Patent Abstract:
A toroidally shaped LPE with a plurality of microtubes extending through the LPE is disclosed. The LPEs are placed into thermal connection with heat producing components. A heat transfer fluid is contained in the microtubes of the LPEs and removes the heat from the heat producing components. This Abstract is provided to comply with rules requiring an Abstract that allows a searcher or other reader to quickly ascertain subject matter of the technical disclosure. This Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72( b )

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from, and incorporates by reference for any purpose the entire disclosure of U.S. Provisional Application Ser. No. 60/463,961, filed Apr. 18, 2003. This application is a Continuation-in-Part of, and incorporates by reference for any purpose the entire disclosure of U.S. patent application Ser. No. 09/328,183 filed Jun. 8, 1999 now U.S. Pat. No. 6,935,409 which claims benefit of U.S. Provisional Application Ser. No. 60/088,428 filed Jun. 8, 1998. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the present invention pertain to a cooling apparatus, and more particularly, but not by way of limitation, to cooling systems incorporating toroidally shaped, low-profile extrusions (LPEs). 
   2. History of Related Art 
   As is explained in greater detail hereinbelow, LPE cooling devices are extremely useful in printed circuit board (PCB) level cooling of electronic components, and for use as heat exchangers in applications where space is limited and/or low weight is critical. 
   LPE refers to a heat exchange apparatus including an integral piece of metal having a series of micro extruded hollow tubes formed therein for containing a fluid. LPEs preferably have multi-void extruded tubes (micro-tubes) designed to operate under the pressures and temperatures required by modern environmentally safe refrigeration gases and to resist corrosion. Aspects of the LPE application to the present invention are set forth and shown in co-pending U.S. patent application Ser. No. 09/328,183 and Ser. No. 10/305,662 assigned to the assignee of the present invention and incorporated herein by reference. 
   LPEs can currently be manufactured with a profile, or height, as low as about 0.05 inches and with tubes of varying inner diameters. Of course, future advances may allow such low-profile extrusions to be manufactured with an even smaller profile. Such low-profile extrusions have been conventionally used in heat exchanger applications in the automotive industry, and are commercially available in strip form (having a generally rectangular geometry) or coil form (a continuous strip coiled for efficient transport). 
   An example of a low-profile extrusion is described in a brochure entitled “Thermalex, Inc.—Setting A Higher Standard in Aluminum Extrusions” (hereinafter the “Thermalex Brochure”). The Thermalex Brochure provides additional detail regarding the Thermalex LPEs and is incorporated herein by reference. 
   U.S. Pat. No. 5,342,189 to Inamura, et al, which is incorporated herein by reference, provides additional detail regarding an extrusion die for making such LPEs. The extrusion die is used for making multi-cavity flat aluminum tubes, which are used for small heat exchanger components, in automotive air-conditioners, condensers, and radiators. The insert die is composed of a male die section having a protrusion part and a female die section, having a die cavity, and is held detachably in a die holder. The male section is a roughly rectangular plate-shaped component, and has an integrally formed twist prevention region which is inserted into the receiver groove of the female section which is integrally formed on the female section. The protrusion part defines the cavity shape of the multi-cavity flat tube, and the female section has the die cavity of the required cross sectional shape to define the outer shape of the tube. 
   U.S. Pat. No. 5,353,639 to Brookins, et al, which is incorporated herein by reference, provides additional detail regarding a method and apparatus for sizing a plurality of micro-extruded tubes used in such LPEs. As described by the Brookins patent, a predetermined number of micro-extruded tubes are stacked on the base fence between the fixed side fence and the clamping fence. The internal webs of the tubes are aligned throughout the stack, perpendicular to the plane of the base fence. The clamping fence is moved toward the stack of tubes to prevent the stack from moving laterally. The die platen is moved toward the stack of tubes and the mating surface of the die platen is in mating engagement with a side surface of the uppermost tube in the stack. A predetermined amount of pressure is applied to the stack of tubes through the die platen. The pressure is applied equally across the entire side surface of the uppermost tube and is transmitted equally through all the tubes of the stack in the sizing die. 
   Other developments in cooling apparatus may be seen in U.S. Pat. No. 5,285,347 to Fox et al., which describes a hybrid cooling system for electrical components. A hybrid heat sink is specially adapted to transfer heat to two heat transfer fluids. The heat sink is incorporated into a cooling system in which some of the electronic components of an electronic device may be cooled by two heat transfer fluids and some electronic components may be cooled by one heat transfer fluid. The electronic components are mounted on a circuit board. In the Fox reference, one of the heat transfer fluids is air and one is a liquid. The hybrid heat sink is attached to electronic components that cannot be cooled to the normal operating range by the cooling air alone. The cooling air is caused to flow over the surface of the heat sink, removing some of the heat. In addition, the liquid heat transfer fluid is caused to flow through the heat sink, thereby removing additional heat. 
   In addition, U.S. Pat. No. 5,901,037 to Hamilton, et al. describes a system for closed loop liquid cooling for semiconductor RF amplifier modules. The system includes a combination of a plurality of elongated micro-channels connected between a pair of coolant manifolds for conducting liquid coolant beneath the transistors to dissipate the heat generated by the transistors. The system also includes a heat exchanger, a miniature circulating pump located on the module, and passive check valves having tapered passages for controlling the flow of coolant in the loop. The valve includes a truncated pyramid-shaped micro-channel valve having no moving parts and is fabricated so as to be a part of either the circulating pump assembly, the coolant manifold, or the micro-channels. 
   It has been shown that the use of low-profile heat pipes greatly improves the efficiency of the heat removal process, while making the cooling package lightweight and compact. It is shown in co-pending U.S. patent application Ser. No. 09/328,183, Ser. No. 10/328,438, Ser. No. 10/328,537, Ser. No. 10/335,373 and Ser. No. 10/345,475 that heat pipes of the unstacked variety provide superior performance in a low-profile, light weight package. 
   Embodiments of the present invention provide a cooling element utilizing a heat pipe with a toroidal shape. The toroidal shape allows the heat pipe to remove heat from a heat generating element while exhibiting a small footprint. The toroidal heat pipe is useful in environments having little space but requiring efficient heat removal. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a heat pipe cooling system and method of manufacture. More particularly, the present invention relates to a cooling system for removal of heat from at least one heat generating component. The system includes a low-profile extrusion having an inner and outer external surface and having a first end and a second end. The low-profile extrusion is curved upon itself such that the second end is disposed generally opposite the first end. The system also includes an interior spaced formed by the inner external surface of the curved low-profile extrusion. The low-profile extrusion has an external surface adapted for thermal connection to the at least one heat generating component. The system also includes a plurality of microtubes formed in the interior of the low-profile extrusion and adapted for containing a heat transfer fluid inside the microtubes, and a fin structure in thermal connection with the exterior surfaces of the extrusion. 
   In another aspect, the present invention relates to a method for cooling heat generating elements. The method comprises placing a generally toroidally-shaped heat pipe substantially near at least one of the heat generating elements, and drawing air across the generally toroidally-shaped heat pipe via a fan structure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the method and apparatus of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
       FIG. 1  is a schematic illustration of a low-profile extrusion heat exchange apparatus of an unstacked variety, shown as a circulation cooling apparatus for removal of heat from certain heat generating components; 
       FIGS. 2 and 3  are schematic illustrations of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as the heat pipe type cooling apparatus for removal of heat from certain heat generating components; 
       FIG. 4  is a schematic illustration of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as heat transfer component of a recirculatory system; 
       FIG. 5A  is a schematic illustration of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as a liquid to liquid manifold cooling apparatus; 
       FIG. 5B  is a schematic illustration of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as a liquid to air manifold cooling apparatus; 
       FIG. 5C  is a schematic illustration of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as an air to air manifold cooling apparatus; 
       FIG. 6  is a is a schematic illustration of a method and apparatus for manufacturing heat pipes according to an embodiment of the heat exchange apparatus of an unstacked variety; 
       FIG. 7  is a schematic illustration of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as heat pipe base/fin cooling apparatus; 
       FIG. 8  is a schematic illustration of another embodiment of the low-profile extrusion heat exchange apparatus of an unstacked variety, shown as a base/heat pipe fin cooling apparatus; 
       FIG. 9  is an illustration of one aspect of a stacked array of phase plane heat pipes; 
       FIG. 10  is a perspective view of an embodiment of a stacked array of phase plane heat pipes; 
       FIG. 11  is a side view of an embodiment of a stacked array of phase plane heat pipes; 
       FIG. 12  is an embodiment of a phase plane heat pipe incorporating fins and a fan; 
       FIG. 13  is an illustration of a laptop computer including the embodiment of the phase plane heat pipe incorporating fins and a fan as shown in  FIG. 12 ; 
       FIG. 14  is an illustration of a laptop computer including another embodiment the phase plane heat pipe incorporating fins and a fan as shown in  FIG. 12 ; 
       FIG. 15  is a front perspective view of a toroidally shaped heat pipe according to the principles of the present invention; 
       FIG. 16  is a side-elevational view of another embodiment of the toroidally shaped heat pipe of  FIG. 15  having a fin structure thermally connected to the top and bottom surfaces of the heat pipe; 
       FIGS. 17   a – 17   e  illustrate yet another embodiment of the toroidal heat pipe incorporating a fan and air flow for improved heat removal characteristics; 
       FIGS. 18   a  and  18   b  illustrate the toroidal heat pipe incorporating a clip for attaching the heat pipe to a heat generating element; and 
       FIGS. 19   a  and  19   b  illustrate the toroidal heat pipe incorporating springs for attaching said fins to the heat pipe and said heat pipe to a heat generating element. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Various aspects of the present invention are illustrated herein by example in  FIGS. 1–19   b  generally, and more particularly embodiments of the present invention are illustrated by  FIGS. 15–19   b . Various modifications may be made by a person of ordinary skill in the art.  FIGS. 1–14  illustrate utilization of low-profile extrusion apparatus of the unstacked and stacked variety. 
     FIG. 1  is a schematic illustration of a cooling apparatus  10  used for removing heat from certain heat generating components  12  mounted on a printed circuit board  14 . The printed circuit board  14  may be housed in a host electronic device (not shown) such as computer, a laptop or notebook computer, or other electronic equipment. Due to the ongoing miniaturization of such host electronic devices, the heat generating components  12  are often located in an area of the printed circuit board  14  and of the host electronic device where space is extremely limited, especially in the “z”, or height dimension. 
   The cooling apparatus  10  generally includes a conventional liquid-to-air heat exchanger  16 , an inlet tube  18 , a low-profile extrusion  20 , an outlet tube  22 , a conventional pump  24 , and tubing  26 . The low-profile extrusion  20  has a plurality of micro-tubes  21 , each micro-tube  21  having a micro-tube inlet  21   a  and a micro-tube outlet  21   b.    
   Micro-tubes  21  are formed by a plurality of longitudinal members. The longitudinal members may be vertical or may be offset from vertical. A preferred offset from vertical is between about 5° and 60°. More preferably, longitudinal members are offset from vertical by about 30°. Furthermore, longitudinal members may be provided with a capillary groove. The capillary groove may be positioned on an external surface or on the longitudinal members. Further, the capillary grooves may be provided in groups of one, two, three or more. 
   Referring again to  FIG. 1 , the extrusion  20  is preferably formed with a generally flat surface on its underside  20   a  for contacting heat generating components  12 , and may be formed with external fins on its top side  20   b  to maximize heat transfer, if space allows. It is notable that the micro-tubes  21  formed in the extrusion  20  may be of nearly any geometry and that shapes with flattened heat transfer surfaces are generally preferred, but tubes of any shape could be used with varying degrees of efficiency. As best illustrated in  FIGS. 7 and 8 , flat extrusions  20  with rectangular micro-tubes  21  are shown. Extrusion  20  is also preferably formed with at least one solid channel (not shown) for mounting to printed circuit board  14 . Conventional thermal interface material (not shown) is preferably provided between low-profile extrusion  20  and heat generating components  12 . 
   The micro-tube inlets  21   a  of the micro-tubes  21  in the extrusion  20  are interconnected in fluid communication, and to the inlet tube  18 , by an inlet endcap  28   a . Similarly, the micro-tube outlets  21   b  of the micro-tubes  21  in the extrusion  20  are interconnected in fluid communication, and to the outlet tube  22 , by an outlet endcap  28   b . Alternatively, micro-tube outlets  21   a  and/or  21  may be sealed by crimping the low-profile member  20 . Micro-tubes outlets  21   a  and/or  21   b  may be individually sealed or connected in fluid communication. The heat exchanger  16  may contain a fluid reservoir (not shown) for housing a heat transfer fluid such as water, glycol, alcohol, or other conventional refrigerants. In addition, a wick, such as a screen may be provided within one or all of micro-tubes  21 . The fluid from the heat exchanger  16  is circulated through the inlet tube  18 , the low-profile extrusion  20 , the outlet tube  22 , and the tubing  26  via the pump  24 . Alternatively, the entire cooling apparatus  10  may be evacuated and charged with fluid which is then circulated via the pump  24 . 
   During operation of the host electronic device, heat generated by heat generating components  12  is transferred from heat generating components  12  to an evaporator section of low-profile extrusion  20 , to the fluid circulating within low-profile extrusion  20 , and then to heat exchanger  16  from a condenser section of low-profile extrusion  20 . Heat exchanger  16  removes the heat from the fluid in a conventional manner. Preferably, an airflow  30  is passed over heat exchanger  16  to aid in such heat removal. Cooling apparatus  10  thus efficiently removes heat from a limited space, low-profile area within the host electronic device (the location of low-profile extrusion  20 ) to an area where it can be removed at a more convenient location and envelope (the location of heat exchanger  16 ). 
     FIGS. 2 and 3  are schematic illustrations of a cooling apparatus  40  used for removing heat from heat generating components  12  on printed circuit board  14 . Referring first to  FIG. 2 , cooling apparatus  40  generally includes a low-profile extrusion  42  manufactured as a heat pipe capable of phase change heat transfer. A preferred method of making a low-profile heat pipe extrusion  42  is described in greater detail hereinbelow. The low-profile heat pipe extrusion  42  is preferably formed with micro-tubes  41 , each micro-tube  41  having a conventional wick structure such as internal fins, grooved inner sidewalls, or metal screens, so as to maximize their heat transfer capability via capillary action. 
   To form a heat pipe, the micro-tubes  41  of the low-profile heat pipe extrusion  42  are evacuated and then charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants before sealing the ends  41   a  and  41   b  of the micro-tubes  41 . The ends may be sealed by crimping. By providing vertically offset longitudinal members, longitudinal members tend to lay over during crimping rather than buckling. Therefore, vertically offset members may be advantageous. As is known in the art, a heat pipe generally has an effective thermal conductivity of several multiples higher than that of a solid rod. Efficiency is increased due to the fact that the phase change heat transfer coefficients are high compared to the thermal conductivity of conventional materials. 
   The low-profile heat pipe extrusion  42  is preferably formed into an evaporator section or first portion  44  for contacting heat generating components  12  and a raised or condenser section second portion  46 . First portion  44  and second portion  46  are preferably substantially similar in construction to low-profile extrusion  20  of  FIG. 1 , except endcaps  28  are not required. First portion  44  acts as the evaporator section of the heat pipe, and second portion  46  acts as the condenser section of the heat pipe. 
   During operation of the host electronic device, heat generated by heat generating components  12  is transferred from heat generating components  12  to first portion  44 . Heat causes the liquid within the micro-tubes  41  in first portion  44  to change to vapor, consuming some of the generated heat. Because the vapor is less dense than the surrounding liquid, the vapor and associated heat rise into the micro-tubes  41  in second portion  46 . Of course, heated liquid may also be transferred from first portion  44  to second portion  46  via the capillary action of the wick structures of the micro-tubes. In second portion  46 , the vapor condenses into liquid onto the inner side walls of the micro extruded tubes  41 . The heat generated by the condensation reaction, as well as any heat transferred via capillary action of the wick structure, is then transferred to air flow  48 . Cooling apparatus  40  thus efficiently removes heat from a limited space, low-profile area within the host electronic device (the location of first portion  44 ) to an area where it can be removed at a more convenient location and envelope (the location of second portion  46 ). Of course, if low-profile heat pipe extrusion  42  is formed with internal wick structures, it is not necessary that second portion  46  be raised from, or higher than, first portion  44 . 
   Referring now to  FIG. 3 , low-profile heat pipe extrusion  42  is shown in operation with a conventional thermoelectric cooler (TEC)  50  in contact with one of the heat generating components  12 . A preferred TEC is sold by Marlow Industries, Inc. of Dallas, Tex. TEC  50  facilitates the heat transfer between the heat generating component  12  and first portion  44  of low-profile heat pipe extrusion  42 , and thus is preferred for use with heat generating components  12  that have high power densities. 
     FIG. 4  is a schematic illustration of a cooling apparatus  60  used for removing heat from a fluid  62 , such as water, glycol, alcohol, or other conventional refrigerants. Fluid  62  is then used to cool conventional heat generating components, such as heat generating components  12  of printed circuit board  14 . By way of example, cooling apparatus  60  may be used in place of conventional heat exchanger  16  in  FIG. 1 . 
   Cooling apparatus  60  generally includes a low-profile extrusion  64 , an inlet endcap  63   a , an inlet tube  66 , an outlet endcap (not shown), an outlet tube (not shown), thermoelectric coolers  52 , and conventional bonded fin heat sinks  68  and  70 . The low-profile extrusion  64  is preferably substantially similar in construction to low-profile extrusion  20  of  FIG. 1 , with a plurality of micro-tubes (not shown) having a micro-tube inlet and a micro-tube outlet (not shown). The micro-tube inlets of the micro-tubes in the extrusion  64  are interconnected in fluid communication, and to the inlet tube  66 , by the inlet endcap  63   a . Similarly, the micro-tube outlets of the micro-tubes in the extrusion  64  are interconnected in fluid communication, and to the outlet tube, by an outlet endcap. 
   The low-profile extrusion  64  preferably has generally flat bottom and top surfaces for contact with TECs  52 . The conventional bonded fin heat sink  68  is coupled to TECs  52  on the top surface of low-profile extrusion  64 , and the conventional bonded fin heat sink  70  is coupled to TECs  52  on the bottom surface of low-profile extrusion  64 . 
   In operation, the low-profile extrusion  64  serves as a manifold, and the TECs  52  remove heat from fluid  62  flowing through the micro-tubes of the low-profile extrusion  64 . Heat removed is transferred from TECs  52  to bonded fin heat sinks  68  and  70 , which dissipate the heat to atmosphere in a conventional manner. Preferably, airflows  72  and  74  pass over and through heat sinks  68  and  70  to facilitate such heat dissipation. 
   Low-profile extrusion  64  has a smaller size and mass than conventional heat exchanger manifolds. For example, a conventional manifold has a minimum profile, or height, in the “z” direction of about 0.75 inches, and low-profile extrusion  64  may have a profile as low as about 0.1 inches. The reduced mass of low-profile extrusion  64  is believed to produce a cooling apparatus  60  with a near zero time constant, increasing startup performance and temperature control. Therefore, cooling apparatus  60  is especially advantageous in applications involving lasers. The wavelength of a laser beam, and thus beam properties, is strongly influenced by temperature, and the tighter temperature control believed to be provided by cooling apparatus  60  is extremely beneficial. 
     FIGS. 5A ,  5 B, and  5 C are schematic illustrations of the cooling apparatus referenced in  FIGS. 2–4  incorporating a stacked heat pipe/TEC configuration.  FIG. 5A  shows a cooling apparatus  80  having a plurality of LPEs  64  and TECs  52  arranged in a serial fashion. A TEC  52  is disposed between, and is in contact with, each of the extrusions  64 . Only one low-profile extrusion  64  and one TEC  52  is numbered in  FIG. 5A  for clarity of illustration. Fluid  62  enters each extrusion  64  via inlet  66  and exits each extrusion  64  via an outlet  82 . In operation, TECs  52  remove heat from fluid  62  flowing through LPEs  64 . The removed heat is transferred to airflow  84  passing over cooling apparatus  80 . 
     FIG. 5B  shows a cooling apparatus  90  having a plurality of LPEs  64 , TECs  52 , and low-profile heat pipe extrusions  92  arranged in a serial fashion. More specifically, a TEC  52  is disposed between, and is in contact with, each low-profile extrusion  64  and low-profile heat pipe extrusion  92 . Only one low-profile extrusion  64 , one TEC  52 , and one low-profile heat pipe extrusion  92  are numbered in  FIG. 5B  for clarity of illustration. Each low-profile heat pipe extrusion  92  is preferably substantially similar in construction to low-profile heat pipe extrusion  42  of  FIG. 1 , excluding raised portion  46 . Fluid  62  enters each extrusion  64  via inlet  66  and exits each extrusion  64  via outlet  82 . In operation, each TEC  52  removes heat from fluid  62  flowing through an adjacent low-profile extrusion  64 . The removed heat is transferred to the evaporator portion  92   a  of the adjacent low-profile heat pipe extrusion  92 . The heat is then transferred to the condenser portion  92   b  of the low-profile heat pipe extrusion  92 , as is explained hereinabove in connection with low-profile heat pipe extrusion  42  of  FIGS. 2 and 3 . An airflow  84  passing over cooling apparatus  90  dissipates heat from each condenser portion  92   b  of each low-profile heat pipe extrusion  92 . 
     FIG. 5C  shows a cooling apparatus  100  having a plurality of TECs  52  and low-profile heat pipe extrusions  92  arranged in a serial fashion. More specifically, a TEC  52  is disposed between, and is in contact with, each low-profile heat pipe extrusion  92 , and the “free end” of adjacent low-profile heat pipe extrusions  92  extend in opposite directions. Only one TEC  52  and two low-profile heat pipe extrusions,  92 ′ and  92 ″, are numbered in  FIG. 5C  for clarity of illustration. In operation, a hot airflow  102  flows over each evaporator portion  92   a  of low-profile heat pipe extrusions  92 ′. The heat is transferred from evaporator portion  92   a  to condenser portion  92   b  of extrusion  92 ″, as is explained hereinabove in connection with low-profile heat pipe extrusion  42  of  FIGS. 2 and 3 . Condenser portion  92   b  of extrusion  92 ″ is in contact with TEC  52 . The TEC  52  removes heat from condenser portion  92   b  of extrusion  92 ″ and transfers it to evaporator portion  92   a  of low-profile heat pipe extrusion  92 ′. The heat is then transferred from evaporator portion  92   a  to condenser portion  92   b  of extrusion  92 ″. Cold airflow  104  passing over condenser portions  92   b  of each extrusion  92 ″ dissipates heat from cooling apparatus  100 . 
   Cooling apparatus  80 ,  90 , and  100  have the same applications and advantages of cooling apparatus  60  described hereinabove. As will be appreciated by one skilled in the art, cooling apparatus  60 ,  80 , and  90  may also be operated as heating apparatus by using thermoelectric coolers (TECs)  52  to heat, rather than to cool, a fluid. 
     FIG. 6  is a schematic illustration of a method and apparatus for manufacturing LPEs or heat pipes. As noted hereinabove, the preferred apparatus and method may be utilized to make LPEs of  FIGS. 1–4 ,  5 A,  5 B, and  5 C as well as the extrusions of  FIGS. 7–16 . However, the preferred apparatus and method may also be utilized to make extruded hollow tubes for other heat exchangers and heat pipes. 
   Apparatus  110  generally includes an oven  112  having an insulated housing. A vacuum station  114  and a fluid charging station  116  are in fluid communication with oven  112 . Alternatively, stations  114  and  116  may be separate from oven  112 . A coil  118  is disposed within a portion of oven  112  on a conventional automatic feed system. Coil  118  may be a coil of hollow tubing, a coil of low-profile extrusion, or a coil of other conventional extrusion having a series of extruded hollow tubes. Furthermore, coil  118  includes any material that can be formed and welded with any fluid fill. The material includes, but is not limited to aluminum, stainless steel, carbon steel, copper, and titanium alloys. An ultrasonic welder/sealer is also provided. One model of ultrasonic welder/sealer is the Ultraseal7 series sold by American Technology, Inc. of Shelton, Conn. A brochure entitled “Ultraseal7–20 20 kHz Portable Ultrasonic Metal Tube Sealer” (hereinafter the “Amtech Brochure”) provides additional information regarding the Ultraseal7 series of ultrasonic welder/sealers and is incorporated herein by reference. A preferred ultrasonic welder/sealer is the Stapla Ultrasonic gantry style seam welder. 
   In a conventional process, the first step is actually forming and cutting the heat exchanger, heat pipe, or extruded tubes into the desired configuration. Next, the preformed system is evacuated and charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants. The system is then sealed, completing the process. Conventional processes are expensive because they are labor intensive and require long setup times for different configurations of heat exchangers, heat pipes, or extruded tubes. 
   However, apparatus  110  may be used to efficiently and economically produce heat exchangers, heat pipes, and extruded tubes, including LPEs, according to the following preferred process. First, coil  118  is placed within a heat producing device such as oven  112  on the automatic feed system. Second, coil  118  is evacuated using vacuum station  114 . Preferably, coil  118  is pulled down to a vacuum of about 10 −7  torr for a period lasting approximately twenty four hours to many weeks depending on performance requirements. Third, coil  118  is charged with a known amount of fluid, such as water, glycol, alcohol, acetone or other refrigerants, using charging station  116 . Acetone is the preferred fluid. Alternatively, coil  118  may be evacuated and charged outside oven  112 . Fourth, oven  112  heats coil  118  until at least some of the fluid is in the vapor phase, and the vapor fills the interior of coil  118  evenly. Fifth, using the automatic feed system, the heated and charged coil  118  is reeled out. 
   Preferably the fluid exits the oven  112  at approximately 40° C. to 60° C. allowing enough thermal inertia to draw vapor into the extrusion external to the oven. A temperature sender container may be provided to ensure that the fluid exit temperature is maintained at a desired level. The coil is then processed by crimping, sealing, and cutting the coil  118  into desired lengths. The temperature difference between the oven  118  and the ambient air (or air-conditioned air) temperature condenses the charging fluid in each pipe before it is crimped. These temperatures and flows are used to control the individual heat pipe fills via a weight analysis. A computer and scale monitor the weight of each part and adjust the oven temperatures accordingly. 
   Subsequent steps include crimping, sealing, and cutting the coil  118 . A hydraulic press, pneumatic or mechanical means may be used for crimping. An ultrasonic welder/sealer, or another standard welding method such as laser electron beam, resistive, TIG, or MIG welding may be used during the sealing stage. Ultrasonic welding is the preferred process. 
   A plasma cutter, or other standard welding method mentioned herein may be used in the cutting stage. However, the plasma cutter is the preferred method. Finished product is collected within container  122 . Thus, heat exchangers, heat pipes, and extruded tubes, including LPEs, are formed while charged with fluid, significantly reducing the setup time and vacuum expense over conventional processes. 
   In addition, by separating the coil side of the process from the crimping, sealing, and welding process steps, the temperatures for the process steps can be adjusted so as to be in the fluid range for the working fluid. Thus, if a cryogenic heat pipe (charging fluid is typically a gas at normal room temperature) is to be manufactured, the temperature of the process steps would be adjusted such that the charging fluid is a liquid. In a similar manner, high temperature heat pipes, where the charging fluid is typically a solid at room temperatures, can be manufactured. 
   Referring now to  FIG. 7 , there is shown an illustration of another embodiment of a low-profile cooling system of an unstacked variety. A cooling apparatus  210  is used for removing heat from heat generating components  12  on a printed circuit board  14 . The cooling apparatus  210  includes a low-profile extrusion  220  manufactured as a heat pipe capable of phase change heat transfer. The low-profile heat pipe extrusion  220  is formed having a plurality of micro-tubes  223 , preferably having a conventional wick structure such as internal fins, grooved inner side walls, or metal screens, so as to maximize the heat transfer capability via capillary action. The micro-tubes  223  of the low-profile heat pipe extrusion  220  are evacuated and then charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants, before the ends of the micro-tubes are sealed. 
   Referring still to  FIG. 7 , the low-profile heat pipe extrusion  220  has a first surface  221  for engaging the heat generating components  12  and receiving heat from the heat generating components  12 . On a second surface  222  of the low-profile extrusion  220 , a conventional bonded fin heat sink  230  or a plurality of cooling fins are mounted to the low-profile extrusion  220 . Preferably, the micro-tubes  223  are disposed in a direction perpendicular to the fins  230  for transferring heat between each of the individual fins  230 . The heat transfer between the individual fins  230  promotes an even distribution of heat across each of the fins  230 . However, the micro-tubes  223  can be oriented for the transfer of heat along the length of the fins  230 . Additionally, in one embodiment, the micro-tubes  223  of the low-profile extrusion  220  are oriented for disbursing heat from the heat generating components  12  to areas of the low-profile extrusion  220  which are not in contact with the heat generating components  12 . 
   Still referring to  FIG. 7 , the use of the low-profile extrusion  220  for transferring heat in the cooling apparatus  210  increases the effective surface area that is transferring heat from the heat generating components to the cooling fins  230 . The resulting cooling apparatus is therefore smaller in size and lighter in weight for the same effective cooling attributes. In some embodiments, the low-profile cooling system of an unstacked variety can decrease the weight of an apparatus for cooling a heat generating component by as much as 50% over traditional fins mounted via a metal plate. 
   Referring now to  FIG. 8 , there is shown an illustration of another embodiment of a low-profile cooling system of an unstacked variety, showing a cooling apparatus  250  used for removing heat from heat generating components  12  on printed circuit board  14 . The cooling apparatus generally includes a base  260  and a plurality of low-profile extrusion fins  270 . The base  260  has a first side  261  for transferring heat between the cooling apparatus  250  and heat generating components  12 . The base  260  also has a second surface  262  for mounting the low-profile extrusion fins  270 . 
   Referring still to  FIG. 8 , the low-profile extrusion fins  270  are LPEs manufactured as a heat pipe capable of phase change heat transfer. The low-profile extrusion fins  270  are preferably formed with a plurality of micro-tubes  273 , each internally having a wick structure such as fins, grooved side walls, or metal screens, so as to maximize the heat transfer capability via capillary action. The micro-tubes  273  of the low-profile extrusion heat piping  270  are evacuated and then charged with a fluid such as water, glycol, alcohol, or other refrigerants, before the micro-tubes  273  are sealed. 
   Still referring to  FIG. 8 , a first end  271  of the low-profile extrusion fins  270  is mounted to the second surface  262  of the base  260  with a second end  272  extending outwardly from the base  260 . The plurality of low-profile extrusion fins  270  are preferably mounted in rows for convection heat transfer to the surrounding environment. In one embodiment, the base  260  can also be formed from a low-profile extrusion similar to the low-profile extrusion  220  in  FIG. 7 . 
   Referring still to  FIG. 8 , the use of the heat pipe type low-profile extrusion fins  270  in the cooling apparatus  250  increases the effective surface area in which heat is transferred from the heat generating components to the surrounding environment via the base  260 . The resulting cooling apparatus is therefore smaller in size and lighter in weight for the same effective cooling attributes. 
   Referring now to  FIG. 9 , there is shown an illustration of a stacked, low-profile cooling system  400  with an array of cooling fins secured to an assembly of the low-profile extrusion heat pipes described above. More specifically, the stacked, low-profile cooling system  400  includes a first phase plane heat pipe  401  with fins  403  secured to an undersurface of the heat pipe  401 , and fins  405  secured to a top surface of the heat pipe  401 . Stacked on top of the phase plane heat pipe  401  is a second phase plane heat pipe  410 , also in thermal contact with the cooling fins  405  disposed on the underside of heat pipe  401 , and further having a set of cooling fins  412  disposed on a top surface of heat pipe  401 . A first thermally conductive spacer block  422  is disposed between the first phase plane heat pipe  401  and the second phase plane heat pipe  410 . A third phase plane heat pipe  415  is stacked on top of the first and second phase plane heat pipes  401  and  410  also in thermal contact with the cooling fins  412  and further being assembled with cooling fins  417  stacked on a top surface of heat pipe  401 . Similarly, a second thermally conductive spacer block  424  is disposed between the second phase plane heat pipe  410  and the third phase plane heat pipe  415 . It may be seen that the cooling fins  403 ,  405 ,  412 , and  417  include elongated arrays in thermal contact with said phase plane heat pipes. 
   As shown herein, an angle between 0 and 90 degrees is suggested relative to the angulated portion of the phase plane heat pipe extending laterally outwardly from element  426 , which may be a heat source or a third thermally conductive spacer block disposed beneath the first phase plane heat pipe  401  with a heat generating component  420  disposed underneath (as shown in  FIG. 9 ). The heat source  420  may be any of a plurality of heat generating components, such as computer chips and/or elements within an electrical circuit. As also referenced in  FIG. 9 , the type of material, either copper or aluminum, has been specified on the thermally conductive spacer blocks  422 ,  424 , and  426 . The thermally conductive spacer blocks  422 ,  424 , and  426  provide a conduit for heat transfer from the heat generating component  420  up to and through the stacked, low-profile cooling system. 
   Referring now to  FIG. 10 , there is shown a perspective view of the stacked, low-profile cooling system  400  of  FIG. 9 . In the embodiment illustrated in  FIG. 10 , air flow is in the direction of arrow  430 . Air is permitted to flow around and through the fins  417 ,  412 ,  405 , and  403  to provide the cooling of the surfaces of the phase plane heat pipes  401 ,  410 , and  415 . Thus, the stacked, low-profile cooling system  400  provide improved operational efficiencies. 
   Referring now to  FIG. 11 , there is shown a side view of the stacked, low-profile cooling system  400  of  FIGS. 9–10 . The stacked, low-profile cooling system  400 , as described above, includes a condenser section  440  where condensing occurs. Likewise, an evaporator section  444  is illustrated in a generally centrally disposed area of the stacked, low-profile cooling system  400  wherein heat is absorbed from the heat source  420 . The transfer of the heat by the stacked, low-profile cooling system  400  causes evaporation and the movement of the fluid within the phase plane heat pipes  401 ,  410 , and  415  through adiabatic sections  446  wherein the fluid is allowed to expand without either loss or gain of heat, as is the technical definition of adiabatic. The angle of 0 to 90 degrees as shown herein further facilitates the movement of the evaporated fluid into the extremities of the heat pipes for the condensation of the heat transfer fluid in the condenser sections  440 , and the flow of fluid back through the adiabatic sections  446  and into the evaporator section  444  where additional heat may be absorbed. 
   Referring now to  FIGS. 9 ,  10 , and  11 , the stacked, low-profile cooling system  400  illustrates phase plane heat pipes in an innovative manner providing a low-profile and lightweight cooling alternative to conventional heat sinks. The low-profile and flat phase plane heat pipes provide an ideal surface to attach to a heat generating component and fins to cool the component. Through the stacking of phase planes, heat removal rates of over 100 watts can be achieved for a standard 31×−mm microprocessor, or keep lower wattage microprocessors at a lower operating temperature. 
   Referring still to  FIGS. 9 ,  10  and  11  in combination, there is shown the stacks of the phase plane heat pipes  401 ,  410 , and  415  that provide a low-profile, high watt density heat removal design. The materials of construction preferably include copper, aluminum, or other thermally conductive substances. The thermally conductive spacer blocks  422 ,  424 , and  426  above described and secured to the heat generating component  420  (as shown in  FIG. 9 ) may be formed of the same materials. The attachment process can be done through mechanically compressing the heat generating device to the heat sink with a thermal pad or thermal grease in between. The specific mounting mechanism is not shown herein and can include a variety of methods currently used in the heat sink market place. The base stack that is in contact with the heat generating component may also be the phase plane heat pipe as well. The fins  403 ,  405 ,  412 , and  417  can be attached on both sides of the phase plane heat pipes  401 ,  410 , and  415  providing surface area for the air/heat exchange to reduce the temperature of the cooling system  400  of  FIGS. 9–11 , and thus the heat generating component  420 . Air is ducted across the cooling fins  403 ,  405 ,  412 , and  417  and the heat pipes  401 ,  410 , and  415  in the manner shown in  FIGS. 9–11 . 
   Again referring to the operation of the stacked, low-profile cooling system  400 , the evaporator section  444  include that region of the phase plane heat pipes where the heat generating component  420  is positioned, as best illustrated in  FIG. 11 . The condenser sections  440  of the phase plane heat pipes located toward the ends provide for the recirculation of the heat transfer fluid and through the adiabatic sections  446 . Significant increases in performance are provided when gravity aids the operation of the individual phase plane heat pipes. The design can have an angular range from 0 (horizontal) to 90 (vertical), depending on the design parameters required for a particular device. Through the stacking approach and increased effective fin-surface area, the stacked, low-profile cooling system will provide superior performance in a low-profile package. 
   Referring now to  FIG. 12 , there is shown an alternative embodiment of the stacked, low-profile cooling system incorporating a possible design for a laptop computer. A heat generating component  487  is shown in phantom and may include a printed circuit board disposed in a laptop computer. In the embodiment illustrated in  FIG. 12 , air is sucked into a fan  480  as shown by arrow  486 . As shown by arrow  485 , air is blown out the sides through fin stock  482  mounted upon at least one phase plane heat pipe  484  of the type set forth and described in  FIGS. 9–11 . The evaporator section  470  of the phase plane heat pipe  484  is thermally and mechanically affixed to the heat generating component  487 . The fins  482  are placed on the condenser section  471  to aid in cooling. A 0 to 90 orientation may be placed on the phase plane  484  between the evaporator section  470  and the condenser section  471 . In another embodiment, a stacked array of heat pipes may be utilized in accordance with the stacked, low-profile cooling system, as well as the utilization of a phase plane heat pipe on both sides of the fan  480 . 
   Referring now to  FIG. 13 , a laptop computer  500  including an embodiment of the stacked, low-profile cooling system of  FIG. 12  is described. The fan  480  is disposed in a corner beneath a keyboard  502  and above a heat source  501  such as a circuit board. Air is drawn in to the fan  480  and dispersed outward through the fin stock  482 . Although the fin stock  482  is illustrated as being positioned vertically in the laptop, the fin stock  482  may also be positioned in other orientations, such as horizontally. 
   Referring now to  FIG. 14 , there is shown another embodiment of the stacked, low-profile cooling system of  FIG. 12  disposed in a laptop computer  500 . In the embodiment illustrated in  FIG. 14 , a fan  550  is connected with two fin stocks  560  for dispersing heat. The fan  550  may be located anywhere within the laptop  500  and have one or more fin stocks  560  associated with the fan  550 . The fin stocks  560  may be located at opposite sides of the fan  550 , or form an L-shape. The fan  550  may also have more than two fin stocks  560  associated with the fan. 
   Various embodiments of the stacked, low-profile cooling system may also include cross configurations where the phase plane heat pipes extend orthogonally one to the other and/or at angles acute to each other for purposes of positioning around components within an electrical system, such as a computer, and/or to improve air flow and to improve the thermal efficiency of the components of the electrical system. 
   Referring now to  FIG. 15 , there is shown an embodiment of a generally toroidally-shaped heat pipe coil cooling system  600  according to the principles of the present invention. The cooling system  600  removes heat from any heat source through an evaporation and condensation process similar to that described above in relation to  FIGS. 2–3  and  9 – 14 . Embodiments of the present invention, as illustrated below may function in any orientation, such as a vertical or a horizontal configuration. The cooling system  600  may include one or more heat pipes  602  with ends  604  and  606 . The sealed ends  604 ,  606  may be tapered or of a consistent width as desired. The heat pipe  602  is curved or bent upon itself (as shown herein) to form a coiled or generally torodially-shaped heat pipe  602  as shown herein so that the ends  604 ,  606  may be in close proximity to one another or direct contact with one another. The generally torodial shape of the heat pipe  602  creates a generally central void  608 . Further, the heat pipe  602  may include a plurality of micro-tubes (not shown) internally as described above in relation to  FIGS. 2–3  and  9 – 14  or the heat pipe  602  may include a single hollow tube. 
   In the embodiment illustrated in  FIG. 15 , the heat pipe  602  may optionally include a generally planar portion  610  for facilitating the mounting to, and/or coupling with a system including heat generating component  612 . The planar portion  610  of the heat pipe  602  creates a large area of surface contact between the heat pipe  602  and the system including heat generating components  612 . By increasing the amount of surface area of the heat pipe  602  that is in contact with the system including heat generating components  612 , the amount of heat that is absorbed and allowed to dissipate through the heat pipe  602  may be increased. Although shown with a barrier between the heat pipe  602  and the heat generating components  612 , the heat pipe  602  may be in direct contact with the heat generating components  612  in accordance with embodiments of the present invention. 
   With further reference to  FIG. 15 , in operation, the heat pipe  602  of cooling system  600  includes a condenser section  614  and an evaporator section  616 . The heat pipe  602  is charged with a heat transfer fluid such as, for example, glycol, alcohol, acetone or any other type of heat transfer fluid. Heat generated by the heat generating component  612  is transferred to the evaporator section  616  of the heat pipe  602 . The heat transfer fluid in the micro-tubes of the heat pipe  602  changes to vapor as the heat transfer fluid absorbs the heat radiated from the heat generating components  612 . The vapor then rises through the heat pipe  602  and collects in the condenser section  614 . As the vapor cools in the condenser section  614 , heat is transferred to the surrounding environment, thus efficiently removing heat from the heat generating components  612 . 
   Referring now to  FIG. 16 , there is illustrated another embodiment of the cooling system of  FIG. 15 . In  FIG. 16 , the cooling system  600  includes an inner fin structure  700  in thermal connection with an inner surface  702  of the heat pipe  602  to facilitate heat removal from a heat generating component  703 . In addition, an outer fin structure  704  may be in thermal connection with an outer surface  706  of the heat pipe  602  to facilitate heat removal from the heat generating components  612 . Although the illustrated embodiment shows an inner fin structure  700  in thermal connection with substantially the entire inner surface  702  of the heat pipe  602 , select portions of the heat pipe  602  may be in thermal contact with an inner fin structure  700 . For example, the inner fin structure  700  may be oriented at the condenser section  614 . Similarly, although the illustrated embodiment shows an outer fin structure  704  in thermal contact with substantially the entire outer surface  706  of the heat pipe  602 , excluding the planar portion  610 , the outer fin structure  704  may be positioned at select portions of the heat pipe  602 , i.e., the condenser section  614 . In addition, the inner and/or outer fin structures  700 ,  704  may terminate at each end  604 ,  606  or may be continuous across the ends  604 ,  606 . 
   Referring now to  FIG. 17   a , there is shown frontal view of the cooling system  600  incorporating the inner and outer fin structures  700 ,  704 , and also including a fan structure  800 . Some portions of the inner fin structure  700  have been eliminated in  FIG. 17   a  for clarity purposes. The fan structure  800  may be any type of fan used in the electronics industry for blowing air in an electronic environment. The inner fin structure  700  may have a height dimension that extends to a portion of the fan structure  800  having little or no air flow, known as the dead spot. When the fan structure  800  is active, air is directed through the inner and/or outer fin structures  700 ,  704  to increase heat removal. The fan structure  800  may have a diameter that is smaller or larger that the body of the cooling system  600 . It may be seen that the generally torodial shape of the heat pipe  602  effectively maximizes the effectiveness of the fan structure  800  so that a generally cylindrical column of air is drawn by the fan structure  800  and the air flow through the cooling system may therefore be maximized as shown in greater detail in  FIGS. 17   d  and  17   e.    
   Referring now to  FIGS. 17   b–c , a side elevational view of the cooling system  600  is shown mounted to the fan structure  800 . As shown in  FIG. 17   b , the cooling system  600  and fan structure  800  may be mounted to a base  802  by screws, adhesives, or other conventional bonding techniques known in the art. As illustrated in  FIG. 17C , the fan structure  800  may be mounted directly to the cooling system  600 . The fan structure  800  may or may not have the same dimensions as the cooling system  600 . 
   Referring now to  FIGS. 17   d–e , a side elevational view of the cooling system  600  and fan structure  800  including a diagrammatic schematic of an associated air column  802  is shown. The air column  802  created by the fan structure  800  is generally cylindrical in shape, matching the general shape of the cooling system  600 . Thus, the energy used to create the air flow is efficiently used by maximizing available air flow around and/or through the fin structures  700  and  704  and minimizing air flow outside the cooling system  600  or inside the void  608 . Increased efficiency in this aspect of the cooling system  600  maximizes the cooling effectiveness in accordance with principles of the present invention. 
   Referring now to  FIGS. 18   a  and  18   b  in combination, there is shown a cooling system  600  in accordance with principles of the present invention. In the embodiment illustrated in  FIGS. 18   a  and  18   b , a base plate  902  sits atop the planar portion  610  of the heat pipe  602 . The planar portion  610  of the heat pipe  602  sits atop a heat generating element (not shown). The base plate  902  functions as a clip that causes the planar portion  610  of the heat pipe  602  to maintain contact with the heat generating component. As shown in this embodiment, the inner fin structure  700  above the planar portion  610  has been eliminated to accommodate the base plate  902 . 
   Referring now to  FIGS. 19   a  and  19   b  in combination, there is shown another embodiment of the cooling system  600  of the present invention. The cooling system  600  incorporates a set of springs  1001  and  1002 . In the embodiment illustrated in  FIGS. 19   a – 19   b , the springs  1001  and  1002  attach the cooling system  600  to a heat generating component (not shown). The inner spring  1001  rests in the void  608  created by the torodial-shaped heat pipe  602 . The outer spring  1002  is oriented along an outer surface of the outer fin structure  704 . Thus, the heat pipe  602  may be mounted to the heat generating element without the use of thermal epoxies or soldering. The springs  1001  and  1002  exert opposing forces such the that the fin structures  700 ,  704  are in thermal contact with the heat pipe  602 . The use of the inner spring  1001  and the outer spring  1002  makes the cooling system  600  wider and allow the inner fin structure  700  to extend throughout the inner surface of the toroidal-shaped heat pipe  602  while allowing the heat pipe  602  to maintain direct contact with the heat generating element (not shown). 
   Referring now to  FIGS. 15 ,  16 ,  17   a–c ,  18   a–b , and  19   a–b , in combination, the heat pipe  602  may be a mass produced product that is processed through a tool. A graphite interface material used between the heat pipe  602  and the heat generating component  612  as well as between the fin structures  700 ,  704  and the inner and outer surfaces of the heat pipe  602 . The use of graphite, in essence, increases the thermal efficiency of the cooling system  600 . 
   It is believed that the operation and construction of the present invention will be apparent from the foregoing description of a preferred embodiment. While the device shown is described as being preferred, it will be obvious to a person of ordinary skill in the art that various changes and modifications may be made to the device without departing from the spirit and scope of the invention as defined in the following claims. Therefore, the spirit and the scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.

Technology Classification (CPC): 5