Abstract:
A heat dissipation device includes a heat sink ( 10 ) in thermal contact with a first heat-generating electronic component. A fan duct ( 30 ) receives the heat sink therein and has an inlet ( 350 ) and an outlet ( 302 ) at opposite sides thereof. A fan ( 20 ) is mounted in the fan duct at the inlet. A portion of airflow generated by the fan flows through the heat sink to cool the first heat-generating electronic component. A shutter ( 31 ) is mounted on the fan duct. Another portion of the airflow generated by the fan flows through the shutter to blow a second heat-generating electronic component located beside the first heat-generating electronic component and outside the fan duct.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a heat dissipation device having a fan duct to guide an airflow flowing from a fan to electronic devices in a computer system. 
   DESCRIPTION OF RELATED ART 
   The central processing unit (CPU) mounted on the motherboard in a computer is the center of operations of the computer. During the operation of the computer, the CPU produces heat. The heat must be quickly carried away from the CPU during the operation of the computer. Excessively high temperature causes the CPU to work abnormally. In addition to the CPU, hard disks and MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) near to the CPU are also sources of heat that need to be cooled. 
   Typically, a related heat sink having a fan duct is mounted on the CPU to remove heat therefrom. A fan is often mounted on the fan duct to provide forced airflow to the heat sink. One example is disclosed in U.S. Pat. No. 6,304,445 B1. However, the related heat sink mounted in the computer can only dissipate heat generated by the CPU, and cannot dissipate the heat generated by other heat-generating electronic components, such as hard disks and MOSFETs next to the CPU because the airflow generated by the fan is not guided to blow onto the other heat-generating electronic components. 
   Thus, it is desired to devise a heat dissipation device which can not only dissipate the heat generated by the CPU but also dissipate the heat by other electronic components beside the CPU. 
   SUMMARY OF THE INVENTION 
   According to a preferred embodiment of the present invention, a heat dissipation device includes a heat sink in thermal contact with a first heat-generating electronic component. A fan duct receives the heat sink therein and has an inlet and an outlet at opposite sides thereof. A fan is mounted in the fan duct at the inlet. A portion of airflow generated by the fan flows through the heat sink to cool the first heat-generating electronic component. A shutter is mounted on the fan duct. Another portion of the airflow generated by the fan flows through the shutter to blow onto a second heat-generating electronic component. 
   Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Many aspects of the present device 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 device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is an exploded isometric view of a heat dissipation device in accordance with an embodiment of the present invention; 
       FIG. 2  is an isometric view of a fan duct with a shutter of the heat dissipation device of  FIG. 1 . 
       FIG. 3  is a view similar to  FIG. 2 , but shown from an opposite bottom aspect; 
       FIG. 4  is an assembled view of  FIG. 1 ; and 
       FIG. 5  is a view similar to  FIG. 4 , but shown from another aspect. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made to the drawing figures to describe a heat dissipation device having a fan duct in accordance with a preferred embodiment of the present invention in detail. 
     FIG. 1  and  FIG. 4  show a heat dissipation device mounted on a printed circuit board (not shown). The heat dissipation device comprises a heat sink  10 , a fan  20  mounted on a side of the heat sink  10  and a fan duct  30  receiving the heat sink  10  and the fan  20  therein. 
   The heat sink  10  comprises a base  12  and a plurality of fins  14  extending upwardly from the base  12 . The base  12  has a generally rectangular configuration and forms a pair of ears  120  extending horizontally and outwardly from opposite lateral sides of the base  12 . The base  12  thermally engages with a CPU (not shown) mounted on the printed circuit board for absorbing heat generated by the CPU. A pair of through holes  122  are defined in each of the ears  120  of the base  12 . The fins  14  form a plurality of channels (not labeled) therebetween, the channels extending along a front-to-rear direction. The fins  14  have a stepped configuration at one of lateral sides thereof to decrease air resistance, for facilitating flow of a portion of airflow generated by the fan  20  toward other electronic components beside the CPU via a shutter  31  coupled to the fan duct  30 . 
   Referring also to  FIGS. 2-3 , the fan duct  30  acts as a shield comprising a substantially rectangular top plate  32  and a pair of lateral baffle plates  33 ,  34  extending perpendicularly and downwardly from opposite lateral edges of the top plate  32 . A width of the top plate  32  adjacent to a front end is shorter than that of a rear end of the top plate  32 . A square faceplate  35  is formed at the front end of the top plate  32  and connects with the lateral baffle plates  33 ,  34 . An opening  350  acting as an inlet is defined in the faceplate  35  for drawing airflow therefrom. The faceplate  35  has four corners  352  beside the opening  350 . Each of the corners  352  defines a through hole  3520  therein. Four flexible bars  37  (shown in  FIG. 1 ) are adhered to four edges of the faceplate  35  and contact with a computer panel to reduce vibration as the fan  20  is operated. A rib  304  connects opposite bottom ends of the baffle plates  33 ,  34  at rear ends of the baffle plates  33 ,  34  to form an outlet  302  for the airflow. A pair of brackets  38  connect to outer circumferential surfaces of the two baffle plates  33 ,  34 . Each of the brackets  38  comprises a vertical side  381  parallel to the baffle plate  33 ,  34  and a horizontal side  382  perpendicularly bent from a bottom end of the vertical side  381 , wherein the horizontal side  382  connects with a bottom edge of the baffle plate  33 ,  34 . The horizontal side  382  defines a pair of threaded holes  3820  therein. Two mounting poles  36  are respectively formed on the each of the brackets  38  and connected to the outer circumferential surface of the two baffle plates  33 ,  34  for permitting passage of fasteners  50  to mount the heat dissipation device on the printed circuit board. The threaded holes  3820  are located between the two mounting poles  36 . A window  340  is defined in the baffle plate  34 . A notch  342  is defined at an edge of the window  340  and communicates with the window  340 . 
   The shutter  31  is separated from the fan duct  30  and comprises a pair of spaced and parallel mounting plates  310  extending horizontally. Each of the mounting plates  310  has a rectangular configuration. A plurality of parallel vanes  312  is obliquely sandwiched between the two mounting plates  310 . The vanes  312  extend toward the window  340  of the fan duct  30  and beyond the mounting plates  310 . Each of the vanes  312  is a rectangular flake. An extending direction of each vane  312  is oblique to an extending direction of the mounting plates  310 . The vanes  312  have different lengths in the extending direction thereof which are gradually increased from front ends to rear ends of the mounting plates  310 . The shortest vane  312  and the longest vane  312  are connected to two opposite front and rear ends of the mounting plates  310  such that a part of the longest and shortest vanes  312  and the mounting plates  310  cooperatively form a parallelogram frame (not labeled). The longest vane  312  forms a block  3120  at an outer side thereof. The shortest vane  312  forms a hook  3122  at a free edge thereof. 
   Again referring to  FIG. 1 , the fan  20  has a substantially square in configuration. The fan  20  has four corners  22  corresponding to the corners  352  of the faceplate  35  of the fan duct  30 . Each of the corners  22  defines a threaded hole  220  located corresponding to the through holes  3520  of the faceplate  35 . 
   Referring to FIGS.  1  and  4 - 5 , in assembly, the fan  20  is received in the fan duct  30  and aligned with the opening  350  of the faceplate  35 . Four corners  22  of the fan  22  abut against the corresponding four corners  352  of the faceplate  35  of the fan duct  30 . Four screws  40  extend through the through holes  3520  of the faceplate  35  and are threadedly engaged in holes  220  defined in the corners  22  of the fan  20 . The base  12  of the heat sink  10  is located at a bottom end of the fan duct  30  and each ear  120  of the base  12  is located between two mounting poles  36  of each of the baffle plates  33 ,  34 , thus covering the stepped fins  14  of the heat sink with the fan duct  30 . The fan duct  30  is fixed to the heat sink  10  by extending four screws (not shown) through the through holes  122  defined in the base  12  to threadedly engage with the threaded holes  3820  defined in the brackets  38  of the fan duct  30 . The heat dissipation device is mounted on the printed circuit board by extending the four fasteners  50  in the mounting poles  36  through the printed circuit board to threadedly engage with a retainer (not shown) attached to a bottom side of the printed circuit board. The vanes  312  of the shutter  31  extend into the inner space (not labeled) of the fan duct  30 . By provision of the stepped configuration of the fins  14 , the vanes  312  cannot interfere with the fins  14 . The frame of the shutter  31  abuts against outer edges of the window  340  of the baffle plate  34  of the fan duct  30 . The block  3120  of the longest vane  312  engages with an inner side of the baffle plate  34  adjacent to the window  340 . The hook  3122  of the shortest vane  312  is engaged in the notch  342 . Thus, the shutter  31  is detachably coupled to the fan duct  30  at the window  340 . The shutter  31  faces towards other heat-generating electronic components beside the CPU such as hard disks or MOSFETs. The vanes  312  of the shutter  31  is oblique towards the other heat-generating electronic components for facilitating airflow for blowing the other heat-generating electronic components and dissipating the heat generated thereby. 
   In use, heat generated by the CPU is firstly absorbed by the base  12  of the heat sink  10  contacting with the CPU; then, the heat reaches the fins  14 . The fan  20  provides a forced airflow to the fins  14 . The airflow flows through passages between the fins  14  thus removing heat from the fins  14 . A part of the airflow in the heat sink  10  flows outwardly through the shutter  31  to take away heat from the other heat-generating electronic components. Therefore, the airflow generated by the fan  20  can cool not only the CPU but also the other heat-generating electronic components beside the CPU. The other heat-generating electronic components are located outside the fan duct  30 . 
   In the present invention, if the other heat-generating electronic components generate little heat which does not need being dissipated by a forced airflow, the shutter  31  of the invention can be removed and replaced by an auxiliary plate (not shown) covering the window  340  of the fan duct  30 . 
   It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of 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.