Alkaline dry battery and sealing gasket therefor
In an alkaline dry battery using a polyamide resin sealing gasket that is placed between a battery case and an anode terminal plate without using a stiffening member and seals the battery case in an airtight manner, the sealing gasket includes a first and a second thin wall parts and is formed of polyamide resin, polyhexamethylene dodecanamide.
1. An alkaline dry battery comprising:
an alkaline power generation element comprising a cathode mixture formed into a tubular shape, a separator disposed inside the cathode mixture, the separator being impregnated with an alkaline electrolyte, and a gelled anode mixture filled inside of the separator;
a cylindrical metallic battery case with a closed bottom that contains the alkaline power generation element and serves as both a cathode terminal and a cathode current collector;
a dish-shaped metallic anode terminal plate having a bar-shaped anode current collector fixed vertically thereon in an internal surface thereof, the anode current collector being inserted into the anode mixture of the power generation element; and
a sealing gasket of a polyamide resin disposed between the battery case and the anode terminal plate without using a stiffening member to seal the battery case in an airtight manner;
wherein the sealing gasket formed as an integrated molding product includes
a central boss through which the anode current collector is inserted,
a perimeter part which is disposed between an opening of the battery case and a peripheral part of the anode terminal plate and forms an airtight sealing by stress deformation caused by contact with an inwardly biased portion of the opening of the battery case,
a middle barrier positioned between the boss and the perimeter part,
a safety valve configured by a first thin wall part provided in a circular part between the boss and the middle barrier, and
a stress absorbing part configured by a second thin wall part formed by bending the circular part between the perimeter part and the barrier, and
wherein the sealing gasket is made of a polyamide resin of polyhexamethylene dodecanamide such that, in the absence of the stiffening member, the first thin wall part of the sealing gasket will break, as opposed to the remainder of the sealing gasket deforming, under pressure loading.
2. The alkaline dry battery according to claim 1 , wherein a thickness of the thin wall part is less than or equal to 0.25 mm.
3. The alkaline dry battery according to claim 1 , wherein the stress absorbing part is formed by the thin wall part having a U-shaped cross-sectional shape.
4. The alkaline dry battery according to claim 1 , wherein a total area of the thin wall part is greater than or equal to 5% of a circumferential cross sectional area of the battery.