Deformable Hub Energy Absorption in Self-Retracting Lifelines
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Solution Overview
Problem
Current self-retracting lifeline systems often result in sudden and high stresses during falls due to the sudden locking of the drum rotation, which can cause injury and require additional components or assembly steps for energy absorption, increasing complexity, bulk, and cost.
Innovation Solution
A self-retracting lifeline system with a deformable hub that absorbs energy without additional components or assembly steps, utilizing a polymeric material hub that deforms to absorb kinetic energy upon braking, reducing stresses and system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If friction brake mechanisms or additional energy absorption components are used, then energy absorption capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The energy absorption function is merged with the drum structure by making the drum itself deformable. The drum is designed with a deformable wall that can collapse radially inward to absorb impact energy, eliminating the need for separate energy absorption components while maintaining the drum's primary function of storing and releasing energy during normal operation
Solution Approach 2:
The deformable drum serves multiple functions: it acts as the rotating element for storing and releasing energy during normal lifeline operation, and simultaneously serves as the energy absorption mechanism during fall arrest. This multi-functionality eliminates the need for dedicated energy absorption components, reducing device complexity and manufacturing cost
2Strength
If high-strength materials are used for drum assembly, then strength and reliability are improved, but manufacturing cost increases
Solution Approach 1:
Different regions of the drum are designed with different material properties to match their specific functional requirements. The deformable wall portion uses a material with appropriate deformation characteristics for energy absorption, while other critical components maintain high strength where needed. This localized material optimization reduces overall manufacturing cost while maintaining necessary strength
Solution Approach 2:
The material parameters of the drum wall are specifically selected to enable controlled deformation at impact forces. By changing the material parameters to allow deformation rather than requiring high-strength rigid materials, the system achieves energy absorption capability while reducing manufacturing cost associated with high-strength materials
3Loss of energy
If the drum assembly is designed to deform, then energy absorption is improved and manufacturing cost is reduced, but structural stability during deformation must be maintained
Solution Approach 1:
The drum structure is segmented into different functional zones: a deformable wall portion designed to collapse radially for energy absorption, and a rigid flange portion that maintains structural stability and provides mounting points. This segmentation allows the drum to deform where needed while maintaining overall structural integrity
Solution Approach 2:
The drum may utilize composite material construction combining materials with different properties - one material providing deformability for energy absorption and another providing structural stability. This composite approach enables simultaneous achievement of energy absorption and structural stability during deformation
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
The system provides increased reliability, reduced complexity, and lower costs by effectively absorbing energy during falls, with the deformable hub design reducing peak fall arrest forces and maintaining system functionality post-deformation.
Implementation Method 1
at least a portion of the hub is formed from a deformable material that deforms to absorb energy
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A lifeline system includes a lifeline and a hub around which the lifeline is coiled. The hub deforms to absorb energy at a predetermined level of force exerted thereon by the lifeline. For example, the hub can be deformable to absorb energy so that a peak fall arrest force in a drop test of the lifeline system with a 220 pound mass attached to the lifeline over a distance of up to 6.56 feet is not more than 1900 pounds. In several embodiments, the peak fall arrest force is no more than 1500 pounds or no more than 1349 pounds.