Abstract:
An apparatus and method for finishing an electrically conductive part through electrochemistry is disclosed. The cathode electrode is configured so as to fit simultaneously in one or more windows or pockets or in a combination thereof. In one embodiment of the present invention a disc-covering cathode electrode is provided that can simultaneously finish all of the windows and pockets using an electrolyte.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to metal material removal and polishing. More particularly, the present invention relates to a method and apparatus for electrochemically finishing the surface of an electrically conductive part by deburring and polishing one or more surfaces of the part.  
       BACKGROUND OF THE INVENTION  
       [0002]     Automobile and truck wheels include an annular wheel rim capable of receiving and securely holding a pneumatic tire. A wheel disc having a circular configuration is formed within the annular wheel rim. The wheel disc may be solid or may have one or more apertures formed therethrough for aesthetics and to reduce weight. The wheel disc will also of necessity have a plurality of wheel attachment holes formed threrethrough for attachment to the vehicle wheel hub studs.  
         [0003]     As is known, vehicle wheels were for many years produced from steel. Such wheels were produced by stamping of the wheel disc and attaching it to a formed rim. However, as technology improved non-ferrous wheels became valuable alternative to the stamped-steel wheels previously known. The fabricating process (forging or casting) allowed the manufacturer to make the wheel wherein the wheel disc has a variety of patterns and configurations. Early wheels were made from steel by casting or forming. While providing improvements over the stamped and formed steel wheel, the wheels made from steel were restricted to the styling design. Eventually because of advancements in fabricating techniques, additional castable or forgeable metal materials were used, including such relatively light-weight materials as aluminum, magnesium, and titanium alloys.  
         [0004]     Regardless of the material from which the light metal wheel is formed, the manufacturing process typically results in rough surface, corners, edges and burrs around both the wheel openings and the wheel pockets formed or machined on the face of the wheel. These imperfections must be removed for reasons both of aesthetics and safety. The finishing process which removes rough surface, corners, edges and metal burrs has typically been very time-consuming, involving as is known the use of a variety of grinding, polishing and finishing tools applied with various levels of manual operations and automation. While providing satisfactory results in general, the use of such manpower and equipment has been both time-consuming, quality inconsistent and cost-ineffective, thus being a possible but less-than-optimum solution for the production of wheels on any sort of volume basis. In addition, the use of deburring equipment on light metal wheels, particularly on aluminum alloy wheels, has also been proven to be undesirable because of the tendency for deburring to discolor the metal.  
         [0005]     In an effort to overcome the inefficiencies of known methods at wheel finishing, electrochemical finishing of wheels made from a conductive metal have been put forward. The electrochemical process has been used in two ways in which one process relies on an electrochemical reaction between an anode and a cathode and the other process relies on a combination of electrochemistry and mechanical grinding/polishing.  
         [0006]     According to the first known technique, the metal part (the anode) is operatively connected with the positive post of a rectifier. The finishing electrode (the cathode) is operatively connected with the negative post of the rectifier. (This arrangement is in opposite order from electroplating.) The finishing electrode is fitted to the-metal part to be finished in a spaced-apart relationship. A narrow gap must be maintained between the finishing electrode and the metal part to prevent short-circuiting. An electrolyte is then flowed through the gap formed between the finishing electrode and the metal part. A current is applied such that the current flows from the surface of the anode to the through the electrolyte to the face of the cathode. This flow effects removal of the rough material resulting in a rounded edge and smooth surface.  
         [0007]     According to a second known technique, a rotatable grinding wheel, such as an electrically conductive diamond-coated wheel, is provided for deburring. The grinding wheel is charged and acts as a cathode and the metallic, electrically-conductive surface to be ground functions as the anode. In operation, an electrolyte fluid is flowed between the grinding wheel and the sharp edge of the part being worked. Similar to the process mentioned above which relies only on electrochemistry, the mechanical-electrochemical process utilizes a rectifier to provide the desired charges to the anode and cathode.  
         [0008]     While the known techniques have provided advancements in the art of finishing parts made from conductive metals, there yet exists opportunities to improve the state of the art. Accordingly, the present invention provides an alternative method of finishing a metallic wheel that is both efficient and cost-effective and provides a further advancement in the state of the art.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides an efficient method and apparatus for finishing an electrically conductive part through electrochemistry. The present invention utilizes a cathode electrode that is configured so as to fit simultaneously in one or more windows or pockets or in a combination thereof. In an alternative embodiment of the present invention a disc-covering cathode electrode is provided that can simultaneously finish all of the windows and pockets using an electrolyte.  
         [0010]     In the first embodiment an electrode having an external shape that substantially mirrors the interior walls of a window or pocket (the “B” face) is provided for fitting within one or more of the window or pocket. (It should be noted that some wheels have only windows, some wheels have only pockets, while others have a combination of pockets and windows.) In this embodiment the finishing or deburring activity may be limited by either insulating the part being finished (the anode), by adjusting the gap between the anode and the cathode, or both. The individual or plural electrodes are fitted to a fixture in a known manner.  
         [0011]     In the second embodiment a disc-fitting electrode is provided having a part-facing surface that is configured so as to have window-mating and pocket-mating features formed thereon. As with the individual electrode arrangement set forth above, the finishing activity may be limited by either insulating the part being finished, by adjusting the gap, or both. According to this embodiment, both the B faces of the windows and of the pockets as well as the front surface of the wheel disc (the “A” face) can be finished simultaneously.  
         [0012]     According to the present invention, rapid and consistent finishing of metal parts, particularly aluminum alloy vehicle wheels, may be achieved. The present invention also provides for improvements in control of the anode electrode (the part) with respect to the cathode electrode. Other advantages and features of the invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and the appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     For a more complete understanding of this invention, reference should now be made to the embodiment illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein:  
         [0014]      FIG. 1  shows a perspective view of a portion of a metal article in the form of a vehicle wheel with an electrode in spaced-apart relation thereto;  
         [0015]      FIG. 2  shows a sectional view of a vehicle wheel before undergoing the finishing process of the present invention;  
         [0016]      FIG. 3  shows a sectional view of the electrode and vehicle wheel of  FIG. 1  with the electrode being positioned adjacent the vehicle wheel shown in sectional view in  FIG. 2 ;  
         [0017]      FIG. 4  shows a view of the vehicle wheel similar to that of  FIG. 2  but illustrating the burrs having been removed; and  
         [0018]      FIG. 5  shows a top plan view of a full wheel disc-covering electrode.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for one constructed embodiment. These specific parameters and components are included as examples and are not meant to be limiting.  
         [0020]     Referring now to  FIG. 1 , a perspective view of an electrode, generally illustrated as  10 , is shown in spaced-apart relation to an electrically conductive metal article, in this case a vehicle wheel, shown in partial view and generally illustrated as  20 . The electrode  10  may be produced from any number of known conductive materials, including brass or copper. The electrode  10  includes a body  12  and a power lead  14 . The lead  14  is connected to a rectifier (not shown in  FIG. 1 , but shown in  FIG. 3 , discussed below).  
         [0021]     The wheel  20  may be composed of any electrically conductive material as is know to those skilled in the art, but is typically formed or machined from aluminum alloy. The wheel  20  typically includes at least one window  22  (formed or machined through the wheel  20 ) and often includes at least one pocket or blind window  24 . As illustrated, the pocket  24  is not formed or machined completely through the wheel  20 .  
         [0022]     The surface area formed or machined between the window  22  and the pocket  24  is typically substantially flat and is referred to as the “A” face in the industry. The “A” face in the wheel  20  is “A” face  26 . The surface formed or machined on the walls of the window  22  is referred to as the “B” face in the industry. The “B” face in the wheel  20  is “B” face  28 . A power lead  30  is connected at one end to the wheel  20 .  
         [0023]      FIGS. 2 through 4  illustrate the vehicle wheel  20  before, during and after undergoing the process of the present invention. With respect first to  FIG. 2 , the wheel  20  is shown in sectional view. As seen in this view, a number of edges exist that are remnants of the wheel formation process. Specifically, an edge  32  is formed or machined between the A face  26  and the B face  28 . An edge  34  is also formed or machined between the B face  28  and the inner wall of the wheel  20 . In addition, an edge  36  is formed or machined around a valve seat  38  which forms the opening for an air valve hole  40 . The air valve hole  40  passes through the wheel  20 .  
         [0024]     The edges  32 ,  34  and  36  are relatively sharp and have burrs. While the object of the present invention is primarily one of polishing, deburring occurs as a by-product of the polishing operation.  
         [0025]     Prior to treatment in accordance with the present invention, a valve hole plug  42  formed from a polymerized composition such as rubber is inserted into the valve seat  38  to restrict passage thereby of the electrolyte discussed below. After processing, the valve hole plug  42  is removed. As illustrated, the valve hole plug  42  has a concave upper surface, but it is to be understood that the upper surface could be flat as well or could take on any other configuration as is known in the art.  
         [0026]      FIG. 3  illustrates the electrode  10  in position relative to the wheel  20 . The B face  28  of the window  22  is adjacent to a surface  44  formed on a wall of the electrode body  12 . As is clear from the illustration, a gap appears between the B face  28  of the window  22  and the surface  44  of the electrode  10 . The gap may be adjusted to control the amount of finishing activity as is known in the art. Typically, however, a gap in the range of between 0.01″ and 0.15″ would be suitable.  
         [0027]     An electrolyte flows in the gap created between the electrode  10  and the wheel  20 . The electrolyte may be selected from the group consisting of sodium chloride, sodium nitride, sodium nitrate, or sodium sulfate as is known to those skilled in the art. The electrolyte may be applied through flowing processes, spraying, or by dipping the vehicle wheel  20  and the electrode  10  into an appropriate vat.  
         [0028]     During the machining process the resulting edge may be sharper than desired. To deburr and to otherwise finish the edge  32 , a lip  46  is formed extending from the body  12  of the electrode  10 . The lip  46  is spaced apart from the edge  32  by a gap  48 . The gap  48  may be in the range of between 0.01″ and 0.15″ according to the amount of material that is to be removed from the edge  32 . The wider the gap  48 , the less material will be removed from the edge  32 . The width of the gap  48  may be selected depending upon the desired sharpness of the edge  32 . While the electrode  10  is illustrated as having the lip  46 , it is not necessary that the lip  46  be present for the successful operation of the method. The lip  46  may be desirable or even mandatory in those instances where the edge  32  must be well-curved with a large radius. Conversely, where the edge  32  need not have a large radius, the lip  46  is not needed.  
         [0029]     While the present invention is directed to polishing, it is important to note that deburring is a bi-product of the polishing operation. This arrangement offers many improvements over the prior art. By way of example, and with reference still to  FIG. 2 , according to known methods, the external edges of the valve hole  40  must be manually deburred. As with all other deburring procedures done by hand, the results are inconsistent. (For example, when the surface of the wheel  20  is deburred by conventional manual methods, the resulting surface is often uneven. This procedure is also very time-intensive.) According to the present invention, deburring of the edges of the valve hole  40  (along with the other edges) takes place during the polishing process, so is a desirable by-product of the polishing process. The present process thus provides for a consistent radius over all of the deburred edges which is a significant improvement over known manual deburring methods.  
         [0030]     Still with reference to  FIG. 3 , during the process of the present invention the edges  32  and  34  are deburred while the polishing process is undertaken. Accordingly, smooth and even edges are formed along the surface of the entire wheel  20 .  
         [0031]      FIG. 4  illustrates the wheel  20  after undergoing the process of the present invention. It will be noted that the edges  32 ,  34  and  36  are now smooth and uniformly rounded.  
         [0032]     Other control factors that determine the amount of material to be removed from the wheel  20  include adjusting the level of the DC current, adjusting the voltage, adjusting the concentration and flow rate of the electrolyte solution, and adjusting the dwell time (the exposure time) of the part to be finished to the electrolyte solution.  
         [0033]      FIG. 5  illustrates a plan view of a full-covering electrode, generally illustrated as  40 . The electrode  50  includes a plurality of outwardly-extending, window-fitting extensions  52 ,  52 ′,  52 ″,  52 ″′,  52 ″″ and a like plurality of outwardly-extending, pocket-fitting extensions  54 ,  54 ′,  54 ″,  54 ″′,  54 ″″. A surface  56  of the electrode  50  is formed between the window-fitting extensions  52  . . .  52 ″″ and the pocket-fitting extensions  54  . . .  54 ″″. The surface  56  is generally opposed to the A face of the vehicle wheel to be finished. Of course, the electrode  40  may be configured so as to embody a different configuration of window-fitting extensions and pocket-fitting extensions as required to match a particular vehicle wheel.  
         [0034]     Each of the window-fitting extensions  52  . . .  52 ″″ and the pocket-fitting extensions  54  . . .  54 ″″ includes side faces which oppose the B faces of the wheel when the electrode  40  is positioned over a wheel (not shown). A gap is defined between the faces of the electrode  40  and the wheel. This arrangement allows for electrolyte to flow through the gap. The flow rate of the electrolyte may be controlled and the gap may be adjusted as desired to determine the amount of material to be removed from the wheel as described above. In addition, other variables related to the electrolyte itself may be adjusted (concentration and dwell time) as needed.  
         [0035]     The present invention has a broad application to a great variety of wheel configurations regardless of the embodiment used. The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.