DEVICE AND METHOD FOR OVERHANGING/HOUSING JIB OF CRANE

摘要

PROBLEM TO BE SOLVED: To provide a device for overhanging and housing a jib of a crane of excellent safety at overhanging and housing work of the jib. SOLUTION: This device is provided with a jib derricking telescopic stop valve 32 for returning pressure of a hydraulic fluid in a jib derricking operation line and a jib telescopic operation line by operating a relief valve 41. The relief valve 41 is provided on the hydraulic fluid pump P1 side between the jib derricking operation line communicated to a jib telescopic cylinder 14 through a jib derricking directional control valve 33 and the jib telescopic operation line communicated to a jib telescopic cylinder 15 through a jib telescopic directional control valve 34. The jib derricking telescopic stop valve 32 operates the relief valve 41 when signals from a turning pin insertion detector 21 and a securing pin insertion detector 22 show that a securing pin and a turning pin are not inserted while signals of a jib derricking operation detector 23 and a jib telescopic operation detector 24 show that a jib is operated to be derricked or telescopically operated. Derricking telescopic motion of the jib is thereby prevented even though the jib derricking directional control valve 33 and the jib telescopic directional control valve 34 are operated.