Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: MOBILE ZINC CATHODE STRIPPING SYSTEM
FIELD OF THE INVENTION
This invention relates to the field of metal production and extraction,
and in particular, to the extraction and production of zinc.
BACKGROUND OF THE INVENTION
Z:inc is commonpy refined by electrolysis. In a typical process, a
number of plate cathocies are each inserted into a separate electrolytic cell.
The electrolytic cell contains a chemical solution which includes zinc. An
electric field is applied to the cell and zinc is deposited on the cathode up
to
the height at which the cathode is submerged in the electrolytic cell. The
zinc forrns a sheet or count on the cathode. The upper edge of the zinc
sheet is located at the "solution line" of the cathode, the line below which
the
cathode was submerged in the zinc solution. In order to harvest the zinc
which has been deposited on the cathodes, it is necessary to separate the
zinc sheets from the cathodes.
T'his removal is. typically done by a zinc sheet stripping machine.
Typically, the cathodes are removed from the cells, and are taken to the zinc
stripping machine, which strips the zinc sheets from the cathodes. The
cathodes are then returned to the cells to undergo the electrolytic process
again, while the removed zinc sheets are gathered and stored.
This zinc strippiing machine will, over time, physically damage the
cathode and render it unfit for continued use in the electrolytic process.
Since the cathodes are capable of being used over and over in the
electrolytic process, it is most economical if the cathodes have a longer
life.
The more frequently the cathodes need to be replaced, the higher the cost
to the producer. Thus, erosion, scratching and other damage to cathodes
is a continuing problerri for zinc producers.
Also, the electrolytic process operates by the application of a current
between pairs of cathodes and anodes in the electrolytic cells. It is the
electrical potential between the cathodes and anodes that causes the zinc
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to deposit on the cathodes. Such electroplating is most efficient when the
cathodes and anodes are clean and free of surface impurities. For example,
dirt on the surface of the cathode can affect the electrical currents
preventing the plating of the zinc on the cathode in the dirty areas. Thus,
zinc producers also have the problem of needing to keep the cathodes clean
in an efficient manner.
Another probleim for zinc producers and their employees is the
significant amount of noise that is created in the harvesting of zinc from the
cathodes. The cathodes themselves, the zinc sheets being removed from
them, and the machinery used to remove the zinc sheets are all metallic.
Thus, when these things come in repeated contact with one another, a great
deal of noise can be generated.
Some zinc extraction plants have fixed installations for removing the
zinc from the cathodes. Such fixed installations are often used in larger
plants, where the cost of a larger fixed installation is justified. Also,
typically,
fixed installations are appropriate where there is a significant amount of
space available for the zinc extraction process. In a fixed installation, the
cathodes are typically fed into the input end of the fixed stripping
installation,
and theri are moved through various parts of the machine, during which time
the zinc sheets are stripped and the cathodes are carried to the output end
of the fixed installation.
There are cases, however, where it is uneconomical to have a fixed
zinc sheet removal installation. There are also cases where the zinc
producer is confronted with floor space so limited as to preclude the use of
a fixed installation. In such cases, it is preferable to have a mobile zinc
stripping system which can be moved between various different groups of
electrolytic cells and used to strip the cathodes adjacent to such
electrolytic
cells.
Canadian Patent No. 2,178,776 discloses a mobile automated
cathode stripping system. The system includes a support frame for
supporting a plurality of cathodes hanging vertically in parallel alignment
with
one another. The system further includes a stripping mechanism including
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a carriage framework mounted for linear movement along the support frame.
The stripping mechanism includes a single pivotable stripping arm assembly.
The assembly provides a pair of stripping knives, one for each side of each
cathode, which wedge underneath the zinc sheet at the top corner of the
sheet. The knives then move in an arc along the cathode under the zinc
sheet, thus stripping the zinc sheet from the cathode and allowing it to fall
by gravity. The zinc sheets are then moved into a receiving bin, and when
the bin is full, the stack is moved to another location to be picked up by a
lift
truck and carried away. Jet spray heads are provided on the carriage which
carries the stripping arm assembly. The purpose of the jet spray heads is
to spray water at the zinc sheets and at the aluminum cathodes after they
have been stripped, in an attempt to clean them. The jet spray heads are
suspended above the cathodes, and spray water downward at a 45 angle.
However, the system described in Canadian Patent No. 2,178,776
suffers from a number of defects. First, each side of the cathode is stripped
by a single knife which traverses the entire vertical length of the cathodes.
Such a stripping method erodes the aluminum cathodes unnecessarily, thus
limiting their life.
Second, the water spray is not particularly effective, by itself, in
cleaning the cathodes. This is particularly true in respect of any impurities
which are stuck to the cathode. Such dirt may tend to stick despite the flow
of water over them. Third, the device is awkward and difficult to use,
because of the nature of the receiving bin for the stripped sheets.
U.S. patent number 5,269,897 discloses an installation for removing
the zinc deposited by electrolysis on aluminum plates. The installation
includes a storage zone for coated cathodes, a scraping zone and a storage
zone forzinc-free cathodes, with the cathodes being displaced consecutively
from one zone to the next. The scraping zone includes a horizontally acting
lateral piercer that separates the upper edge of the sheets of deposited zinc
from the cathodes, and a vertically acting scraping device for removing all
of the zinc sheets. The upper edge is separated by the lateral piercer being
initially inserted under the zinc sheet. The heads of the piercer are then
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initially iinserted under the zinc sheet. The heads of the piercer are then
adjusted so that they rio longer rest upon the cathode as the remainder of
the upper edge is separated, thus reducing contact between the piercer and
the cathode, and reducing damage to the cathode.
This patent, however, discloses a fixed installation where the
cathodes are carriecl through the stripping device. Thus, the device
disclosed in US patent number 5,269,897 is not appropriate for use where
space is limited or where the cost of a fixed system is not justified.
SUMMARY OF THE INVENTION
Therefore, what is desired is a mobile zinc stripping machine that is
effective in stripping ziric sheets from cathodes. The machine of the present
invention will preferably operate so as to minimize damage to the cathodes
during operation. It wilN also preferably be space efficient, be constructed
so
as to reduce the noise generated during the zinc stripping process, and be
constructed so as to be able to effectively clean the cathodes after
stripping.
Therefore, according to one aspect of the invention there is provided
a device for stripping zinc sheets from cathodes, the device comprising:
a moveable base frame for moving the device along a floor;
a cathode support frame, coupled to the moveable base frame, the
cathode support frame being sized, shaped and positioned to support the
cathodes during stripping;
a stripping assembly for stripping the zinc sheets from the cathodes,
the stripping assembly being movably coupled to the base frame and being
moveable relative to ithe cathode support frame to permit the stripping
assembly to strip each cathode supported in the cathode support frame;
at least one power source coupled to the base frame and operatively
connected to the stripping assembly;
ttie stripping assembly including a lateral stripper, movable across the
cathodes in the cathocle support frame, for separating an upper edge of a
zinc sheet from each of the cathodes, the lateral stripper being adapted to
bias away from the cathode immediately upon entering between the zinc
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sheet and the cathode, and a scraping device, movable in a direction
generally perpendicular to a direction of the lateral piercer, for completing
removaN of the sheet from each said cathode.
According to a further aspect of the invention, there is provided a
device for stripping zinic sheets from cathodes, the device comprising:
a moveable base frame for moving the device along a floor;
a cathode support frame, coupled to the moveable base frame, the
cathode support frame being sized, shaped and positioned to support the
cathodes during stripping;
a stripping assembly for stripping the zinc sheets from the cathodes,
the stripping assembly being movably coupled to the base frame and being
moveable relative to the cathode support frame to permit the stripping
assembly to strip each cathode supported in the cathode support frame;
a bottom-up stacker assembly coupled to the base frame;
a sheet carriei, for transporting the zinc sheets to the stacker
assembly, the sheet carrier being positioned so as to receive the zinc sheets
when they are stripped, the stacker assembly being adapted to create a
stack from the zinc sheets carried on the sheet carrier; and
at least one power source coupled to the base frame and operatively
connected to the stripping assembly, to the sheet carrier and to the stacker
assembly.
According to a further aspect of the invention, there is provided a
device for stripping zinc sheets from cathodes, the device comprising:
a moveable base frame for moving the device along a floor;
ai cathode support frame coupled to the base frame, the cathode
support frame being sized, shaped and positioned to support the cathodes
during stripping;
a stripping assembly for stripping the zinc sheets from the cathodes,
the stripping assembly being movably coupled to the base frame and being
moveable relative to the cathode support frame to permit the stripping
assembly to strip each cathode supported in the cathode support frame;
at least one cathiode cleaner, movably coupled to the base frame, the
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cathode cleaner being movable along the cathode support frame and along
each said cathode so as to permit the cathode cleaner to clean each
cathode supported on the cathode support frame; and
at least one power source coupled to the base frame and operatively
connected to the stripping assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
To facilitate a better understanding of the invention, a preferred
embodiment will now be described with reference to the drawings in which:
Figure 1 is a side view of a typical cathode used in association with
the present invention;
Figure 2 is a side view of the preferred embodiment of the mobile zinc
stripping device;
Figure 3 is a plan view of the preferred embodiment of the mobile zinc
stripping device;
Figure 4 is an end view of the preferred embodiment of the mobile
zinc stripping device from the cathode support frame end;
Figure 5 is an end view of the preferred embodiment of the mobile
zinc stripping device from the stacker assembly end;
Figure 6 is a rear view of the stacker assembly with details of the
device removed for clarity;
Figure 7 shows the scraping device in operation;
Figure 8 is a plan view of the lateral stripper;
Figure 9 is a longitudinal cross-section of the lateral stripper, taken
along line IX-IX of Figure 8;
Figure 10 is a transverse cross-section along the line X-X of Figure
8;
Figure 11 is a transverse cross-section along the line XI-XI of Figure
8;
Figure 12 is a cross-section along the line XII-XII of Figure 8;
Figure 13 is a plan view of the arms of the lateral stripper;
Figure 14 is a partial plan view of the lateral stripper table, in which
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the arms of the stripper have been removed; and
Figure 15 is a cross-section along the line XV-XV of Figure 14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, the preferred form of cathode for use in
accordance with the present invention is shown. The cathode 10 includes
an alurninum plate 12, a support bar 14, and carrying hooks 16. The
aluminum plate 12 is preferably 50-60 inches long, 30-32 inches wide, and
0.25 inches thick. The plate 12 is immersed in an electrolytic cell and the
zinc sheet 17 is created on both sides of the plate 12.
The cathode 10 also include a dielectric region 18. Because the
dielectric is electrically neutral, no zinc adheres to the dielectric region
18.
The plate 12 has side edges 20, 22, and a bottom edge 24. In the preferred
form of cathode, the side edges 20, 22 are also coated with a dielectric, but
the bottom edge 24 is not. Thus, zinc coats the bottom edge 24 during the
electrol,ytic process, but not the side edges 20, 22. The result is a zinc
sheet
that has an overall V-shape. The zinc sheet 17 covers both flat sides of the
plate 12 as well as the bottom edge 24, but not the side edges 20, 22.
Fteferring now to Figures 2 - 6, the first step in stripping the zinc
sheets 17 from the cathodes 10 is to remove a number of the cathodes 10
from the electrolytic cell and place them in the cathode support frame 26.
The cathode support frame 26 is sized, shaped and positioned to support
the cathodes during stripping. In the preferred embodiment, the cathode
support frame 26 comprises a continuous notched beam 28 on one side of
the devdce, and, on the other, a series of spaced upright beams 30 having
saddles or notches thereon. This configuration allows multiple cathodes 10
to be side loaded into the cathode support frame 26 through the spaces
between the upright beams 30.
The notched beam 28 and the upright beams 30 are coupled to the
base frame 31. The base frame 31 acts as the base for all of the
components of the device described herein.
To load the cathodes 10 into the cathode support frame 26, a grabber
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(not shown) is used to lift the cathodes 10 out of an electrolytic cell. The
grabber grasps the carrying hooks 16 of each cathode 10. Preferably, the
cathodes 10 are loaded into the cathode support frame 26 in groups of
fifteen.
The notches of the notched beam 28 and the upright beams 30 are
sized and spaced such that one end of the support bar 14 sits securely in a
notch of the notched beam 28, while the other ends sits securely in a notch
of an upright beam 30. Each cathode 10 is thus held in place.
In the preferred embodiment, there are thirty cathode slots in the
cathode support frame 26. When the cathodes 10 are loaded into the
cathode support frame 26, they are preferably loaded into every second slot.
If the cathode support frame 26 already contains cathodes 10 that have
been stripped, then the new cathodes 10 which are about to be stripped can
be loaded into the cathode support frame 26, and the stripped cathodes 10
can be removed immediately thereafter. Thus, loading the cathodes 10 into
every second slot of the cathode support frame 26 allows for efficient use to
be made of the machinery and labour used to load the cathodes 10 in and
out of the cathode support frame 26. It will be appreciated by those skilled
in the art that other configurations of the cathode support frame 26 are
comprehended by the present invention. What is needed is to provide a
cathode support frame 26 which is sized, shaped and positioned to suitably
support cathodes during stripping.
Next, the cathodes 10 are stripped by the stripping assembly 32. The
stripping assembly 32 includes a lateral stripper 34 and a vertical scraping
device 36. The lateral stripper 34 is carried by a stripper carriage 38 and
the
scraping device 36 by a scraping device carriage 39. Both carriages 38 and
39 are movably mounted on two carriage rails 40 and 42 coupled to the base
frame 31.
It will be appreciated that the carriages 38, 39 could ride on one
carriage rail, or on more than two carriage rails. However, two carriage rails
are preferred because! such a configuration balances the need to provide
adequate stability for the carriage 38 while not using up too much space.
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It will be appreciated that the stripper 34 and scraping device 36 can
be carried by any carriage assembly which allows them to move
appropriately. However, the two carriage configuration (carriages 38, 39 as
the carriage assembly) is preferred over, say, a single carriage, because it
allows for a smaller device, given that the stripper 34 and scraping device 36
are separate (i.e. the scraping device trails the stripper).
The stripping assembly 32 operates as follows. The carriage 38
moves along the cathode support frame 26 to a position adjacent to each
hanging cathode where the lateral stripper 34 and scraping device 36 strip
each cathode 10 in turn. For each cathode 10, the first stage of stripping is
performed by the lateral stripper 34.
The design of ttie lateral stripper 34 will be explained with reference
to Figures 8 to 15.
Fteferring first to Figures 8 to 12, the lateral stripper consists of two
equal horizontal arms, referenced with numbers 224 and 225, mounted with
the ability to be longitudinally displaced along a table 226. These arms are
connected to a rear actuating hydraulic cylinder 227 and their forward ends
are wecige-shaped stripper heads 228 that define vertical tapered edges
229. The stripper 34 is located in a position facing one of the cathodes in
the cathode support frame 26, in such a way that the arms 224 and 225 are
located one on each side of a cathode 10. The stripper 34 is also situated
at a height such that the tapered edges 229 of the arms 224 and 225 are at
the height of the upper edge of the zinc sheets 17 stuck to the cathodes 10.
As can be seen in Figures 8 to 10, the rod of the cylinder 227 is
connected to a transverse head 230, the ends of which are connected to the
arms 224 and 225. Tlhis head has a lower protuberance 231 that can be
displaced along a longitudinal channel 232 formed in the table 226. In order
to guide the longitudinal displacement of the arms 224 and 225, the table
226 also has fixed longitudinal guides 233 and freely rotating rear rollers
234.
As can be seen in Figures 8, 9 and 12, mounted on the forward part
of the table 226 are two lateral pushrods that drive the arms 224 against
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each other. Each of these pushrods consists of a rod 235 linked by one of
its ends 236 to a fixed point, while the other end has a freely rotating
roller
237 supported against the adjacent arm. Acting on the rod 235 is a cylinder
238, whose action causes the arms 224 and 225 to approach each other.
As can be seeri in Figures 8, 9, 14 and 15, the table 226 forms an
enlargement in its forward part in which, starting from its upper surface, an
offset or slot 239 is created in which is mounted a support 240. This support
240 consists of a flat piece of width approximately equal to that of the slot
239 but with length slightly shorter, so that this piece is limited in its
upper
part by two transverse dividers 241 of length greater than the width of the
support 240. Starting from the transverse sides, the support 240 has two
facing blind drill-holes 242 which house compression springs 243 supported
against the shorter walls of the slot 239. These serve as centralizing
elements for the support 240.
The upper surface of the support 240 has two intermediate slots 244,
each of which opens into one of the longitudinal sides of the support 240.
These two intermediai:e slots 244 are slightly out of phase with each other
in the longitudinal direction of the support 240. Each of these slots 244 has
a centralizer 245. Each centralizer consists of a piece that is appreciably
flat, with a rectangular contour and of width approximately equal to that of
the slots 244 but with length shorter than these. Starting from a the side
facing outwards, the centralizers 245 have a blind drill-hole what houses a
compression spring 247 supported against the opposite wall of the slot 244.
Between their larger surfaces, the centralizers 245 also have a drill-hole 248
for mounting a freely rotating roller 249 (Figures 10 and 11) for adjusting
the
separation of the arms 224 and 225, as will be explained below.
The position of the centralizing pieces 245 can also be adjusted by
means of a threaded rod 250 that penetrates an opening 251 made in the
transverse sides of the: support 240 and which protrudes to the outside via
a hole or opening made in the wall limiting the slot 239 in the table. Mounted
on the ends of the dividers 241 of the support 240 are cylinders 238 that act
on the rods 235 responsible for moving the arms together.
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sides of the arms 224 and 225 have offsets or recessed steps 252 that
house the freely rotating rollers 249, defining the external vertical wall 253
of these offsets as rolling tracks for the rollers 249. The offsets 252 vary
in
width along a section 254, causing the edges 229 to become axially out of
phase by a distance equal to the separation distance between the rollers
249. As can be seen in Figure 8, the rollers 249 act on the track of the
opposite arms.
In this configuration, forthe arms 224 and 225 to act on the cathodes,
and starting from the position shown in Figure 8, the two arms begin to be
displaced without the cylinders 238 being actuated until the sides 229 of the
arms become located over the plate 12, one arm on each side, at the edge
of that plate. At that moment, the cylinders 238 are actuated and the arms
224 and 225 move together in such a way that the edges 229 are supported
on the surfaces of the cathode. The maximum distance of separation
between the arms 224 and 225 is regulated by the threaded rods 250.
Advancing in this position, the sides 229 of the arms start to scrape off the
zinc sheets deposited on the cathode 10. During this advance, when the
rollers 249 reach the ramps 254 of the tracks 253 on which these rollers are
supported, the arms 224 and 225 are caused to separate slightly in such a
way that the front sides 229 of the these arms no longer rest upon the
surface of the cathodes 10. Thus, the rollers 249 act as moving or biasing
elements to move or bias the heads 228 away from the cathode immediately
after the edges 229 enter under the zinc sheet 229. From that moment on,
the rapid advance of the arms -24 224 and 25 225 can be achieved, causing
the zinc sheets 17 to be detached without scratching the surfaces of the
cathodes. At a certain moment during the progress of the arms along the
cathode, which can be regulated as wished, the action of the cylinders 238
can be cut out, with which the springs 247 push against the pieces 245,
forcing the arms 224, 225 to become separated.
Because of the springs 243 and 247, the self-centring of the arms 224
and 225 over the cathodes is achieved, even when these blades start to
deviate over the cathodes.
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deviate over the cathodes.
VVith the system of centring the arms 224 and 225 and moving them
closer together, correct action is indeed achieved on the cathode for
removing the upper part of the zinc deposits and preventing erosion or
deterioration of the cathodes.
C)nce the upper edges 56, 58 of the zinc sheet 17 have been
liberated from the plate 12, the lateral stripper 34 moves back to its
original
position and the carriage 38 moves along the cathode support frame 26 so
as to permit the laterall stripper 34 to operate on subsequent cathodes 10.
Meanwhile, the scraping device 36 is carried by the carriage 39 such that it
trails the lateral stripper 34.
When the carriage 39 has moved into a position where the scraping
device 36 is directly above a cathode 10 which has already been acted upon
by the lateral stripper 34, the scraping device 36 then operates to completely
remove the zinc sheet 17 from the cathode 10 as explained below.
This process is shown in detail in Figure 7. The upper edges 56, 58
of the ziinc sheet 17 have already been bent away from the plate 12 by the
lateral stripper 34. The scraping device 36 then moves downwardly as
shown into the wide gap so created.
The scraping device 36 includes two scraping arms 60, 62 and two
scraping heads 64, 66, one for each side of the zinc sheet. As the scraping
arms 60, 62 move downwardly, the tips of the scraping heads 64, 66 enter
under the separated upper edges 56, 58 of the zinc sheet 17. As the
scraping arms 60, 62 proceed still further downwardly, the scraping heads
64, 66 rnake contact with the inner portions of the zinc sheet 17 and force
the zinc sheet 17 off the plate 12. The scraping arms 60, 62 are moved
downwardly until the entire zinc sheet 17 has been stripped free from the
plate 12.
1'he scraping heads 64, 66 are preferably positioned so that they do
not rest against or even contact the plate 12 as they progress downwardly.
This positioning significantly reduces the risk that the plate 12 will be
physically damaged by scratching or scoring. This positioning is made
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possible by the fact that the upper edges 56, 58 have already been
separated from the plate 12 by the lateral stripper 34 to form a wide gap.
Thus, the scraping heads 64, 66 can engage and strip the zinc sheet 17
without the heads 64, 66 needing to contact the plate 12.
In the preferred embodiment, the scraping heads 64, 66 have
roundecl edges 68, 70 for contacting the zinc sheet 17 so as to minimize
tearing or the like of the zinc sheet. Also, it is preferable to have, mounted
to each of the scraping heads 64, 66, a stainless steel brush 72, 74 on the
inside of the heads 64, 66. The stainless steel brushes 72, 74 are sized,
shaped and positioned so as to brush the cathode as the scraping heads 64,
66 move downwardly and strip the zinc sheet 17. The brushes 72, 74 trail
the edges 68, 70 of the heads 64, 66 as the zinc sheet 17 is stripped, and
they brush the plate 12. When the scraping device 36 is raised again to
prepare for stripping the next cathode 10, the brushes 72, 74 again brush
the plate 12. The brushes 72, 74 are preferably positioned such that each
one of brushes 72, 74 brushes one side of the plate 12.
I-t is preferable also that the scraping heads 64, 66 extend along the
entire width of the plate 12. This has two benefits. First, stripping can be
completed most efficiently if the force is exerted evenly across the zinc
sheet
17, which reduces the likelihood that the sheet will tear or buckle. Second,
the brushes 72, 74 mounted on the inside of the heads 64, 66 can extend
completely across the plate 12, thus providing a more thorough cleaning of
the plate 12. It will further be appreciated that the wedging force to strip
the
zinc sheet 17 provides a seating force for the brushes, causing good
cleaning contact.
It will be appreciated by those skilled in the art that, though the
stripping assembly described above is preferred for the reasons given, other
stripping assemblies rnay be used within the present invention. What is
important is that the device includes a stripping assembly 32 movably
coupled to the base frame 31, which is effective in stripping the zinc sheets
17 from the cathodes 10. The stripping assembly 32 should be movable
relative to the floor 76 on which the device sits, and relative to the cathode
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support frame 26 so as to permit the stripping assembly to strip the cathodes
wheri they are on the cathode support frame 26.
After the zinc sheets 17 are stripped from the cathodes 10, they drop
to the sheet carrier 78, which is positioned so as to receive the zinc sheet
17
5 when ttiey are stripped. The sheet carrier 78 preferably comprises a
conveyor belt 80 operatively coupled to a pair of drive shafts 82, which
shafts drive the conveyor belt 80 by rotating.
As shown in Figure 2, preferably the zinc sheets 17 which have been
stripped have a "V" or "taco" shape. As the sheets 17 contact the conveyor
10 belt 80, the sheets 17 are typically tipped sideways by the motion of the
conveyor belt 80 and carried toward the stacker assembly 84, which stacker
assembly is coupled to the base frame 31.
As the conveyor belt 80 carries the sheets 17 to the stacker assembly
84, the sheets 17 are preferably flattened and prepared for stacking by
passing under the pinch roller 86. The pinch roller 86 is coupled to the base
frame 31 and positioned at the end of the conveyor belt 80, and just above
the conveyor belt 80. The pinch roller 86 allows the zinc sheets 17 to
proceed to the stacker assembly 84, but at the same time, flattens the zinc
sheets 17 (i.e. closes the "V" of the V-shaped zinc sheets) as they are
carried to the stacker assembly 84 by the conveyor belt 80.
I-t will be appreciated that, though this structure for the sheet carrier
78 is preferred, it is not required for the present invention. Rather, any
sheet
carrier 78 for transporting the zinc sheets 17 to the stacker assembly 84 will
suffice if the sheet carrier 78 is positioned so as to receive the zinc sheets
17 when they are stripped.
1"he stacker assembly 84 is preferably a bottom-up stacker assembly,
i.e., adapted to create a stack 88 by a bottom-up stacking method. This
method is preferred because it allows for a saving of floor space, thus
allowing the device to have a smaller footprint. In top down stacking, the
zinc sheets 17 would need to be carried up to the top of the stack. This
would necessitate the greater use of floor space, as the conveyor belt 80
would need to extend further in order to carry the sheets diagonally upwardly
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to the top of the stack. By contrast, with bottom-up stacking, it is only
necessary to carry the zinc sheets 17 to the bottom of the stack 88, thus
shortening the required length of the conveyor belt 80 and rendering smaller
the overall footprint of the stripping device.
In the preferred embodiment, the stacking assembly comprises a
stack grasper in the form of a pair of arms 90, 92 having hook portions 94,
96 for grasping the stack 88 from below. The stacking assembly also
preferably comprises a lifting mechanism 98 coupled to the base frame 31
and the arms 90, 92.
l'o perform bottom up stacking, the arms 90, 92 grasp the stack 88
which is lifted by the lifting mechanism 98. An additional zinc sheet 17 is
then carried to the stacker assembly 84 by the conveyor belt 80, and the
stack 88 is then placed upon the additional zinc sheet 17 by the lifting
mechariism 98 being lowered, the arms 90, 92 opening to release the stack
88 onto the additional zinc sheet 17, and the arms 90, 92 closing again
under the additional zinc sheet 17. The additional zinc sheet 17 is thus
added to the stack 88.
It will be appreciated that this method of stacking is likely less noisy
than a top-down stacking method, because, in a top-down stacker, the
additiorial sheet will often fall onto the existing stack in a noisy manner.
By
contrast, in the preferred embodiment, the stack is placed (not dropped) on
the additional zinc sheet, and then the stack, including the recently added
sheet, is picked up again.
Also, the arms 90, 92 are preferably rotatably coupled to the base
frame 31, most preferably through a rotatable stacker shaft 100. The
rotatable stacker shaft 100, together with the arms 90, 92, act as a stack
rotator which can rotate the stack up to approximately 180 about the vertical
stacking axis in a plarie generally parallel to the floor 76. In the preferred
embodiment, the rotatable stacker shaft 100 is coupled to the base frame 31
at a point above the stack 88, such that when the shaft 100 rotates, the
stack 88 is rotated in a plane generally parallel to the floor 76.
Typically, the stack 88 will tend to become of uneven height across
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its width as more sheets 17 are added to the stack 88. In particular, the side
of the stack 88 where the closed ends of the sheets 17 are located will be
at a different height than the side where the open ends are, as more sheets
17 are added. One reason for this is that, during the electrolytic process,
the
zinc tends to flow slightly toward the bottom of the cathode 10. Thus, as
sheets 17 are added to the stack 88, it may become progressively more
lopsideci and unstable. However, by rotating the stack 88 when it is half
complete, the stack 88 can be balanced and rendered more stable. For this
reason, it is preferably that the device include a stack rotator, and most
preferably that it include the stack rotator described above.
The device also preferably includes a stack removal station 102
coupledl to the base frame. In the preferred embodiment, the arms 90, 92
are movable along the base frame 31 to and from the stack removal station
102 so that the arms 90, 92 can move a completed stack 88 to the stack
removal station 102.
The stack 88 is placed on the stack removal station 102 to allow the
stack 88 to be removed in order to make space for the next stack. In the
preferred embodiment, the stack removal station has a first lift truck access
and a second lift truck access. Most preferably, the first lift and second
lift
truck accesses comprise first and second pairs of hollows 104, 106 for
receiving the forks of a lift truck. Having two lift truck accesses provides
increased flexibility of loading in the event floor space is limited. Thus, in
a
tight space, there may be no room for a lift truck to approach the first lift
truck access. However, providing a second lift truck access creates another
route by which the lift truck can reach the stack 88 to be removed. Most
preferably, the two pairs of hollows 104, 106 are positioned at approximately
right angles to one another, so that the lift truck can access the stack 88
either from the end of the device or the side of the device.
The stacks 88 will typically, because of the shape of the sheets 17,
have a wider and a narrower dimension when seen in plan view. For greater
stability, the lift truck will preferably lift the stack 88 with its wider
dimension
across the forks and its narrower dimension parallel to them. Thus, in the
CA 02349394 2001-05-30
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preferred embodiment, the arms 90, 92 are adapted to rotate the stack
betweeri a first position to facilitate use of the first pair of hollows 104,
and
a second position to facilitate the use of the second pair of hollows 106,
where the second position is angularly displaced from the first position.
Most preferably, the first and second positions will be angularly displaced
from one another by about 90 .
In the preferred embodiment, the device further includes a scale 110
operatively coupled to the stack removal station 102 for sensing the weight
of a stack 88. most preferably, the stack removal station includes a platform
112, and the scale is positioned below the platform 112 such that the
gravitational force operating on the stack 88 is transmitted to the scale 110.
hiaving the scale 110 is useful for quality control purposes, so that the
zinc producer can tell what the variation is in the weight of the stacks 88,
and
for inventory control purposes, so that the producer can know how much
zinc it is producing, and how much it has in inventory. Thus, it is most
preferably if the scale 110 is connected to the producer's inventory and
quality control computer databases so as to efficiently provide the producer
with the required information.
I n order to make the stripping device mobile, the movable base frame
31 preferably includes a set of wheels 116 coupled to the base frame and
positioned so as to support the base frame on the floor. Most preferably, at
least two of the wheels 116 are connectable to a mobility power source,
such as a hydraulic or electrical power source, for moving the device.
Most preferably, the device operates automatically and is controlled
by at least one controller or more, if necessary or desirable, The controller
is preferably a Programmable Logic Controller 122 of the type generally
available for operating industrial machinery.
Also, preferably, the moving portions of the device are powered by at
least orie power source (which includes multiple power sources). Most
preferably, the power source is a hydraulic pump 120 which is operatively
connected to and thus powers the stripping assembly, stacking assembly,
sheet carrier and stack rotator. The hydraulic pump 120 may also be used
CA 02349394 2001-05-30
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to power the wheels 116.
V'Vhile the foregoing embodiments of the present invention have been
set forth in considerable detail for the purposes of making complete
disclosure of the invention, it will be apparent to those skilled in the art
that
various modifications can be made to the device without departing from the
scope of the invention as defined in the attached claims. Some of these
variations are discussed above and others will be apparent to those skilled
in the art. For example, the power source may be a source other than a
hydraulic pump, such as, for example, an electric motor. What is considered
important in the present invention is to provide a mobile zinc stripping
device
which, preferably: is floor-space-efficient, reduces the wear on the cathodes
being stripped, and provides a means for effectively cleaning the cathodes.
