Arrow of the crane has reach variable, with a device for automatic balancing

摘要

The invention provides a system for automatically balancing the jib of cranes of the type with articulated arms or telescopic arms depending on the variation of the reach of this jib. The annular section chambers of the hydraulic cylinder controlling the auxiliary arm of the crane and of the hydraulic cylinder controlling the pivoting arm carrying the counterweight are connected in series by a duct. The full section chambers of the hydraulic cylinders are connected selectively, by actuation of a valve, either to the pressure line or to the return line. In the right-hand position of the valve, the counterweight is pivoted and the arm is raised simultaneously, whereas in the opposite position of the valve the arm is lowered and the counterweight is raised.