Pull-Type Blind Fastener for Flush Preloaded Installation
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Solution Overview
Problem
Traditional blind fasteners often result in a protruding tip or recesses after installation, requiring additional machining to achieve a flush surface with the workpiece, and are costly and complex to manufacture, especially when considering galvanic corrosion prevention.
Innovation Solution
A pull-type blind fastener comprising a pin, sleeve, collar, and bulb former, where the pin is pulled to deform the bulb former against the workpiece, creating a mechanical lock without the need for both sides of the workpiece to be accessible, and allowing for one-sided installation, thus eliminating the need for further machining and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional blind fasteners are installed, then the fastening function is achieved, but protruding tips or recesses are created requiring additional machining
Solution Approach 1:
The fastener is divided into multiple functional components: a pin with breaking portion for insertion and actuation, a bulb-forming portion for creating the mechanical lock, and a sleeve for receiving the pin. This segmentation allows each component to be optimized for its specific function, enabling flush break without compromising installation simplicity.
Solution Approach 2:
The protruding tip or pintail is completely removed by designing the pin to break flush with the workpiece surface. The breaking portion is specifically designed to separate at the workpiece surface, extracting the problematic protruding element entirely rather than attempting to machine it down.
2Productivity
If traditional blind fasteners are used, then fastening is achieved, but additional machining operations are required to remove protrusions
Solution Approach 1:
The fastener performs its own finishing operation through the breaking mechanism. As the pin is pulled during installation, the breaking portion automatically snaps off at the workpiece surface, eliminating the need for external machining operations. The fastener itself creates the flush surface condition.
Solution Approach 2:
The breaking portion of the pin is designed to be discarded after serving its installation function. This sacrificial element enables the flush break feature while the remaining pin components stay in place to provide the fastening function, separating the installation aid from the permanent fastening structure.
3Reliability
If complex fastener designs are used to prevent galvanic corrosion, then corrosion protection is improved, but manufacturing cost increases
Solution Approach 1:
The fastener components are designed to be made from the same material throughout, eliminating galvanic corrosion concerns that would arise from dissimilar metal contacts. This homogeneous material approach simplifies manufacturing and reduces costs while maintaining reliability.
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 pull-type blind fastener achieves a recess-free, flush installation with enhanced mechanical properties such as shear strength, tensile strength, and residual preload, while being cost-effective and suitable for one-sided installation, reducing the need for additional machining and minimizing galvanic corrosion concerns.
Implementation Method 1
the bulb former is deformed against the workpieces thus locking the fastener in position
Implementation Method 2
As the pin is pulled away from the workpieces, the sleeve is held in place. The pin head is disposed on a blind side and applies force to the bulb former
Data Source
AI summary
A blind pull type fastener includes a pin, a sleeve, a collar, and a bulb-forming portion. The pin includes a head. The pin is pulled so that the head applies force to the bulb-forming portion. The bulb-forming portion is deformed to form a bulb. The collar is deformed into a void of the sleeve. The pin includes locking rings. The collar is deformed to lock with the locking rings.