| 摘要 |
PURPOSE:To raise the manufacturing efficiency of a boom for a back hoe type oil-pressure shovel by combining a flat bottom plate, a tip of a U-shaped cross section, both basal end parts, and an intermediate part obtained by bending a U-shaped linear elemental material having notches leading from a hole to a hole for forming a boss hole on its both sides. CONSTITUTION:A bottom plate 11 formed by bending a flat plate at a given position, a tip part 12 formed into a U-shaped linear shape by press bending, and a basal end part 13 formed by the same method as in the conventional one are provided. On the other hand, an intermediate part 14 is produced by bending a flat plate 14A having a top part 15A, side parts 16A and 17A, and boss holes 19A and notches 20 formed in its sides 16A and 17A by a bending process in such a way as to close the notches 20 with a given curvature. These parts are combined to form a boom. In the bending process of the intermediate part 14, bending stress is absorbed by the notches 20 in order to lessen the concentration of stress. |
