Dual-Phase Shock Absorber for Fall Arrest Energy Management
Solution Overview
Problem
Existing fall arrest lanyards with shock absorbers often fail to provide adequate energy absorption for falls exceeding six feet, leading to severe injuries due to sudden stops and excessive deceleration forces, as they are either under-capacitated or over-capacitated, not meeting regulatory safety standards for varying fall distances.
Innovation Solution
A dual-phase shock absorber design that absorbs energy in two distinct phases, initially providing an arrest force of 900 pounds or less and then increasing to 1800 pounds or less, utilizing high-efficiency energy tear webbing with varying stitching density or adhesive properties to manage energy absorption across different fall distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a Force level I shock absorber with 900 lb arrest force is used, then the deceleration force remains within acceptable levels for six-foot falls, but the shock absorber cannot absorb sufficient energy for falls exceeding six feet, resulting in sudden stops and force spikes above 1800 pounds
Solution Approach 1:
The shock absorber is divided into multiple tear-away stitch rows with different tear strengths, creating distinct energy absorption phases. The first phase uses lower strength stitches (900 lb tear strength) to absorb energy during initial deceleration, while subsequent phases use higher strength stitches (1800 lb tear strength) to absorb additional energy from longer falls, preventing sudden stops
Solution Approach 2:
The patent changes the physical parameter of stitch tear strength along the length of the shock absorber. By varying the stitch density and/or thread strength in different sections, the shock absorber provides different arrest forces at different stages of deployment, enabling it to adapt to varying fall distances while maintaining safe deceleration forces
2Reliability
If a Force level II shock absorber with 1800 lb arrest force is used, then the energy absorption capacity increases to handle falls greater than six feet, but the deceleration force exceeds acceptable levels and may injure workers weighing less than 180 pounds
Solution Approach 1:
The shock absorber is segmented into multiple rows of stitches with progressively increasing tear strengths. This segmentation allows the system to absorb energy in controlled increments, providing 1800 lb of total energy absorption capacity while limiting the peak deceleration force to 900 pounds during the initial phase, thereby protecting lighter workers from excessive forces
Solution Approach 2:
The patent implements parameter changes by varying the stitch tear strength along the shock absorber's length. The first row of stitches has lower tear strength (900 lb) to limit initial deceleration force, while subsequent rows have higher tear strength (1800 lb) to provide additional energy absorption capacity for longer falls, thus resolving the contradiction between energy absorption and force limitation
3Ease of manufacture
If a single-strength shock absorber design is used, then the manufacturing process is simple and consistent, but the device cannot adapt to different fall distances, requiring separate Force level I and Force level II devices
Solution Approach 1:
The patent applies parameter changes by systematically varying the stitch tear strength along the shock absorber's length within a single manufacturing process. This allows one device to provide multiple energy absorption phases (900 lb and 1800 lb capacities) without requiring separate manufacturing lines for different Force levels, thereby achieving both manufacturing consistency and fall distance adaptability
Solution Approach 2:
The multi-phase shock absorber design makes a single device universally applicable to different fall scenarios. By incorporating multiple tear-away stitch rows with different strengths, the shock absorber can function as both a Force level I (900 lb) and Force level II (1800 lb) device depending on the fall distance, eliminating the need for workers to select between different device types
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 dual-phase shock absorber effectively manages energy absorption for both short and extended falls, meeting regulatory standards by providing a safe and robust deceleration process that reduces the risk of injury from excessive force spikes, while maintaining compliance with OSHA requirements.
Implementation Method 1
a strap having a connected area designed to tear by breaking the connective threads to create mechanical hysterisis under load and thereby absorb energy
Data Source
AI summary
The use of a fall arrest lanyard that provides fall arrest forces at least two primary levels is disclosed. One example provides a lanyard with a pair of shock absorbers of different capacities in series. Other examples use a single shock absorber that provides at least two distinct levels of arrest force. Varying the strength of the attachment area that is to be separated to provide the arrest force and by varying the amount of area being separated at one time varies the levels of arrest force.