Slewing crane telescoping crab jib - has jib head beam retractable into jib head guide, both being of box shaped cross=section

摘要

The telescopable crab jib for tower slewing cranes comprises a jib base guide (40) and a jib head beam (41) each of box shaped cross-section and each having a track (21, 22) for a traversable crab. The jib base guide and the jib head beam to the extent to which they form the appropriate portion of the crab track, each comprise an identical pair of angle sections (33 or 38). Both pairs of angle sections form a common continuous crab track (200) in flush alignment when the jib is extended. A box section is arranged above each pair of angle sections and in order to obtain the retracted state of the crab jib the angle section pair of the jib head beam and associated box section (34 - 37) of smaller size are retractable into the jib base guide having an angle section pair (33) and associated box section (26) of larger size.