Tower crane telescopic jib crab - has stepped rollers for continuous running on rails of different gauge

摘要

The rollers on which the crab runs are stepped to form sections of two different diameters, allowing it to travel continuously over different jib sections where the rails (6, 3) are of a different gauge. To free the narrow gauge rollers and allow the crab to run on the wider gauge ones, the height, at the junction between sections, of the crab can be varied by a ramp, at the end of one of the pairs of rails. The system of stepped rollers allows the crab to move between non-aligned rails of adjacent sections, without danger of becoming loose.