Patent Document

BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     This invention relates generally to a machine for removing debris from battery cells, and more specifically to a machine that removes metallic debris from the terminals of battery cells.  
         [0003]     2. Background Art  
         [0004]     Sometimes people think that the battery pack powering their cellular telephone or portable computer is simply a cell or two inside a plastic box. Nothing could be farther from the truth. Today&#39;s rechargeable battery packs include a complex array of electrical and mechanical components, including charging circuits, safety circuits, fuel gauging circuits, latches and connectors, just to name a few.  
         [0005]     By way of example, a rechargeable battery for a laptop computer may contain eight cells, protection circuitry, fuel gauging circuitry and a microprocessor. Each of these cells must be electrically connected to both the circuitry and the external connector for the overall battery pack to function properly. A popular way to make internal connections within battery packs is with tabs. A tab is a thin, flexible, electrically conductive, metal strip that can be welded to cells and soldered to boards.  
         [0006]     Referring now to  FIG. 1 , illustrated therein is an exemplary cell-tab assembly. A rechargeable cell  1  is shown electrically coupled to a tab  2 . A resistance, or spot, welder  3  makes the connection between the cell  1  and the tab  2 . This essentially works as follows: the cell  1  is placed into a mechanical fixture and an operator places the tab  2  atop the cell  1 . The spot welder  3  is then lowered onto the tab  2 , thereby machanically pressing the tab  2  against the cell  1 . An electrical current then flows from one electrode  5  of the welder  6 , through the tab  2 , through the cell  1 , back through the tab  2 , and into a second electrode  6  of the welder  3 . This current flow creates heat, which causes the tab  2  to fuse to the cell  1 .  
         [0007]     Occasionally, however, as with any manufacturing process, the process proves less than perfect. When this occurs, the weld between the tab  2  and cell  1  may not be sufficiently strong. The operator facing this scenario has two options: scrap the bad cell, resulting in increased cost to his employer, or rework the faulty cell-tab assembly. The latter is generally the chosen option, as manufacturers can ill afford to scrap expensive cells due to faulty weld joints.  
         [0008]     The rework process requires that the tab  2  be removed from the cell  1 . This is generally done by forcibly tearing the tab  2  from the cell  1 . When this is done, turning now to  FIG. 2 , metal bumps  20 , left over from the welding process, remain on the cell  1 . These metal bumps  20  must be removed prior to the attachment of another tab for the new weld to be secure. One prior art solution for removing these bumps is by way of a rotary tool with a grinding attachment. Generally speaking, an operator employing this solution takes a small grinding element and grinds off the metal bumps  20 .  
         [0009]     The problem with this process is that it can be quite destructive to the cells. The grinding, while removing the metal bumps  20 , can also remove metal from the cell housing. In come cases, the grinding can even create holes in the cell housing.  
         [0010]     There is thus a need for an improved method and apparatus for removing metal debris from battery cells. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  illustrates a prior art battery cell-tab assembly.  
         [0012]      FIG. 2  illustrates metal debris on a battery cell.  
         [0013]      FIG. 3  illustrates a perspective one preferred embodiment of a machine in accordance with the invention.  
         [0014]      FIG. 4  illustrates a top, plan view of one preferred embodiment of a machine in accordance with the invention.  
         [0015]      FIG. 5  illustrates a side, elevated view of one preferred embodiment of a machine in accordance with the invention.  
         [0016]      FIG. 6  illustrates a side, elevated view of one preferred embodiment of a machine in accordance with the invention.  
         [0017]      FIG. 7  illustrates a cutting action performed by a machine in accordance with the invention.  
         [0018]      FIG. 8  illustrates one method of operating a machine in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” 
         [0020]     Referring now to  FIG. 3 , illustrated therein is one preferred embodiment of a machine  300  for removed debris from a battery cell or battery cells. While the exemplary embodiment of  FIG. 3  is designed to accommodate a single cell, it will be obvious to those of ordinary skill in the art having the benefit of this disclosure that the machine  300  could be altered to accommodate multiple cells by duplication of parts.  
         [0021]     The machine  300  includes a base member  300  for supporting the various elements of the machine. The base member  301  may be mounted on rubber feet  302  to prevent motion while in action. Disposed atop the base member  301  is a means for holding a battery cell  303 . The means for holding a battery cell  303  includes a fixed block  304  for accommodating at least one battery cell. The fixed block  304  includes a recess  309  for holding a battery cell. The recess  309  of this exemplary embodiment is suited for holding cylindrical cells, and is thusly cut as a “V” shaped groove. It will be obvious to those of ordinary skill in the art having the benefit of this disclosure that other shapes could be substituted for the V-shaped recess to accommodate cells of other shapes, including rectangles, semi-circles, and squares.  
         [0022]     A moveable member, illustrated here as a moveable belt  305 , passes through the fixed block  304 . The moveable belt  305  forms a complimentary V-shape that opposes that of the recess  309 . In so doing, the moveable belt  305  and the recess  309  of the fixed block  304  form a closed loop  306  when viewed from the top. A battery cell may be inserted into this closed loop  306 .  
         [0023]     As stated, the moveable belt  305  passes through an aperture  301  in the fixed block  304 , and is coupled to a moveable support  307 . The moveable support  307 , and therefore the attached moveable belt  305 , are spring loaded against the fixed block  304  by at least one coil spring  309 . The coil spring  309  pulls the moveable belt  305  toward the recess  309  when the spring is at rest. A lever  308  coupled to the moveable support  307  allows an operator to open the closed loop  306  by pulling on the lever  308 . When the lever  308  is released, the coil spring  309  causes the moveable belt  305  to again pull back into the aperture  310 .  
         [0024]     A cutting means  312 , having at least one blade  313  coupled thereto, is provided for removing debris from the battery cells. The operation of the cutting means  312  will be described in more detail below with respect to  FIGS. 7 and 8 . The cutting means  312  is electrically isolated from the means for holding a battery cell  303  to prevent inadvertent short circuits of the battery cell through the machine. The isolation can be achieved in many different ways, including the addition of rubber gaskets between components. One preferred way of electrically isolating the cutting means  312  from the means for holding a battery cell  303  is by anodizing the various components. The anodization electrically insulates each component from another.  
         [0025]     A magnet  314  is disposed below the cutting means  312 . The magnet  314  serves to “catch” metallic debris that is removed from the surface of the battery cell when the moveable cutting means  312  passes across the cell&#39;s surface. While the magnet  314  is optional, it proves extremely effective in keeping the overall workspace clean. The magnet  314  additionally ensures that metallic fragments do not attach themselves to the cell, by static electricity, residual glue, ink or otherwise. Such “sticky fragments” could end up within a battery pack, thereby compromising the reliability of the pack.  
         [0026]     The cutting means  312  is mechanically coupled to a sliding member  311 . The sliding member travels on rails  312 , and moves parallel to the base member  301 . A removable blade carrier  315  secures the blade to the sliding member  311  by bolts or other fastening members. The sliding member  311  is actuated by a main lever  316 . The main lever  316  is rotatably coupled to the sliding member  311  by a gear assembly  317 . Essentially, when the main lever  316  is rotated, the gear assembly  317  actuates, thereby causing the sliding member  311 , and thus the cutting member  312 , to travel parallel to the base member  301  along the rails  318 . It is this parallel travel that allows the blade of the cutting member  312  to pass across at least one surface of the battery cell, thereby removing debris. In other words, actuation of the lever  316  actuates the cutting means  312 , thereby causing the cutting means  312  to pass along one end of the battery cell.  
         [0027]     The starting point and amount of travel of the sliding member  311  and cutting means is determined by a travel assembly. The travel assembly includes a threaded member  320  coupled to the sliding member  311 , a threaded stop  321  disposed about the threaded member  320 , a fixed adjustment stop  319  coupled to the base member  301 , and a second threaded stop  322 . The threaded member  320  passes through the fixed stop  319 , and the threaded stop  321  is coupled to the threaded member  320  such that the fixed adjustment stop  319  is disposed between the sliding member  311  and the threaded stop  321 .  
         [0028]     For removing debris with the push stroke of the lever  316 , the preferred method so debris falls to the magnet  314  rather than remaining on the cutting member  312 , the starting location of both the sliding member  311  and the cutting member  312  is set by the position of the second threaded stop  322  on the threaded member  320 . By twisting the second threaded stop  322  about the threaded member  320 , a user may adjust this starting location. Note that the sliding member  311  may optionally be spring loaded to keep the sliding member  311  pushed or pulled towards or away from the means for holding a battery cell  303  in the rest position.  
         [0029]     The space between the second threaded stop  322  and the first threaded stop  321 , relative to the fixed adjustment stop  319  determines the amount of travel of the sliding member  311 . One may adjust the travel of the sliding member  311  by twisting either the threaded stop  321  or second threaded stop  322  about the threaded member  320 . This twisting causes the first and second threaded stops  321 ,  322  to contact the fixed adjustment stop  319  at different points during the motion of the sliding member  311 .  
         [0030]     Referring now to  FIG. 4 , illustrated therein is a top, plan view of a machine in accordance with the invention. A second spring  400  can be seen in this view. Two springs  309 , 400  are useful in that it keeps the travel of the moveable support  307  uniform relative to the fixed member  304 .  
         [0031]     One inserts a battery cell into the machine  300  by pulling the lever  308  in the X direction  401 , thereby opening the closed loop  306 . When the battery is inserted into now expanded closed loop  306  of the means for holding a battery  303 , the amount if insertion is limited by the leveling means  403  coupled to the cutting means  312 . Once the battery cell contacts the leveling means  403 , the user releases the lever  308 , wherein the springs  309 ,  400  cause the moveable support to move in the -X direction  402 .  
         [0032]     The leveling means  403  is essentially a flat surface coupled to the cutting means  312  that limits the amount of insertion, thereby ensuring that the blade of the cutting means  312  aligns properly with a surface of the battery cell. After the battery cell is inserted, this alignment allows the blade of the cutting means  312  to pass cleanly across the surface of the battery cell when the cutting means  312  is actuated. As such, the cutting means “shaves” debris from the surface of the battery cell.  
         [0033]      FIGS. 5 and 6  illustrate side, elevated views of the machine. These views provide clearer looks of parts that are seen only fractionally in the perspective view of  FIG. 3 .  
         [0034]     Referring now to  FIG. 7 , illustrated therein is the cutting action performed by a machine in accordance with the invention. As stated above, after the means for holding a battery cell is opened, a battery cell  700  having metallic debris  701 ,  702  is inserted into the means for holding a battery cell  303  until one end or edge  703  of the cell touches or otherwise contacts the leveling means  403 . Once the means for holding a battery cell  303  has been closed, the cutting means  312  may be actuated. Actuation of the cutting means  312  causes the blade  313  to pass along the end  703  of the battery cell  700 , thereby removing debris  701 ,  702  from the battery cell  700 . Once removed, the debris  701 ,  702  may then fall upon the magnet  314 , where it remains magnetically attached until an operator performs a cleaning operation. The method described in this paragraph is illustrated in  FIG. 8 .  
         [0035]     While simple in operation, the machine produced superior and surprising results in practice. The principal improvement was an increase in pull strength resistance of tab-cell assemblies. In other words, cells that were shaved with the machine and then welded to tabs survived larger pull forces without the welds breaking than did new cells that were welded to tabs without having passed through the machine. This result is indicated in Table 1 below.  
                                                                                                           TABLE 1                                                       Avg.   Avg.               Pos.   Neg.   Pos.   Neg.   %   %   Pos.   Neg.               Term.   Term.   Term.   Term.   Impr.,   Impr.,   Term.   Term.           Test   w/   w/   w/o   w/o   Pos.   Neg.   %   %           Cycle   mach   mach   mach   mach   Term.   Term.   Impr.   Impr.                                1   A2   13.8   12.8   11.89   10.88   86.12   84.99               TIME   B2   12.5   12.1   11.56   9.06   92.51   74.84           C2   12.7   11   11.25   11.98   88.54   −8.91           D2   15.6   12.9   10.56   12.56   67.69   97.40           E2   12.8   13.1   13.01   10.87   −1.66   83.01           AVE   10.72   9.82   9.28   8.89   86.53   90.58   86.53   90.58           1       2   A3   13.1   12.9   11.88   9.59   90.68   74.31       TIME   B3   13.7   12.6   11.36   9.99   82.89   79.25           C3   13.9   13.5   11.83   11.23   85.12   83.19           D3   14.8   12.5   10.98   10.58   74.21   84.67           E3   12.3   12.9   11.58   11.33   94.15   87.79           AVE   13.56   12.88   11.53   10.54   85.00   81.85   85.00   81.85           2       3   A4   12.5   14.1   11.57   10.84   92.55   76.89       TIME   B4   12.9   11.9   13.56   9.98   −5.13   83.90           C4   13.6   12.3   10.56   10.58   77.66   86.04           D4   13.8   11.8   10.23   10.57   74.13   89.56           E4   15.5   13.8   11.95   10.99   77.11   79.60           AVE   13.66   12.78   11.58   10.59   84.74   82.88   84.74   82.88           3       4   A5   12.1   12.3   11.25   10.87   92.93   88.41       TIME   B5   12.6   13   11.32   11.23   89.87   86.39           C5   12.3   11.9   10.87   10.88   88.33   91.42           D5   13   11.7   11.25   11.26   86.50   96.20           E5   13.5   12.1   10.99   10.32   81.40   85.30           AVE   12.7   12.2   11.13   10.91   87.67   89.44   87.67   89.44           4            Overall Average of Improvement   85.99   86.19                  
 
         [0036]     As can be seen from the table above, when tests were run on sample sets of five cells, the average increase in pull strength was over 85%, or 1.6 lbs. This increase in pull strength not only increases the reliability of the overall battery pack, but also reduces costs due to customer field returns.  
         [0037]     A second improvement realized with the machine was reduced cost in manufacture. The reduced cost came primarily from two sources: First, overall raw material cost was reduced because cells did not have to be scrapped. When a poor weld joint appeared, the machine facilitated refurbishment of the cell surface. A second reduction of cost came from reduced labor time. In contrast to the time consuming rotary tool reworking, the machine facilitated a fast, clean refurbishment cycle.  
         [0038]     A third improvement was decreased electrical impedance. When cells were refurbished with the machine, experimental results showed lower electrical impedance from tab to cell. This reduced impedance means that more of the battery cell&#39;s energy will be delivered to the host, as opposed to being dissipated as heat in the battery pack.  
         [0039]     While the preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims.

Technology Category: 4