Patent Publication Number: US-2012037624-A1

Title: Electronic enclosure including a flame arrestor having a mechanical check valve

Description:
BACKGROUND OF THE INVENTION 
     Exemplary embodiments pertain to the art of electronic enclosures and, more particularly, to an electronic enclosure having a flame arrestor including a mechanical check valve. 
     Certain electronic enclosures, particularly those employed in environments containing flammable gases or liquids, are required by various standards setting institutes to include an explosion proof designation. The explosion proof designation denotes that the enclosure is designed to prevent internal combustions from exiting and igniting external flammable substances. In some cases, the enclosure includes a flame arrestor that prevents a flame front initiating within the enclosure from exiting to the surroundings. 
     Flame arrestors function by forcing a flame front through channels too narrow to permit continuation of a flame. The particular form of the channels can vary. For example, flame arrestors may include regular channels, such as those defined by a wire mesh or openings formed in a sheet metal plate, or irregular channels such as those provided with a randomly packed material. The particular size of the channels can vary depending upon the flammability of any associated fuel. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Disclosed is an electronic enclosure that includes a housing having a plurality of walls that define an interior portion. A flame arrestor is mounted at one of the plurality of walls of the housing. The flame arrestor includes a mechanical check valve. The mechanical check valve is configured and disposed to allow a fluid to exit the interior portion of the housing and prevent fluid from entering the interior portion of the housing. 
     Also disclosed is a motor drive system including a fan housing unit having a housing member provides with an interior zone. A motor drive unit is connected to the fan housing unit. The motor drive unit includes a housing having an interior portion. The housing includes at least one flame arrestor having a mechanical check valve moveable between a first position that fluidly isolates the interior portion and a second position that allows passage of fluid from the interior portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  is a lower left perspective view of a motor drive system in accordance with an exemplary embodiment; 
         FIG. 2  is a partially cut way view of the motor drive system of  FIG. 1  illustrating flame arrestors including mechanical check valves exploded from a motor drive unit; 
         FIG. 3  depicts the mechanical check valves of  FIG. 2  in a closed configuration; 
         FIG. 4  depicts the mechanical check valves of  FIG. 2  in an open configuration; 
         FIG. 5  depicts mechanical check valves in accordance with another aspect of the exemplary embodiment in a closed configuration; and 
         FIG. 6  depicts the mechanical check valves of  FIG. 5  in an open configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     A motor drive system  1  includes an electronic enclosure or motor drive unit  2  in accordance with an exemplary embodiment illustrated generally at  2  in  FIG. 1 . Motor drive unit  2  is mounted to a fan housing unit  3  having a motor housing unit  4 . Motor drive unit  2  includes a housing  8  having a first wall  10 , a second wall  11 , a third wall  12 , a fourth wall  13  and a bottom wall  15  that collectively define an interior portion  17  that houses a motor drive control  20 . Motor drive control  20  is configured and disposed to control a fan motor  25  ( FIG. 3 ) arranged within motor housing unit  4 . Fan motor  25  drives a fan  30  that is disposed within an interior zone  33  of fan housing unit  3 . In the exemplary embodiment shown, fan  30  takes the form of an axial fan. In further accordance with the exemplary embodiment, motor drive unit  2  is provided with a plurality of flame arrestors  40 - 43 . Flame arrestors  40 - 43  allow a flame front to pass from motor drive unit  2  into interior zone  33 . In addition, flame arrestors  40 - 43  can also prevent moisture from entering motor drive unit  2  from interior zone  33  of fan housing unit  3 . 
     Reference will now be made to  FIGS. 2-4  in describing flame arrestors  40 - 43 . As each flame arrestor  40 - 43  is similarly formed, a detailed description will follow with reference to flame arrestor  40  with an understanding that the remaining flame arrestors include corresponding structure. Flame arrestor  40  includes a blocking tube  60  having a first end  62  that extends to a second end  63  through an intermediate portion  65 . First end  62  includes a flange  70  that is designed to cooperate with bottom wall  15  to position blocking tube  60  within interior zone  33 . Second end  63  includes an angled surface  74  that minimizes any ingress of moisture from interior zone  33  to blocking tube  60 . In order to prevent any moisture that may enter blocking tube  60  from entering motor drive unit  2 , flame arrestor  40  includes a mechanical check valve  80  positioned within blocking tube  60 . 
     In accordance with one aspect of the exemplary embodiment, mechanical check valve  80  takes the form of a duckbill valve  84  that is inserted into blocking tube  60 . Duckbill valve  84  includes a first end section  87  that extends to a second end section  88 . First end section  87  defines an inlet section  90  and includes a flange section  92 . Flange section  92  is configured to locate duckbill valve  84  within blocking tube  60 . That is, flange section  92  mates with flange  70  to position duckbill valve  84  within blocking tube  60 . Second end section  88  of duckbill valve  84  defines an outlet section  96  that includes a valve member  100 . In accordance with the exemplary embodiment, valve member  100  is formed from a resilient material that is designed to deflect when subjected to a predetermined pressure. More specifically, duckbill valve  84  is normally in a closed configuration, such as shown in  FIG. 3 . In the closed configuration, any moisture that may exist within motor housing unit  4  is prevented from entering motor drive unit  2 . However, in the event that a pressure build up occurs within motor drive unit  2  from, for example, a combustion event, valve member  100  deflects to the open configuration as shown in  FIG. 4 . In the open configuration, duckbill valve  87  allows any pressure build up within motor drive unit  2  to pass into interior zone  33 . At the same time, duckbill valve  84  allows any flame front to pass into interior zone  33 . 
     Reference will now follow to  FIGS. 5 and 6 , wherein like reference numbers represent corresponding parts in the respective views, in describing a mechanical check valve  120  in accordance with another aspect of the exemplary embodiment. Mechanical check valve  120  takes the form of a spring valve  122  including a first end section  129  that extends to a second end section  130 . First end section  129  defines an inlet section  134  and includes a flange section  136 . In a manner similar to that described above, flange section  136  locates spring valve  122  in blocking tube  60 . Second end section  130  defines an outlet section  140  having a valve member  144 . 
     In a manner also similar to that described above, spring valve  122  is normally in a closed configuration, such as shown in  FIG. 5 . In the closed configuration, any moisture that may exist within interior zone  33  is prevented from entering motor drive unit  2 . However, in the event that a pressure build up occurs within motor drive unit  2  resulting from, for example, a combustion event, valve member  144  opens, as shown in  FIG. 6 , to allow pressure to escape into motor housing unit  4 . The pressure at which valve member  144  will open is determined by a spring  150  that extends between first and second end sections  129  and  130 . Spring  150  biases valve member  144  into the closed configuration. However, if pressure build up within motor drive unit  2  is sufficient to overcome the biased force of spring  150 , valve member  144  will shift to expose outlet section  140  to inlet section  134  to release the pressure into fan housing unit  4 . At the same time, mechanical valve  120  allows any flame front that may develop in motor drive unit  2  to pass into interior zone  33 . 
     At this point it should be understood that the exemplary embodiments provide an electronic enclosure including a device for preventing moisture from passing from an interior zone into the housing while allowing for pressure relief and flame diversion. More specifically, a motor fan installation may require a motor drive unit capable of explosive containment with pressure relief and flame direction control when located in an explosive environment. Moreover, the same installation may also require that the fan be subjected to a high moisture environment. The explosion proof housing includes a flame arrestor(s) that provides pressure relief and flame control. However, conventional flame arresters allow moisture to pass into the motor drive unit housing. The present exemplary embodiments not only provide the pressure relief and flame control but also provide a barrier to moisture. In this manner, the electronic enclosure can be more readily employed in moist environments such as condensers, evaporators and the like. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.