Jib crane system having a rotatable mast

摘要

A jib crane system comprising a horizontally extending load beam rigidly attached to the upper end of a vertically extending mast. The lower of the mast extends inside a hollow pipe and is rotatably associated with a base plate assembly or rotatably secured in the foundation at the site of the crane. Roller bearings are rigidly secured to the mast and positioned in frictional contact with the pipe. The roller bearing revolves around the circumference of the pipe as the mast and load beam rotate around the central axis of the mast. The roller bearings are adjustable for varying the frictional contact of the rollers with the pipe.