Self-Leveling Bottom Block Assembly for Crane Hoists
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Solution Overview
Problem
Conventional overhead lift cranes with single rope support configurations risk uncontrolled load movement if a rope breaks, and solutions using four ropes increase hoist drum size and weight, necessitating a need for a single failure-proof, self-leveling bottom block assembly with reduced size and weight.
Innovation Solution
A bottom block assembly with a central vertical axis, a hook, and two pairs of equally spaced sheaves, where one rope supports the block if the other fails, ensuring the load remains level, utilizing a configuration where one rope crosses over the other, reducing the number of ropes needed while maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four ropes are used to support the bottom block, then the bottom block remains level even with a full load attached to the hook, but a larger hoist drum is required which increases the trolley spread and the overall weight of the trolley hoist assembly
Solution Approach 1:
The invention divides the support system into two independent rope systems, each capable of supporting the full load independently. Each rope is reeved through its own pair of sheaves, creating separate support paths that can function independently, thus achieving single failure proof capability with fewer ropes
Solution Approach 2:
The invention uses a vertical stacking arrangement of sheave pairs at different heights on the bottom block, creating a three-dimensional configuration. The first pair of sheaves is positioned higher than the second pair, allowing ropes to cross between levels and reducing the horizontal spread required
2Reliability
If four ropes are used to support the bottom block, then the bottom block remains level even with a full load attached to the hook, but a larger hoist drum is required which increases the trolley spread
Solution Approach 1:
The invention uses a vertical stacking arrangement of sheave pairs at different heights on the bottom block, creating a three-dimensional configuration. The first pair of sheaves is positioned higher than the second pair, allowing ropes to cross between levels and reducing the horizontal spread required
Solution Approach 2:
The invention combines multiple rope functions into fewer ropes by having each rope serve dual purposes: supporting the block and maintaining levelness through the crossed configuration. The crossing arrangement allows each rope to contribute to both vertical support and horizontal balance
Data Source
AI summary
A bottom block assembly includes 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, a first rope reeved about the first pair of sheaves, a second pair of sheaves rotatably attached to the block, and a second rope reeved about the second pair of reeves. The first and second pairs of sheaves are each equally spaced about the central vertical axis. The first pair of sheaves are located higher on the block than the second pair of sheave so that a portion of the first rope located between the first pair of sheaves crosses over a portion of the second rope located between the second pair of sheaves. If either rope fails, the other rope ensures the block remains level with a full load attached to the hook.