Patent ID: 7520713
Filing Date: 2009-04-21
Classification: E02F,Y10T

Abstract:
1. A boom assembly bent at the center in a longitudinal direction so as to form a round shape protruding upward when seen from the side, comprising; a front boom sub assembly, said front boom sub assembly constituting the front of the center in the longitudinal direction of said boom assembly; and a rear boom sub assembly, said rear boom sub assembly constituting the rear of the center in the longitudinal direction of said boom assembly, wherein said front boom sub assembly and said rear boom sub assembly are symmetric to each other when seen from the side, and portions from the midway positions in the longitudinal direction of said front boom sub assembly and said rear boom sub assembly to the center in the longitudinal direction of the boom assembly have upper surfaces of arc shape protruding upward when seen from the side, and portions from the middles in the longitudinal direction of said front boom sub assembly and said rear boom sub assembly to ends in the longitudinal direction of the boom assembly have upper surfaces of linear shape when seen from the side.