Blind Fastener Pull Region Geometry for Lower Installation Force
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Solution Overview
Problem
Existing blind fasteners often fail due to fatigue stresses and geometric variations in the bore, requiring high installation forces that can lead to tool damage and operator ergonomic issues.
Innovation Solution
A blind fastener design comprising a sleeve and mandrel with a specific configuration, where the mandrel has an enlarged portion and a pull region of limited axial length, allowing for reduced installation forces and secure engagement without fracturing, using a tool to deform the sleeve and swage it onto the mandrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional blind fasteners are installed using high forces to ensure secure fastening, then the fastening reliability is improved, but the installation tool durability and operator ergonomics deteriorate
Solution Approach 1:
The patent changes the geometric parameters of the mandrel, specifically limiting the pull region axial length to no greater than 4 times the shank region diameter. This parameter optimization allows the fastener to achieve secure fastening with reduced installation forces, directly resolving the contradiction between fastening reliability and installation force requirements
Solution Approach 2:
The mandrel features localized geometric variations including an enlarged portion at the first end and a specifically dimensioned pull region at the second end. These local quality changes enable different functional zones that distribute stresses more effectively, allowing reliable fastening without requiring excessive installation forces throughout the entire fastener
2Ease of operation
If the mandrel pull region is made longer to improve tool engagement, then the ease of operation is improved, but the risk of mandrel fracturing during installation increases
Solution Approach 1:
The patent establishes a specific parameter relationship where the pull region axial length is limited to no greater than 4 times the shank region diameter. This optimized parameter balance provides sufficient tool engagement for ease of operation while maintaining mandrel strength to prevent fracturing during installation
Solution Approach 2:
The mandrel is segmented into distinct functional regions: an enlarged portion at the first end, a shank region in the intermediate portion, and a pull region at the second end. This segmentation allows each region to perform its specific function optimally - the enlarged portion aids insertion, the shank provides structural strength, and the pull region enables controlled tool engagement without compromising overall mandrel strength
3Adaptability or versatility
If conventional fastener designs are used to accommodate bore geometric variations, then the adaptability is improved, but the fastener failure rate due to fatigue stresses increases
Solution Approach 1:
The mandrel incorporates localized geometric features including an enlarged portion and a specifically dimensioned pull region that create stress distribution zones. These local quality variations allow the fastener to adapt to bore geometric variations while preventing fatigue failure by avoiding stress concentration in critical areas
Solution Approach 2:
The optimized parameter of the pull region axial length (no greater than 4 times the shank region diameter) creates a balanced stress distribution that accommodates bore variations without creating fatigue-prone stress concentrations, thereby improving both adaptability and durability simultaneously
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 reduces installation forces, enhances corrosion resistance, and enables lighter, longer-lasting tools with improved ergonomics by securely fastening without fracturing the mandrel, thus reducing material costs and tool damage.
Implementation Method 1
The portion of the sleeve on a first side of the structure is deformed
Implementation Method 2
the second sleeve end is swaged onto the shank region of the mandrel on an oppositely disposed second side of the structure
Data Source
AI summary
The present disclosure relates to a blind fastener and a method of installation thereof. The blind fastener comprises a sleeve and a mandrel. The sleeve comprises a first sleeve end, a second sleeve end, and a cavity extending from the first sleeve end to the second sleeve end. The mandrel is configured to be at least partially received by the cavity of the sleeve. The mandrel comprises a first mandrel end disposed adjacent to the first sleeve end and comprising an enlarged portion having a diameter greater than a diameter of the cavity, a second mandrel end comprising a pull region, and a shank region extending intermediate the first mandrel end and the second mandrel end. The pull region comprises an axial length no greater than four times a diameter of the shank region and is configured to be engaged by an installation tool.