Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
1998-12-18
2001-08-14
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S006000, C429S006000, C429S010000
Reexamination Certificate
active
06274261
ABSTRACT:
TECHNICAL FIELD
The present invention relates to metal-air batteries of the type that are supplied with reactive gas by an active air moving device, and more particularly relates to a cylindrical metal-air cell having a cylindrical peripheral air cathode.
BACKGROUND OF THE INVENTION
Generally described, a metal-air cell, such as a zinc-air cell, uses one or more air permeable cathodes separated from a metallic zinc anode by an aqueous electrolyte. During operation of the cell, oxygen from the ambient air is converted at the one or more cathodes to produce hydroxide ions. The metallic zinc anode is then oxidized by the hydroxide ions. Water and electrons are released in this electrochemical reaction to provide electrical power.
Initially, metal-air cells found limited commercial use in devices, such as hearing aids, which required a low level of power. In these cells, the air openings which admitted air to the air cathode were so small that the cells could operate for some time without flooding or drying out as a result of the typical difference between the outside relative humidity and the water vapor pressure within the cell. However, the power output of such cells was too low to operate devices such as camcorders, cellular phones, or laptop computers. Furthermore, enlarging the air openings of a typical “button cell” was not practical because it would lead to premature failure as a result of flooding or drying out
In order to increase the power output of metal-air cells so that they could be used to operate devices such as camcorders, cellular phones, or laptop computers, air managers were developed with a view to providing a flow of reactive air to the air cathodes of one or more metal-air cells while isolating the cells from environmental air and humidity when no output is required. As compared to conventional electrochemical power sources, metal-air cells containing air managers provide relatively high power output and long lifetime with relatively low weight. These advantages are due in part to the fact that metal-air cells utilize oxygen from the ambient air as the reactant in the electrochemical process as opposed to a heavier material such as a metal or a metallic composition. Examples of air managers are shown in U.S. Pat. Nos. 4,913,983, 5,356,729, and 5,691,074.
Attempts have been made to design a metal-air cell to fit the form of a standard “D” or “AA” cylindrical alkaline cell. Cylindrical batteries without air managers are shown in U.S. Pat. No. 3,697,326 and European Published Application No. 1,459,135. The lack of success of these designs likely is attributable to an inability to provide high enough power output for devices typically operated by conventional standard sized cylindrical cells without providing large air openings that allow the cells to flood or dry out.
Thus, there is a need in the art for a standard size cylindrical metal-air cell that can provide a power output level sufficient to operate electrical devices, whether individually or in groups inserted into a battery compartment of such devices. Such a cell also should not flood or dry out when inserted into such devices and left unattended during extended periods of non-use.
SUMMARY OF THE INVENTION
The present invention seeks to provide a cylindrical metal-air cell that can provide a high power output level, and also can be inserted into electrical devices and left unattended during extended periods of non-use without flooding or drying out.
This object is achieved according to the present invention by a cylindrical metal-air cell having a generally cylindrical housing, a generally cylindrical oxygen electrode extending axially adjacent an interior surface of the housing, a plurality of elongate plenums defined between the oxygen electrode and the interior surface of the housing, an isolating passageway positioned between the ambient environment and each of the plenums, and an air moving device operable when on for forcing air through the isolating passageways and into at least one of the plenums. The isolating passageways are operable while unsealed and the air moving device is not forcing air through the isolating passageway to protect the cell from the ambient environment.
In one embodiment of the present invention, the axial plenums are formed by the shape of the electrode material, preferably a conductive, carbon-containing material. In this embodiment, the housing or case may be smoothly cylindrical. In another embodiment, the housing forms multiple axial plenums and the outer surface of the electrode material may be smoothly cylindrical. In either embodiment, the housing may be conductive, and the carbon material of the electrode may contact the housing to provide current collection for the electrode.
Preferably, the isolating passageways are formed in end pieces that seal the ends of the housing. The air moving device may be any appropriate apparatus for moving air, such as a miniature fan, a micromachine fan, or a diaphragm air pump. In an alternative embodiment of the invention, the isolating passageways may be provided only at one end of the housing and an air pathway may be defined so that air may be moved from that end along one set of the axial plenums in one direction along the cell, and returned along another set of the axial plenums in the opposite direction. Also, air may be forced into and out of a plenum through the same isolating passageway.
Cells embodying the present invention can be used individually, combined in a battery pack, or placed in groups in conventional battery compartments of electrical devices where the cells are connected in series or in parallel. Each cell having a standard “D” size can produce a power output of at least about 1.25 watt using a micromachine blower that draws 10% or less of the cell's available power while moving air at a rate of 75 cc per minute or higher. Each cell having a standard “AA” size can produce a power output of at least 0.5 watt using a micromachine fan that draws 10% or less of the cell's available power while moving air at a rate of 30 cc per minute or higher. It is possible to construct cells embodying the present invention having a standard “D” size that produce a power output of 2.5 watt or more using a micromachine blower that draws 10% or less of the cell's available power while moving air at a rate of 150 cc per minute or higher, and cells having a standard “AA” size that produce a power output of 1.0 watt or more using a micromachine fan that draws 10% or less of the cell's available power while moving air at a rate of 60 cc per minute or higher.
Other objects, features and advantages of the present invention will become apparent upon reviewing the following detailed description of preferred embodiments of the invention, when taken in conjunction with the drawings and the appended claims.
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Bentz R. Dennis
Tinker Lawrence A.
AER Energy Resources Inc.
Alejandro Raymond
Alston & Bird LLP
Chaney Carol
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