| 摘要 |
A swivel frame structure for a hydraulic excavator, said swing frame structure being to be arranged in a swing upperstructure 21, has a center frame 1 composed of side plates 6,7 and a reinforcement plate 8 joined to each other. The swing frame structure is provided with mating portions for bringing the side plates 6,7 and the reinforcement plate 8 into engagement with each other. These mating portions comprise plug-in structure portions, which in turn comprise holes 6a,7a formed through the respective side plates 6,7 and lugs 8a,8b arranged on opposite side edge portions of the reinforcement plate 8 and to be inserted into the holes 6a,7a of the corresponding side plates 6,7. The center frame can be fabricated without needing any jigs for fixedly holding the side plates and a bottom plate together.
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