Abstract: In vehicle-mounted cranes comprising a hoisting arm consisting of two hingedly interconnected arm sections the outer one of which is equipped with a longitudinally displaceable boom, a bracket removably attachable to the outer end of said boom and to which bracket is hingedly connected a rocker arm with a longitudinally displaceable boom with means thereon to support a load, in addition to which two hingedly interconnected links are provided to likewise connect said bracket with said rocker arm. Locking bolts secure said bracket to the first-mentioned boom, whereby the bracket together with the rocker arm and the boom thereon may be dismounted from the rest of the crane as a unit which may be attached to the crane whenever increased lifting height is required.

Abstract: In hydraulically operated loading cranes, particularly loading cranes comprising multiple loading arms, a blocking device in the form of a return piston arranged, upon occurrence of an excessive pressure in the master cylinder, to prevent operation of piston-and-cylinder units actuating the loading arms in a direction away from the loading crane post but permit operation in the reverse direction, i.e. movement of the loading arms towards the post. The blocking device thus ensures that the moment of loading on the crane arms never reaches a value involving risks that the crane will tip over.