Toyo Kohan Co., Ltd.

Kinji Saijyo

Hiroaki Okamoto

Hiroaki Kawamura

A safety device for a closed battery capable positively preventing a rupture due to a rapid internal pressure rise at over-packing and short-circuiting and being produced inexpensively, a positive electrode lid ( ) attached to one end of an outer covering can ( ) comprises a pressure receiving plate ( ) forming the innermost lid and connected to positive electrode ( ) of an electrode unit ( ) via positive electrode lead ( ), a shielding plate ( ) forming a middle lid and electrically connected to the pressure receiving plate ( ) via a center contact ( ), and a sealing plate ( ) forming the outermost lid and electrically connected to the shielding plate ( ). The center contact ( ) is formed of a projection ( ) having a first flat contact surface ( ) of the pressure receiving plate ( ) and a second flat contact surface ( ) of the shielding plate ( ), and a plurality of annular grooves ( ) are alternately provided around the second flat contact surface ( ) so as to face each other at 180&deg; intervals, the annular grooves ( ) being covered with a metal foil ( ) to form valve membranes ( ).

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Yamaguchi-ken, Japan

Kinji Saijyo