Abstract:
An enclosure such as a notebook computer chassis in which the thermo-siphon devices are embedded in the skin of the enclosure is disclosed. The thermo-siphon devices include heat pipes. The thermo-siphon devices are use to absorb the heat dissipated by a heat source and dissipate it at a remote location.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    In electronic as well as non-electronic devices, enclosures are commonly used to house device components. These enclosures perform several functions including providing structural support to the device components, preventing the enclosed components from overheating, and vibration dampening. The enclosures are also referred to as housings. One example of an enclosure for an electronic device is a computer chassis. Typically, a computer includes a chassis that is generally a metallic frame. The chassis typically houses circuit boards, power supplies and wiring. The chassis typically includes four sidewalls and top and bottom elements. The sidewalls and the top and bottom elements are also referred to as chassis walls. Generally, at least one of the chassis walls comprises a removable cover such that the chassis components are easily accessible for replacement and repair purposes. The chassis walls are typically thick and rugged such that they provide a robust structural support for the enclosed components. The chassis walls are collectively referred to as the chassis skin.  
           [0002]    The skin often encloses device components that can malfunction and cause device failure when they overheat. Some device components dissipate heat during their operation. They are referred to as heat sources. An example of the heat source includes the integrated chips that comprise the circuit boards installed in the computer chassis. The heat generated by the heat sources can damage not only the heat sources themselves but also the other components enclosed by the skin. To avoid device failure, therefore, the heat in the interior of the enclosure must be effectively managed. A common heat management technique includes designing a well-ventilated enclosure such that the heat can dissipate to the exterior of the enclosure. Another technique includes fabricating the enclosure from materials with high thermal conductivity. Still another technique includes installing a cooling fan inside the enclosure. Yet another effective heat management technique includes using a thermo-siphon device to absorb the heat from the interior of the enclosure and transfer it to a heat sink. The heat sink can include the air to the exterior of the enclosure or a cooler portion of the chassis away from the heat source. A well-known thermo-siphon device is the heat pipe.  
           [0003]    A disadvantage of installing thermo-siphon devices in the interior of the enclosure is that they require additional space and thus increase the size of the enclosure. In the industries such as the notebook computer industry, the consumers are ever demanding a smaller and lighter chassis. The thermo-siphon devices are effective heat management tools and it is desirable to use them. There is a need in the art, therefore, for an enclosure design that houses the thermo-siphon devices without increasing the enclosure size.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which:  
         [0005]    [0005]FIG. 1 illustrates a front cross sectional view of the computer chassis of the prior art.  
         [0006]    [0006]FIG. 2 illustrates a front cross sectional view of one embodiment of the computer chassis that comprises the thermo-siphon device embedded in the skin of the chassis.  
         [0007]    [0007]FIG. 3 illustrates a front cross sectional view of another embodiment of the computer chassis that comprises the thermo-siphon device embedded in the skin of the chassis.  
         [0008]    [0008]FIG. 4 illustrates a top cross sectional view of the computer chassis of FIG. 3.  
     
    
     DETAILED DESCRIPTION  
       [0009]    The present invention discloses an enclosure in which the thermo-siphon devices are embedded in the skin of the enclosure. In the ensuing description, a computer chassis is disclosed by way of example. It will be evident, however, that the present invention can relate to any electronic or non-electronic device enclosure that houses thermo-siphon devices.  
         [0010]    [0010]FIG. 1 illustrates a front cross sectional view of one embodiment of the computer chassis of the prior art. A computer chassis  100  is shown having a top element  104 , a bottom element  108 , and sidewalls  112  and  116 . The top and bottom elements  104  and  108 , and the sidewalls  112  and  116  collectively form the skin  120 . The interior  124  of the chassis  100  is defined as the space enclosed by the skin  120 . The inner wall  130  of the skin is exposed to the interior  124  and the outer wall  132  is exposed to the exterior  136  of the chassis  100 . The shortest distance between the inner wall  130  and the outer wall  132  constitutes the skin thickness. Typically, the space between the walls  130  and  132  is filled with a metallic material such that it provides for a robust skin  120  that can provide a strong structural support to the chassis  100 . The skin can also be fabricated from non-metals that have low thermal conductivities.  
         [0011]    The interior  124  of the chassis has a thermo-siphon device  128 , for example, a heat pipe, and a heat source  140  installed therein. An example of the heat source  140  is an integrated circuit (IC) chip. The chip  140  is embedded on the circuit board  144  and faces the top element  104  such that the heat flux  148  dissipated by the chip  140  flows towards the top element  104 . It is appreciated that FIG. 1 illustrates exemplary chassis geometry and other chassis  100  geometries are feasible. For example, chassis  100  geometries wherein the chip  140  is positioned such that it faces one of the sidewalls  112  or  116 , or the bottom element  108 , are contemplated. It is also contemplated that although the newly generated heat flux  148  will initially thrust towards the top element  104 , the heat flux  148  can eventually spread in infinite direction.  
         [0012]    The thermo-siphon device  128  serves to transport the heat away from the chip  140  such that the chip  140  and the other components of the circuit board do not overheat. In one embodiment, the thermo-siphon device  128  is a heat pipe. The heat pipes  128  are well known in the art as self-contained heat-transfer devices. In one embodiment, the heat pipes transport thermal energy by vaporizing a liquid inside one end near a heat source and re-condensing it at the other end. The heat pipes are depressurized and sealed. One advantage of the heat pipes is that they have low temperature drops across their lengths. The internal geometry of the heat pipe typically consists of a hollow tube, an annulus wicking structure, and a working fluid. The heat is conducted through the heat pipe walls by means of conduction heat transfer.  
         [0013]    The vaporizing end  152  of the heat pipe  128  is positioned intelligently near the heat source  140  such that maximum amount of heat flux  140  is absorbed by the vaporizing end  152 . The re-condensing end  156  releases the heat flux  148  absorbed by the vaporizing end  152 . The re-condensing end  156  is intelligently positioned near the ventilation cavity  160  such that the heat flux  148  released by the re-condensing end  156  can be dissipated into the air to the exterior  136  of the chassis  100 . The fan  164  facilitates the dissipation of the heat flux  148  to the exterior  136 .  
         [0014]    The heat pipe  128  is only one example of the thermo-siphon device  128 . Another example of the thermo-siphon device  128  is a strip of a high efficiency conduit material. The thermo-siphon device  128  is typically fabricated from materials that have good thermal conductivity including metals such as copper and non-metals.  
         [0015]    The shortest distance between the outer wall  132  of the top element  104  and the outer wall  132  of the bottom element  108  is referred to as the chassis height  168 . It is evident from FIG. 1 that installing the thermo-siphon device in the interior  124  of the chassis  100  adds to the chassis height  168 . This is a disadvantage of the computer chassis  100  of the prior art.  
         [0016]    [0016]FIG. 2 illustrates a front cross sectional view of one embodiment of the computer chassis that comprises the thermo-siphon device embedded in the skin of the chassis. The thermo-siphon device  228  is shown sandwiched between the inner wall  230  and the outer wall  232  of the skin  220 . In one embodiment, the thermo-siphon device  228  is embedded in the top element  204 . In another embodiment, as illustrated in FIG. 3, the thermo-siphon device  328  is embedded in the bottom element  308 . It is contemplated that in other embodiments, the thermo-siphon device  228  can be embedded is the sidewalls  212  and  216 . In one embodiment, the thermo-siphon device  228  is tubular in shape. In another embodiment, the thermo-siphon device  228  has a flattened geometry. In one embodiment, the thermo-siphon device  228  is a heat pipe. In another embodiment, the thermo-siphon device  228  is a strip of high efficiency conduit material. In one embodiment, the heat pipe  228  is a tubular heat pipe. In another embodiment, the heat pipe  228  is a flattened heat pipe. In one embodiment, the thermo-siphon device  228  has a linear geometry. In another embodiment, as illustrated in FIG. 4, the thermo-siphon device  228  has a curved geometry.  
         [0017]    In one embodiment, the thermo-siphon device  228  is an integral part of the skin  120  wherein the thermo-siphon device  228  is embedded in the skin  220  during the fabrication process of the skin  220 . Such an embodiment makes the function of heat removal an integral part of the skin  220 . The prior art, as illustrated in FIG. 1, separates the enclosure function of the skin  220  from the heat removal function. The space occupied by the thermo-siphon device  228  is filled with skin material such as metallic material in the prior art. In one embodiment, a cavity of the size of the thermo-siphon device  228  is created in the skin  220  during the skin fabrication process such that the thermo-siphon device can be secured in the cavity. In one embodiment, the skin cavity is created through a material removal process. In another embodiment, the skin cavity is created during the injection molding operation to fabricate the skin  220 .  
         [0018]    In one embodiment, the thermo-siphon device  228  is not an integral part of the skin  220  and the thermo-siphon device  228  can be inserted and removed from the skin cavity by accessing the interior  224  of the chassis  200 . In one embodiment, the top element  204  that contains the cavity is a removable cover such that the thermo-siphon device  228  can be inserted and removed from the cavity by removing the top element  204 .  
         [0019]    In one embodiment, the inner wall  230  of the skin  220  does not cover the vaporizing end  252  of the thermo-siphon device  228 , thereby exposing the vaporizing end  240  to the interior  224  of the chassis  200 . In one embodiment, neither skin wall  230  or  232  covers the re-condensing end  256 , thereby exposing the re-condensing end  256  to the fan  264  and the ventilation cavity. It is contemplated that in one embodiment, the chassis  200  does not include a fan. In one embodiment, the inner wall  230  does not cover any part of thermo-siphon device  228 , thereby exposing the full length of the thermo-siphon device  228  to the interior  224  of the chassis  200 . The thermo-siphon device  228  can be secured into the cavity through various means such as, for example, support from the walls  230  and  232 , thermal epoxy, and interference fit with the cavity walls.  
         [0020]    In one embodiment, thermo-siphon device  228  extends through the skin cavity (not shown) in the sidewall  216  such that the re-condensing end  256  is positioned to the exterior  236  of the chassis  200 . In one embodiment, the thermo-siphon device  228  can be manually inserted into and removed from the skin cavity through the sidewall cavity.  
         [0021]    In one embodiment, a metallic plate  272  interfaces the heat source with the vaporizing end  252  of the thermo-siphon device  228 . The metallic plate  272  increases the surface area from which the heat flux  248  can be absorbed by the vaporizing end  252 . In one embodiment, the metallic plate  272  is a copper plate. In one embodiment, the copper plate  272  is attached to the vaporizing end  252  through means such as crimping, soldering and thermal epoxy. Intimate contact between the plate  272  and the vaporizing end  252  is desirable because the vaporization end&#39;s heat absorption efficiency is a function of the proximity between the heat source  240 , the plate  272  and the vaporization end  252 .  
         [0022]    [0022]FIG. 4 illustrates a top cross sectional view of the computer chassis of FIG. 3. Two non-linear thermo-siphon devices  428  are shown embedded between the inner wall  430  and the outer wall  232  (hidden underneath the inner wall  430 ). Three metallic plates  472  are shown attached to the thermo-siphon devices  428 . In one embodiment, the vaporizing ends  252  of the two thermo-siphon devices  428  are attached to the same metallic plate  472  to enhance the pace and quantity of the absorption of the heat flux  248  dissipated by the heat source  240 . In another embodiment, the re-condensing ends of the two thermo-siphon devices  428  are attached to the same metallic plate  472  to enhance the pace and quantity of the dissipation of the heat flux  248  to the heat sink.  
         [0023]    It is evident from the chassis heights  168  and  268  of FIGS. 1 &amp; 2 respectively that embedding the thermo-siphon device  228  into the skin  220  of the chassis  200  instead of installing it in the interior  224  is advantageous because it reduces the additional space requirement to install the thermo-siphon device  228  in the interior  224 . It is contemplated that the thermo-siphon device  228  can be embedded in a variety of enclosures that house the thermo-siphon device  228 .  
         [0024]    In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.