Overhead crane including a single failure proof hoist

Abstract

An overhead crane for use in handling critical loads and including a horizontally movable trolley on which is mounted a single failure proof hoist mechanism having alternative or redundant means for supporting the loads if structural failure occurs in the hoist mechanism. The hoist mechanism comprises a rotatable drum, drive means for rotating the drum, an upper sheave block, and a lower sheave block supporting a hook assembly. A pair of wire ropes, each capable of fully supporting the load, are wound around the drum and the upper and lower sheave blocks and function to suspend the lower sheave block and the hook assembly. The hoist mechanism also comprises an equalizer assembly operably connected to the trolley and supporting the ropes in such a manner as to provide means to compensate for any discrepancies in the lengths of the two ropes. The rotatable drum, drive means, sheave blocks, hook assembly and equalizer assembly each comprise or are associated with alternative or redundant means which operate in the event of structural failure or failure of one of the ropes to provide support for the load. The arrangement of the ropes on the drum and the reeving system function to prevent swinging or rotating motion of the load in the event that one of the ropes breaks or a structural failure occurs. The equalizer assembly also includes shock absorbing means to dampen the effects of impact on the crane in the event that one of the ropes fails or a structural failure occurs.

Dependencies are inferred from the claim text.