Abstract: The present invention relates to a linkage actuator for effecting all rectilinear or rotative movements, acting on the elements (1 and 2) constituting the linkage, characterized in that it acts directly on the linkage axle (3) and in that it is preferably constituted by at least one jack (4) and by chains or cables (5) guided on the one hand on the linkage axle (3) and on the other hand on the pinions or pulleys or grooved wheels (6), the jack (4) coacting with the chains or cables (5) and if desired with the linkage axle (3), which is integral at its ends with one of the elements (1 or 2), the other element (2 or 1) housing the actuator.

Abstract: A crane for material handling is constituted by a boom (1) and a fixed column (2) for supporting the boom (1). The boom (1) is articulated for vertical swinging movement on and relative to a rotating device (3), mounted for rotation about a vertical axis on or in the column (2) and provided with a torsion-transmitting member (4) passing through the column (2) and coacting at its lower portion with a rotation activator (5) of the boom (1). The boom (1) is provided at its free end with a hook, a grapple or another tool, or with a like rotatable actuator.