Floating Cage Nut Assembly via Interference Fit and Adhesive Bonding
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Solution Overview
Problem
Existing cage nut assembly methods, particularly in the aeronautical field, face challenges such as weight addition from metallic fasteners, mechanical weakening, complex assembly processes, and compatibility issues with composite structures, along with difficulties in thick structures and rivet availability.
Innovation Solution
A cage nut device with a tubular portion that interferes with the structure's bore for manual assembly, using adhesive for permanent attachment and grooves for improved adhesive distribution, combined with retaining and locking mechanisms to correct misalignments and prevent rotation, offering a lightweight and efficient assembly alternative.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic fasteners (rivets or screw/nut systems) are used to assemble the nut support to the structure, then the assembly is securely fixed, but the total weight of the device increases and additional holes must be drilled in the structure
Solution Approach 1:
The invention extracts the metallic fasteners from the assembly system, eliminating them entirely. The nut support is designed with an integrated mounting flange that directly interfaces with the structure, removing the need for separate rivets or screws and thereby reducing total device weight while maintaining secure fixation.
Solution Approach 2:
The mounting flange is merged with the nut support body, creating an integrated component. This combination eliminates the need for separate fasteners and reduces the number of parts, thereby reducing weight while ensuring reliable assembly fixation through the integrated flange-structure interface.
2Reliability
If metallic fasteners are used to assemble the nut support, then secure fixation is achieved, but the structure is mechanically weakened due to additional drilled holes
Solution Approach 1:
The invention removes the need for drilled holes in the structure by extracting the metallic fastener system. The mounting flange is designed to interface with the structure surface or existing features without requiring additional holes, thereby preserving the structure's mechanical strength and integrity.
3Reliability
If rivets are used to assemble the nut support, then secure fixation is achieved, but the assembly process becomes long and complex requiring specific installation tools
Solution Approach 1:
The invention extracts the rivet system and associated installation tools from the assembly process. The mounting flange is designed for simplified attachment to the structure, eliminating the need for specialized rivet installation equipment and reducing assembly complexity and time.
4Reliability
If rivets are used to assemble the nut support, then fixation is achieved, but the method is problematic for composite structures which do not support crimping
Solution Approach 1:
The invention removes the crimping action associated with rivet installation. The mounting flange is designed to attach to the structure through methods compatible with composite materials, such as bonding or mechanical interlocking that does not involve crimping, thereby enabling use with composite structures.
5Ease of operation
If the tubular portion is designed for interference mounting in the bore, then manual assembly is enabled and adhesive distribution is improved, but the bore diameter must be precisely controlled within a narrow range
Solution Approach 1:
The tubular portion features localized interference zones (such as circumferential ribs or grooves) rather than uniform interference along the entire length. This localized approach enables manual assembly while reducing the sensitivity to bore diameter variations, as the interference is concentrated in specific regions that can accommodate normal manufacturing tolerances.
6Reliability
If longitudinal grooves are added to the tubular portion for improved adhesive distribution, then assembly solidity is increased, but the manufacturing complexity of the tubular portion increases
Solution Approach 1:
The longitudinal grooves create a porous-like structure on the surface of the tubular portion, increasing the surface area for adhesive bonding. This enhanced surface geometry improves adhesive distribution and assembly solidity while the grooves can be efficiently formed through standard manufacturing processes such as injection molding or machining.
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 solution provides a lightweight, solidly fixed cage nut assembly that reduces installation time and maintains structural integrity, overcoming the limitations of traditional rivet-based methods while accommodating thick structures and composite materials.
Implementation Method 1
The tubular portion is then permanently attached to the structure by applying an adhesive to said tubular portion, before assembly
Implementation Method 2
By 'interference mounting' is meant mounting with negative play. This interference mounting is preferably defined so that the nut support can be inserted into the structure manually
Data Source
Figure 1
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Figure 4~5
AI summary
The invention relates to a cage nut device (10), comprising: - a nut (11) comprising a tubular body (12) connected to a collar (15), which is substantially planar and orthogonal to the body, - a nut support (20) comprising a nut cage (23) forming an internal housing (28) able to accommodate the nut, the support also comprising a tubular portion, with the result that the collar of the nut can be inserted into said internal housing, characterized in that an external surface of the tubular portion of the nut support comprises longitudinal splines (22) having a diameter less than the diameter of the bore, and at least two longitudinal ribs (44) having a diameter greater than the diameter of the bore. The invention also relates to a method for installing such a device.