Note: Descriptions are shown in the official language in which they were submitted.
766
The present invention relates to a batter comprislng
a single flat cell or several cells piled on each other and
being integrally connected along the circumference, said
cells each comprising a zinc anode, an alkaline electrolyte,
a cathode of mercuric oxide, mercury or manganese dioxide
or a mixturè thereof, and a cell casing in the form of a
plastic cup, a terminal plate being located both on the
inner and on the outer side of the bottom of said plastic cup.
German patent specification No. 906,586 to
Schneider, published March 15, 1954, discloses a battery
block of flat cells. The active portions of these flat
cells are located in frames of non-hardenable ! thermoplastic
material which has been made conductive by addition of carbon.
This plate abuts a zinc plate extending from the cell below
with a relatively large bent portion through a correspondingly
shaped recess in the bottom of the frame. By sticking the
zinc plate in each cell to the ~rame by using a solvent, a
relatively good security against leakage of electrolyte
to the conductive thermoplastic plate is obtained. This
known construction does not, however, suffice in solving the
sealing problems present by alkaline batteries of the above
type.
~y alkaline batteries of the above type with cells
piled on each other, it has previously been a problem to
obtain a sufficiently tight assembling of the cells into
an integral unit. This problem has now been solved by
using a particular method of assembling the cups along
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their periphery. By this method the cups are assembled at
a time along the entire periphery by a quick process.
The object of the present invention is to provide an
improved security against electrolyte leakage from an alkaline
battery of the above type, by increasing the resistance to
electrolyte leakage at the terminal passage in the bottom
of each plastic cup.
Usually electrolyte leakage from an alkaline battery
is due to one or more of the following well-known phenomena:
1. Capillary effect in the unevennesses of the
surface, by a bad sealing etc.
2. Electrocapillary effect.
3. Oxygen reduction.
4. H2O reduction.
5. Eïectroosmosis.
6. The Marangoni effect.
It must, however, be regarded as certain that in
addition to the above, terminal amalgamation is of substantial
importance as the zinc electrodes contain mercury dispersing
between zinc and terminal metal. This is of importance for
the negative terminal, by which only the phenomena mentioned
under items 3 to 6 occur, and by which experience shows the
greatest sealing difficulties.
The battery according to the invention comprises at
least two flat cells stacked on each other and integrally
connected along the circumference, the cells each comprising
a zinc anode, an alkaline electrolyte, a cathode of a material
selected from the group consisting of mercuric oxide,
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mercury or manganese dioxide or a mixture thereof, and a
cell casing in the form of a plastic cup having a bo-ttom
comprising elastomeric material, a terminal plate, the
terminal plates being located both on the upper and lower
surfaces of the bottom of the upper cup and abutting a
substantial portion of the surfaces, at least one of the
terminal plates comprising a plurality of projecting knobs,
each knob extending through an aperture located in the
bottom of the upper cup and being relatively small relative
~o the diameter of the bottom, each knob furthermore being
connected to the other terminal plate in such a manner that
the plates squeeze about and under pressure abut the material
in the bottom of the cup so as to form a pressure seal
between the terminal plates and the elastomeric material,
and a sealing ring located in said aperture and surrounding
the knobs, the sealing ring being deformed by the pressure
of the terminal plates.
Such a connection with a great specific pressure
between the terminal metal and the elastomeric material
provides a durable sealing as cold flow is avoided, which
would otherwise cause a decreasing pressure between polymer
and metal. Furthermore a double sealing between metal and
polymer is obtained with an interspace interrupting the
capillary effect, and a long creepage-path between terminal
metal and polymer.
The connection is provided by a simple method and with
a relatively great deformation of material, whereby rather
great tolerances are permitted regarding the aperture in the
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plastic cup and regarding the metal knob and in a sealing
ring located between the metal knob and the edge in one
embodiment of the battery. In this embodiment two separa-te
sealing portions are obtained between the metal and the
rubber with air therebetween. As a result the capillary
effect is interrupted.
As an additional reduction of the risk for electro-
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lyte leakage, the terminal plate not containing the anode
may according to .the invention be of a metal particularly
impeding for the reduction of 2 and H20, and/or which
can be manufactured particularly smooth, but for that
.5 matter may be unstable at contact with the anode.
: According to an alternative embodiment of the battery
according to the invention, the cups are cast of hard,
thermoplastic elastomer, and the aperture in the bottom of
. each cup is defined by an edge shaped with annular project-
ing rim portions. Such a construction renders it possible
to dispense with the sealing ring, whereby a quicker as-
.sembling process is provided.
By using plastic cups of elastomeric materials, cells
having particularly good .temperature properties are ob-
taine.d, as.these materials have very low glass transition
temperatures, and the cups can resist strong mechanical
inrluences in the later battery producing process~
The invention will be described below with reference
.to .the accompanying drawing, in which
.20 Fig. 1 illustrates a connection between two cells and
a passage to the atmosphere in an embodiment of the battery
according to the invention,
Fig. 2 illustrates an alternative embodiment of the
terminal passage between the cells or to the surroundings,
and
Fig. 3 illustrates a dovetailed knob, and
Fig. 4 is a.bottom view of a cell with four knobs.
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Fig. 1 illustrates two plastic cups 1 forming cell
casings interconnected by connecting surfaces 2 in an in-
stant process influencing -the entire periphery at the same
time. Such an instant influence may for instance be pro-
-5 duced by ultrasonic welding, gluing by dipping, hot weld-
ing, high frequency welding or another similar assembling
process.
The lowermost cell in Fig. 1 is completely mounted
with a pressed cathode 3 of mercuric oxide, mercury or
manganese dioxide or mixtures thereof, two separator
diaphragms 4, and an anode 5 comprising powdered zinc in
alkaline electrolyte. A negative terminal plate 6 with
curved edges is located above the cathode 3, and a termi-
nal plate 7 is located under the anode 5 in the bottom of
the cup.
The terminal plates 6 and 7 in plastic cups 1 piled
on each other are interconnected through an aperturelin
the middle of the bottom 8 of the uppermost cup, the first
terminal plate 7 comprising an embossed, projecting knob
9 extending through the aperture in the bottom of the cup,
and furthermore being spot welded to the middle of the
second terminal plate 6. The spot welding is performed in
such a manner that the terminal plates 6 and 7 squeeze
about the material in the bottom 8, whereby a pressure
sealing between the terminal metals and the elastomeric
material in the bottom is established. As a result cold
flow and thereby involved decreasing contact pressure are
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avoided. As the terminal plates squeeze against both sides
of the bottom, a double sealing between metal and plastic
polymer surfaces under a specific sealing pressure is ob-
tained, said sealing pressure being very hiqh across the
relatively small sealing por*i.on. Furthermore, .the termi-
nal plate 6 ma~ optionally consist of a metal particularly
impeding for the reduction of 2 and H20 etc., whereby an
additional securing against leakage`is provided. The bat-
tery~illustrated furthermore provides a long electrolyte
creepage path.
In.the embodiment illustrated in Fig. l,.the knob 9
on the .terminal plate 7 is surrounded by a sealing ring 10
such as for instance a torique of rubber deformed under
influence of pressure when the .terminal plates are being
assembled. In this manner two separate.sealing portions
are provided between metal and rubber with.air ~th.erebe-
tween, which interrupt the capillary effect.
In the embodiment illustrated in Fig. 2 .the plastic
cup is cast of a hard, thermoplastic elastomer, and the
.20 :~edge about the aperture in the.bottom of the cup is pro-
vided with three projecting sealing portions 11 forming
three separate plastic-metal sealing portions with air
therebetween.~ :
It is to be understood that the above terminal pàssage
principle may also be us.ed in the top and the bottom of a
single flat cell.~
The metal-elastomer~sealing provides a double sealing
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as two metals with an interspace therebetween are sealed
by means of the same torique~ Should the first.sealing fail
on account of the capillary effect, the.interspace is
capable of receiving part of the leakage before the second
sealing enters into function. Furthermore, two different
metals are used for the sealing. One metal, against which
a sealing is aimed at, may not stand a location within the
cell, but may stand a location in the atmosphere. There-
fore it is an additional advantage that two different
.lO metals ma~ now be employed.
According to an alternative embodiment. several pole
connections from one cell to the other are provided, e.g.
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: three or four pole connections~ These.pole connections may
. be provided along a circle.concentric with the cup. The
pole connections and the knobs 9 are preferably mutually
located at .the same angular distance. According to a pre-
ferred embodiment, the knobs are dovetailed. However, theknobs need not be equally formed or be provided in the same
: .terminal plate of adjacent terminal plates.
