AU2009265804B2

AU2009265804B2 - Stripping apparatus and method for removing an electrodeposited metal layer from a cathode plate

Info

Publication number: AU2009265804B2
Application number: AU2009265804A
Authority: AU
Inventors: Leon Crosset
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-07-04
Filing date: 2009-06-30
Publication date: 2014-06-26
Anticipated expiration: 2029-06-30
Also published as: WO2010000717A3; BRPI0915708A2; CN102084036A; EP2141265A1; WO2010000717A2; EP2318571B1; CN102084036B; EP2318571A2; BRPI0915708B1; ES2390007T3; AU2009265804A1

Abstract

Apparatus and method for removing an electrodeposited metal layer from a cathode plate comprising a feeding zone, a metal stripping unit, a discharge zone, and a carousel with a substantially horizontal axis of rotation comprising engaging means such that: (i) In a first position, first engaging means face the end of the conveyor feeding line so as to pivotally engage the first coated cathode plate present on said line; (ii) In a second position, the engaged first cathode is brought into position in the stripping unit by rotation of the carousel, whilst a second coated cathode is engaged into the next engaging means of the carousel; and (iii) In a third position the stripped first cathode plate is discharged onto the discharge zone by further rotation of the carousel whilst the second cathode is brought into position in the stripping unit and a third coated cathode is engaged in the nextengaging means facing the conveyor feeding line.

Description

WO 2010/000717 PCT/EP2009/058149 Stripping apparatus and method for removing an electrodeposited metal layer from a cathode plate 5 Field of invention The present invention relates to the field of metal production by cathodic electrodeposition and in particular to the removal of the electrodeposited metal coating from the cathodic support plate. 10 Background of the invention Metal refinement by electrolysis is a well known technique applied for the production of metals like zinc, copper, silver, etc. and consists of inserting a 15 cathode into an electrolytic cell containing a solution including an ion of the metal to be refined. Upon application of an electric field across the cell, metal is electrolytically deposited onto the surfaces of the cathode in contact with the solution to form a metal coating. The top of the cathode is generally located above the level of the solution so as to leave an area of the cathode which 20 remains uncoated. When the metal coating has grown to the desired thickness, it must be scraped or stripped off the cathode. In some techniques, the metal coating is scraped off the surface of the cathode while the latter is still immersed in the electrolytic solution. For example, In 25 US 3,772,003 the cathode is in the shape of a rotating drum partially immersed in the electrolytic solution. The deposited metal is removed continuously as the cathode drum rotates by a scraping blade tangently contacting the surface thereof which stands out of the solution level. In US 4,273,640 disc-shaped cathodes are rotatably mounted in an electrolytic cell such as to be partially 30 immersed in the elecrolytic solution. As the cathode rotates, a metal coating is WO 2010/000717 2 PCT/EP2009/058149 formed on the surface thereof and is scraped by a blade immersed in the solution. In US 5,565,083 the cathode is in the form of a plate and the deposited metal is removed from the major surfaces of the cathode plate with a scraper blade moving relative to the cathode while this is still immersed in the 5 electrolytic cell. In a different approach, EP 436,602 discloses a cathode in the shape of e.g., a drum which is lifted out of an electrolytic cell when the coating is of a sufficient thickness. Then scraping knives located below the drum and mounted on hinges so as to form a funnel or truncated cone are displayed such that when the cathode is driven down, the metal coating deposited on its inner 10 surface is scraped off by the funnel forming blades and recovered in the centre thereof as the drum is immersed again for further coating. These techniques all have the advantage of being continuous or semi-continuous, but they do not permit the recovery of the metal in the form of a sheet, but rather in a particulate form. 15 In order to obtain the refined metal in the shape of sheets, it is necessary to allow enough time for a metal coating of a sufficient thickness to build up on the immersed surfaces of the cathode before removing the coating. This led to the development of sequential batch processes, wherein a plurality of cathodes, 20 usually rectangular plates, are first immersed in a corresponding number of electrolytic cells in an electrodeposition unit for a time sufficient to build up a metal coating of the desired thickness. In a second step the coated cathodes are removed from the electrolytic cells and brought to a stripping unit where the metal coating is separated from the main surfaces of the cathode plates by 25 blades or knives in relative movement with the interface between the cathode plate and the metal coating. The refined metal is recovered in the shape of sheets and is conveyed away for further processing, while the scraped electrode plates are removed, their surfaces cleaned and are returned to the electrodeposition unit. 30 WO 2010/000717 3 PCT/EP2009/058149 In US 1,553,080 of 1921, a coated plate is lifted out of an electrolytic cell and as it is being lifted is engaged in a stripping device comprising fixed blades. The relative movement of the raising cathode and the fixed knives causes the removal of the metal deposit from the surface of the cathode. In most 5 techniques, however, the relative movement of the stripping blades and the interface between the cathode and the metal coating consists of mobile blades running over the surface of a fixed cathode (cf. e.g., US 4,806,213). US 3,996,127 discloses an apparatus wherein a plurality of coated cathode plates 10 are conveyed to a stripping unit in a conveying line wherein the plates are hung side by side, forming a garland. Although this equipment allows the coated cathode plates to be delivered to the stripping unit in an automated step-by step process, the side-by-side arrangement of the cathodes is not compatible with today's productivity requirements and space restrictions. For these reasons, 15 most stripping apparatuses comprise a conveyor wherein the coated cathodes are arranged in a face-to-face relationship instead. in JP 3138388, JP 55018584, and JP 62224694, apparatuses are disclosed wherein the metal coating of a plurality of coated cathode plates arranged in a 20 face-to-face relationship are simultaneously stripped by a corresponding number of stripping blades. This batch process is interesting but is complex and expensive as it requires the movement of a plurality of stripping blades to be coordinated. Yet another apparatus is disclosed in WO 02/097170 wherein the stripping is carried out in two steps: a first lateral stripping followed by a 25 second, vertical scraping step. The former lateral stripping is carried out while the cathode is still hanging on the conveying line. Although the plates are arranged in a face-to-face relationship in all these apparatuses, they must be separated from one another by a distance sufficient to allow the insertion of the stripping blades in between. In order to increase the number of plates being 30 conveyed to the stripping unit, and hence reduce the size of the line, many WO 2010/000717 PCT/EP2009/058149 apparatuses comprise a supply line where the coated cathode plates are arranged in a close packed face-to-face arrangement and further comprise a transfer device to transfer individual plates from the supply line to the stripping unit. 5 In order to transfer coated cathode plates one by one to the stripping unit various systems were proposed. Individual feeding systems comprising a bars and pistons mechanism allowing individual plates to be transferred from the conveyor to the stripping unit are described in US 3,625,806, US 3,847,779 and 10 EP 470,033. These systems, however, are rather complex and may suffer from fatigue problems due to the repetitive reciprocating motions they are subjected to. Furthermore, they are rather slow, since several components must move back and forth in perfect coordination to feed a first cathode plate to the stripping unit and to catch the next one from the conveyor. 15 Alternative to the bars and pistons feeding mechanisms, US 3,689,396 describes a first step-by-step conveyor in connection with a second, continuous conveyor to convey individual plates from the first conveyor to the stripping unit. As an alternative thereto, a carousel loading individual cathode plates from the 20 conveyor to various processing stations were proposed in EP 482,258. The rotating axis of the carousel in this document is substantially vertical, and the stripping operation requires several stages which are too long according to today's standards. 25 There thus remains a need in the art for stripping apparatuses which are quick, durable, reliable, and compact. 30 5 Summary of the invention The present invention is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims. In particular, in an aspect of the 5 present invention there is provided a novel apparatus for removing an electrodeposited metal layer from a cathode plate comprising: (a) a feeding zone comprising a conveyor feeding line to convey coated cathode plates arranged in a face to face relationship to, 10 (b) a metal stripping unit wherein the electrodeposited metal is stripped off the opposite two main surfaces of the cathode plates with two knives; and (c) a discharge zone wherein the stripped cathode plates are conveyed away in a face to face arrangement for further handling, 15 characterized in that, it further comprises (d) a carousel with a substantially horizontal axis of rotation comprising engaging means such that: (i) In a first position, first said engaging means faces the end of the conveyor feeding line so as to pivotally engage the first coated 20 cathode plate present on said line; (ii) In a second position, the engaged first cathode is brought into position in the stripping unit by rotation of the carousel, whilst a second said coated cathode plate is engaged into the next said engaging means of the carousel; and 25 (iii) In a third position the stripped first said cathode plate is discharged onto the discharge zone by further rotation of the carousel whilst the second said cathode plate is brought into position in the stripping unit and a third said coated cathode plate is engaged in a further said engaging means facing the conveyor feeding line 6 In another aspect of the present invention there is provided a process for removing an electrodeposited metal layer from a cathode plate comprising the following steps: 5 (e) feeding coated cathode plates arranged in a face to face relationship from an electrolytic deposition unit to a carousel having an axis of rotation substantially horizontal; (f) loading a first said coated cathode plate onto the carousel in a loading zone and bringing it to a metal stripping unit by rotation of the 10 carousel, whilst a said second coated cathode is loaded onto the carousel; (g) stripping the electrodeposited metal layer off the opposite two main surfaces of the first cathode plate present in the stripping unit by driving two knives down the interface between the cathode plate and 15 the metal coating; (h) recovering stripped metal sheet in a receiving unit for conveying it away for further handling; and (i) bringing the stripped first cathode plate to a discharge zone by further rotation of the carousel, which simultaneously drives the second coated 20 cathode plate to the stripping unit and loads a third said coated cathode plate onto the carousel. The major difference between the present invention and the known apparatuses is that the coated cathodes are fed individually to the stripping unit by a carousel having a 25 substantially horizontal axis of rotation. This has several advantages. First the carousel always rotates in the same direction which ensures smoother and quicker operations as well as more durability than systems comprising reciprocating parts, which are subject to fatigue failures. Second, the present invention is compact since the coated cathode plates are conveyed in a close packed arrangement prior to being fed to the stripping unit, and 7 the carousel width is substantially flush with the rest of the apparatus and occupies little area on the floor compared with a carousel rotating around a vertical axis as in EP 482,258. Third, with the appropriate stripping device as defined below, the stripping process can be shortened by reducing the number of movements required to complete 5 this task. In particular, a stripping device particularly suitable for removing an electrodeposited metal layer from a cathode plate comprises: (a) a scissor-like frame comprising two reciprocating members pivotally connected to a central member; 10 (b) a pair of stripping knives mounted at one end of each reciprocating member at a distance from the connection point thereof to the central member at least equal to the height of the cathode plate to be stripped; (c) first driving means to open and close the scissor-like frame, and thus 15 to drive apart and closer together the knives, respectively; and (d) second driving means for driving the whole scissor-like frame down and up again, over a distance at least equal to the height of the cathode plate to be stripped. 20 An apparatus according to the present invention further comprising a stripping device as described above is preferred and is particularly advantageous because it allows the stripping cycle to be completed with a total of five moves: (1) first rotation of the carousel to bring the coated cathode into position; (2) closing of the scissor-like frame to bring the stripping knives into contact with the top of the cathode; (3) driving the knives down 25 along the interface between the metal coating and the cathode plate to remove the metal sheet; (4) driving the knives up again and open the scissor like frame; and (5) with a second rotation of the carousel bring the uncoated cathode plate to a discharge zone. As this happens, the next coated cathode plate is already in position at the stripping unit, 8 ready to undergo steps (2)-(5) again. The total stripping cycle (1)-(5) for one cathode can be as short as less than 7 s, preferably less than 5 s, and most preferably, less than 4 s. Throughout this specification, the word "comprise", or variations thereof such as 5 "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Any discussion of documents, acts, materials, devices, articles or the like which has been 10 included in this specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia or elsewhere before the priority date of this application. 15 Brief description of the Figures Figure 1: side view of a preferred stripping apparatus at a first stage, wherein a first cathode plate on the conveyor is engaged onto the carousel; 20 Figure 2: side view of a preferred stripping apparatus at a second stage, wherein the first cathode plate on the conveyor is being driven to the stripping unit by rotation of the carousel, and the scissor-like frame is open; 25 Figure 3: side view of a preferred stripping apparatus at a third stage, wherein the first cathode plate is at the stripping unit, the scissor-like frame is closed and the stripping knives in contact with the main surfaces of the cathode; 9 Figure 4: side view of a preferred stripping apparatus at a fourth stage, wherein the stripping knives are driven down along the interface between the cathode and the metal coating thus separating it from the cathode surfaces; 5 Figure 5: side view of a preferred stripping apparatus at a fifth stage, wherein the stripping knives are driven up again and the stripped metal sheet is collected by the guiding means; Figure 6: front view of a preferred stripping apparatus at said third stage. 10 Detailed description of exemplary embodiments of the invention The stripping apparatus of the present invention comprises four main sections: (a) a conveyor (10), (b) a stripping unit (11), (c) a receiving unit (14) for receiving the stripped 15 metal sheets, and (d) a discharge conveyor for bringing the cathode plates to further processing (e.g., the surface of plates can be cleaned for further immersion into an electrolytic cell and start the cycle again). (a) conveyor (10) 20 The function of the conveyor (10) is to bring the coated cathode plates from out of the electrolytic bath to the stripping unit. For reasons of space economy the conveyor brings the plates in a close packed arrangement. According to the present invention, the cathode plates are arranged on the conveyor in a face-to-face arrangement. They may be fixed to 25 the conveying line by any means known in the art. For example, they can be hung to a single or a pair of chain or rail conveyors. The electrodes may be fixed to a support comprising fixing means to the conveyor, or the fixing means can be integral to the cathode plates, without any external support frame. The conveyor drives the cathode plates step-by-step towards the stripping unit. The downstream side of the conveyor 30 transfers the first cathode plate (62) present onto the carousel (7) of the stripping unit. In 9a this context, the step-by-step frequency of the conveyor is in phase with the step-by step rotation of the carousel as defined below. (b) stripping unit 5 The stripping unit comprises a carousel (7) for bringing each cathode plate one by one to its stripping position and a pair of knives run through the whole interface between the cathode plate and the metal coating. The carousel (7) rotates over a substantially horizontal axis which is located not higher than the WO 2010/000717 10 PCT/EP2009/058149 conveyor line. Preferably, the conveyor line is at a level comprised between the horizontal axis of rotation of the carousel and its top ridge as illustrated in the Figures. The conveyor line connects with engaging means, such as a pair of slots (1) of the carousel (7) to transfer and pivotally hang a coated cathode plate (62) 5 thereto as illustrated in Figure 1. In this position of the carousel, the next slot (2) downstream of slot (1) is in stripping position: Figure 1 shows a cathode plate (61) after stripping. Upon a first rotation of the carousel (7) the coated cathode plate (62) loaded on pair of slots (1) is brought into stripping position within range of the stripping knives, whilst at the same time the cathode plate (61) 10 which was stripped before is driven onto the discharge line (12) and the next coated cathode plate (63) is being transferred from the conveyor (11) to the pair of slots (5). At this stage it is preferred to clamp the carousel into position with clamping 15 means (13) to ensure that the system remains stable during the stripping operation. In Figure 3, clamping means (13) are illustrated as connecting with slots (3) and (4) located below the axis of rotation of the carousel, but any clamping system preventing carousel (7) from rotating can be used instead. The carousel could also be clamped through the motor controlling its rotation, but 20 this solution requires the use of powerful motors which add to the cost of the apparatus. Once in stripping position, a pair of stripping knives (8) is brought into contact with the two main surfaces of the cathode, at a level located above the coating 25 line. In this respect, according to the present invention, the knives (8) are mounted at the end of long arms (20) connecting to form a scissor-like frame, said arms being long enough to allow the knives to be run from the top to the bottom of the cathode plate.

WO 2010/000717 11 PCT/EP2009/058149 In operation, the scissor-like frame (20) is open during rotation of the carousel (7) to give clearance to the coming coated (62) and to the departing stripped cathode plates (61) as illustrated in Figure 2. Once the cathode plate is in stripping position and the carousel is preferably clamped into position, the 5 scissor-like frame closes its arms thus bringing the knives (8) into contact with the uncoated top section of the cathode plate (cf. Figure 3). The scissor-like frame is then driven down to run the knives through the interface between the metal coating and the cathode plate (cf. Figure 4). In order to ease the stripping work of the knives, a wedge like tool (31) can be positioned ahead of the knives 10 to initiate a crack at the interface and allow the knives to run into this crack (cf. Figure 6). When the coated metal sheet is detached from the cathode plate it falls down and is recovered by guiding means (14) which gently guide the metal sheet to a 15 receiving unit for conveying it for further handling. At this point the scissor-like frame (20) is driven up again until the knives reach their starting position (cf. Figure 5) and is then opened to give clearance to the departing cathode plate which has just been stripped and for the coming coated cathode plate (63) upon further rotation of the carousel (after removal of the clamping means (13), if it 20 applies). Stripping devices of other types can be conveniently used with the stripping apparatus of the present invention, but the one described above, with the knives mounted at the end of a scissor-like frame is particularly preferred as it allows to 25 substantially reduce the size of the equipment and reduce the number of knives movements required to carry out the stripping operation: closing the scissor-like frame, driving it down, driving it up, and opening the scissor-like frame. Such economy of movements allows the control unit to be simpler and saves a lot of time. The time required for one stripping cycle with the apparatus of the present 30 invention is estimated between 3 and 7 s, preferably between 3 and 6 s, most WO 2010/000717 12 PCT/EP2009/058149 preferably between 3 and 5 s, leading to stripping cycle time reductions of up to 70% with respect to existing stripping lines. Figure 6 illustrates a front view of the stripping unit showing cathode plates (62) 5 and (61) hanging on the carousel (7), the former at its stripping position and the latter at its transfer position onto the discharge zone (12). The carousel's rotation is driven by motor (30). The knives (8) are shown in stripping position, contacting the uncoated top section of the cathode plate (62). It can be appreciated from Figure 5 that the alignment of the cathode plate (62) to be 10 stripped and the stripping knives (8) is critical for the stripping operation. For this reason it may be advantageous to provide the carousel with alignment means (15) for bringing the cathode in alignment with the stripping knives (8) as the cathode is driven to the stripping unit (11). A simple and efficient alignment means (15) consists of curved handles positioned in the inner side of the 15 carousel's walls, vis-A-vis each slot and such that a cathode (62) loaded on a pair of slots (5) is progressively and smoothly being aligned as it pivots around its hanging hinges upon rotation of the carousel (7) until it reaches its stripping position in stripping unit (11). Other alignment means can be used, but this is so simple and flawless that it is particularly preferred. 20 (c) Receiving unit (14) The coating sheets (6b) are made of purified metal which is usually very ductile and can weigh a couple of hundreds of kilograms. As the stripping knives (8) run 25 down along the coating-cathode interface the metal sheet (6b) detaches itself from its support (6a) and eventually falls down. The receiving unit (14) serves to ensure that the falling metal sheet (6b) does not crash and crumple under the impact. Several types of receiving units exist in the market as for instance the ones described in US2007/0272561 or in US 3,625,806, and can be conveniently 30 used in the present invention. As an alternative, a receiving unit (14) comprising WO 2010/000717 13 PCT/EP2009/058149 a series of wheels facing each other and mounted with rubber tyres to damp the impact. The series of wheels are so arranged as to bring the falling metal sheet (6b) from a substantially vertical position as it falls to a horizontal one as it is laid down onto a conveying belt or any other receiving element. Usually a 5 number of sheets are stacked on said receiving element before being conveyed away for further processing. When stripped off the cathode surfaces (6a), a metal sheet (6b) is folded in two, the folding line corresponding to the bottom edge of the cathode which was 10 immersed in an electrolytic cell. If all the folded metal sheets are stacked with the folding line on the same side, the pile will tilt on one side and will be unstable. In order to increase the stability of a stack of metal sheets, it is preferred that the arrangement of the series of wheels is suitable for laying the metal sheets onto the receiving element with their folding lines with alternating 15 orientations. This can be achieved by disposing a first series of facing wheels in alignment with the hanging cathode to catch the falling metal sheet and a second series of facing wheels alternatingly guiding the metal sheets so as to lay them onto the receiving element once with the folding line positioned upstream and next with the folding line positioned downstream with respect to the 20 direction of motion of the line for each new falling sheet. In particular, the second series of facing wheels may be mounted on a carriage, itself pivotally mounted below the first series of wheels. By oscillating said carriage with each new metal sheet, the folding line thereof is led downstream or upstream to achieve the desired effect. 25 (d) discharge zone (12) The discharge line (12) is located downstream of the carousel (7) and is adapted to receive the stripped cathode plates being evacuated from their stripping 30 position. The discharge zone comprises a conveyor similar to the one described WO 2010/000717 14 PCT/EP2009/058149 in point (a) supra. Similarly the stripped cathodes are conveyed away step-by step from the carousel for further handling. Generally the surfaces of the cathode plates are treated and then the plates are brought back to the electrolytic cells for further electrolytic metal deposition. 5

Claims

1. Apparatus for removing an electrodeposited metal layer from a cathode plate comprising: 5 (a) a feeding zone comprising a conveyor feeding line to convey coated cathode plates arranged in a face to face relationship to, (b) a metal stripping unit wherein the electrodeposited metal is stripped off the opposite two main surfaces of the cathode plates 10 with two knives; and (c) a discharge zone wherein the stripped cathode plates are conveyed away in a face to face arrangement for further handling, characterized in that, it further comprises 15 (d) a carousel with a substantially horizontal axis of rotation comprising engaging means such that: (i) In a first position, first said engaging means faces the end of the conveyor feeding line so as to pivotally engage the first 20 coated cathode plate present on said line; (ii) In a second position, the engaged first cathode is brought into position in the stripping unit by rotation of the carousel, whilst a second said coated cathode plate is engaged into the next said engaging means of the carousel; and 25 (iii) In a third position the stripped first said cathode plate is discharged onto the discharge zone by further rotation of the carousel whilst the second said cathode plate is brought into position in the stripping unit and a third said coated cathode plate is engaged in a further said engaging means facing the 30 conveyor feeding line. 16

2. Apparatus according to claim 1, wherein the stripping unit comprises: (e) a scissor-like frame on which are mounted the knives and 5 comprising: (i) closing means for closing the scissor-like frame to bring the knives into contact with the opposite main surfaces of the cathode plate in position in the stripping unit; and (ii) driving means for driving the scissor-like frame downwards 10 to strip the deposited metal layer off the cathode plate with the knives.

3. Apparatus according to any one of the preceding claims, further comprising guiding means located below the stripping unit for guiding 15 stripped metal sheets to a receiving unit for conveying them away for further handling.

4. Apparatus according to the preceding claim, wherein the guiding means comprise at least one pair of rotatably mounted wheels and so separated 20 as to accommodate therebetween stripped said metal sheets falling from the stripping unit.

5. Apparatus according to any one of the preceding claims, wherein the carousel comprises clamping means to firmly hold the cathode plate in 25 position in the stripping unit.

6. Apparatus according to any one of the preceding claims, wherein each said engaging means of the carousel is provided with alignment means for bringing the cathode plate in alignment with the stripping knives as 30 the cathode plate is driven to the stripping unit. 17

7. Apparatus according to the preceding claim wherein the alignment means consist of curved handles positioned in the inner side of the carousel's walls, vis-A-vis each said engaging means and such that a 5 said cathode plate loaded on one engaging means is progressively being aligned as it pivots around an axis parallel to the axis of rotation of the rotating said carousel until it reaches its stripping position in the stripping unit. 10

8. Process for removing an electrodeposited metal layer from a cathode plate comprising the following steps: (a) feeding coated cathode plates arranged in a face to face relationship from an electrolytic deposition unit to a carousel 15 having an axis of rotation substantially horizontal.; (b) loading a first said coated cathode plate onto the carousel in a loading zone and bringing it to a metal stripping unit by rotation of the carousel, whilst a second said coated cathode is loaded onto the carousel; 20 (c) stripping the electrodeposited metal layer off the opposite two main surfaces of the first cathode plate present in the stripping unit by driving two knives down the interface between the cathode plate and the metal coating; (d) recovering stripped metal sheet in a receiving unit for conveying 25 it away for further handling; and (e) bringing the stripped first cathode plate to a discharge zone by further rotation of the carousel, which simultaneously drives the second coated cathode plate to the stripping unit and loads a third said coated cathode plate onto the carousel. 18

9. Process according to claim 8 wherein the stripping step comprises: - bringing the knives into contact with the top of the opposite 5 main surfaces of the cathode plate by closing a scissor-like frame located on top of the plate and on which the knives are mounted; and - driving each said knife downward along the respective interface between the cathode plate and the electrodeposited metal layer. 10

10. Process according to claim 8 or 9, wherein the recovering step comprises guiding stripped metal sheet falling from the stripping unit with guiding means to a receiving unit for conveying it away for further handling. 15

11. Process according to any one of claims 8 to 10, wherein the cathode plates simultaneously and progressively pivot around an axis parallel to the axis of rotation of the carousel and are aligned with respect to the position of the knives as the carousel rotates between the loading zone and the stripping unit. 20

12. Process according to any of claims 8 to 11, wherein the carousel is clamped into position prior to the stripping step when a said coated cathode plate is in position in the stripping unit. 25

13. Process according to claim 9, wherein the stripping step comprises the following steps: - the scissor-like frame holding the knives is in an open position while the carousel rotates to bring a said coated cathode plate to 30 the stripping unit such that the knives leave enough clearance 19 for the cathode plate to pass from a conveyor feeding line to the stripping position; - once the cathode plate is in position in the stripping unit, the carousel is clamped into position and the scissor-like frame is 5 closed to bring the knives into contact with the cathode plate; and - the electrodeposited layer is stripped off the plate by driving the scissor-like frame down so that each said knife runs down along a respective interface between the coating and the 10 electrodeposited metal layer, and the stripped metal sheet falls into the guiding means and is led to a receiving unit.

14. An apparatus for removing an electrodeposited metal layer from a cathode substantially as hereinbefore described with reference to one or 15 more of Figures 1 to 6 of the accompanying drawings.

15. A process for removing an electrodeposited metal layer from a cathode substantially as hereinbefore described with reference to one or more of Figures 1 to 6 of the accompanying drawings. 20