| 摘要 |
PROBLEM TO BE SOLVED: To improve torsional rigidity of a revolving frame and suppress the mass of the revolving frame.SOLUTION: A revolving frame 30 comprises: at least two facing side plates 31, 31 (vertical plates); a bottom plate 41 connected to at least two side plates 31, 31 at the lower side from the height direction centers of the side plates 31; and a top plate 45 (an upper traverse member) connected to at least two side plates 31, 31 on the upper side from the height direction centers of the side plates 31. The revolving frame 30 also comprises: a lower opening 51 formed on the bottom plate 41 on the rear side from a seating face part 43 (in an area A); and an upper opening 55 formed on the top plate 45 on the rear side from the seating face part 43 (in the area A). The area of the upper opening 55 is equal to or less than 2/3 of the area of the lower opening 51.SELECTED DRAWING: Figure 5 |
