Patent ID: 7802815

Claim:
A working machine including a main frame structure, an upper frame structure, the upper frame structure being slewable relative to the main frame structure about a substantially upright axis, the main frame structure including a main frame part provided by a cast central portion and four connecting arms which extend outwardly of the central portion towards two monolithic cast track sub-frames at the sides of the machine, wherein the central portion of the main frame part is a casting, and the four connecting arms are ends of two fabricated elements which are attached to the central portion, wherein each track sub-frame includes inner and outer track sub-frame members arranged generally side by side with cross members between and spacing the inner and outer track sub-frame members of each track sub-frame apart, wherein the inner and outer sub-frame members and the cross members of each track sub-frame are of a weldable material, wherein the inner track sub-frame members each include a plurality of integrally provided formations which extend inwardly towards the central portion of the main frame part, and wherein the fabricated elements of the main frame part are welded to the inwardly extending formations to attach the central portion to the track sub-frames.