Patent Publication Number: US-2007121309-A1

Title: Shielding device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a shielding device, and particularly to a shielding device for providing EMI (electromagnetic interference) protection for electronic components on a circuit board.  
      2. Description of the Prior Art  
      U.S. Pat. No. 6,711,032 B2 discloses a conventional shielding device comprising a cover and a base frame mounted on a printed circuit board (PCB). A plurality of flanges are bended from outer edges of the cover and define multiple apertures extending therethrough. The base frame comprises side walls with a plurality of outwardly dome shaped projections for engaging with the apertures when the shielding device is in closed position. The projections can firmly engaging with the apertures in a height direction of the shielding device, and wherein the dimension of the apertures in the longitude direction is larger than that of the projections. However, since the projections are formed in the frame by stamping process, the frame is sometimes troublesome to provide excellent flatness when mounted on the PCB, thereby increasing the cost of the manufacture.  
      Thus there is a need for an improved shielding device which can overcome the disadvantage of the prior art.  
     BRIEF SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a shielding device with excellent flatness and low cost.  
      To fulfill the above-mentioned objects, according to a preferred embodiment of the present invention, a shielding device comprises a frame and a top cover enclosing the frame. The frame comprises a top wall and a plurality of side walls depending downwardly from the top wall. The side walls comprise a plurality of ellipse shaped mounting holes defined therethrough. The top cover comprises a body portion and a plurality of flanges extending downward from the body portion. The flanges define a plurality of dome shaped projections and a plurality of half ball shaped protrusions all projecting inwardly from the central portions of the flanges. The projections can firmly engaging with the mounting holes in a height direction, and wherein the dimension of mounting holes in a longitude direction is lager than that of the projections, thereby providing a wide possible engaging area. So it doesn&#39;t need precisely mating relationship between the projections and the mounting holes and facilitates the assembled process of the shielding device. Besides, the protrusions are intervening with the frame and form a small gap between the frame and top cover, thereby it is easy to disassemble the shielding device. Further more, the projections are disposed on the top cover instead of the frame, thereby providing excellent flatness of the frame and decreasing the cost of the manufacture.  
      Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which:  
       FIG. 1  is a perspective view of a shielding device in accordance with the present invention;  
       FIG. 2  is another perspective view of  FIG. 1 ;  
       FIG. 3  is an exploded view of the shielding device in accordance with the present invention;  
       FIG. 4  is another exploded view of  FIG. 3 ;  
       FIG. 5  is a partly view of the shielding device according to the present invention;  
       FIG. 6  is a partly cross-sectional view of the edge of the shielding device taken along line  6 - 6  of  FIG. 1 ; and  
       FIG. 7  is a partly cross-sectional view of the edge of the shielding device taken along line  7 - 7  of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Reference will now be made in detail to the preferred embodiment of the present invention.  
      Referring to  FIGS. 1-4 , a shielding device  1  comprises a frame  10  and a top cover  11  for enclosing the frame  10 . The frame  10  is mounted on a circuit board (not shown) by soldering and encloses a plurality of electronic elements (not shown) on the circuit board within its bound. Both of the frame  10  and the top cover  11  are made from a metal or a metal alloy.  
      The frame  10  comprises a narrow, horizontal top wall  100  and a plurality of side walls  101  depending downwardly from outer edges of the top wall  100  wherein the side walls  101  are separated from each other. The frame  10  further defines a pair of openings  103 ,  105  and a separated wall  104  between said openings  103 ,  105 . The openings  103 ,  105  are adapted for enclosing the electronic elements on the circuit board. The side walls  101  comprise a plurality of ellipse shaped mounting holes  102  defined therethrough. The dimension in the longitude direction of the mounting holes  102  is signed as “W”. The dimension in the height direction perpendicular to the longitude direction of the mounting holes  102  is signed as “V” which is shorter than “W” (seen in  FIG. 5 ).  
      The top cover  11  comprises a body portion  110  and a plurality of holes  112  formed therein. A plurality of flanges  111  extends from outer edges of the body portion  110 . Some flanges  111  define a number of dome shaped projections  114  projecting inwardly from the central portions of the flanges  111  for detachably engaging with corresponding mounting holes  102  of the frame  10 . Other flanges  111  contain a plurality of half ball shaped protrusions  113  extending inwardly from the central portions of the flanges  111  for intervening against the frame  10 . As shown in  FIG. 4 , each protrusion  113  is smaller than a projection  114 .  
      During assembly, the flanges  111  of the top cover  11  are brought to slide in the height direction over the side walls  101 , and the dome shaped projections  114  easily encounter the mounting holes  102 . The top cover  11  is firmly assembled to the frame  10  by the engagement of the projections  114  and the mounting holes  102  in the height direction. The protrusions  113  are intervening with the frame  10  thereby forming a small gap between the frame  10  and top cover  11  (seen in  FIG. 7 ). During disassembly, the half ball shaped protrusions  113  slide over the side walls  101  and the dome shaped projections  114  are easily detached from the mounting holes  102 , so that the top cover  11  can be separated from frame  10 , thereby facilitating repair of the electronic elements when necessary.  
      Referring to  FIGS. 5-6 , the dimension of mounting holes  102  “V” is substantially the same as that of the projections  114 . Therefore, the projections  114  can firmly engaging with the mounting holes  102  in the height direction. Besides, the dimension “W” of each mounting hole  102  is larger than that of the projection  114 , thereby providing a wide possible engaging area between the projections  114  and the mounting holes  102  in the longitude direction perpendicular to the height direction. It doesn&#39;t need precisely mating relationship between the projections  114  and the mounting holes  102  in the longitude direction, thereby facilitating the assembled process of the shielding device  1 .  
      It is to be understood, however, that even though numerous, characteristics and advantages of the present invention have been set fourth in the foregoing description, together with details of the structure and function of the invention, the disclosed is illustrative only, and changes may be made in detail, especially in matters of number, shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.