Arm for construction machine with upper ends of rear plate protruding upward

摘要

An arm of a hydraulic excavator is formed as a box-shaped structural body surrounded by left and right side plates, an upper plate, a lower plate, and a thick rear plate. An upper end of the thick rear plate is protruded upward from an outer surface of the upper plate. Upper ends of a pair of arm cylinder brackets joined to an outer surface of the thick rear plate are arranged higher than the outer surface of the rear thick upper plate and lower than the upper end of the thick rear plate. As a result, in each of the arm cylinder brackets, a joint area with the thick rear plate can be ensured large, and joint strength can be improved.

主权项

1. An arm for a construction machine formed as a box-shaped structural body having a square cross sectional surface having left and right side plates, an upper plate joined to upper end sides of said left and right side plates by welding, a lower plate joined to lower end sides of said left and right side plates by welding, and a rear plate joined to rear end sides of said left and right side plates and to a rear end side of said upper plate by welding, comprising:
a boom connecting boss disposed on rear parts of lower sides of said left and right side plates and joined to said left and right side plates and a rear end of said lower plate and a front end of said rear plate by welding; a bucket connecting boss joined to front ends of said left and right side plates, said upper plate, and said lower plate by welding; a pair of left and right arm cylinder brackets joined to an outer surface of said rear plate by welding; and a pair of left and right bucket cylinder brackets joined to an outer surface of the rear end side of said upper plate by welding, wherein said upper plate has a portion that is bent diagonally downward, wherein an upper end of said rear plate protrudes upward from a height position of an outer surface of a rear end edge of the portion of said upper plate; that is bent diagonally downward, wherein upper ends of said pair of arm cylinder brackets are arranged higher than the height position of the outer surface of said rear end edge of the portion of said upper plate that is bent diagonally downward and arranged lower than said upper end of said rear plate, and wherein said pair of left and right bucket cylinder brackets are disposed on a portion of said upper plate that is forward of the portion of said upper plate that is bent diagonally downward.