Linear Energy Absorber for Fall Arrest Braking Force Control
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Solution Overview
Problem
Existing fall arrest systems face challenges in precisely controlling braking force, maintaining reliability in dirty environments, and providing indication of fall events, leading to potential injuries and frequent component replacement due to wear and sensitivity to surface conditions.
Innovation Solution
Incorporating a linear energy absorber that responds to a predetermined load threshold by deploying and moving the safety device vertically, allowing precise control of braking force and providing a visible indication of fall events, while reducing the need for frequent inspection and replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a friction brake is used to control braking force, then the braking force can be adjusted, but the brake becomes highly sensitive to surface conditions and requires frequent inspection and adjustment
Solution Approach 1:
The patent replaces the friction-based mechanical braking system with a linear energy absorber that uses controlled deformation of a steel strip. The energy absorber deploys a pre-formed steel strip that deforms plastically to absorb fall energy, eliminating the need for friction surfaces that are sensitive to dirt and wear. This substitution of mechanical friction with controlled material deformation resolves the reliability issue in dirty environments.
Solution Approach 2:
The patent changes the fundamental parameter of energy absorption from friction-based force multiplication to controlled plastic deformation. The linear energy absorber uses a steel strip that deforms permanently in a controlled manner to absorb energy, changing the physical mechanism from friction (which is sensitive to surface conditions) to plastic deformation (which is more stable). This parameter change eliminates the need for frequent adjustment and maintenance.
2Speed
If the braking force is increased to stop falls faster, then the fall arrest time is reduced, but the force applied to the user may injure them or damage the safety harness
Solution Approach 1:
The patent incorporates a linear energy absorber that is pre-configured to deploy and deform in a controlled manner during a fall. The steel strip is pre-formed and positioned to engage at a specific load threshold, providing beforehand cushioning that limits the peak force transmitted to the user. This prior cushioning mechanism ensures that even during rapid deceleration, the force remains within safe limits, resolving the contradiction between fast arrest and user safety.
Solution Approach 2:
The patent changes the energy absorption mechanism from high-force friction braking to controlled plastic deformation. The linear energy absorber deforms the steel strip plastically, which provides a more gradual and controlled energy absorption profile. This parameter change in the energy absorption mechanism allows for faster fall arrest while limiting peak forces to safe levels, protecting both the user and the safety harness.
3Force
If the braking force is precisely controlled, then the fall arrest performance is optimized, but the assembly and adjustment of the brake becomes complex and difficult
Solution Approach 1:
The patent replaces the complex friction brake assembly with a simpler linear energy absorber mechanism. Instead of requiring precise adjustment of friction surfaces, loading mechanisms, and clutch engagement, the energy absorber uses a pre-formed steel strip that deploys at a predetermined load threshold. This substitution eliminates the complex assembly and adjustment procedures while providing consistent and reliable force control.
Solution Approach 2:
The linear energy absorber uses a disposable steel strip that is pre-formed and cannot be adjusted or tuned after assembly. The strip is designed to deform permanently in a controlled manner during a fall, and after use, the entire energy absorber can be replaced as a single unit. This approach eliminates the need for complex assembly and adjustment procedures, making the device easier to manufacture and deploy while maintaining precise force control characteristics.
4Power
If the friction brake surfaces are loaded heavily to absorb more energy, then the brake can handle larger falls, but the surface conditions and degree of loading become difficult to set and maintain
Solution Approach 1:
The patent replaces the friction-based energy absorption system with a linear energy absorber that uses controlled plastic deformation of a steel strip. The energy absorption capacity is determined by the geometry and material properties of the steel strip, which are set during manufacturing. This substitution eliminates the need for precise field adjustment of loading conditions, as the energy absorption characteristics are built into the strip's physical design rather than requiring precise mechanical assembly.
Solution Approach 2:
The patent changes the energy absorption mechanism from friction (which requires precise control of normal force and coefficient of friction) to plastic deformation (which is governed by material yield strength and geometric parameters). The linear energy absorber uses a steel strip with specific dimensions and material properties that are manufactured with tight tolerances, providing consistent energy absorption capacity without requiring complex assembly adjustment. This parameter change in the fundamental energy absorption mechanism resolves the manufacturing precision issue.
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 solution enables precise control of braking force, reduces maintenance needs, and provides a clear visual indication of fall events, enhancing safety and reliability in fall arrest systems.
Implementation Method 1
The linear energy absorber is of the type which absorbs energy by deforming a steel strip
Implementation Method 2
The brake 8 comprises a pair of opposed friction discs 8a and 8b loaded into contact with one another
Data Source
AI summary
A safety device for a fall arrest system comprises: a body, attachment means for attaching the safety device to a support structure, a drum mounted for rotation relative to the body, a safety line wound on the drum, a speed sensitive clutch connected to the drum, and a linear energy absorber connecting the body to the attachment means, in which the speed sensitive clutch is adapted to respond to rotation of the drum relative to the body in a direction tending to unwind the safety line from the drum and above a predetermined speed by locking the drum against further rotation in said direction relative to the body, and the linear energy absorber is adapted to respond, when the speed sensitive clutch has locked the drum, to an applied load along the safety line greater than a threshold value by deploying and absorbing energy so that the attachment means moves away from the body.