Improvements in the Manufacture of Electrodes for Secondary Batteries.
Year: 1898

page_text: Date of Application, 8th July, 1898-Accepted, 17th Sept., 1898
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Electrodes for Secondary
Batteries.
I, HERBERT JOHN HADDAN, of the Firm of Herbert Haddan & Co., of 18,
Buckingham Street, Strand, London, W.C., Civil Engineer, do hereby declare
the nature of this invention a communication to me from abroad by Carl Francke,
of Dessauerstrasse, 6, Berlin, S.W., in the Empire of Germany, Director, and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement: -
When producing pure lead plates intended to serve as electrodes for electric
accumulators or secondary batteries formed according to the Plante process, one
must give attention firstly to obtaining the largest lead surface in proportion to
the total weight and the normal surface of the plate. Further when producing
such electrode plates one must take care that with the oxidation of the lead
effected when forming the plates, and the extension of their volume thereby,
the plates undergo no injurious bending, whereby the danger of self discharge
and of short circuiting may happen, whilst on the other hand the interior con-
ductibility of the plates should be as large as possible for the purpose of obtain-
ing quick charging.
The present invention relates to a method of manufacture which allows of the
production of electrode plates, corresponding completely with the above require-
ments. According to this method a flat grating a of soft, tough lead or of an
appropriate lead composition is made by means of casting and which may have
for instance the form shown in Fig. 1. The single grating bars of the form of
arrangement shown may for instance be 1 mm. thick and 10 mm. high. Although
it is recommended to choose as ground form of the cells of such a grating the
equilateral triangle, other polygons including the circle etc. can be used. On
the one side of the described grating a there is cast a lead band which serves
for current admission.
After having made the grating a the same is laid between guiding bars and
pressed together mechanically in such a manner towards the lead band that
the intervals formed by the cells disappear nearly and one obtains a plate shaped
body of the form shown in Fig. 2. In order to prevent the tearing of single lead
stripes when pressing large plates together, a slide c provided with three cornered
roses d is used, which is drawn in a row of cells of the grating to be pressed
together, as shown in Fig. 1. When forming the plate the same expands in
consequence of the volume increase of 'the lead and this in the direction in which
the plate is pressed together. Bendings which might hereby be caused, are
easily removed after formation of the plate. A further distorting of the elec-
trode plate on later charging and discharging does not take place, because the
distension and contraction hereby effected, which would have produced lateral
bendings, in consequence of the intervals required being made in a sufficient
manner at the time of formation an expansion of the plate can take place with-
out disadvantage in the original pressure direction.

page_text: The characteristic difference of the electrode plates made according to this
new mode of manufacture is they have no fixed lead core and are pressed together
after the casting to an essentially smaller plate surface, whilst in the old system
the existing core cannot follow the expansions and contractions of the ribs &c.
thereon, so that naturally, especially in strong charges, distorting of such core
plates must happen.
By avoiding a core in the new electrode plates the weight of the plate is
further diminished and the efficacious surface is proportionally increased, whilst
simultaneously the inner conductibility of the plate is preserved and the com-
pendious form required for practical use is maintained.
Having now particularly described and ascertained the nature of this in-
vention and in what manner the same is to be performed I declare that what I
claim is;-
1. The improved method of manufacturing electrode plates, whereby a flat
grating made of lead or a suitable lead alloy without a core is pressed together
mechanically in such a manner, that the bars forming the grating lie tightly
on one another leaving small intervals and thus a plate body expansible in the
direction of pressure is made increasing as much as possible the efficacious sur-
face of the plate by simultaneously diminishing the weight and the size of the
plate and capable of avoiding later bendings of the plate when charging or
discharging.
2. An improved manufacture as under Claim 1 whereby by when pressing
the grating a together a slide c with noses d formed to correspond with the shape
of the cells is slid in a row of cells of the grating for the purpose of avoiding
any tearing away of single grating bars when pressing together.
3. The electrode plates made according to the mode of manufacture specified
under Claims 1 and 2.