Abstract:
A heat dissipation device includes a seat and a base having a first face and a second face opposite to the first face and thermally contacting the seat. A plurality of fins extends from the first face of the base. Two heat pipes are thermally arranged on the second face of the base. Each of the two heat pipes is bent and has a section sandwiched between the base and the seat, and another section thereof stretching along the base from said section to a portion of the base in no attachment with the seat.

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 electronic device to prevent it from becoming unstable or being damaged. Typically, a heat dissipation device is attached to an outer surface of the electronic device to absorb heat from the electronic device. 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 electronic device, and a plurality of fins arranged on the base. The base is intimately attached on the electronic device thereby absorbing the heat generated by the electronic device. Most of the heat accumulated at the base is transferred to the fins and is then dissipated from the fins. However, electronics technology continues to advance, and increasing amounts of heat are being generated by powerful state-of-the-art electronic devices. Many conventional heat dissipation devices are no longer able to efficiently remove heat from these electronic devices.  
         [0004]     In order to overcome the disadvantages of the heat dissipation device set out above, 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. The 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 which is usually called the evaporating section of the heat pipe and 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, the heat-transfer capability of the heat dissipation device including the heat pipe is improved greatly.  
         [0005]     Typically, a heat dissipation device illustrated as follows is used. The heat dissipation device comprises a base for absorbing heat from a heat generating electronic device, a heat pipe thermally connected to the base, and a plurality of fins arranged on the base. Generally, the heat pipe is I-shaped. The base defines a groove substantially in the center thereof receiving the heat pipe therein. In use, the base is in contact with the electronic device and absorbs heat from the electronic device. The heat in the base is absorbed by the heat pipe, and the heat pipe transfers the heat from the center to other parts of the base. The heat in the base spreads to the fins to be dissipated to ambient air. However, the heat pipe is straight, which results in the thermally contacting area between the base and the heat pipe being relatively small. Consequently, the heat in the center of the base can not be transmitted to other parts of the base rapidly and evenly. The heat generated by the electronic device accumulates in the center of the base and the electronic device. Normal functions and abilities of the electronic device are adversely affected. Therefore, the heat dissipation device needs to be improved.  
         [0006]     What is needed, therefore, is a heat dissipation device which achieves a greater heat-transfer capability and a greater heat dissipation capability.  
       SUMMARY OF INVENTION  
       [0007]     A heat dissipation device in accordance with a preferred embodiment of the present invention comprises a seat for absorbing heat from a heat generating electronic device, and a base having a first face and a second face opposite to the first face and thermally contacting the seat. A plurality of fins integrally extends from the first face of the base. Two heat pipes are thermally arranged on the second face of the base. Each of the two heat pipes is bent and has a section sandwiched between the second face of base and the seat, and another section thereof stretching along the second surface of the base from said section to a portion of the base in no attachment with the seat.  
         [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 first embodiment of the present invention;  
         [0010]      FIG. 2  is an inverted view of  FIG. 1  but without a base;  
         [0011]      FIG. 3  is an inverted and assembled view of  FIG. 1 ;  
         [0012]      FIG. 4  is an inverted and partially assembled view of a heat dissipation device in accordance with a second embodiment of the present invention;  
         [0013]      FIG. 5  is an inverted and partially assembled view of a heat dissipation device in accordance with a third embodiment of the present invention; and  
         [0014]      FIG. 6  is an inverted and partially assembled view of a heat dissipation device in accordance with a fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Referring to  FIGS. 1 and 2 , a heat dissipation device according to a first embodiment of the present invention for dissipating heat generated by an electronic device (not shown) located on a printed circuit board (not shown) is shown. The heat dissipation device comprises a seat  10 , a heat sink  30  on the seat  10 , and two heat pipes  50  thermally contacting the seat  10  and the heat sink  30 .  
         [0016]     The seat  10  is a substantially rectangular metal plate having great thermal conductivity, and has a bottom face (not labeled) for contacting with the electronic device (not shown) and a top face (not labeled) opposite the bottom face. Two parallel grooves  110  each with semicircular cross section are defined in the top face of the seat  10  for receiving the heat pipes  50  therein.  
         [0017]     The heat sink  30  comprises a base  31  and a plurality of fins  33  on the base  31 . The base  31  is a substantially rectangular plate and comprises a top face having the fins  33  integrally extending therefrom and a bottom face having a protrusion  34  extending downwardly from a center portion thereof. The protrusion  34  has a bottom face thereof defining two substantially U-shaped grooves  310  therein. The two grooves  310  are juxtaposed in the bottom face of the base  31  but oriented oppositely to each other. Each groove  310  comprises a first section  311  and two parallel second sections  313  substantially perpendicularly extending from two ends of the first section  311 , respectively. The first sections  311  of the grooves  310  are located adjacent a center of the protrusion  34 . The second sections  313  of the grooves  310  are located adjacent two opposite lateral sides of the bottom face of the base  31 . The two first sections  311  of the two grooves  310  are parallel to each other. The corresponding second sections  313  of the two grooves  310  extend oppositely in the bottom face of the base  31 . A round corner is formed at each joint of the first section  311  and second sections  313  of each groove  310 .  
         [0018]     Each of the two heat pipes  50  is substantially U-shaped and is identical to the groove  310  of the base  31  in profile. Each heat pipe  50  comprises a first transferring section  510  and two substantially parallel second transferring sections  530  extending from two ends of the first transferring section  510 . A round corner is formed at each joint of the first and second transferring sections  510 ,  530  of each heat pipe  50 .  
         [0019]     Referring to  FIG. 3 , the top face of the seat  10  is thermally combined to the bottom face of the protrusion  34  of the heat sink  30 . Therefore, the grooves  110  of the seat  10  and the first sections  311  of the grooves  310  of the base  31  of the heat sink  30  corporately define two parallel channels (not labeled). The two heat pipes are juxtaposed in the base  31  of the heat sink  30 . The first transferring sections  510  of the two heat pipes  50  are accommodated in the two channels, respectively. The second transferring sections  530  of the two heat pipes  50  extend beyond the seat  10  and are received in the second sections  313  of the grooves  310  of the heat sink  30 , respectively. Therefore, the two heat pipes  50  are thermally combined to the heat sink  30  side by side but oppositely. The first transferring sections  510  of the two heat pipes  50  are positioned adjacent the center of the bottom face of the base  31  of the heat sink  30 . The corresponding second transferring sections  530  of the two heat pipes  50  extend oppositely and are positioned near the two opposite lateral sides of the base  31  of the heat sink  30 .  
         [0020]     In use, the bottom face of the seat  10  contacts the electronic device to absorb heat from the electronic device. The heat in the seat  10  is absorbed by the first transferring sections  510  of the heat pipes  50  and the protrusion  34  of the heat sink  30 . And then, part of the heat in the heat pipes  50  and the protrusion  34  directly spreads upward to the fins  33 , and part of the heat is transferred outwardly to lateral portion of the base  31  of the heat sink  30  via the second transferring sections  530  of the heat pipes  50 . Subsequently, the heat in the fins  33  is dissipated to ambient air.  
         [0021]     According to the first embodiment of the present invention, the heat pipes  50  combined to the bottom of the base  31  of the heat sink  30  are curved to form a U-shape; therefore, the heat pipes  50  and the base  30  have a larger thermal contacting area therebetween; the heat in the center of the base  31  can be transferred to lateral portions of the base  31  rapidly via the second transferring sections of the heat pipes  50  in comparison with the conventional heat dissipation device; therefore, the heat generated by the electronic device is evenly distributed to the base  31 , to thereby be dissipated by the fins  33  rapidly. Thus, the heat-dissipating capability of the present invention is improved greatly.  
         [0022]     Referring to  FIG. 4 , a heat dissipation device in accordance with a second embodiment of the present invention is shown. The heat dissipation device is similar to the heat dissipation device of the first embodiment, but the main difference is that each of two heat pipes  50   a  has one of two second transferring sections  530   a  thereof located adjacent to a center of a bottom face of a base  31   a  of the heat sink  30 , the other of the two second transferring sections  530   a  located adjacent to lateral sides of the base  31   a  of the heat sink  30 . Two first transferring sections  510   a  of the two heat pipes  50  are substantially parallel to each other and are located adjacent to two opposite lateral sides of the base  31   a.  The second transferring sections  530   a  of the two heat pipes  50   a  are parallel to each other. The base  31   a  of the heat sink  30  defines grooves  310   a  accommodating the heat pipes  50   a  therein.  
         [0023]     Referring to  FIG. 5 , a heat dissipation device in accordance with a third embodiment of the present invention is shown. The heat dissipation device is similar to the heat dissipation device of the second embodiment, but the main difference is that one of two heat pipes  50   b  of the heat dissipation device has one second transferring section  530   b  located between two second transferring sections  530   b  of the other heat pipe  50   b.  A base  31   b  of the heat sink  30  defines grooves  310   b  accommodating the heat pipes  50   b  therein.  
         [0024]     Referring to  FIG. 6 , a heat dissipation device in accordance with a forth embodiment of the present invention is shown. The heat dissipation device is similar to the heat dissipation device of the third embodiment, but the main difference is that two heat pipes  50   c  of the heat dissipation device are substantially rectangular without being closed up. Each heat pipe  50   c  comprises four transferring sections  510   c.  Each heat pipe  50   c  has one transferring section  510   c  positioned adjacent a center of a base  31   c,  and other three transferring sections  510   c  positioned adjacent three lateral sides of the base  31   c  of the heat sink  30 . The transferring section  510   c  adjacent the center of the base  31   c  of one heat pipe  50   c  is disposed among the four transferring sections  510   c  of the other heat pipe  50   c.  Therefore, the two heat pipes  50   c  are located in the base  31   c  taking the format crossing loops.  
         [0025]     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.