Jib extension and locking system, for crane with telescopic jib, has latches between jib sections released and re-locked before and after jib length adjustment

摘要

The jib (7) has typically 4 telescoping sections (9-12) e.g. U-shaped in cross-section. When its length is at a minimum these nest inside one another. A hydraulic actuator (19), lying along the jib center line (y-y') extends the jib by moving the sections out telescopically. Optimally, the actuator is of the worm and nut, or chain loop type. The outermost section (9) is pivoted on the chassis, and the innermost (12) carries the hoist cable pulleys (13). The actuator's piston rod (22) rests on a bearing pad (20) at the winch end; its cylinder (19) on rollers (24,25) within the innermost section. Where the rod enters the cylinder the latter is fitted with a cross-head (21) carrying a lateral thruster (50) whose ram (51) can engage in any one of three immobilizing latches (30) fixed to the ends of the inner three jib sections. The cross-head is aligned with the selected latch using a position sensor (60,61). The ram, expelled into a socket on the latch housing, separates a wedge-shaped nose two spring-loaded latch-bolts, freeing them from a notched locking bar (40) fixed on the next outermost section. Bars are fixed at each end of each section and at intermediate points. After the actuator repositions the jib the ram retracts and the latch re-locks to the new bar.