Abstract:
Cathode plate edge protector systems formed by secondary and tertiary molding processes, in which fluid plastic is molded around and/or introduced into previously manufactured plastic edge protectors. A U-shaped edge protector system is formed by bevel-cutting abutting ends of edge protector strips, securing the strips in the desired configuration a molding jig, and molding corner pieces around the abutting ends. The system is then removed from the jig and slip-installed over the two sides and the bottom edge of a cathode plate. In an optional tertiary molding process, fluid plastic may be introduced into the remaining void between the edge protector system and the cathode plate. Another edge protector system is formed by mounting edge protector strips on opposing side edges of a cathode plate, damming the open ends, and introducing fluid plastic in the contained voids between the strips and the cathode plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to non-metallic protective coverings for the edges of cathode plates used in electrowinning processes. More specifically, the invention pertains to cathode plate edge protector systems formed by secondary and tertiary molding processes, in which fluid plastic is molded around and/or injected into previously molded plastic edge protectors. 
     2. Description of the Prior Art 
     The two processing methods used for producing copper are: pyrometallurgy, or smelting, and hydrometallurical leaching. The present invention pertains to the latter method, in which copper bearing ore is pulverized and placed on a leach pad. A weak solution of sulfuric acid is sprayed onto the upper surface of the pulverized ore. The acid solution percolates through the ore, dissolving the acid-soluble copper. The solution is collected in a pond beneath the leach pad. 
     In the next step, the copper-bearing solution is pumped from the pond to a solvent extraction facility. At this facility, organic chemicals are mixed with the solution, separating the copper into a more concentrated solution. This concentrate is then mixed with sulfuric acid, forming an electrolyte solution. 
     The final step is the electrowinning process, an electrolytic method used to remove heavy metal ions from concentrated solutions. The copper electrolyte is pumped from the extraction facility into a steel tank at the electrowinning facility. Rows containing alternating cathode and anode plates extend throughout the volume of the tank. The cathode plates are made from stainless steel and the anode plates are made from lead. The plates are vertically suspended, so as to be substantially immersed in the copper electrolyte. The upper ends of the cathodes and the anodes are welded to horizontal hanger bars, which overlay respective electrical buss lines. The buss lines are interconnected to a source of low voltage, high current, DC. The copper ions are reduced through the electolytic process, and deposited as a layers of copper covering the cathode plates. After a week, or so, the cathode plates are removed from the electrolyte and an electroplated copper sheet is stripped from each side of the stainless steel cathode plates. 
     During this electrowinning process, the copper deposits along the edges of the cathode grow faster and sometimes in a more irregular fashion, that on the planar portions. This causes problems in removal of the copper sheets, as the edge deposited copper is thicker and of varying shape. The prior art teaches the use of non-conductive edge protectors, which extend along the side edges and the bottom edge of the cathode. The edge protectors cover the edges and a small adjacent strip of the planar portion of the cathode. In this way, no copper is deposited onto the edges of the cathode, and a clean line is presented by the inner edge of the edge protector for easy removal of the copper sheet. 
     Many different designs for these edge protectors have been developed. For example, U.S. Pat. No. 5,690,798, granted to Alexander et al., shows a corner protector for an electrowinning electrode. In this arrangement, a corner protector is located at each corner of the electrode, covering the region where each side edge strip and the bottom edge strip meet in abutting relation. Each corner protector has a vertical channel for receiving the lower end of a side edge strip, a horizontal channel for receiving the end of the bottom edge strip, and a cutout for receiving the corner of the cathode element. 
     However, the electrolytic process produces heat and expansive forces which compromise the integrity and useful life of prior art edge protectors. Adhesives fail, leaks develop, and deposits eventually form inside the cracks and the cavities of the prior art edge protector systems. When the deposits form in these regions, the edge protectors bulge outwardly and allow further intrusions of the electrolyte. Then, the sheets of deposited copper are difficult to remove, or are damaged during removal, and the cathode plate requires servicing before it can be used again. 
     Therefore, the need exists for a cathode edge protector system which does not rely upon adhesives, retainer strips, or other mechanical connectors, for attachment to the cathode. 
     The need exists for a cathode edge protector system incorporating a corner protector molded in situ on the end of one or more edge strips. 
     The need also exists for a cathode edge protector system which contains no external cracks or defects, or any internal voids, into which electrolyte can seep or intrude. 
     The need further exists for a cathode plate edge protector system in which edge strips can be preliminarily molded into any desired shape, mounted onto an edge of a cathode plate, and subsequently filled with fluid plastic for structural integration with the cathode plate. 
     SUMMARY OF THE INVENTION 
     The cathode plate edge protector systems of the present invention are formed by carrying out secondary and tertiary molding processes in conjunction with previously molded or extruded plastic edge protector strips. The first embodiment, a U-shaped edge protector system, is formed by first bevel-cutting the four abutting ends of three edge strips. The strips are then installed into a molding jig to form a U-shaped assembly. The molding jig includes right-angle cavities surrounding the two corners of the assembly. Lastly, fluid plastic is introduced into the cavities, molding plastic corner pieces around the abutting ends of the edge strips, and forming a unitary structure. 
     The edge protector system is removed from the jig and prepared for installation over the two side edges and the bottom edge of a cathode plate. The cathode plate includes a plurality of plate apertures arranged in spaced relation along its opposing first and second side edges. First and second plastic retainer strips, including a plurality of liked-spaced registration pins on their undersides, are installed along the side edges with the pins fitted into respective apertures. 
     A second edge protector system is formed by mounting an edge protector strip on the side edge a cathode plate, without a retainer strip. After damming the open ends, a fluid curable into a hardened body is introduced into the contained void between the edge strip and the side edge of the cathode plate. The process is repeated for the opposing edge. 
     A third edge protector system incorporates aspects of the first system and adds a tertiary molding process. The U-shaped edge protector system of the first system is formed, but it is merely slip-installed onto the cathode plate without using the retainer strips. Then, in a third tertiary molding process, fluid plastic is introduced into the contained void between the edge protector system and the cathode plate, filling the void within the edge protector system and the apertures in the cathode plate. A permanent and integrated structure between the edge protector system and the cathode plate is thereby formed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first edge protector system, mounted on a cathode plate with a hanger extending along its upper edge; 
     FIG. 2 is a fragmentary, cross-sectional, detail inset, taken on the broken line  2 — 2  in FIG. 1, showing the retainer strip and the covered portion of the cathode plate in broken line; 
     FIG. 3 is a cross-sectional view taken on the line  3 — 3  in FIG. 2; 
     FIG. 4 is a fragmentary, exploded view of a cathode plate and a retainer strip, showing the plate aperture and the registration pin; 
     FIG. 5 is a perspective view of a cathode plate, showing the installation of retainer strips with their registration pins aligned for insertion into respective apertures in the cathode plate; 
     FIG. 6 is an exploded perspective view, showing the first step of a corner piece molding process, with a side edge protector strip and a bottom edge protector strip being installed in the lower half mold with their beveled edges arranged in abutting relation; 
     FIG. 7 is a perspective view showing the second step of a corner piece molding process, the mold halves being closed upon the protector strips and the fluid plastic injection nozzle being introduced to an injection passageway; 
     FIG. 8 is a perspective view showing the third step of a corner piece molding process, the mold halves being separated and the unitary edge strips and the molded corner being removed from the lower half mold;. 
     FIG. 9 is a fragmentary, exploded, perspective view showing the beveled ends of the second side edge strip and the second end of the bottom edge strip, prior to installation into a lower mold half for forming a second molded corner; 
     FIG. 10 is a perspective view of a cathode plate fitted with the retainer strips, the first edge protector system in the process of being slip-installed over the side edges; 
     FIG. 11 is a perspective view of a cathode plate fitted with a second embodiment of an edge protector system; 
     FIG. 12 is a fragmentary, cross-sectional detail inset taken on the broken line  12 — 12  in FIG. 11, showing a molded locking body and the covered portion of the cathode plate in broken line; 
     FIG. 13 is a cross-sectional view taken on the line  13 — 13  in FIG. 12; 
     FIG. 14 is a perspective view of the first step of a locking body molding process, the cathode plate being fitted with the pair of side edge protector strips; 
     FIG. 15 is a fragmentary, perspective view of the second step of the molding process of FIG. 14, showing the bottom end injection mold forms and the upper end dam; 
     FIG. 16 is a fragmentary, perspective view of a side edge protector strip, showing a locking body which is molded within the side edge protector strip, and the cathode plate about which and through which the locking body is molded; 
     FIG. 17 is a perspective view of a cathode plate fitted with a third embodiment of an edge protector system, showing the injection mold forms on one top end and the dam on the other top end; 
     FIG. 18 is a fragmentary, cross-sectional, detail inset taken on the broken line  18 — 18  in FIG. 17, showing a molded locking body and the covered portion of the cathode plate in broken line; 
     FIG. 19 is a cross-sectional view taken on the line  19 — 19  in FIG. 18; 
     FIG. 20 is a cross-sectional view taken on the line  20 — 20  in FIG. 17; 
     FIG. 21 is a fragmentary, cross-sectional detail inset of an alternative, tubular form of an edge protector strip, showing a molded locking body and the covered portion of the cathode plate in broken line; and, 
     FIG. 22 is a cross-sectional view taken on the line  22 — 22  in FIG.  21 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, and in particular FIG. 1, a U-shaped edge protector system  11  for a cathode plate  12  is shown. Edge protector system  11  comprises a first side edge strip  13  and a second side edge strip  14 , preferably molded or extruded from a plastic material. First side edge strip  13  has an upper end  16  and a lower end  17 , and an inner, open side portion  18  extending therebetween. Lower end  17  includes a bevel termination  19 . Similarly, second edge strip  14  has an upper end  21 , a lower end  22 , and an inner, open side portion  23  extending between ends  21  and  22 . The lower end  22  of second edge strip  14  is also provided with a bevel termination  24 . 
     Also provided is a bottom edge strip  26 , having an first end  27  with a bevel termination  28 . Bevel termination  28  is adapted for mating engagement with bevel termination  19  of the first side edge strip  13 , forming a first juncture  29 . Bottom edge strip  26  also includes a second end  31  with a bevel termination  32  adapted for mating engagement with bevel termination  24  of the second side edge strip  14 . A second juncture  33  is thereby formed, as shown in FIG.  1 . Bottom edge strip  26  also has an inner, open side portion  34 , extending between the first end  27  and the second end  31 . 
     To complete formation of the U-shaped edge protector system  11 , first side edge strip  13  and bottom edge strip  26  are placed within a lower corner mold  36  with their respective bevel terminations in aligned, abutting relation. Then, as shown in FIG. 7, an upper corner mold  37  is lowered over the lower corner mold and the captive edge strips, and is clamped securely thereon. Both the upper and the lower corner molds include recesses  38  to accommodate respective portions of the edge strips, and they also include a corner cavity  39  surrounding the ends of the edge strips and the first juncture  29 . A passageway  41  extends through the interface of both molds, allowing the introduction of a fluid which is curable into a hardened form. Preferably, this is a plastic material, identical to the material previously used to mold or extrude the side and bottom edge strips. A plastic injection nozzle  42  is inserted into passageway  41 , and the fluid plastic is introduced into passageway, entirely filling the corner cavity  39 . 
     It should be noted that while an injection molding process is primarily referred to herein for the molding and formation of the fluid plastic, other equivalent processes may be used. For example, if the plastic material is made less viscous through the use of additives or elevated temperatures, the fluid plastic may be poured or introduced under low pressures into the various cavities and molds described herein. This approach may be desirable for safety reasons, as well as for ease and speed of production. Thus, the disclosure herein contemplates that the different molding processes may be carried out by injection molding under relatively high pressure, or it may be carried out by pouring the fluid material or introducing it into the edge strips or mold cavities under low pressure. 
     After a period of time has passed, the introduced fluid material cures into a hardened form, and the upper corner mold  37  may be removed. When the first side edge strip and the bottom edge strip  26  are removed from the lower corner mold, it is evident that a first molded corner piece  43  has been molded over the first juncture  29  (See, FIG.  8 ). This secondary molding process structurally integrates the previously molded edge strips through the use of a corner piece molded in situ over the mating juncture of the two edge strips. An identical secondary molding process is performed at the other corner of the system, where second side edge strip  14  conjoins with the second end  31  of bottom edge strip  26 . (See, FIG.  9 ). A second molded corner piece  44  is molded over the juncture  33 , and the major components of the U-shaped edge protection system  11  have been formed. 
     Attention will now be directed to the details of the cathode plate  12 , onto which the edge protection system  11  is installed. The cathode plate  12  includes a top edge  46 , a bottom edge  47 , and first side edge  48  and second side edge  49  extending therebetween. Side edges  48  and  49  include a plurality of plate apertures  51 , arranged in spaced relation substantially along their full extent. A first retainer strip  52  and a second retainer strip  53  are provided for installation, respectively, over first side edge  48  and second side edge  49 . Each retainer strip includes a plurality of registration pins  54 , depending from their undersides. The registration pins  54  are arranged in spaced relation, for snug insertion into respective plate apertures  51 . In that manner, retainer strips  52  and  53  are installed onto cathode plate  12 . (See, FIG.  5 ). 
     To complete the installation of edge protection system  11  onto cathode plate  12 , the open side portion  18  of the first side edge strip  13 , and the open side portion  23  of the second edge said second side edge strip  14 , are respectively slip-installed over the first retainer strip  52  and the second retainer strip  53 , until the bottom edge of cathode plate is inserted into the open side portion  34  of the bottom edge strip  26 . (See, FIGS.  1  and  10 ). 
     As is shown in FIGS. 2 and 3, the open side portions of the edge strips include an inner cavity  56  to accommodate both the edges of the cathode plate and the retainer strips mounted thereon. Inner cavity  56  includes a plate recess  57  sized and configured to receive said side edge of said cathode plate. Cavity  56  also includes a strip recess  58 , having upper portion and lower portions in communication with the plate recess  57 . Each retainer strip is housed within the upper portion of the strip recess  58 . It should be noted that the plate apertures  51  lie within the portion of the plate recess  57  which lies between the upper and lower portions of the strip recess  58 . Thus, the registration pins  54  extend downwardly from the retainer strips, pass through the plate apertures  51 , and enter the lower portion of the strip recess  58 . (See, FIG.  3 ). In this manner, confinement of the retainer strips  52  and  53  and their registration pins  54  within the strip recesses  58  of the side edge strips, coupled with the registration pins  54  passing through the plate apertures  51 , ensure that the edge strips and the cathode plate  12  are securely locked together, particularly against lateral movement. 
     As shown in FIG. 1, a hanger bar  59  extends across the upper edge  46  of the cathode plate  12 . The hanger bar is typically welded to the cathode plate, to provide a secure means of suspending the plate within the electrolyte. The hanger bar also lies upon electrical buss lines (not shown), to interconnect the cathode with the power supply. To facilitate periodic removal of the cathode plate from the electrolyte for copper harvesting, two hook holes  61  are provided in the upper end of the plate  12 . Because the hanger bar  59  closes off the upper side of the hook holes, the hooks removing the cathode plate actually lift against the hanger bar 
     Another embodiment of an edge protector system  62  is shown in FIG.  11 . This embodiment provides protection only for the side edges of a cathode plate  12 . Edge protector system  62  includes a first side edge strip  63  and a second side edge strip  64 . Both strips  63  and  64  are identical, having an upper end  66 , a lower end  67 , and an inner, open side portion  68  extending therebetween. Open side portion  68  includes an inner cavity  69  having a volume. 
     The cathode plate  12  used in connection with edge protector system  62  is identical to that previously described, so the same numerical designations will be employed for the sake of simplicity. Cathode plate  12  has a top edge  46 , a bottom edge  47 , and a first side edge  48  and a second side edge  49  extending therebetween. The first and second side edges include a plurality of plate apertures  51  extending through the cathode plate. The apertures  51  are arranged in spaced relation along the cathode plate edges, as shown in FIGS. 14 and 16. 
     In a first step in assembling the system  62 , the first side edge strip  63  is installed over the first side edge  48  of the cathode plate  12 . (See, FIG.  14 ). Preferably, after this step is completed, the cathode plate and the strip  63  are held in place securely by means of a jig or other suitable clamping apparatus. The first side edge  48  fills only a portion of the volume of the inner cavity  69  within the first side edge strip. It should be noted, in addition, that the open side portion  68  of the first side edge strip  63  encloses the plate apertures  51  which extend along the first side edge  48 . 
     At this juncture, a dam  71  is installed over the upper end  66  of side edge strip  63 . This darn seals off the otherwise open end of the inner cavity  69 . At the lower end  67  of side edge strip  63 , an edge strip injection mold  72  is installed over portions of the strip  63  and the cathode plate  12 . Injection mold  72  is of split block construction for easy installation and removal. Mold  72  also includes an injection port  73 , having an inner passageway in communication with the inner cavity  69 . The previously described injection nozzle  42  is adapted for insertion into port  73 , for delivery of a fluid curable into a hardened form, into inner cavity  69 . Preferably, this fluid is an injection molded plastic, of the same material used in the previous manufacture of the side edge strips  63  and  64 . 
     Upon injection or introduction of the fluid into the inner cavity  69 , the remaining unfilled portion of the inner cavity  69 , primarily above and below the side edge of the cathode plate and within the plurality of plate apertures, is filled with fluid. When this fluid cures into a hardened form, a locking body  74  is formed. The configuration of the locking body  74  is particularly evident in FIG.  16 . Locking body  74  includes an upper strip  76 , a lower strip  77 , and cylindrical pins  78  extending therebetween. With the cylindrical pins  78  passing through the plate apertures, and the upper and lower strips filling the remainder of the inner cavity above and below the edge of the cathode plate, the side edge strip  63  and the cathode plate  12  are securely and permanently joined together. Then, upon removal of the darn  71  and the strip injection mold  72 , the identical process is repeated for mounting and securing remaining side edge strip  64  to the cathode plate  12 . 
     Yet another embodiment of the invention, comprising an edge protector system  79  is shown in FIG.  17 . This third embodiment is in many ways a combination of certain features of the first embodiment and the second embodiment, previously described. For that reason, where appropriate, many of the same numerical designations for various components will be used. In addition, where systems and assembly processes pertaining to these common components have already been discussed in detail, reference will simply be made to the previous discussion rather than repeating the same subject matter. 
     Edge protector system  79  includes a first side edge strip  81 , a second side edge strip  82 , and a bottom edge strip  83 . These edge strips are assembled into a U-shaped unitary structure, by means of the same secondary molding process described in connection with the first embodiment, represented by edge protector system  11 . Accordingly, edge protector  79  also includes a first molded corner piece  84  and a second molded corner piece  86 . Side strips  81  and  82 , as well as bottom edge strip  83 , all include an inner, open side portion  87  and an inner cavity  88 , identical to those corresponding features discussed previously. 
     Edge protector system  79  is slip-installed over the side edges and the bottom edge of cathode plate  12 , as shown in FIG.  17 . However, no retaining strips are installed along the side edges of the cathode plate, before the U-shaped unitary structure of system  79  is installed thereon. A dam  89  is provided at the upper end of the first side edge strip  81 . An injection mold  91  is provided at the upper end of the second side strip  82 . The entire assembly is held fast in a jig, or within clamps on an assembly table. 
     In a tertiary molding process, a fluid curable into a hardened form, is injected or introduced through the injection mold  91 , into the remaining unfilled portion of inner cavity  88 . This fluid is preferably a fluid plastic, identical or similar to that used previously to mold the edge strips and the corner pieces. As with the injection process described to make the edge protector system  62 , the introduced fluid fills the portion of the inner cavity  88  above and below the side edge of the cathode plate and within the plurality of plate apertures. When this fluid cures into a hardened form, a locking body  92  is formed. This locking body permanently secures the edge strip assembly to the cathode plate. 
     FIG. 19, a cross-sectional view taken through a plate aperture  51 , shows how the locking body  92  extends above, below, and through the side edge of the cathode plate  12 . FIG. 20, a cross-sectional view taken through a representative portion of the bottom edge strip  83 , shows how the locking body exists only above and below the bottom edge of the cathode plate  12 . In other words, since no plate apertures are normally provided along the bottom edge, the locking body in this region is so confined. 
     While all of the edge strips described so far have been generally rectangular in cross-section, other configurations may be used as well. For example, in FIGS. 21 and 22, an edge strip  93  which is circular in configuration is shown. Edge strip  93  has an inner, open side portion  94  which includes a right, circular cylindrical inner cavity  96 . As with the other edge strips, the cathode plate  12  passes through the open side portion  94  and into the inner cavity  96 . If the edge of the cathode plate includes a plate aperture  51 , the locking body  97  will extend above, below, and through the edge of the plate, as shown in FIG.  22 . 
     It will be appreciated, then, that I have disclosed three embodiments of improved cathode plate edge protector systems for cathode plates, and methods for making same, incorporating secondary and tertiary molding processes in conjunction with previously molded or extruded plastic edge protector strips. of the cathode plate and within the plurality of plate apertures. When this fluid cures into a hardened form, a locking body  92  is formed. This locking body permanently secures the edge strip assembly to the cathode plate. 
     FIG. 19, a cross-sectional view taken through a plate aperture  51 , shows how the locking body  92  extends above, below, and through the side edge of the cathode plate  12 . FIG. 20, a cross-sectional view taken through a representative portion of the bottom edge strip  83 , shows how the locking body exists only above and below the bottom edge of the cathode plate  12 . In other words, since no plate apertures are normally provided along the bottom edge, the locking body in this region is so confined. 
     While all of the edge strips described so far have been generally rectangular in cross-section, other configurations may be used as well. For example, in FIGS. 21 and 22, an edge strip  93  which is circular in configuration is shown. Edge strip  93  has an inner, open side portion  94  which includes a right, circular cylindrical inner cavity  96 . As with the other edge strips, the cathode plate  12  passes through the open side portion  94  and into the inner cavity  96 . If the edge of the cathode plate includes a plate aperture  51 , the locking body  97  will extend above, below, and through the edge of the plate, as shown in FIG.  22 . 
     It will be appreciated, then, that I have disclosed three embodiments of improved cathode plate edge protector systems for cathode plates, and methods for making same, incorporating secondary and tertiary molding processes in conjunction with previously molded or extruded plastic edge protector strips.