Nested Sheave Belt Block and Tackle for Twisted Geometries
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Solution Overview
Problem
Flat belts in block and tackle systems are sensitive to sheave misalignment and limited in their ability to accommodate twisted geometries, leading to premature failure and reduced service life compared to wire ropes, and they require specific twist ratios to maintain service life, which restricts the complexity and flexibility of sheave arrangements.
Innovation Solution
The system employs nested and split sheaves of varying diameters and configurations, including out-of-plane sheaves and support plates, to achieve high reduction ratios while maintaining the advantages of belt-driven systems, allowing for more flexible form factors and increased mechanical advantage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flat belts are used in block and tackle systems, then the system achieves lightweight construction and low maintenance, but the belts experience premature failure when subjected to sheave misalignment or twisted geometries
Solution Approach 1:
The patent employs nested sheaves where smaller sheaves are positioned within the diameter of larger sheaves, creating a compact arrangement that reduces the overall twist ratio requirements. The belt path is configured to pass around multiple nested sheaves in sequence, allowing the system to achieve high mechanical advantage while maintaining acceptable belt bend radii and reducing misalignment sensitivity.
Solution Approach 2:
The patent transitions from a planar sheave arrangement to a three-dimensional nested configuration. By stacking sheaves in multiple layers with varying diameters and positioning them at different radial distances from the center, the system achieves complex belt paths that minimize twist accumulation and reduce the impact of misalignment on belt service life.
2Productivity
If nested sheaves of varying diameters are used, then the system achieves high reduction ratios and flexible form factors, but the device complexity increases
Solution Approach 1:
The patent utilizes nested sheaves where smaller sheaves are positioned within the diameter of larger sheaves, creating a compact arrangement that reduces the overall twist ratio requirements. The belt path is configured to pass around multiple nested sheaves in sequence, allowing the system to achieve high mechanical advantage while maintaining acceptable belt bend radii and reducing misalignment sensitivity.
Solution Approach 2:
The support plate serves multiple functions: it provides structural support for mounting sheaves, defines the geometric relationship between nested sheaves, maintains proper spacing to control belt bend radii, and anchors the belt at the central point. This multi-functionality reduces the need for additional separate components, thereby managing complexity.
3Force
If the belt is configured to extend around multiple nested sheaves, then the mechanical advantage is increased, but the belt wear increases due to repeated bending
Solution Approach 1:
The patent varies the diameter of sheaves in the nested arrangement, with larger diameters positioned where the belt experiences higher bending stresses. This local variation in sheave size optimizes the belt bend radius at critical locations, reducing stress concentration and extending belt service life while maintaining high mechanical advantage through the overall nested configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration minimizes belt wear, increases flexibility, and allows for more complex sheave arrangements, enhancing the mechanical advantage and ease of manufacturing while maintaining the benefits of belt-driven systems over rope or wire-driven systems, thereby extending the service life and reducing the risk of premature failure.
Implementation Method 1
belt driven block and tackle
Implementation Method 2
high reduction block and tackles
Data Source
AI summary
This disclosure describes a belt driven block and tackle system. Traditionally flat belts have many advantages over wire ropes, including maintenance-free operation for an extended service life, a low cost of manufacture, and a reduced physical size in at least one dimension for a given set of working loads. The system includes a block and tackle including first pair of outer sheaves and a first pair of inner sheaves positioned between the first pair of outer sheaves, and a belt extending from a central point, around the first inner pair of sheaves, the first outer pair of sheaves, and out of the block and tackle.