| 摘要 |
PROBLEM TO BE SOLVED: To provide a swivel frame that can reduce the impact of stress from a center frame against the portion of a beam welded to the center frame and has a welded structure to ensure the load bearing strength of the beam.SOLUTION: In a skirt beam 26 welded posterior to the center of an entire longitudinal length of a center frame 23A, a pair of beam side plates 42 are welded by a vertical weld 41 in an area lower than the center in the height direction of a side 24a of the center frame 23A. A pair of cutout grooves 43 are formed by cutting out the upper portion of the end of each of beam side plates 42 near the side 24a. Between the upper portions of these beam side plates 42, a beam upper plate 44 is integrally provided by welding. From this beam upper plate 44 along each of cutout grooves 43 to the side 24a, a connection plate 45 for cutouts is welded between the pair of beam side plates 42, and the end of the connection plate 45 for cutouts is welded in the center in the height direction of the side 24a by a horizontal weld 46. |
