Patent ID: 8960461
Filing Date: 2015-02-24
Classification: B66C

Abstract:
1. A crane comprising: a lower body; an upper slewing body mounted on the lower body so as to be slewable; a counterweight unit including a plurality of wheels each being rollable on the ground and having a variable steering angle, the counterweight unit being capable of travelling on the ground with respective rolling motions of the wheels, in a turning direction equal to a slewing direction of the upper slewing body, in a state of being suspended from the upper slewing body; a steering actuator adapted to rotate the wheels around a steering-rotation center axis to change the steering angle thereof; and a steering control device for controlling an operation of the steering actuator, the steering control device including a slewing-identification-signal receiving section which receives a slewing identification signal to enable a slewing direction of the upper slewing body to be identified, and an actuator operating section which operates the steering actuator when the upper slewing body is slewed involving the traveling of the counterweight unit in the turning direction, based on an orbit of the counterweight unit, so as to make a line along a traveling direction of the wheels to be inwardly inclined to a tangent line located on the steering-rotation center axis of the wheels, the tangent line being tangent to the orbit of the counterweight unit traveling in the turning direction, based on the slewing direction identified by the slewing identification signal; wherein said wheels travels inside or inwardly of said tangent line around the orbit in a clockwise and counter-clockwise direction.