Abstract: Disclosed is a crane comprising: a lower body; an upper slewing body; a counterweight unit including a plurality of wheels to travel on the ground in a turning direction equal to a slewing direction of the upper slewing body while being suspended from the upper slewing body; a steering actuator for rotating each of the wheels around a steering-rotation center axis to change the steering angle; and a steering control device for controlling the steering actuator. The steering control device includes: a slewing-identification-signal receiving section which receives a slewing identification signal for identification of the slewing direction of the upper slewing body; and an actuator operating section operates the steering actuator to orient each of the wheels to the inside of a tangent line to an orbit of the wheel at the steering-rotation center axis, based on the identified slewing direction identified from the slewing identification signal.

Abstract: At an inner circumference side of a lower ring and an upper ring, flange pars are formed respectively, and a ring-shaped clamp device is arranged at the inner circumference side, and separated at four points, into a front side, back side, left side, and right side, and divided into four divided clamps. At the separation points of front and back sides, the left and right divided clamps are rotatably connected with each other, and at the separation points of left and right sides, the front and back divided clamps are connected to cylinders respectively. By the extension/contraction operation, the front and back clamps move between joint and separation positions, and if the front and back clamps position at the joint points, predetermined spaces are formed between the divided clamps. Lock blocks to be inserted into the spaces for regulating return of the divided clamps to the separation positions are provided.

Abstract: At an inner circumference side of a lower ring and an upper ring, flange pars are formed respectively, and a ring-shaped clamp device is arranged at the inner circumference side, and separated at four points, into a front side, back side, left side, and right side, and divided into four divided clamps. At the separation points of front and back sides, the left and right divided clamps are rotatably connected with each other, and at the separation points of left and right sides, the front and back divided clamps are connected to cylinders respectively. By the extension/contraction operation, the front and back clamps move between joint and separation positions, and if the front and back clamps position at the joint points, predetermined spaces are formed between the divided clamps. Lock blocks to be inserted into the spaces for regulating return of the divided clamps to the separation positions are provided.

Abstract: A hydraulic drive system for counterweight dolly in a counterbalance type crane, including dolly driving wheels supported vertically movably through wheel supporting hydraulic cylinders at the lower portion of the counterweight dolly which is connected to the rear portion of a crane body; a wheel driving hydraulic motor connected to each of the wheels; a support pressure detecting mechanism for detecting a support pressure for each wheel supporting hydraulic cylinder, the support pressure detecting mechanism being provided in a drive circuit for the cylinder; and a mechanism for controlling the driving pressure for the wheel driving hydraulic motor in accordance with a detected value provided from the detecting mechanism.

Abstract: A hydraulic drive system for a counterweight dolly in a counterbalance type crane having a crane body provided with a lower travelling structure an upper swivelling structure and the counterweight dolly connected to the rear portion of the upper swivelling structure through a connecting member, characterized by including a swivelling hydraulic motor for swivelling the upper swivelling structure of the crane body; a swivelling control valve for controlling the pressure of hydraulic oil to be fed to the swivelling hydraulic motor; a hydraulic circuit for swivelling operation which controls the amount of operation of the swivelling control valve; a hydraulic motor for the counterweight dolly which drives each wheel of the dolly; a dolly control valve for controlling the pressure of hydraulic oil to be fed to the hydraulic motor for the counterweight dolly; and a control circuit for actuating the dolly control valve in accordance with an operational pressure of the hydraulic circuit for swivelling operation and t