Hitachi Construction Machinery Co., Ltd.

Hironao Ishikawa

Kouhei Urase

Shingo Kishimoto

Saori Sawai

An upper boom is constituted by a box member having a shape like a box that includes an upper flange, a lower flange, a left web and a right web, and bosses that are welded to both ends of the box member. Bent plate portions which are bent inward are provided at both ends of the left web, and bent plate portions are also provided at both ends of the right web. Reinforcement plates are positioned at an outside of the bent plate portions and welded between the left web and the boss, and reinforcement plates are also welded between the right web and the boss at an outside of the bent plate portions. With these bent plate portions and the reinforcement plates, a double structure can be provided in the vicinities of the bosses, and these portions can be reinforced.

Front device

A left fore leg () is formed to shape by a casting means, integrating an inner joint portion (A), an outer joint portion (B) and an intermediate tubular portion (C) into an unitary tubular structure. In this case, a joining end (A) of the inner joint portion (A) as well as an outer joining end (B) of the outer joint portion (B) is in the form of an open end of a rectangular shape. Accordingly, it becomes possible to cut the production cost of truck frame () and to form a longer welding bead around the outer periphery of the respective inner and outer joining ends (A) and (B) to enhance the joint strength between the inner joint portion (A) and a center frame () as well as the joint strength between the outer joint portion (B) and a side frame ().

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Tsukuba, Japan

Hironao Ishikawa