Improvements in and relating to Electric Accumulators.
Year: 1896

page_text: Date of Application, 23rd Nov., 1896-Accepted, 28th Aug., 1897
Improvements in and relating to Electric Accumulators.
I, IPPOLITO CELESTRE, of Syracuse in the Kingdom of Italy, Doctor, 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 improvement made in the construction of electrodes for accumulators which
forms the subject of my application for Letters l'atent has for its object to remedy
the various inconveniences which occur with practically all the types of accumu-
lators hitherto constructed, the principal ones being the small specific capacity
and the rapid deterioration of the plates.
This object is attained by means of the preparation of the active material which
whilst possessing the requisite porosity in order to render it capable of effective action
even for rapid discharge, will nevertheless present such a degree of hardness and
tenacity that it may be formed into plates without the aid of any metallic frame.
The active substance is prepared exclusively with oxides and salts of lead, and
the requisite cohesion is imparted thereto by a simple process of sulphating,
discarding entirely the use of foreign substances whether organic or mineral.
The process is as follows:-
The oxides of lead, either alone or mixed with electrolytic lead are treated with
solution of sulphuric acid, the mass is then worked into a paste with carbonate
or sulphate of lead the quantity of the latter ingredient varying according to the
degree of porosity which the mass is desired to possess, if when the cell is finished
at is required to have a high rate of discharge the quantity of lead carbonate or
sulphate will be greater than if a small rate of discharge is required. The paste
is then submitted to mechanical pressure while immersed in dilute sulphuric acid
either after having filled with it the temporary frames of suitable dimensions to
give it the requisite shape and thickness which the plates are desired to possess,
or after having filled the frames of the electrodes therewith, the construction and
the use of which will be hereafter explained.
I will now give by way of example the proportions of oxide and carbonate best
adapted for a plate seven millimetres in thickness designed for a mean discharge
of 1.2 amperes for 12 hours. Positive plate, Minium treated with a solution of
sulphuric acid 450 grammes.
When the reaction is finished 50 grammes of
powdered lead carbonate is added. The mass is then mixed with water and pressed
into the frame. Negative plate. Minium treated as above 200 grammes.
Powdered litharge 200 grammes. Powdered lead carbonate 100 grammes.
During the subsequent treatment the carbonate is transformed first into sulphate
and then into lead di-oxide or metallic lead.
In the negative plate the sulphate can be substituted for the carbonate.
If the plates are required to discharge at the mean rate of 3 amperes for 3 hours
then the quantity of carbonate can be increased to half that of the oxides in the
positives plates and to one-third that of the oxides in the negative plates.
The proportion of carbonate therefore can be varied within wide limits according
to the rate of discharge required.
At the end of a certain time variable according to the thickness of the paste

page_text: in consequence of the process of sulphation above named the paste acquires a
very considerable hardness and one can remove it from the temporary frames if
use has been made thereof in order to adapt it to, the permanent holders without
danger of breaking. After this, the plates thus constructed are submitted to the
action of the electric current in-the same manner as the ordinary charging of
accumulators. In consequence of this action the oxides of lead of the positive
plates are transformed into peroxide, whilst those of the negative plates are
reduced to metallic lead. At the same time even the sulphate of lead added to the
oxides or resulting from the decomposition of, the carbonate in presence of the
sulphuric acid of the bath is transformed into peroxide in the positive plates and
into metallic lead in the negative plates, but by reason of reduction in volume in
the one and the other case it confers upon the plates a certain degree of porosity
which is proportionally greater as the quantity of sulphate or carbonate used has
been increased. In this manner the porosity of the plates may be regulated
according to the use which is to be made of them; whilst the positive plates as
well as the negative, as may easily be seen from the description of the process
which I have given, are formed of a substance essentially homogeneous and of
extreme purity, in consequence of the complete absence of any foreign substance,
to great advantage from the point of view of their electrical conductivity. In
these conditions the electrodes show moreover such a hardness and tenacity that
it is possible to do away with the use of metallic frames unless these be specially
required for some other purpose, as for instance to conduct the current. Moreover
it is in order to obtain a more completo conductivity that the electrodes are
composed of two or more small sheets united together by the frame which is divided
for this purpose into a like number of compartments by means of interior cross
bars. The accompanying drawing represents a frame for a plate formed of six
pieces, but for plates of larger dimensions one may have a larger number of
compartments. It is however necessary to see that the active material of the
positive plates is able to expand by reason of the peroxidation without obstacles,
and without endangering its rigidity or that of the frame. For this purpose the
frames are provided having special curves of dilatation as shown in the drawing.
If care be taken that the active matter does not touch these curves at their interior
then under the action of the internal pressure, these latter expand within the
desired limits, thus increasing the aurfaces in all the compartments, so that the
dilatation of the active material can take place without any hindrance. By
means of these arrangements, every danger of rupture being removed, the frames
may have a thickness as little as desired so as to reduce to the minimum the dead-
weight of the electrodes which will consequently have a specific capacity con-
'siderably superior to that of the plates of any other system. Secondly, the absence
of metallic pieces within the active mass which by reason of their oxidation cause
splitting and the falling down of the active material in almost all types of
accumulators hitherto in use as also the dilatation of the frames which permits
the increase in volume by oxidation, whether of the frames or of the active material
confer on these plates almost permanent durability; and by virtue of the tenacity
which they are possessed of they suffer no injury even by the shocks to which the
accumulator may be subjected. Amongst the other advantages which are derived
from this system of construction, I may point out that the reactions between the
active material and the metallic part have here only a very minor importance by
reason of the very limited extension of the surface of mutual contact. From this
it results that the yield must be very much increased and that the spontaneous
discharge, that is to say on open circuit will only be effected with very great
slowness. In fact the loss of current between the charging and the discharging of
an element thus composed is negligible and it is possible to preserve a plate
charged during several months without its losing a serious amount of the energy
which is accumulated therein. Further, the great cohesion of the active material
and the suppression of all the causes which may injure its consistency render the
element proof against internal contacts which commonly take place by the falling

page_text: down of some fragment of the same and which produce a rapid discharge even when
the circuit is broken. Finally, for the maintaining of the accumulators of this
system, it is only necessary to supply every two or three months a little distilled
water in order to restore the solution to the required volume which is not only a
very easy but also a very economical process.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what I
claim is :-
1. The process of preparing active material for accumulator plates by means
of simply sulphating oxides of lead as hereinbefore set forth and with the complete
exclusion of all foreign substances whether as an adhesive material or as a reacting
material.
2. The use of carbonate or sulphate of lead in the preparation of this material
by means of which there may be obtained the degree of porosity desired.
3. The frames for accumulator plates provided with curves of dilatation as shown
in the accompanying drawing.
D
0011
וו
זג.
1000
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.