Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed...
Patent
1986-06-30
1987-07-07
Walton, Donald L.
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
429 56, H01M 212
Patent
active
046787259
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hermetically sealed storage battery comprising a group of plates as packaged in a synthetic resin film or sheet wrapping which is electrolyte-resistant and heat-weldable. The invention simplifies the construction of a housing for a group of plates, with the housing itself constituting a safety valve necessary for a storage battery.
BACKGROUND ART
Regarding the primary battery which is not charged and produces no gas or little gas in discharge, there is known a construction such that the current generation element and plate group are packaged liquid- and gas-tight in a synthetic resin film housing. In this construction, the housing structure for the battery is very much simplified.
However, in the storage battery which is charged and produces gases in charge, mere enclosure of the plate group by such a housing does not allow withdrawal of evolved gases from the cell and with a gradual build-up of the internal pressure of the cell, the housing is ruptured to cause scattering of the electrolyte, etc. Thus, this type of housing as such is not desirabIe and a safety mechanism that permits withdrawal of gases was required.
As electrical appliances using a storage battery as a power source and, particularly, portable electrical appliances are progressively miniaturized and reduced in thickness, there has been a demand for a hermetically sealed storage battery which is similarly compact and thin and long serviceable.
DISCLOSURE OF THE INVENTION
The present invention provides a hermetically sealed storage battery which is suitable for use as a power source in such applications. The hermetically sealed storage battery according to the present invention comprises a group of plates held in an electrolyte as hermetically sealed in a wrapping or housing constituted by a synthetic resin film or sheet which is electrolyte-resistant and heat-weldable, with portions of the housing which surround the periphery of said group of plates excepting a safety valve portion being formed into a sealing portion by thermal interwelding of strips of the resin film or sheet, and a pair of terminal pieces protruding from the group of positive and negative plates through the sealing portion, said safety valve being constituted by an adhesion portion formed by portions of the film or sheet which are laid one upon the other so that when the internal pressure of the cell increases beyond a predetermined level, said adhesion portion is opened by the gas accumulated in the cell to allow the gas to escape to the atmosphere.
The plate group is formed in such a manner that the electrical capacity of the positive plate is larger than that of the negative plates, and the electrolyte is held by these plates and a separator so as to ensure no liberation of electrolyte and the oxygen gas evolved from the positive plate upon charging is ionized and removed by the negative plates so that, as a battery, the positive plate is rate-determining.
Therefore, when the amount of oxygen gas evolved from the positive plate at charging is within the capacity of the negative plates to ionize and remove the oxygen gas, the gas is absorbed and removed by the negative plates within the cell and substantially none escapes through the safety valve. Thus, the hermetic sealing effect is easily accomplished.
However, if the amount of oxygen gas evolved form the positive plate exceeds the capacity of the negative plates to absorb and remove the oxygen gas, the evolved oxygen gas is accumulated within the cell to increase internal pressure of the cell and when this pressure exceeds the physical strength of the housing itself, the housing is ruptured to damage the battery and the appliance using the battery as a power source is also damaged.
The safety valve is provided for preventing such an event, and when the internal pressure of the cell exceeds a limit, the adhesion portion is expanded by the gas in the cell so as to let the gas escape out to keep the storage battery safe.
The safety valve in the present invention
REFERENCES:
patent: 2282459 (1942-05-01), Deeley
patent: 3607401 (1971-09-01), Halpert
patent: 3870566 (1975-03-01), Bergum et al.
patent: 4256813 (1981-03-01), Kniazzeh
patent: 4439500 (1984-03-01), Gibbard et al.
Kikuchi Yoichi
Kobayashi Kenji
Matsushita Electric Industrial Co., Inc.
Walton Donald L.
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