Patent ID: 8550266
Filing Date: 2013-10-08
Classification: B66C

Abstract:
1. A hoisting device comprising a mobile slewing carriage constrained to move around a geographically fixed axis of revolution, a geographically stationary counterweight lying on said axis of revolution, a tension column, capable of withstanding substantial axial compression, connected to the counterweight and extending upward from said counterweight along said axis of revolution, a swivel joint connecting the counterweight to the tension column, which permits the tension column to deviate slightly from vertical, a back mast extending from said slewing carriage to the tension column, the back mast being connected to the slewing carriage at one end and to the tension column at its other end, and a main boom pivotally connected to the slewing carriage and extending from the slewing carriage in a direction away from said tension column, wherein both the main boom and the back mast are joined to the slewing carriage by hinges, each said hinge comprising a hinge pin supporting both the back mast and the main boom, and a spherical bearing affixed to the slewing carriage and supporting the hinge pin.