Alkaline dry cell

Details Alkaline dry cell Alkaline dry cell

1998-07-23

2001-05-22

Brouillette, Gabrielle (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S229000, C429S206000, C429S165000, C429S060000

Reexamination Certificate

active

06235429

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an alkaline dry cell, and more particularly to an alkaline dry cell having characteristics particularly suitable as power for the flash of a camera.
2. Description of the Related Art
The alkaline dry cell is generally formed of a hollow cylindrically-formed cathode depolarizing mixture having electrolytic manganese dioxide as an active material and a gel anode having zinc alloy powder as an active material, which are placed with a cylindrical separator therebetween in a metallic cathode can which is a closed-end cylinder and doubles as a cathode terminal, and a metallic anode current collector which is inserted into the gel anode.
Recently, demands for the alkaline dry cell is sharply expanding with the increased use of various equipment and, researches are being made vigorously to increase its capacity. To increase the capacity, there is a method which, for example, increases the inner volume of the cell by making the cathode can and the separator thinner, so that an amount of the active material can be increased.
The alkaline dry cell has long been used as power for a remote control and a personal portable. In addition, a large demand is expected for the alkaline dry cell as power for a personal handy phone and the flash of a single-use camera in these years. To use the alkaline dry cell as power for the flash of a single-use camera, it is necessary to get a large current temporarily but an amount of the active material is not required to be increased largely. For example, cells now available on the market have a utilization factor of less than 30% of the active material. Thus, its utilization factor is small. Therefore, the improvement being made in the alkaline dry cell in these years, namely a method of increasing the inner capacity of the cell in order to increase the theoretical capacity, is not necessarily suitable to use it as power for the flash of a single-use camera.
In view of the aforementioned circumstances, the invention was achieved to provide an alkaline dry cell having performance particularly suitable as power for the flash of a single-use camera.
SUMMARY OF THE INVENTION
The invention relates to an alkaline dry cell, which is formed of a hollow cylindrically-formed cathode depolarizing mixture having electrolytic manganese dioxide as an active material and a gel anode having zinc alloy powder as an active material, which are placed with a cylindrical separator therebetween in a metallic cathode can which is a closed-end cylinder and doubles as a cathode terminal, and a metallic anode current collector which is inserted into the gel anode, wherein the electrolytic manganese dioxide is in an amount of 1.71 g or more, the zinc alloy powder is 0.65 g or more, a theoretical capacity ratio (N
E
/P
E
) between the anode and the cathode is in a range of 1.0 to 1.20, and an area ratio (P
A
/N
A
) between an anode-opposed area of the cathode depolarizing mixture and a contact area of the current collector against the gel anode is in a range of 1.82 to 8.24.
The conventional alkaline dry cell contains the cathode active material (electrolytic manganese dioxide) in an amount of about 3.5 g or more and the anode active material (zinc alloy powder) in an amount of about 1.5 g or more. As described above, the theoretical capacity of the cell as power for the flash is satisfactory in a half of a commercially available cell. In the present invention, electrolytic manganese dioxide is decreased to 1.71 g (value resulting from the conversion with purity set to 92%) or more and zinc alloy powder to 0.65 g or more, both smaller than they were used conventionally.
Since the active materials are decreased in their amounts, the formed cathode depolarizing mixture can be made to have a thinner wall, and the anode current collector can be made larger accordingly. Therefore, a contact area between the anode current collector and the gel anode can be increased. In the alkaline dry cell, the matallic anode current collector is generally made to have a rod shape. It is welded to a metal top of the anode terminal and inserted into the gel anode in order to take an electric current. In other words, the collector takes an electric current directly through its part which is in contact with the gel anode, so that an increase of the contact area with the gel anode is advantageous to take a large current. Therefore, the invention, which can have a large contact area between the anode current collector and the gel anode, is advantageous in taking a large current.
When a theoretical capacity ratio (N
E
/P
E
) between an anode theoretical capacity (N
E
, Ah) and a cathode theoretical capacity (P
E
, Ah) is 1.0 or below, a utilization ratio of the active materials decreases, so it is not practical. And when it exceeds 1.20, the cathode active material reacts excessively, and the anode active material and the current collector produce gas by their electrochemical reaction when the cathode reaction material has completed its reaction. These decreases a reliability of a dry cell.
And, when an area ratio (P
A
/N
A
) between an anode-opposed area (P
A
) of the cathode depolarizing mixture and a contact area (N
A
) of the anode current collector against the gel anode is larger than 8.24, the anode current collector has a lowered current collecting capacity, so that it is not practical. And, when the area ratio is less than 1.82, it is hard to have a required filling amount of the gel anode. Meanwhile, the conventional alkaline dry cell has an area ratio (P
A
/N
A
) of about 9.0 to 11.00.


REFERENCES:
patent: 5300371 (1994-04-01), Tomantschger et al.
patent: 5340666 (1994-08-01), Tomantschger et al.
patent: 5424145 (1995-06-01), Tomantschger et al.

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