Abstract:
A heat dissipating device for cooling a heat-generating electronic device, includes a heat sink assembly ( 10 ) and a fan ( 20 ) mounted to a side of the heat sink assembly. The heat sink assembly includes a heat spreader ( 12 ), a plurality of fins ( 14 ), and heat pipes ( 16 ) thermally connecting the heat spreader and the fins. The fins include at least one fastening fin ( 146 ). The fastening fin includes a pair of mounting tabs ( 1462 ). The mounting tabs of the fastening fin are oriented towards the fan for mounting the fan on the heat sink assembly. The fastening fin functions not only for dissipating heat into a surrounding environment but also for connecting the fan to the heat sink assembly.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a heat dissipating device having a plurality of fins, wherein at least one fin functions as a fan holder to mount a fan on a heat sink of the heat dissipating device. 
   2. Description of Related Art 
   With the progress of technology electronic products are becoming lighter, thinner, shorter, and smaller. Therefore, the free space inside electronic products is becoming more and more limited. 
   In electronic products having broad applications, a heat dissipation device is commonly used in all kinds of industrial equipment. The conventional heat dissipation device commonly comprises a heat sink and a fan mounted to the heat sink. A fan holder or a fan fastener is used for connecting the fan and the heat sink to mount the fan onto the heat sink. U.S. Pat. No. 6,788,536 and U.S. Pat. No. 7,004,236 show examples of this kind of heat dissipation device. However, extra fan holders or fan fasteners not only waste space and raise cost, but also make the installation and maintenance of the fans troublesome. 
   Thus, it is desired to devise a heat dissipating device which can directly mount a fan thereon. 
   SUMMARY OF THE INVENTION 
   According to a preferred embodiment of the present invention, a heat dissipating device for cooling a heat-generating electronic device, includes a heat sink assembly and a fan mounted to a side of the heat sink assembly. The heat sink assembly includes a heat spreader, a plurality of fins, and heat pipes thermally connecting the heat spreader and the fins. The fins include at least one fastening fin. The fastening fin includes a pair of mounting tabs. The mounting tabs of the fastening fin are oriented towards the fan for mounting the fan on the heat sink assembly. 
   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 assembled view of a heat dissipating device in accordance with a preferred embodiment of the present invention; 
       FIG. 2  is an exploded view of the heat dissipating device of  FIG. 1 ; 
       FIG. 3  is an assembled view of a heat dissipating device in accordance with a second embodiment of the present invention; 
       FIG. 4  is an exploded view of the heat dissipating device of  FIG. 3 ; and 
       FIG. 5  is an enlarged isometric view of a bottom fin of the heat dissipating device of  FIG. 4  from a different aspect. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a heat dissipating device in accordance with a preferred embodiment of the present invention. The heat dissipating device is to be mounted on a printed circuit board (not shown) and comprises a heat sink assembly  10  and a fan  20  mounted to the heat sink assembly  10 . 
   Also referring to  FIG. 2 , the heat sink assembly  10  comprises a heat spreader  12 , a first fin assembly  14  and a second fin assembly  18 , with three parallel U-shaped heat pipes  16  thermally connecting the heat spreader  12  and the first and second fin assemblies  14 ,  18 . 
   The heat spreader  12  has a bottom face (not labeled) for contacting a CPU (not shown) mounted on the printed circuit board to absorb heat therefrom, and a top face  122  with three grooves  124 . Two mounting brackets  13  each with a pair of ears  132  are attached to opposite bottom sides of the heat spreader  12 . The heat spreader  12  thermally engages with the CPU mounted on the printed circuit board by extending four fasteners  50  through the four ears  132  to threadedly engage with a retainer (not shown) attached to a bottom side of the printed circuit board. 
   Each heat pipe  16  comprises a horizontal evaporating portion  160  and a pair of vertical condensing portions  162  parallel to each other. The condensing portions  162  extend from two opposite ends of the evaporating portion  160 . The evaporating portions  160  of the heat pipes  16  are soldered in the grooves  124  of the heat spreader  12 . The condensing portions  162  are extended through the first and second fin assemblies  14 ,  18 . 
   The first fin assembly  14  comprises a plurality of first fins (not labeled) each having a first flat body  140 . The second fin assembly  18  comprises a plurality of second fins (not labeled) each having a second flat body  180 . The bodies  140 ,  180  of the first and second fins are parallel to the heat spreader  12 . The bodies  140 ,  180  of the first and second fins are perforated with through holes  142 ,  182 . Each of the through holes  142 ,  182  has its respective annular sidewall  144 ,  184  that is formed during punching of its respective through hole  142 ,  182 . The condensing portions  162  of the heat pipes  16  are received in the through holes  142 ,  182  and soldered to the sidewalls  144 ,  184  so that the first fin assembly  14  and the second fin assembly  18  are combined with the condensing portions  162  of the heat pipe  16 . The first and second fin assemblies  14 ,  18  are both mounted on the evaporating portions  160  of the heat pipes  16 . The first fin assembly  14  has a top fin  146  and a bottom fin  147 . The top and bottom fins  146 ,  147  cooperatively function as a fan holder for mounting the fan  20  on a side of the first fin assembly  14 , in addition to their original function of heat dissipation. In this preferred embodiment of the present invention, the fan  20  is sandwiched between the first fin assembly  14  and the second fin assembly  18 . The top fin  146  and the bottom fin  147  have the same configuration and are mounted on top and bottom of the first fin assembly  14 . The top fin  146  has a body  1460  with a configuration similar to that of each of the bodies  140  of the first fins and a pair of tabs  1462  extending upwardly from a front edge of the body  1460 . The bottom fin  147  also has a body  1470  with a configuration similar to that of each of the bodies  140  of the first fins and a pair of tabs  1472  extending downwardly from a front edge of the body  1470 . The tabs  1462 ,  1472  are located at opposite ends of the edges of the bodies  1460 ,  1470  and oriented towards the fan  20 . The tabs  1462 ,  1472  correspond to four corners of the fan  20  and define threaded holes  1464 ,  1474  therein. 
   The fan  20  has a square configuration and comprises a pair of parallel plates  22 ,  24 . The plate  22  is oriented to the first fin assembly  14 , and the plate  24  is oriented towards the second fin assembly  18 . The fan  20  is inserted between the first and second fin assemblies  14 ,  18  after the heat sink assembly  10  is assembled together. Four screws  30  are extended through four corners of the plate  22  and threadedly engaged in the threaded holes  1464 ,  1474  of the tabs  1462 ,  1472  of the top and bottom fins  146 ,  147  of the first fin assembly  14 , thus attaching the fan  20  on the first fin assembly  14 . 
   When the fan  20  operates, airflow generated by the fan  20  flows through the first, second fin assemblies  14 ,  18  to take heat away therefrom. The first and second fin assemblies  14 ,  18  absorb the heat from the CPU. Accordingly, the heat generated by the CPU can be quickly dissipated. 
   Referring to  FIGS. 3-4 , a heat dissipation device according to a second embodiment of the present invention is shown. The heat dissipation device in the second embodiment comprises a heat sink assembly  10   a  and a fan  20   a  mounted on the heat sink assembly  10   a.    
   The heat sink assembly  10   a  comprises a heat spreader  12   a , a first fin assembly  14   a , a second fin assembly  18   a  mounted below the first fin assembly  14   a , three parallel U-shaped heat pipes  16   a  thermally connecting the heat spreader  12   a  and the first and second fin assemblies  14   a ,  18   a . The heat spreader  12   a  has the same configuration as the heat spreader  12  of the first preferred embodiment of the present invention and defines three parallel grooves  124   a  therein. Each heat pipe  16   a  comprises a horizontal evaporating portion  160   a  soldered into a corresponding groove  124   a  of the heat spreader  12   a  and a pair of vertical condensing portions  162   a  perpendicularly extending from two opposite ends of the evaporating portion  160   a.    
   The first fin assembly  14   a  comprises a plurality of first fins (not labeled) each having a first flat body  140   a  parallel to the heat spreader  12   a . Each first flat body  140   a  is perforated with through holes  142   a . The condensing portions  162   a  of the heat pipes  16   a  are soldered in the through holes  142   a  so that the first fins are combined with the heat pipes  16   a . The second fin assembly  18   a  is located between the condensing portions  162   a  of the heat pipes  16   a . The first fin assembly  14   a  has a top fin  146   a  and a bottom fin  147   a . The top and bottom fins  146   a ,  147   a  cooperatively function as a fan holder to mount the fan  20   a  on a front side of the first fin assembly  14   a , in addition to their original function of heat dissipation. The top fin  146   a  has a body  1460   a  with a configuration similar to that of each of the bodies  140   a  of the first fins and a pair of tabs  1462   a  extending upwardly from an edge of the body  1460   a . The bottom fin  147   a  also has a body  1470   a  with a configuration similar to that of each of the bodies  140   a  of the first fins and a pair of tabs  1472   a  extending downwardly from an edge of the body  1470   a . The tabs  1462   a ,  1472   a  are located on opposite ends of the edge of the bodies  1460   a ,  1470   a  and are oriented towards the fan  20   a . The tabs  1462   a ,  1472   a  correspond to four corners of the fan  20   a ; each tab  1462   a ,  1472   a  defines a threaded hole  1464   a ,  1474   a  therein. An inclined guiding plate  1471   a  is bent downwardly from a rear end of the body  1470   a , whereby a portion of the airflow generated by the fan  20   a  flows through the second fin assembly  18   a  and then is guided by the guiding plate  1471   a  to directly blow over other electronic components at a rear side of the CPU. A first and second opposite baffle walls  1473   a ,  1475   a  extend perpendicularly downwardly from two lateral sides of the body  1470   a  of the bottom fin  147   a , respectively. Referring also to  FIG. 5 , the second baffle wall  1475   a  has a length shorter than that of the first baffle wall  1473   a . A separator plate  1476   a  is perpendicularly bent from a rear end of the second baffle wall  1475   a  toward the first baffle wall  1473   a.    
   The second fin assembly  18   a  is formed by continuously bending a single metal plate. A bottom of the second fins  18   a  is soldered on the evaporating portions  160   a  of the heat pipes  16   a , and a top of the second fin assembly  18   a  is soldered to a bottom of the bottom fin  147   a  of the first fin assembly  14   a  in a manner such that the heat spreader  12   a , the evaporating portions  160   a  of the heat pipes  16   a , and the first and second fin assemblies  14   a ,  18   a  are thermally connected together, whereby the heat received by the evaporating portions  160   a  is immediately transferred to the first and second fins of the first and second fin assemblies  14   a ,  18   a . A free end of the separator plate  1476   a  abuts against a corresponding lateral side of the second fin assembly  18  and a bottom edge of the separator plate  1476   a  intimately contacts with a top surface of the heat spreader  12   a , thus preventing a portion of the airflow generated by the fan  20   a  from flowing through a gap between the second baffle wall  1475   a  and the lateral side of the second fin assembly  18   a  along the front-to-rear direction. 
   In assembly of the second embodiment of the present invention, the fan  20   a  is mounted to the front side of the first fin assembly  14   a  by bringing screws  30  to extend through the corners of the fan  20   a  and screw into the threaded holes  1464   a ,  1474   a  of the top and bottom fins  146   a ,  147   a  of the first fin assembly  14   a . Thus, the fan  20   a  and the heat sink assembly  10   a  are connected together. 
   In the present invention, by the provision of the tabs formed on the fins, the fan can be firmly mounted to the side of the heat sink assembly without any fan holders. Thus, cost of the heat dissipation device is decreased. 
   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.