Abstract:
A heat dissipation device is for contacting with a heat generating electronic device to remove heat from the electronic device. The heat dissipation device includes a base, a plurality of fins arranged on the base and at least one heat pipe thermally positioned on the base. The heat pipe includes a U-shaped first portion, a second portion and a connecting portion interconnecting the first and second portions. The first portion of the heat pipe thermally engages the base. The second portion of the heat pipe is located above the base, and thermally engages with the plurality of fins.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to heat dissipation devices for use in removing heat from electronic devices, and more particularly to a heat dissipation device incorporating a heat pipe for improving heat dissipation efficiency of the heat dissipation device.  
       DESCRIPTION OF RELATED ART  
       [0002]     During operation of an electronic device such as a computer central processing unit (CPU), a large amount of heat is often produced. The heat must be quickly removed from the CPU to prevent it from becoming unstable or being damaged. Typically, a heat dissipation device is attached to an outer surface of the CPU to absorb heat from the CPU. The heat absorbed by the heat dissipation device is then dissipated to ambient air.  
         [0003]     Conventionally, a heat dissipation device comprises a solid metal base attached on the CPU, and a plurality of fins arranged on the base. The base is intimately attached on the CPU thereby absorbing the heat generated by the CPU. Most of the heat accumulated at the base is transferred firstly to the fins and then dissipated from the fins. However, the electronics technology continues to advance, and increasing amounts of heat are being generated by powerful state-of-the-art CPUs. Many conventional heat dissipation devices are no longer able to efficiently remove heat from these CPUs.  
         [0004]     In order to overcome the above set out disadvantages of the heat dissipation device, one type of heat dissipation device used for the electronic device includes a heat pipe for transferring heat from a position to another position of the heat dissipation device. A heat pipe is a vacuum-sealed pipe that is filled with a phase changeable fluid, usually being a liquid, such as water, alcohol, acetone and so on, and has an inner wall thereof covered with a capillary configuration. As the electronic device heats up, a hot section usually called evaporating section of the heat pipe which is located close to the electronic device also heats up. The liquid in the evaporating section of the heat pipe evaporates and the resultant vapor reaches a cool section usually called condensing section of the heat pipe and condenses therein. Then the condensed liquid flows to the evaporating section along the capillary configuration of the heat pipe. This evaporating/condensing cycle repeats and since the heat pipe transfers heat so efficiently, the evaporating section is kept at or near the same temperature as the condensing section of the heat pipe. Correspondingly, heat-transfer capability of the heat dissipation device including such the heat pipe is improved greatly.  
         [0005]     For instance,  FIG. 7  illustrates a heat dissipation device incorporating two heat pipes  2 . The heat dissipation device further comprises a base  1  for contacting with an electronic device and a plurality of fins  3  arranged on the base  1 . The base  1  defines two parallel grooves  10  therein. The fins  3  cooperatively define two through holes therein. Each heat pipe  2  has a substantially straight evaporating section  21  received in one of the grooves  10  of the base  1 , a straight condensing section  22  substantially parallel to the evaporating section  21  received in one of the through holes of the fins  3 , and a connecting section  23  connecting the evaporating section  21  and the condensing section  22 . The heat generated by the electronic device is absorbed by the base  1 , and transferred from the base  1  to a low portion of the fins  3  and the evaporating sections  21  of the heat pipes  2 . Then the heat is transferred to an upper portion of the fins  3  by the fins  3  themselves and the heat pipes  2 , and finally dissipated by the fins  3  to ambient air. However, the evaporating section  21  of the heat pipe  2  is straight, which results that the thermally contacting area between the base  1  and the evaporating section  21  is considerably small. Consequently, the amount of the heat, which can be transmitted by the heat pipe  2  is limited, whereby the high heat-transfer capability of the heat pipe  2  is not fully utilized. Therefore, the heat dissipation efficiency of the heat dissipation device is not optimal and can not meet with the higher and higher heat dissipation demand of the electronic device.  
         [0006]     What is needed, therefore, is a heat dissipation device which achieves a great heat-transfer capability and a great heat dissipation capability.  
       SUMMARY OF INVENTION  
       [0007]     A heat dissipation device in accordance with a preferred embodiment of the present invention is for contacting with a heat generating electronic device to remove heat from the electronic device. The heat dissipation device comprises a base, a plurality of fins and at least one heat pipe thermally positioned on the base. The fins are arranged on a face of the base. The heat pipe comprises a coplanar bent first portion, a second portion and a connecting portion. The first portion of the at least one heat pipe is thermally positioned to the face of the base. The second portion of the at least one heat pipe is remote from the face of the base and substantially parallel to a plane where the first portion is on. The connecting portion of the at least one heat pipe projects beyond the base and connects the first portion and the second portion. The second portion thermally engages with the fins.  
         [0008]     Other advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]      FIG. 1  is an exploded, isometric view of a heat dissipation device in accordance with a preferred embodiment of the present invention;  
         [0010]      FIG. 2  is an inverted and partially assembled view of  FIG. 1 ;  
         [0011]      FIG. 3  is an assembled view of  FIG. 1 ;  
         [0012]      FIG. 4  is an exploded, isometric view of a heat dissipation device in accordance with an alternative embodiment of the present invention;  
         [0013]      FIG. 5  is an inverted and partially assembled view of  FIG. 4 ;  
         [0014]      FIG. 6  is an assembled view of  FIG. 4 ; and  
         [0015]      FIG. 7  is a partially exploded, isomeric view of a conventional heat dissipation device. 
     
    
     DETAILED DESCRIPTION  
       [0016]     Referring to  FIGS. 1-3 , a heat dissipation device of the preferred embodiment of the invention comprises a base  10 , a plurality of fins  30  arranged on the base  10  and two heat pipes  50  thermally contacting with the base  10 .  
         [0017]     The base  10  is a substantially rectangular metal plate having high thermal conductivity, and has a bottom face (not labeled) for contacting with an electronic device (not shown) and a top face (not labeled) opposite the bottom face. Two grooves  110  are defined in the top face of the base  10  for receiving the heat pipes  50  therein. Each groove  110  is substantially U-shaped, having a long portion  111  near a lateral side of the top face of the base  10 , a short portion  113  substantially parallel to the long portion  111  and located near a center of the top face of the base  10 , and a middle portion  115  between the long portion  111  and the short portion  113  and connecting the long portion  111  and the short portion  113 . A free end of the long portion  111  of each groove  110  extends through an edge of the base  10 . The two grooves  110  are juxtaposed in the base  10 , but orientations thereof are opposite, wherein, the short portion  113  of one groove  110  is located between the long portion  111  and the short portion  113  and neighboring the short portion  113  of the other groove  110 .  
         [0018]     Each of the fins  30  is substantially rectangular and made from a metal sheet. Each fin  30  comprises a body  310  and two flanges  320  perpendicularly extending from two opposite edges of the body  310 . The body  310  has two through holes (not labeled) defined therein. The fins  30  are assembled together with the flanges  320  of each fin  30  adjoining the body  310  of the adjacent fin  30 . The holes of the fins  30  corporately define two through channels  330  for receiving the heat pipes  50  therein.  
         [0019]     Each of the two heat pipes  50  comprises a bent first portion  510 , a second portion  520  and a connecting portion  530  connecting the first portion  510  and the second portion  520 . The connecting portion  530  extends perpendicularly from the bent first portion  510 , and the second portion  520  extends perpendicularly from the connecting portion  530 . A profile of the first portion  510  is identical to that of the groove  110  of the base  10 , substantially U-shaped, and comprises three coplanar sections: a long section  511 , a short section  513  substantially parallel to the long section  511 , and a middle section  515  connecting the long section  511  and the short section  513 . The connecting portion  530  extends substantially perpendicularly from an end of the long section  511  of the first portion  510 . The second portion  520  extends substantially perpendicularly from the connecting portion  530  and parallel to the long section  511  of the first portion  510 . A rounded corner is formed at each of joints of the sections  511 ,  513 ,  515  of the first portion  510  and the portions  510 ,  520 ,  530  of the heat pipe  50 .  
         [0020]     In assembly, the first portions  510  of the heat pipes  50  are positioned beneath the fins  30  and respectively received in the two grooves  110  of the base  10 , wherein, the long section  511 , the short section  513  and the middle section  515  are respectively received in the long portion  111 , the short portion  113  and the middle portion  115  of each groove  110 . Therefore, the two first portions  510  of the two heat pipes  50  are juxtaposed on the base  10 , but orientations thereof are opposite, wherein, the long sections  511  of the first portions  510  are positioned near the two opposite lateral sides of the top face of the base  10 , and the short sections  513  are positioned near the center of the top face of the base  10 . The short section  513  of one of the heat pipes  50  is positioned between the long section  511  and the short section  513  and neighboring the short section  513  of the other heat pipe  50 . The two connecting portions  530  of the heat pipes  50  project upwardly beyond the top face of the base  10  from the long sections  511  and are positioned at two opposite sides of the fins  30 , respectively. The second portions  520  of the heat pipes  50  extend in the through channels  330  of the fins  30  from opposite sides of the fins  30 , respectively. The second portions  520  thermally engage with the fins  30 .  
         [0021]     In use of the heat dissipation device of this embodiment of the invention, the base  10  absorbs heat from the electronic device, to which the base  10  is attached. The fins  30  absorb the heat accumulated on the base  10  and then dissipate the heat to ambient air. The first portions  510  of the heat pipes  50  absorb the heat accumulated on the base  10  and then deliver the heat to the second portions  520  via the connecting portions  530  of the heat pipes  50 . The heat in the second portions  50  is subsequently transferred to the fins  30  and dissipated.  
         [0022]     According to this preferred embodiment of the present invention, it can be understood that, the first portion  510  of the heat pipe  50  attached to the base  10  is bent to have a substantial U-shape, such that the base  10  and the heat pipe  50  have a larger thermal contacting area therebetween in comparison with the conventional heat dissipation device. Consequently, more heat can be rapidly delivered to the fins  30  through the heat pipes  50  to be dissipated to the ambient air. Thus, the heat-dissipating capability is improved greatly by the heat dissipation device in accordance with the present invention.  
         [0023]     Referring to  FIGS. 4-6 , a heat dissipation device of the alternative embodiment of the invention is shown. The heat dissipation device is similar to the heat dissipation device of the preferred embodiment of the invention. The difference therebetween is that the heat dissipation device further comprises a plate  70  thermally positioned on the fins  30 , thereby the fins  30  being sandwiched between the plate  70  and the base  10 . The plate  70  also has high heat conductivity and defines two spaced parallel grooves  710  in a bottom face thereof which thermally contacts the fins  30 . The second portions  520  of the heat pipes  50  are received in the grooves  710  of the plate  70 . The second portions  520  of the heat pipes  50  thermally contact the plate  70  and a top of the fins  30 . In use, the heat in the second portions  50  of the heat pipes  50  is simultaneously transferred to the plate  70  and the fins  30  to be dissipated to the ambient air.  
         [0024]     It is believed that the present invention and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.