Year: 1889

page_text: I, GEORG EDUARD HEYL, Chemist, of No. 8, Salz ufer, in the City of Charlottenburg,
Prussia, German Empire, 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:—
Up to the present time, the electrodes of secondary batteries have, in some cases,
been made of porous plates of more or less finely divided lead. The latter is used in
form of powder, sponge, strips, foils, or dust. All these forms of the lead possess the
disadvantage that the surfaces of the particles approach each other too much by the
pressure required in forming the plates, and oppose a great resistance to the circulation
of the electrolytic liquid. During the action, small particles of lead separate and form
short circuits, which can be avoided only by the use of troublesome envelopes, which
injure the efficiency.
The present invention produces an electrode superior to those hitherto known. The
new electrode, which is of lead-felt, possesses, for the same weight, a much greater
active surface, as the lead-felt, in spite of the heavy pressure used in forming the plates,
is not compressed to a compact mass, but remains much more porous than any of the
lead preparations heretofore used, whereby the electrolyte circulates more freely and
the efficiency is increased. As no lead particles can separate from the lead-felt, short
circuits are not formed and envelopes not required. The manner in which the lead frame
is united with the single plates composing the electrode, secures an undisturbed and
complete transmission of the electric current.
To carry out my invention, I prepare a number of lead-felt cakes or plates, by
hanging up vertically, thin round wires or threads of lead, which have the same weight
for each plate, entangling and combining or felting them by causing several streams
of compressed air to act against them simultaneously in different directions. When
the lead threads are sufficiently felted, they are suddenly dropped to the ground,
forming a spongy heap of loose felt, which is compressed in a suitable mould and by
any suitable compressing apparatus, so as to furnish a coherent cake or plate of lead-
felt, about to a inch thick, 3 to 6 inches wide, and 6 or more inches long. A
number of these plates are then placed flat into a suitable mould, in such manner that

page_text: a space of to inch remains between and around the different plates. After having
moistened the edges of the plates with soldering fluid, melted lead is poured into the
mould, whereby the edges of the felt cakes are soldered to the setting lead. In this
way, all the felt plates are firmly united with each other and with the frame and trellis
work by soldering, securing an absolute electric contact and complete transmission of
the electric current.
As the lead threads of the plates are felted, and moreover compressed, no short ends
or particles can drop down. The round threads, crossing each other in every direction
and completely entangled and felted, cannot be compressed to a compact mass, but
retain the original interstices, holes, canals, etc., though decreased in size by pressure.
By these means an active surface is produced of greater extent than any of the known
electrodes of the same weight are able to present. The effectiveness of the new
electrode is considerably greater than that hitherto attained, as the electrolytic fluid
can freely circulate through the lead-felt, and the security of working is absolute.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, 1 declare that what I
claim is:-
1. For secondary batteries, an electrode, consisting of a number of plates or cakes
of lead felt, of the same or nearly the same weight, and suitably compressed, united
together, and to the lead frame which transmits the electric current, by soldering,
substantially as described and for the purpose explained.
2. In an electrode for secondary batteries, the different plates or cakes constituting
the active mass, consisting of lead felt, in combination with a leaden frame or trellis-
work, soldered to the plates, substantially as described and for the purpose explained.
3. For secondary batteries, the use of lead-felt as the material for the electrode plates
or cakes, substantially as explained and for the purpose set forth.
Dated this 24th day of April 1889.
GEORG EDUARD HEYL.
By Harris & Mills,
23, Southampton Buildings,
Agents.