Coated Swaged Fastener Collar for Visual Swaging Verification

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Solution Overview

Problem

Conventional swaged lockbolt fasteners face challenges in distinguishing between unswaged and swaged collars, particularly in large-scale fabrications with numerous fasteners, due to small sacrificial tell-tale formations and inaccessible locations, posing safety risks and quality concerns.

Innovation Solution

A swaged lockbolt fastener with a coated collar featuring a visually distinct indicator material that changes color upon correct swaging, allowing easy identification of properly swaged fasteners by color change, even from a distance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If small sacrificial tell-tale formations are used to indicate swaging, then the swaging status can be indicated, but it becomes difficult to see and check visually

Engineering Contradiction:
Improveswaging status indicationVSAvoidvisual detection difficulty
Core Design Contradiction:
ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies a color-changing indicator material that transitions from an first color (e.g., red) in the unswaged state to a second color (e.g., silver/gray) when swaged. This color change provides clear visual distinction between swaged and unswaged collars, solving the detection difficulty while maintaining reliable status indication.

Inventive Principle:
Principle #32Color changes

Solution Approach 2:

The indicator material undergoes a physical parameter change (color) in response to the swaging process. This parameter change makes the swaging status easily detectable by the human eye, transforming an invisible mechanical process into a visible indicator.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If pressure sensitive material is applied to indicate swaging force, then the force amount can be indicated, but the material remains on the surface making visual checking difficult

Engineering Contradiction:
Improveswaging force indicationVSAvoidvisual checking difficulty
Core Design Contradiction:
ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The indicator material is designed to be removed or consumed during the swaging process. When swaging occurs, the indicator material is stripped away to expose the substrate, providing a clear visual indication. This extraction approach eliminates the remaining material that would otherwise obscure the view.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The indicator material provides color indication that changes or disappears during swaging, allowing visual detection of the swaging status without leaving obstructive residue on the collar surface.

Inventive Principle:
Principle #32Color changes

3Productivity

If numerous fasteners are used in large-scale fabrications, then the assembly complexity increases, but it becomes difficult to check each fastener individually

Engineering Contradiction:
Improveassembly scaleVSAvoidinspection difficulty
Core Design Contradiction:
ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The color-changing indicator material allows for rapid visual inspection of multiple fasteners from a distance. Operators can quickly scan through numerous collars and immediately identify which ones have been properly swaged based on color differences, dramatically improving inspection efficiency in large-scale fabrications.

Inventive Principle:
Principle #32Color changes

Solution Approach 2:

The indicator material automatically provides visual feedback about the swaging status without requiring additional inspection tools or complex procedures. Each collar self-indicates its status through color, enabling operators to inspect many fasteners quickly and easily.

Inventive Principle:
Principle #25Self-service

4Adaptability or versatility

If fasteners are located in inaccessible positions, then the assembly design is flexible, but close checking becomes difficult

Engineering Contradiction:
Improvelocation flexibilityVSAvoidinspection accessibility
Core Design Contradiction:
Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The bright color change provides long-range visual detection capability, allowing operators to inspect fasteners in hard-to-reach locations from a distance. The contrasting colors ensure that even remotely located collars can be visually verified without requiring close physical access.

Inventive Principle:
Principle #32Color changes

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

Enables easy and remote visual verification of correctly swaged fasteners, reducing the need for close examination and ensuring safer, more reliable assembly processes.

Implementation Method 1

US2008/0297343 A1 discloses methods of indicating amounts of applied force to various components including swage fittings by the application of pressure sensitive material which changes colour according to the amount of force applied.

Methodology Applied
Scientific EffectPressure sensitive material color change: Pressure-sensitive Paint

Data Source

PatentEP3953591B1Swaged fasteners
Publication Date: 2026.04.01
  • EP3953591B1 patent drawingFigure 1~4
  • EP3953591B1 patent drawingFigure 5

AI summary

A swaged fastener (10) includes a coated collar (12) for location in use on a pin (14). In an unswaged condition, the coated collar (12) comprises a substrate material (16) having a substrate colour and an indicator material (20) having an indicator colour. The indicator material (20) is located on the substrate material (16). The indicator colour is visually different to the substrate colour. The coated collar (12) includes a swaging surface (18) to which, in use, a swaging force is applied to move the collar (12) from the unswaged condition to a swaged condition. The indicator material (20) comprises at least part of the swaging surface (18) and is arranged so that, in a correctly swaged condition, the indicator material (20) comprising the swaging surface (18) is substantially removed to expose the substrate colour and thereby provide a visual indication that the swaging process has been correctly carried out.