Insert Nut Flange Diameter Ratio to Prevent Jack-Up
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Solution Overview
Problem
Existing insert nuts used in screw fastening applications often experience issues with being jacked up from substrates or screws loosening due to differences in flange diameters, leading to extraction forces exceeding the fixing force, resulting in defects such as insert nut extraction and screw loosening.
Innovation Solution
An insert nut design with a flange diameter that is at least 2.4 times the nominal diameter of the screw, featuring knurled portions and a counterbore to enhance resin engagement and prevent rotation with the screw, along with a manufacturing process using progressive pressing to optimize dimensions and reduce material waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the flange diameter of the insert nut is made smaller than the head diameter of the screw, then the fastening force is enhanced, but the insert nut is jacked up from the substrate during fastening and the screw is loosened
Solution Approach 1:
The patent applies asymmetry by making the flange diameter of the insert nut larger than the head diameter of the screw, creating an intentional dimensional asymmetry that reverses the conventional design. This asymmetric configuration ensures that the screw head cannot contact the substrate directly, preventing the jack-up phenomenon and maintaining fastening stability throughout the tightening process and during use.
2Reliability
If the flange diameter of the insert nut is made larger to prevent jack-up, then fastening stability is improved, but the difference in flange diameters causes extraction force to pull out the insert nut from the substrate
Solution Approach 1:
The patent applies parameter changes by establishing a specific dimensional relationship where the flange diameter is 1.1 to 1.5 times the screw head diameter. This quantitative parameter optimization balances two opposing requirements: it is large enough to prevent jack-up and ensure stability, yet controlled to minimize the lever arm that generates extraction force, thereby preventing insert nut pull-out from the substrate.
3Force
If a flanged screw is used to enhance fastening force, then the screw can securely clamp the member, but the insert nut is jacked up from the substrate or the screw is loosened along with use
Solution Approach 1:
The patent applies preliminary action by pre-configuring the insert nut with a flange diameter larger than the screw head diameter before assembly. This preliminary dimensional configuration ensures that during the fastening operation, the screw head contacts only the insert nut flange, preventing direct contact between the screw head and substrate that would cause jack-up, thereby maintaining fastening system integrity throughout repeated use.
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 design effectively suppresses defects like jack-up and loosening, ensuring secure fastening and reduced material costs through improved torque distribution and enhanced resin engagement, while maintaining a balanced flange diameter ratio for optimal performance.
Implementation Method 1
a recess-and-protrusion-shaped portion formed on an outer surface of the insert nut, the recess-and-protrusion-shaped portion including a plurality of ridges and a plurality of roots formed alternately in a circumferential direction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An insert nut (1), which is configured to be inserted into a substrate made of a resin (55), the insert nut (1) including: an internal thread portion (5) into which a screw is to be fastened; a recess-and-protrusion-shaped portion (6,11) formed on an outer surface of the insert nut (1), the recess-and-protrusion-shaped portion (6,11) including a plurality of ridges (6a,11a) and a plurality of roots (6b,11b) formed alternately in a circumferential direction; and a flange portion (3) formed on one end side in a screw axial direction of the internal thread portion (5), wherein a nominal diameter of the screw to be fastened into the insert nut (1) is 3 mm or more, and an outer diameter of the flange portion (3) is 2.4 times or more and 4 times or less as large as the nominal diameter of the screw to be fastened into the insert nut (1).