Patent ID: 11904374
Assignee: NIPPON STEEL CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 0:
1. A die assembly comprising:
a columnar punch; and
a hollow die configured to receive the punch,
the die assembly being configured to shear a metal sheet placed on the die by moving the punch in a predetermined direction,
the punch comprising a bottom surface and an outer perimeter surface, the bottom surface comprising a cutting edge constituted by an outer perimeter edge of the bottom surface, the outer perimeter surface extending from the outer perimeter edge in a direction parallel to the predetermined direction,
the outer perimeter edge comprising, in plan view, corners, each corner having a curved portion, each curved portion being convexly curved or concavely curved,
the bottom surface comprising a planar portion and cutout portions, each cutout portion recessed with respect to the planar portion in the predetermined direction, each cutout portion including a respective corner with its curved portion in plan view, an apex of the curved portion included in the cutout portion, wherein, in the cutout portion, the outer perimeter edge includes a portion extending in a direction at an angle of 30° or less with respect to the predetermined direction.