Duplex slewing jib crane - has jibs on body slewing on common axis by ball-type ring

摘要

The two jibs slew about a common vertical axis, and also derrick about horizontal axes. The two cranes are each secured to a slewing body on the common axis, and one at least is screwed to the mounting on the ship by a ball slewing ring. The jib foot pins in each case can be below the slewing ring, both being at the same height. The superstructures can slope inwards at the bottom, and a ladder can be provided inside the mountings, its lower end being fixed to part of the rotary slipring assembly through which the electric power is supplied. The superstructures can be mounted on the column by means of a quadruple slewing ring, or two double slewing rings one above the other, the gear ring for the slewing motion being fixed to the bottom race.