Abstract:
A heat sin assembly includes a heat sink and a fixing device. The heat sink assembly includes a heat-absorbing base, a heat pipe attached to base, and a plurality of stacked fins through which the heat pipe extends. A fixing device is detachably engaged with the base and defining a plurality of apertures therein far from the base. A plurality of fasteners is positioned into the apertures of the fixing device to be ready to secure the heat sink assembly. The fasteners are movable relative the fixing device when pressed. The fixing device is readily coupled to the heat sink and removed therefrom so that the heat sink assembly is easily updated with another fixing device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is related to one corresponding U.S. patent applications entitled “HEAT DISSIPATION DEVICE ASSEMBLY”, recently filed on Sep. 30, 2004 with application Ser. No. 10/955,610. The disclosure of the above-identified application is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to cooling of electronic devices, and particularly to heat sink assembly with a fixing device which can be readily coupled to the heat sink and removed therefrom.  
         [0004]     2. Prior Art  
         [0005]     Developments in integrated circuits technology have led to remarkable improvements of performances of electronic devices. During operation of many contemporary electronic devices, large amounts of heat are produced. Such heat must be efficiently dissipated out from the electronic devices, to prevent it from becoming unstable or being damaged. Typically, a heat sink is attached to an outer surface of the electronic devices to facilitate dissipation of heat therefrom.  
         [0006]     A conventional heat sink assembly often uses a clip to attach a heat sink to an electronic device. The clip is placed into a channel of the heat sink and presses a top surface of a base of the heat sink. However, the channel is a space which would otherwise be occupied by a number of heat-dissipating fins. This results in lower heat dissipation efficiency of the heat sink.  
         [0007]     A heat sink assembly using a clip placed under the heat sink to attach the heat sink to the electronic device is developed. An example of such an assembly is disclosed in U.S. Pat. No. 6,851,467 B1. It is apparently seen the heat sink has a bulky heat dissipating portion and a contrastively small base for fitting in with great heat generated by a central process unit (CPU) and high density of other electronic elements around the CPU on a printed circuit board. In order to fasten the heat sink to the CPU firmly, a clip is positioned in a groove around a conductive core of the heat sink and cannot be removed unless other components of the heat sink assembly are not disassembled. As a result, the heat sink assembly cannot be used to other situation where the printed circuit board is provided a different engaging structure except that the whole heat sink assembly is disassembled and updated with another suitable clip coupled to the heat sink. Operation of updating the heat sink assembly with another clip is cumbersome. This leads to that the heat sink is used narrowly.  
         [0008]     Therefore, an improved heat sink assembly which overcomes above problems is desired.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, what is needed is to provide a heat sink assembly with a fixing device which is readily assembled to and removed from a heat sink for substitution.  
         [0010]     A heat sink assembly of an embodiment of the invention comprises a heat-absorbing base, a heat pipe attached to base, and a plurality of stacked fins through which the heat pipe extends. A fixing device is detachably engaged with the base and defining a plurality of apertures therein far from the base. A plurality of fasteners is positioned into the apertures of the fixing device to be ready to secure the heat sink assembly.  
         [0011]     Another embodiment of the invention comprises a heat sink and a fixing device. The heat sink includes a base, with a step formed on a periphery face of the base, a plurality of fins above the base, and at least a heat pipe which is attached to the base and extends away from the base and through the fins. An accommodating space is defined between the step and the fins, around the base. The fixing device comprises a frame defining an opening for receiving the base. The frame is removably positioned in the accommodating space, surrounding the base, and abutting against the step thereof for preventing the fixing device from separation from the heat sink. A plurality of fixing arms extends from the frame for receiving fasteners.  
         [0012]     Other, advantages and novel features of the present invention will be drawn from the following detailed description of some embodiments of the present invention together with the attached drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is an exploded view of a heat sink assembly with fixing devices of a preferred embodiment in accordance with the present invention;  
         [0014]      FIG. 2  is a partly assembled view of  FIG. 1 ;  
         [0015]      FIG. 3  is a fully assembled view of  FIG. 1 ;  
         [0016]      FIG. 4  is an exploded isometric view showing a base and a fixing device of a second embodiment;  
         [0017]      FIG. 5  is an exploded isometric view showing a base and a fixing device of a third embodiment;  
         [0018]      FIG. 6  is an assembled view of  FIG. 5 ; and  
         [0019]      FIG. 7  is an exploded view showing a base and a fixing device of a fourth embodiment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     In the following detailed description of the embodiment, reference is made to the accompanying drawings that illustrate embodiments of the present invention and their practices.  FIG. 1  shows a heat dissipation assembly like a heat sink assembly of a preferred embodiment in accordance with the present invention. The heat sink assembly is for being mounted to a printed circuit board (not shown) to contact an electronic device or a heat source, such as a CPU (not shown), for heat dissipation. The heat sink assembly comprises a heat sink  100 , a fixing device  150  and a plurality of fasteners  160 .  
         [0021]     Please refer to  FIG. 2  together with  FIG. 1 , the heat sink  100  has a disc-shaped base  110 . The base  110  has a bottom face (not labeled) for contacting the CPU, a top face (not labeled) opposing the bottom face and defining two pair of parallel grooves  113 , and a periphery face (not labeled) between the bottom face and the top face. The periphery face defines continuous external screw thread  115 . Two pairs of L-shaped heat pipes  120  are attached to the base  110 , with one end of each heat pipe  120  is fixedly received in a corresponding groove  113  of the base  110 . Another end of each heat pipe  120  extends away from the top face of the base  110  and through a plurality of stacked fins  130  which are parallel to the top face of the base  110 .  
         [0022]     The fixing device  150  includes a frame  152  defining a circular opening  154  with continuous inner screw thread  155  for engaging with the external screw thread  115  on the base  110  of the heat sink  100 . Two pairs of clamping arms  156  extend from the frame  152  outwardly. An aperture  157  for receiving a fastener  160 , such as bolt, is defined on each clamping arm  156  near to free end thereof. The fixing device  150  can be coupled to the heat sink  100  by rotating the fixing device  150  relative to the heat sink  100  to reach a full engagement between the internal screw thread  155  of the fixing device  150  and the external screw thread  115  of the base  110 . Each fastener  160  extends through a spring  170  and is received in one aperture  157  of the fixing device  150 . The springs  170  on the fasteners  160  are compressed lightly to make the fasteners  160  positioned in the apertures  157  of the clamping arms  156  and movable up and down relative to the clamping arms  156  when the fasteners  160  are pressed. The fasteners  160  may be driven to extend tightly into holes of the printed circuit board to clamp the heat sink assembly down against the CPU. Combination of the heat sink  100  and the fixing device  150  is shown in  FIG. 3 . The fixing device  150  can be removed conveniently from the heat sink  100  by reversely rotating the fixing device  150  relative to the heat sink  100 .  
         [0023]     From above description of the preferred embodiment, we see that the fixing device  150  can be coupled to the heat sink  100  readily and removed therefrom by rotation of the fixing device  150  relative to the heat sink  100 , without disassembling the heat sink  100 . Thus, the heat sink assembly can be readily updated by displacing the fixing device  150  with another one that has a different dimension, such as longer clamping arms. The updated heat sink assembly can be used to another situation where there is a different engaging structure corresponding to the updated heat sink assembly.  
         [0024]     Engagement between the base of the heat sink and the fixing device in the present invention is not limited to the preferred embodiment as above-mentioned. It can be achieved by other variations.  FIG. 4  illustrates a second embodiment of the present invention. It has the same heat pipes, fins and fasteners as the first embodiment. For concision, only a disc-shaped base  210  of a heat sink (not shown) and a fixing device  250  are shown in  FIG. 4 . In this embodiment, a plurality of first external teeth  213  and second external teeth  213 ′ extend radially outwardly from a periphery face of the base  210 . The first external teeth  213  are spaced evenly apart by a series of external gaps  215 , so the second external  213 ′ teeth are. The first external teeth  213  and second external teeth  213 ′ are opposed to and separated from each other by a groove  214  therebetween. The fixing device  250  has a frame  252  defining an opening  254  in a center thereof. A plurality of internal teeth  253  extend radially inwardly from an inner periphery of the frame  252 , corresponding to the external gaps  215  of the base  210 . Adjacent internal teeth  253  are separated by an internal gap  255 . Similar to the first embodiment, the fixing device  250  has two pairs of clamping arms  256  extending from the frame  252  and defining apertures  257  thereon. When assembly, the base  210  is disposed above the fixing device  250 , the first external teeth  213  of the base  210  oppose the internal gaps  255  of the fixing device  250 . The first external teeth  213  pass through the internal gaps  255 , and the frame  252  of the fixing device  250  is positioned between the first external teeth  213  and the second external teeth  213 ′ and within the groove  214  of the base  210 . Then, the fixing device  250  is rotated until the internal teeth  253  of the fixing device  250  abut the corresponding first external teeth  213  of the base  210 . The fixing device  250  is thereby prevented from separation from the base  210  of the heat sink. The fixing device  250  can be removed readily from the heat sink by rotation of the fixing device  250  until the first external teeth  213  oppose the internal gap  255 .  
         [0025]      FIG. 5  and  FIG. 6  show a third embodiment of the present invention. Also for concision, only a base  310  of a heat sink, a fixing device  350  and a stopping ring  380  are shown. The base  310  comprises an upper section (not labeled) and a lower section  315  which is threaded around thereof. The stopping ring  380  defines an opening  384  with an internal screw thread  385  for engaging with the lower section  315  of said base  310 . The fixing device  350  has a frame  352  defining an opening  354  corresponding to the base  310 , and clamping arms (not labeled) same as that in the first embodiment. Referring to  FIG. 6 , when assembly, the lower section  315  of the base  310  passes through the opening  354  of the fixing device  350  and screws into the opening  384  of the stopping ring  380 . The frame  352  of the fixing device  350  is positioned in an accommodating space between the stopping ring  380  and the fins (not shown) and surrounds the upper section of the base  310 , being prevented from escaping from the base  310 . The fixing device  350  can be removed readily from the heat sink after the stopping ring  380  is screwed off.  
         [0026]     For further sufficiently understand the present invention, a fourth embodiment is disclosed as follows. Referring to  FIG. 7 , only a base  410  and a fixing device  450  is shown also for concision. Other elements, such as heat pipes, fins are same as that in the first embodiment and not shown in  FIG. 7 . The base  410  defines an annular groove  415  around thereof. The fixing device  450  is divided into two pieces and has a pair of sub-frames  451 ,  452 . Each sub-frame  451 ,  452  has a semicircle hooping portion  453 ,  454  which has the same thickness as the width of the groove  415  of the base  410 . Each sub-frame  451 ,  452  has two clamping arms  455 ,  456  which extend from the hooping portion  453 ,  454  and define apertures  457 ,  458 . When assembly, the two sub-frames  451 ,  452  are respectively received in the annular groove  415  of the base  410  and jointed into a frame around the base  11   d , forming a Provisional combination of the heat sink (not shown) and the fixing device  450 . When several fasteners (not shown) extend the apertures  457 ,  458  of the fixing device  450  and into holes (not shown) in a printed circuit board (not shown), the pair of sub-frames  451 ,  452  are fixedly coupled to the heat sink and the assembly is mounted on the printed circuit. The fixing device  450  can be removed readily from the heat sink after the fasteners is pulled out of the holes of the printed circuit board.  
         [0027]     It is recognized that the invention may be susceptible to various other modifications and alternative constructions in view of this disclosure. Although the invention has been shown and described in detail herein by a preferred embodiment and certain alternatives, it should be understood that there is no intention of limiting the invention strictly to this. But rather it is the intention to cover all such other modifications and alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.