Patent ID: 6868671

Claim:
A hydraulic circuit for a crane comprising: a first actuator group including actuator circuits driven by a first hydraulic source, said actuator circuits including a boom hoisting motor circuit as a driving circuit for a winch motor for boom hoisting and a wind-up motor circuit as a driving circuit for a winch motor for wind-up, said boom hoisting motor circuit and said wind-up motor circuit being selectively connected in series through a control valve for boom hoisting and a control valve for wind-up; a second actuator group including actuator circuits driven by a second hydraulic source; and a switching valve provided between said control valve for boom hoisting and said control valve for wind-up in said first actuator group, wherein said switching valve is capable of being switched between a first position and a second position, wherein both said boom hoisting motor circuit and said wind-up motor circuit are connected to said first hydraulic source at the first position of said switching valve, and wherein at the second position of said switching valve, said boom hoisting motor circuit and said wind-up motor circuit are cut off from one another and a downstream one of said boom hoisting motor circuit and said wind-up motor circuit is connected to said second hydraulic source via said switching valve.