Offset boom type construction machine

Abstract

On the lower surface of a cylinder stay at its fore end portion, a stopper plate is pivotally attached as a safety device for front working equipment by a pin. A rear end portion of the stopper plate is supported to an upper boom to be swung in union with the upper boom. The stopper plate has an outer peripheral configuration having a first curved region which functions as a first stopper, and a second linear region which functions as a second stopper. When a swing angle of the upper boom is within a risky range of possible interference between the bucket and the cab upon the arm being maximally folded, an inner belly portion of the arm strikes against the first region before the occurrence of such interference, whereby further folding of the arm is mechanically limited. When the arm is folded from a condition that the swing angle of the upper boom is within a range in which the bucket and the cab will never interfere with each other and a folding angle of the arm comes within a risky range of possible interference between the bucket and the cab upon the upper boom being further swung laterally toward the cab side, the second region strikes against a side portion of the arm before the occurrence of such interference, whereby further swing of the upper boom is mechanically limited.