Note: Descriptions are shown in the official language in which they were submitted.
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REDUCED MAINTENANCE EXPLOSION DAMAGE RESISTANT
STORAGE BATTERY
BACKGROUND OF THE INVENTION
This application relates to the field of storage
batteries. In particular, this application relates to
structure integral with a storage battery rendering it
5 explosion damage resistant, and providing gas recom-
bination means to reduce or eliminate the need for
maintenace in the form of water addition.
Conventional lead-acid storage batteries, such as
used for heavy duty charge-discharge applications,
10 including such uses as powering industrial trucks,
industrial street vehicles and mine locomotives,
require frequent replacement of water. Water is iost
from such batteries due to the electrolysis of the
water in the electrolyte into hydrogen and oxygen, as
15 well as through evaporation. This electrolysis occurs
to a slight extent during operation of the battery, but
primarily during overcharge, when at least some cells
of the battery have accepted substantially full charge,
and additional energy supplied is expended in
20 electrolysis.
This problem is particularly severe when batteries
are built for extended life, by the addition of anti-
mony to the lead grids to increase the tensile strengthand retard the degradation of the positive active
material. This addition also causes undesirable side
effects, which increase the internal losses of the bat-
5 tery, resulting in a decrease in overall battery effi-
ciency, and an increased need for water additions.
This problem has largely been overcome by substituting
calcium as the hardening agent for the grids, resulting
in a reduced amount of required overcharge.
The gases evolved from a battery, primarily oxygen
and hydrogen, combine explosively when ignited. If
ignited external to the battery, the flame enters the
volume of gas confined within the battery, causing an
explosion of the battery. There have been numerous
15 attempts to solve this problem by keeping the advancing
flame front from entering the battery by the use of
porous membranes, which cooi the gases below their
ignition temperature. However, in industrial applica-
tions, it may occur that a severe overload may cause a
20 portion of the internal structure of the battery to
melt explosively, in turn igniting the gas within the
battery, and causing the battery to explode. Since the
source of ignition is internal to the battery, devices
which cool a flame front advancing towards the battery
25 are of no effect.
Batteries may also be provided with catalytic
recombination devices containing platinum or palladium,
to recombine the oxygen and hydrogen generated by the
disassociation of water during the overcharge. Such
30 devices are well-known and readily availabie in the
form of replacement vent caps, which fit onto the top
of the battery. Unfortunately, such units require con-
siderable extra space over the top of the battery and,
in most cases, this additional height is not available.
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In batteries for electric industrial trucks, the height
of the cell is at a maximum, in order to provide the
maximum number of kilowatt hours of energy for a given
size truck. The same consideratlons apply in railroad
5 applications, and, to a lesser extent, to automotive
applications. However, in automotive applications, the
addition of calcium instead of antimony as the har-
dening agent for grids reduces the quantity of explo-
sive gases generated and results in a battery which
10 does not require maintenance, since the life is five
years or less, and sufficient additional electrolyte is
initially provided to allow for losses due to disasso-
ciation of the water. Obviously, this approach is not
useful for batteries intended for industrial use or
15 long life.
The instant invention overcomes these and other
disadvantages and problems of the prior art.
SUMMARY OF THE INVENTION
_
The invention provides a battery which is explosion
20 damage resistant whether the source of ignition is
exterior or interior to the battery, and which reduces
or eliminates the need for maintenance in the form of
adding water to the battery by providing means for
catalytic recombination of the evolved gases by struc-
25 ture within the battery itself. In accordance with theinvention, the battery is rendered explosion resistant
by a honeycomb structure which is fitted over the top
of the plates, to separate the evolved gases into smaii
pockets, which will withstand the force of the
30 resultant smaller explosions without breakage in
surrounding pockets. To reduce the need for addition
of water by catalytic recombination of evolved gases, a
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hattery according to the inven-tion is provided
with a catalyst such as pa~ladium or platinum,
either as a gas recombining element in the form of
a flat plate containing a catalyst in a non-
5 wetting material resting on the honeycomb struc-
ture, or, the honeycomb structure may be made from
a suitable non-wetting sintered material including
small amounts of platinum or palladium, so that a
single structure provides both damage-preventing
10 and catalytic recombination features.
Therefore, it is a primary object of the
invention to provide a reduced maintenance, explo-
sion damage resistant storage battery. It is an
advantage of the invention that such a storage
15 battery does not require additional heiqht for the
provision of features which render it an explosion
damage resistant and reduced maintenance battery.
It is a further advantage of the invention that
such a battery is explosion damage resistant
20 whether the ignition of evolved gases is external
to the battery, or internal to the battery. It is
a feature of the invention that a honeycomb struc-
ture is disposed within the battery, resting
either on top of the plates, or slightly above the
25 plates, substantially filling the space above the
battery electgrolyte, and that the means for cata-
lytic combination of evolved gases is located
entirely within the battery.
Accordingly, the invention provides an explo-
30 sion damage resistance reduced maintenance storagebattery, including a case, a plurality oE negative
and positive plates and a quantity of electrolyte,
and defining a first chamber between the negative
and positive plates and an uppermost chamber of
35 the case. First and second strap members respec-
tively interconnect the positive and negative pla-
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tes, and respectively include first and second
post members connected to the strap members and
passing through the chamber and the uppermost sur-
face of the case. An explosion suppressing member
5 is disposed in the first c~amber and around both
the first post member and the second post member,
and defines a substantially smaller second chamher
between itself and the uppermost surface, and
divides the first chamber into a plurality of
10 separated gas chambers having lower ends helow the
surface of the electrolyte and upper ends com-
municating with the second chamber, the explosion
suppressing member being a catalyst member for
catalyzing the recombination of the valved gases
15 of the storage battery. The case defines a vent
opening through the uppermost surface and in com-
munication with the second chamber.
BRIEF DESCRIPTION OF THE DRAWI~G
FIG. 1 is a top view of a storage battery
20 according to the invention.
FIG. 2 is a side elevational sectional view
taken along line 2-2 in FIG. l, showing an
integral means for resisting explosion damage and
recombining evolved
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gases.
FIG. 3 is a side elevational sectional view, taken
along line 2-2 in FIG. 1 showing a second embodiment of
a battery provided with separate means for resisting
5 explosion damage and recombining evolved gases.
~ IG. 4 is a top elevational view of the means for
resisting explosion damage as shown in FIGS. 2 and 3.
FIG. 5 is a top elevational view of the means for
recombining evolved gases shown in FIG. 3.
FIG. 6 is a side elevational view, taken along line
6-6 in FIG. 5.
DESCRIPTION OF THE PREFE~RED EMBODIMENTS
Referring to FIG. 1, a top elevational view of a
battery incorporating the invention, shows a battery
10, having a case 12. In the illustrated embodiment
case 12 is made of polypropylene or polyethylene. The
upper end of case 12 is covered by cover member 14. It
should be noted that directional references are used
for description only, and not intended as limits on the
20 scope of the invention. As illustrated, cover member
14 is joined to case 12 by sealing material 16. Cover
member 14 has raised areas 18 surrounding positive
posts 20 and negative posts 22. Positive posts 20 and
negative posts 22 are fused to conductive inserts 24,
25 molded in the insulating material of cover member 14,
thus forming a seal around posts 20 and 22.
Preferably, inserts 24 and posts 20 and 22 are made of
pure lead or lead alloy. Cover member 14 also
includes, as iliustrated, a central raised area 26
30 surrounding a filling opening 28 which is provided with
interrupted threads 30 for retaining a conventional
battery cap or vent plug, not shown.
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FIG. 2 shows a side eievational sectional view of a
battery 10 according to the invention, where the means
for resisting explosion damage due to ignition of gases
evolved from the active elements of battery 10, par-
S ticularly during the overcharge portion of a chargingcycle, and the means for catalytically recombining the
evolved gases, oxygen and hydrogen, is a single
member. As shown, battery 10 includes a plurality of
negative plates 32 and positive plates 34. To p~event
loss of active material from the positive plates 34 as
the battery is used, a prefabricated mat 36 of finely-
divided strands of a suitable material such as glass
are used. Mats 36 are held firmly against the surfaces
of a positive plate 34, by mats shown as mats 38 and
15 40. Mat 36 is bonded to mat 38, which is wrapped
around the faces and bottom of a pl,ate 34, and mat 40
is wrapped around the faces and sides of a plate 34,
over mats 36 and 38. Thin retaining and separating
assemblies 44 hold mats 36, 38 and 40 firmly in place.
Assemblies 44 include retainers which are perforated
adjacent the central portion of the surfaces of plates
34, and imperforate along their bottom and side edges
to prevent mossing, the growth of free lead particles
at the edges of negative plates, such as plates 32,
from forming a conductive bridge between plates 32 and
34. Assemblies 44 also include microporous separators
extending beyond the edges of negative plates 32, nega-
tive plates 32 being smaller than positive plates 34,
further separating and insulating a plate 32 from a
plate 34. Negative plates 32 are supported upon bridge
member 46 by tabs 47 so that separators 44 extend
beyond the edges of negative plates 32, further
reducing the possibility of electrical shorts forming
between positive plates 34 and negatives plates 32.
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Bridge member 46 is supported above the floor 48 of
case 12 by support members 50, so that whatever sedi-
ment does form will not build unduly high in any area
of floor 48. In the view shown, tabs 52 of positive
5 plates 34 pass through perforated moss shield 54 and
are joined t~ positive strap 56, made of pure lead or a
lead alloy. Moss shield 54 reduces the opportunity for
interplate shorts forming at the tops of the plates.
Positive strap 56 is joined to positive posts 20; and
lO the connection between positive s~rap 56 and positive
post 20 is reinforced by support members 58.
Explosion damage to battery 10, due to either
internal or external ignition of evolved gases 5 iS pre-
vented by means of flash or e~plosion suppressing means
15 here shown as a honeycomb structure 60, disposed within
battery 10. hs illustrated, honeycomb member 60 rests
upon positive strap 56, and on a corresponding negative
strap, not shown in FIG. 2, thus having a lower edge 62
below electrolyte level 64 and an upper edge 66 which
20 is above electrolyte level 64 in battery 10. As
illustrated, member 60 fills the majority of the volume
of a first chamber 59 between moss shield 54 and cover
member 14. As shown, a small space or second chamber
68 may be left above honeycomb member 60, to allow the
25 escape of any gases which may be evolved and not pre-
viously recombined. As shown, member 60 is formed to
fit closely around battery posts, such as positive post
20 and negative post 22, support members 58, and wall
70, which defines filling opening 28. ~s shown, member
30 60 has a reduced-diameter opening 72 adjacent filling
opening 28, between moss shield 54 and lower edge 74 of
wall 70, adequate to receive a hydrometer or ther-
mometer, while reducing the amount of gas which may be
contained in filling opening 28 to the smallest
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possible amount. Evolved gas which may escape, escapes
through vent openings 75 in wall 70. As can be seen,
member 60 thus divides the majority of the space within
battery 10 above electrolyte level 64 into a plurality
5 of individual pockets or chambers 76, each so small
that ignition of gas within one such pocket will not
result in any damage to battery ~0, and isolates the
gas in one pocket from gases in other such pockets, to
minimize and localize the explosive results of ignition
lO of evolved gases. Although there is some communication
between pockets 76 through space 68, it will be
apparent that, due to the presence of member 60, and
its thermal mass, the majority of the evolved gases
within battery 10 may be held below combustion tem-
15 perature even if a small volume of evolved gases israised above combustion temperature by some means of
ignition, either within or without battery 10.
~ oneycomb member 60 must be made of a material
which is inert to the electrolyte used, and may be made
20 of any appropriate material. For instance, it may be
made of lead, to further improve its heat-absorption
capability and explosion reduction capability, or, as
illustrated, may include a material which catalyzes the
recombination of evoived gases such as hydrogen and
25 oxygen. Platinum and palladium are well-known
materials for this purpose. If member 60 is made of
lead, it must be electrically insulated from po~itive
and negative straps such as strap 56 by a layer of a
suitable plastic material, not shown.
As illustrated, member 60 is made of a powdered
material, preferably a hydrophobic material which
resists flooding, and small pellets 77 of a catalyst
material such as platinum or palladium mixed and molded
in the form of member 60. Among the materials useful
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to support the peilets of catalyst material is poly-
tetrafluoroethylene resin, such as is sold under the
registered trademark Teflon. Other suitable moiding
materials which are resistant to the electrolyte used
5 will be apparent, and may also be used.
Member 60 may also be formed of an inert material,
and subsequently plated with platinum or palladium. A
member 60 plated with a catalyst, such as by flash-
plating, will serve to recombine much of the evo~ved
lO gas, reducing the loss of water from the electrolyte,
and reducing the need for maintenance, while simulta-
neously reducing the magnitude of any explosion that
may result from ignition of evolved gases to a magni-
tude which will not cause bursting of the battery and
15 throwing about of acid electrolyte.
FIG. 3 is a partial view of a battery 10, showing a
second preferred embodiment of means for resisting
explosion and reducing water loss due to evolved gases.
As in the embodiment shown in FIG. 2, a flash or explo-
20 sion suppressing means here shown as honeycomb member60a is disposed within battery 10, extending both above
and below electrolyte level 64. In the embodiment
illustrated, honeycomb member 60a does not perform a
catalytic recombination function, but mere'y protects
25 battery 10 against the results of ignition of evolved
gases. A means for recombining the evolved gases is
shown disposed in a space or chamber identified with
the referene number 68 in FIG. 2, between the top edge
66 of the honeycomb member 60a and cover member 14.
As shown in FIG. 3, a catalyst member f~8 iS substan-
tially planar, and includes a catalytic mixture 80
including catalyst pellets 82 in a hydrophcbic powder
84. Preferably, pellets 82 are of platinum or palla-
dium, and hydrophobic or non wetting powder 84 is
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silica carbor or graphite powder treated with a
hydrophobic material such as silicon or powdered
Teflon. Thus, pellets 82 are supported, and protected
against an uncontrolled rate of contact with evolved
5 gases. Mixture 82 is constrained between a first plate
member 86 and a second plate member 88. Both first and
second plate member 86 and 88 are perforated, to allow
the entrance of evolved gases, the perforations being
small enough to prevent the escape of catalytic mixture
10 80. Preferably, plate members 86 and 88 are made of
lead, to assist in dissipation of the heat of recom-
bination of the evolved gases, but can also be made of
any suitable plastic.
Referring now to FIG. 4~ a top plan view of a pre-
15 ferred embodiment of a member such as 60 or 60a is
shown. As shown, member 60, 60a defines a plurality of
honeycomb-shaped chambers or pockets 76, thus dividing
the gases within battery 10 into small individual
pockets. Honeycomb member 60, 60a is provided with
20 opening 90 to clear positive and negative battery posts
20 and 22, and with recesses 92 to clear support
members 58, if used, and with a recess 94 to clear wall
70 of filling opening 28, as well as a reduced-diameter
filling opening 72, here shown centrally disposed as
25 appropriate for the battery shown in FIGS. 1-3.
Referring now to FIG. 5 and 6, a catalyst member
78, as shown in FIG. 3, is depicted. First plate
me~ber 86 and second plate member 88 are joined
together at edges 96, catalyst member 78 defining a
30 plurality of openings 98, to provide for the passage of
battery posts such as post 20, 24 therethrough, and a
filling opening 100, here shown as a centrally-disposed
filling opening. In the embodiment illustrated, first
and second plate members 86, 88 are perforated by
.
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shearing a portion of the periphery of a plurality of
areas 102. As shown in FIG. 6, edges 104 of areas 102
are deflected inwardly, defining openings 106 which are
too small to allow the escape of catalytic mixture 80.
As will be apparent, numerous variations and modi-
fications of the catalytic recombination means and
explosion resistant means disclosed herein will be
obvious to one skilled in the relevant art, and may be
easily made without further invention and without
lO departing from the spirit and scope of this invention.
