Crane with boom raising assist structure

A method of setting up a lift crane wherein the lift crane comprises, during operation, a carbody;

• ground engaging members elevating the carbody off the ground;
• a rotating bed rotatably connected to the carbody;
• a boom pivotally mounted at a first end to the rotating bed with a load hoist line extending adjacent a second end of the boom;
• a boom hoist mechanism that can be used to change the angle of the boom relative to the rotating bed during crane operation;
• and a boom raising assist structure;
• the method comprising:
• a) attaching the first end of the boom to the rotating bed and constructing the boom, with the boom extending out from the rotating bed parallel to the ground and being supported by the ground in a first position, and the weight and length of the boom being sufficient to generate a moment that would tip the crane if the crane boom hoist mechanism were to attempt to lift the boom off the ground without using the boom raising assist structure;
• b) positioning the boom raising assist structure between the ground and the boom, with the boom raising assist structure connected to the boom;
• c) using the boom raising assist structure and the boom hoist mechanism together to pivot the boom about its connection to the rotating bed, and raising the boom from the first position to a second position defining a first boom angle, the first boom angle being at least as large as the boom angle needed so that the moment generated by the boom will no longer tip the crane even if the boom raising assist structure were no longer in contact with the ground;
• and
• d) using the boom hoist mechanism to raise the boom to a second angle steeper than the first angle, where the boom raising assist structure is no longer in contact with the ground.

A mobile lift crane comprising:

• a) a carbody;
• b) moveable ground engaging members elevating the carbody off the ground;
• c) a rotating bed rotatably connected to the carbody;
• d) a boom pivotally mounted at a first end to the rotating bed with a load hoist line extending adjacent a second end of the boom;
• e) a boom hoist drum connected to the rotating bed and boom hoist rigging connected between the boom hoist drum and the second end of the boom, the boom hoist drum and rigging being useable to change the angle of the boom relative to the rotating bed;
• and
• f) a boom raising assist structure connected to the boom between the first end of the boom and the center of gravity of the boom comprising two hydraulic cylinders each having a jack pad on a lower end thereof wherein the weight and length of the boom are sufficient to generate a moment that would tip the crane if the crane boom hoist drum and rigging were to attempt to lift the boom off the ground without using the boom raising assist structure.