Patent ID: 8528755

Claim:
A mobile crane comprising: a lower propelling body; an upper slewing body slewably mounted on the lower propelling body; a boom attached to the upper slewing body pivotably with respect to the upper slewing body; a mast disposed rearward of the boom and adapted to be raised and lowered so as to raise and lower the boom; a counterweight disposed at the rear of the upper slewing body and adapted to be hung from the mast through a guy line; a counterweight-lifting cylinder attached to the counterweight so as to be extended to vertically push up the counterweight while receiving a reaction force from a ground surface, the counterweight-lifting cylinder having a cylinder body surrounding an internal space thereof, a piston provided within the cylinder body so as to partition the internal space into an upper head-side cylinder chamber and a lower rod-side cylinder chamber, and a rod extending from the piston downwardly beyond a lower end of the cylinder body, the counterweight-lifting cylinder being adapted to be extended by supply of a hydraulic pressure into the head-side cylinder chamber and to be retracted by supply of a hydraulic pressure into the rod-side cylinder chamber; a pressure detection sensor operable to output a detection signal indicative on an internal pressure of the head-side cylinder chamber of the counterweight-lifting cylinder; and a controller operable to set a rated load, based on the detection signal from the pressure detection sensor.