Patent ID: 7204519

Claim:
A construction machine comprising a lower traveling body having a frame and an upper slewing body which slews freely about the lower traveling body, the frame of the lower traveling body comprising a hollow center frame having an upper plate, a lower plate, and side plates surrounding sides thereof, the upper plate being formed with an attachment ring on which a slewing bearing of the upper slewing body is mounted; a pair of truck frames disposed on outside of two side portions of the center frame; and connecting members for connecting the center frame to the truck frames, center joining portions of the connecting members being welded to the side plates of the center frame, wherein the center frame comprises the side plates positioned so as to jut out from the attachment ring, and reinforcing ribs which connect the upper plate to the lower plate in an interior of the center frame beneath the attachment ring, and the reinforcing ribs expand from the side plates to the interior of the center frame beneath the attachment ring.