| 摘要 |
<p>An overhead crane characterized by its redundant or double-safe features. The crane has two separate ropes with one end of each rope attached to the drum and the other end attached to an equalizer. Each rope, intermediate its opposite ends, is reeved over sheaves in the sheave nest and on the load block in such manner that each rope provides at least four active parts (i.e., load-supporting lines) running to the four horizontal quadrants of the load block with respect to the vertical center line therethrough. With this system and arrangement the load block will be supported by two independent sets having at least four active rope parts or lines of support in each set in such a manner that if a rope breaks or fails for any reason, at least one remaining complete set of at least four active parts provided by the undamaged rope will assume full support with little or no appreciable impact load occurring and with only small and acceptable swinging or twisting movement imparted to the lead. Additional redundancy and double-safety is provided by: constructing the crane hook so it has two separate load paths into the load block; having two complete gear trains between the hoist motor and the drum assembly with each being capable of handling the rated load with a normal factor of safety; having safety lugs to catch the drum hubs in case of shaft failure; having safety retainers for all sheaves in the sheave nest and in the load block to sustain the load upon failure of any sheave or its supporting shaft; and, having the equalizer bar boxed or caged in with load supporting members and provided with bumpers at opposite ends.</p> |
