Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer or spacer insulating structure
Reexamination Certificate
1997-07-11
2001-05-22
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer or spacer insulating structure
C429S176000, C429S204000, C429S228000
Reexamination Certificate
active
06235421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an enclosed lead storage battery which employs, as electrode plates, grids each having no frames at its opposite lateral sides, such as an expanded grid.
2. Description of the Related Art
Generally, a group of electrode plates for use in an enclosed lead storage battery are constructed by layering a positive electrode plate, a separator formed of a water-absorbent glass mat, and a negative electrode plate in sequence side by side, and are then housed in an enclosed container. When an electrolyte is poured into the container housing the group of electrode plates therein, all of the electrolyte is held in the water-absorbent glass mat serving as the separator. Therefore, the electrolyte is hardly present in the container under such a free or liberated condition that the electrolyte is too much in excess of the electrolyte holding ability of the separator. In such an enclosed lead storage battery, oxygen generated from the positive electrode plate in an overcharged state is absorbed by the negative electrode plate, thereby preventing an excessive rise in internal pressure of the storage battery.
In many cases, cast grids each having frames on its opposite lateral sides are employed as grids constituting the positive and negative electrode plates. Also, as stated above, the electrolyte is kept from being present under the free or liberated condition. Therefore, lead is prevented from depositing on the opposite lateral sides of the electrode plate, thereby ensuring the protection against a short-circuit.
Meanwhile, grids each having no frames on its opposite lateral sides (e.g., expanded grids) have often been employed as, particularly, the negative electrode plates in recent years. For an electrode plate employing such an expanded grid which has no frames on its opposite lateral sides, however, there is a fear that the repetition of charging and discharging cycles may cause an active material to swell out of the opposite lateral sides of the negative electrode plate, extend further along the inner wall surfaces of the container beyond the separator, and finally come into contact with the opposite lateral sides of the positive electrode plate, thus giving rise to a short-circuit.
SUMMARY OF THE INVENTION
With the view of solving the above-stated problem in the related art, an object of the present invention is to provide an enclosed lead storage battery wherein grids each having no frames at their opposite lateral sides are employed as electrode plates, while ensuring prevention of a short-circuit between the lateral sides of negative and positive electrodes plates.
To achieve the above object, according to the present invention, the opposite lateral sides of a group of electrode plates comprising positive electrode plates, negative electrode plates and separators layered side by side are covered by a porous mat in the direction in which the electrode plates are layered. The porous mats fills, particularly, spaces between the lateral sides of the negative electrode plates and the adjacent separators. With this construction, an active material swelling at the opposite lateral sides of the negative electrode plates during repeated charging and discharging cycles is prevented by the presence of the porous mat from reaching the opposite lateral sides of the positive electrode plates while bypassing the separators. Thus, an enclosed lead storage battery can be provided in which a short-circuit between the lateral sides of the negative and positive electrode plates is surely avoided.
REFERENCES:
patent: 4262068 (1981-04-01), Kono et al.
patent: 5468575 (1995-11-01), Holland et al.
patent: 540491 (1941-05-01), None
patent: WO8101076 (1981-04-01), None
European Search Report dated Jan. 21, 2000.
Patent Abstracts of Japan, vol. 009, No. 225, (E-342), Sep. 11, 1985 & JP 60 081776 A (Matsushita Denki Sangyo KK), May 9, 1985.
Patent Abstracts of Japan, vol. 011, No. 384 (E-565), Dec. 15, 1987 & JP 62 150649 A (Matsushita Electic Ind Co. Ltd.), Jul. 4, 1987.
Patent Abstracts of Japan, vol. 012, No. 337 (E-657), Sep. 12, 1988 & JP 63 102172 A (Japan Storage Battery Co. Ltd.), May 7, 1988.
Hattori Takashi
Hiramatsu Akitoshi
Kashio Gou
Taniguchi Akihiro
Maples John S.
Matsushita Electric - Industrial Co., Ltd.
Stevens Davis Miller & Mosher L.L.P.
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