| 摘要 |
A lift crane includes a carbody; moveable ground engaging members; a rotating bed rotatably connected to the carbody, the rotating bed comprising a counterweight support frame; a boom pivotally mounted on the front portion of the rotating bed; a boom hoist system connected to the rotating bed and the boom that allows the angle of the boom relative to the plane of rotation of the rotating bed to be changed; a counterweight unit supported on the counterweight support frame in a moveable relationship with respect to the counterweight support frame; and a counterweight unit movement device connected between the rotating bed and the counterweight unit so as to be able to move the counterweight unit toward and away from the boom. The crane is configured such that during crane operation, the moment generated by the counterweight unit acts on the rotating bed predominantly through the counterweight support frame. Alternatively, the crane can include a mast connected to the rotating bed and a counterweight support beam moveably connected to the rotating bed and a tension member connected between the mast and the counterweight support beam; and a counterweight unit supported on the counterweight support beam in a moveable relationship with respect to the counterweight support beam. In some embodiments the same basic crane is configured to be set-up with two different counterweight options, i) the first option having a counterweight unit directly supported on the counterweight support frame and a counterweight unit movement device connected so as to move the counterweight unit with respect to the counterweight support frame, and ii) the second option having a counterweight support beam moveably connected to the remainder of the rotating bed and a counterweight unit supported on the counterweight support beam, with the counterweight unit movement device connected so as to move the counterweight support beam with respect to the counterweight support frame. |
