| 摘要 |
PROBLEM TO BE SOLVED: To improve durability of a serration mechanism by distributing share of load on a center punching surface plate to minimize stress. SOLUTION: A center punching surface plate 63 is pulled out to the forward from a space between a fixed surface plate 61 and an inner side block surface plate 65 constituting a part of a surface plate 9 of this device, and the inner side block surface plate 65 is shifted centerwards in the direction of the fixed surface plate 61. After a metal plate W is carried to a space between the upper surface plate 9 and a lower surface plate 7, the inner side block surface plate 65 is shifted outwards. The center punching surface plate 63, when it is returned to the backward, is engaged through engaging recessed parts 75, 79, 83 and engaging members 77, 81, 85 provided on contact surfaces of the fixed surface plate 61 and the inner side block surface plate 65 which are located on the both sides of the center punching surface plate 63. By cooperative actions of the upper surface plate 9 and the lower surface plate 7, the metal plate W is pressed and fixed, and at the same time the load exerted on the center punching surface plate 63 at the time of bending is distributed on the fixed surface plate 61 and the inner side block surface plate 65 through engaging of the engaging recessed parts 75, 79, 83 and the engaging members 77, 81, 85.
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