Improvements in and connected with the Manufacture of Electrode Plates for Secondary Batteries.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in and connected with the Manufacture of Electrode
Plates for Secondary Batteries.
I, JULIUS EMIL HOFMANN, of Delligsen, near Alfeld on Leine in the Empire
of Germany, Engineer, 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 has for its object electrode plates for secondary batteries, and a
In the
special casting mould therefor, or a special process for their manufacture.
case of electrodes, it is of importance to obtain as reliable a connection as possible of
the active substance with the supports of the same. Whilst the first point of view
has been already pretty well regarded in the newer secondary batteries, electrode
plates have been entirely wanting in which the second point of view has been
sufficiently taken into account.
This invention solves both these problems in a satisfactory manner as, first, the
active substance is thoroughly prevented from falling out of its supports, and,
secondly, the effective surface of contact between the supports and the active
substance is as large as possible.
In order to attain this object, the plates of lead which serve as supports or a
foundation for the active substance, are provided with pocket-like recesses arranged
at an acute angle to the surface of the plate; these recesses may be of a comical,
pyramidal, cylindrical or prismatic shape. In these pocket-like openings the active
substance is firmly packed, so that it may not fall out during the forming and the
later use.
The electrode forming the object of this invention is shown on the accompanying
drawing together with a casting mould suitable for making the same.
Figure 1 is a section of this improved electrode plate.
Figure 2 a plan view of the same.
Figure 3 is a casting mould in which the steel plates shown in Figures 4 and 5
are inserted, placed one upon another in the manner hereinafter described.
In Figure 1, the sectional form for the pocket like recesses is square in shape.
These recesses are formed symmetrically on both sides of the lead plate a, and
are arranged at an acute angle to the plane of the plate in such a way that in the
centre a solid part of the lead plate a still remains. This is indeed not absolutely
necessary but is however preferable as the electrode plate thereby obtains
much greater solidity. The pocket-like recesses are arranged, as shown in Figure 2,
to a very considerable number above and in proximity to one another, so that an
extremely large active surface results therefrom without anything further.
a
Figure 3 shows a casting mould suitable for making the above described electrode
plates. The case C has wedge pieces e standing at an acute angle to the plane of
the centre against which wedge pieces the peculiarly shaped steel plates d are
arranged one on top of another. The steel plates d are made like a comb at their
lower ends. The teeth which are in this case prismatic in shape always admit of a
small interstice between them, in which the vertical partitions, Figure 4, are formed
when casting. The teeth have further on their upper surface the recess shown on
the drawing in which, during the casting, the partitions, which stand at an acute
angle to the plane of the plates, Figures 3 and 5, are formed. In order to maintain
the steel plates d of one side at a suitable distance from those of the other side,
they are fixed in the casing C by means of their edge for in other suitable manner.
In order to allow of the steel plates being easily drawn out of the casing, they are
provided with openings g, by means of which they can be easily taken hold of.
When the steel plates d have been arranged in layers one upon the other in the

page_text: manner shown in Figure 3, the casting may be commenced. When the casting
operation has been finished, one steel plate d after the other, is withdrawn in order
that no deformation of the partitions formed may take place. In this manner it is
possible to make the walls of the cells as thin as may be required, so that the
effective surface of the plate is a maximum one.
After the pocket-like cells have been filled with the active substance, the
effectiveness of the electrode plates may be further considerably increased, by
making depressions in the prismatic bodies h, Figure 6, formed by the active
substance, such depressions being somewhat smaller than the pockets or recesses b;
these depressions have for their object to facilitate as much as possible the access
of the electrolytic fluid to the active substance. The depressions i may be
preferably produced by means of plates shaped like combs which correspond on a
diminished scale to the steel plate d. The depressions may also be filled up with
neutral porous substances.
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 I
claim is-
1. An electrode plate for secondary batteries having pocket like recesses b
inclined at an acute angle to the plane of the plate, and of prismatic, pyramidal,
cylindrical, or conical shape, the space contained within the outer limits of the
plate being thus divided into so great a number of cells, that the partitions
enclosing the separate cells afford on all sides, with the exception of the outer
walls, as large an effective surface as possible for contact with the active
substance.
2 For the manufacture of the electrode plates described in Claim 1, a casting
mould composed of a case C with wedge plates or faces c inclined at an acute angle
to the plane of the plate, against which faces comb-like steel plates & are inserted
one upon the other in such a way that, when casting, the electrode plate herein-
before described is produced, alter which the steel plates d are withdrawn one by
one from the mould in order to avoid any deformation of the partitions.
3. In the electrode plates described in Claim 1, the formation of depressions i
in the active substance, which correspond on a smaller scale to the pocket-like
cells, and allow the electrolytic fluid to have thorough access to the active
substance.
Dated this 23rd day of May 1893.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.