OA11970A

OA11970A - Cathode plate.

Info

Publication number: OA11970A
Application number: OA1200100335A
Authority: OA
Inventors: Revill Wayne Armstrong; David Bailey
Original assignee: Copper Refineries Pty Ltd
Priority date: 1999-06-18
Filing date: 2000-06-16
Publication date: 2006-04-17
Also published as: CN1263897C; PL352310A1; RO121039B1; EP1230440A1; JP2003502512A; CN1357059A; MXPA01013036A; ES2627807T3; EP1230440B1; TR200103610T2; BR0011752A; AR024402A1; CA2377364A1; AUPQ106699A0; EP1230440A4; ZA200110359B; PL201085B1; CA2377364C; RU2247799C2; PE20010502A1

Abstract

A method of electro-depositing an envelope of metal on a cathode. The metal envelope (120) comprises metal sheets (122, 124) on either side of the cathode plate (100). A groove (150) is provided along one edge of the cathode plate whereby metal deposited on and adjacent to said groove forms a frangible portion (140). The groove is shaped such that a line of weakness (A) is formed in the metal deposited within the groove such that separation of the two sheets of deposited metal is initiated along the line of weakness.

Description

i 119 7 ο

I . .1 .

TITLE: CATHODE PLATE

TECHNICAL FIELD

The présent invention relates to a cathode plate for use in electro-deposition of métal.

5 BACKGROUND ART

There are various processes and apparatus for electro-refining or electro-winning métal.

One particularly successful process for electro-depositing of copper for example isthe so-called ISA PROCESS in which copper is deposited on a stainless Steel cathode 10 mother plate. The electrolytically deposited copper is then stripped from the cathode byfirst flexing the cathode to cause at least a part of the copper deposit to separate from thecathode and then wedge stripping or gas blasting the remainder of the copper from the cathode.

In the ISA PROCESS the bottom edge of the cathode mother plate is generally 15 covered with a release compound such as wax or a plastic edge strip to prevent déposition of copper thereon. This allows for removal of the electro-deposited copper assubstantially équivalent separate sheets from both sides of the cathode plate. Suchwaxing of the cathode sheet, however, is time consuming and there is added cost bothfor applying the wax and for recovering the wax from the stripping process and 20 associated housekeeping.

To avoid these difficulties, some electro-refining/electro-winning operations use aso-called enveloped cathode process. In such a process the lower edge of the cathode 11970 -2- sheet is not waxed and the electro-deposited métal is allowed to grow on both sides ofthe sheet and around the bottom edge of the cathode mother plate.

Removal of the electrolytically deposited envelope of métal is then accomplishedby flexing the cathode and pulling back the métal from both sides of the sheet so that it 5 forms a V. The cathode mother plate is then removed from between the electrolyticallydeposited envelope of métal, the envelope is then closed and rotated from its verticalposition to a horizontal position and transported to a stacking/bundling station.

Not only does such a removal process require complex apparatus for opening themétal envelope, removing the cathode mother plate prior to closing of the envelope and 10 rotating the envelope from the vertical to the horizontal position for stacking, such anarrangement is time consuming and generally not as quick as the ISA PROCESSstripping step.

In conjunction with other parties, the applicant has recently developed a newprocess in which an envelope of métal is formed on the stainless Steel cathode mother 15 plate and then stripped into two separate sheets. This process is subject of co-pendingInternational Patent Application No. PCT/FI99/00979. By way of summary, the new process will be discussed with reference to figures 1A-1D and 2A-2D attached herewith.The initial step in stripping an electrolytically deposited métal envelope from its cathode mother sheet is to at least partially separate either side of the deposited envelope 20 from the cathode sheet. In this regard reference is made to figures 1A-1D. The enveloped cathode comprises cathode sheets 20 and 30 deposited on the cathode mothersheet 10 and joined along the lower edge thereof by a frangible portion 40. The cathode -3- 119 7ο mother sheet is firstly flexed to provide séparation of at ieast the upper end portion 50 ofthe sheets 20, 30.

The partially separated envelope as shown if figure 1D is then subjected to astripping operation as shown in figures 2A and 2B. The partially separated sheets 20 5 and 30 are positioned in a stripping apparatus on rollers or conveyor belt 50. Theapparatus includes a wedge stripper or air blaster 130. These wedge strippers 130 enterthe gap between sheets 20, 30 and cathode mother sheet 10. The wedge strippers 130release the sheets 20 and 30 of the electro-deposited envelope from the cathode mothersheet 10. The sheets 20 and 30, however, are still held together by the ffangible portion 10 40 extending along the bottom edge of the cathode sheet 10 as shown in Figure 2B. To effect full séparation of the electro-deposited métal envelope into separate substantiallyéquivalent sheets. These sheets are 20 and 30 is held by grippers 25,35 and rotated aboutthe frangible portion 40 from the substantial vertical position shown in figure 2B to thesubstantially horizontal position shown in figure 2C. This rotation séparâtes the 15 deposited métal into two substantially équivalent sheets. In many cases, a single rotationof the sheets 20, 30 from the vertical to the horizontal is ail that is required to separatethe sheets. This séparation of the sheets 20 and 30 from each other as well as thecathode mother plate may be confirmed by the grippers 25, 35 as foliows. The gripperswhich still hold the sheet 20, 30 in the horizontal position shown in figure 2C, are 20 adapted to pull the respective sheets slightly outward as shown in figure 2D. If thesheets, 20, 30 move outwardly in unison with the grippers, séparation of the sheets 20, 30 is confirmed. If, however, the force to move the grippers outward is too great orsimply the grippers do not move this indicates that the frangible portion 40 has not in 1197 0 -4- fact separated the sheets 20,30 and accordingly further rotation (as shown in figure 2C)of the sheets may be required.

If further manipulation/rotation of sheets 20, 30 is required, the apparatus usinggrippers 25 and 35 rotâtes sheets 20 and 30 upwardly and downwardly until the 5 aforementioned confirmation of séparation of the sheets is effected.

Once the cathode sheets 20 and 30 are separated into substantially équivalent separate sheets, it is a simple matter to transport the sheets out of the apparatus forstacking and subséquent treatment.

In some cases it is quite difficult to separate the envelope of deposited métal into 10 two separate sheets. As will be appreciated, repeated rotation or flapping of the sheetportions can be quite finie consuming and reduces the overall effîciency of the process.

Reference is made to Figure 3 which shows a groove 15 in a cathode mother plate 10 with deposited métal extending around the end of the cathode mother plate 10. This» groove 15 is formed in the bottom edge of the cathode mother plate as a ’growth 15 effecting means' as described in co-pending International Patent Application No. PCT/FI99/00979. The Applicant's hâve found, however, that even with groove 15 thedeposited métal may not cleanly release from the cathode plate or split into twosubstantially équivalent sheets 20, 30. To explain, as shown in Figure 3, on occasion,the métal envelope séparâtes into two sheets with a lip 25 attached to one sheet. This lip 20 extends around almost the entire end portion of the mother plate 10. The fracture line 35between métal sheets 20 and 30 is essentially on one side of the cathode mother plate 10rather than being in the preferred frangible région 40 at the lower end of the motherplate. 11970 -5-

It is an object of the présent invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a usefiil alternative to the prior art.

DISCLOSURE OF THE INVENTION

In a first aspect, the présent invention provides a method of electro-depositing anenvelope of métal on a cathode said envelope including deposited métal on either side ofsaid cathode and joined along at least one edge by a frangible portion, and beingremovable from said cathode by rotation of respective sides of the deposited métalenvelope about the frangible portion to separate the deposited métal from the cathodeinto two substantially équivalent sheets, the method comprising providing a groove on said cathode plate whereby métaldeposited on and adjacent to said groove forms said frangible portion, and wherein said groove is shaped such that a line of weakness is foimed in themétal deposited within the groove such that séparation of the two sheets of the depositedmétal is initiated along said line of weakness.

In a first embodiment, the groove is shaped as a V, with the line of weakness being formed within the arc of the V.

In another embodiment the arc of the V-groove is between 75 and 105 degrees and most preferably the arc of the V-groove is substantially 90 degrees.

The présent applicant has determined that the size and shape of the groove in thecathode mother plate has an impact on the ability to separate the deposited métalenvelope from the cathode into two substantially équivalent sheets.

By appropriate sizing and shaping of the groove, it is possible to reliably provide a line of weakness between the two sides of the electro-deposited envelope, such that the 119 70 -6- separation or splitting of two separate sides of sheets of the deposited métal envelope isinitiated on the line of weakness within the groove.

If the line of weakness is not formed within the groove, the fracture line may beinitiated outside the confines of the groove and in some cases may continue to propagateround the end of the plate to an exterior side of the cathode mother plate métal envelopeas shown in Figure 3. The sheets may then fracture at a point outside the frangiblerégion. Having such a line of fracture outside the frangible région créâtes difficulties inthe stripping process. Firstly, it can render splitting of the two sheets quite difficult. Insome instances it may be necessary to rotate or flap the sheets several times to provideséparation. Clearly this is undesirable, and increases the résidence time of the plate inthe stripping machine and thereby slows production.

Further, having a line of fracture outside the frangible région will produce twosheets which are not substantially symmetrical or équivalent in size. One sheet may beessentially fiat with another sheet having a small lip or hooked edge as shown in Figure 3. The resulting sheets with uneven edges are unsightly and difficult to handleparticularly in high speed automated machinery.

The applicant has found that the size and shape of the groove can be tailored sothat the line of weakness extending between the two sheets remains within the confinesof the groove. The shape of the groove is a balance between allowing growth of thedeposited métal in the groove while still permitting easy séparation of the two sheets.

Indeed, in another embodiment the groove may be shaped to permit deposited métal to substantially fill the entire groove. In yet another embodiment. the groove is shaped to allow déposition of métal directly adjacent the apex of the groove. 1 19 7 0 * -7- Ιη another aspect, the présent invention provides a cathode plate for electro-deposition of métal, said cathode plate having a groove along at least one edge andshaped such that, in use. a line of weakness is formed in the métal deposited within the groove, whereby during stripping of métal from said cathode, séparation of the envelope ofmétal into two substantially équivalent sheets is initiated along said line of weakness.

Unless the context clearly requires otherwise, throughout the description and thedaims, the words ‘comprise’, ‘comprising’, and the like are to be construed in aninclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the senseof “including, but not limited to”.

BRIEF DESCRIPTION OF THE DRAWINGS

The présent invention will now be described by way of example only withreference to the accompanying drawings in which:

Figures 1A-2D are end elevational views of the process for stripping electro-deposited métal envelopes as developed by the applicant and are included forclarification purposes only.

Figure 3 is an end elevational view of a cathode mother plate with a depositedmétal envelope partially stripped into two separate sheets,

Figure 4 is an end elevational view of an embodiment of the présent invention,

Figures 5 and 6 are end elevational views showing different shaped bottom edgesof cathode plates.

MODE(S) FOR CARRYING OUT THE INVENTION 1197 Ο -8-

Figures 1A-2D and Figure 3 ail relates to prior art mechanisms and are discussed above.

The applicants hâve found that it is possible to tailor a groove in the lower end ofthe mother plate such that a line of weakness is formed in the groove to thereby permit 5 reliable fracture of the deposited métal envelope into two substantially équivalent andpreferably symmetrical sheets. Référencé is made to Figure 4 which shows cathode mother plate 100 with a ν'-groove 150 formed along its lower end edge. For the sake of simplicity, the arc ofgroove 150 shown in Figure 4 is 90 degrees, however, as will be appreciated from the 10 foregoing it is not essential that the groove by V-shaped or that the arc of the grooveequal 90 degrees.

The shape and size of V-groove 150 is designed to perforai several fonctions. Itsprimary fonction is to permit séparation of the deposited métal envelope 120 from themother plate 100 into two substantially équivalent sheets 122 and 124. 15 Howthe V-groove provides this fonction will now be explained. As will be clear to persons skilled in the art, when the mother plate 100 is placed in an electrolytic cell ( for, say, electro-refîning of copper, it is interspersed between copper anodes andsubstantially immersed in an electrolytic solution. The copper from the anodes entersthe electrolyte for redepositing on the cathode. Generaîly, to provide a “foll terni” 20 deposit the cathode remains in the electrolyte bath for between 5 and 14 days.

When the copper crystals are deposited on the métal cathode, they are deposited at substantially right angles to the déposition surface. This is shown by arrows in Figure 4.Generaîly, the copper will take the path of least résistance and endeavour to deposit on 11970 -9- the cathode as quickly as possible. Accordingly, it will be appreciated that it is easier forthe copper to deposit on the exterior side surfaces 102, 104 of the cathode plate 100rather than in the V-groove 150. It is important, however, that copper is deposited in theV-groove since when the copper envelope is removed from mother plate 100, by pulling 5 on the opposite sides of the métal envelope as discussed above, fracture or crack initiation begins in the frangible région 140 at the lower end of the mother plate 100. Itis désirable that this crack initiation begins at the apex of V-groove 150. Accordingly, itis préférable that V-groove 150 is shaped to allow déposition of copper in the V-grooveadjacent the apex with the line of weakness extending between the arc of the V-groove 10 150.

The applicants hâve found that certain groove sizes and shapes permit such'symmetrical' splitting of the deposited métal while others do not. For instance, a V-groove with an arc of 90° ±15° allows growth of copper in the V-groove whileproviding a line of weakness as shown by dotted line A between the arc of the V-groove. 15 When the deposited métal envelope is then removed, the position of line of weakness Ain the V-groove causes the splitting of the deposited métal into two substantiallyéquivalent sheets to initiate along the line of weakness or fracture line in the frangible région 140.

The groove 150 shown in Figure 4 can be compared with the V-groove shown in 20 the Figures 5 and 6.

In Figure 5, a shallow V-groove 60 is shown. The shape of this V-groove 60 doesnot provide as great a résistance to déposition of copper as does groove 150 shown inFigure 4. Accordingly, copper is deposited quite readily in V-groove 60. This is 119 7 0 -10- desirable. However. the applicants hâve found that due to the shape of groove 60, thelength and hence effectiveness of the line of weakness is reduced. Thus a stronger bondis formed between the two sides of the métal envelope making it more difïïcult to splitthe métal envelope into two substantially équivalent sheets. Indeed, experimental trials 5 hâve shown that several cycles of rotation or flapping in the stripping machine may berequired to separate such sheets and in some cases they may split in a manner similar tothat shown in Figure 3.

In Figure 6, the groove 70 is narrower and deeper. This créâtes a greater résistanceto déposition of copper ions that enter V-groove 150 of Figure 4 or V-groove 60 of 10 Figure 5. In some cases, copper will not deposit throughout V-groove 70 and particularly not near the apex of the V-groove. This causes a bridging 80 of métal acrossthe V-groove. This bridging of métal across the V-groove avoids formation of the lineof weakness in the arc of the V-groove. The bridge 80 can act to strongly bind the twosides of the métal envelope which, once again, may resuit in the deposited métal 15 requiring several cycles of rotation or flapping to separate into two sheets which, mostlikely, will not be substantially équivalent in size.

In another embodiment of the présent invention, which is particularly suitable forelectro winning processes, the V-groove can be sized and shaped to trap gaseous material which further acts to define a line of weakness in the arc of the groove. 20 It will be appreciated that variations may be made to the process and apparatus described herein without departing from the spirit or scope of the présent invention.

Claims

119 7 0 -11 - CLAIMS

1. A method of electro-depositing an envelope of métal on a cathode said envelopeincluding deposited métal on either si de of said cathode joined along at least one edge bya frangible portion, and being removable from said cathode by rotation of respective 5 sides of the deposited métal envelope about the frangible portion to separate thedeposited métal from the cathode into two substantially équivalent sheets, the method comprising providing a groove on said cathode plate whereby métaldeposited on and adjacent to said groove forms said frangible portion, and wherein said groove is shaped such that a line of weakness is formed in the 10 métal deposited within the groove such that séparation of the two sheets of depositedmétal is initiated along said line of weakness.

2. A method as claimed in claim 1 wherein the groove is shaped as a V, the line ofweakness being formed within the arc of the V.

3. A method as claimed in claim 1 or claim 2 wherein the sides of the groove are 15 between 75 and 150° apart.

4. A method as claimed in any one of the preceding daims wherein the sides of thegroove are 90° apart.

5. A method as claimed in any one of the preceding daims wherein the groove isshaped to allow déposition of métal directly adjacent the apex of the groove. 20

6. A method as claimed in any one of the preceding daims wherein the groove is shaped to permit deposited métal to substantially fïll the entire groove.

7. A method as claimed in any one of the preceding daims wherein the groove isshaped to capture gas rising from below the cathode plate during déposition of métal. - 12- 1197ο

8. A cathode plate for electro-deposition of an envelope of métal, said cathode platehaving a groove along at least one edge and shaped such that, in use, a line of weaknessis formed in the métal deposited within the groove, whereby during stripping of métal from said cathode, séparation of the envelope of5 métal into two substantially équivalent sheets is initiated along said line of weakness.

9. A cathode plate as claimed in claim 8 wherein the groove is shaped as a V, the lineof weakness being formed within the arc of the V.

10. A cathode plate as claimed in claim 8 or claim 9 wherein the sides of the grooveare between 75 and 150° apart. 10

11. A cathode plate as claimed in any one of daims 8 to 10 wherein the sides of the groove are 90° apart.

12. A cathode plate as claimed in any one of daims 8 to 11 wherein the groove isshaped to allow déposition of métal directly adjacent the apex of the groove.

13. A cathode plate as claimed in any one of daims 8 to 12 wherein the groove is15 shaped to permit deposited métal to substantially fill the entire groove.

14. A cathode plate as claimed in any one of daims 8 to 13 wherein the groove isshaped to capture gas rising from below the cathode plate during déposition of métal.

15. A method of electro-depositing an envelope of métal on a cathode substantially asherein described with reference to any one of the embodiments of the invention 20 illustrated in the accompanying drawings and/or examples.

16. A cathode plate for electro-deposition of an envelope of métal substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.