Patent Publication Number: US-6660138-B2

Title: Electropolishing process means for an inner surface of a long tube

Description:
1. FIELD OF THE INVENTION 
     The present invention is an electropolishing process and device for electropolishing an inner surface of a long tube, especially applied to a long tube having a length greater than two meters and an inside diameter having a range between 0.3 to 5 cm. 
     2. BACKGROUND OF THE INVENTION 
     A process of electropolishing includes connecting a workpiece to an anode and a metal to a cathode. Aforesaid structure of the workpiece connected to the anode and the metal connected to the cathode is put into an electrolyte for electrifying with a direct current to remove the defects on the workpiece surface and make the surface shiny and smooth. Electropolishing improves surface cleanness, roughness, passivation, etc. For different fields of semiconductor, chemical industry, biochemical engineering, food industry, tubes are needed to deliver fluids of those fields. Inner surfaces of tubes are treated by polishing or electrolysis to approach high cleanness and anti-corrosion. Especially, products of IC/LCD/III-V require high standards of cleanness and anti-corrosion, thus, applying the present invention to the products is a challenge. 
     U.S. Pat. Nos. 4,826,582 and 4,849,084 used part of the technologies of electropolishing a 10-meter heat exchange tube. The electrode device for positioning the workpiece and sealing the electrolyte is required. The prior art adopts a 3-layer structure of delivering electrolyte of high pressure air, but unfortunately the structure is very complicated and only suitable for the larger diameter workpieces, not for the tube of inside diameter under 3 cm. 
     In U.S. Pat. No. 5,958,195, which taught the technology of electropolishing an inner surface of a long and bended tube. However, to electropolish a bended tube, electrode must move alone a bended curve so as to not cause a short circuit. The most important parts are a flexible electrode and an insulation device. The insulation device avoids short circuit and non-concentricity, but this kind of device blocks a flow of electrolyte and makes a non-uniform electric field. 
     U.S. Pat. Nos. 4,601,802 and 4,705,611 offers a fixture applied an inside tube, and the fixture stabilizes a plurality of axially rotating tubes simultaneously. An end connector can circulate tube and exhaust gas from an upper end, and electrolyte can be recycled after overflowing. An electrode length is equal to the tube length, therefore a huge space and a super power supplier are needed to fit such conditions. 
     Based on the aforesaid issues, the present inventor of the patent has being studied and referred to practical experiences and theory for designing and effectively improving the prior arts. 
     SUMMARY OF THE INVENTION 
     The first object is to offer an electropolishing process and device for electropolishing an inner surface of a long tube, which improves an electrode design and applies theories of macro and micro polishing to an electrode for improving a manufacturing rate for both smoothing and passivation effect on the surface of workpiece. 
     The second object is to offer an electropolishing process and device for electropolishing an inner surface of a long tube, which can treat an inner surface of a tube greater than 2 meters and an inside diameter range of 0.3 to 5 cm. The device is simple to reduce equipment costs. 
     The third object is to offer an electropolishing process and device for an inner surface of a long tube, which avoids short circuiting and non-concentricity problems. An electrode of the present invention is installed through a center of a partition, so the electrode has a certain distance with the inner surface in tube because the partition supports the electrode. Therefore, the short circuit and non-concentricity are solved. Further the average electric field is kept all the time because the partition is round. 
     The fourth object is to offer an electropolishing process and device for electropolishing an inner surface of a long tube, which electrode can be designed to have multiple sections. Thereby, eliminating the need for a huge storage space. Further, the electrode can be added to different sections depending on needs to improve electrolyzing and polishing result. 
     The appended drawings will provide further illustration of the present invention, together with description; serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a practical application of the present invention. 
     FIG. 2 is a first preferred embodiment of the present invention. 
     FIG. 3 is a preferred embodiment of an electrode of the present invention. 
     FIG. 4 is a second preferred embodiment of the present invention. 
     FIG. 5 is a third preferred embodiment of the present invention. 
     FIG. 6 is a sectional view of a partition of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For different fields of semiconductor, pharmaceutical industry chemical industry, biochemical engineering, food industry, inner surfaces of needed tubes and fitting of aforesaid fields are treated by electropolishing process for improving surface cleanness, roughness and passivation results. The present invention comprises an electrolyte delivering system, which makes electrolyte uniformly pass through an inner surface of a long tube. A cable guides a direct current to a working area of an inner surface of tube, and the electrolyte is an electrifying media to make a complete electric path. An end of the cable can be added to an insulated electrode means, which slowly moves along an imaginary central axis of the tube such that a cathode electrode does not contact an anode electrode, thus short circuit problem is then evaded. The electrode means is complex to produce a huge and fine polishing result, such as a Cu-W bar. 
     Referring to FIG. 1, which is a schematic of a practical application of the present invention. Electrolyte is stored in a tank  10 , and a heater  11  is inside the tank  10  for keeping the electrolyte at a predetermined temperature. Electrolyte passes through a switch  12  and a pipe  23  to a tube  16 . The switch  12  is made of TEFLON or other heat-resistant and acid-proof material. The tube  16  is placed on an inclined platform  17 , and thus a higher end of tube  16  connects to the pipe  23  for passing electrolyte from higher end to a lower end. Inclined angles of the inclined platform  17  can be adjusted to control electrolyte flowing speeds. Tube  16  includes at least one electrode (not shown in FIG.  1 ), which is hung up by a cable  20 , and another end of the cable  20  is rolled up by an axial mechanism  22 . The axial mechanism  22  rolls up cable  20  to move the electrode upward when electropolishing process reaction is being performed inside tube  16 . The present invention adopts that electron exchanging from an anode half reaction and a cathode half reaction generates an electropolishing process result. Tube  16  is an anode, thus an inner surface of tube  16  is an anode, and anode loses electrons. The electrode is a cathode, and the cathode receives electrons. FIG. 1 does not show the electrode, so only cable  20  is shown to represent the electrode. Tube  16  is about 2 meters long or more. The electrolyte temperature is lower when electrolyte approaching to a lowest end of tube  16 , thus a plurality of halogen bulbs  15  are placed around tube  16  for heating. Electrolyte is recycled after passing through tube  16  to a recycling tank  13 , then it is delivered back to tank  10  by a pump  14  which is heat-resistant and acid-proof. The aforesaid explains a complete procedure for electropolishing process. Following is a detail description. 
     Referring to FIG. 2, which is a first preferred embodiment of the present invention. In the embodiment, at least one partition  18 , a complex electrode  21  and a propeller  19  are in a tube  16 ; the electrode  21  is hung up by the cable  20  and driven by the axial mechanism  22  to move toward the axial mechanism  22 . Electrolyte fills an inner diameter of the tube  16 , and a diameter of the partition  18  is slightly smaller than an inner diameter of the tube  16  (a diameter range of electropolishing process of the present invention is between 0.3 to 5 cm). The partition  18  floats in the tube  16  and is almost perpendicular to the inner surface of tube  16 , so the partition  18  does not touch the inner surface of the tube  16 . Finally, the cable  20  provides a direct electric current to the electrode  21  and through a medium of the electrolyte to the inner surface; the electropolishing process reaction is then started. The electrode  21  is placed in a center of the partition  18 , and it is double electrodes, which is complex for approaching a huge and fine polishing result. Further, the electrode  21  can be made from different materials, such as copper, wolfram, stainless steel, etc. On the other hand, the electrode  21  can be single as well (not shown in figure), and the single electrode is positioned between partition  18  and the propeller  19 . The reaction is preceded only between them, so electropolishing process goes slowly. The propeller  19  quickly exhausts air bulbs generated by the reaction, because air bulbs affect polished surface. When electrolyte flowing from an end close to axial mechanism  22  to another end of tube  16 , propeller  19  is also driven by axial mechanism  22  in an opposite direction. The propeller generates a vortex by the aforesaid relative motion. Air bulbs in between partition  18  and the propeller  19  and another side of partition  18  are exhausted fast. Referring to FIG. 5, which is a third preferred embodiment of the present invention. Propeller  19  can be replaced with a screw slideway  24 , and air bulbs go through the screw slideway  24  to an outside. Obviously, the screw slideway  24  functions as propeller  19 . As shown in FIG. 2, plural slots  25  are designed on an outer edge of partition  18 , those slots  25  make electrolyte flow close to inner surface more fluently and a boundary layer is then broken to generate an average anode membrane, such flow effectively brings air bulbs out. Referring to FIG. 6, which is a sectional view of a partition of the present invention. For fluently introducing electrolyte, partition  18  has many holes  26  as meshes. Further, the partition  18  is made of TEFLON or other insulating material for saving total energy and enhancing the electropolishing process result. Another function of partition  18  is to avoid contacting the negative electrode and positive inner surface, hence short circuit and non-concentricity are solved. Further, the average electric field is kept all the time because partition  18  is round. Partition  18  is variable for different tube diameters. 
     Referring to FIG. 3, which is a preferred embodiment of an electrode of the present invention. The electrode can be made of plural materials for different levels of polishing. A complex electrode  21  consists of a first electrode  211  and a second electrode  212  for two-stage electropolishing process reaction, and it is to promote result shown as in FIG.  1 . 
     Referring to FIG. 4, which is a second preferred embodiment of the present invention. An electrode  21  of the preferred embodiment includes a third electrode  213 , a fourth electrode  214 , a fifth electrode  215  and a sixth electrode  216 . The electrodes are placed in a center of a plurality of partitions  18 . This embodiment is for multi-stage reaction, and it seems each kind of electropolishing processing reaction can be approached from the embodiment. 
     While the present invention has been shown and described with reference to preferred embodiments thereof, and in terms of the illustrative drawings, it should be not considered as limited thereby. Thus, the present invention is infinitely used. However, various possible modification, omission, and alterations could be conceived of by one skilled in the art to the form and the content of any particular embodiment, without departing from the scope and the spirit of the present invention. 
     The invention is disclosed and is intended to be limited only the scope of the appended claims and its equivalent area.