Coiled Strip Energy Absorber for Consistent Fall Arrest Load
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Solution Overview
Problem
Frictional rotational energy absorbers in fall arrest systems require a higher initial couple to start rotation than to continue, leading to incomplete energy absorption, increased fall distance, and sensitivity to environmental changes and surface properties, resulting in potential injuries and increased system size, weight, and cost.
Innovation Solution
A coiled strip energy absorber that uses plastic deformation to absorb energy, with a predetermined couple for deployment determined by the material properties, ensuring consistent operation and reduced environmental sensitivity, and a controlled stop mechanism to prevent excessive deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If friction pads are used with a preset load to absorb energy through relative rotation, then energy absorption is achieved, but the applied couple required to start rotation is larger than to continue rotation, leading to incomplete energy absorption and increased fall distance
Solution Approach 1:
The invention changes the fundamental parameter of energy absorption mechanism from friction-based to plastic deformation-based. The yield strength of the metal strip provides a constant resistance force throughout deformation, ensuring that the couple required to start and continue rotation remains substantially constant, thereby maintaining maximum safe load throughout the energy absorption process and minimizing fall distance
Solution Approach 2:
The invention replaces the friction-based mechanical system with a plastic deformation-based system. Instead of relying on friction between pads which varies during operation, the invention uses the yield strength of a metal strip which provides consistent resistance, eliminating the problem of varying couple requirements and associated safety issues
2Loss of energy
If friction-based energy absorbers are used, then energy absorption is achieved, but the system requires precise setting of contact load and is sensitive to environmental effects, increasing device complexity
Solution Approach 1:
The invention makes the energy absorption system self-regulating through the material properties of the metal strip. The yield strength of the strip automatically provides the correct resistance force without requiring external setting mechanisms or adjustment of contact loads. The system adapts to environmental conditions through the inherent properties of the metal rather than requiring active control
Solution Approach 2:
The invention extracts and eliminates the complex setting mechanism and spring-based contact load adjustment system from the friction-based design. By using plastic deformation of a metal strip, the system removes the need for precise mechanical settings and environmental compensation mechanisms, simplifying the overall device
3Loss of energy
If friction pads with preset load are used, then energy absorption is achieved, but the contact load changes over time due to environmental effects, reducing reliability
Solution Approach 1:
The invention changes the basis of operation from environmental-sensitive friction properties to environmentally-stable material yield strength. The metal strip's yield strength remains substantially constant under varying environmental conditions, providing reliable and consistent energy absorption performance without the drift and variability inherent in friction-based systems
4Loss of energy
If larger energy absorbing capacity is provided to account for increased fall distance, then complete energy absorption is ensured, but size, weight and cost increase
Solution Approach 1:
The invention changes the energy absorption mechanism to achieve more efficient energy dissipation through plastic deformation. This allows the energy absorber to be more compact and lighter while providing sufficient energy absorption capacity, as the plastic deformation process converts kinetic energy more effectively per unit mass compared to friction-based systems
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 coiled strip energy absorber allows for consistent energy absorption throughout the fall arrest process at the maximum safe load, minimizing fall distance and reducing size, weight, and cost, while being less affected by environmental changes and surface properties.
Implementation Method 1
the elongate member passes the deformer structure and is plastically deformed, so absorbing energy and permitting rotation of the coiler member and the outer member
Data Source
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AI summary
A rotational energy (1) typically for use in a fall arrest system has a coiler (5), a length of plastically deformable strip (4) and a deformer structure (3,3c). The plastically deformable strip has a first end (4a) attached to the coiler (5) and a second free end (4b) and extends past the deformer structure at a position between the first and second ends. Relative rotation of the coiler member and deformer structure (3,3c) causes the strip to be drawn past the deformer structure, plastically deforming the strip and winding the strip coil form about the coiler member.