Electrical conductor, process for manufacturing an electrical conductor and electrode for an electrolysis cell

Electrical conductor comprising a metallic bar (1) jacketed with a sheath (2) made from a metal different from that of the bar, in which the bar (1) exhibits at least one longitudinal groove (3, 3') containing a bead (4, 4') made from the same metal as the sheath (2), welded to the bar (1), and the sheath (2) exhibits an opening opposite the bead (4, 4'), the said opening containing a metallic mass (9, 9') welded to the bead (4, 4') and to the sheath (2). The conductor finds one application in electrodes comprising a metallic plate longitudinally fixed to an electrical conductor.

The present invention relates to an electrical conductor comprising a 
metallic bar jacketed with a sheath made from a metal different from that 
of the bar. 
Electrical conductors of this type are commonly used in the construction of 
electrodes intended for cells for the electrolysis of aqueous solutions, 
especially of sodium chloride solutions. In this application, they usually 
comprise a copper bar jacketed with a sheath made from a metal which is 
inert with respect to the chemical environment in the electrolysis cell, 
and they are inserted horizontally or vertically between a pair of 
vertical metallic plates forming the actual electrode. For example, in the 
case of cathodes intended for the electrolytic production of hydrogen and 
aqueous sodium hydroxide solutions, the metal of the sheath is generally 
chosen from iron, nickel and their alloys. The copper bar is used for its 
high electrical conductivity and consequently has the principal function 
of conveying high current densities, whereas the sheath serves to isolate 
the copper bar from the corrosive action of the electrolytes flowing in 
the electrolysis cell. The sheath furthermore provides the additional 
function of ensuring that the electrical current flows between the bar and 
the electrode plates. It is consequently desirable to reduce to a minimum 
the electrical contact resistance between the bar and the sheath. In order 
to achieve this objective, consideration has been given to using 
electrical conductors obtained by a metallurgical operation of coextrusion 
of the bar and the sheath. However, electrical conductors obtained by this 
technique are expensive. 
In U.S. Pat. No. 4,647,358, a more economical process is proposed for 
manufacturing an electrical conductor intended for the electrolytic 
refining of copper. According to this process, the copper bar and the 
sheath are manufactured separately, the latter being slit over its entire 
length, the bar is inserted into the sheath and the edges of the slit of 
the sheath are welded to each other. However, electrical conductors 
obtained by this known process have a very poor electrical conductivity at 
the contact surface between the bar and the sheath. 
The invention aims to overcome the abovementioned drawbacks by providing an 
electrical conductor formed from a bar jacketed with a sheath, which has a 
good electrical conductivity in the contact zone between the bar and the 
sheath and which is simple and economical to manufacture. 
Accordingly, the invention relates to an electrical conductor comprising a 
metallic bar jacketed with a sheath made from a metal different from that 
of the bar; according to the invention, the bar exhibits at least one 
longitudinal groove containing a bead made from the same metal as the 
sheath, welded to the bar, and the sheath exhibits an opening opposite the 
bead, the said opening containing a metallic mass welded to the bead and 
to the sheath. 
In the electrical conductor according to the invention, the metallic bar 
has the principal function of conducting the electrical current. The 
sheath fulfills two functions: on the one hand, it serves to isolate the 
bar from the chemical environment in which the electrical conductor is 
used; on the other hand, it serves to transfer the electrical current in 
the direction transverse to the bar between the latter and a metallic 
element (for example an electrode) connected to the sheath. 
The profile of the bar is not critical. It may, for example, consist of a 
cylinder of circular or oval cross-section, or of an elongate 
parallelepiped the cross-section of which is a square, a rectangle, a 
trapezium or any other polygon, regular or otherwise. For ease of 
construction, a rectilinear bar of square or rectangular cross-section is 
preferably used. According to the invention, the bar has a longitudinal 
groove. The latter may extend over the total length of the bar or over 
only a fraction of the latter. The groove serves as receptacle for a 
metallic bead constituted by the same metal or alloy as the sheath, this 
metallic bead being welded to the bar. 
The sheath must have a profile which is matched to the profile of the bar 
in such a manner that it can envelope it over approximately its total 
length. The profile of the sheath and its disposition around the bar must 
furthermore be such that the sheath has an opening opposite the metallic 
bead which is in the groove of the bar. The opening of the sheath may be a 
slot which extends over its total length or over only a portion of the 
latter. It serves as a receptacle for a metallic mass constituted by the 
same metal or alloy as the sheath, this metallic mass being welded to the 
bead and to the sheath. 
The metal of the sheath depends on the intended use of the electrical 
conductor. It must be chosen from those metals capable of being welded to 
the metal of the bar. 
In a particular embodiment of the electrical conductor according to the 
invention, the metallic bar is made from copper and the sheath is made 
from a metal chosen from iron, nickel, alloys of iron and alloys of 
nickel. The alloys of iron comprise ordinary carbon steels and alloyed 
steels such as, for example, stainless steels alloyed with chromium, 
nickel and molybdenum and steels alloyed with silicon which have special 
electrical properties. Examples of nickel alloys are Monel (alloy of 
nickel, copper, iron, manganese and silicon) and Inconel (alloy of nickel, 
manganese, iron, silicon, chromium, aluminium and titanium). The 
electrical conductors in accordance with this embodiment of the invention 
find particular application in the construction of cathodes intended for 
cells for electrolysis of aqueous alkali metal chloride solutions. 
In another embodiment of the electrical conductor according to the 
invention, the sheath is a metallic sheet folded around the bar in such a 
manner as to envelope the latter, and the abovementioned opening is a slot 
delimited between the two juxtaposed edges of the sheet. 
In a further embodiment of the electrical conductor according to the 
invention, the bar has two longitudinal grooves containing a bead made 
from the same metal as the sheath, and the sheath is formed from two 
separate trough-shaped longitudinal shells which longitudinally cover the 
bar while providing, between their longitudinal edges which face each 
other, a gap constituting the abovementioned opening opposite each bead. 
In this embodiment of the invention, the sheath consequently has two 
slot-shaped longitudinal openings which are located facing the beads and 
which contain two metallic masses such as defined above, welded 
respectively to the two beads and to the two shells. 
In the electrical conductor according to the invention, the bar is coupled 
to the sheath by a welded assembly, constituted by the abovementioned bead 
or beads and by the abovementioned metallic mass or masses. This welded 
assembly ensures an optimum electrical connection between the bar and the 
sheath and, as a consequence, reduces the resistance to the passage of the 
electrical current between the bar and the sheath. 
The invention also relates to a process for manufacturing an electrical 
conductor, by assembling a metallic bar and a sheath made from a metal 
different from that of the bar; according to the invention at least one 
longitudinal groove is made in the bar, a bead made from the same metal as 
the sheath is welded in the groove of the bar, the bar is inserted into 
the sheath by making an opening in the latter opposite the bead and the 
sheath is welded to the bead in the abovementioned opening. 
In the process according to the invention, the bar may be obtained, for 
example, by a metallurgical rolling operation. The groove may be formed in 
the bar during the rolling, or alternatively it may be formed subsequently 
by a machining operation. 
The sheath may be obtained by a rolling operation of the type which are 
used for the manufacture of metallic tubes, the abovementioned opening in 
the sheath then being obtained by machining. However, according to the 
invention, it is preferred to utilise a sheath obtained by folding or 
roll-bending a metallic sheet. For this purpose, in a particular 
embodiment of the process according to the invention, a sheath obtained by 
roll-bending or folding a metallic sheet is utilised and a gap forming the 
abovementioned opening, intended to contain the metallic mass, is left 
between the longitudinal edges of the roll-bent sheet. 
In another embodiment of the process according to the invention, two 
longitudinal grooves are made in the bar and a sheath obtained by placing 
the two longitudinal metallic shells together in such a manner as to leave 
a gap between their opposingly disposed edges, the said spacing forming 
the abovementioned opening. In this embodiment of the process according to 
the invention, the two shells have the shape of a trough and are obtained, 
for example, by deep-drawing a metallic sheet. 
The electrical conductor according to the invention is especially designed 
for the transport of the electrical current longitudinally in the bar and 
transversely through the sheath. It is suitable both for direct current 
and for alternating current. It finds one advantageous application in the 
construction of electrodes intended for electrolysis processes, such as 
iron, steel or nickel cathodes which are commonly used in processes for 
the electrolysis of water or of aqueous alkali-metal chloride solutions. 
The invention consequently also relates to an electrode for an electrolysis 
cell, comprising at least one plate made from a metal selected from iron, 
nickel, alloys of iron and alloys of nickel, the said plate being fixed to 
an electrical conductor according to the invention, in which the bar is 
made from copper and the sheath is made from a same metal as the plate. 
This electrode finds one application as a cathode for the production of 
hydrogen and of aqueous sodium hydroxide solutions in a cell for the 
electrolysis of aqueous sodium chloride solutions. 
In the electrode according to the invention, the plate may be solid or 
perforated. It may, for example, be a sheet made from expanded metal.

In these figures, the same reference notations designate identical 
elements. 
The electrical conductor represented in FIG. 1 comprises a bar 1 made from 
copper, in a sheath 2 made from nickel. The copper bar is a rectilinear 
bar, of rectangular cross-section, which has been obtained by rolling. It 
exhibits, on two opposite faces, two grooves 3, 3'. The grooves 3 and 3' 
are filled with nickel beads 4 and 4'. The nickel beads have been formed 
in the grooves by deposition in the molten state by means of a 
conventional arc-welding technique using a nickel or nickel-alloy welding 
rod, such that they are welded to the bar 1. 
The sheath 2 is constituted by two shells 5 and 6 having the shape of 
troughs matching exactly the perimeter of the bar 1. The shells 5 and 6 
have been obtained by deep-drawing two nickel sheets. Their sizes are 
chosen in such a manner that a slot is delimited by their longitudinal 
edges 7 and 8 opposite the bead 4 and such that a second slot is delimited 
between their other longitudinal edges 7' and 8' opposite the bead 4'. 
These two slots are filled respectively with two nickel masses 9 and 9'. 
The latter are obtained by deposition from the molten state by means of a 
conventional arc-welding technique using a nickel or nickel-alloy welding 
rod, such that they are welded to the beads 4, 4' and to the shells 5 and 
6. 
In the conductor represented in FIG. 1, the beads 4 and 4' and the metallic 
masses 9 and 9' produce both a mechanical fixing of the sheath 2 to the 
bar 1 and a low-resistance electrical connection between the bar 1 and the 
sheath 2. 
The electrode represented in FIGS. 2 and 3 comprises a pair of perforated 
vertical nickel plates 10, 10', disposed in a parallel fashion and 
opposite each other, on either side of a horizontal metallic conductor 
designated in its entirety by the reference notation 11. Two corrugated 
nickel sheet elements 12, 12' serve to connect the plates 10 and 10' to 
the conductor 11. 
The conductor 11 conforms to that shown in FIG. 1 and described above. 
The plates 10 and 10' are fixed to the sheet elements 12 and 12' by weld 
points. 
The sheet elements 12 and 12' are also fixed by a welding operation. The 
latter is carried out all along the metallic masses 9 and 9' of the 
electrical conductor, in such a manner as to minimise the electrical 
resistance of the connection between the plates 10, 10' and the bar 1 of 
the electrical conductor 11.