Patent ID: 7963579
Filing Date: 2011-06-21
Classification: B66C,B66D

Abstract:
1. A bottom block assembly for a crane, said bottom block assembly comprising, in combination: a block having a central vertical axis; a hook secured to the block for attaching a load to the block; a first pair of sheaves rotatably attached to the block; wherein rotational axes of the first pair of sheaves are parallel and spaced apart about the central vertical axis; a first rope reeved about the first pair of sheaves; a second pair of sheaves rotatably attached to the block; wherein rotational axes of the second pair of sheaves are parallel and spaced apart about the central vertical axis; a second rope reeved about the second pair of sheaves; and wherein if either the first rope or the second rope fails, the other of the first rope and the second rope ensures that the block remains level with a full load attached to the hook.