Pressure sensitive ciruit breaker

Details Pressure sensitive ciruit breaker Pressure sensitive ciruit breaker

1998-11-04

2001-06-19

Maples, John S. (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With control means responsive to battery condition sensing...

C429S057000, C429S090000

Reexamination Certificate

active

06248470

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressure sensitive circuit breaker (hereinafter referred to as “PSCB”) to be used for ensuring the safety of a storage battery such as a secondary battery capable of being regenerated by re-charging. Particularly, the invention is concerned with a PSCB having a rectangular lid.
2. Description of the Prior Art
If a storage battery of this type is continued to be charged even after completion of charging or if it is charged with an electric current larger than a predetermined current, a trouble may arise in the storage batter, with evolution of gas therein, increase of pressure and temperature in the battery, consequent swelling of the battery, further, oozing of electrolyte caused by cracking and consequent bad influence on the device in which the battery is installed. Even if the result is not to such an extent, if the battery is continued to be used in such a state, the aforesaid swelling of the battery will proceed and may cause cracking or burst. Thus, as to a storage battery which has undergone some trouble, it is necessary to stop the use thereof immediately.
Among the devices for which the reduction of size has been required recently, there are many devices which are characterized by their small wall thickness. With this tendency, square or rectangular batteries have come to be used. Also in this case, reduction of thickness remains to be solved. On the other hand, in reply to a keen demand for safety, it is necessary to incorporate a safety valve and a current cut-off mechanism in such devices.
In a conventional PSCB referred to above, when the internal pressure of a storage battery increases due to some abnormal chemical change of a power generating element, the increased pressure acts on a safety valve, so that the safety valve is lifted and an electric conduction passage which connects a central projection with a lead through a lead stripper plate is stripped or broken. As the pressure further increases and reaches a predetermined level, a thin-walled portion of the safety valve is broken and a gas present in a battery case and having the increased pressure is released to the exterior through a hole formed in a lid.
However, the prior art described above involves a problem of complicated manufacture because a member for diaphragm is connected to the lid (a negative case) by caulking or welding. Particularly, in the case of welding, since spot welding is performed continuously, it has so far been necessary to ensure reliability of the welded portion so as to afford a satisfactory airtightness of the same portion and also necessary to inspect the welded portion.
Since two spaces (edges) for welding or caulking are needed in the transverse direction, the width of the diaphragm is narrowed relative to the width of the battery, resulting in that it becomes difficult to take a certain displacement of the diaphragm.
Even if the shape of the diaphragm is made elliptic or the like, it is not so effective because the diaphragm displacement is substantially restricted at a portion where the distance between the center and the peripheral edge is the shortest.
SUMMARY OF THE INVENTION
It is the first object of the present invention to provide a PSCB not requiring such a bonding allowance for the portion to be welded as in the prior art, capable of forming a large diaphragm portion and reducing the size, especially thickness, of a battery in its external form, permitting a large displacement of the diaphragm portion and ensuring a reliable operation thereof, permitting the diaphragm portion to be easily machined with a high accuracy integrally with a lid by grinding, with neither a hole nor a gap being formed in a bonded portion by welding which hole or gap is formed in the prior art, and capable of greatly reducing the number of machining and testing steps.
It is the second object of the present invention to provide a PSCB which permits a safety valve portion to be machined simultaneously with the diaphragm portion by grinding and which is easy to manufacture.
It is the third object of the present invention to provide a PSCB wherein a holder can be fixed without any substantial increase in the number of components even with omission of the conventional member for diaphragm.
The above first object is attained by the first means comprising a lid connected to a case of a battery in an airtight manner, a diaphragm portion formed by grinding a part of the lid so as to have a wall thickness which is small in comparison with other portions of the lid, the diaphragm portion being displaced by an internal pressure of the battery, a cut-off member having an electric conduction passage and held directly or indirectly by the lid, the cut-off member functioning to cut off the electric conduction passage by displacement of the diaphragm portion with an increase in internal pressure of the battery, an outer connection means connected to one end of the electric conduction passage of the cut-off member, and an inner connection means for connecting an opposite end of the electric conduction passage of the cut-off member with a power generating element located in the interior of the battery.
The above second object is attained by a second means in combination with the first means wherein the lid has a safety valve integral with the lid, a part of the safety valve being broken when the internal pressure of the battery reaches a predetermined value or more, said part of the safety valve being small in wall thickness in comparison with other portions of the lid.
The above third object is attained by a third means in combination with the first means which has an insulating holder and a fixing portion formed in the holder by insert molding, the fixing portion being made of a metal and connected to the outer or the inner connection means and welded to the lid.


REFERENCES:
patent: 4345611 (1982-08-01), Ikeda et al.
patent: 4943497 (1990-07-01), Oishi et al.
patent: 5985478 (1999-11-01), Kim

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