Pawl-Less Wearable Retractable Locking for Fall Arrest Miniaturization
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Solution Overview
Problem
The miniaturization of wearable retractables is limited by the minimum required strength of pawls, which restricts size reduction due to fall arrest forces, making it challenging to further reduce the size and weight of these devices.
Innovation Solution
The solution eliminates traditional pawls by using sperrad teeth on clutch-mounted sperrad plates outside the drum periphery, allowing the drum to rock back and forth to duplicate the pawl's function, engaging a stop member or stop cap within the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If traditional pawls are used for locking mechanism, then locking strength is sufficient to endure fall arrest forces, but device size and weight cannot be reduced below certain minimum
Solution Approach 1:
The patent extracts the pawl component entirely from the system and replaces it with a drum-based locking mechanism. The drum itself performs the locking function by engaging with sperrad teeth on the housing, eliminating the need for separate pawl components and thereby reducing overall device weight and size while maintaining locking capability.
Solution Approach 2:
The drum serves multiple functions: it winds the retractable cord, provides the locking mechanism through its engagement with sperrad teeth, and acts as the primary structural element. This multi-functionality eliminates the need for separate pawl components, reducing device complexity, weight, and size while maintaining fall arrest capability.
2Volume of moving object
If drum size is reduced for miniaturization, then device compactness improves, but locking mechanism strength becomes insufficient to handle fall arrest forces
Solution Approach 1:
Instead of having pawls engage the drum (traditional approach), the patent inverts the engagement relationship: the drum engages fixed sperrad teeth on the housing. This inversion allows the drum to be smaller while maintaining locking strength, as the fixed sperrad teeth provide the structural strength rather than the moving pawls.
Solution Approach 2:
The locking function is merged into the drum-housing engagement system. The drum and sperrad teeth work together as an integrated locking mechanism, where the sperrad teeth on the housing provide the structural strength for fall arrest, allowing the drum to be miniaturized without compromising locking capability.
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
This design enables the creation of smaller, lighter wearable retractables by eliminating the need for traditional pawls, allowing for reduced size and weight while maintaining the necessary locking strength, effectively addressing the size reduction limitations.
Implementation Method 1
The sperrad and drum assembly are rotationally fixed relative to each other by use of a spring loaded clutch mechanism
Implementation Method 2
allowing the drum to rock back and forth in the housing to duplicate the function of a traditional pawl
Data Source
AI summary
A pawl-less retractable comprises an inner frame with a drum-sperrad assembly mounted to the inner frame between side members of the frame to rotate relative to the frame and a stop cap which, during a fall, engages said drum-sperrad assembly to prevent further rotation of said drum. The inner frame can be pivotally mounted to the stop cap such that the inner frame and the drum-sperrad assembly pivot relative to the step cap, or the stop cap can pivot relative to the drum-sperrad assembly. The stop cap comprises a central body, a leading wing extending from a first side of the central body and a trailing wing extending from a second side of the central body opposite said first side. In use, the drum-sperrad assembly and the stop cap pivot relative to each other between an unlocked position in which the teeth of the sperrad are inside of an engagement zone circle and a locked position in which the teeth are outside of the engagement zone circle.