Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
This invention relates to the electrowinning of
metals and, more particularly, relates to a device for
bypassing the current to one or more electrolytic cells in a
cell house.
In the electrowinning of metals, current is fed to
rows of electrolytic cells via bus bars and the current flows
through the alternating anodes and cathodes which are
supported in each cell on electrode contact bars positioned on
the cell walls. It is necessary, from time to time, to clean
out the electrolytic cells, to replace a cell and to carry out
cell maintenance work. In order to avoid having to shut down
an entire row of cells, the current is jumped or shunted for
one or more selected cells so that the current bypasses those
cells and the electrodes can be removed without interrupting
the electrolytic process in the remainder of the cells.
Devices and methods for current bypass of
electrolytic cells are known. According to U.S. Patent 3 432
422~ slotted L-shaped inter-cell connecting bus bars,
connected to copper anode bus bars of diaphragm electrolytic
cells for electrolysis of alkali-metal chloride brines,
provide for simplified removal of one cell from a series
without the use of a conventional jumper bar. According to
U.S. Patent 3 494 850, a device for short-circuiting a cell in
a series of series-connected movable mercury cathode
electrolytic cells comprises a row of tulip contacts directly
on a sole plate of the cell and knives engageable with the
contacts of an adjacent cell by flexible means. A power
operated mechanism provides the` engagement whereby the cell is
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short-circuited. According to U.S. Patents 3-930 978 and
4 078 984, a portable jumper switch is provided beneath a row
of cells permitting a cell to be taken out of production by
conducting the current through the jumper switch without
interrupting continuous operation of the other cells~
According to U.S. Patent 4 227 987, a jumper system for
bypassing one of a series of chloralkali diaphragm cells
includes two L-shaped conductors, a switch for electrically
connecting the conductors and a contact pressuring device for
10 remotely moving the conductors into contact with the cell
preceding and the cell following the cell to be disconnected.
The devices according to these patents are used mainly in
relation to brine electrolysis and are not useful or practical
for application in processes for the electrowinning of metals.
In electrowinning processesl cell bus bars or
shorting bars are used to cause current to bypass a cell. For
example, it is disclosed in U.S. Patent 3 579 431 that certain
bus bars used for supporting the header bars of the
alternating cathodes and anodes are enlarged in cross-section
20 and extended longitudinally to assist in forming a shunt
across several cells during a repair cycle. In a large cell
house,`many of these enlarged bus bars must be permanently
installed to allow repair of any selected cell. This requires
high capital investment. ~ccording to U.S. patent 3 929 614,
large size conductor bars are used in addition to normal-sized
electric conductors, both types being positioned on the cell
walls. Shorting electric conductors can be connected to the
large size bars for shorting the cell wall conductors so that
electrodes can be removed from the cell so shorted. The use
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-shorting bars must be large enough to carry the full current
applied to a row of cells. For very large currents such as,
for example, higher than 15000 Amperes, the enlarged bars and
the shorting bars became impractically heavy and large, which
interferes with the efficient operation of the cellhouse.
SUMMARY OF THE - INVENTION
It has now been found that the disadvantages of prior
art processes can be alleviated by providing a portable
current bypass assembly, which can be placed over and on top
of one or more cells to be repaired or cleaned. The portable
assembly can be moved to any desired location in the cell
house and the need for a large number of enlarged bus bars and
shorting bars is eliminated, thereby considerably reducing
capital cost. No interference with process efficiency is
encountered. The current bypass assembly consists of a
rectangular or square-shaped frame of bus bars, which are
large enough in cross-section to carry the current supplied to
a row of cells. The frame has means for being transferred by
crane and has placing means for accurately placing and
locating the bypass assembly in relation to electrolytic
cells. The frame is also provided with contact means for
establishing electrical contact between the bypass assembly
and the electrode contact bars positioned on the cell walls.
Accordingly, there is provided a portable current
bypass assembly for electrolytic metal winning cells in series
having cell electrode contact bars mounted on cell walls
comprising, in combination, a rectangular frame formed of an
electrically conductive metal having sufficient length to
straddle at least three consecutive cells; a pair of an inner
and an outer current collector bus bars forming part of said
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frame at each end of said frame, one of said pairs functioning
as an anode current collector bus bar at one end of the frame
and the other of said pair functioning as a cathode current
collector bus bar at the other end of the frame; locating
means secured to said frame for accurately placing and
locating said bypass assembly in relation to the cells to be
bypassed; a plurality of equi- spaced support means secured to
the outer current collector bus bars at each end of the frame
assembly; and contact means removably supported by the said
support means for establishing electrical contact between the
bypass assembly and cell electrode contact bars.
The locating means comprise a pair of spaced-apart
locating pin-bracket assemblies secured to each outer
collector bus bar at each end of the assembly, a pinbracket
assembly preferably secured to the outer collector bus bar in
proximity to each corner of the frame, each said pin-bracket
assembly having a downwardly projecting pin adapted to be
seated in a mating socket formed in a cell wall, and means for
laterally adjusting each said pin for selectively aligning the
bypass assembly with the cells to the electrode permit the
contact means to engage the cell electrode contact bars.
Guide means are positioned off-centre in each pin-bracket
assembly whereby turning of said guide means through 180
locates the guide means in one of a pair of laterally off-set
positions for aligning the bypass assembly with the cells.
The support means comprise a plurality of equi-spaced
brackets secured to each of the outer collector bus bars, each
bracket having a horizontal spool contact bar secured thereto,
and electrically conductive fingers ~dapted to be inserted
into said brackets for contact with said spool contact bar
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secured to the bracket and for contact with a cell electrode
contact bar.
BRIEF DESC~IPTION OF THE DRAWINGS
The invention will now be described with reference to
the accompanying drawings wherein:
Figure 1 is a plan view of two cell rows of opposite
polarity, in a circuit, showing current
bypass assemblies of the invention in their
two operative positions;
Figure 2 is a plan view of the current bypass
assembly shown in Figure l;
Figure 3 is an end elevation taken along the line
3-3 of Figure 2 with contact fingers
removed;
Figure 4 is a side elevation, partly in section,
taken along line 4-4 of Figure 2;
Figure 5 is a perspective view of a corner of the
bypass assembly of the invention;
Figure 6 is a perspective view of a locating pin
2b assembly and an adjacent finger support
bracket;
Figure 7 is a perspective view of the locating pin
assembly shown in Figure 6 with the
locating pin partially raised;
Figure 8 is a perspective view, partially cut away,
of a finger support bracket with a section
of spool bar; and
Figure 9 is a perspective view of a contact finger
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DESCRIPTION OF THE PREFER~ED EMBODIMENT
.
The current bypass assembly of the invention
generally depicted by the numeral 10 as shown in Figure 2
consists of the two "concentric" rectangular frames comprising
an inner frame generally indicated with 12 and an outer frame
generally indicated with 14 of bus bars which frames may be
elongated or square in plan. The two frames 12, 14 are formed
of suitable electrically conductive metal such as, for
example, aluminum or copper and are narrowly spaced apart from
each other by transverse metal spacers 1~ welded to the frames
to ensure that a narrow gap exists between the said frames.
The opposite ends 18, 20 of the assembly have a plurality of
closely spaced spacers 16 for reasons which will become
apparent as the description proceeds. Each corner of the
assembly has a diagonal brace 22 to provide additional
rigidity to the structure.
Each of the ends 18, 20 of the frame assembly has an
outer current collector bus bar 24 and an inner current
collector bus bar 26 defined by the outer and inner frames
respectively, one end of the frame functioning as an
anode-current collector bus bar and the other end of the frame
functioning as a cathode-current collector bus bar. The two
opposite sides 28, 30 of the frame assembly in like manner
comprise an outer carrier bus bar 32 and an inner carrier bus
bar 34~
The bypass assembly can be lifted, transported and
lowered by means of a chain sling 35 having a pair of
diverging extensions 36, 38 at each end secured by means of a
conventional eye hook, chain shackle and lifting pin depicted
0 by numeral 40 near each corner of the assembly.
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The lengths of the bus bars 32, 34 which comprise the
sides 28, 30 of the assembly can vary depending on the number
of cells to be by-passed. The shortest length must permit the
straddling of three cells by the assembly. The assembly
illustrated is designed to straddle five cells but it is
understood that the upper limit of the length of the assembly
is determined by practical consideration such as ease of
handling and weight restrictions.
With reference to Fig.3, the opposite ends 42, 44 of
the current collector bus bars 24, 26 are slightly raised
above the upper edges 46 of the operative central portions of
bars 24, 26 so that bus bars 32~ 34 clear piping at each cell
and to facilitate seating of side bars 32, 34 on supports 48,
50. A locating pin-bracket assembly 52 is secured by bolts to
the outer collector bus bars 24 at each end of the assembly in
proximity to each corner for precisely locating the assembly
over electrolytic cells.
With reference now to Figures 6 and 7, each locating
pin-bracket assembly 52 comprises a back plate 54 by which it
is bolted onto a current collector bus bar 24. A pair of
opposed side plates 56, 58 are welded to back plate 54 at one
end and rigidly secured a fixed distance apart at the opposite
end by an intermediate, transverse vertical plate 60 and a
transverse horizontal bottom plate 62 both welded to side
plates 56, 58, and an upper transverse guide plate 64 having
downwardly depending end flanges 66 for bolting of the said
upper guide plate to side plates 56, 58. A locating pin
housing depicted by numeral 67 comprises the opposing ends of
side plates 56, 58, transverse vertical plate 60, upper and
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lower plates 64, 62, and vertical front guides 68 welded to
the inner faces.
The locating pin 69 consists of an elongated
star-shaped lower portion 70 secured to the underside of
rectangular guide plate 72 which is adapted to slide
vertically within housing 67 guided by vertical rod 74 coaxiàl
with pin lower portion 70 extending upwardly from plate 72
through bushing 76 mounted off-centre in transverse upper
guide plate 64. Bushing 76 in upper guide plate 64 maintains
locating pin lower portion 70 within elongated opening 76
formed transversely in lower plate 62, shown most clearly in
Figure 7. Vertical travel of locating pin 69 is restricted to
its upper limit by upper guide plate 64 and its lower extent
of travel is determined by the seating of the transverse guide
plates 72 on lower plate 62. Each locating pin 69 is offset
laterally from the centre of the locating pin housing 67 and
can be readily moved to the opposite side of transverse
opening 76 by removing bolts 80, turning upper guide plate 64
through 180, and resecuring upper guide plate 6~ to the
side plates 56, 58 with locating pin 69 ad~acent the opposite
end of the slot 76.
With reference now to Figure 1, the current bypass
assembly 10 is shown located in two rows of cells which are
generally arranged in a U-shaped pattern with a current flow
depicted by the arrows 80, 82, cathodes being depicted by
solid lines 81 and anodes by broken lines 83. Two lateral
positions for the current bypass assembly are necessary for
the alignment of the bypass assembly with the electrodes, the
upstream end of the assembly having the cathode-current
0 collector bus bars 92 and contact means to be described for
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electrical contact with cathode contact bars and the
downstream end of the assembly having the anode-current
collector bus bars 90 and said contact means for electrical
contact with anode contact bars in the adjacent electrolytic
cells. By selectively positioning the locating pins to the
desired lateral position in housings 67, the whole bypass
assembly 10 is moved laterally the distance between an anode
and a cathode in the electrolytic cells, thereby aligning the
assembly as desired in relation to the contact bars in
upstream and downstream cells in various rows without rotation
of the bypass assembly.
With reference now to Figure 5, 6 and 8, a plurality
of contact plates 100 are secured by bolts to the outer anode
and cathode current collector bars 24. A total of twenty-six
equi-spaced contact plates are secured, side by side, to the
cathode current collector bus bar. Each contact plate 100 has
an outwardly extending lower flange 102, shown most clearly in
Figure 8, which supports a small section of spool contact bar
104 preferably screwed and brazed onto the upper surface of
flange 102. Spool contact bars 104 conveniently consist of
sections of a cell electrode contact bar cut in half along its
longitudimal centre line. Each section of contact bar mounted
on plate flange 102 has three equally spaced grooves 108 which
provide contact with contact fingers 120, to be described.
A finger support bracket 110 is screwed onto each of
contact plates 100. Each bracket 110 comprises a mounting
base 112 adapted to be bolted to contact plate 100 and two
pairs 113 of outwardly extending spaced apart support members
114 havir.g a transverse angle section 116 welded to the distal
ends thereof. Opposing members 114 of each pair 113 have
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outwardly flared upper edges 115 to facilitate the insertion
of fingers 120, shown most clearly in Figure 9.
On the anode current collector bus bar are bolted
twenty-four contact plates 100 and corresponding support
brackets 112 identical to those on the cathode current
collector bus bar and, in addition, a slightly larger contact
plate and support bracket are mounted in the centre of the
twenty-four contact platès 100. The centre finger support
bracket is capable of accommodating three fingers and the
corresponding section of spool contact bar 104 has five
equally spaced grooves 108 formed thereon. The contact plates
100 mounted on the cathode current collector bus bar are
positioned such that no finger 120 is situated on the centre
line of the assembly. However, the anode current collector
bus bar has the larger contact plate capable of receiving
three fingers centrally located such that a centre finger is
on the centre line of the anode current collector bus bar.
The reversal of the pin locator as described above
moves the bypass assembly laterally the distance between an
anode and a cathode to make the former cathode collector bus
bar the anode bus bar and vice versa. The cathode bar thus in
effect becomes the anode bar in the laterally moved position
and has a finger in the centre line of the assembly whereas
the former anode bar is now the cathode bar and has no finger
on its centre line.
The contact fingers 120 shown in Figures 5 and 9 are
adapted to freely slide vertically in and out of the finger
support brackets 110. Each finger 120 has an upper portion
with a hand grip fabricated of antimonial lead and a lower
0 contact portion fabricated from copper. Each finger has a
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V-notch 122 formed in its bottom edge at one end which is
adapted to make contact with a grooved portion 108 of the
spool contact bar 104 on the contact plate flange 102 and has
an extended portion with flat surface 124 on its bottom edge
at the other end which is adapted to make contact in a groove
of an aligned cell electrode contact bar on the cell wall, not
shown. The fingers are sufficiently heavy, for example, 28.8
kg each, to provide good pressure contact with the spool
contact bars 104 and the cell electrode contact bar, resulting
in uniform low resistance and an even distribution of
current. Shoulder 126 formed on the outer end of finger 120
is adapted to remain above the height of flange 116, as shown
most clearly in Figure 5, such that the weight of the finger
is continually maintained on the cell contact bar.
In operation, the current bypass assembly shown in
Figure 1 is positioned over a row of electrolytic cells to
straddle five of cells 140, 142, 144, 146 and 148. The
locating pins 69 are seated in mating sockets 150 to precisely
position the bypass assembly over the cell walls such that the
fingers supported on the cathode current collector bus bar are
in alignment with the cathode contact bars and the fingers on
the anode current collector bus bar are in alignment with the
anode contact bars in the adjacent cells, as shown most
clearly in Figures 3 and 4. Current has been previously shut
off to the cell rows and cathodes have been removed from cell
140 and anodes from cell 148 such that the respective fingers
120 fit in the now empty cathode and anode grooves of the cell
electrode contact bars on the adjacent cells.
Once proper mechanical contact has been established,
the chain sling 35 is disconnected from the craner and the
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crane is then available to removeJ for example, the cathodes
from cell 146. Power is again switched on for the system and
electrolysis continues while power bypasses the five cells now
inactivated.
The remaining electrodes are removed from cell 146
and the cell is now ready for cleaning out or other
maintenance work. Upon completion of work at cell 146,
electrodes are lifted from cell 144 and placed in cell 146,
permitting work to be carried out at cell 144. This procedure
is repeated until cells 142, 144 and 146 are cleaned and, once
all work is completed, current is again switched oEf, the
crane removes the bypass assembly, and subsequently replaces
the cathodes and anodes in cells 140 and 148 respectively,
permitting the current to be again switched on and the
; electrowinning process continued.
It will be understood, of course, that modifications
can be made in the embodiment of the invention illustrated and
described herein without departing from the scope and purview
of the invention as defined by the appended claims. For
example, the two connecting frames of bus bars can be closed
at the top and the bottom and the spacers can be provided with
holes or passages, so that four closed channels or tubuler
bodies are formed. With suitable connection for admitting
water or air to the channels, the assembly can be water or
air-cooled. Water or air cooling allows a reduction in the
cross-sectional area of each of the bus bars and thus reduces
the weight of the assembly.
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