Improvements in the Electro-deposition of Metals, particularly applicable to the Deposition on Wires.
Year: 1896

page_text: Date of Application, 21st Apr., 1896
Complete Specification Left, 13th Jan., 1897-Accepted, 6th Mar., 1897
PROVISIONAL SPECIFICATION.
Improvements in the Electro-deposition of Metals, particularly
applicable to the Deposition on Wires.
I, JOHN CAMBRON GRAHAM, of 2 Garden Court, Temple, London, E.C.,
Barrister-at-Law, do hereby declare the nature of this invention to be as
follows:-
The rate at which a metal such as copper can he electrically thrown down from
a solution of any given strength depends to a very great extent upon the rate at
which the solution or electrolyte can be made to circulate over the face of the
cathode.
My invention relates to the deposition of metals in long lengths such as wires by
causing a rapid circulation of the electrolyte to take place along the face of
the wire.
I take a tube or trough of any convenient length through which I stretch a small
wire hereinafter called the matrix which acts as the cathode. This tube must
either itself act as the anode, or it may have pieces of metal inside of it which act
as anodes.
Into one end of this tube I force the electrolyte or solution by any convenient
means; allowing it to escape freely out of the tube at the other end. This may be
done by allowing the electrolyte to flow from an elevated reservoir into one end of
the tube; and I have lound that a fall of a couple of feet from the level of the
electrolyte in the reservoir to the level of the tube is sufficient to produce a
circulation with which very dense currents may be used. The electrolyte is
allowed to flow freely out at the other end of the tube and may he returned to the
reservoir by means of a centrifugal pump or by other mechanical means.
The wire or matrix is stretched between the two ends of the tube and where
great lengths of the matrix are used, it should be supported at intervals throughout
the length of the tube so as to prevent it sugging so as to come too near to the
anode. Care must be taken either that the circulation be not interfered with near
the points of support or if this interference cannot be avoided the current
density must be reduced at these points otherwise a defective deposit will be
produced.
The quantity of current should be gradually increased as the area of the matrix
increases. If the matrix is in the form of a wire kept gradually moving through
the tube at such a rate that by the time it reaches the end of the tube it has a
deposit on it of the desired thickness, the anodes may if desired be divided in
sections as measured along the tube, so that the quantity of current passing in any
section may be regulated. The rate of travel will depend upon the size of the
matrix the thickness of the desired deposit. the length of the trough or tube, and
the current density. With a saturated solution of sulphate of copper! have found
that a current density of 150 amperes to the square foot of matrix surface may well
be used, and from this the rate of travel may be easily calculated. With weaker
solutions than saturated ones the current density must be less; but in all cases the
current density is easily ascertained by experiment.
It is obvious that many more wires than one acting as matrices may be passed
simultaneously through the same tube, and if arranged at equal distances froin the
centre the anode may take the form of a rod passing down the centre.
It is desirable that the electrolyte as it flows along the tube should be thrown
into swirls and eddies as much as possible so as to prevent any stream of partially

page_text: exhausted electrolyte from continuing to flow for any considerable distance along
the face of the matrix; and this may be readily effected by placing small ribs at
short distances from each other in the inside of the tube so as to destroy the
regularity of the flow, or in any other convenient manner, the object being to
destroy the parallelism of the flow.
$11000
Improvements in the Electro-deposition of Metals, particularly
applicable to the Deposition on Wires.
I, JOHN CAMERON GRAHAM, of 2 Garden Court, Temple, London, E.C.
Barrister-at-Law, do hereby declare the nature of this invention and in what
manner the same is to be performed, to he particularly described and ascertained
in and by the following statement :-
The rate at which a metal such as copper can be thrown down from a solution of
any given strength depends to a very great extent upon the rate at which the
solution or electrolyte can be made to circulate over the face of the cathode.
My invention relates to the deposition of metals in long lengths such as wires,
strips, sheets or cylinders by causing a rapid circulation of the electrolyte to take
place over the whole face of the cathode: when forming a wire I take a tube or
trough of any convenient length through which I stretch a small wire hereinafter
called the matrix which acts as the cathode. This tube must either itself act as
the anode, or it may have pieces of metal inside of it which act as anodes.
Into one end of this tube I force the electrolyte by any convenient means
allowing it to escape freely out of the tube at the other end. This may be
effected either by allowing the electrolyte to flow from an elevated reservoir into
one end of the tube or by means of a pump; and I have found that a fall of a
couple of feet from the level of the electrolyte in the reservoir to the level of the
tube is sufficient to produce a circulation with which very dense currents may be
used. If the electrolyte is allowed to flow freely out at the other end of the tube
it may be returned to the reservoir by means of a centrifugal pump or by other
means.
The wire matrix is stretched between the two ends of the tube and where great
lengths of the matrix are used it should be supported at intervals throughout the
length of the tube so as to prevent it sagging too much. Care must be taken
either that the circulation be not interfered with near the points of support, or if
this interference cannot be avoided the current density must be reduced at these
points, which can be managed by having no anode near or by shielding, otherwise a
defective deposit will be produced.
The quantity of curront should be gradually increased as the superficial area of
the wire matrix increases.
The matrix may be kept gradually moving through the tube at such a rate that
by the time it reaches the end of the tube it has a deposit on it of the desired
thickness and the anode may if desired be divided into sections as measured along
the tube so that the quantity of current passing in any section may if necessary he
regulated positively. The rate of travel will depend upon the size of the matrix,
the thickness of the desired deposit the length of the trough or tube, and the
current density. With a saturated solution of sulphate of copper I have found
that a current density of 150 amperes to the square foot of matrix surface may be
used, and from this the rate of travel may easily be calculated. With weaker
solutions than saturated ones the current density must be less; but in all cases the
current density is easily ascertained by experiment. But with such dense currents

page_text: as 150 amperes to the square foot there is a great tendency to form nodular
growths on the surface of a wire cathode, and if the intention is to draw or roll
the deposit into wire I have found it best to use a current density of about
60 amperes to the square foot, at which rate the growth of nodules is very
Blight
It is obvious that many more wires than one, acting as matrices may be passed
simultaneously through the same tube or its equivalent.
It will be observed that in the apparatus above described the electrolyte is
confined to the space between the anode and the cathode and through this space it
is caused to circulate uniformly and with great rapidity. By this means the entire
surfaces of both the anode and the cathode are very effectually washed. The rapid
circulation over the catbode surface is always a matter of great importance when
using dense currents as the impoverishment of the electrolyte on that surface due
to the rapid deposition of the metal in solution is thereby prevented. If the
cathode surface be not rapidly washed, the deposit when using dense currents
quickly becomes discoloured and spoiled. And the washing of the anodo surface is
of great importance when soluble anodes and dense currents are used, inasmuch as
the resistance to the passage of the current rises very rapidly when euch anodes
are used unless they are well washed probably in consequence of the formation of a
soluble salt on the surface which can only be dissolved rapidly by washing the
anode surfaces. With insoluble anodes such as lead or carbon this washing of the
anodes is not so necessary.
And further it will be observed that according to this process it is not necessary
to burnish the deposit or to use rotating cathodes, and that every part of the
surface of the cathode receives simultaneously a uniform deposit.
The principle of this invention is equally applicable to the deposition of metals
in the form of tubes, cylinders, sheets and strips and in the drawings appended
hereto suitable apparatus is shown diagrammatically for the deposition of metals in
those forms as well as in the form of wires.
Where the object is to deposit métal from such impure solutions as those
obtained by lixiviating ores the anodes may be either of lead or carbon or other
insoluble substauce or muy even be of a soluble nature as for example of iron for
I have found that the iron which goes into solution from the iron anode as the
copper is deposited has very little tendency to be itself deposited on the cathode
provided that the rapid circulation of the electrolyte over the cathode surface be
maintained.
.
Referring to the two accompanying sheets of drawings which illustrate the
methods of putting my invention into practice :-
Figures 1, 2, 3 and 4 relate to the manufacture of wires.
Figure 1 is a general but diagrammatic side view of the apparatus.
Figure 2 is a section through the depositing vat at the line y z.
Figures 3 and 4 are respectively end and side views of the apparatus for winding
off the wires after they have been thickoned in tho depositing vat.
Figures 5 and 6 relate to the manufacture of tubes and are respectively a plau
and a longitudinal section of an apparatus for depositing a bent tube which is
equally applicable to straight tubes or cylindors.
Figure 7 is a section through a suitable apparatus for the production of strips or
sheets.
Referring first to Figure 1, A is the depositing vat, B is a centrifugal pump,
C is the vat containing the electrolyte, D are bobbins of thin wire from which the
wires are passed into the depositing vat, these wires act as cathodes; E are rollers
which draw the wires through the vat and regulate the rate at which they are so
drawn. F are the bobbins on which they are wound. G and I are chambers
containing alkali and acid for cleaning the wires if necessary, and K is a chamber
represented diagrammatically for annealing the wires if desired.
Referring now to Figure 2 which is a cross section on the line y z through the
depositing vat, the wires are shown by dots, L are planks or frames of wood on

page_text: which the anodes M are placed, thus leaving the closed spaces N through which
the electrolyte is forced with great rapidity. By such an arrangement as this the
wires are deposited with an almost true circular section, and not in an oval form as
might have been expected.
Figures 3 and 4 show convenient arrangements of and details for working the
bobbins F on which the thickened wires are wound. O is a pivoted lever carrying
a pawl P, and Q is a very slowly revolving shaft carrying a number of cains R
which lift the lever O, and the weight. S thus pulls the bobbin round as the wire is
delivered by the rollers E. T is a slowly reciprocating shaft carrying eyes W
which are attached to it by small brackets V which thus guide the wires on to the
bobbius as they are wound on.
Or if preferred the wires may be thickened up to three quarters or an inch in
thickness, and cut off in straight lengths when a sufficient length has emerged from
the depositing bath. Any roughness on these pieces may be cut off with a revolving
cutter or in other convenient manner, after annealing and then they may be
drawn down to wires.
Figures 5 and 6 are respectively a plan and a section of a tube making
apparatus.
Here a bent tube is shown for the purpose of illustrating the
application of this invention to a form of deposit not hitherto easily made. This
form of apparatus is equally applicable to straight tubes or cylinders.
a is a woodon mandril supported at each end on blocks b; c is a conducting
surface formed on the mandril to act as the cathode which ultimately becomes the
deposited tube; d is a lead or copper tube to act as the anode, which stops short of
the ends of the cathode so as to prevent growths forming on the edges. The two
ends of d are held in wooden boxes e and the electrolyte is forced in at and
discharged at g as shown by the arrows.
I find it convenient to make the anode pipo d and the wooden boxes e in halves
so that on removing the upper half from time to time the deposit can be examined
and if necessary scraped.
Figure 7 shows in cross section a convenient arrangement for depositing in the
form of strips or sheets; are the anodes; i the cathodes which form the sheets or
strips; the spaces through which the electrolyte flows rapidly, and I are distance
pieces. The pieces m are of wood and they form a series of chambers to contain
the plates. The strips or sheets can if desired be slowly drawn through the
depositing tank as in the case of wires.
1 would have it distinctly understood that all the drawings in this specification
are diagrammatic but they supply a sufficient guide to enable any person
conversant with the electro-deposition of metals to put my invention into
practice.
Having now particularly described and ascertained tho nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
. claim is―
.
1. The method of depositing metals electrically by causing the electrolyte to
flow rapidly and uniformly through tubes or troughs over the whole surface of the
cathode and anode substantially as described.
2. The olectrical deposition of metals in the form of wires, strips, sheets,
tubes or cylinders upon a matrix or conductor over which the electrolyte is caused
to flow rapidly substantially as described with reference to the accompanying
drawings.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.