Captive Nut Sleeve Interference Fit for Aircraft Tank Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fastener systems for aircraft structures, such as those disclosed in GB-A-2212580, weaken the substructural member and complicate the assembly process due to the use of rivets to hold captive nuts in place.
Innovation Solution
A fastener system utilizing a captive nut with a sleeve that achieves an interference fit within a hole, eliminating the need for rivets by using a metallic sleeve with a cylindrical interface, which allows for quick and easy installation without compromising the structural integrity of the substructural member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rivets are used to hold the captive nut in place, then the captive nut is securely attached to the substructural member, but the substructural member is weakened and the assembly process is complicated
Solution Approach 1:
The invention extracts the rivet from the assembly by using a press-fit sleeve instead. The sleeve is directly pressed into the substructural member to hold the captive nut, eliminating the need for separate rivets and their associated holes that would weaken the structure.
Solution Approach 2:
The invention merges the function of the rivet and the captive nut holder into a single press-fit sleeve component. This sleeve both secures the captive nut and attaches to the substructural member through interference fit, reducing the number of parts and assembly steps.
2Reliability
If rivets are used to hold the captive nut, then the captive nut is securely attached, but the assembly process is complicated
Solution Approach 1:
The invention removes the rivet installation step from the assembly process. The press-fit sleeve is installed in a single operation using hydraulic pressure, eliminating the need for separate riveting operations and reducing overall assembly complexity.
Solution Approach 2:
The sleeve is pre-formed with the exact interference fit dimensions needed for the substructural member. This preliminary preparation allows for direct press-fit installation without requiring complex assembly procedures or multiple adjustment steps.
3Productivity
If an interference fit is used for the sleeve in the hole, then the captive nut can be installed quickly and easily, but the sleeve and hole must have precise dimensions
Solution Approach 1:
The invention specifies precise dimensional parameters for the sleeve outer diameter and hole inner diameter to create the interference fit. By carefully controlling these parameters, the sleeve creates a secure friction fit that enables quick installation without requiring additional fastening operations.
Solution Approach 2:
The sleeve is made from a material with appropriate mechanical properties that allow it to withstand the interference fit stresses while maintaining dimensional stability. The material selection ensures that the precise dimensions are maintained under load, providing both quick installation and reliable attachment.
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 interference fit provides a secure and efficient method to attach secondary structures to primary structures like aircraft fuel tanks, enhancing assembly speed and reducing the risk of weakening the substructural member, while maintaining structural integrity and allowing for easy installation in various applications beyond aircraft fuel tanks.
Implementation Method 1
a sleeve which is located in a hole with an interference fit between an outer surface of the sleeve and an inner surface of the wall of the hole
Data Source
AI summary
An assembly with an aircraft fuel tank is disclosed having a captive nut with an internal thread, a secondary structure, and a fastener which secures the secondary structure to the fuel tank. The fastener has a shaft which passes through the secondary structure and has an external thread coupled to the internal thread of the captive nut. The fuel tank has a fuel tank element with a hole, and the captive nut has a sleeve which is located in the hole with an interference fit between an outer surface of the sleeve and an inner surface of the wall of the hole.