Captive Fastener Retaining Ring Groove Design
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Solution Overview
Problem
Captive panel fasteners in the aerospace industry face issues with maintaining proper positioning, as they tend to recess into or out of panels, which can lead to instability and improper securing of aircraft panels.
Innovation Solution
A captive panel fastener design featuring multiple retaining elements, including a cylindrical member with longitudinally extending grooves, a retaining ring with radially inwardly extending prongs, and spring-loaded pins, which work together to securely hold the fastener in place within the panel bore, preventing movement and ensuring proper positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single retaining element is used to hold the fastener, then the device complexity is reduced, but the reliability of preventing fastener movement deteriorates
Solution Approach 1:
The retaining system is divided into multiple independent retaining elements (retaining ring with first and second retaining features, plus additional retaining elements) that work together to secure the fastener. Each retaining element provides independent support, and the segmentation allows the system to maintain reliability even if one element fails or is insufficient alone.
Solution Approach 2:
The patent employs multiple retaining elements as a form of redundancy before failure can occur. By having backup retaining features (such as the retaining ring with multiple retaining features and additional retaining elements), the system compensates for potential weaknesses in any single element, ensuring reliable fastener positioning under various loading conditions.
2Reliability
If multiple retaining elements are added to prevent fastener movement, then the reliability of fastener positioning is improved, but the device complexity increases
Solution Approach 1:
Multiple retaining functions are merged into a single integrated retaining ring component. The retaining ring incorporates both the first retaining feature (radially inwardly extending portion) and the second retaining feature (longitudinally extending groove), combining what could have been separate components into one unified element that provides multiple retaining mechanisms simultaneously.
Solution Approach 2:
The retaining ring serves multiple functions: it provides the first retaining feature to prevent fastener movement in one direction, the second retaining feature (groove) to prevent movement in another direction, and also acts as a structural support element. This multi-functionality reduces the need for additional specialized components.
3Reliability
If the retaining ring prongs are made more flexible to grip the grooves, then the retaining capability is improved, but the structural strength of the retaining ring deteriorates
Solution Approach 1:
The retaining ring exhibits local quality by having different mechanical properties in different regions. The radially inwardly extending prongs are designed with local flexibility to provide gripping action on the cylindrical member, while the main body of the retaining ring maintains higher structural strength. This localized variation in stiffness allows the prongs to deform and grip without compromising the overall structural integrity of the ring.
Solution Approach 2:
The retaining ring incorporates dynamic characteristics through the flexibility of its prongs, allowing them to deform elastically under load to enhance gripping capability. This dynamic response enables the prongs to adapt to manufacturing tolerances and maintain consistent gripping force, while the ring's overall structure remains sufficiently rigid to withstand operational loads.
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 design effectively prevents the fastener from recessing into or out of the panel, ensuring stable and secure attachment of aircraft panels, enhancing the reliability and safety of the fastening system.
Implementation Method 1
at least one spring loaded pin positioned internally within the cylindrical member
Implementation Method 2
the second end portion of the cylindrical member being flared to form a flared portion of the second end portion of the cylindrical member
Data Source
AI summary
Captive panel fasteners are configured to be held captive on a panel by multiple retaining elements. The fasteners include longitudinal grooves along a cylindrical portion of the fastener, a retaining ring over the cylindrical portion, a primary structure for retaining the retaining ring on the cylindrical portion, and secondary structure for retaining the cylindrical portion within a bore of the panel. The retaining ring includes radially inwardly extending opposing prongs that fit into the longitudinally extending grooves. A stop point may be provided in the longitudinally extending grooves, or an end of the fastener may be flared, to retain the retaining ring on the fastener. The prongs may also be slightly flexible and flared to grip the longitudinally extending grooves. The secondary structure can include one or more spring loaded pins in the fastener extending externally outward.