Sealing method for button-type battery

PURPOSE:To perform sealing free of eccentricity by making sealing by placing on an under mold provided with a constraining portion to constrain the side wall of the battery container to the inside end surface and also provided with more than two of upwardly tapered movable clamping pieces a battery container. CONSTITUTION:The upper part of the under mold 1 is provided with more than two horizontally movable clamping pieces 2 and 2' whose outside end surface is provided with the upwardly tapered portions 4 and 4' and whose inside end surface is provided with the constrainig portions 6 and 6' to constrain the side wall of the cylindrical battery container 5. The battery container 5 to be sealed is placed on the under mold 1, the over mold 7 is moved downwards, and the movable clamping piece 2 and 2' are moved inwards by the tapered portions 4 and 4', until the tapered portions 4 and 4' of the movable clamping pieces conincide with the tapered portion 8 of the over mold 7, whereby the side wall 5a of the battery container 5 is constrained by the constraining portions 6 and 6' of the movable clamping pieces. At the same time, the upper end opening 5b of the battery container 5 is folded inwards and sealed by the curved surface 10 of the sealing over mold 9.