Abstract: The invention relates to a power arm comprising four faces, two of which being constituted by plates, which arm is mounted for pivotment about an axis and with respect to a structure, and is fitted with the coupling lug of a jack comprising a pivoting axis of said jack and its support, permitting a deflection of said jack which is parallel to the deflection of the arm, said support being constituted by extended portions of the plates.The arm comprises a cross piece of which the length 1 is substantially equal to the spacing between the said extended portions and which is situated between the said extended portions, and transversed by the axis, a threaded end of which cooperates with a nut to hold the cross piece in position between the said extended portions.An application is found in the production of a shovel boom.

Abstract: The invention relates to a power arm made of a bent, welded structure defined by two lateral plates and by an upper plate and a lower plate welded to the lateral plates and comprising a box having an upper cap and a lower base forming a cross piece of width equal to the spacing of the lateral plates, disposed between these plates in the zone of their elbow and welded to said plates. The cap and the case join, forming two angles, along two lines which pass substantially through the neutral axis of each lateral plate. The invention finds particular application in the manufacture of the boom of a hydraulically operated shovel.