Method and apparatus for stripping electrolytic precipitate from supporting structures

The invention relates to a method and apparatus for stripping a thin, sheet-like layer of electrolytically accumulated metal precipitate (6) from its supporting structures (1) by means of a peeling blade (4) driven towards the upper edge of the precipitate layer (6). For the stripping operation, the supporting structure (1) is first attached to the stripping station by aid of gripping members (2, 3), the frame whereof advantageously provides a housing in common with the peeling blades (4). Moreover, the measuring and control members (7, 8) which are advantageously located in the common housing, are used in determining the surface profile of the supporting structure (1), and the obtained profile is made use of while choosing the orientation of the peeling blade (4).

The present invention relates to a method and apparatus for stripping thin, 
sheet-like layers of electrolytically accumulated metal precipitate from 
supporting structures such as a cathode sheet or a mother sheet by 
employing a peeling blade which is advantageously driven towards the upper 
edge of the precipitate. 
In the electrolytic production of metal, such as zinc, it is customary to 
use an aluminium cathode sheet, on the surface whereof the metal layer is 
precipitated. The metal layer is stripped after the layer has reached 
sufficient thickness. In the stripping procedure there is commonly used a 
stripping machine comprising a peeling unit. The peeling unit wedges an 
aperture at the upper edge of the metal layer, whereafter the layer can be 
stripped in the stripping unit proper. 
In the method introduced in the U.S. Pat. No. 3,689,396, the knife-like 
blades are driven under the metallic precipitate at the side edge by 
employing a hinged plastic guard, which prevents the metal precipitate 
from accumulating in the corner of the cathode sheet. In order to strip 
the metal layer, the guard member is opened, and the blades have access to 
under the precipitate layer through the aperture formed under the guard 
member. However, the cathode sheets are easily corroded under the guard 
members, which considerably shortens the working age of the cathode 
sheets. Hence the cathode sheets and their production bring about 
remarkable expenses. 
The object of the present invention is to obviate some of the drawbacks of 
the prior art and to achieve an improved and cheaper method and apparatus 
for stripping metal precipitates from their supporting structures. 
In order to perform an advantageous stripping according to the invention, 
the cathode sheet comprising the metal precipitate is firmly attached at 
the top edge by means of gripping members which form the frame guiding the 
peeling blades. The position of the gripping members with respect to the 
cathode sheet is advantageously chosen so that the jaws lock the cathode 
sheet on both sides of the corroded zone caused by the solution boundary 
of the electrolysis, so that the torques created in connection with the 
stripping do not turn or bend the cathode sheet. Moreover, the gripping 
members are employed for measuring, by aid of intermediate members, the 
depth of the corrosion in order to define the profile of the cathode 
sheet. On the basis of the obtained profile, the movement of the peeling 
blades is guided in conformity to the shape of the corrosion, so that the 
peeling blades move advantageously along the surface of the cathode sheet 
both in height and in depth, thus preventing any cutting of the cathode 
sheet which would lead to further damage. 
The peeling blades of the apparatus of the invention are advantageously 
knife-like blades which are stick in between the metal precipitate and the 
cathode sheet on both sides of the sheet. The peeling blades wedge an 
advantageous aperture in between the metal precipitate and the cathode 
sheet, which is made use of in stripping the metal precipitate. 
According to the invention, the metal precipitate is stripped off the 
cathode sheet with a minimum wearing of the cathode, whereby the working 
age of the cathode sheet is lengthened and the expenses caused by the 
sheets are essentially reduced. Moreover, work safety can be essentially 
improved, because now hazardous situations caused by damaged sheets arise 
more rarely than before, the probability of damaged sheets thus being 
minimized.

For an advantageous realization of the method of the invention, the cathode 
sheet 1 lifted from the electrolytic bath is washed and conveyed to the 
stripping station according to FIG. 1. In the stripping station the 
cathode sheet 1 is fastened on both sides of the upper edge by means of 
two-part gripping members 2 and 3. The gripping members 2 and 3 are 
interconnected by aid of the frame 5, which at the same time serves as the 
housing for the peeling blades employed in the stripping procedure. 
Before the stripping procedure proper, there is determined the profile of 
the cathode sheet 1, possibly deviating from a straight planar surface and 
formed of earlier removed metal precipitate layers and/or caused by the 
solution boundary of the electrolysis. The determination of the profile 1a 
is carried out by means of the measuring members 7 and control members 8, 
attached to the frame above the precipitate layer 6 formed on the cathode 
sheet 1. On the basis of the measured surface profile of the cathode 
sheet, the position of the peeling blades 4 with respect to the frame 5 
for starting the stripping is chosen so that any wearing of the cathode 
sheet 1 owing to the stripping of the precipitate layer 6 can be 
essentially avoided. 
The peeling blades 4 employed in the stripping are, as is apparent from 
FIGS. 2 and 3, knife-like in shape and have an advantageously bluntish and 
narrow point. The stripping motion of the peeling blades 4 is 
advantageously started vertically near the upper edge of the precipitate 
layer 6a, and the blades are driven, controlled by the control members 8, 
along the determined surface profile of the cathode sheet 1 so that the 
points of the peeling blades 4 are kept essentially near to the sheet 
surface also in the corroded zone of the sheet 1. Thus the peeling blades 
are essentially simultaneously driven both vertically and in depth in 
order to achieve an advantageous realization of the invention.