Abstract:
An air duct includes two spaced sidewalls, a top wall connected between tops of the sidewalls, an extension plate pivotably mounted between tops of the sidewalls in front of the top wall, and a deformable portion to maintain the extension plate coplanar with the top wall.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a heat dissipation system including an air duct. 
         [0003]    2. Description of Related Art 
         [0004]    For an air duct, a space is often provided between tops of the air duct and a fan, for a user to extend a hand through to handle the fan. As a result, airflow from the fan may flow out of the air duct through the space, which will reduce the heat dissipation efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, all the views are schematic, and like reference numerals designate corresponding parts throughout the several views. 
           [0006]      FIG. 1  is an exploded, isometric view of a first exemplary embodiment of a heat dissipation system. 
           [0007]      FIG. 2  is an assembled, isometric view of  FIG. 1 . 
           [0008]      FIG. 3  is an assembled, isometric view of a second exemplary embodiment of a heat dissipation system. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The disclosure, including the accompanying drawings, is illustrated by way of example and not by way of limitation. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         [0010]      FIGS. 1 and 2  shows an exemplary embodiment of a heat dissipation system. The heat dissipation system include a base board  10 , an air duct  30  mounted on the base board  10 , and a row of fans  20  mounted on the base board  10  and positioned adjacent to a front side of the air duct  30 . 
         [0011]    The air duct  30  includes a plurality of spaced side boards  34  perpendicularly rested on the base board  10 , a top board  32  perpendicularly mounted on tops of the side boards  34  opposite to the base board  10 , a plurality of poles  360  each connected between two adjacent side boards  34  and in front of the top board  32 , a plurality of extension boards  368  rotatably mounted to the poles  360 , and a plurality of maintaining elements  364 . An airflow channel  33  aligning with one of the fans  29  bound by every two adjacent side boards  34 , the base board  10 , and the top board  32 . In this embodiment, the maintaining elements  364  are torsion springs each including a coiled main body  365  fitted about one of the poles  360  and two legs  367  extending away from each other from opposite ends of the main body  365 . A hollow installation portion  366  extends from a side of each extension board  368  to fit about one of the poles  360 , thereby rotatably installing the extension board  368  to the pole  360 . The legs  367  of each torsion spring  364  are respectively abutted to an inner surface of the portion  366  and the top board  32 , to maintain the extension board  368  coplanar with the top board  32 , thereby covering a space between the top board  32  and a corresponding one of the fans  20 . The extension boards  368  are capable of being pivoted upward or downward to deform the torsion springs  364 , thereby exposing the spaces to detach the fans  20 . The extension boards  368  are then released, and the torsion springs  364  are restored to maintain the extension boards  368  coplanar with the top board  32 . 
         [0012]      FIG. 3  shows in another embodiment, the maintaining elements  364  are elastic lines or belts. Opposite ends of each flexible line are respectively fixed to a top of the top board  32  and an outer surface of a corresponding one of the extension boards  368 ; thereby maintaining the extension board  368  coplanar with the top board  32  to cover the space between the top board  32  and a corresponding one of the fans  20 . At this time, the extension boards  368  can be pivoted upward to expose the spaces. When the extension boards  368  are released, the extension boards  368  drops downward until the flexible line is stretched. 
         [0013]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and various changes may be made thereto without departing from the spirit and scope of the description or sacrificing all of their material advantages, the examples hereinbefore described merely being exemplary embodiments.