Improvements in the Manufacture of Positive Lead Electrodes for Electric Accumulators.
Year: 1896

page_text: Date of Application, 18th May, 1896
Complete Specification Left, 12th Feb., 1897-Accepted, 3rd Apr., 1897
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Positive Lead Electrodes for
Electric Accumulators.
I, HENRI OWEN TUDOR, of Rosport, in the Grand Duchy of Luxemburg,
Engineer, do hereby declare the nature of this invention to be as follows:-
The process forming the subject of this invention for the production of positive
lead electrodes for electric accumulators is a modification of the well known
method of Planté for forming a layer of peroxide of lead on the surface of lead
electrodes.
Gladstone and Tribe as far back as the year 1883 found that, when employing
very dilute sulphuric acid (1:1000), lead plates treated according to Plante's
method became more quickly corroded than when employing stronger electrolytes
and that the action in the first few minutes is considerably greater than it is
afterwards. They noticed at the same time the formation of yellowish oxides and
sulphates of lead under the layer of dark coloured peroxide of lead.
According to the present invention I avail myself of the results of the above
named experiments and in the first stage of the manufacture a very porous layer
of suitable thickness is obtained on the lead electrodes by the employment of very
dilute sulphuric acid. In the second stage this layer, which contains a large
amount of sulphate, is reduced to spongy lead by charging the electrodes as negative
electrodes. In the third stage the electrodes so treated are finished and the spongy
lead is converted into the peroxide.
In carrying out my invention great care is required, especially in the first stage.
The metallic lead electrodes, which are preferably formed with as large a surface
as possible, are charged at intervals as positive electrodes in very weak acid of
about to 2° Bé. As soon as the positive electrodes shew that gas is being
formed the periods of rest are replaced by slight discharges until a sufficiently thick
porous layer is obtained.
On an average 15 to 25 days suffice for the production of a sulphate layer of
sufficient strength. This layer is very hard and the direct employment of the
electrodes is excluded by reason of the large amount of lead sulphate present. The
electrode plates are therefore charged in the same weak acid, as negative electrodes,
until the layer is completely reduced, formation of gas sets in and the original
brown plate assumes a grey appearance. The electrodes are then finished by being
employed as positive electrodes in strong acid (15° to 20° Bé.) whereby the layer is
converted into dark peroxide. This process is most advantageously carried out by
charging until gas begins to be formed, then allowing periods of rest, and then
continuing the charging operation until gas again commences to be given off. The
battery is then slowly discharged and then again overcharged. This treatment
can be repeated many times with or without periods of rest. Positive plates made
according to this process possess a very adhesive layer of a constant capacity.
Instead of employing simple metallic lead electrodes I may employ electrodes
the surfaces of which are provided with a thin layer of lead oxide or other
lead salts.
M
1000
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Positive Lead Electrodes for
Electric Accumulators.
I, HENRI OWEN TUDOR, of Rosport, in the Grand Duchy of Luxemburg,
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:--
The process forming the subject of this invention for the production of positive
lead electrodes for electric accumulators is a modification of the well known
method of Planté for forming a layer of peroxide of lead on the surface of lead
electrodes.
Gladstone and Tribe as far back as the year 1883 found that, when employing
very dilute sulphuric acid (1:1000), lead plates treated according to Planté's
method became more quickly corroded than when employing stronger electrolytes
and that the action in the first few minutes is considerably greater than it is
afterwards. They noticed at the same time the formation of yellowish oxides and
sulphates of lead under the layer of dark coloured peroxide of lead.
According to the present invention I avail myself of the results of the above
named experiments and in the first stage of the manufacture a very porous layer
of suitable thickness is obtained on the lead electrodes by the employment of very
dilute sulphuric acid. In the second stage this layer, which contains a large amount
of sulphate, is reduced to spongy lead by charging the electrodes as negative
electrodes. In the third stage the electrodes so treated are finished and the spongy
lead is converted into the peroxide.
In carrying out my invention great care is required, especially in the first stage.
The metallic lead electrodes, which are preferably formed with as large a surface
as possible, are charged at intervals as positive electrodes in very weak acid of
about to 2° Bé. As soon as the positive electrodes shew that gas is being formed
the periods of rest are replaced by slight discharges until a sufficiently thick porous
layer is obtained.
On an average 15 to 25 days suffice for the production of a sulphate layer of
sufficient strength. This layer is very hard and the direct employment of the
electrodes is excluded by reason of the large amount of lead sulphate present.
The electrode plates are therefore changed in the same weak acid, as negative
electrodes, until the layer is completely reduced, formation of gas sets in and the
original brown plate assumes a grey appearance. The electrodes are then finished by
being employed as positive electrodes in strong acid (15° to 20° Bé.) whereby the
layer is converted into dark peroxide. This process is most advantageously
carried out by charging until gas begins to be formed, then allowing periods of
rest, and then continuing the charging operation until gas again commences to be
given off. The battery is then slowly discharged and then again overcharged.
This treatment can be repeated many times with or without periods of rest.
Positive plates made according to this process possess a very adhesive layer of a
constant capacity.
Instead of employing simple metallic lead electrodes I may employ electrodes
the surfaces of which are provided with a thin layer of lead oxide or other
lead salts.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
A process for the manufacture of positive lead electrodes for electric accumulators.

page_text: such process consisting in charging the lead electrodes as positive electrodes for some
time in very weak acid at first with intervals of rest and then with intervals for
discharging for the purpose of forming a layer of lead oxide containing sulphate, in
then reducing this oxide layer by employing the electrodes as negative electrodes
and finally in arranging the electrodes in strong acid as positive electrodes and
repeatedly charging and discharging the same for the purpose of converting the
reduced layer into the peroxide all substantially as hereinbefore described.
Dated the 12th day of February 1897
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.