Abstract:
A heat dissipation device includes a base for absorbing heat from a heat generating device and a first fin set disposed on the base. Two second fin sets are located on two sides of the first fin set and extend beyond the base. At least a heat pipe includes a first section thermally sandwiched between the base and the first fin set and extending totally within and thermally contacting with the two second fin sets, and a second section extending away from the base and thermally contacting the first fin set and the second fin set.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    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 heat pipes for improving heat dissipation efficiency of the heat dissipation device. 
         [0003]    2. Description of Related Art 
         [0004]    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. 
         [0005]    Conventionally, a heat dissipation device comprises a solid metal base attached to the CPU, and a plurality of fins arranged on the base. The base is intimately attached to the CPU thereby allowing it to absorb the heat generated by the CPU. Most of the heat accumulated at the base is transferred firstly to the fins and then dissipates away from the fins. However, as electronics technology continues to advance, increasing amounts of heat are being generated by powerful state-of-the-art CPUs. As a result, many conventional heat dissipation devices are no longer able to efficiently remove heat from these CPUs. 
         [0006]    In order to overcome the above problems, one type of heat dissipation device used with the electronic devices includes a heat pipe for transferring heat from one part to another part 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 or the like, and has an inner wall thereof covered with a capillary system. As the electronic device heats up, a hot section (usually called an 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 a condensing section) of the heat pipe and condenses therein. The condensed liquid then flows to the evaporating section along the capillary system 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. As a result, heat-transfer capability of the heat dissipation device including such a heat pipe is greatly improved. 
         [0007]    Typically, a heat dissipation device comprises a base, a plurality of fins located on the base and a heat pipe thermally connecting the base and the fins for transferring heat from the base to the fins. The heat pipe is U-shaped and comprises an evaporating section contacting the base, a condensing section parallel to the evaporating section and extending away from the base, and a connecting section connecting the evaporating section and the condensing section. The fins define a through channel receiving the condensing section therein. In use, the base absorbs heat generated by the electronic device. The evaporating section of the heat pipe is heated up and transfers the heat to the condensing section. Finally, via the condensing section of the heat pipe, the heat reaches the fins to be dissipated to ambient air. However, in this heat dissipation device, the great heat transfer capacity of the heat pipe cannot be fully utilized. 
         [0008]    What is needed, therefore, is a heat dissipation device which can achieve a greater heat dissipation capability. 
       SUMMARY OF THE INVENTION 
       [0009]    A heat dissipation device in accordance with a preferred embodiment of the present invention comprises a base for absorbing heat from a heat generating device and a first fin set disposed on the base. Two second fin sets are located at two sides of the first fin set and extend beyond the base. At least a heat pipe comprises a first section thermally sandwiched between the base and the first fin set and extending through and totally within the two second fin sets, and a second section extending away from the base and thermally contacting the first fin set and the second fin set. 
         [0010]    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 THE DRAWINGS 
         [0011]    Many aspects of the present apparatus 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 apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0012]      FIG. 1  is an exploded, isometric view of a heat dissipation device in accordance with a preferred embodiment of the present invention; 
           [0013]      FIG. 2  is an assembled view of the heat dissipation device of  FIG. 1 ; 
           [0014]      FIG. 3  is an assembled view of the heat dissipation device of  FIG. 1  viewed from a bottom aspect; and 
           [0015]      FIG. 4  is an assembled view of the heat dissipation device of  FIG. 1 , wherein a base of the heat dissipation device is removed. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Referring to  FIG. 1 , a heat dissipation device in accordance with a preferred embodiment of the invention comprises a base  40 , a first fin set  80  located on the base  40 , two second fin sets  90  located at two sides of the first fin set  80 , and a plurality of heat pipes  20  thermally connecting the first, second fin sets  80 ,  90  and the base  40 . 
         [0017]    The base  40  is made of metal having excellent heat conduction properties, such as copper, aluminum and the like. The base  40  is substantially T-shaped, and comprises a main portion  48 , a first fixing portion  46  and a second fixing portion  44  extending from two opposite sides of the main portion  48 . The first fixing portion  46  is longer than the main portion  48  and the second fixing portion  44 . The second fixing portion  44  has a length similar to that of the main portion  48 . The first, second portions  46 ,  44  and the main portion  48  have top faces (not labeled) coplanar with each other. The main portion  48  has a bottom face lower than that of the first, second fixing portions  46 ,  44  for contacting with an electronic device (not shown). The first, second fixing portions  46 ,  44  each define two fixing holes (not labeled) therein for fixing the heat dissipation device to a printed circuit board (not shown) on which the electronic device is mounted. The main portion  48  defines three parallel grooves  49  in the top face thereof for receiving the heat pipes  20  therein. The grooves  49  each have a semicircular cross section. 
         [0018]    The first fin set  80  is disposed on the top face of the base  40 , and comprises a plurality of first fins (not labeled) assembled together. Each of the first fins is made of a metal sheet with good heat dissipating properties. Each first fin is substantially L-shaped and comprises a first portion  84  located adjacent to the base  40  and a second portion  82  remote from the base  40 . The first portions  84  of the fin set  80  thermally contact the top face of the first, second fixing portions  46 ,  44  and the main portion  48  of the base  40 . The fixing holes of the first, second fixing portion  46 ,  44  are essentially uncovered by the first portions  84  of the first fin set. Each second portion  82  has a lateral side flush with a corresponding lateral side of the first portion  84 , and an opposite lateral side extending beyond the second fixing portion  44  of the base  40 . First and second flanges  87  perpendicularly extend from corresponding lower edge of the first portion  84  and upper edge of the second portion  82 . The first and second flanges  87  of the fins abut against the corresponding first portions  84  and the second portions  82  of the adjacent fins. The first portion  84  defines three grooves  88  in a bottom thereof corresponding to the three grooves  49  of the base  40 . The grooves  88  of the first portion  84  each have a semicircular cross section. Three channels  86  are each cooperatively defined by a plurality of through holes (not labeled) defined in the second portion  82  of each first fin, and extend through the first fin set  80  for receiving the heat pipes  20 . The three through holes of each second portion  82  of each first fin define a triangle in the second portion  82 . The three channels  86  are located at different heights and horizontal portions of the second portions  82  of the first fin set  80 . 
         [0019]    The two second fin sets  90  are located at two opposite sides of the first fin set  80 . Each second fin set  90  comprises a plurality of second fins (not labeled) assembled together. Each of the second fins is made of metal sheet with good heat dissipating properties. Each second fin is substantially L-shaped, and comprises a first dissipating portion  94  at a lower portion thereof and a second dissipating portion  92  at an upper portion thereof. Each second dissipating portion  92  has a lateral side flush with a corresponding lateral side of the first dissipating portion  94 , and an opposite lateral side extending beyond a corresponding opposite lateral side of the first dissipating portion  94 . First and second flanges  97  perpendicularly extend from corresponding lower edges of the first dissipating portion  94  and upper edge of the second dissipating portion  92 . The first and second flanges  97  of the second fins abut against the corresponding first dissipating portions  94  and the second dissipating portions  92  of the adjacent second fins. The first dissipating portion  94  defines three parallel channels  98  extending through the first dissipating portions  94  of the second fin set  90  and corresponding to the grooves  88  of first fin set  80  and the grooves  49  of the base  40 , for receiving the heat pipe  20  therein. The channels  98  each have a circular cross section. Corresponding to the channels  86  of the first fin set  80 , the second dissipating portions  92  of the second fin set  90  define three through channels  96  therein, for receiving the heat pipe  20  therein. The three channels  96  are located at different heights and horizontal portions of the second dissipating portions  92  of the second fin set  90 . The channels  96  each have a circular cross section. 
         [0020]    The heat pipes  20  are each substantially U-shaped, and comprise a first transfer section (evaporating section)  22 , a second transfer section (condensing section)  24  parallel to the first transfer section  22 , and a connecting section  26  connecting with the first and second transfer sections  22 ,  24 . A rounder corner is formed at each joint of the first transfer section  22 , the connecting section  26  and the second transfer section  24  of the heat pipe  20 . 
         [0021]    Middle portions (not labeled) of the first transfer sections  22  of the heat pipes  20  are soldered in the grooves  49  of the main portion  48  of the base  40  and the grooves  88  of the first fin set  80 . Side portions of the first transfer sections  22  are interferentially received in the channels  98  of the two second fin sets  90  and located totally within the fins of the second fin sets  90 . The second transfer sections  24  of the heat pipes  20  are interferentially received in the channels  86 ,  96  of the first fin set  80 , and the two second fin sets  90 . The connecting sections  26  of the heat pipes  20  are located outside one of the two second fin sets  90 . 
         [0022]    In use, the main portion  48  of the base  40  contacts the electronic device and absorbs heat from the electronic device. The first transfer sections  22  of the heat pipes  20  absorb the heat in the base  40 . Part of the heat in the first sections  22  of the heat pipes  20  is transferred to the first portions  84  of the first fin set  80  and the first dissipating portions  94  of the two second fin sets  90 , another part of the heat is transferred to the second transfer sections  24  via the connecting sections  26  of the heat pipes  20 . Then the heat in the second transfer sections  24  of the heat pipes  20  reaches different portions of the second portions  82  of the first fin set  80  and the second dissipating portions  92  of the two second fin sets  90 . The heat in the fins of the first and second fin sets  80 ,  90  is dissipated to the ambient air. 
         [0023]    According to the preferred embodiment of the present invention, the heat dissipation device has the two second fin sets  90  located at two sides of the first fin set  80 , and contacts the heat pipes  20  to absorb heat in the heat pipes  20 , therefore, the heat absorbed in the heat pipes  20  from the electronic device can be removed to the first and second fin sets  80 ,  90  rapidly, so that, the heat pipes  20  can be fully utilized to absorb heat from the electronic device. As a result, heat transfer and dissipation capacity of the heat dissipation device are improved. Furthermore, the side portions of the first sections  22  of the heat pipes  20  are located totally within the second fin sets  90 , whereby the first sections  22  can have a large contacting area with the second fin sets  90  so that the heat received by the first sections  22  can be quickly transmitted to the second fin sets  90 . 
         [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.