Patent ID: 6860395

Claim:
A crane jib which comprises: a main arm installed free to rotate about a support turret, an auxiliary arm articulated at a first end of the main arm, a first double acting hydraulic jack having a cylinder supported on said main arm and a rod which is connected to said auxiliary arm, to control a tilting of said auxiliary arm with relation to said main arm, a counterweight articulated at a second end of said main arm, a second double acting hydraulic jack having a cylinder supported by said main arm and a rod connected to said counterweight, a hydraulic balancing pipe connecting an annular chamber of said first double acting hydraulic jack to an annular chamber of said second double acting hydraulic jack, a control means selectively connecting a full section chamber of one of said first double acting hydraulic jack and said second double acting hydraulic jack to a hydraulic fluid supply source and a full section chamber of the other of said first double acting hydraulic jack and said second double acting hydraulic jack to a hydraulic fluid reservoir, a hydraulic fluid transfer line connecting said hydraulic fluid supply source to said hydraulic balancing pipe, means for controlling hydraulic fluid transfer to said hydraulic balancing pipe, provided on said hydraulic fluid transfer line, first position detection means provided close to the articulated connection between the main arm and the auxiliary arm, for detecting a position of the auxiliary arm with relation to the main arm, second position detection means provided close to the articulated connection between the main arm and the counterweight, for detecting a position of the counterweight with relation to the main arm, and a logic controller connected firstly to said first and second position detection means and secondly to said means for controlling hydraulic fluid transfer, said logic controller activating said means for controlling hydraulic fluid transfer to provide a hydraulic fluid transfer to said hydraulic balancing pipe when said first position detection means detects a pendular position of said auxiliary arm while said second position detection means does not detect a vertical position of the counterweight.