| 摘要 |
PURPOSE:To reduce the friction between a groove forming punch and a part where a groove is formed of the bottom and to lengthen the life of the groove forming by specifying the groove forming angle of the punch, and forming a groove in the bottom of a battery container in a free state by press work. CONSTITUTION:A groove forming punch 21 is lowered and a groove forming projection 21a of the punch 21 is pressed to the bottom 2 of a battery container 1 to form a groove 3. The tip 21a1 of the projection 21a is formed in a flat state and the bottom of the groove 3 is also formed in a falt state. The groove forming angle theta of the projection 21a is 50-80 deg.. The tensile stress f is applied to the groove forming part of the bottom 2 pressed with the tip 21a1 of the projection 21a and the part where no groove is formed is free from the pressure. The groove forming part of the bottom 2 is easy to be deformed, and the resistance to deformation in this part and the friction between the projection 21a and the part where the groove is formed are reduced. |
