Shear Pin Load Indicator for Fall Protection
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Solution Overview
Problem
Conventional load indicators for self-retracting lanyards can be inadvertently activated due to rough handling and it is difficult to visually identify the activation status, leading to potential misinterpretation of whether the SRL has been subjected to shock loading.
Innovation Solution
A load indicator design featuring a shear pin and indicator cover that moves between inactivated and activated positions, with the indicator cover covering and uncovering a visible indicator region to clearly signify activation, preventing inadvertent activation and ensuring reliable shock loading detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional load indicator with a link and shear pin is used, then the SRL can detect shock loads, but the load indicator can be inadvertently activated due to rough handling
Solution Approach 1:
The indicator cover is pre-positioned to cover the indicator region before any load occurs. The shear pin is pre-installed to prevent the saddle from moving. This preliminary configuration ensures that accidental movements during rough handling cannot trigger activation, as the shear pin must be sheared by sufficient force first before the saddle can move and uncover the indicator.
Solution Approach 2:
The shear pin acts as an intermediary element between the external force and the saddle. It mediates the force transmission, requiring a threshold force to be sheared before the saddle can move. This intermediary mechanism filters out minor forces from rough handling while allowing genuine shock loads to trigger the indicator.
2Reliability
If a conventional load indicator with a link is used, then the activation status can be detected, but it is difficult to visually identify whether the link has moved from inactivated to activated state
Solution Approach 1:
The indicator region is designed with visible color changes or distinct visual markers that are easily distinguishable. When the saddle moves to uncover the indicator region, the color or visual pattern changes clearly indicate activation status. This makes visual identification straightforward and eliminates ambiguity about whether activation has occurred.
Solution Approach 2:
The indicator system transitions from a subtle positional change of the link to a dimensional change where the indicator cover moves to uncover a previously hidden region. This creates a before/after visual state that is easily distinguishable, transforming a difficult-to-detect movement into an obvious visual change.
3Reliability
If the link slides from inactivated to activated position after exceeding threshold force, then shock load detection is achieved, but the indicator may be activated by forces below the shock load threshold
Solution Approach 1:
The shear pin is pre-configured with a specific shear strength that corresponds to the desired shock load threshold. This preliminary setting ensures that only forces exceeding this threshold can shear the pin and activate the indicator. The threshold is built into the design before deployment, preventing activation by lower forces during rough handling.
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 improved load indicator effectively prevents false activations and provides a clear visual indication of shock loading, ensuring accurate assessment and maintenance of the SRL.
Implementation Method 1
when a force exceeding a predetermined threshold value is applied on the saddle causing the shear pin to shear or break
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A load indicator for use with a fall protection apparatus having a line and a connector for connecting to a user includes a housing having a pass-through opening and a covered indicator region. A shear pin extends across the pass-through opening, and a saddle extends across at least a portion of the pass-through opening and is supported by at least a portion of the shear pin. The saddle is configured for connecting to at least a portion of the connector. The saddle is movable relative to the housing between a first position and a second position when a force exceeding a predetermined threshold value is applied on the saddle causing the shear pin to shear or break. At least a portion of the indicator region is uncovered in the second position of the saddle when the shear pin shears or breaks.