Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to storage batteries, more
particularly to a lead-acid storage battery and a method
of manufacturing the same.
An object of the present invention is to provide a
storage battery having favorable high rate discharge
characteristics and long life, and a process for manu-
facturing the sa~e.
Another object of the present invention is to provide
a storage battery which can be mass produced and a process
for manufacturing the same.
A further object of the present invention is to
provide a storage battery which is inexpensive and easy
to make, and a process for manufacturing the same.
According to the invention, there is provided a
storage battery formed by arranging between negative and
positive plates an embossed separator having a plurality
of concaves provided on a thin microporous sheet and
channels connecting said concaves with each other and
shallower than the concaves.
The present invention can be more easily understood
- by referring to the following drawings and description.
Fig. 1 is a partly sectioned perspective view of a
storage battery of the present invention;
Fig. 2 is a partial plan view of an embossed separator
forming the storage battery of the present invention;
Fig. 3 is a greatly enlarged partial perspective view
of the embossed separator of Fig. 2;
Fig. 4 is an even more enlarged sectional view of the
embossed separator taken substantially along line A-A' of
Fig. 2;
Fig. 5 is a partial perspective view of a conventional
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embossed separator;
Fig. 6 is a partial vertical sectional view of the
separator of Fig. 5 as arranged in close contact between
negative and positive plates; and
Fig. 7 is a diagrammatical view showing a process used
for manufacturing an embossed separator forming a storage
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battery of the present invention.
In Fig. 1, a storage battery 1 comprises negative
plates 3, embossed separators 4 of a special shape,
positive plates 5 and an electrolyte Inot illustrated)
housed in an electric battery container 2, a lid 6
covering the container.
A feature of the present invention involves the use
of embossed separators of a special shape in the storage
battery. Each embossed separator 4 is formed of a plur-
ality of concave portions 7, channels 8 connecting theconcave portions and shallower in depth as compared
thereto and substantially projecting webs g on one surface
thereof. The separator is in the form of a microporous
sheet 4, having convex portions corresponding to the
concave portions, linear projections corresponding to
-the channels and concaved webs corresponding to the
projecting webs on the other surface. As a whole, this
embossed separator is formed as a concave-convex element
and has an apparent thickness several times as large as
the thin original microporous sheet from which it is
made. The thin microporous sheet is a microporous sheet
containing a synthetic resin or a sheet of a thickness of
less than 0.5mm comprising a nonwoven fabric or the like
made of fine synthetic fibers of a diameter of less than
5 microns. It is preferable that each concave portion be
diamond-shaped and having a side length in the range of 1
to lOmm., or be substantially in the form of a circle, an
ellipse, a square or a rectangle of a size substantially
corresponding to such range. It is preferable that the
distance between the concave portions be in the range of 4
to 20mm. and that the width of the channel be in the range
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of 0.2 to 2mm. If they are outside these ranges, it will
be difficult to form concave and convex portions on the
thin microporous sheet and, even if they can be formed, no
embossed separator of a desired apparent thickness main-
taining a distance between negative and positive plates
will be obtained, the pore diameter of the micropores will
be reduced and made more filmy than is necessary, the
electric resistance will be high and the battery perfor-
mance will not be satisfactory.
The embossed separator ~ is obtained by passing a
microporous sheet under an applied pressure between an
elastic roll and a heated metallic embossing roll having
a pattern of a plurality of projections and linear
projections connecting the projections and lower than
them. The detailed manufacturing process shall be
described later.
The thus made embossed separator is formed to be
concave-convex as a whole so as to have an apparent
thickness. When such embossed separators are used in a
storage battery, the electric resistance is so low that
the battery performance is favorable. Further, this
embossed separator has so many comparatively small con-
cave portions as to render it highly elastic. When
arranged between negative and positive plates, the
separator effectively applies a force of pressure par-
ticularly to the active material of the positive plate and
is very effective in preventing the active material from
shedding off. As a result, it has an advantage of further
improving the life of the battery. Further, when this
embossed separator 4 is arranged in close contact between
the negative plate 3 and positive plate 5, due to concave
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portions 7 and shallower channels 8 provided on the
embossed separator 4, the space between the embossed
separator 4 and the negative plate 3 or positive plate
5 forms a continued passage. This results in an easy
diffusion of the electrolyte, easy removal of gases
generated from the plates during the use of the battery
and smooth electrochemical reaction, thereby improving
the battery perEormance. In the conventional embossed
separator 4', a plurality of concave portions 7' are
merely formed as shown in Figs. 5 and 6. Therefore, when
the embossed separator 4' is arranged in close contact
between a negative plate 3' and positive plate 5', concave
portions 7' become sealed chambers from which gases will
be difficult to escape and therefore remain to prevent the
movement of ions and, as a result, the battery performance
will deteriorate extremely.
Another feature of the present invention is that a
part or all of the micropores of the plurality of concave
portions 7 or channels formed on the embossed separator 4
are reduced or are made filmy. Therefore, the microporous
sheet l-is made of a synthetic resin or a mixture of a
synthetic resin with an inorganic filler. Polyvinyl
chloride, polystyrene and polyvinylidene fluoride are
approriate types of synthetic resins to be used. Many
other resins, the micropores of which can be reduced or
made filmy micropores when heated, can be used. The
reduction or ~ilming of the micropores will be influenced
by the heating temperature of the aforedescribed metaIlic
embossing roll passing the microporous sheet. The higher
the temperature, the more the reduction or filming of the
micropores and the more filmy the sheet. On the other
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hand, the more filmy the concaves or channels, the higher
the elasticity of the embossed separator but the higher
the electric resistance.
The formation of a sheet high in elasticity is of
a microporous sheet which is made of a compound of a
microporous synthetic resin with a nonwoven or woven
fabric of synthetic fibers, in which only the synthetic
resin forming micropores will melt but the synthetic
fibers will not melt and which is optimum to bring about
favorable results in the battery performance and life.
When such embossed separator having a high elasticity is
arranged between negative and positive plates, it will
be very effective in preventing particularly the active
material of the positive plate from shedding off and will
be advantageous in further improving the performance and
life of the battery as a result.
A further feature of the present invention is to
assemble a storage battery by arranging the embossed
separator 4 between the negative plate 3 and positive
plate 5 so that the channels 8 formed on the separator may
be diagonal to the vertical direction of the plates. The
removal of the gases generated during the use of the
battery will therefore be further improved and the battery
performance will further improve.
A still further feature of the present invention
involves contacting the tips 7a of concave portions 7 with
the positive plate and contacting convex portions 9 with
the negative plate. It is the arrangement of the embossed
separator wherein spaces formed between microporous sheet
and the plates allow for easy diffusion of the electro-
ly~te and the removal of the gases, and the direct contact
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of filmy part 7a on the positive plates give strong
oxidation resistance, thereby improving the battery
performance and life.
A still further feature of the present invention
involves a ne~ process for manufacturing storage
batteries. It comprises the step of forming concaves and
convexes by passing a thin microporous sheet between a
flat surface elastic roll and a heated metallic embossing
roll having a pattern of a plurality of projections and
linear projections connecting such projections with each
other and lower than them, the step of then cooling under
no applied tension the microporous sheet which has the
concaves and convexes already formed on it and the step
of assembling a storage battery with the thus obtained
embossed separators. Fig. 7 is a diagrammatical view
showing a process for manufacturing a storage battery
and particularly a process for manufacturing an embossed
separator. For example, a thin microporous sheet ll is
passed, under an applied pressure, between a metallic
embossing roll 12 having the aforedescribed pattern and
heated to a predetermined temperature, and an elastic roll
13 having a flat surface. Therefore, the plurality of the
higher projections connecting said higher projections with
each other on the metallic embossing roll will contact
the microporous sheet under the applied pressure. As a
result, the diameters of the micropores of the sheet, as
at 7, and channels 8 formed on the microporous sheet will
be reduced or made filmy and other webs 9 will retain the
micropores as they are. This is because of the use of flat
elastic roll 13 which may be, for example, a rubber roll.
As a result, favorable embossed separators for storage
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batteries low in electric resistance and high in battery
discharge characteristic will be obtained. Then the
embossed narrow long microporous sheet 11' is passed under
no applied tension between a pair of cooling rolls 14
and 14'. If a tension is applied, concaves and channels
formed on the microporous sheet 11' will be deformed or
will be reduced in apparent thickness. Thus no favorable
result will be brought about in the performance and life
of the battery. The microporous sheet 11" having passed
through the cooling rolls 14 and 14' passes through the
next step when it is cut into a required size for use as
separators 4. A storage battery is assembled by arranging
such embossed separator between negative and positive
plates. Some examples on the aforedescribed embossed
separators are shown in the following.
Example 1:
A thin microporous sheet having a polyester non-woven
fabric of a thickness of 0.2mm. and chlorinated polyvinyl
p r ~A c ~ p G~ I
chloride as the ~nclp~ microporous components and an
average micropore diameter of 0.6 micron was made, was
passed at a speed of lOm./min. under a nipping pressure
of 78kg/cm2. between a metallic embossing roll having a
pattern comprising a plurality of projections of which
the shape of the tip was in the form of a diamond having
a side length of 2mm., the height was 1.8mm. and the
distance between the centers of projection was 5mm. and
linear projections connecting the projections with each
other, having a width of the tip of 0.2mm. and lower than
the projections and heated to a temperature of 130C., and
a flat surface rubber roll made of neoprene (a synthetic
rubber3 of a hardness of 80 flat on the surface. The sheet
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was then passed between a pair of cooling rolls under no
applied tension to obtain an embossed separator of an
apparent thickness of 0.8mm. provided with nonporous filmy
concaves and nonporous filmy channels of a depth of 0.3mm.
and a width of 0.2mm. connecting the concaves with each
other.
This embossed separator was so low in the electric
resistance in dilute sul~uric acid of a specific gravity
of 1.20 as to be of O.OOlOQ/dm2/sheet, was of 130H/sheet
in the resistance to electric oxidation and was twice as
strong as a conventional paper resin bonded separator.
Further, its elasticity was so high that, when a load of
20kg/lOOcm2. was applied for 3 months, the deformation
was 10%. It was superior to a conventional glass fiber
mat.
When a battery was assembled by setting these embossed
separators so that the tips (conve~es on the other
surface~ of the concaves contact the positive plate and
the channels connecting the concaves with each other were
diagonal to the vertical direction and was tested, a
distance between the plates could be held by the plurality
the elastic concaves provided on the embossed separator,
the active material could be prevented from shedding o~f,
the movement of the electrolyte could be easy by the
shallow communicating channels connecting the plurality of
the concaves with each other and the gases generated from
the plates could be moved through the plurality of the
concaves and shal:Low channels of the aforementioned
separators and could be removed out of the electrolyte.
Particularly, at a high rate discharge, high performance
not seen in any conventional separator was shown. There
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were increases of 20~ in the battery capacity and 8~
in the voltage characteristic. The life of the storage
battery of the present invention in which these embossed
separators were used was 50% longer than of a battery
in which ribbed separators were used. Further~ as
the channels of the embossed separator are diagonally
arranged, the gases in clearances between separator and
plates could be removed very well. As compared with a
conventional ribbed separator or separator with glass
fiber mat, the embossed separator applied to the present
invention is made by the mere deformation of a thin
microporous sheet and has no material added, therefore,
its cost reduction of 30% is possible. It is so simple to
handle in assembling a storage battery by enveloping plate
with this paper like flexible embossed separator that lt
is easy to make the storage battery.
Example 2:
A microporous sheet of a polyester nonwoven fabric of
a thickness of 0.2mm. using fibers with diameter of less
than 5.0 micron was made, was passed between a metallic
embossing roll having a pattern of a plurality of projec-
tions of a shape of the tip in the form of a circle of a
diameter of 3mm. connected with each other through linear
projections ha~ing a width of the tip of lmm. and lower
than the projections and heated to 120C., and a rubber
roll, and was then passed between a pair of cooling rolls
under no applied tension. As a result, an embossed
separator of an apparent thickness of 0.7mm. was obtained,
on which a plurality of circular concaves and channels
connecting them with each other were formed. This
embossed separator was so low in the electric resistance
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in dilute sulfuric acid of a specific gravity of 1.20 as
to be of 0.0008Q/cm2./sheet and was of 60H/sheet in the
resistance to electric oxidation. When these embossed
separators were incorporated into a battery in such a
manner the tips of the concaves contacted the positive
plates and the channels were disposed diagonally rela-
tively to the vertical direction and the battery was
tested, the capacity increased by 13% and the voltage
characteristics increased by 10~. Further, there were
the same advantages as in Example 1.
Example 3:
A uniform mixture consisting of 15% by volume high
molecular weight polyethylene, 15% by volume silica as
a filler, 1% by volume carbon black and 69~ by volum~
petroleum oil as a plasticizer was made into a sheet.
The sheet was dipped in a solvent hexane to extract the
petroleum oil to make a thin microporous sheet of a
thickness of 0.3mm. This microporous sheet was passed
between a metallic embossing roll having a pattern with a
plurality of projections of a shape of the tip in the form
of a diamond of a side length of 2mm. and of a distance
between the projections of 5mm. connected with each oth~r
through linear projections having a width of the tip
of 0.2mm. and lower than the projections and heated to
160C., and a rubber roll, and was then passed between a
pair of cooling rolls to obtain an embossed separator
of an apparent thickness of 0.8mm. having a plurality
of diamond-shaped concaves and channels connecting
them with each other~ This embossed separator was of
0.0017Q/dm ./sheet in the electric resistance in dilute
sulfuric acid of a specific gravity of 1.20 and of more
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than 450H/sheet in the resistance to electric oxidation.
Just this embossed separator was rather poor in the
elasticity and was therefore comparatively short in the
life but its life increased to be 20% longer than of the
conventional ribbed separator. Further, there were the
same advantages as in Example 1.
Thus the storage battery of the present invention
and the process for manufacturing the same have various
advantages that the performance and life of the storage
battery are remarkably improved and that the battery is
cheap, is easy to make and is adapted to be mass-produced.
It is needless to say that various modifications of
the product and alterations of the manufacturing process
are possible in the range not deviating from the spirit of
the present invention. For example, the material to be
used for the thin microporous sheet is not limited to the
examples. Also, the means of cooling the thin microporous
sheet after having passed through the metallic embossing
roll and elastic roll is not limited to contacting the
cooling rolls in the examples but may be by air-cooling~
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