LIFT CRANE WITH IMPROVED MOVABLE COUNTERWEIGHT

摘要

A lift crane includes a carbody and movable ground engaging members mounted on the carbody. A rotating bed is rotatably connected to the carbody and includes a counterweight support frame including a rack coupled directly to a lower surface of the rotating bed. A boom is pivotally mounted to the rotating bed. A counterweight unit includes a trolley, the counterweight unit being in a movable relationship with respect to the rotating bed. A counterweight unit movement device is configured to move the counterweight unit toward and away from the boom. Other embodiments include a counterweight support beam movably connected to the rotating bed, the counterweight support beam including another rack coupled to a lower surface of the counterweight support beam. A counterweight support beam movement device is connected between the counterweight support beam and the counterweight support frame.

主权项

1. A lift crane comprising:
a) a carbody; b) movable ground engaging members mounted on the carbody allowing the crane to move over the ground; c) a rotating bed having a front portion and a rear-most fixed portion, the rotating bed being rotatably connected to the carbody about an axis of rotation that provides a plane of rotation perpendicular to the axis, the rotating bed including a counterweight support frame including a rack coupled directly to a lower surface of the counterweight support frame, the rack having teeth formed therein; d) a boom pivotally mounted about a fixed boom hinge point on the front portion of the rotating bed and including a load hoist line for handling a load; e) 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; f) a counterweight unit that includes a trolley, the counterweight unit being supported on the counterweight support frame in a movable relationship with respect to the rotating bed; and g) a counterweight unit movement device configured to move the counterweight unit toward and away from the boom, the counterweight unit movement device including at least one motor driving a gear connected to the trolley, and in which the gear engages the teeth on the rack to move the trolley with respect to the rotating bed as the motor turns the gear.