An Improved Manufacture of Electric Accumulators.
Year: 1893

page_text: Date of Application, 22nd Sept., 1893
Complete Specification Left, 20th June, 1894-Accepted, 21st July, 1894
PROVISIONAL SPECIFICATION.
An Improved Manufacture of Electric Accumulators.
We, LUDWIG WILHELM SCHÖFFER, of Villa Witu, Gelnhausen, President of
the "Electricitäts-Gesellschaft Gelnhausen mit Beschränkter Haftung," aud
GEORG ERNST WILHELM SCHÖFFER, of 265 Langgasse, Gelnhausen, Manager
of the said Company, both in the Empire of Germany, do hereby declare the
nature of this invention to be as follows:-
Our invention relates to the manufacture of electric accumulators.
Electrodes for electric accumulators are manufactured by the use of a mixture
of finely pulverized lead and a substance in the form of powder which permits of the
expansion of the lead in its conversion into lead peroxide at the positive electrode
without changing the form of the supports for the electrodes.
Lead divided by mechanical or chemical means, preferably pure lead, has already
been used for the exclusive filling of the cells. Whilst however the manufacture of
the negative electrodes by the introduction of finely pulverized lead into the
supports designed for this purpose does not give rise to any difficulties, all the
endeavours heretofore made to use finely pulverized lead also as a filling material
for the positive electrodes have been unsuccessful because of the inconvenience that
there the peroxide formed by the action of oxygen occupies a considerably larger
volume than the finely pulverized lead from which it is produced, and that in
consequence of this increase of volume of the active filling material a strong pressure
is exerted upon parts of the supports for the electrodes. By this pressure the
supports for the electrodes are caused to bend and the filling material falls from
them, so that the electrode is destroyed and rendered unserviceable.
When lead
oxides are transformed into peroxides or reduced to metallic lead the change of
volume is inconsiderable and has no destructive effect upon the supports for the
electrodes.
A filling material consisting of a mixture of lead oxide or a lead salt and
substances remaining passive, such as coke, has already been employed for
augmenting the porosity of the reduced or also of the peroxidized lead, and use has
also been made of a mixture of one or more derivatives of lead and graphite for
increasing the conductivity of the lead derivatives in the accumulator.
Differing from these modes of producing electrodes, in which on the one hand the
filling of the positive electrodes with finely pulverized metallic lead is precluded,
and by which on the other hand definite objects are to be realized, such as an
increased porosity of the reduced lead or of the peroxidized lead, or a greater
conductivity of the lead derivatives, our improved mode of manufacture is chiefly
designed for enabling finely pulverized lead to be employed as a filling material for
positive electrodes, by admixing substances possessing certain properties.
In order to achieve this object we mix to the finely pulverized lead a substance
in the form of powder, which is either separated by the action of the acid in the
accumulator as the transmutation of the lead into peroxide progresses; or else is
yielding enough or is so changed by the action of the acid that it permits of the
expansion of the particles of lead in its transformation into lead peroxide,
compensating for the pressure of the expanding particles of lead so that the supports
for the electrode will not be acted upon.
The substance selected should be such that it has no deleterious effect upon the
chemical reactions in the accumulator. In some cases the said substance is so
changed by the acid that, like lute, it increases the cohesion of the mixture.
As an admixture of the first kind we may employ for instance finely pulverized

page_text: zinc, starch or the like, and as an admixture of the second kind for instance
powdered pumice stone, also blast-furnace slag, glass, cork, wood or the like in the
form of powder.
The proportion of the material to be mixed to the finely pulverized lead may be
greatly varied. It depends on the material selected and on whether the electrode
is designed for a rapid or a slow discharge. Pulverized zinc for instance may be
admixed up to about 5 per cent. of the weight of the finely pulverized lead, and
powdered pumice stone up to about 50 per cent. and upwards of the volume.
While by means of such admixtures positive electrodes can be manufactured of
finely pulverized metallic lead we gain the great advantage, in case both electrodes
are filled with the same mixture, that the electrodes become very porous, that the
acid easily penetrates into the interior and that a large surface of contact exists
between the active filling material and the acid.
By filling the supports of lead for the electrodes with metallic lead in such a
mixture, a much more intimate contact takes place between the support through
which the current enters and the active material than is the case with accumulators
having supports for the electrodes which are filled with lead oxides or with lead
salts.
Furthermore the time of formation and the work, as compared with accumulators
in which the filling material of both electrodes consists of lead oxides or of lead
salts, are considerably diminished, being reduced to about one-fifth. The capacity
of accumulators with filling material produced as herein before described is much
higher proportionally to the weight of the electrodes than in the case of
accumulators which do not possess such a mixture. Accordingly if the capacities
are equal our improved accumulator is much lighter and can also be manufactured
at a lower price than those in which lead oxides are used as a filling material.
Dated this 22nd day of September 1893.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.
66
COMPLETE SPECIFICATION.
An Improved Manufacture of Electric Accumulators.
We, LUDWIG WILHELM SCHOFFER, of Villa Witu, Gelnhausen, President of
the Electricitäts-Gesellschaft Gelnhausen mit Beschränkter Haftung," and
GEORG ERNST WILHELM SCHÖFFER of 265 Langgasse, Geluhausen, Manager
of the said Company, both in the Empire of Germany, 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:-
Our invention relates to the manufacture of electric accumulators.
Electrodes for electric accumulators are manufactured by the use of a mixture of
finely pulverized lead, and an electrically indifferent substance in the form of
powder which permits of the expansion of the lead in its conversion into lead
peroxide at the positive electrode without changing the form of the supports for the
electrodes.
Lead divided by mechanical or chemical means, preferably pure lead, has already
been used for the exclusive filling of the cells. Whilst however the manufacture of
the negative electrodes by the introduction of finely pulverized lead into the
supports designed for this purpose does not give rise to any difficulties, all the
endeavours heretofore made to use finely pulverized lead also as a filling material
for the positive electrodes have been unsuccessful because of the inconvenience that
in this case the peroxide formed by the action of oxygen occupies a considerably
larger volume than the finely pulverized lead from which it is produced, and that
in consequence of this increase of volume of the active filling material a strong
pressure is exerted upon parts of the supports for the electrodes. By this pressure

page_text: the supports for the clectrodes are caused to bend and the filling material falls from
them, so that the electrode is destroyed and rendered unserviceable. When lead
oxides are transformed into peroxides or reduced to metallic lead the change of
volume is inconsiderable and has no destructive effect upon the supports for the
electrodes.
A filling material consisting of a mixture of lead oxide or a lead salt and
substances remaining passive, such as coke, have already been employed for
augmenting the porosity of the reduced or also of the peroxidized lead, and use has
also been made of a mixture of one or more derivatives of lead and graphite for
increasing the conductivity of the lead derivatives in the accumulator.
Differing from these modes of producing electrodes, in which on the one hand the
filling of the positive electrodes with finely pulverized metallic lead is precluded,
and by which on the other hand definite objects are to be realized, such as an
increased porosity of the reduced lead or of the peroxidized lead, or a greater
conductivity of the lead derivatives, our improved mode of manufacture is chiefly
designed for enabling finely pulverized lead to be employed as a filling material for
positive electrodes, by admixing substances possessing certain properties.
In order to achieve this object we mix to the finely pulverized lead a substance
in the form of powder, which is either separated by the action of the acid in the
accumulator as the transmutation of the lead into peroxide progresses, or else is
yielding enough or is so changed by the action of the acid that it permits of the
expansion of the particles of lead in its transformation into lead peroxide, con-
pensating for the pressure of the expanding particles of lead so that the supports
for the electrode will not be acted upon.
The substance selected should be such that it is electrically indifferent and has
no deleterious effect upon the chemical reactions in the accumulator.
In some
cases the said substance is so changed by the acid that, like lute, it increases the
cohesion of the mixture.
As an admixture of the first kind we may employ for instance finely pulverized
ziuc, starch or the like, and as an admixture of the second kind for instance
powdered pumice stone, also blast-furnace slag, glass, cork, wood or the like in the
form of powder.
The proportion of the material to be mixed to the finely pulverized lead may be
greatly varied. It depends on the material selected and on whether the electrode is
designed for a rapid or a slow discharge.
Pulverized zinc for instance may be admixed up to about 5 per cent. of the weight
of the finely pulverized lead, and powdered pumice stone up to about 50 per cent, and
upwards of the volume.
We will hereinafter describe how for example the manufacture of a filling
material from lead dust and pumice-stone powder and the introduction of the same
into such electric accumulators take place.
In the first place the lead dust and the electrically indifferent pumice stone
powder to be added are weighed in such quantities that the desired proportion will
be obtained.
The two pulverulent substances are then uniformly mixed in a mixing drum.
Here the very fine lead dust penetrates into the pores of the indifferent substance
(pumice stone), whereby subsequent firm cohesion of the filling material is
considerably increased.
The substanees thus mixed are then removed from the mixing drum, moistened
with water and carefully kneaded. In this manner is produced a plastic material
which is similar to moulding sand and can be introduced in the known manner into
supports suitable therefor.
The introduction of the material must take place immediately after the
moistening, because the material cannot be worked subsequently, thus behaving
similarly to gypsum which must also be used directly after the moistening.
When the filling material is introduced the electrodes become moderately but

page_text: still perceptibly heated, the material becomes hard, stony and adheres firmly to the
electrode plates.
After this the plates are put together in the customary manner in vessels for the
forming and subjected to the action of the electric current. Here the finely
divided lead at the positive electrode is converted into peroxide of lead, which
latter occupies a greater volume than the metallic lead and consequently tends to
expaud.
Owing to the fact that the electrically indifferent substance admixed to the
filling material yields, or becomes yielding by the action of the acid, it takes up the
pressure produced by the increase of volume, that is to say it compensates the same
and thus protects the support of the electrodes from injurious deformations.
Inasmuch as the soft peroxide of lead formed is partly forced into the pores of the
admixed porous substance the durability of the filling material is increased.
While by means of such admixtures positive electrodes can be manufactured of
finely pulverized metallic lead, we gain the great advantage, in case both electrodes
are filled with the same mixture, that the electrodes become very porous, that the
acid easily penetrates into the interior and that a large surface of contact exists
between the active filling material and the acid.
By filling the supports of lead for the electrodes with metallic lead in such a
mixture, a much more intimate contact takes place between the support through
which the current enters and the active material than is the case with accumulators
having supports for the electrodes which are filled with lead oxides or with lead
salts.
Furthermore the time of formation and the work, as compared with accumulators
in which the filling material of both electrodes consists of lead oxides or of lead
salts, are considerably diminished, being reduced to about one-fifth. The capacity
of accumulators with filling material produced as herein before described is much
higher proportionately to the weight of the electrodes than in the case of
accumulators which do not possess such a mixture. Accordingly if the capacities
are equal our improved accumulator is much lighter, and can also be manufactured
at a lower price than those in which lead oxides are used as a filling material.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is
The manufacture of electric accumulators in which the active covering material
of the positive electrode,consists of a mixture of metallic lead finely pulverized
with an electrically indifferent substance in the form of powder, which is either
(1) separated by the acid in proportion as the conversion of the lead into peroxide
progresses and thus gives room for the increase of volume, such as zinc dust, starch
and the like, or (2) is or becomes sufficiently yielding to permit of the expansion of
the particles of lead in their conversion into peroxide of lead and to receive the
pressure produced, such as pumice stone, blast furnace slag, glass, cork, wood
and the like in the form of powder.
Dated this 19th day of June 1801
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.