a  and the bearing  335 , respectively, according to the first embodiment described above. 
         [0083]    As illustrated in  FIG. 22 , the belts  436  are different from the belts  336  according to the first embodiment described above in that a plurality of through holes  436   c  are provided along the circumferential direction of each of the belts  436 . Other configurations of the belts  436  may be similar to those of the belts  336  according to the first embodiment described above. The plurality of through holes  436   c  may be formed on the whole circumference of each of the belts  436  in the circumferential direction at equal spaces. The spaces of the plurality of through holes  436   c  correspond to the spaces of the plurality of projections  432   b  (the spaces in the circumferential direction) and to the spaces of the plurality of projections  434   b  (the spaces in the circumferential direction). The through holes  436   c  are formed at positions that correspond to the projections  432   b  of the first rollers  432  and the projections  434   b  of the second rollers  434  in the Z direction. The through holes  436   c  include openings that correspond to the projections  432   b  of the first rollers  432  and the projections  434   b  of the second rollers  434 . In other words, the through holes  436   c  are formed so as to allow the projections  432   b  of the first rollers  432  and the projections  434   b  of the second rollers  434  to be inserted therein (to be passed therethrough). Note that in the second embodiment, the belts  436  are each provided with a double layer structure (a double structure) including a first belt  436   a  on the inner diameter side and a second belt  436   b  on the outer diameter side; however, each of the belts  436  may have a single layer structure similar to the structure of the belt  336  according to the first embodiment described above. On the other hand, each of the belts  336  according to the first embodiment described above may have a double layer structure similar to the structure of the belt  436 . The first belts  436   a  may be formed of, for example, a conductive material such as copper or conductive rubber, and the second belts  436   b  may be formed of a copper thin plate. 
         [0084]    Note that the belts  436  according to the second embodiment may, as described later, rotate around the first rollers  432  and the second rollers  434  while being rotated by the rotation of the first rollers  432  and the second rollers  434 . 
         [0085]    The elastic members  438  are components provided in the preferred embodiments in an optional manner and may be elastic members that are similar to the elastic members  338  according to the first embodiment described above. Note that in the second embodiment, the elastic members  438  each include supported portions  438   a  that are supported by the upper surface of the belt  436 ; however, the elastic members  438  may have a structure similar to the structure of the elastic members  338  according to the first embodiment described above. On the other hand, the elastic members  338  according to the first embodiment described above may each have supported portions similar to those of the elastic members  438 . 
         [0086]      FIGS. 23A and 23B  are each a diagram illustrating connection portions between the relay mechanism  430  and each of the first busbar  410  and the second busbar  420 .  FIG. 23A  is a top view and  FIG. 23B  is a front view. Note that in  FIGS. 23A and 23B , in order to facilitate the view of the interior, illustration of a protective cover  500  and a protective flange  204  of the tray  200  that are described later is omitted. 
         [0087]    As illustrated in  FIG. 23B , the relay mechanism  430  is disposed so that the belts  436  are in contact with both the first busbar  410  and the second busbar  420  in the X direction. In the above, as illustrated in  FIG. 23A , the belts  436  are in surface contact with both the first busbar  410  and the second busbar  420 . In other words, the belts  436  are in surface contact with both the first busbar  410  and the second busbar  420  at sections between the center of the first roller  432  and the center of the second roller  434  in the Y direction. Accordingly, the contact areas between the relay mechanism  430  and each of the first busbar  410  and the second busbar  420  may be increased in an efficient manner such that the relay mechanism  430  may relay electric power from the power source  20  to the tray  200  side in a stable and efficient manner. Note that each of the elastic members  438  preferably exerts an elastic force that reliably allows the relay mechanism  430  to come in contact with each of the first busbar  410  and the second busbar  420 . 
         [0088]      FIGS. 24A and 24B  are each a top view illustrating the manner in which the relay mechanism  430  moves upon movement of the tray  200 .  FIG. 24A  illustrates a state in which the tray  200  is housed in the housing  100  and  FIG. 24B  illustrates a state in which the tray  200  is drawn out from the housing  100 . Note that in  FIGS. 24A and 24B , in order to facilitate the view of the interior, illustration of the upper surface member of the housing  100  is omitted. 
         [0089]    As illustrated in  FIGS. 24A and 24B , when the tray  200  is drawn out from the housed state, the relay mechanism  430  moves in the Y2 direction with respect to the tray  200  and moves in the Y1 direction with respect to the housing  100 . During the movement, the relay mechanism  430  maintains surface contact with the first busbar  410  and the second busbar  420 . Note that during the storing operation as well, similar to the drawing-out operation, the relay mechanism  430  moves while maintaining surface contact with the first busbar  410  and the second busbar  420 . During the movement of the relay mechanism  430 , the belts  436  of the relay mechanism  430  rotate around the first rollers  432  and the second rollers  434  with the rotation of the first rollers  432  and the second rollers  434  (see  FIG. 21 ). In other words, the belts  436  do not slide against the first busbar  410  and the second busbar  420  in the Y direction but rotates around the first rollers  432  and the second rollers  434  while relatively moving with respect to the first busbar  410  and the second busbar  420 . Accordingly, the second embodiment may also obtain an effect similar to that obtained with the first embodiment described above. 
         [0090]    In particular, in the second embodiment, the first rollers  432  and the second rollers  434  rotate while the projections  432   b  and  434   b  fit into the fitting holes  411   a  and  412   a  of the first busbar  410  and the fitting holes  421   a  and  422   a  of the second busbar  420 . In other words, when the tray  200  moves in the Y1 direction, the second busbar  420  pushes the projections  432   b  and  434   b  that fit into the fitting holes  411   a  and  412   a  in the Y1 direction (the tangential direction). Furthermore, the first busbar  410  pushes the projections  432   b  and  434   b  that fit into the fitting holes  411   a  and  412   a  in the Y2 direction (the tangential direction). With the above, the first rollers  432  and the second rollers  434  are rotated in the counterclockwise direction in plan view. Consequently, the belts  436  are rotated in the counterclockwise direction in plan view with the projections  432   b  and  434   b  that penetrate the through holes  436   c.  In a similar manner, when the tray  200  moves in the Y2 direction, the second busbar  420  pushes the projections  432   b  and  434   b  that fit into the fitting holes  411   a  and  412   a  in the Y2 direction (the tangential direction). Furthermore, the first busbar  410  pushes the projections  432   b  and  434   b  that fit into the fitting holes  411   a  and  412   a  in the Y1 direction (the tangential direction). With the above, the first rollers  432  and the second rollers  434  are rotated in the clockwise direction in plan view. Consequently, the belts  436  are rotated in the clockwise direction in plan view with the projections  432   b  and  434   b  that penetrate the through holes  436   c.  As described above, in the second embodiment, the projections  432   b  and  434   b,  the through holes  436   c,  the fitting holes  411   a  and  412   a,  and the fitting holes  421   a  and  422   a  are provided in the above manner; accordingly, wear of the belts  436  and other components may be reduced in a further reliable manner. In other words, the possibility of the belts  436  sliding on the first busbar  410  and the second busbar  420  is reduced and the wear of the first busbar  410  and the second busbar  420  upon the drawing-out and storing operation of the tray  200  may be reduced in a further reliable manner. 
         [0091]    Note that in the second embodiment, the projections  432   b  and  434   b  that are fitted into the fitting holes  411   a  and  412   a  of the first busbar  410  and the fitting holes  421   a  and  422   a  of the second busbar  420  are formed on each of the first rollers  432  and each of the second rollers  434 . However, the above may be opposite. That is, fitting holes may be formed in the outer peripheral surfaces of the first rollers  432  and the outer peripheral surfaces of the second rollers  434 , and projections may be formed on the first busbar  410  and the second busbar  420 . In such a case, the projections of the first busbar  410  and the second busbar  420  may be fitted into the fitting holes of the first rollers  432  and the second rollers  434  through the through holes  436   c  of the belts  436 . 
         [0092]      FIG. 25  is an explanatory drawing of the protective cover  500 , the protective flange  204  of the tray  200 , and other components and is an enlarged cut-away view of a portion of  FIG. 16 . 
         [0093]    As illustrated in  FIGS. 16 and 25 , the device  2  preferably includes the protective cover  500 . The protective cover  500  is provided to the tray  200  so as to cover the second busbar  420 . In the example illustrated in  FIG. 25 , the protective cover  500  covers the second busbar  420  from the X2 side of the tray  200  in the X direction. Accordingly, when the tray  200  is drawn out from the housing  100 , the second busbar  420 , which is drawn out together with the tray  200 , may be avoided from being exposed to the outside. 
         [0094]    Note that as illustrated in  FIG. 25 , the protective cover  500  extends in the Y direction so that the whole exposed portion of the second busbar  420  is covered (hid) when the tray  200  is fully drawn out. In order to avoid the protective cover  500  from hindering the function of the relay mechanism  430  described above, the protective cover  500  may be provided on the X2 side with respect to the first busbar  410 . The protective cover  500  may be fixed to the tray  200  with any method such as a screwing or the like. Note that in the example illustrated in  FIG. 25 , the upper side (the Z1 side) of the second busbar  420  is protected (covered) by a protective flange  206  on the upper side of the tray  200 . In a similar manner, the lower side (the Z2 side) of the second busbar  420  may be protected by a protective flange (not shown) on the lower side of the tray  200 . Furthermore, in the example illustrated in  FIG. 25 , the front side (the Y1 side) of the second busbar  420  is protected (covered) by the protective flange  204  on the front side of the tray  200 . However, the protective cover  500  may be formed so as to carry out some or all of the functions of the protective flanges  204  and  206 . 
         [0095]    Note that the protective cover  500  may be provided to the device  1  according to the first embodiment described above in a similar manner. 
         [0096]    Each of the embodiments has been described above in detail; however, the present disclosure is not limited to a specific embodiment and various modifications and changes may be made within the scope of the claims. Furthermore, all or some of the components of the embodiments described above may be combined with one another. 
         [0097]    For example in the second embodiment described above, the projections  432   b  and  434   b  that are fitted into the fitting holes  411   a  and  412   a  of the first busbar  410  and the fitting holes  421   a  and  422   a  of the second busbar  420  are formed on each of the first rollers  432  and each of the second rollers  434 . However, similar projections that fit into the fitting holes  411   a  and  412   a  and the fitting holes  421   a  and  422   a  may be formed in the outer peripheral surfaces of the belts  436 . Alternatively, the fitting holes may be formed in the outer peripheral surfaces of the belts  436  and projections may be formed on the first busbar  410  and the second busbar  420 . In either of the cases, the configurations of the first rollers  432  and the second rollers  434  may be similar to those of the first rollers  332  and the second rollers  334  according to the first embodiment described above. In such a case, similar to the first embodiment described above, the belts  436  rotate around the first rollers  432  and the second rollers  434  while the friction generated between the belts  436 , and the first rollers  432  and the second rollers  434  rotates the first rollers  432  and the second rollers  434 . Such friction between the belts  436 , and the first rollers  432  and the second rollers  434  may be generated by engagement of the projections formed in or the fitting holes formed on the inner peripheral surfaces of the belts  436  and the fitting holes formed in or projections formed on the outer peripheral surfaces of the first rollers  432  and the second rollers  434 . 
         [0098]    Furthermore, in the second embodiment described above, the fitting holes  411   a  and  412   a  of the first busbar  410  and the fitting holes  421   a  and  422   a  of the second busbar  420  are holes that penetrate the first busbar  410  and the second busbar  420 . However, the fitting holes  411   a  and  412   a  and the fitting holes  421   a  and  422   a  may be holes (concavities) with a bottom. 
         [0099]    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 embodiments of the present invention have 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.