Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2000-03-31
2001-07-24
Bell, Bruce F. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S281000, C029S746000
Reexamination Certificate
active
06264808
ABSTRACT:
The present invention relates to an electrode used in electrolytic refining or electrowinning, i.e. a cathode, provided at least on one side with an edge strip made of some insulating material in order to prevent the growing together of the deposits created in electrolytic refining or electrowinning. The invention also relates to a method for producing the electrode.
BACKGROUND OF THE INVENTION
In electrolytic refining or electrowinning, which is used as a sub-process in the production of metals, such as copper, nickel and zinc, the cathode electrode employed at present is commonly a mother plate made of stainless steel, and the metal to be refined is precipitated on both sides of said mother plate. If the mother plate edges are not protected with an edge strip made of some insulating material, the deposits created in the refining or electrowinning process on both sides of the mother plate will grow together. Such edge strips and their use is described for example in the EP patent application 454,056 and in the FI patent application 955,919.
The edge strips used in the mother plate are generally installed on the mother plate surface, in which case the surface-installed edge strips are susceptible to damage when the deposits are being removed. Particularly the bottom edge strip, located on the opposite side with respect to the fastening edge of the hanger bar of the mother plate, is prone to damage, because the deposits are usually removed from the hanger bar direction towards the bottom edge strip. Although the bottom edge strip were not damaged during deposit removal, the edge strip installed on the mother plate surface gathers impurities that weaken the purity of the deposit created on the mother plate surface.
In order to obviate the drawbacks caused by edge strips installed on the mother plate surface, the FI patent application 863,244 introduces an edge strip which is installed in a dovetail groove, so that part of the edge strip is placed in said groove in order to support the external part of said groove.
The edge strip is formed of a polymer film, folded in its longitudinal direction; a stainless steel wire is placed in the fold, and the overlapping film halves, located on top of each other, are joined in a watertight fashion. The edge strip formed in said fashion is drawn in, together with the included wire, starting from the bottom end of the grooved cathode edge. Thus the edge strip is drawn over the topmost horizontal cathode edge, so that the overlapping part facilitates the replacing of a used edge strip at some later stage. By means of the stainless steel wire placed in the groove, the edge strip is protected from being protruded or drawn out of the wedge-shaped aperture during usage. However, the edge strip according to the FI patent application 863,244 is not suited to be realized as a uniform strip covering all three edges of the cathode plate, because the problems caused by the bottom corners of the cathode plate, left in between the vertical edge strips and the horizontal edge strip, are equally serious as with traditional external edge strips. Moreover, the structure of the edge strip is not necessarily suitable for ordinary cathode plate thicknesses, because for instance the use of stainless steel wire requires a given addition in the cathode plate thickness.
SUMMARY OF THE INVENTION
The object of the present invention is to obviate some of the drawbacks of the prior art and to realize an improved electrode for electrolytic refining or electrowinning, with lower production costs than the prior art electrodes, and a method for producing said electrode; the electrode edges, apart from the hanger bar fastening edge, are provided with edge strips in order to prevent the deposits created in electrolytic refining or electrowinning from growing over the edges, from one side of the electrode to the other, so that at least one of the edge strips is installed at least partly to an essentially straight-walled groove formed in the electrode edge. The essential novel features of the invention are apparent from the appended claims. According to the invention, in an electrode used in electrolytic refining or electrowinning—one edge of which electrode is provided or can be provided with a hanger bar—there is formed a groove at least in the edge opposite to the hanger bar, and the width of said groove is substantially equal at least at its front end located at the electrode edge and at the rear end placed inside the electrode. The desired groove width between said groove ends can vary depending on the target of usage of the electrode; in the area between the two ends, the groove can either have equal walls, or then it can be wider or narrower. If the groove has equal walls in the area between the two ends, the groove wall is essentially straight through the whole length of the groove and parallel to the electrode surface. If the groove is wider in the area between the two ends, this widening is achieved either in a curved or in a linear fashion. The widening of the groove is advantageously achieved so that the groove is at its widest substantially in the middle, with respect to the groove length. When the groove is narrower in the area between the two ends, the narrowing is advantageously achieved in similar fashion as the widening of the groove.
By means of the design of the groove formed in the electrode edge, it is advantageously secured that the edge strip stays in place inside the groove. The staying in place can be further improved, particularly when using a straight-walled groove, by pressing the groove edges together in the immediate vicinity of the electrode edge after the edge strip already is placed in the groove. Now the width of the groove formed in the electrode edge may in the front end become smaller than in the rear end, but even in this case the starting point is a groove with front and rear ends that are substantially equal in width.
According to the invention, the edge strip made of some insulating material is at least partly installed in the groove provided in the electrode edge so that the thickness of the edge strip is essentially not more than the thickness of the electrode. The edge strip thus prevents the growth of the deposit from one side of the electrode to another side so that the deposits created on the different sides cannot grow together over the electrode edge surface. At the same time, the edge strip does not, however, prevent possible impurities contained in the electrolyte from unrestrictedly flowing along the electrode surface.
The edge strip manufactured of some insulating material and installed, at least partly, in the groove made in the electrode edge is advantageously made by extruding the plastic material of the edge strip directly into the groove, in which case the desired shape for the edge strip is obtained simultaneously. The edge strip can also be shaped so that when manufacturing the edge, for example by machining or by extrusion, the edge strip is designed, at least as regards the part meant to be inserted in the groove provided in the electrode edge, to be essentially wedge-shaped.
When employing, according to the invention, an edge strip that is at least partly installed in a groove formed in the electrode edge, at least in the edge that is opposite to the electrode hanger bar, there can be achieved a substantially uninterrupted protection for all electrode edges, apart from the hanger bar fastening edge. In all three edges, there can now be used for instance ready-shaped wedge-like edge strips that are sawed in the desired measures. The edge strips are installed in the grooves formed in the electrode edges, and the groove edges are, when necessary, pressed together in order to ensure that the edge strip stays better in place in the groove. It is also possible to use, exclusively in the groove opposite to the electrode hanger bar, a ready-shaped, wedge-like edge strip to be installed in the groove made in the electrode edge, whereas the edges adjacent to the hanger bar are provided with edge strips external to the edge.
Bell Bruce F.
Outokumpu Oyj
Smith-Hill and Bedell
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