Self-Threading Blind Fastener for High-Preload Structural Joints
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Solution Overview
Problem
Current high-strength blind fasteners for aerospace applications are costly and lack the necessary preload and stiffness to effectively carry structural loads, limiting their use in automated manufacturing of aerospace components.
Innovation Solution
A self-forming thread blind fastener comprising a sleeve and a pin, where the pin's threaded portion forms threads on the sleeve's inner wall upon rotation, axially compressing and deforming the sleeve to create a bulb, providing high preload and stiffness while being cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If current high-strength blind fasteners are used, then structural load carrying capability is improved, but cost increases significantly
Solution Approach 1:
The fastener system performs self-threading where the pin automatically forms threads in the sleeve during installation through rotational motion. The sleeve deforms and forms its own bulb expansion within the bore to create the locking mechanism, eliminating the need for pre-tapped holes or separate threading operations. This self-service approach reduces manufacturing complexity and cost while maintaining structural load carrying capability.
Solution Approach 2:
The sleeve is pre-configured with a specific geometry including a bulb portion that will expand into the bore. The pin is pre-configured with threading features that will automatically form threads in the sleeve during installation. These preliminary configurations enable the fastener to achieve high strength connections through the installation process itself, without requiring additional manufacturing steps or expensive pre-processing of the workpiece.
2Productivity
If automated production is implemented, then productivity increases, but manufacturing precision requirements increase
Solution Approach 1:
The fastener design incorporates specific geometric parameters including the bulb portion configuration, thread pitch, and material hardness ratios between pin and sleeve. These parameter choices are optimized to provide self-aligning and self-adjusting characteristics during installation, reducing sensitivity to dimensional variations and making the process more tolerant of normal manufacturing tolerances while remaining suitable for automated application.
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 self-forming thread blind fastener offers a cost-effective alternative to traditional fasteners with enhanced preload and stiffness, suitable for structural panels, effectively carrying structural loads and providing airtight seals.
Implementation Method 1
forcibly contacting the at least partially threaded portion of the shank of the pin with the inner wall of the sleeve, thereby deforming the inner wall and forming threads thereon
Implementation Method 2
axially compress and deform the elongate portion of the sleeve and form the threads on the at least a portion of the inner wall of the sleeve
Implementation Method 3
deforming the elongate portion of the sleeve to form a bulb thereon
Data Source
AI summary
Self-forming thread blind fasteners and methods for fastening are provided. The self-forming thread blind fastener comprises a sleeve and a pin. The sleeve comprises a first sleeve end, a second sleeve end, an elongate portion, and an inner wall defining a bore. The pin is configured to be at least partially received by the bore. The pin comprises a first pin end, a second pin end, a pin head portion, an at least partially threaded portion, a shank intermediate, and a driving portion. The at least partially threaded portion is configured to form threads on at least a portion of the inner wall of the sleeve. The driving portion is configured to receive a torque to rotate the pin within the sleeve and thereby axially compress and deform the sleeve and form the threads on the at least a portion of the inner wall of the sleeve.