Self-Retractable Lifeline Cable Payout Limiting Mechanism
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Solution Overview
Problem
Existing self-retracting lifelines (SRLs) lack the ability to adapt to variable fall restraint protection, requiring multiple devices for different work environments and potentially causing injury due to sudden stops during falls, as they cannot be physically limited to specific cable payout distances.
Innovation Solution
An active SRL with a pretension assembly that allows users to limit cable payout by winding up a power spring, incorporating a mechanism with aligned plates and an actuator to temporarily mobilize the arbor, enabling the SRL to be pretensioned to a specific length, thereby avoiding the need for active braking in most situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single SRL device with fixed cable length is used, then device simplicity and inventory reduction are improved, but adaptability to variable work environments deteriorates
Solution Approach 1:
The patent implements a dynamic cable length adjustment mechanism where the cable can be repositioned along the reel body to change the effective payout distance. This allows a single SRL device to adapt to different work environments by dynamically adjusting the cable configuration rather than requiring multiple fixed-length devices
Solution Approach 2:
The SRL device is designed to perform multiple functions: it can operate as a standard fall arrest device with full cable extension, or as a fall restraint device with limited cable payout. The ability to reposition the cable along the reel body enables the single device to serve different safety requirements across various work environments
2Reliability
If active fall arrest equipment is used, then life-saving capability is improved, but user comfort and injury risk worsen due to sudden stops
Solution Approach 1:
The patent enables preliminary configuration of cable payout distance by repositioning the cable along the reel body before use. This preliminary action allows the system to be set up as a fall restraint system that prevents the user from reaching hazardous areas, thereby avoiding the need for active fall arrest and its associated sudden stop injuries
Solution Approach 2:
The patent converts the potential harm of active fall arrest (sudden stops causing injury) into benefit by enabling passive fall restraint configuration. By adjusting the cable length to limit payout distance, the system prevents falls before they occur, transforming the harmful abrupt stopping force into a beneficial preventive restraint that maintains user comfort
3Adaptability or versatility
If multiple SRL devices of varying sizes are maintained for different work environments, then adaptability is improved, but cost and inventory complexity worsen
Solution Approach 1:
The patent designs a universal SRL device that can function across multiple work environments by allowing the cable to be repositioned along the reel body. This single multi-functional device replaces the need for maintaining multiple specialized devices of different cable lengths
Solution Approach 2:
The dynamic repositioning capability of the cable along the reel body enables one device to provide the functionality of multiple fixed-length devices. Users can adjust the effective cable length by repositioning it, eliminating the need to stock various sized SRL devices
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
Enables a single SRL device to provide both active fall arrest and passive restraint, reducing the need for multiple devices and minimizing the risk of injury from sudden stops, while allowing for versatile use in various work environments by limiting cable payout to a desired distance.
Implementation Method 1
A cable that is wrapped around a central reel body can pay out through an aperture of the housing and retract back on itself through the use of a power spring
Implementation Method 2
SRLs utilize an active braking system positioned within the housing that can quickly stop the cable from paying out when a particular velocity or G-force is detected
Data Source
AI summary
A self-retractable lifeline (“SRL”) having the combination of an active fall arrest braking system and a passive restraint distance limiting mechanism that allows a user to pretension and preset the distance that its cable is capable of paying out. The SRL's cable limiting mechanism includes a pretension assembly, which may include a pair of aligned plates and an actuator that temporarily mobilizes an arbor when the lever is opened. The arbor is affixed to the SRL housing and to an interior of a power spring that rewinds the cable back into the housing when the cable is paid out. The other end of the arbor is in a mechanical relationship to one of the aligned plates that prohibits rotational movement of the arbor when the aligned plates are engaged but allows rotational movement of the arbor when the aligned plates are temporarily disengaged.