An Improved Process for the Manufacture of Accumulator Plates.
Year: 1897

page_text: Date of Application, 24th Apr., 1897-Accepted, 29th May, 1897
COMPLETE SPECIFICATION.
An Improved Process for the Manufacture of Accumulator Plates.
I, WILHELM ALEXANDER BOESE of 154 Kopenickerstrasse, Berlin in the
Empire of Germany, Manufacturer, 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 :-
"
"
This invention relates to a process for the manufacture of accumulator plates of
the kind which are known as "solid plates or "mass plates, the active material
itself forming a solid structure without adhering to a metallic support (lattice
work, grid or the like) which plates only require a simple frame or one divided into
two or more fields for supplying or carrying off the current.
"
"
The processes hitherto known for the manufacture of such mass plates are
all founded on the use of certain binding or adhesive. materials which are addel
to the metallic oxides in order to give coherence to the mass, which binding
substances must be made in such a way as to produce a hardening of the mass
under the action of certain acids with which the raw plates are treated, and yet
secure a certain porosity to the plates without which the electrolyte could not
penetrate.
In contrast to the inventions hitherto known, each of which ascribes special
advantages over all others to the binding material on which it is based, the present
invention differs therefrom in that the kind of binding material plays no part or
only a very subordinate rôle in the making of accumulator plates of active material
and in fact the use of a binding material for the metallic oxide may in certain
circumstances even be dispensed with; and that the main condition for the
production of durable and yet firm and porous plates lies rather in the peculiarity
of the manufacture of the plates, without which, even with the most suitable
binding materials no product capable of durable working can be obtained.
This peculiarity in the manufacture of the plates forms the object of the present
invention.
66
mass
"
In order to attain this object towards which all processes for making
plates are directed, namely the production of a product both hard and porous,
according to the present process the peculiar reactions are utilised which takes
place between red lead and certain organic and inorganic acids, whereby either
peculiar peroxide of lead salts are formed (as for instance by means of acetic acid
or phosphoric acid) or a separation of the red lead molecules into lead superoxide
and an insoluble or scarcely soluble lead peroxide salt (as by means of sulphuric
acid) takes place. An accompaniment of the peculiar reactions of such acids on
red lead, is the expansion of the reaction product and this appearance may be
utilised for making very solid mass plates even without the use of a binding
material for the red lead.
In carrying out this process, carefully dried blocks of red lead, which before the
drying are pressed into a frame, are allowed to undergo reaction within this frame
with one of the above mentioned acids. The process of hardening may be thus
explained, that in consequence of the expansion of the mass, the particles of the
reaction product are mutually wedged together in the frame which limits their
lateral expansion in all directions and the plate thereby receives an extremely
bard constitution. A necessary condition for success is that the reaction between
the red lead and the acid should only take place within the frame which surrounds
the plate, and not previously. Following up this point of view the process can be

page_text: carried out in various manners, for instance by dipping, in the acids in question,
dried cakes of red lead surrounded with a frame before the dipping; or by mixing
pulverised acids (such for instance as oxalic acid) with dried red lead, inserting
the same in a frame and then suitably moistening them; or by rapidly inserting
in the frame red lead freshly mixed with liquid acids, such for instance as sulphuric
acid. In the latter case the separation of the red lead into superoxide and lead
sulphate does not immediately take place. In each of these modes of carrying
out the process, the expansion of the mass will take place in the frame and the
hardening will proceed in the manner herein before described.
"
In the method of carrying out the process hereinbefore described, the use of a
binding material for the red lead which is to be inserted in the frame is not
mentioned because it is unnecessary; the use of suitable binding materials known
as such is not however excluded. In the choice of such binding materials attention
will have to be paid, preferably to their chemical behaviour in view of the acids
employed. If for instance the operation be carried out with concentrated acetic
acid, such materials as dissolve in acetic acid but are not chemically altered by
the same, such as asphalt, catechin and the like are to be recommended as binding
materials. If on the other hand the operation be carried out with sulphuric acid
a solution of coal tar residues in alcohol, petroleum, ether or benzole as described
in my Patent No. 11532 of 1892 may preferably be taken as the binding material.
In place of the coal tar residues, bodies of the phenol class may be employed, such
for instance as carbolic acid, creosol, naphthol, anthol, pyrogallic acid, pyrocatechin
and tannin as described in my Patent No. 4610) of 1895. These bodies easily
combine with lead oxide (for instance the phenol to form phenol lead oxide) and
the resulting combinations impart to the raw electrode a firm constitution, and are
easily decomposed by the electric current.
If a 66 mass plate (raw electrode)
formed of red lead and a binding material of the last mentioned kind be placed
in dilute sulphuric acid, the mass will harden to a firm and hard plate which is
distinguished by small resistance to the passage of the current, a high electric
capacity and an extraordinary durability in use. The kind of binding material
mentioned causes the sulphuric acid to evenly penetrate the mass without forming
a crust and to become a coherent evenly converted hard "mass" plate. It is thus
possible to carry out the hardening in the simplest form imaginable so that the
plates may be placed in the acid bath in a dry condition and left therein several
days without bringing them during this time again in contact with the air. In
proportion as the acid is consumed it is replaced by the insertion of fresh quantities,
as the even procedure of the chemical process which takes place during the
hardening is also here brought about or effected by the strength of the acids. If
the acid contents sink too low, impervious layers of salts are formed.
If the
immersion of the plates in the bath is interrupted during the process, the change
or conversion of the whole mass is no longer constant and various layers are
formed which are no longer in combination with one another and cause the
formation of swellings or bulgings and an early decomposition or breaking up of
the plates when in use. It is therefore an essential condition for the success of the
process that the plates should remain in the bath for a single and uninterrupted
period.
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 1
claim is
1. A process for the manufacture of accumulator plates, which consists in
causing red lead to be reacted on within a frame by an organic or inorganic acid
which combines with red lead or which decomposes the red lead, forming an
insoluble or hardly soluble lead salt, with or without the use of a binding material,
in order to produce a mutual wedging of the particles of the mass in the frame by
the resultant expansion of the reaction product substantially as herein before set
forth.

page_text: 2. A process for the manufacture of accumulator plates which consists in mixing
red lead with acetic acid and a binding material soluble in the latter, such as
asphalt or catechin, and allowing it to react in a frame divided into one or more
parts substantially as described.
3. A process for the manufacture of accumulator plates, which consists in dry
red lead formed into plates being inserted in sulphuric acid, or an acid having a
similar action and allowing it to stand therein uninterruptedly, the acid consumed
being replaced until the said plates are sufficiently hard, substantially as
described.
Dated this 23rd day of April 1897.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.