An Improvement in Dry Voltaic Cells, and in Conducting Connections for the Carbons of these and other Electric Cells.
Year: 1893

page_text: COMPLETE SPECIFICATION.
An Improvement in Dry Voltaic Cells, and in Conducting
Connections for the Carbons of these and other Electric
Cells.
We, SIEMENS BROTHERS & Co. LIMITED and EUGEN FERDINAND
AUGUST OBACH, all of No. 12 Queen Annes Gate, Westminster, Electrical
Engineers, 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 simple and efficient construction of dry voltaic cell,
and to the formation of a sound conducting connection to the carbon of this cell
or the carbon or other non metallic electrode of other cells.
Fig. 1 of the accompanying drawings is a vertical section of a cell according to
this invention.
Fig. 2 is a sectional plan of the upper end of the carbon shewing one mode of
connecting it to the conductor.
Fig. 3 is a vertical section of the upper part of the carbon shewing a
modification.
A zinc cylinder A is cemented to an insulating base B which may be of wood
ceramic or like material, but preferably is a compound of asphalt about 70 to
80 per cent., ground paper pulp about 10 to 15 per cent. and resin about 10 to
15 per cent. This composition when hot, being in a plastic condition, is readily
moulded to the required shape, becoming quite hard when it cools. C is a central
rod of carbou which is surrounded by a depolarising mixture D consisting of
about 50 or 60 per cent. manganese peroxide and about 40 or 50 per cent. plumbago.
This is made up with about 1 per cent. of gum tragacanth to the condition of a thick
paste which is squeezed out of an annular die, in the form of a hollow cylindrical
column. A suitable length cut from this column, preferably wrapped in porous
paper or fabric is placed in the cell being centred within the upwardly projecting
ring 6 of the base B, the carbon C being previously placed within it. The annular
space between the depolariser and the zinc is filled in with an exciting mixture E
consisting of about 80 to 90 per cent. of plaster of paris and 10 to 20 per cent. flour
or other vegetable meal made into a thin paste with solution of ammonium chloride.
An annulus of paper F is placed over D and E after the whole has been pressed
down to ensure good contact of the depolarising and exciting compounds to each
other and to the carbon and zinc respectively. Over the whole is a layer G of
rasped or ground cork or other granulated material the granules of which do not
absorb moisture. This layer is covered by another paper annulus H and a
bituminous sealing compound K, through which is fixed a small glass tube L com-
municating with the space containing the cork to allow escape of gases. In some
cases we introduce above the middle of the layer of cork a layer of liquid plaster of
paris which is allowed to set in that position and which allows gases to pass through
it, but being separated from the moist contents of the cell does not permit moisture
from these to pass.
The one terminal M is a strip or wire of copper soldered to the zinc, the other
terminal is a screw threaded metal pin P with a collar, nut Q and a clamping nut R.
This is fixed in the carbon C in the following manner; a round hole is formed in
the carbon, larger than the pin P and by means of a V shaped chisel or gauge, a
groove is cut down each side of the hole, the chisel being somewhat inclined so as
to deepen the grooves at the bottom. The pin P being held central, a fused alloy,
consisting of about 2 parts bismuth to 2 parts lead and 1 part tin, is poured into the
hole around the pin. This alloy expands a little in solidifying, and thus fixes the:

page_text: pin very steadily in the hole and makes sound conducting contact with the pin and
the carbon. The lower part of the pin P is tinned and the nut Q is also preferably
tinned on its underside so that, on being screwed down, it can be soldered to the
alloy. The grooves formed in the carbon serve to prevent the alloy from turning
and, being undercut, they also prevent it from being withdrawn from the carbon.
According to the modification shewn in Fig. 3, the hole in the carbon is screw
threaded instead of having the undercut grooves shewn in Figs. 1 and 2.
cases instead of using a screw threaded pin as described we employ a tinned wire
which is placed in the alloy when in a liquid condition and is fixed therein by the
cooling or setting of the same. The use of such a wire would facilitate the
connecting up of two or more cells to form a battery.
In some
Obviously the mode above described of forming a sound conducting contact_to
the carbon may be applied generally to carbons or other non-metallic electrodes
employed in voltaic and other electric cells.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. A dry voltaic cell consisting of a zinc cylinder fixed on an insulating base and
containing a central carbon surrounded by concentric depolarising and exciting
layers covered by granulated cork or equivalent material for preventing escape of
moisture and a bituminous seal, the depolarising and exciting layers. being
compounded and the whole constructed substantially as described.
2. For making conducting connections to carbons, the combination of a screw
threaded metal pin and its nuts or a wire with an alloy that expands in solidifying
in a hole formed in the carbon with undercut grooves or screw thread, substantially
as described.
Dated this 28th day of March 1893.
ABEL & IMRAY, ·
Agents for the Applicants.