External Lewis
From Wikipedia, the free encyclopedia
The External Lewis , Kerb Lifter or Slab Lifter is a type of lifting device used in the Stonemasonry trade since Medieval times. Originally shaped like a pair of scissor-tongs, and swung from a treadwheel crane, the External Lewis has been modified to handle kerbstones and large slabs of polished stone in contemporary stone yards.
A Kerb Lifter is a large, adjustable pair of tongs, made with a pair of handles so that two men can manouevre heavy blocks of stone into position. Kerb lifters are also made to fit mechanical lifters like forklifts or crane-trucks so that larger stones can be placed.
In stone yards, a Slab Lifter is hung from a shed gantry or forklift to transport slabs of stone between storage racks and stone processing machines. It consists of two hinged, weighted friction pads that close astride the top of a slab, and are pulled tightly together by the weight of the slab itself.
This lifting appliance has a safety locking device that is engaged after the gripping pads are activated by the weight of the stone. The locking device ensures that the slab is not released by any jerky movement, and is easily disengaged after the slab is secured in its new location. Another safety feature is the support bracket and safety chain, allowing safe lifting of large slabs to multi-storey buildings[1].
