Patent Publication Number: US-2010108298-A1

Title: Heat pipe with planished end surface

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat pipe, which has a planished end surface. Particularly, an electronic device can be flatly mounted on the planished end surface of the sealed end of the heat pipe. 
     2. Description of the Prior Art 
     With the progress of science and technology, the technologies of many electronic products all face problems of heat dissipation but can not break through. For example, a great deal of heat is generated by the central processing unit of a computer; the heat will have harmful effect on the whole system if the heat is not removed. Heat pipe plays a major role in the heat dissipating function of the central processing unit of a computer. 
     The prior method for manufacturing sintered heat pipe is to seal an end of a metal pipe by fusing in high temperature. Then, a metal bar is placed into the pipe, and metal powder is filled into the pipe. After the sintering process, the manufacturing of the heat pipe is finished by pulling out the metal bar. The sealed end of the metal pipe, which is manufactured by the method, is perfectly round and thicker than the circumferential wall, and the endpoint of the inner wall is lacking in capillarity. Therefore, the applications of the heat pipe nowadays are confined to the circumferential wall of the pipe rather than its end portion. 
     Accordingly, a scope of the present invention provides a heat pipe that has a planished end surface. Thereby, an electronic device can be flatly mounted on the planished end surface of the sealed end of the heat pipe. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above-mentioned purposes and solve the disadvantages discussed previously, the present invention provides a heat pipe that has a planished end surface. Thereby, an electronic device can be flatly mounted on the planished end surface of the sealed end of the heat pipe. 
     The present invention provides a heat pipe that has a planished end surface, and thereby an electronic device can be flatly mounted on the planished end surface of the sealed end of the heat pipe. The heat pipe includes a sealed metal pipe and a porous capillary diversion layer. The metal pipe has a space in vacuum, a working fluid is in the space, wherein the planished end surface is formed on the outer wall of an sealed end of the metal pipe. The porous capillary diversion layer is disposed in the space, and it covers and includes the inner wall of the sealed end of the metal pipe. 
     The present invention uses stamping process to form a planished surface on an end of the heat pipe, and it disposes a porous capillary diversion layer to cover the planished end of the inner wall for the working fluid to smoothly circulate. Therefore, an electronic device can be flatly mounted on the planished end surface of the sealed end of the heat pipe and has good heat dissipating effect. 
     The advantage and spirit of the invention may be understood by the following recitations together with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         FIG. 1A  is a schematic diagram of the external view of a heat pipe. 
         FIG. 1B  is a sectional diagram along the L-L line in  FIG. 1A  for illustrating the inner structure of a heat pipe. 
         FIG. 2A  to  FIG. 2G  illustrate the manufacturing process of the heat pipe of the first embodiment according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a heat pipe that has a planished end surface. Particularly, an electronic device can be flatly mounted on the planished end surface of the sealed end of the heat pipe. 
     The heat pipe of the present invention includes a sealed metal pipe and a porous capillary diversion layer. The metal pipe has a space in vacuum, and a working fluid is in the space, wherein the planished end surface is formed on the outer wall of a sealed end of the metal pipe. The porous capillary diversion layer is disposed in the space, and it covers and includes the inner wall of the sealed end of the metal pipe. The planished end surface of the sealed metal pipe is formed by a stamping process. 
     Referring to  FIG. 1A ,  FIG. 1A  is a schematic diagram the external view of a heat pipe. As shown in  FIG. 1A , the heat pipe  1  includes a sealed metal pipe  12  and a planished sealed end  16 . 
       FIG. 1B  is a sectional diagram along the L-L line in  FIG. 1A  for illustrating the inner structure of a heat pipe. As shown in  FIG. 1B , according to the first embodiment the present invention, the heat pipe  1  further includes a porous capillary diversion layer  14 . The metal pipe  12  has a space in vacuum, and a working fluid is in the space. The porous capillary diversion layer  14  is disposed in the space, and it covers and includes the inner wall of the sealed end  16  of the metal pipe  12 . 
     The method for planishing a sealed end of a pipe body for making a heat pipe will be described blow. Referring to  FIG. 2A  to  FIG. 2G ,  FIG. 2A  to  FIG. 2G  illustrate the manufacturing process of the heat pipe of the first embodiment according to the present invention. 
     First, provide a pipe body, a female mold, and a male mold. The pipe body has an open end. The female mold has a flat bottom surface, and the female mold is adapted to receive the sealed end of the pipe body. The male mold has a flat top surface corresponding to the bottom surface of the female mold, and the male mold is adapted to be inserted into the pipe body from the open end of the pipe body. 
     Referring to  FIG. 2A , as shown in  FIG. 2A , the sealed end  16  of the pipe body  12  is first fixed within the female mold  24 , and the male mold  26  is inserted into the pipe body  12 . Then, as shown in  FIG. 2B , by use of the male mold  26 , press the sealed end  16  of the pipe body  12  with respect to the female mold  24  to form a planished surface at the sealed end  16  of the pipe body  12 . At this point, the pipe body  12  that has the planished end surface is finished. 
     Then, the pipe body, which has the planished end surface, is produced into a heat pipe. A central bar is provided, and the diameter of the central bar is smaller than the diameter of the pipe body. 
     Referring to  FIG. 2C , as shown in  FIG. 2C , a first metal powder  142  is placed into the pipe body  12 , the central bar  28  is inserted into the pipe body  12  from the open end of the pipe body  12 , and it presses against the first metal powder  142 . As shown in  FIG. 2D , a second metal powder  144  is filled between the pipe body  12  and the central bar  28 . Then, as shown in  FIG. 2E , a sintering process is executed to fuse the second powder  144  with the first powder  142 , thus forming a porous capillary diversion layer  14  on the inner wall of the pipe body  12 . The central bar  28  is then taken out from the pipe body  12 . Referring to  FIG. 2F , as shown in  FIG. 2F , a working fluid is injected into the pipe body  12  by using a tubule  20 . Finally, vacuum the pipe body  12  and seal the open end of the pipe body  12 . Then, the heat pipe shown in  FIG. 2G  is finished. 
     The first powder and the second powder can be a copper powder, a nickel powder, a silver powder, a metal powder of which the surface is plated with copper, nickel or silver, or other similar metal powder. 
     In one embodiment, the inner wall of the pipe body that has the planished end surface has a plurality of tiny nicks which form an initial porous capillary diversion layer on the pipe wall. The manufacturing method of the heat pipe made from the pipe body with the planished end surface comprises the following steps. First, place a first metal powder into the pipe body, and insert the central bar into the pipe body from the open end of the pipe body and against the first metal powder. Then, execute a sintering process to fuse the metal powder with the initial porous capillary diversion layer located at the periphery of the inner wall of the pipe body, and form a porous capillary diversion layer which covers and comprises the inner wall of the sealed end of the metal pipe. Take the central bar out from the pipe body and inject a working fluid into the pipe body by using of a tubule. Finally, vacuum the pipe body and seal the open end of the pipe body. 
     In one embodiment, the manufacturing method of the heat pipe made from the pipe body, which has the planished end surface, manufactures a plurality of tiny nicks by using a mechanical process to form a porous capillary diversion layer, it then injects a working fluid into the pipe body by using a tubule. Finally, the pipe body is vacuumed, and the open end of the pipe body is sealed. 
     In one embodiment, the manufacturing method of the heat pipe made from the pipe body, which has the planished end surface, is described below. First, sinter a plurality of metal particles on the inner wall of the pipe body, and dispose a metal net on the inner wall to form a porous capillary diversion layer. Similarly, inject a working fluid into the pipe body by using a tubule, and vacuum the pipe body. Finally, seal the open end of the pipe body, and the heat pipe, which has a planished end surface is finished. 
     In one embodiment, the manufacturing method of the heat pipe made from the pipe body, which has the planished end surface is described below. First, lay a corrugated metal wire cloth on the inner wall of the pipe body, and dispose a flat metal net cloth on the inner wall to form a porous capillary diversion layer. Inject a working fluid into the pipe body by using a tubule, and vacuum the pipe body; then, seal the open end of the pipe body. The shape of the corrugated metal wire cloth is in triangular form, rectangular form, trapezoid form, or flexuous form. 
     In one embodiment, the shape of the planished end surface is tabular or fluted. The pipe body is made of a copper metal, a nickel metal, a silver metal, or other similar metal materials. 
     In one embodiment, the electronic device connected to the heat pipe can be a light emitting diode, a laser diode, or an integrated circuit. 
     In practical application, when stamping the planished surface of the pipe body, the pipe body may be broken due to excess deformation. By heating the pipe body and increasing the flexibility by heat pressing, this can avoid forming cracks on the pipe body caused by stamping. 
     With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.