Thin-Walled Rivetless Fastener for Small-Hole Composite Attachment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nut plates and fasteners face issues such as weak attachment, high labor and cost due to separate coldworking, thick barrel walls requiring larger hole diameters, and limited options for composite structures, particularly in blind portions of airframes, where traditional riveted solutions are problematic.
Innovation Solution
A rivetless fastener system featuring a thin-walled bushing that expands within a hole for secure anchoring, combined with an adhesive for enhanced bonding, and an installation tool that measures forces during installation to ensure proper fastening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick barrel wall is used in traditional nut plates, then the attachment strength is improved, but the hole diameter must be increased which reduces edge distance and structure lifespan
Solution Approach 1:
The patent employs a thin-walled bushing (wall thickness 0.005-0.030 inches) that is expanded within the hole to achieve secure anchoring. This thin-walled structure reduces the required hole diameter and preserves edge distance while maintaining attachment strength through the expansion and adhesive bonding mechanisms.
Solution Approach 2:
The bushing is expanded by approximately 3.5% within the hole, changing its dimensional parameters to create a friction fit and enhance adhesive bond. This parameter change allows the thin-walled structure to achieve the necessary holding power without requiring a larger initial hole diameter.
2Ease of operation
If surface bonded retainers are used, then installation is simplified, but the attachment reliability deteriorates as they tend to fall off
Solution Approach 1:
The patent combines multiple anchoring mechanisms into a single integrated system: the expanded bushing provides mechanical interlocking through friction fit, while adhesive material positioned on the bushing outer surface provides chemical bonding. This combination of mechanical and chemical anchoring methods ensures reliable attachment while maintaining installation simplicity.
3Strength
If traditional riveted nut plates are used in composite structures, then the fastening strength is improved, but the manufacturing cost and complexity increase due to drilling small holes in composites
Solution Approach 1:
The patent extracts the rivet component from the fastening system, creating a rivetless design. The bushing is inserted into the hole and expanded to provide anchoring without requiring rivets, thereby eliminating the need for additional rivet holes in composite structures while maintaining fastening strength.
4Manufacturing precision
If coldworking of bolt hole is done separately from nut plate installation, then the manufacturing precision is improved, but the labor and cost increase
Solution Approach 1:
The patent merges the coldworking process with the nut plate installation process. The bushing expansion during nut plate installation performs the coldworking function, simultaneously preparing the hole and securing the fastener in one operation, thereby improving productivity while maintaining manufacturing precision.
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 system provides robust, reliable, and cost-effective attachment with reduced hole expansion, preserving edge distance and increasing structure lifespan, while the installation tool ensures accurate and efficient installation, reducing maintenance time and improving reliability.
Implementation Method 1
The bushing may be configured to be expanded by about 3.5% within the hole. Expansion of the bushing, in some embodiments, may securely couple the bushing with the hole of the structure via at least friction fit.
Implementation Method 2
an adhesive material positioned on at least one of the first side of the retainer and an outer surface of the bushing. In some embodiments, the adhesive material may be positioned on at least the outer surface of the bushing, and expansion of the bushing enhances a bond between the adhesive material and the hole.
Data Source
AI summary
A fastener for retaining a bolt in a hole in a structure, comprising a bushing integrally formed with and extending from the bottom surface of a retainer, the bushing being dimensioned for insertion into the hole in the structure and having a wall thickness ranging from about 0.005 inches to about 0.030 inches, wherein the bushing is configured to be expanded within the hole, thereby securely coupling the expanded bushing within the hole of the structure and anchoring the retainer to the surface of the structure surrounding the hole. A tool for installing a fastener, comprising a tapered mandrel configured for insertion within a fastener situated within a hole of the structure, a drive mechanism configured to retract the mandrel through the fastener and thereby expand the fastener, and a force sensor configured for measuring a force applied by the drive mechanism to retract the mandrel through the fastener.