Pull-Type Blind Fastener with Flush Break and Residual Preload
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Solution Overview
Problem
Existing fasteners, such as rivets and blind fasteners, often result in protrusions or recesses after installation, requiring additional machining to achieve flush surfaces, and are inefficient or costly in terms of materials and installation complexity.
Innovation Solution
A pull-type blind fastener comprising a pin, sleeve, collar, and bulb former, allowing one-sided installation and forming a flush break with the workpiece through deformation of the bulb former against the workpiece, creating a mechanical lock without the need for further machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional blind fasteners are installed, then the fastening function is achieved, but protruding tips, pintails, or recesses are formed on the workpiece surface requiring additional machining
Solution Approach 1:
Instead of the fastener breaking below the surface as in traditional designs, this invention inverts the break location to occur exactly at the surface level. The stem is designed with a controlled break point that aligns with the workpiece surface, causing the fastener to snap off flush without creating protrusions or recesses, thereby eliminating the need for additional machining operations.
Solution Approach 2:
The fastener design incorporates a self-regulating mechanism where the stem breaks at a predetermined point during installation. The break point is engineered to automatically align with the workpiece surface, allowing the fastener to self-correct and achieve flush installation without requiring external machining operations or additional adjustment steps.
2Strength
If traditional fasteners are used, then workpieces are held together, but additional machining operations are required to achieve flush surfaces
Solution Approach 1:
This invention merges two previously separate operations into one: the fastening installation and the surface finishing. By designing the stem to break flush with the workpiece surface during installation, the patent combines the fastening function with the surface preparation function, eliminating the need for separate machining operations and thereby improving productivity without compromising fastening strength.
3Device complexity
If blind fasteners are installed from one side, then installation complexity is reduced, but material deformation must be controlled to achieve flush break
Solution Approach 1:
The stem is pre-designed with a controlled break point and appropriate geometry before installation. The stem includes a narrowed section or stress concentration point that is engineered to break at a specific location. This preliminary design ensures that during one-sided installation, the stem will break precisely at the workpiece surface without requiring complex control mechanisms or adjustment procedures during the installation process.
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 fastener achieves flush installation with the workpiece, reducing the need for additional machining and lowering manufacturing costs while maintaining desirable mechanical properties like shear strength, tensile strength, and residual preload.
Implementation Method 1
the bulb-forming portion is deformed against the workpieces thus locking the fastener in position
Implementation Method 2
The force applied by the sleeve, the bulb-forming portion and the pin during installation of the pull-type blind fastener is retained to mechanically lock the pull-type blind fastener
Data Source
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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.