Temporary Fastener Cap With Tapered Neck to Limit Surface Damage
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Solution Overview
Problem
Temporary fasteners often damage aircraft skin panels by scratching or gouging the exterior surfaces 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 with the workpieces, reducing damage to TPCs and isolating it to a small area around the fastener hole, allowing for easy removal and reattachment without further damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional temporary fastener is used to fasten workpieces, then the workpieces are securely joined together, but the exterior surfaces of the workpieces are scratched, gouged, or damaged
Solution Approach 1:
A cap is introduced as an intermediary component between the temporary fastener and the workpiece exterior surface. The cap includes a body that fits over the fastener and a neck that contacts the workpiece, isolating the damaging squeezing action from the exterior surface while allowing the fastener to perform its fastening function
Solution Approach 2:
The cap is divided into distinct functional segments: a hollow body portion that accommodates the fastener mechanism, a neck portion that contacts the workpiece surface, and a tip portion that fits into the hole. This segmentation allows each part to perform its specific function while protecting the workpiece surface
2Reliability
If a cap is used to fit over the temporary fastener, then slippage of the fastener is reduced, but damage to TPCs is not significantly alleviated
Solution Approach 1:
The cap is designed with varying contact characteristics at different locations: the body provides stable engagement with the fastener, the neck provides localized contact with the workpiece surface, and the tip fits precisely into the hole. This local differentiation allows the cap to provide stability where needed while minimizing surface damage
3Stability of the object's composition
If the cap contacts a large surface area of the workpiece, then stability is improved, but damage to TPCs is exacerbated
Solution Approach 1:
The cap transitions from a simple cylindrical shape to a three-dimensional form with a tapered neck and tip portion that extends into the hole dimension. This dimensional change allows the cap to achieve stability through geometric interlocking rather than through broad surface contact, thereby minimizing TPC damage
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.