EDGE STRIP CAP

Abstract: An edge strip (10) for a cathode plate (100). The edge strip defines a longitudinally extending channel (20) for receiving the cathode plate (100). A support member or tab (50) is also provided in the edge strip and adapted to mate with a complementary recess formed in the lower end corners of the cathode plate (100). The support member or tab (50) can provide two functions. Firstly, the support member provides a shoulder portion (55) adapted to abut the complementary surface (120) of the cathode plate and thereby support the cathode plate in the edge strip. Alternatively, or in addition, the bottom edge portion (120) concealed within the edge strip (10) is spaced apart from the exposed bottom edge (140) of the plate. This minimises metal deposition on the concealed bottom edge portion (120).

Description: TITLE: EDGE STRIP CAP TECHNICAL FIELD The present invention relates to edge strips for cathodes as used in electro-refining metal. BACKGROUND ART The ISA process as developed by Mount Isa Mines and Copper Refineries Limited in Australia in which copper or other non-ferrous metals are deposited on stainless steel cathode plates is well-known. The electrolytically deposited metal is normally stripped from the cathode by first flexing the cathode to cause at least a part of the copper deposit to separate from the cathode and by mechanical stripping or gas blasting, the sheet of deposited copper is released from the cathode. Generally, deposition of metal on the edge portions of the plate is avoided since this renders the deposited metal more difficult to strip from the cathode plate. Edge strip protectors such as plastic strip mouldings, wax coating or a combination of both may be used to avoid deposition of metal on the edge portions of the cathode plate. Generally, the longitudinal edges of the cathode plate are protected. Depending upon process requirements, the bottom end edge may be covered or left exposed. A typical example is shown in Figure 1. The cathode plate comprises stainless steel sheet 14 welded along its upper surface to hanger bar 11. On each longitudinal edge portion, an edge strip 18 is provided to prevent metal deposition along the longitudinal edges of the cathode. There have been many previously proposed edge strip configurations and methods of connecting these edge strips to the cathode plates. Some edge strips are chemically bonded to the plate, while others are mechanically attached for example by a series of pins running transversely through the edge strip and cathode plates. Chemical bonding is not always reliable and can tend to break down on exposure to the electrolyte solution and heat. Mechanical bonding is both expensive and time consuming to install. Regular maintenance and reinstallation is also required after several cycles of depositing, flexing and stripping of the plates. Australian patent application no. 15464/99 discloses a two-piece edge protector strip for a cathode plate. This protector strip has a first channel member of relatively resilient material such as rubber. This channel member is wrapped around the edge portions of the cathode plate and then forced into a second channel member which in turn grips and holds both the first channel member and the corresponding edge portions of the cathode plate together. While this arrangement is useful in that it does not require additional chemical or mechanical bonding, certain difficulties have still arisen with this technology. Generally, edge strips extend to or below the bottom end edges of the respective cathode plate. Accordingly, in use, any force applied to the bottom of the cathode plate/edge strip arrangement is transmitted to the edge strips and tends to shear or at least move the edge strips relative to the cathode plate. Any such movement or damage of the edge strip can be extremely detrimental to the process. In particular, it is both costly and time consuming to replace or reposition the edge strip protectors. Another disadvantage of the prior art arises from the deposition of metal on that portion of the cathode plate held within the edge strip. It is intended to provide a close fit in the edge strip to prevent substantial ingress of electrolyte but more particularly to prevent deposition of metal in this region. If metal is deposited on that portion of the cathode plate held by the edge strip, such deposition of metal may force open and detach the edge strip from the cathode plate. A number of techniques have been used in an effort to prevent such deposition of metal on the edge portions of the cathode plate. These include resilient collars on the edge strips or filling the edge strips with suitable sealant such as silicone. Most of these techniques have now become obsolete by providing closer tolerances between the edge stripd and the cathode plate. However, a perennial problem remains, which is the growth of the deposited metal on the exposed lower end portion of the edge of the cathode plate received in the edge strip. As mentioned above, the edge strips terminate at or slightly above the bottom end edge of the cathode plate. The bottom end edge of the cathode plate held in the edge strip, however, is exposed to electrolyte and metal may freely deposit along this bottom end edge. Generally this does not cause structural failure of the edge strip. However, once the metal is stripped from the cathode these additional deposits or "dags" remain on the stripped metal, providing an unattractive product. In severe cases these deposits act to bridge the metal sheets stripped from either side of the cathode plate, making their separation more difficult. Various mechanisms have been proposed in sealing of this end edge of the cathode plate including end caps, filling the end portion with silicone sealant or indeed covering the entire bottom end edge with an edge strip protector. Each of these methods, however, have only proved to be partially successful. It is an object of the present invention to overcome or ameliorate one or more of the disadvantages of the prior art, or at least to provide a useful alternative. DISCLOSURE OF THE INVENTION Accordingly, in a first aspect, the present invention provides an edge strip for a cathode plate, said strip having a longitudinally extending channel for receiving an edge portion of the cathode plate and at least one support member in said channel, said support member providing a shoulder portion adapted to abut a complementary surface of a cathode plate and thereby support the cathode plate in the edge strip. In a second aspect, the present invention provides a cathode plate comprising a metal portion for deposition of metal and two edge strips extending along longitudinal edge portions of the metal plate, each strip having a longitudinally extending channel for receiving an edge portion of the cathode plate and a tab extending longitudinally in said channel from said lower end and adapted to mate with a complementary recess formed in a respective end corner of the cathode plate, each said recess defining a discrete bottom edge portion concealed within the edge strip and spaced apart from an exposed bottom edge of the plate thereby to minimise metal deposition on the concealed bottom edge portion. In a particularly preferred embodiment, the tab extending longitudinally in said channel performs a dual function, firstly as the support member and secondly to minimise electrolyte migration to and minimise metal deposition on the bottom edge portion concealed within the edge strip. In another embodiment, the edge strip may include a series of support members/tabs along its length. These support members/tabs may be provided as separate pieces or formed integrally with the edge strip. In yet another embodiment, the edge strip may include an end cap at its lower end with the support member/tab extending longitudinally in the channel from the end cap. Apart from the aforementioned support member/tab arrangement, the remainder of the edge strip can be of any conventional construction. The invention is suitable for use with single piece edge strips which may include additional chemical or mechanical fastening, or two piece type edge strips such as disclosed in Australian Patent Application No. 15464/99. Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a front elevational view of a conventional cathode plate with edge strip(s). Figure 2 is a perspective view of the separate components of the first embodiment of the present invention, and Figure 3 is a side elevational view of the components of Figure 1 in situ. MODE FOR CARRYING OUT THE INVENTION Referring to the drawings, the present invention comprises edge strip 10 and tab or support member 50. The edge strip shown in Figure 2 is similar to that disclosed in Australian patent application no. 15464/99. It comprises a first relatively resilient channel member 15 adapted to be held within a channel 20 formed by second relatively rigid channel member 25. An end cap 30 closes the end of channel 20 at the lower end of the edge strip. The edge strip is adapted to receive edge portion 110 of cathode plate 100. The bottom end of edge portion 110 includes a recess or notch defining a support surface 120 and vertical surface 130. Tab member 50 is also adapted to be received in longitudinally extending channel 20. In the examples shown, tab member 50 is provided as a separate piece, however, it may be integrally formed with edge strip 10, end cap 30 or rigid channel member 25. Tab member 50 provides a shoulder portion 55 adapted to support the cathode plate. As shown more clearly in Figure 3, in use the shoulder portion 55 abuts the support surface 120 of the cathode plate 100, thereby supporting the cathode plate in the edge strip. Of course as will be apparent to those skilled in the art, an identical edge strip may be provided on the opposite edge portion of the cathode plate such that it is supported on both sides. Unlike previously proposed chemical or mechanical bonded edge strips, any force applied to the edge strip eg by dropping the cathode plate/edge strip arrangement, is transmitted from the edge strip via tab 50 to the cathode plate 100. All reaction force is thereby directed through tab 50 to the mother plate and accordingly relative movement in the longitudinal direction between edge strip 10 and cathode plate 100 is eliminated or at least reduced. This is a significant advantage over and above the prior art systems which required chemical bonding or mechanical bonding by pins etc which could shear if a significant force was applied. In this embodiment, only one tab/support member 50 is shown. It would be appreciated by persons skilled in the art, however, that it may be desirable to have several tab/support members 50 to support the cathode plate 100 along the length of the edge strip. Another advantage which arises from the embodiment shown in Figures 2 and 3 is the way metal is deposited in the lower region of the cathode plate. As discussed above, generally the bottom end edge of the cathode plate 100 extends along the entire width of the plate. In this instance, however, a notch or recess formed at the bottom end edges such that the bottom edge 120 of the edge portion 110 which is concealed with the edge strip 10, of the cathode plate is spaced from the exposed bottom edge 140 of the cathode plate. This spacing of edge 120 from edge 140 is significant in that it increases the resistance to deposition of metal such that metal will generally preferentially deposit on the exposed portions of the cathode plate including vertical edge 130 rather than depositing on edge 120. Since edge 130 is in the longitudinal direction it does not create as great a problem as growth in the lateral direction. Further, any metal deposited along edge 130 is in the direction of stripping ie the longitudinal direction of the plate. Accordingly, it does not interfere with stripping of the metal sheets on either side of the cathode plate. As known to persons skilled in the art, the dags or additional growth along the bottom end edge of the plate can make separation of the sheets from either side of the cathode plate and from each other more difficult. In these respects it will be appreciated that the invention provides a practical and commercially significant improvement over the prior art. It will be appreciated that variations can be made to the method and apparatus described without departing from the spirit or scope of the present invention.

Claims: CLAIMS 1. An edge strip for a cathode plate, said strip having a longitudinally extending channel for receiving an edge portion of the cathode plate and at least one support member in said channel, said support member providing a shoulder portion adapted to abut a complementary surface of a cathode plate and thereby support the cathode plate in the edge strip. 2. An edge strip as claimed in claim 1 comprising a series of support members along its length. 3. An edge strip as claimed in claim 1 or claim 2 wherein each support member is integrally formed with a respective edge strip. 4. An edge strip as claimed in any one of the preceding claims further comprising an end cap at its lower end, at least one support member extending longitudinally in the channel from the end cap. 5. An edge strip as claimed in claim 4 wherein the support member and end cap are of unitary construction. 6. A cathode plate comprising a metal plate portion for deposition of metal with an edge strip as defined by any one of claims 1-3 on either longitudinal edge adapted to support the cathode plate from both sides. 7. A cathode plate comprising a metal portion for deposition of metal and two edge strips extending along longitudinal edge portions of the metal plate, each strip having a longitudinally extending channel receiving an edge portion of the cathode plate and a tab extending longitudinally in said channel from said lower end and adapted to mate with a complementary recess formed in a respective end corner of the cathode plate, each said recess defining a discrete bottom edge portion concealed within the edge strip and spaced apart from an exposed bottom edge of the plate thereby to minimise metal deposition on the concealed bottom edge portion. 8. A cathode plate as claimed in any one of the preceding claims wherein the tab extending longitudinally in said channel performs a dual function, firstly as the support 5 member and secondly to minimise electrolyte migration to and metal deposition on the bottom edge portion concealed within the edge strip. 9. A cathode plate as claimed in claim 7 or claim 8 wherein each tab is integrally formed with a respective edge strip. 10. A cathode plate as claimed in any one of claims 7 to 9 further comprising end caps o at the lower end edge of each edge strip, the tab extending longitudinally in the channel from the end cap. 11. A cathode plate as claimed in claim 10 wherein the tab and end cap are of unitary construction. 12. An edge strip for a cathode plate substantially as herein described with reference to 5 any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. 13. A cathode plate substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.

Inventors: ARMSTRONG REVILL WAYNE, CUTMORE JOHN, ARMSTRONG, REVILL, WAYNE, CUTMORE, JOHN
Applicants: ARMSTRONG REVILL WAYNE, COPPER REFINERIES PTY LTD, CUTMORE JOHN, ARMSTRONG, REVILL, WAYNE, COPPER REFINERIES PTY. LTD., CUTMORE, JOHN
Application year: 2000
Main classification: C25C7
IPC codes: C25C7