Patent ID: 7335439

Claim:
A hermetically sealed battery comprising: an electrode group in which a positive electrode and a negative electrode are wound via a separator; an outside can having an opening for storing said electrode group, said opening being used as a terminal for one of the said electrodes; and an opening sealing unit including a pressure valve for hermetically closing the opening of said outside can by means of an insulation gasket, the said opening sealing unit being used as a terminal for the other electrode, wherein the said opening sealing unit is equipped with a valve chamber for storing said pressure valve, a cap portion in which a flange is constituted, and a bottom plate for closing said opening, wherein an annular Positive Temperature Coefficient (PTC) element is disposed on the upper surface of the flange of the said cap portion, and wherein said PTC element is fixed by a fold portion constituted at the peripheral area of the said bottom plate.