Patent ID: 7766176

Claim:
A mobile lift crane comprising: a) central crane unit having a carbody, moveable ground engaging members and a rotating bed mounted to the carbody with a rotatable connection such that the rotating bed can swing with respect to the ground engaging members; b) a boom unit having a boom support member, a boom pivotally mounted on the boom support member, and at least one moveable ground engaging member mounted on the boom support member so that the weight of the boom is supported by the boom unit moveable ground engaging member, and whereby the boom, boom support member and boom unit moveable ground engaging member all travel together as a single unit; c) a counterweight unit having counterweight on a counterweight support member and moveable ground engaging members mounted on the counterweight support member; and d) rigging connecting the boom and counterweight unit such that a load lifted by the boom can be counterbalanced by the counterweight; e) wherein the boom unit is connected to the central crane unit by a first structural member and the counterweight unit is connected to the central crane unit by a second structural member, wherein both the first and second structural members carry compressive loads and maintain the boom unit, the rotating bed and the counterweight unit in lateral alignment with each other, but allow relative vertical movement between the boom unit, the rotating bed and the counterweight unit, and wherein the crane further comprises a main mast pivotally mounted on the combination of the central crane unit, the boom unit and the first structural member.