Patent Publication Number: US-2007123160-A1

Title: Communication cabinet and a method for dust removal of communications cabinet filters

Description:
RELATED APPLICATIONS  
      This application is a Continuation of and claims the priority benefit of U.S. Utility Application 10/981,968 filed 04 Nov. 2004, COMMUNICATION CABINET AND A METHOD FOR DUST REMOVAL OF COMMUNICATIONS CABINET FILTERS, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to communication cabinets and to methods for dust removal of communication cabinet filters.  
     BACKGROUND OF THE INVENTION  
      Modern network may include a large amount of communication cabinets that are spread over large areas. In many cases the communication cabinets are located several miles from each other. The large amount of communication cabinets and the distances between these cabinets increases the cost of network maintenance.  
      It is known that heat buildup shortens the life of communication equipment. Dust particles also can cause various malfunctions, especially when the communication cabinet is located in a humid environment. Dust can stick to communication equipment forming a layer that increases the heat buildup.  
      Various cooling techniques are known in the art. A first technique utilizes perforated communication cabin walls or doors as well as internally installed fans. This technique allows dust to enter the communication cabinet thus subjecting communication equipment within the communication cabinet to dust related failures.  
      In order to prevent dust and particles from entering the communication cabinets some communication cabinets are equipped with filters. Air passes though the filters, cools the interior of the communication cabinet and is forced out of the communication cabinet.  
      Gradually, these filters get filled with dust and over time allow diminishing amounts of air to enter the communication cabinet. As a result the communication equipment within the communication heats and malfunctions.  
      There is a need to provide a communication cabinet and a method for dust removal of communication cabinet filters.  
     SUMMARY OF THE PRESENT INVENTION  
      A communication cabinet, that includes: (i) at least one fan, adapted to rotate at a first direction during a first period and to rotate at a second opposing direction during a second period; (ii) a controller, adapted to control the at least one fan; and (iii) at least one filter positioned to substantially prevent dust from entering the communication cabinet during the first period and to allow air to exit the communication cabinet such as to remove dust from the filter during the second period.  
      A method for dust removal from one or more filters, the method includes: (i) providing a communication cabinet that include the one or more filters, whereas the one or more filters are positioned such as to substantially prevent dust from entering the communication cabinet; (ii) rotating at least one fan at a first direction during a first period such as to cool at least one communication circuit installed within the communication cabinet; and (ii) rotating the at least one fan at a second opposing direction during a second period such as to remove dust from the at east one filter.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:  
       FIG. 1  illustrates a portion of a communication cabinet according to an embodiment of the invention;  
       FIG. 2  illustrates a communication cabinet according to an embodiment of the invention;  
       FIG. 3  is a schematic illustration of airflows within the communication cabinet during a cooling period, according to an embodiment of the invention;  
       FIG. 4  is a schematic illustration of airflows within the communication cabinet during a dust removal period, according to an embodiment of the invention;  
       FIGS. 5-6  are flow charts illustrating methods for dust removal, according to embodiments of the invention; and  
       FIG. 7  is a schematic diagram of a controller, according to an embodiment of the invention.  
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  illustrates a portion  12  of communication cabinet  10  according to an embodiment of the invention.  FIG. 1  illustrates the inner infrastructure of communication cabinet  10 , without any doors, walls or any communication equipment.  
       FIG. 2  illustrates portion  12  as well as multiple pivotally mounted doors and walls of the communication cabinet  10 .  
      The inventors used a BroadAccess™ communication cabinet of Teledata networks of Herzliya, Israel. The BroadAccess™ includes a large variety of communication cabinets of different sizes that include one or more communication cages, and can support between sixty-four subscriber lines and one thousand and nine hundred subscriber lines. The communication cabinets can be installed outdoor or indoor, and can be mounted in various manners including wall mounting, pad mounting and floor level mounting. It is noted that the invention can be applied in other communication cabinets of the BroadAccess™ family, as well as in other communication cabinets.  
      The inner space of communication cabinet  10  is divided to multiple sections (denoted  40 - 48  in  FIGS. 3 and 4 ) in a manner that allows air and cables to pass through these sections, but this is not necessarily so. It is noted that at least one communication cage can be installed within each of these sections.  
      It is noted that communication cabinet  10  can include one or more fans that are positioned in various locations. For convenience of explanation it is assumed that multiple fans  16  are located in an upper inner wall  14  of the communication cabinet  10 .  
      The amount of fans  16  and filters as well as their position can vary within the scope of the invention. For example, according to an embodiment of the invention fans are located in fan trays that are located under each communication cage. According to an embodiment of the invention these fans participate in the dust removal but according to another embodiment they do not participate. These fans can rotate at the same direction, regardless of the rotation of fans  16 , they can be shut down or slowed during the dust removal period or even can rotate at a first direction during cooling periods and rotate to an opposite direction during a dust removal period.  
      Portion  12  has a rectangular shape and includes an inner upper wall  14  in which six fans  16  are installed in a “T” formation. An upper section  48  is defined between inner upper wall  14  and the top wall (or cover)  18  of the communication cabinet  10 . Conveniently, upper section  48  is designed such as to allow air sucked by fans  16  to exit the communication cabinet  10 . The air can exit through apertures or openings defined by the top wall  18  and other parts of portion  12  such as the inner upper wall  14 , by perforating portions of the top wall  18  or other parts of portion  12 . According to an embodiment of the invention air can exit through at least one shutter.  
      A complex of rods, flanges and panels (denoted  30 ) divide the space between the inner upper wall  14  and the bottom wall  32  of the communication to four rectangular-shaped sections  40 - 46 . Typically, communication equipment such as multiple communication boards are vertically positioned within dedicated rails that are connected to dedicated communication cages (not shown) that are installed within two upper sections  40  and  42 . Typically, high power supply and additional circuitry are positioned in the lower sections  44  and  46 .  
      Two sidewalls  70  and  72  are pivotally connected to portion  12 . The pivotal connection eases the access to communication equipment while facilitating to install the communication cabinet  10  near a wall.  
      Two front doors  50  and  52  are pivotally connected to portion  12 . Each door  50  and  52  has a single aperture within its lower portion. A first filter  60  is positioned within the aperture of first door  50  while a second filter  62  is positioned within the aperture of second door  52 .  
      Conveniently, air can flow through the inner space of communication cabinet  10 . During a first period (that can also be referred to as the cooling period) the fans  16  rotate such as to force air to enter the inner space through filters  60  and  62 .  
       FIG. 3  is a schematic illustration of airflows  100  and  102  within the communication cabinet  10  during a cooling period and  FIG. 4  is a schematic illustration of airflows  112  and  110  within the communication cabinet  10  during a dust removal period.  
      It is noted that both  FIG. 3  and  FIG. 4  are out of scale. It is further noted that these airflow illustrate the flow through an empty communication cabinet  10 . One skilled in the art will appreciate that the airflows within the various sections of communication cabinet  10  shall vary when communication equipment is installed within the cabinet. It is further noted that the presence of communication equipment within the communication cabinet  10 , the shape of the various sections (including the upper section  40 ) and the usage of multiple fans can alter the airflows (for example by inducing turbulences) but that air will substantially follow one or more path that starts at filters  60  and  62  and ends at shutters  80  and  82 .  
      During a cooling period fans  16  rotate at clockwise direction and force air that enters through filters  60  and  62  to flow (as illustrated by airflows  100  and  102 ) through sections  40  and  42 , through fans  16  and the upper section  48  and finally to exit the communication through shutters  80  and  82 . Typically, during the cooling period the filters  60  and  62 , and especially their outer surfaces, get filled with dust and particles.  
      During a dust removal period fans  16  rotate at counterclockwise direction and force air to flow (as illustrated by airflows  110  and  112 ) through sections  40  and  42  and to exit through filters  60  and  62 . The air that exits through filters can remove the dust.  
      Conveniently, during the dust removal period air is not allowed to enter the communication cabinet  10 , thus causing the communication equipment within the communication cabinet  10  to gradually heat. The shutters  80  and  82  are substantially closed during the duct removal period.  
      In order to prevent malfunctions, the dust removal period is relatively short. Its length can be determined by estimating the thermal behavior of the communication cabinet  10  and especially the behavior of communication circuitry within the cabinet  10 . The dust removal period can also depend upon temperatures measured within one or more locations of the communication cabinet  10 .  
       FIG. 3  further schematically illustrates a controller  13  that controls the rotation of fans  16 . It is noted that the control  13  controls the polarity of power supplied to the fans by sending control signals to power supply  11 . It is noted that various prior art methods and devices can be used for controlling the fans and that the controller  13  can be located within various locations of communication cabinet, including within a communication cage.  
       FIG. 7  illustrates a controller  13 , as well as various components of a fan control circuitry, according to an embodiment of the invention.  
      Controller  13  is connected to airflow sensor  21 , temperature sensor  27 , memory unit  25  and communication equipment controller  23 . Controller  13  is also connected to power supply  11  and can control the polarity of voltage provided to fans. It is noted that other control signals and methods can be applied.  
      According to an embodiment of the invention the sequence of cooling period and dust removal period can be repeated continuously. Controller  13  sends appropriate control signals to fans  16  and in response they force air to exit filters  60  and  62  or to exit through shutters  80  and  82 .  
      Conveniently, the controller  13  is connected to a pair of relays that can select between two power sources such as to reverse the polarity of voltage supplied to the fans.  
      According to another embodiment, controller  13  can initiate a dust removal session in response to signals provided to it by airflow sensor  21  or temperature sensor  27 . It can initiate a dust removal period when the airflow reduces to a predefined threshold or once a heating pattern of the communication cabinet may indicate that one or more filters are partially filled with dust. The pattern can be stored within memory unit  25  and can even be updated by the controller  13 .  
      The controller  13  can also initiate a dust removal period in response to the status of communication equipment, as indicated by communication equipment controller.  
      According to an embodiment of the invention the controller can shut down portions of the communication equipment when the temperature reaches a predetermined upper threshold.  
      According to another embodiment of the invention controller  23  can be connected a transmitter and report the status of the communication cabinet to a remote location. Thus, when failures occur or even when communication cabinet operates in a proper manner a remote location can receive status information.  
       FIG. 5  is a flow chart illustrating a method  300  for dust removal from a one or more filters. Method  300  starts by stage  310  of providing a communication cabinet that comprises at least one filter, whereas the at least one filter is positioned such as to substantially prevent dust from entering the communication cabinet.  
      Stage  310  is followed by stage  320  of rotating at least one fan at a first direction during a first period such as to cool at least one communication circuit installed within the communication cabinet. It is noted that the fans  16  of  FIG. 1  rotate at the same direction but in other configurations during the cooling period one or more fans that belong to a first group of fans can rotate at a first direction while one or more fans that belong to a second group of fans rotate at a second opposing direction.  
      Stage  320  is followed by stage  330  of rotating the at least one fan at a second opposing direction during a second period such as to remove dust from the at least one filter. Stage  330  is followed by stage  320 . It is noted that the fans  16  of  FIG. 1  rotate at the same direction but in other configurations during the dust removal period one or more fans that belong to a first group of fans can rotate at the second direction while one or more fans that belong to a second group of fans rotate at the first direction.  
      According to an embodiment of the invention the first period is substantially longer than the second period. The inventors used a first period of about one hour or few hours and a second period of about one minute.  
      According to an embodiment of the invention method  300  further includes stage  315  of estimating a heating of at least one communication circuit within the communication and in response determining a length of the second period.  
      According to an embodiment of the invention stage  330  further includes receiving an indication about a temperature of at least one communication circuit within the communication period and in response adjusting the second period. Conveniently, the second period ends if the measured temperature reaches a predefined threshold. It is noted that the length of the second period can depend upon said measurement alone (for example—the rotation to the second opposing direction continues until the equipment reaches a certain temperature), or may be dependent upon said measurement and a predefined time period. The latter can include rotating at the second opposing direction until either a predetermined time passes or the measured temperature reaches the threshold.  
      According to an embodiment of the invention stage  320  of rotating of at least one fan during a first period includes forcing air from a low portion of the communication chamber to a high portion of the communication chamber.  
      According to yet a further embodiment of the invention stage  320  further includes allowing air to flow through at least one shutter and stage  330  include substantially preventing air from entering the communication cabinet via the at least one shutter.  
      According to various embodiments of the invention the length of each period and even the manner in which fans are activated (for example the amount of activated fans) and by dynamically altered, either in accordance to a predefined pattern or in response to signals provided to controller  13 .  
       FIG. 6  is a flow chart illustrating a method  350  for dust removal from a filter. Method  350  differs from method  300  by stage  325  of checking if the airflow within the communication cabinet  10  is satisfactory. If so, stage  325  is followed by stage  320 , else stage  325  is followed by stage  330 . The airflow can be measured by flow meters but can also be estimated in response to the thermal behavior of the communication cabinet. For example if the communication cabinet reaches a certain temperature or tends to heat more quickly in comparison to an expected pattern than method  350  assumes that there is an airflow malfunction.  
      Those of skill in Variations, modifications and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims.