Cylindrical battery and gasket for use in same

1. A cylindrical battery gasket comprising a battery canister, a gasket for sealing an opening of the battery canister, a ring-shaped positive electrode mixture and a cylindrical separator with a bottom inserted into an inner side of the ring-shaped positive electrode mixture, characterized in that the gasket comprises:

a boss part with a central hole through which a negative-electrode collector is inserted, and a canister-contact part touching an inner side of the opening, upon the battery canister being sealed,

a disk-shaped part extending radially from an outer periphery of the boss part, connecting the boss part to the canister-contact part, and

a bent stress-buffering part being part of the disk-shaped part, and which absorbs the radial distortion of the gasket upon the battery canister being sealed, the stress-buffering part including two or more sharply-angled bent parts, and being nearer a center of the battery than to the positive electrode mixture, upon the battery canister being sealed by the gasket, the two or more sharply-angled bent parts further comprising a first bent part, convexly formed within the battery canister, and a second bent part, concavely formed within the battery canister, which is nearer an outer periphery of the gasket than to the first bent part, the first and second bent parts being connected by a reinforced section, which extends between the first and second bent parts and has a thickness along an entire length thereof in an at rest state that is greater than that of the first bent part nearer the center of the gasket and of the second bent part on the outer periphery of the gasket,

wherein a first section connecting the boss part and the first bent part is slanted downwardly in a direction from the boss part of the gasket towards the outer periphery of the gasket,

the reinforced section extending from the first bent part towards the second bent part is slanted upwardly in a direction from the boss part of the gasket toward the outer periphery of the gasket,

a second section extending from the second bent part and connecting the second bent part and the canister-contact part is slanted downwardly in a direction from the boss part of the gasket to the outer periphery of the gasket, the second section also having an area cross-sectionally tapered that expands towards the outer periphery of the gasket, and

the separator has an upper opening portion which projects inwardly towards a central axis of the battery, with a free end of the upper opening portion contacting the concave side of the second bent part.

2. A cylindrical-battery gasket, according to claim 1 , characterized by the thickness of the reinforced section of the gasket ranging from 1.20 to 2.13 times as much as a lesser value of thicknesses of the first and second bent parts.

3. A cylindrical battery, according to claim 1 , characterized by a shear-inducible ring-shaped thin part connecting the disk-shaped part to a first part of the boss part, with a second part of the boss part being less in diameter than the first part and positioned between the first part of the boss part and the opening of the battery canister, the ring-shaped thin part being located near an unevenness between the first part and the second part, with the ratio of the outer diameter of the first part to that of the second part ranging from 0.63 to 0.90.

4. A cylindrical battery comprising the cylindrical battery gasket of claim 1 .