Abstract:
A corner insert for edge strips used with modified electrodes for electrolytic processes. An electrode that is at least partially submerged in an electrolyte is protected by edge strips to prevent depositions and metallic bridges. The edge strips are typically mitered to abut one another at the corners of the electrode and it is difficult to seal this junction. One solution is to remove the corners of the electrode, provide non-mitered edge strips, and close the gap at the corner with an insert adapted to seal to the additional edges of the electrode created by removing the comers. Another solution is to provide a corner insert having one or more anchors for anchoring the corner insert to the electrode and to respective adjacent edge strips, the corner insert sealing against the edge strips and against opposite sides of the electrode whether or not the corner portion has been removed. Yet another solution is to omit an edge strip at the bottom edge of the electrode, and provide an edge strip insert having an anchor for anchoring the edge strip insert to the electrode and to an edge strip which receives the anchor, the edge strip insert for sealingly seating against the edge strip and against opposite sides of the electrode whether or not the corner portion has been removed.

Description:
This application is a continuation-in-part of Ser. No. 09/579,653, filed May 26, 2000, now U.S. Pat. No. 6,312,573. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to electrolytic processes and apparatus for refining metals and, in particular, to an improved edge strip assembly for mother plates that have been modified by the removal of corner portions. 
     2. Description of the Prior Art 
     Electrolysis is utilized to extract metals and other cations from an electrolytic solution. The extraction process involves passing an electric current through an electrolyte solution of a metal of interest, such as copper, gold, silver, or lead. The metal is extracted by electrical deposition as a result of current flow between alternating anode and cathode plates immersed in cells of an extraction tank house. In electrowinning processes, a solution of metal-rich electrolyte is circulated through the extraction cells. The cathode is generally constructed of a metal alloy, such as titanium or copper alloys, and various grades of stainless steel which are resistant to corrosive acid solutions. Typically, each cathode consists of a thin sheet of metal of uniform thickness, e.g., 2-4 mm, disposed vertically between parallel sheets of anodic material, so that a uniform current density is maintained throughout the surface of the cathode. A pure layer of metal is electrodeposited on the cathode surface, which thus becomes plated during the process, upon passing of an electric current through the electrolyte. 
     Similarly, in refinery metal-purification processes, an anode of impure metal is placed in an electrolytic solution of the same metal and subjected to an electric current passing through the anode, the electrolyte and the cathode of each cell, The anode goes into solution, thereby separating the metal from impurities, which drop to the bottom of the tank. The electrical current then produces the deposition of the dissolved metal in pure form on the cathode, which typically consists of a mother plate of stainless steel. When a certain amount of pure metal has been plated onto the mother plate, the cathode is pulled out of the tank and stripped of the pure metal. 
     In both processes, the pure metal deposit is grown to a specific thickness in sheets deposited on each side of the cathode, and then the cathode is removed from the cell and stripped. For quality control purposes, it is very desirable that these sheet deposits be uniform in shape and thickness, so that they can be easily removed by automated stripping equipment. The overall economy of the production process, depends in part on the ability to mechanically strip the cathodes of the metal sheets at high throughputs and speeds without utilizing manual or physical intervention. To that end, the mother plates have a surface finish that is resistant to the corrosive solution of the tank house and is strong enough to withstand continuous handling by automated machines without pitting or marking. Any degradation of the finish of the blank causes the electrodeposited metal to bond with the cathode resulting in difficulty of removal and/or contamination of the deposited metal. 
     If deposition is allowed to occur at the edges of a cathode, metallic bridges form between the deposited sheets on either side of the cathode. These metallic bridges, which can wrap around the edges of the cathode, hinder the stripping operation and can cause damage to the sheets and/or the cathode. To alleviate this problem, nonconductive strips known as edge strips or protector strips are placed over the submerged bottom and side edges of the cathode. The edge strips are normally mechanically fixed to the cathode with glued pins or pin inserts. In addition to inhibiting the formation of metallic bridges, edge strips function to prevent direct contact between the cathode and the adjacent anodes. 
     As is well understood in the art, at each lower corner of a cathode the vertical edge strips, mounted on the side edges of the mother plate, define junctions with the horizontal edge strip mounted on the bottom edge. Often glue is applied to these junctions to prevent penetration of the electrolyte into, and an accompanying deposition of metal around, the junctions. However, over time, the glue develops cracks which permit leakage of the electrolyte into the junctions. Eventually, the edge strips must be removed to allow removal of deposits accumulated on the edge of the cathode in the junction areas. The process of removing the edge strips, cleaning the cathode and replacing the edge strips is time-consuming and also keeps the cathode out of service; therefore, it is very undesirable. 
     In order to further reduce the likelihood of electrolyte penetration into corner junctions, manufacturers have improved the fit between abutting parts of adjoining strips. This objective has required greater precision finishing of the edge strips and more accurate positioning of the strips on the cathode during installation, so that manufacturing as well as mounting costs have increased. To obtain a better fit, edge strips are sometimes also mitered, which further increases manufacturing and installation time. 
     U.S. Pat. No. 5,690,798 describes a corner protector designed to wrap around the side and bottom edge strips abutting at the lower corners of a mother plate. The protector has a vertical channel adapted to receive the lower end of a vertical edge strip, a horizontal channel adapted to receive an end of the bottom edge strip, and a cutout for the corner of the mother plate. Thus, the protector provides additional separation between the edges of the cathode and the electrolytic solution, but it involves the use of an additional component with attendant supply, installation and maintenance costs. 
     A notable improvement recently found in the art, based on a different approach to reducing electrodeposition at the lower corners of cathodes, has been to cut away the corner portions of the mother plate covered by abutting side and bottom edge strips. Thus, the accumulation of electrolyte deposits is avoided by eliminating the metallic substrate upon which deposition may occur. Unfortunately, though, electrolyte seepage still causes deposition along the edges of the cut-away corners covered by the edge strips. The use of caulking and/or binding material, such as silicone, to seal the abutting parts of adjoining edge strips delays but does not prevent the eventual penetration of electrolyte and accumulation of deposits. 
     Therefore, there is still a need for an improved system of cathode-edge protection designed to overcome these problems, especially the accumulation in the comer areas of the mother plate. The present invention provides a new edge-strip component that fulfills this need for mother plates that have been modified by the corner cut-away approach described above. 
     Another aspect of the present invention provides a new edge-strip component that fulfills this need for mother plates whether or not modified by the corner cut-away approach described above. 
     In one embodiment of the invention corresponding to this aspect, a corner insert is provided having one or more anchors for anchoring the corner insert to the electrode and to respective adjacent edge strips, the corner insert sealing against the edge strips and against opposite sides of the electrode whether or not the corner portion has been removed. 
     In another embodiment of the invention corresponding to this aspect, the edge strip at the bottom of the electrode is omitted and an edge strip insert is provided having an anchor for anchoring the edge strip insert-to the electrode and to an edge strip which receives the anchor, the edge strip insert sealing against the edge strip and against opposite sides of the electrode whether or not the corner portion has been removed. 
     SUMMARY OF THE INVENTION 
     The main object of the invention is an edge strip system that reduces the accumulation of electrolyte at the lower corners of cathode mother plates. 
     In particular, an object of the invention is a system intended for application with mother plates where the lower corners have been removed. 
     An additional object of the invention is to provide an accessory component suitable for use with existing side and bottom edge strips. 
     One more object of the invention is to provide a method of protecting the lower corners of an electrode assembly so as to enable operation for longer periods of time without cleaning. 
     A further object of the invention is to provide a system that can be implemented economically according to the above stated criteria. 
     According to the preceding objects, as well as others that will become apparent as the description proceeds, the invention consists of a nonconductive insert adapted to fill the void resulting from the absence of mother-plate corners wrapped within the abutting ends of side and bottom edge strips. In the preferred embodiment of the invention, the insert comprises a plate of dimensions commensurate with the metal corner removed from the mother plate, so that the resulting void is filled. The insert includes at least one anchor, preferably two, adapted to frictionally engage the end of a strip mounted along the edge of the mother plate. If two anchors are used, they are disposed at a right angle to make it possible to attach the insert to both edge-strip ends coming together at a corner of the mother plate. The insert and its anchors are designed to completely fill the void left by the missing mother-plate corner, thereby preventing penetration of electrolyte and accumulation of deposits. Additional protection and stability of assembly may be provided by bonding the insert to both adjoining edge-strip ends with glue. 
     According to other embodiments of the invention, the insert may be incorporated into the edge-strip end as an integral component of the strip. In such case, the end of the integrated insert may include a lateral anchor adapted for frictional engagement of the end of a conventional edge strip to form a corner junction. This design is particularly suitable for injection molded manufacture. When a single, vertical edge strip is used (bottom edge strips are sometimes not utilized), the lateral anchor is not necessary. 
     Thus, the insert of the invention, whether implemented as an accessory to or as an integral component of an edge strip, serves as a plug for the missing corner of a modified electrode and a filler for the resulting void left within adjacent corner ends of the side and bottom strips mounted on the edges of the mother plate. The insert prevents seepage of electrolyte to the corner site and to adjacent portions of the mother-plate edges encased in the edge strips, so that less frequent cleaning of the corner areas is required. 
     Another aspect of the invention resides in a method of making an electrolytic electrode assembly. The method comprises the steps of providing an electrode having a first edge, a second edge perpendicular to the first edge, and an insert corresponding to the removal of a corner portion at the intersection of the two edges; placing a first edge strip over the first edge so that an end thereof is in the region of the intersection; placing a second edge strip over the second edge so that an end thereof is in the region of the intersection, and replacing the missing corner portion of the electrode with an insert of nonconductive material confined by the ends of the first and second edge strips. The method can further comprise the step of adhesively connecting the insert to the ends of the edge strips. 
     Another aspect of the invention resides in a nonconductive insert that may be used for mother plates whether or not a corner of the mother plate has been removed. In one embodiment, the insert includes a corner member having an aperture that defines interior surfaces for seating against opposite sides of the mother plate, and is adapted to sealingly seat against an end of the edge strip. In another embodiment, the insert includes a corner member having an aperture that defines interior surfaces for seating against opposite sides and corner edges of the mother plate. 
     In yet another embodiment of the invention, a nonconductive insert may be used for plugging an edge strip having an end defining a cross-sectional circumference, the insert comprising a base from whose upper surface extend spaced-apart prongs, the prongs having interior surfaces adapted to seat, respectively, against the sides of the mother plate and the upper surface of the base adapted to seat against the end of the edge strip around substantially the entire length of the circumference. The base may include a slot therethrough, disposed between the interior surfaces of the prongs, so that the bottom edge of the mother plate may be flush with or extend beyond the bottom surface of the base. The base may also include a corner insert for filling the void in a mother plate which has had its corner removed. 
     Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose but one of the various ways in which the invention may be practiced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational, fragmentary view of a mother plate found in prior art where a corner section has been cut out to prevent accumulation of deposits resulting from electrolyte seepage into a corner junction of edge strips. 
     FIG. 2 is an end view of a conventional edge strip. 
     FIG. 3 is an elevational view of a corner junction between two mitered edge strips according to conventional practice. 
     FIG. 4 illustrates the void defined by the channels and slots of conventional edge strips when joined to form a corner junction over a modified mother plate. 
     FIG. 5 is an elevational front view of an insert according to the invention. 
     FIG. 6 is a side view of the insert of FIG.  5 . 
     FIG. 7 is a top view of the insert of FIG.  5 . 
     FIG. 8 is a top view of an edge strip including the insert of the invention, either as a separate component fitted into the end slot of the strip, or as an integral part thereof 
     FIG. 9 is a side view of the edge strip assembly of FIG.  8 . 
     FIG. 10 illustrates the edge strip assembly of FIG. 8 installed on the bottom edge of a modified mother plate. 
     FIG. 11 illustrates an edge strip of unitary construction with a solid end plug designed for vertical-edge applications where a bottom edge strip is not used. 
     FIG. 12 is an end view of the edge strip of FIG.  11 . 
     FIG. 13 is a sectional view of the edge strip of FIG.  11 . 
     FIG. 14 is an elevational, fragmentary view of the mother plate of FIG.  1  and edge strips according to another aspect of the invention. 
     FIG. 15 is an elevational, fragmentary view of the mother plate of FIG. 1, edge strips according to the present invention and a corner member according to the present invention. 
     FIG. 16 is a pictorial view of a first embodiment of an insert according to the present invention. 
     FIG. 17 is a pictorial view of the insert of FIG. 16 including a first embodiment of anchors according to the present invention. 
     FIG. 18 is a pictorial view of the insert of FIG. 16 including a second embodiment of anchors according to the present invention. 
     FIG. 19 is a sectional view of the insert of FIG. 16, taken along a line  19 — 19  thereof. 
     FIG. 20A illustrates an edge strip installed on a side edge of a mother plate so that the end of the edge strip is flush with the bottom edge of the mother plate. 
     FIG. 20B illustrates the edge strip of FIG. 20A displaced upwardly so that the end of the edge strip is no longer flush with the bottom edge of the mother plate. 
     FIG. 21A is an elevational right side view of a second embodiment of an insert according to the present invention. 
     FIG. 21B is an elevational front view of the insert of FIG.  21 A. 
     FIG. 21C is a top view of the insert of FIG.  21 A. 
     FIG. 22A is an elevational night side view of a third embodiment of an insert according to the present invention. 
     FIG. 22B is an elevational front view of the insert of FIG.  22 A. 
     FIG. 22C is a top view of the insert of FIG.  22 A. 
     FIG. 23A is an elevational right side view of a third embodiment of an insert according to the present invention. 
     FIG. 23B is an elevational front view of the insert of FIG.  23 A. 
     FIG. 23C is a top view view of the insert of FIG.  23 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The gist of the invention resides in the idea of providing a nonconductive insert to replace the portion of a mother-plate corner removed to avoid deposition of electrolyte at the corner junctions between side and bottom edge strips. For the purposes of this disclosure, the terms “modified electrode” and “modified mother plate” are intended to refer to conventional electrodes and mother plates where the bottom corners have been so removed. 
     Referring to the drawings, wherein like parts are referred to throughout with like numerals and symbols, FIG. 1 is a partial view of a modified mother plate  10  having a corner section  12  removed (shown in phantom line), as explained above. Conventional edge strips  14 , as illustrated in cross-section in FIG. 2, include a longitudinal channel  16  adapted to receive an edge  18  (or  20 ) of the mother plate in tight connection to prevent seepage of electrolyte inside the strip. A wider longitudinal slot  22 , running within the channel  16 , is provided to receive retaining opposite ends of pins  24  inserted through and protruding on both sides from the border of the mother plate. Each edge strip is installed on the mother plate by sliding the slot  22  over the pins  24 , so that the strip becomes engaged by the pins and firmly retained in place over the border of the electrode to protect its edge. The length of the pins  24  is preferably chosen to be approximately the same as the width of the slot  22  to ensure firm installation and durability of the resulting assembly. 
     Conventional strips are also often mitered at a 45-degree angle for corner junctions, as illustrated in FIG.  3 . Therefore, when these edge strips are installed on a modified electrode, the empty portions of channels  16  and slots  24  resulting from the missing section  12  of the modified electrode in adjoining ends of mitered edge strips create a void at the corner location, as approximately illustrated by the phantom-line circle  26  in FIG.  4 . When electrolyte penetrates the seal formed by the mitered surfaces of the edge strips abutting at the corner, damaging deposits form in the cavity produced by the structure of the modified electrode. 
     According to the present invention, a nonconductive insert  30 , shown in FIGS. 5-7, is provided to fill the cavity defined by the channels  16 , the slots  22 , and the cut-out corner edges  32  and  34  of the modified mother plate  10 . Accordingly, the insert  30  includes a plate  36  of dimensions substantially equal to the section  12  removed from the corner of the mother plate  10  for which the invention is intended, so that the insert  30  will fill the void created by its removal. In addition, the insert  30  includes orthogonal anchors  38  and  40  projecting in the directions of the slots  22  in the edge strips mounted on the side and bottom of the modified mother plate. As better seen in the side and top views of FIGS. 6 and 7, each anchor  38 , 40  is sized so that it can be press-fit around the edge of the mother plate  10  through the end of a corresponding slot  22 . Specifically, referring to the side view of FIG. 6, the opening  42  within two prongs of the anchor  38  is adapted to receive the edge  32  of the mother plate; and the opening  44  within two prongs of the anchor  40  is adapted to receive the edge  34  of the plate in tight frictional connection. Each prong is sized to fit in the longitudinal openings left in the slot  22  on either side of the mother plate after the edge strip is mounted on the plate. 
     FIGS. 8 and 9 illustrate in top and side views, respectively, the insert 30 of the invention as it would appear when inserted into a single edge strip  14 . FIG. 10 shows the same partial assembly mounted on the bottom edge of a mother plate  10 . As one can appreciate from these figures, it is clear that the further installation of a vertical edge strip by sliding it into position through the retaining pins  24  and the anchor  38  (in the slot  22 ) produces a compact corner assembly with essentially no residual empty space. In order to complete the elimination of interstices within the corner junction and further strengthen the assembly, a glue may be applied to all abutting surfaces during installation. Inasmuch as the insert  30  is made of nonconductive material, preferably the same as the main constituent of the edge strips, the edges  32  and  34  of the modified electrode are fully protected from electrical contact with the electrolyte solution and the corner sections are thereby durably prevented from accumulating metallic deposits. 
     In the preferred embodiment of the invention, the insert  30  is sized to fit a conventional edge strip of the type illustrated in FIG.  2 . Accordingly, the plate  36  is approximately 16 mm long, 16 mm wide, and 3 mm thick. The anchors  38 , 40  are about 20 mm long, 7 mm wide, and extend about 10 mm beyond the plate  36 . Each prong in the anchors is defined by a 3-mm opening ( 42 , 44 ) for receiving the edge ( 32 , 34 ) of a mother plate  10 . 
     The insert  30  of the invention has been described as a separate accessory component for use with conventional edge strips. On the other hand, the insert could be equivalently incorporated as an integral part of an edge strip of unitary construction. Such an embodiment would have exactly the same appearance of the assembly shown in FIGS. 8 and 9, but it would consist of a single-piece, preferably injection-molded, unit. 
     Similarly, an equivalent edge strip  50  of unitary construction, illustrated in FIGS. 11-13, is disclosed for vertical-edge applications where a bottom edge strip is not used. The strip  50  features a solid end plug  52  (seen in FIG. 11) designed to replace the corner section  12  removed from the modified mother plate  10 . Accordingly, the end view of the strip shows a solid flat surface, as seen in FIG.  12 . Otherwise, the strip  50  retains the same structural features of a conventional edge strip, including a channel  16  for receiving the edge of the mother plate and a slot  22  (seen in the cross-section of FIG. 13) for retaining pins  24 . 
     As described above, an insert according to the invention is provided that fills the void that is created inside abutting edge strips by removing a corner portion  12  of the mother plate  10 . In another aspect of the invention, which is described immediately below, the invention provides for sealing portions of the perimeter of the mother plate that are left unprotected by edge strips which are not abutting. The corner portion may or may not be removed from the mother plate. 
     With reference to FIG. 14, edge strips  60  that sealingly receive edges  18  and  20  of the mother plate  10  need not extend into the space  62  (shown in phantom lines) that is defined by removing the corner  12  of the mother plate. This eaves the space  62  open for receiving an insert that connects between the edge strips  60  and seals with the remaining perimeter of the mother plate  10  that is associated with this space. 
     Turning to FIG. 15, a preferred insert  70  according to the present invention includes a comer member  72  of suitable dimensions for tightly connecting between edge strips  60   a  and  60   b . Preferably, the comer member  72  of the insert  70  is formed of the same material as the edge strips, or is formed of a material or includes a material at edges  71  that abut the edge strips that is suitable to seal therewith so as to inhibit the formation of metallic bridges on the mother plate due to electrolyte penetration into corner junctions. 
     Turning to FIG. 16, the insert  70  further includes an aperture  73  in the corner member adapted to receive the thickness of the mother plate  10 , the aperture having sealing edges  84  for forming a suitable seal with the edge strips  60 . The aperture also includes internal sealing surfaces  75  for sealing with the edges  32  and  34  of the mother plate  10 . The sealing edges and surfaces may simply be the termination of the surfaces defining the aperture  73  as depicted, or they may be especially adapted for forming the seal, e.g., by being formed of a different material or by having a specialized geometry. 
     Turning to FIG. 17, the insert  70  preferably includes anchors  74 ,  76 , for anchoring the corner member  72  to the mother plate. Each anchor is sized so that it can be press-fit around the edge of the mother plate  10 . This improves sealing between the insert and the mother plate, and provides a strong mechanical connection. 
     With further reference to FIG. 2, where the edge strips  60  include a channel  16  for receiving the edges  18  and  20  of the mother plate and a longitudinal slot  22 , the anchors  74  and  76  may be adapted to fit snugly into the longitudinal slots  22  of respective edge strips. For this purpose, the anchors are provided with two parallel members, e.g.,  74   a  and  74   b  which are spaced apart to permit snugly receiving the thickness of the mother plate  10 , the parallel members being received in respective portions  22   a ,  22   b  of the slot  22 . 
     Turning to FIG. 18, the parallel members  74   a  and  74   b , and/or  76   a  and  76   b , may be joined at respective outside edges  74   c ,  76   c  to form a closed corner. By comparing FIGS. 17 and 18, it is seen that the width of the parallel members is arbitrary within limits set by, on the one hand, the mechanical stiffness of the parallel members and, on the other, the size of the corner member  72 . 
     Turning to FIG. 19, the aperture  73  in the corner member preferably extends a depth “d” into the corner member  72  to form a channel that may be press-fit around the edges  32  and  34 . The insert  70 , when joined to the edge strips  60   a  and  60   b  and when receiving the mother plate  10  with the corner  12  removed, produces a compact corner assembly with minimal residual empty space. As will be readily appreciated, the aperture  73  may be alternatively shaped to accommodate a corner section  12  of different geometry, or may be enlarged to accommodate a mother plate  10  that has not had the corner section  12  removed. 
     For example, in FIG. 19, the mother plate  10  includes a side edge  18  and a bottom edge  20 , which meets two corner edges  92   a  and  92   b  at respective points C 1  and C 2 . The corner edges meet at a point C 3  between the points C 1  and C 2 . The edges  92  are not collinear with the respective side and bottom edges. Alternatively, there may be additional corner edges defining additional points Cn between the points C 1  and C 2 , e.g, between the points C 3  and C 1 , and/or between C 3  and C 2 , and the angles between the corner edges need not be perpendicular. Where the corner section  12  has not been removed, the corner edges  92  are collinear with the respective side and bottom edges. As in the case of the embodiment  30  of FIG. 5, a glue or sealant may be applied to all abutting or mating surfaces and to fill any remaining gaps or interstices to further seal and strengthen the assembly. 
     It is sometimes desirable not to provide an edge strip on the bottom edge  20  of the mother plate, and therefore to protect with edge strips only the two opposite sides of the plate. For example, the bottom edge  20  of the plate may be left open to ride on a chain. Edge strips  60  installed on a side edge  18  (FIG. 1) of the mother plate are positioned most advantageously so that ends  79  thereof are flush with the edge  20  as shown in FIG.  20 . However, as a result of the rough treatment that the mother plate often receives in industrial use, the side edge strips can shift in position, typically sliding upwardly and leaving portions of the side edge  18  (FIG. 1) unprotected as shown in FIG.  20 B. 
     Referring back to FIGS. 1 and 2 and as mentioned above, the edge strips typically have a longitudinal slot  22  running within the channel  16 . Another problem posed by omission of the bottom edge strip is that this slot provides a conduit for conducting electrolyte to the mother plate. 
     Referring generally to FIGS. 21A-23C, to address these problems, yet another aspect of the invention provides edge strip inserts  80  that are especially adapted to close the ends of side edge strips when no bottom edge strip is provided, to provide a reliable and durable seal with the mother plate along the side edges thereof. The inserts  80  may be provided in a number of alternative configurations, such as (a) those particularly adapted for an edge strip that is attached to the mother plate so that its end  79  is not flush with the bottom edge of a mother plate that does not have section  12  (FIG. 1) removed from the corner of the mother plate; (b) those which are adapted for an edge strip that is attached to the mother plate so that its end is flush with the bottom edge of a mother plate that does have section  12  removed from the corner of the mother plate; (c) those which are adapted for an edge strip that is attached to the mother plate so that its end is flush with the bottom edge of a mother plate that does not have section  12  removed from the corner of the mother plate; and (d) those which are adapted for an edge strip that is attached to the mother plate so that its end is not flush with the bottom edge of a mother plate that does have section  12  removed from the corner of the mother plate. 
     Referring to FIGS. 21A-21C, an insert  80 ( a ) is shown corresponding to the configuration (a) above. The insert  80 ( a ) includes a base  82   a  having a slot  84   a , and an anchor comprising two parallel prongs  86   a  and  88   a  projecting from a top surface  81   a  of the base and disposed about the slot so that inner surfaces  85   a  of the prongs are flush with corresponding sides  87   a  of the slot. The spacing “t” between these surfaces is ideally equal to the thickness of the mother plate, so that these surfaces may snugly receive the mother plate between the prongs, the bottom edge  20  (FIG. 1) of the mother plate extending to or beyond a bottom surface  83   a  (FIG. 21B) of the base through the slot. 
     Though it is less desirable, configuration (a) may also be implemented by providing a slot extending from the top surface into but not through the base, or by replacing the slot with a surface that is elevated with respect to the top surface of the base on which the edge  20  of the mother plate may rest, all without departing from the principles of the invention. 
     Turning back to FIGS. 1 and 2 and as mentioned previously, the longitudinal slot is provided to receive ends of pins  24  inserted through and protruding on both sides from the border of the mother plate  10 . According to the invention, the insert or longitudinal slot is adapted in shape and size so that right and left side portions  22   a  and  22   b  (FIG. 2) of the longitudinal slot snugly receive the prongs  86   a  and  88   a.    
     Also as mentioned previously, the pins  24  have been inserted through corresponding holes in the mother plate; however, according to the invention, at least one of these pins is preferably omitted leaving a corresponding empty hole, and the inserts  80   a  are adapted to take advantage of the existence of this hole. Particularly, one of the prongs  86   a  includes a pin  89   a  adapted in shape and size to project into and preferably through the empty hole in the mother plate when the mother plate is received between the surfaces  85   a  and  87   a , to fill and seal the hole from electrolyte as well as provide a means for anchoring the insert  80   a  to the mother plate and, thereby, for anchoring the edge strip to the mother plate as described immediately below. 
     Because the edge strips are typically very stiff, it is most advantageous to install the insert onto the mother plate first, e.g., by spreading the prongs apart sufficiently so that the pin  89   a  clears the surface of the mother plate until the pin is positioned for insertion into the hole in the mother plate, and then to install the edge strip, e.g., by sliding the edge strip down along the side edge of the mother plate so as to engage the prongs in the respective portions  22   a ,  22   b  (FIG. 2) of the longitudinal slot, and finally abutting the end  79  (FIGS. 20 a  and  20   b ) of the edge strip snugly against the top surface  81  a of the base  82   a . The top surface of the base seals against the end  79  along substantially the entire circumference “C” of the end  79  (FIG.  2 ), to prevent seepage of electrolyte into the slot  16  and longitudinal channel  22 . 
     Turning to FIGS. 22A-22C, an insert  80 ( b ) is shown corresponding to the configuration (b) above. The insert  80 ( b ) includes a base  82   b  having a corner section  92   b  and an anchor comprising two parallel prongs  86   b  and  88   b  projecting from top surface  81   b  of the base and disposed about the corner section so that inner surfaces  85   b  of the prongs are flush with corresponding faces  94   b  of the corner section. The corner section  92   b  is shaped to fit the section  12  (FIG. 1) that has been removed from the mother plate. The thickness of the corner section and the spacing “t” between the surfaces  85   b  is ideally equal to the thickness of the mother plate, so that the surfaces  85   b  snugly receive the mother plate between the prongs. Edge surfaces  96   b  and  98   b  of the corner section abuttingly receive edges  32  and  34  (FIG. 1) respectively of the mother plate, the bottom edge  20  (FIG. 1) of the mother plate extending to the top surface  81   b  (FIG. 21B) of the base. 
     As in the case of the insert  80   a , one of the prongs  86   b  of the insert  80   b  preferably includes a pin  89   b  adapted in shape and size to project into and preferably through the empty hole in the mother plate when the mother plate is received snugly between the surfaces  85   b  and on top of the surface  96   b , to fill and seal the hole from electrolyte as well as provide a means for anchoring the insert  80   b  to the mother plate and, thereby, for anchoring the edge strip to the mother plate. 
     Also as in the case of the insert  80   a , it is most advantageous to install the insert  80   b  onto the mother plate first, e.g., by spreading the prongs apart sufficiently so that the pin  89   b  clears the surface of the mother plate until the pin is positioned for insertion into the hole in the mother plate, and then to install the edge strip, e.g., by sliding the edge strip down along the side edge of the mother plate so as to engage the prongs in the respective portions  22   a ,  22   b  (FIG. 2) of the longitudinal slot, and finally abutting the end  79  of the edge strip snugly against the top surface  81   b  of the base  82   b.    
     Corresponding to the configuration (c) above, an insert  80   c  (not shown) may be provided that is similar to the insert  80   a , except that the slot may be omitted so that the edge  20  of the mother plate is flush with the top surface of the base. 
     Corresponding to the configuration (d) above and referring to FIGS. 23A-23C, an insert  80   d  may be provided that is similar to the insert  80   b , except that a slot  100  extending through a base  82   d  is provided so that the edge  20  of the mother board may be positioned to be flush with a bottom surface  83   d  of the base  82   d  instead of resting on the top surface  81   d  as in the insert  80   b.    
     Though it is less desirable, configuration (d) may also be implemented by providing a slot extending from the top surface into but not through the base, or by replacing the slot with a surface that is elevated with respect to the top surface of the base on which the edge  20  of the mother plate may rest, all without departing from the principles of the invention. 
     Any of the inserts  80  may be provided in right or left hand form as required. As in the case of the embodiment 30 of FIG. 5, a glue or sealant may be applied to all abutting or mating surfaces and to fill any remaining gaps or interstices to further seal and strengthen the assembly. Preferably, the anchors of the inserts  80  are adapted to be press-fit around the edge of the mother plate  10 . 
     It is clear that the insert of the invention has been described in terms of a conventional edge strip characterized by a longitudinal channel and a slot having the geometry illustrated in the figures. As one skilled in the art would readily understand, though, the invention can be used in equivalent fashion with any other type of edge strip, the fundamental idea being only to replace the missing corner piece of the mother plate with a nonconductive filler plug and, preferably, also with a binding material. 
     As will be readily apparent to a person of ordinary mechanical skill, an insert designed for a different type of edge strip would have to be modified to conform to the specific interior geometry of the strip. 
     Various changes in the details, steps and components that have been described may be made by those skilled in the art within the principles and scope of the invention herein illustrated and defined in the appended claims. Therefore, while the present invention has been shown and described herein in what is believed to be the most practical and preferred embodiments, it is recognized that departures can be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent processes and products.