Abstract:
The present invention discloses a coating layer removing apparatus and a method for the same. The apparatus of the present invention comprises a transport device displacing an electrode plate; a laser device having a laser head arranged above the displacement path of the electrode plate; and a control center electrically connected to the transport device and the laser device. The method of the present invention comprises mounting an electrode plate on the transport device; using the control center to set the speed of displacing the electrode plate, and program the time interval, count and penetration depths of the laser beams; and using the device of the present invention to form exposed areas equidistantly on the electrode plate. The apparatus of the present invention automatically removes a coating layer with a laser beam without directly contacting the electrode plate. Therefore, the present invention can fast form exposed areas of high quality.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus to fabricate the electrode plate of a lithium battery, particularly to a coating layer removing apparatus and a method for the same, which can reduce the fabrication time and promote the yield rate. 
     2. Description of the Related Art 
     Lithium batteries have advantages of high energy density, compactness, environmental protection and combination ability. Therefore, lithium batteries have been widely used in many fields. With the increasing usage, more and more manufacturers invest in the technical development of lithium batteries. 
     Although the lithium battery has a very large market share, the fabrication speed thereof is hard to increase. The productivity of lithium batteries is limited by the fabrication of the electric-conduction tab and the electrode plate of the conventional electrode roll. Refer to  FIG. 1 . The electrode plate  100  may be a positive or negative electrode plate and comprises a substrate  110  and two coating layers  120  and  130  respectively formed on two surfaces of the substrate  110 . An electric-conduction tab  150  is soldered to a region of the substrate  110 , which is exposed from the electrode plate  100 . To increase the electricity storage within the original volume, the exposed area  140  where the electric-conduction tab  150  is joined to the electrode plate  100  should be as small as possible. In other words, the closer the exposed area  140  to the area of the electric-conduction tab  150 , the higher the electricity storage of a lithium battery. 
     The abovementioned scheme is ideal in theory but hard to realize in practice. Because the electrode plate  100  is very thin, removing the coating layers  120  and  130  to expose the substrate  110  is usually undertaken manually, which is laborious and time-consuming. Further, a slightly greater force applied by the worker may damage the very thin substrate  110 . In fact, either too great or too small a force applied by the worker would affect the quality and the discharging capability of the lithium battery. 
     Both the coating layers  120  and  130  must be partially removed to form the exposed areas  140 . However, the conventional technology can only remove a single coating layer  120  or  130  in one cycle. In other words, at least two cycles of operation are needed to form the exposed areas  140  of a single electrode plate  110 . Therefore, the manufacturers have to invest more manpower and capital to produce lithium batteries, which reduces the competitiveness of the Taiwan lithium battery manufacturers. 
     A Taiwan patent of application No. TW096116856 disclosed an apparatus to solve the abovementioned problem, which simultaneously heats specialized areas of the upper and lower surfaces of the electrode plate  100  and then applies a solvent to the coating layers  120  and  130  inside the heated areas. The coating layers  120  and  130  are softened and expanded by the solvent and then separated from the substrate  110 . The softened coating layers  120  and  130  are mechanically removed with a scraper or a file to form the exposed areas  140  on the electrode plate  100 . The prior-art patent can fast and economically fabricate the positive and negative electrode plates  100  with reliable quality. 
     We should admit that the Taiwan patent of application No. TW096116856 provides automatic fabrication and solves the low-productivity problem resulting from manually removing the coating layers  120  and  130  of the electrode plate  100 . The prior art can obtain the exposed areas  140  with the same depth in theory. However, the variation of the thickness of the coating layers  120  and  130 , the extent of heating, the extent of solvent etching and the variation of the force applied to scrape off the coating layers  120  and  130  affect the removal of the coating layer  120  and  130 , in practice. Thus, the damage rate of the electrode plates  100  is still high, and the yield and quality is still unstable, in the prior art. Therefore, the competitiveness promoted by the prior art is limited. 
     Accordingly, the present invention proposes a coating layer removing apparatus and a method for the same to overcome the abovementioned problems. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a coating layer removing apparatus and a method for the same, which use laser to remove the coating layers on the surfaces of an electrode plate, whereby is improved the damage rate of the substrate of the electrode plate and promoted the quality and yield of the products. 
     Another objective of the present invention is to provide a coating layer removing apparatus and a method for the same, which form the exposed areas on both the upper and lower surfaces of an electrode plate in a single cycle, and which favor the mass-production of lithium batteries, reduce the fabrication cost, and promote the competitiveness of the manufacturers. 
     To achieve the abovementioned objectives, the present invention proposes a coating layer removing apparatus, which comprises a transport device, a laser device and a control center. The transport device displaces an electrode plate. The laser device has a laser head arranged over the displacement path of the electrode plate. The laser head of the laser device emits a laser beam to hit the electrode plate. Because the electrode plate has coating layers on both surfaces, the coating layer hit by the laser beam is removed to expose the substrate and form an exposed area. The control center electrically connects with the transport device and the laser device to control the speed at which the transport device displaces the electrode plates, the timing at which the laser device emits laser beams, the count of the laser beams, and the penetration depths of the laser beams. 
     The present invention also proposes a coating layer removing method, which comprises steps: setting the displacement speed and stop positions of the electrode plate into the control center; inputting the time interval between two laser beams, the count of the laser beams, and the penetration depths of the laser beams; using the coating layer removing apparatus of the present invention to automatically form the exposed areas on the surfaces of the electrode plate according to the input conditions. 
     Below, the embodiments are described in detail in cooperation with the attached drawings to demonstrate the present invention and make easily understood the objectives, technical contents, characteristics and accomplishments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram schematically showing an electrode plate of a conventional electrode roll; 
         FIG. 2  is a diagram schematically showing a coating layer removing apparatus according to one embodiment of the present invention; 
         FIG. 3  is a block diagram schematically showing the architecture of a coating layer removing apparatus according to the present invention; 
         FIG. 4  is a diagram schematically showing that a laser device projects a marking frame onto an electrode plate according to the present invention; 
         FIG. 5  is a flowchart of a coating layer removing method according to the present invention; 
         FIG. 6  is a diagram schematically showing a coating layer removing apparatus according to another embodiment of the present invention; 
         FIG. 7  is a diagram schematically showing a coating layer removing apparatus according to yet another embodiment of the present invention; and 
         FIG. 8  is a diagram schematically showing a coating layer removing apparatus according to a further embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Refer to  FIG. 2  and  FIG. 3  a diagram and a block diagram respectively schematically showing a coating layer removing apparatus and the architecture thereof according to one embodiment of the present invention. The coating layer removing apparatus of the present invention comprises a transport device  10 , a laser device  20 , a blowing device  30  and a control center  40 . The transport device  10  is used to displace a positive or negative electrode plate, which will be referred to as the electrode plate  200  thereinafter. The transport device  10  includes a releasing wheel unit  11 , a winding wheel unit  12 , a tension wheel unit  13  and two fixing wheel units  14 . One end of the electrode plate  200  is fixed to the releasing wheel unit  11 , and then inserted through the tension wheel unit  13  and the fixing wheel units  14 , and finally fixed to the winding wheel unit  12 . The releasing wheel unit  11  is a passive element, and the winding wheel unit  12  is an active element. When the winding wheel unit  12  reels up the electrode plate  200  clockwise, the electrode plate  200  moves along the displacement path constructed by the tension wheel unit  13  and the fixing wheel units  14  and drive the releasing wheel unit  11  to rotate clockwise. The position of the tension wheel unit  13  can be adjusted to modify the tension of the electrode plate  200 . 
     Refer to  FIG. 4 . The laser device  20  is arranged at a predetermined position above the displacement path of the electrode plate  200 . The laser device  20  includes a light-guiding and focusing unit  21  and a laser head  22 . In the laser carving technology, the light-guiding and focusing unit  21  projects a marking frame f onto the surface of an object, and the laser head  22  emits a laser beam to hit the marking frame f and remove the material inside the marking frame f. The laser head  22  may be a carbon dioxide laser gun, a YAG laser gun or an excimer laser gun. The electrode plate  200  of a common lithium battery includes a substrate  210  and two coating layers  220  and  230  respectively on the upper and lower surfaces of the electrode plate  200 . The materials of the substrate  210  and the coating layers  220  and  230  vary with the polarity of the electrode plate  200 . In this embodiment, the laser beam hits the coating layer  220  on the upper surface of the electrode plate  200 ; the area marked by the marking frame f is an exposed area  240  to be joined with an electric-conduction tab. 
     The structures of the positive and negative electrode plates, the laser carving technology and the marking technology are all prior arts. In the specification, the present invention does not exclude any of other laser guns that can remove the coating layer. The substitutions of laser guns belong to the equivalent modifications or variations according to the spirit of the present invention and should be included within the scope of the present invention. 
     The blowing device  30  includes an air compressor (not shown in the drawing) and a nozzle  31 . The nozzle  31  is arranged beside the laser head  22  and aimed at the area marked by the marking frame f. The air compressor supplies an inert gas to the nozzle  31  to blow the area marked by the marking frame f. The inert gas can lower the temperature of the area heated by the laser beam. The control center  40  electrically connects with the transport device  10 , laser device  20  and blowing device  30 . The control center  40  has a keyboard  41  and a screen  42 . Via the keyboard  41 , the user inputs data to control the start, pause, stop, rotation speed of the winding wheel unit  12 , and the count, time interval and penetration depths of the laser beams. 
     Below is described the method to implement the device of the present invention to effectively remove the coating layer  220  of the positive or negative electrode plate  200 . Refer to  FIG. 5 . In Step S 1 , the worker mounts the electrode plate  200  on the releasing wheel unit  11 , guides one end of the electrode plate  200  to pass through the tension wheel unit  13  and the fixing wheel units  14 , and winds the electrode plate  200  on the winding wheel unit  12 . Next, in Step S 2 , the worker starts the control center  40  and begins the position-calibration function to locate the electrode plate  200  at an initial position. 
     Next, in Step S 3 , the worker programs the displacement speed, the spacing between two pause areas, and the pause time via the keyboard  41  and checks the input data via the screen  42 . The control center  40  is programmed to start the laser device  20  to emit the laser beam when the movement of the electrode plate  200  pauses. Next, in Step S 4 , the worker determines the size of the marking frame f of the light-guiding and focusing unit  21 . The electrode plate  200  is very thin. The counts of laser beams and the penetration depth of each laser beam for a single exposed area  240  is carefully selected, so that the laser energy is applied to each exposed area  240  in several cycles by small amounts lest the substrate  210  be damaged. The penetration depth of the last laser beam for each exposed area  240  is set to be the smallest so that the action of the last laser beam has a polishing effect to remove the residual coating layer  220 . The start timing and the end timing of the blowing device  30  are also programmed in Step S 4 . 
     After all the necessary settings have been done, the worker starts the coating layer removing apparatus of the present invention to automatically remove the coating layer  220  of the electrode plate in Step S 5 . Step S 1  and Step S 2  are not necessarily undertaken in the beginning. Step S 1  and Step S 2  may be also executed after Step S 3  and Step S 4 . The sequence exchange mentioned above would not influence the result of the present invention. 
     Once the coating layer removing apparatus is started, the winding wheel unit  12  drives the electrode plate  200  to move for a short distance to reach the predetermined position. Next, the light-guiding and focusing unit  21  of the laser device  20  projects a making frame f onto the surface of the electrode plate  200  and focuses a laser beam onto the marking frame f. According to the count and penetration depths set in Step S 4 , the laser device  20  gradually reduces the thickness of the coating layer  220  cycle after cycle. At the same time, the nozzle  31  of the blowing device  30  sends out an inert gas to reduce the temperature of the electrode plate  200  lest overheat distort the electrode plate  200 . After an exposed area  240  is done, the control center  40  controls the winding wheel unit  12  to rotate again to displace the electrode plate  200  for a given distance so that the laser device  20  can undertake a next cycle of coating layer removing operation. The steps of displacing the electrode plate, applying laser beams and supplying inert gas will be performed repeatedly until a predetermined quantity of exposed areas  240  is obtained. The removal of the coating layer  230  on the opposite surface is realized via merely re-mounting the electrode plate  200  of the winding wheel unit  12  to the releasing wheel unit  11  without undertaking Step S 3  and Step S 4  any more. Therefore, the present invention can reduce the damage rate of the electrode plate  200  and promote the quality of the products. 
     According to the description of the device and method of the present invention, the persons skilled in the art can achieve higher production efficiency via varying the numbers of the tension wheel units, the fixing wheel units and the laser devices. Refer to  FIG. 6  a diagram schematically showing a coating layer removing apparatus according to another embodiment of the present invention. In this embodiment, the transport device  10  includes a releasing wheel unit  11 , a winding wheel unit  12 , two tension wheel units  13  and  13 ′, a plurality of fixing wheel units  14  and  14 ′, and two diverting wheel units  15  and  15 ′. After passing through the diverting wheel units  15  and  15 ′, the upper surface and the lower surface of the electrode plate  200  is top down and bottom up. In other words, the orientation of the upper coating layer  220  and the lower coating layer  230  are exchanged. Thus, the original upper coating layer  220  becomes downward, and the original lower coating layer  230  becomes upward. In this embodiment, the laser head  22  of the laser device  20  is faced to the coating layer  220 , and the laser head  22 ′ of the laser device  20 ′ is faced to the coating layer  230 . Two nozzles  31  and  31 ′ are respectively arranged beside the laser devices  20  and  20 ′. Thereby, the exposed areas  240  on two sides of the electrode plate  200  are simultaneously completed in a single process. 
     Refer to  FIG. 7  for yet another embodiment of the present invention. In this embodiment, an image capture device  50 , such as CCD (Charge Coupled Device), is arranged beside the laser device  20  to capture the image of the exposed area  240  to improve the soldering quality of the electrode plate  200  and the electric-conduction tab. The image capture device  50  is electrically connected with the control center  40 , and the control center  40  presents the image on the screen  42 . Thus, the worker can perform quality control via the screen  42 . Alternatively, the control center  40  examines the color difference of the image with an image processing technology. When the color difference exceeds a standard, the control center  40  initiates a warning action. The warning action includes triggering an alarm light or a buzzer to remind the workers of the quality problem. Besides, a suction nozzle  61  is arranged beside the area marked by the marking frame f to remove the debris generated in removing the coating layers  220  and  230  lest the debris affect the quality of soldering. Thereby, the fabrication quality of lithium batteries is further promoted. 
     Refer to  FIG. 8  for a further embodiment of the present invention. In this embodiment, the electrode plate  200  passes a positioning axis  71  of an edge-positioning module and diverts downward. A photosensor  80  is arranged between the positioning axis  71  and the laser head  22 ′ and electrically connected to the control center  40 . When the exposed area  240  of the coating layer  220  passes the photosensor  80 , the photosensor  80  generates a positional signal. The control center  40  receives the positional signal and determines the timing of triggering the laser device  20 ′. Then, the laser device  20 ′ emits laser beams to remove a portion of the coating layer  230 . The edge-positioning module is a positioning device usually used in the transport device of plate-like materials. In the present invention, the edge-positioning module is used to guarantee that the consistency of the positions of the exposed areas  240 . In the present invention, a camera and an image processing technology may replace the photosensor  80  to generate the positional signal. 
     In conclusion, the present invention adopts laser devices to remove the coating layers to prevent from damaging the substrates of the positive and negative electrode plates and promote the quality and yield rate of the electrode roll. Further, the present invention realizes fabrication automation, reduces the manpower and cost for the manufacturers, and promotes the productivity of lithium batteries. 
     The embodiments described above are to demonstrate the present invention to make the persons skilled in the art to understand, make and use the present invention. However, the embodiments are not intended to limit the scope of the present invention. Any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention, which is based on the claims stated below.