Temporary Fastener Cap With Tapered Neck for Surface Protection
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Solution Overview
Problem
Temporary fasteners often damage the exterior surfaces of aircraft skin panels by scratching or gouging due to their squeezing action, which is exacerbated by the brittleness of temporary protective coatings (TPCs) at low temperatures and softness at high temperatures, leading to costly smoothing processes.
Innovation Solution
A hollow, cup-shaped fastener cap with an inwardly tapered neck that minimizes surface contact by fitting over the aligned holes, reducing damage to TPCs and isolating it to a small area around the hole, which can be removed during countersinking, preventing further damage when reattached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temporary fastener squeezes workpieces together to maintain alignment and prevent distortion, then the fastening function is improved, but damage to the exterior surfaces and TPCs worsens
Solution Approach 1:
The patent introduces a cap as an intermediary component between the temporary fastener and the workpiece surface. The cap's tapered neck fits over the fastener's tapered end, allowing the fastener to maintain its squeezing function while the cap's tip contacts only a minimal area of the workpiece surface, thereby mediating between the fastening requirement and surface protection requirement
Solution Approach 2:
The cap is designed with non-uniform geometry where the tip has a minimal contact area with the workpiece surface while the body provides full coverage over the fastener. This local differentiation allows the cap to protect the majority of the surface while permitting localized contact at the tip, resolving the contradiction between overall surface protection and necessary fastening action
2Stability of the object's composition
If a cap fits over the temporary fastener to reduce slippage, then the fastener stability is improved, but protection against TPC damage remains insufficient
Solution Approach 1:
The cap is segmented into distinct functional zones: the body portion that fits over the fastener to provide stability and prevent slippage, and the tapered neck with minimal tip that contacts the workpiece surface. This segmentation allows each portion to independently fulfill its function - the body ensures fastener stability while the minimal tip minimizes surface damage
3Stability of the object's composition
If the cap has a larger contact area with the workpiece, then the fastener is more stable and less prone to slippage, but surface damage to TPCs increases
Solution Approach 1:
The cap utilizes dimensional differentiation by extending the body portion along the fastener axis to provide stability, while the tapered neck reduces the radial dimension at the contact point to minimize surface damage. This dimensional strategy allows the cap to be stable (long body) while causing minimal surface contact (small tip radius)
Data Source
AI summary
A cap for a temporary fastener comprises a hollow, cup-shaped body and an inwardly tapered neck. The hollow body fits over a workpiece-engaging portion of the temporary fastener, and the neck extends from the hollow body. The tapered neck terminates in a hollow tip that is sized and configured to fit over aligned holes in the joined workpieces and to contact a minimal surface area of the outermost workpiece to reduce surface damage to the workpieces such that any damage will be removed when the holes are countersunk in the normal course of assembly.