Multiple mast section tower crane

Claim 1

A TOWER CRANE HAVING A TOWER BUILT UP FROM A NUMBER OF SECTIONS ARRANGED END-TO-END AND HAVING A SUPERSTRUCTURE FOR MOUNTING A JIB, WHICH SUPERSTRUCTURE WHEN THE TOWER IS ERECTED, SURROUNDS THE UPPER END OF THE TOWER, MEANS FOR SUPPORTING SAID SUPERSTRUCTURE ON THE UPPER END OF SAID TOWER FOR SLEWING MOVEMENTS, SAID SUPERSTRUCTURE COMPRISING A SUBSTANTIALLY RECTANGULAR CAGE HAVING THREE SIDES OF WHICH TWO OPPOSED SIDES DEFINE A LATERAL OPENING TO PERMIT, DURING ERECTION, THE INTRODUCTION OF THE UPPERMOST TOWER SECTION INTO SAID CAGE AND FURTHER COMPRISING A DETABHABLE FOURTH SIDE FOR PARTLY CLOSING SAID OPENING WHILE LEAVING A REDUCED PART OF SAID OPENING STILL OPEN TO PERMIT INTRODUCTION OF ONE OR MORE FURTHER TOWER SECTIONS ONE AFTER ANOTHER INTO SAID CAGE, GUIDE MEANS CARRIED BY SAID THREE SIDES OF THE SUPERSTRUCTURE CAGE AND THE FOURTH DETACHABLE SIDE, ENABLING THE SUPERSTRUCTURE CAGE, WHEN COMPLETED BY THE ATTACHMENT THERETO OF THE FOURTH SIDE, TO SERVE AS A GUIDE DURING RAISING OF THE UPPERMOST TOWER SECTION, AND TO PERMIT THE SIDEWAYS INTRODUCTION OF THE SAID FURTHER SECTIONS BENEATH THE UPPERMOST TOWER SECTION; AND THE TOWER HAVING POWER OPERATED MEANS INCLUDING A SINGLE DRIVE MOTOR FOR RAISING THE TOWER WITHIN THE SUPERSTRUCTURE, FOR HOISTING THE SUPERSTRUCTURE UP THE TOWER AND FOR IMPARTING SLEWING MOVEMENT TO THE SUPERSTRUCTURE RELATIVE TO THE TOWER.