Fall Arrest Safety Device with Linear Energy Absorber
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Solution Overview
Problem
Existing fall arrest systems face challenges in precisely controlling braking force, maintaining reliability over time, and detecting fall events, due to sensitivity to surface conditions and frequent need for inspection and replacement of friction-based brake components.
Innovation Solution
Incorporation of a linear energy absorber that deploys and absorbs energy when a predetermined load is exceeded, providing precise control over braking force and visible indication of fall events, reducing maintenance needs and improving system reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If friction-based brake components are used to control braking force, then the braking force can be adjusted, but the system becomes sensitive to surface conditions and requires frequent inspection and replacement
Solution Approach 1:
The patent replaces the friction-based mechanical brake system with a magnetic particle brake system. The magnetic particle brake uses magnetic fields and magnetic particles to generate braking force, eliminating the sensitivity to surface conditions that plagues friction-based systems. This substitution maintains the ability to control braking force while dramatically improving reliability and reducing maintenance requirements.
Solution Approach 2:
The patent changes the fundamental parameter of braking mechanism from friction-based contact force to magnetic field-based force. By using magnetic particles that can be controlled through magnetic field strength, the system achieves precise braking force control without the wear and surface condition sensitivity inherent in friction-based systems.
2Force
If friction disks are used in the brake system, then braking can be achieved, but the surface properties change over time particularly in dirty environments requiring regular inspection and adjustment
Solution Approach 1:
The patent eliminates friction disks entirely by substituting them with a magnetic particle brake system. This replacement removes the surface property degradation issue that occurs with friction disks in dirty environments, as magnetic particles do not suffer from the same wear and contamination sensitivity.
Solution Approach 2:
The magnetic particle brake system is designed to be self-regulating and self-lubricating, eliminating the need for regular inspection and adjustment. The magnetic particles automatically maintain optimal braking characteristics without human intervention, significantly reducing maintenance requirements.
3Speed
If high braking force is applied to stop a falling user, then the fall can be arrested quickly, but the force applied to the user may become high enough to injure the user or cause damage to the safety harness
Solution Approach 1:
The magnetic particle brake enables continuous and smooth control of braking force through variation of magnetic field strength. This allows the system to apply just enough force to arrest the fall at a controlled rate, avoiding the sudden high-force application that could injure the user while still achieving rapid deceleration from fall speeds.
Solution Approach 2:
The brake system dynamically adjusts braking force during the fall arrest process. It can apply higher force initially to quickly reduce fall speed, then modulate the force to complete the arrest smoothly, optimizing both response time and user safety throughout the entire deceleration process.
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 allows for simpler assembly and reduced maintenance, as well as immediate visual indication of fall events, enhancing user safety and system reliability by absorbing fall energy through a linear energy absorber that is less prone to environmental changes.
Implementation Method 1
The metal strip is plastically deformable and is arranged in a coiled configuration
Implementation Method 2
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
Data Source
Figure 1~2
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Figure 6~7
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.