FLAT BATTERY

1 . A flat battery, comprising:

a bottomed cylindrical exterior can having a cylindrical side wall extending in a cylinder axial direction;

a bottomed cylindrical seal can having a peripheral wall extending in the cylinder axial direction and covering an opening of the exterior can such that the peripheral wall is located inside the exterior can; and

a gasket formed by injection molding on the peripheral wall of the seal can and sandwiched between the exterior can and the seal can,

wherein the gasket includes:

a covering portion molded on the peripheral wall so as to cover at least a portion of the peripheral wall of the seal can; and

a protruding portion formed integrally with the covering portion and displaced from the peripheral wall in the cylinder axial direction, and

the protruding portion has an injection portion formed to correspond to an injection port of a mold used for injection molding of the gasket.

2 . The flat battery according to claim 1 , wherein:

a portion of the covering portion that is located adjacent the exterior can is sandwiched between the cylindrical side wall of the exterior can and the peripheral wall of the seal can, and

the injection portion is located on a portion of the protruding portion that faces the cylindrical side wall of the exterior can.

3 . The flat battery according to claim 2 , wherein the injection portion has a recess formed on a surface of the protruding portion.

4 . The flat battery according to claim 1 , wherein the protruding portion has a length measured in the cylinder axial direction that is larger than a size of the protruding portion measured in a thickness direction.

5 . The flat battery according to claim 4 , wherein the peripheral wall of the seal can extends in the cylinder axial direction with its edge portion not being folded back.

6 . The flat battery according to claim 4 , wherein the protruding portion has a protrusion length measured in the cylinder axial direction that is larger than a thickness of the protruding portion measured at its edge.

7 . The flat battery according to claim 4 , wherein the protruding portion has a protrusion length measured in the cylinder axial direction that is ¼ or more of a length of the gasket measured in the cylinder axial direction.

8 . The flat battery according to claim 4 , wherein the gasket is tapered in shape such that a thickness of a portion of the covering portion that covers an outer side of the peripheral wall of the seal can gradually decreases toward an edge of the peripheral wall.

9 . The flat battery according to claim 4 , wherein:

the exterior can and the seal can are bottomed and cylindrical in shape, and

the cylindrical side wall of the exterior can has an outer diameter that is smaller than four times a height of the exterior can and seal can as joined together measured in the cylinder axial direction.

10 . The flat battery according to claim 9 , wherein the cylindrical side wall of the exterior can has an outer diameter that is not more than twice the height of the exterior can and seal can as joined together measured in the cylinder axial direction.

11 . A method of manufacturing a flat battery, comprising:

a seal can forming step for forming a bottomed cylindrical seal can; and

a gasket molding step for injection-molding a gasket on a peripheral wall of the seal can using a mold, the gasket having a covering portion covering the peripheral wall of the seal can and a protruding portion protruding from the covering portion,

wherein, in the gasket molding step, the gasket is molded by injecting resin into an area of the mold that is used to form the protruding portion during injection molding.