Patent ID: 7789253

Claim:
A combination crane used for crane operation, comprising: two crawler cranes, each of said crawler cranes respectively comprising a lower propelling body having crawlers, an upper revolving body rotatably mounted on said lower propelling body, a boom whose base section is tiltably supported on said upper revolving body, a tilting mechanism that hoists and lowers said boom, and a hoist mechanism that hoists and lowers a lifting member hung by a hoist rope from a top of said boom; a connecting beam which connects said upper revolving bodies of said two crawler cranes; and means for controlling swinging and propelling of said combination crane by stopping the crawlers of the lower propelling body of one of said two crawler cranes, unlocking the upper revolving body of the one of said two crawler cranes such that the upper revolving body of the one of said two crawler cranes can rotate relative to the lower revolving body of the one of said two crawler cranes, locking the upper revolving body of the other of said two crawler cranes such that the upper revolving body of the other of said two crawler cranes cannot rotate relative to the lower revolving body of the other of said two crawler cranes, and operating the crawlers of the lower propelling body of the other of said two crawler cranes such that the other of the two crawler cranes swings around the one of the two crawler cranes, wherein said connecting beam is rotatably connected to both of said upper revolving bodies of said two crawler cranes so as to rotate around an approximately horizontal axis.