Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
1998-06-05
2001-02-06
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S164000
Reexamination Certificate
active
06183902
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a galvanic cell employing an inward beaded contour cup and a can assembly that occupies a relatively small volume so that the internal volume of this cell is reserved primarily for the active components of the cell. This invention also relates to a process for producing a galvanic cell employing an inward beaded contour cup and having optimum internal volume for the active components of the cell.
BACKGROUND OF THE INVENTION
The miniaturization of electronic devices has created a demand for small but powerful electrochemical cells. Cells that utilize an alkaline electrolyte are known to provide high energy density per unit volume, and are therefore well suited for applications in miniature electronic devices such as hearing aids, cameras, watches and calculators. However, alkaline electrolytes, such as aqueous potassium hydroxide and sodium hydroxide solutions, have an affinity for wetting metal surfaces and are known to creep through the sealed metal interface of an electrochemical cell. Leakage in this manner can deplete the electrolyte solution from the cell and can also cause a corrosive deposit on the surface of the cell that detracts from the cell's appearance and marketability. These corrosive salts may also damage the device in which the cell is housed. Typical cell systems where this problem is encountered include silver oxide-zinc cells, nickel-cadmium cells, air depolarized cells, and alkaline-manganese dioxide cells.
In the prior art it has been a conventional practice to incorporate insulating gaskets between the cell's cup and can so as to provide a seal for the cell. Generally, the gasket must be made of a material inert to the electrolyte contained in the cell and the cell environment. In addition, it must be flexible and resistant to cold flow under pressure of the seal and maintain these characteristics so as to insure a proper seal during long periods of storage. Material such as nylon, polypropylene, ethylene-tetrafluoroethylene copolymer and high density polyethylene have been found to be suitable as gasket materials for most applications. Typically, the insulating gasket is in the form of a “J” shaped configuration in which the extended wall of the cup is inserted so that upon being radially squeezed, a flange of the gasket forms a seal with the bottom portion of the wall of the cup. The gasket generally extends the entire length of the internal wall of the cell. The volume of the gasket could exceed as much as 20% of the internal volume of the cell and therefore results in a waste of space in the cell for the active components of the cell. To better insure a good seal, a sealant is generally applied to the gasket, including its “U” shaped groove, so that upon insertion of the cup into the gasket, the edge of the extended wall of the cup will seat in the sealant and then upon the application of a compressive force, the wall of the gasket will be compressed against the edge of the extended cup wall.
U.S. Pat. No. 4,302,517 discloses a sealed galvanic cell employing an insulating gasket between the can and the cup of the cell. The cell is composed of a first sealing segment disposed and compressed between the rim of the can and the edge of the cup and a second can support segment extending within the cup and substantially parallel to the wall of the cup and defining a plurality of spaced apart openings which accommodate the cell's electrolyte and/or the cell's reaction product.
It is an object of the present invention to provide a cell structure that employs an inward beaded contour cup and a can housing that occupies a minimum internal volume for the cell.
It is another object of the present invention to provide an inward beaded contour cup and a can housing for a cylindrical cell that uses a low profile gasket disposed between the cup and can to electrically insulate the cup from the can and to provide a seal for the cell so that the cell has a large internal volume for its active components.
It is another object of the present invention to provide a novel inward beaded contour cup and a can housing for a cell that is easy to make, cost effective to produce and easy to assemble.
It is another object of the present invention to provide a process for producing a cell with a novel inward beaded contour cup and a can housing occupying a minimum volume for the cell.
The foregoing and additional objects of the present invention will become more fully apparent from the following description and drawings.
DESCRIPTION OF THE INVENTION
One aspect of the invention relates to a galvanic cell comprising a first electrode having a polarity; a second electrode of opposite polarity; a separator between said first electrode and said second electrode; an electrolyte; a two-part conductive housing containing said first electrode, said second electrode, said separator and said electrolyte, the first part of said housing being a can electrically connected to said first electrode and having a wall and an edge defining an opening, and the second part of said housing being a cup electrically connected to said second electrode and having an upstanding wall with an outer surface and an edge end defining an opening and having an inward beaded area at the vicinity of the open end of the cup, and an insulating gasket comprising a base member having at least one upstanding wall, preferably an outer wall and an inner wall spaced apart from the outer wall thereby defining a “U” shaped groove; wherein the edge of the can's wall is disposed against said gasket, preferably within the groove of said gasket; one upstanding wall of said gasket is disposed between the wall of the can and the wall of the cup; and the base member of said gasket is seated on the beaded area of the cup producing a sealed galvanic cell.
Preferably, the beaded area of the cup's wall is composed of a portion of the cup's wall folded upon itself. The beaded area is disposed at the vicinity of the open end of the cup and provides a support for the low profile gasket during sealing of the cell. The inner wall of the gasket is seated on the peripheral area of the separator of the cell to secure the first electrode within the can of the cell. Another embodiment of the invention would entail the use of a ring or similar component between the inner wall of the gasket and the separator so that the inner wall of the gasket would be seated on the separator via the ring or other type of component, preferably a firm component.
In the conventional cell construction, an electrode dome is seen as a problem. The electrode dome reduces the internal volume in the anode compartment and also could cause delamination or breakage of the protective membrane which could result in leakage. The electrode dome is the result of the electrode compression at the circumferencial edge of the electrode caused by the compression of the gasket. The electrode dome can be effectively eliminated by controlling the material flex direction. Thus a mechanism should be made that will set the flex direction and also provide room to accommodate the deflection. The flex direction can be controlled by simply blanking an oversize disc electrode to fit the cathode can. The effect will be similar to the use of a wedge type masher. The wedging of the electrode also will provide excellent electrical contact of the metallic screen with the cathode can. To accommodate the electrode, the cathode can may contain a shallow outward embossment as shown on FIG.
6
. The embossed can also serves as a controlled gap for uniform air diffusion across the surface of the electrode membrane.
As shown in
FIG. 5
, the vertical height B from the open end of the cup to the beaded contour should preferably be located between 5% and 40% of the vertical length A of the upstanding wall of the cup measured from the open end of the cup, more preferably located between 8% and 30% of the vertical length of the upstanding wall and most preferably located between 10% and 25% of the vertical length of the upstand
Eveready Battery Company Inc.
Kalafut Stephen
Ruthkosky Mark
Toye, Jr. Russell H.
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