Abstract:
Provided is an electronic equipment cabinet capable of detecting a storage state of a circuit board unit by using a smaller number of switches than circuit board units. The electronic equipment cabinet, which stores a plurality of circuit board units inserted and extracted in the same direction, includes a plurality of slots for storing the circuit board units, a plurality of cover members for covering the slots, and a switch for detecting closing of all the slots. The cover members, which are provided by a plurality of types having an installation order restricting mechanism for preventing closing of the slots, except for when the cover members are installed according to a preset installation order, includes a driving member located in a final-installation cover member that is installed last and configured to drive the switch.

Description:
TECHNICAL FIELD 
     The present invention relates to an electronic equipment cabinet for storing a circuit board unit. More particularly, the invention relates to an electronic equipment cabinet that needs a switch for detecting a storage state or a load state of a plurality of circuit board units. 
     BACKGROUND ART 
     As an electronic equipment cabinet for efficiently storing a circuit board unit, there is known a cabinet that includes slots to freely insert and extract circuit board units. 
     Arranging cover members in the circuit board units to cover the slot provides an advantage of simultaneously storing the circuit boards and closing the slots. Such an electronic equipment cabinet is generally employed for a personal computer and, in many cases, employed for a video device and a measuring device. 
     When the electronic equipment cabinet having the slots is employed for the video device, a gap between an outer wall of the cabinet and the cover member of the circuit board unit creates a possibility that EMI (Electro Magnetic Interference), such as electromagnetic wave leakage to the outside of the cabinet, may occur. JP2000-332479A (Patent Literature 1) discloses a method for improving the effects of reducing EMI by forming a gasket in the gap between the cabinet and the cover member to close the gap, thereby improving shielding performance. 
     In recent years, for security purposes, there has been known an electronic equipment cabinet that includes a switch to detect storage of a circuit board unit in a slot of the cabinet. JP2004-172455A (Patent Literature 2) discloses an electronic equipment cabinet that includes a switch and can detect a storage state or a load state based on the contact state between a part of the cover member and the switch. 
     In the electronic equipment cabinet for storing the plurality of circuit board units, the inclusion of a switch corresponding to each circuit board unit increases the number of components, thus increasing costs. The switch itself becomes an EMI antenna, and hence when there are many switches, the influence of EMI easily appears. 
     In particular, the recent enlargement of the video device requires displaying of a video with higher accuracy and smoother representation of motion. This necessitates video data of a wider band, and a clock of the video device has become faster. The faster clock generates greater noise, and the influence of EMI has become more conspicuous in the video device. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP2000-332479A 
         Patent Literature 2: JP2004-172455A 
       
    
     SUMMARY OF INVENTION 
     An example of an object of the present invention is therefore to provide an electronic equipment cabinet capable of detecting the storage state of a circuit board unit by using a smaller number of switches than circuit board units. 
     To achieve the object, according to an aspect of the present invention, an electronic equipment cabinet, which stores a plurality of circuit board units inserted and extracted in the same direction, includes a plurality of slots for storing the circuit board units, a plurality of cover members for covering the slots, and a switch for detecting closing of all the slots. The cover members, which are provided by a plurality of types having an installation order restricting mechanism for preventing closing of the slots, except for when the cover members are installed according to a preset installation order, includes a driving member located in a final-installation cover member that is installed last and configured to drive the switch. 
     According to the present invention, the storage state of the circuit board unit can be detected by using a smaller number of switches than circuit board units. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing an electronic equipment cabinet according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view when circuit board units are stored in the electronic equipment cabinet. 
         FIG. 3  is a side view showing a circuit board unit. 
         FIG. 4  is a sectional view showing the electronic equipment cabinet. 
         FIG. 5  is a block diagram showing a circuit configuration example of a video device. 
         FIG. 6  is a sectional view showing an electronic equipment cabinet according to a second exemplary embodiment. 
         FIG. 7  is a sectional view showing an electronic equipment cabinet according to a third exemplary embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, exemplary embodiments of the present invention are described.  FIG. 1  is a perspective view showing an electronic equipment cabinet according to a first exemplary embodiment of the present invention.  FIG. 2  is a perspective view when circuit board units are stored in the electronic equipment cabinet. 
     As shown in  FIG. 1 , electronic equipment cabinet  1  includes slots  6   a ,  6   b ,  6   c , and  6   d  formed in sequence to store circuit board units  2   a ,  2   b ,  2   c , and  2   d  inserted and extracted in the same direction. As shown in  FIG. 2 , circuit board units  2   a ,  2   b ,  2   c , and  2   d  are inserted into slots  6   a ,  6   b ,  6   c , and  6   d  to be stored in electronic equipment cabinet  1 . 
       FIG. 3  is a side view showing circuit board unit  2   d  stored in slot  6   d  of electronic equipment cabinet  1 .  FIG. 4  is a sectional view (A-A section shown in  FIG. 2 ) when circuit board units  2   a ,  2   b ,  2   c , and  2   d  are stored in slots  6   a ,  6   b ,  6   c , and  6   d.    
     As shown in  FIG. 3 , circuit board unit  2   d  includes cover member  3   d  to cover slot  6   d , and circuit board  5   d  having electronic component  13   d . Cover member  3   d  has screw  7   d  formed to fix circuit board unit  2   d  to an outer wall of electronic equipment cabinet  1 . 
     At a lower end of cover member  3   d , base  4  is formed to be a step in a direction for inserting circuit board unit  2   d  into slot  6   d . At an upper end of cover member  3   d , gasket  8   d  is similarly formed in the inserting direction into slot  6   d.    
     When circuit board unit  2   d  is stored in slot  6   d , the upper end of cover member  3   d  overlaps a surface of the lower end of adjacent cover member  3   c  ( FIG. 4 ). Thus, the upper end (hereinafter, referred to as gasket) of cover member  3   d  is bent so that gasket  8   d  of cover member  3   d  can come into contact with base  4   c  of cover member  3   c.    
     Further, cover member  3   d  includes driving member  9  formed to drive switch  10  ( FIG. 4 ) for detecting closing of slot  6   d  by cover member  3   d . In this exemplary embodiment, a projection is formed as driving member  9 . 
     Cover member  3   d  is made of a conductive material having a plate thickness of about 1 millimeter, and a depth of base  4  formed at the lower end of cover member  3   d  is designed to be 5.5 millimeters. Gasket  8   d  is also made of a conductive material having a thickness of about 1 millimeter. Using the conductive materials for cover member  3   d  and gasket  8  improves EMI shielding performance. 
     Circuit board units  2   a ,  2   b , and  2   c  are similar in configuration to circuit board unit  2   d . However, as described below, in this exemplary embodiment, it is only cover member  3   d  that closes lowermost slot  6   d  that comes into contact with switch  10 . This eliminates the necessity of forming any driving member  9  in cover members  3   a ,  3   b , and  3   c.    
     As shown in  FIG. 4 , connectors  11   a ,  11   b ,  11   c , and  11   d  electrically connectable to circuit boards  5   a ,  5   b ,  5   c , and  5   d  are arranged in electronic equipment cabinet  1 . Connectors  11   a ,  11   b ,  11   c , and  11   d  are fixed to mother board  12  in electronic equipment cabinet  1 , and are electrically interconnected via mother board  12 . 
     Thus, inserting circuit boards  5   a ,  5   b ,  5   c , and  5   d  into connectors  11   a ,  11   b ,  11   c , and  11   d  enables exchanging of electric signals among circuit boards  5   a ,  5   b ,  5   c , and  5   d . Connectors  11   a ,  11   b ,  11   c , and  11   d  can be directly fixed to electronic equipment cabinet  1  as long as they are electrically interconnected. 
     Gasket  8   a  is disposed in a contact position between a top surface of electronic equipment cabinet  1  and cover member  3   a , and hence there is no gap between electronic equipment cabinet  1  and cover member  3   a . Gaskets  8   b ,  8   c , and  8   d  are also arranged in contact positions between cover members  3   a  and  3   b ,  3   b  and  3   c , and  3   c  and  3   d , and bases  4   a ,  4   b ,  4   c , and  4   d  are formed at lower ends of cover members  3   a ,  3   b ,  3   c , and  3   d  to improve sealing. As a result, there is no gap between adjacent cover members  3   a  and  3   b ,  3   b  and  3   c , and  3   c  and  3   d , enabling reduction of the influence of EMI. 
     Further, in electronic equipment cabinet  1 , switch  10  is disposed only in lowermost slot  6   d . Switch  10  comes into contact with driving member  9  to detect closing of slot  6   d  by cover member  3   d . In this exemplary embodiment, the switch detects the closing by contact. However, the present invention is not limited to the contact-type switch. For example, an optical detection switching can be used. 
     Next, a method for detecting storage states of circuit board units  2   a ,  2   b ,  2   c , and  2   d  according to the present invention is described. 
     In circuit board unit  2   a  stored in uppermost slot  6   a , gasket  8   a  formed at the upper end of first cover member  3   a  abuts on the top surface of electronic equipment cabinet  1 . In circuit board unit  2   b  stored in slot  6   b  second from the top, gasket  8   b  formed at the upper end of second cover member  3   b  abuts on base  4   a  formed at the lower end of first cover member  3   a.    
     Thus, in a state where circuit board unit  2   b  stored after unit  2   a  is fixed to electronic equipment cabinet  1 , a back side of cover member  3   b  overlaps a front side of cover member  3   a , and hence circuit board unit  2   a  stored first is also fixed to electronic equipment cabinet  1 . To pull out circuit board unit  2   a  from electronic equipment cabinet  1 , circuit board unit  2   b  must be pulled out. 
     Because of base  4   a  formed at the end of cover member  3   a , when circuit board unit  2   a  is stored after circuit board unit  2   b  has been stored in electronic equipment cabinet  1 , a front side of the gasket interferes with a back side of base  4   a . This inhibits storage of circuit board unit  2   a  after circuit board unit  2   b  has been stored, necessitating first installation of cover member  3   a . In other words, base  4   a  and the gasket constitute an installation order restricting mechanism for preventing closing of slot  6   a  except for when the cover members are installed according to a preset installation order. 
     A relationship between circuit board unit  2   c  stored in slot  6   c  third from the top and circuit board unit  2   b  is similar to that between circuit board unit  2   b  and circuit board unit  2   a . Specifically, gasket  8   c  formed at the upper end of cover member  3   c  abuts on base  4   b  formed at the lower end of cover member  3   b , and circuit board unit  2   b  is fixed by circuit board unit  2   c  stored after unit  2   b.    
     Similarly, circuit board unit  2   c  is fixed by circuit board unit  2   d  stored in slot  6   d  fourth from the top, namely, lowermost slot  6   d  in this exemplary embodiment. This inhibits pulling-out of previously stored circuit board units  2   a ,  2   b , and  2   c  before circuit board unit  2   d  is pulled out. It can therefore be understood that when storage of lastly stored circuit board unit  2   d  in slot  6  is detected, circuit board units  2   a ,  2   b , and  2   c  will also have been stored. 
     In other words, when cover member  3   d  is removed from electronic equipment cabinet  1 , only cover member  3   d  moves away from electronic equipment cabinet  1  while other cover members  3   a ,  3   b , and  3   c  are not separated from electronic equipment cabinet  1 . When one of cover members  3   a ,  3   b , and  3   c  corresponding to slots  6   a ,  6   b , and  6   c  is removed from electronic equipment cabinet  1 , cover member  3   d  corresponding to slot  6   d  is always separated. 
     To achieve such a relationship, cover members  3   a ,  3   b ,  3   c , and  3   d  overlap one another at the ends in a direction where slots  6   a ,  6   b ,  6   c , and  6   d  are formed. This requires only one switch  10  to detect an installed state of cover member  3   d  that becomes a final-installation cover member. 
     Thus, in this exemplary embodiment, switch  10  is disposed in lowermost slot  6   d . The storage of circuit board unit  2   d  causes contact between driving member  9  and switch  10 , thereby enabling detection of a storage state of circuit board unit  2   d  and storage states of other circuit board units  2   a ,  2   b , and  2   c.    
     The cover members are classified into a plurality of types. Specifically, they are first cover member  3   a  installed first in the cabinet, second cover members  3   b  and  3   c  installed after the installation of first cover member  3   a , and cover member  3   d  that becomes a final-installation cover member. 
       FIG. 5  is a block diagram showing a circuit configuration example (DLP: Digital Light Processing) of a video device. Circuit components of the video device are not directly related to the present invention, and thus a detailed configuration is omitted. 
     As shown in  FIG. 5 , a video device body includes, in addition to circuit boards  5   a ,  5   b ,  5   c , and  5   d , mother board  12 , and switch  10  stored in electronic equipment cabinet  1 , power units  29   a  and  29   b , power control circuit board  14 , igniter  18 , lamp unit  19 , opto-tube  20 , prism  21 , DMD (Digital Micromirror Device) driving circuit  22 , and lens  23 . In this exemplary embodiment, circuit boards  5   a ,  5   b ,  5   c , and  5   d  are respectively body control circuit board  15 , video signal processing circuit board  16 , first video signal input circuit board  17   a , and second video signal input circuit board  17   b.    
     Body control circuit board  15  includes voltage detection circuit  25 , temperature detection circuit  26 , cooling fan control circuit  27 , and key-controlling control circuit  28 . Body control circuit board  15  has a function of detecting a contact state between driving member  9  and switch  10 . Video signal input circuit board  17   a  and  17   b  include input terminals for receiving video signals, and the input terminals are exposed to the outside of cover members  3   c  and  3   d . Video signal processing circuit board  16  includes a processing circuit that processes a video signal. 
     When power unit  29   a  is turned on, power is supplied through power control circuit board  14  and mother board  12  to DMD driving circuit  22 , body control circuit board  15 , video signal processing circuit board  16 , and video signal input circuit boards  17   a  and  17   b  to be driven. After a video signal has been transmitted from the input terminal to video signal input circuit board  17   a  or  17   b , video signal processing circuit board  16  processes the video signal to transmit it through mother board  12  to DMD driving circuit  22 . 
     When power unit  29   b  is turned on, igniter  18  applies ignition voltage to lamp unit  19  to light it. Light from the lamp is transmitted through opto-tube  20  to enter prism  21 . The light, which has been separated into R, G, and B colors by prism  21 , is reflected by a DMD controlled by DMD driving circuit  22 , and transmitted through lens  23  to be projected on a screen. 
     Further, when switch  10  and driving member  9  ( FIG. 4 ) are set in a noncontact state, body control circuit board  15  immediately responds to stop security processing of the video signal. A signal is also transmitted from body control circuit board  15  to video signal processing circuit board  16  to stop the video processing. 
     The use of abovementioned electronic equipment cabinet  1  and cover members  3   a ,  3   b ,  3   c , and  3   d  enables reduction of the number of switchers  10  to detect storage states of circuit board units  2   a ,  2   b ,  2   c , and  2   d . As a result, the number of components and the influence of EMI can be reduced. 
     In electronic equipment cabinet  1  shown in  FIGS. 2 to 4 , switch  10  is disposed in lowermost slot  6   d . However, the location of switch  10  is not limited to lowermost slot  6   d . For example, as shown in  FIG. 6 , bases  4   a ,  4   b ,  4   c , and  4   d  can be located at the upper ends of cover members  3   a ,  3   b ,  3   c , and  3   d , while gaskets  8   a ,  8   b ,  8   c , and  8   d  can be located at the lower ends. 
     This arrangement inhibits pulling-out of circuit board units  2   b ,  2   c , and  2   d  before circuit board unit  2   a  is pulled out from gasket  6   a . In this case, switch  10  is located to detect a storage state of circuit board unit  2   a  in slot  6   a.    
     Furthermore, the present invention can be applied to a case where circuit board unit  2   c  stored in slot  6   c  between the uppermost layer and the lowermost layer fixes circuit board units  2   a ,  2   b , and  2   d . Specifically, as shown in  FIG. 7 , switch  10  is located to detect a storage state of circuit board unit  2   c.    
     The present invention has been described by referring to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments. Various changes understandable to those skilled in the art can be made to the configuration and the specifics of the present invention within its technical teachings. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1  electronic equipment cabinet 
           2   a ,  2   b ,  2   c ,  2   d  circuit board unit 
           3   a ,  3   b ,  3   c ,  3   d  cover member 
           4   a ,  4   b ,  4   c ,  4   d  base 
           6   a ,  6   b ,  6   c ,  6   d  slot 
           8   a ,  8   b ,  8   c ,  8   d  gasket 
           9  driving member 
           10  switch