Patent ID: 8511489
Filing Date: 2013-08-20
Classification: B66C

Abstract:
1. A mobile lift crane comprising: a) a carbody having moveable ground engaging members; b) a rotating bed rotatably connected about an axis of rotation to the carbody such that the rotating bed can swing with respect to the ground engaging members; c) a boom pivotally mounted on a front portion of the rotating bed; d) a mast mounted at its first end on the rotating bed; e) a moveable counterweight unit; and f) a counterweight movement structure connected between the rotating bed and the counterweight unit such that the counterweight unit may be moved to and held at both a forward position and a rearward position; g) wherein the crane has a total amount of counterweight of at least 250 metric tonne and a maximum rated load moment of at least 6,250 tonne-meters, and the ratio of maximum rated load moment to total weight of the counterweight is at least 25 tonne-meters/tonne; and h) wherein the moveable ground engaging members comprise crawlers, and the counterweight movement structure is configured such that the counterweight unit is capable of being moved close to the axis of rotation such that the center of gravity of the counterweight unit is in front of the rear end of the crawlers.