Abstract:
Described is a device which includes a housing, a chimney and a heat dissipation element. The housing includes at least one heat generating electric component mounted within an interior space thereof. The chimney extends from a proximal end surrounding a space adjacent to the at least one component through an opening in the housing to a distal end outside the housing. The heat dissipation element is attached to the distal end of the chimney and separated from the housing so that heat from the at least one component travels through the chimney to the heat dissipation element from which it is dissipated.

Description:
BACKGROUND INFORMATION 
   Thermal performance in a small electronics device is becoming increasingly challenging. Increasing CPU processing speeds, greater radio performance, and integrated power-over-ethernet (“POE”) add significant thermal burdens to such a device. 
   In a conventional electronic device (e.g., one which has a relatively slow processor and a minimal radio performance), a cooling off process is generally managed by utilizing a venting system in a housing. Warm air simply escapes the warm device through the venting system, while cooler outside air enters the device to replace the exiting warmed air. Due to restrictions in air flow and limitations on installations and placements of such a device, this process remains useful for minimal heat loads and light performance applications. 
   As performance increased in an electronics device, a venting system is replaced or augmented by a metal enclosure. Some metal enclosures are designed to dissipate heat. For example, the metal enclosure may function as a heat sink and draw point heat off a device through conduction and spread the heat loads into an installed environment by both convective and radiative processes. However, such a device generally recycle a percentage of heat back in to the enclosure and radiative heating of the electronics by the metal inside is not prevented. 
   SUMMARY OF INVENTION 
   The present invention relates to a device which includes a housing, a chimney and a heat dissipation element. The housing includes at least one heat generating electric component mounted within an interior space thereof. The chimney extends from a proximal end surrounding a space adjacent to the at least one component through an opening in the housing to a distal end outside the housing. The heat dissipation element is attached to the distal end of the chimney and separated from the housing so that heat from the at least one component travels through the chimney to the heat dissipation element from which it is dissipated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an exemplary embodiment of a device according to the present invention. 
       FIG. 2  shows another exemplary embodiment of the device according to the present invention. 
       FIG. 3A  shows a cross-sectional view of yet another exemplary embodiment of the device according to the present invention. 
       FIG. 3B  shows a cross-sectional view of yet another exemplary embodiment of the device according to the present invention. 
       FIG. 3C  shows a cross-sectional view of yet another exemplary embodiment of the device according to the present invention. 
       FIG. 4  shows a method for dissipating heat in the device according to the present invention. 
   

   DETAILED DESCRIPTION 
   The present invention relates to a device which includes an external heat sink arrangement. For example, the present invention may be particularly useful for cooling small electronic devices. 
     FIG. 1  shows an exemplary embodiment of a device  100  according to the present invention. The device  100  may be, for example, a wireless portable, an access point, a router, etc. 
   The device  100  includes a housing  102 . Certain electronic components of the device  100  may be stored within the housing  102 . The housing  102  may be formed of a plastic material (e.g., injection molded or vacuum formed plastic). Housing  102  may also have a vent  155  on one or more sides. The housing  102  preferably has a high resistance to thermal conductivity. As one of ordinary skill in the art will therefore understand, the housing  102  may block radiative and convective recycled heat from reaching the electronic components. 
   The device  100  also includes at least one heat sink arrangement  150 . The heat sink  150  includes at least one chimney  152 . Those skilled in the art would understand that the chimney may have any desirable shape such a cylindrical shape, a rectangular shape, a square shape, etc. The chimney  152  may extend through an opening  151  in the housing  102 . For example, the opening  151  may be a sized opening to accommodate exterior dimensions of the chimney  152 . The chimney  152  is preferably manufactured using a thermally conductive material (e.g., a metal). The heat sink  150  includes a dissipation element  154  having at least one fin  156 . 
     FIG. 2  shows another exemplary embodiment of a device  200  according to the present invention. The device  200  may be an electronic device such as a wireless device. The device  200  includes a housing  202  and a circuit board  204  (e.g., a printed circuit board or “PCB”) stored in the housing  202 . The circuit board  204  may be of any shape, size, or design (e.g., form factor) known to those of skill in the art. The circuit board  204  may include any number and variety of circuit components (e.g., processors, memory, etc (not shown)). The circuit components may attach on either side of the circuit board  204  (e.g., top or bottom). 
   In the exemplary embodiment, the circuit board  204  includes a component  206 . The component  206  may be, for example, a radio component, such as a PCI (“Peripheral Component Interconnect”) radio card. For example, the component  206  may be a radio component for wireless networking (e.g., Wi-Fi compatible). As one of ordinary skill in the art will understand, the component  206  may generate heat while the device  200  is in use. 
   As described above, the device  200  includes at least one heat sink  250 . The heat sink  250  includes a dissipation element  252  which has one or more fin  256  and a chimney  254 . The chimney  254  of the heat sink  250  is preferably manufactured of a thermally conductive material (e.g., a metal). In the exemplary embodiment, the chimney  254  includes at least two sides being substantially normal the circuit board  204  (e.g., to reduce the viewing angle relevant to radiative heating). The chimney  254  may have a hollow or a solid construction. In the case of the hollow chimney, a highly thermally conductive material (e.g., an embedded copper metal) or some electrical contrivance  311  (e.g., to augment heat flow through the hollow chimney) may be incorporated within the hollow chimney. 
   The chimney  254  may be in close proximity or direct contact (e.g., at a proximal end) with the component  206 . The chimney  254  is preferably substantially perpendicular to the component  206 . As one of ordinary skill in the art will understand, the heat sink  250  may draw point heat from the component  206  (e.g., a source load) via conduction through the chimney  254 , into the dissipation element  252 . The heat or heat load from the component  206  may be dissipated (e.g., via convection) into the environment from the fins  256 . 
     FIG. 3A  shows a cross-sectional view of another exemplary embodiment of a device  300   a  according to the present invention. The device  300   a  includes a housing  302   a  (e.g., a plastic housing) enclosing, for example, a circuit board  304   a . The circuit board  304   a  includes at least one component  306   a.    
   The device  300   a  includes at least one heat sink  350   a  according to the present invention. The heat sink  350   a  includes a dissipation element  352   a , at least one chimney  354   a , and fins  356   a . The chimney  354   a  is preferably substantially perpendicular to the component  306   a . A proximal end of the chimney  354   a  may be in close proximity or direct contact with the component  306   a . The chimney  354   a  passes through an opening  310   a  in the housing  302   a  to allow the heat sink  350   a  to draw point heat off the component  306   a  (e.g., in a direction A). The heat is transferred, via the chimney  354   a , to the dissipation element  352   a  and/or the fins  356   a  and dissipated into the environment (e.g., in directions B). 
   The exemplary embodiment of the device  300   a  may also include a transfer layer  308   a . The transfer layer  308   a  may have, for example, a Thermal Transfer Material (“TTM”). As one of ordinary skill in the art will understand, the transfer layer  308   a  may eliminate any air gap between the component  306   a  and the heat sink  350   a . Heat from the component  306   a  may be conducted through the transfer layer  308   a  to the chimney  354   a.    
   As shown in  FIG. 3A , the dissipation element  352   a  is preferably not in contact with the housing  302   a . The device  300   a  may include an external air insulator region  372   a  which is an open space located between the dissipation element  352   a  and a top portion of the housing  302   a . The external air insulator region  372   a  is open on all sides to permit air flow. As one of ordinary skill in the art will understand, the external air insulator region  372   a  may be useful for ensuring that a substantial portion of heat is not recycled between the dissipation element  352   a  and the housing  302   a . In addition, air flow through the external air insulator region  372   a  allows for convective venting of the recycled heat from concentrating on the housing  302   a.    
   The device  300   a  according to the present invention may further include an internal air insulator region  370   a . The internal air insulator region  370   a  includes space between the component  308   a  and inner portion of the housing  302   a . The internal air insulator region  370   a  may prevent heat collected in the housing  302   a  from being passed to internal components (e.g., the circuit board  304   a  and components). The internal air insulator region  370   a  may also provide for protection from heat transferred between internal electronics and/or components (e.g., the components  306   a ) of the device  300   a . In some exemplary embodiments, the housing  302   a  includes a vent on one or more sides. The vents may allow warm insulating air to escape and cooler insulating air to enter from the environment. 
     FIGS. 3B and 3C  show further exemplary embodiments of the present invention. The device  300   b  shown in  FIG. 3B  is substantially similar to the device  300   a . However, the device  300   b  includes an additional heat sink  350   b  to dissipate heat off another component  306   b . As one of ordinary skill in the art will understand, devices  300   b  according to the present invention may include any number of components  306   b . Each component  306   b  may have a corresponding heat sink  350   b  and chimney  354   b.    
   Another exemplary embodiment of the device  300   c  is shown in  FIG. 3C . The device  300   c  is substantially similar to the devices  300   a . However, the device  300   c  includes an additional chimney  354   c  to dissipate heat off another component  306   c . As discussed above, each component  306   c  of the device  300   c  may include a corresponding chimney  354   c . In this exemplary embodiment, two or more chimneys  354   c  may transfer heat to the same dissipation element  352   c.    
     FIG. 4  shows a method of dissipating heat in a device according to the present invention. In step  401 , heat is generated by at least one component within a housing of the device. In step  403 , the heat is dissipated from the component via a chimney which may be in direct or substantially close contact with the component. In step  405 , the heat is transferred along the chimney to a dissipation element located outside of the housing of the device. In step  407 , the heat is then dissipated to the environment from the dissipation element via convection and radiation. 
   The described embodiments of the present invention may provide for improved thermal performance in small electronic and wireless devices, while retaining the use of natural convection and radiative cooling. The improved thermal performance is accomplished via a highly efficient thermal path to move heat loads from a point of creation to the environment. The present invention is a light weight and low cost cooling solution using a minimal amount of metal material. The present invention also provides sufficient technology head room to permit substantial growth for at least five years. 
   While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.