Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed... – Blowout type
Reexamination Certificate
2001-05-17
2003-10-14
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
Blowout type
C429S061000
Reexamination Certificate
active
06632559
ABSTRACT:
INDUSTRIAL FIELD
The present invention relates to a safety device to make a closed battery explosion-proof and a closed battery with the safety device.
BACKGROUND OF THE INVENTION
Recently, a lithium battery with non-water electrolytic solution and a secondary battery with non-water electrolytic solution for a lithium ion battery have been broadly employed for pocket electronic tools.
Although the secondary battery has a high electro motive force, the secondary battery would explode in case of increasing inner pressure caused by chemical reaction in an electrode member with a positive electrode and a negative electrode installed in an outer container. For example, when a non-aqueous electrolytic solution battery such as a lithium secondary battery is in an overcharge condition or a large amount of electric current is flown into the battery in a short circuit condition caused by a wrong operation, non-aqueous electrolytic solution is absorbed in the electrode member and gas is produced. When the gas is continuously produced in the outer container and the inner pressure of the outer container is increased, the battery would eventually explode.
In order to avoid such an explosion, a closed battery for pocket electronic tools was developed as shown in Japanese Patent Laid-Open Publication No. 6-338305.
In the conventional art, a positive electrode lid provided at an edge of an outer container comprises a metallic porous plate affected as the inner most lid and connected to a positive electrode of an electrode member through a positive electrode lead, a metallic explosion-proof valve affected as an intermediate lid electrically connected to the metallic porous plate through a central adhered portion and a metallic cap terminal electrically connected to the metallic explosion-proof valve.
Under the structure as described above, when the inner pressure of the battery is increased, the metallic porous plate and the metallic explosion-proof plate are electrically isolated by breaking the central adhered portion and gas produced in the inside of the battery is discharged by breaking a part of the metallic explosion-proof valve so as to avoid an explosion of the battery.
However, in a conventional closed battery, some drawbacks remain. Although a central adhered portion is formed by welding a central portion of a metallic porous plate and a metallic explosion-proof valve by spot welding, it is difficult to weld all the portions uniformly by spot welding and a welding strength of each closed battery is not constant. As the result, the inner pressure of a battery for isolating a communication between the metallic porous plate and the metallic explosion-proof plate is not constant. In the case of a closed battery, although the inner pressure of the battery rises to a predetermined isolation pressure, a communication between the metallic porous plate and the metallic explosion-proof can not be isolated. Thus, a reliability of a closed battery is damaged in view of safety.
In order to solve the above problems, a purpose of the present invention is to provide a safety device of a closed battery in which a pressure plate and a shield plate can be isolated certainly and the safety of the closed battery can be maintained sufficiently even if the inner pressure of the battery exceeds a predetermined level, and a closed battery with the safety device.
DISCLOSURE OF THE INVENTION
To accomplish the above purpose, a safety device of a closed battery as claimed in claim I comprises a positive electrode lid attached at one end of an outer container, the positive electrode lid including a pressure plate effected as the innermost lid and electrically connected to a positive electrode of an electrode member through a positive electrode lead, a shield plate effected as an intermediate lid and electrically connected to the pressure plate through a central contacting portion, and a sealing plate affected as the outermost lid and electrically connected to the shield lid wherein at least one gas flow hole is provided at the pressure plate so as to communicate the internal space of the outer container with a contacting space between the pressure plate and the shield plate. A central contacting portion includes a protrusion which protrudes from a-central portion of the pressure plate toward the shield plate and having a first flat contacting surface and a second contacting surface provided at the central portion of the shield plate and contacting with the first flat contacting surface of the protrusion. The pressure plate and the shield plate are isolated when the inner pressure level of the outer container exceeds a predetermined electric current isolation pressure.
A safety device as claimed in claim
2
comprises a positive electrode lid attached at one end of an outer container, the positive electrode lid including a pressure plate effected as the innermost lid and electrically connected to a positive electrode of an electrode member through a positive electrode lead, a shield plate effected as an intermediate lid and electrically connected to the pressure plate through a central contacting portion, and a sealing plate affected as the outermost lid and electrically connected to the shield lid, wherein at least one gas flow hole is provided at the pressure plate so as to communicate the internal portion of the outer container with a contacting space between the pressure plate and the shield plate. A plurality of circular grooves are formed at a substantially central portion of the shield plate except for connecting tab portions which are coaxially notched and alternatively arranged with an angle of 180° so as to oppose the adjacent grooves of each other. The diameter of the grooves gradually increases from the inner side to the outer side and the pressure plate and the shield plate are isolated when the inner pressure level of the outer container exceeds a predetermined electric current isolation pressure.
A safety device as claimed in claim
3
comprises a positive electrode lid attached at one end of an outer container, the positive electrode lid including a pressure plate effected as the innermost lid and electrically connected to a positive electrode of a electrode member through a positive electrode lead, a shield plate effected as an intermediate lid and electrically connected to the pressure plate through a central contacting portion, and a sealing plate affected as the outermost lid and electrically connected to the shield lid, wherein at least one gas flow hole is provided at the pressure plate so as to communicate the internal space of said outer container with a contacting space between the pressure plate and the shield plate. The central contacting portion includes a protrusion protruded from a central portion of the pressure plate toward the shield plate and having a first flat contacting surface and a second contacting surface provided at a central portion of the shield plate and contacting with the first flat contacting surface of said protrusion, a plurality of circular grooves at a portion surrounding with the second flat contacting surface of the shield plate except for connecting tab portions which are coaxially notched and arranged alternatively with an angle of 180° so as to oppose the adjacent grooves of each other. The diameter of said grooves gradually increases from the inner side to the outer side. A valve layer is formed at each circular groove by adhering a metallic foil piece on a the side surface of said shield plate which abuts the pressure plate when the inner pressure level of the outer container exceeds a predetermined electric isolation pressure, the second flat contacting surface of the shield plate is released from the first flat contacting surface of the pressure plate so as to isolate an electric communication between the pressure plate and the shield plate. When the pressure level of the outer container exceeds a predetermined layer break pressure, each valve layer is broken. It is preferable that the shield plate and the metallic foil piece are made of a clad metal pla
Kawamura Hiroaki
Okamoto Hiroaki
Saijyo Kinji
Browdy and Neimark
Kalafut Stephen
Toyo Kohan Co. Ltd.
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