Stud and Grommet Assembly for Low Insertion, High Extraction Force
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Solution Overview
Problem
Stud and grommet assemblies with interference bumps require high insertion forces due to radial flexing of the grommet and have low retraction forces, leading to inefficiencies in installation and removal processes.
Innovation Solution
The use of stud and grommet assemblies with panel retention fingers and stud retention fingers instead of interference bumps, allowing for lower insertion effort and higher extraction force, with the grommet and stud designed as a unitary body for enhanced repeatability and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If interference bumps are used on the grommet, then the grommet can be secured to the panel, but high insertion forces are required due to radial flexing of the grommet
Solution Approach 1:
The grommet is segmented into multiple panel retention fingers and stud retention fingers that can independently flex and engage. This segmentation allows the retention function to be distributed across multiple flexible elements rather than requiring the entire grommet body to flex radially, thereby reducing insertion force while maintaining retention strength.
Solution Approach 2:
The retention fingers are designed to be dynamically flexible during insertion and extraction, allowing them to bend and conform to the panel and stud head surfaces. This dynamic flexibility reduces the force required for insertion while providing strong engagement during operation.
2Strength
If interference bumps are used on the grommet, then the grommet can retain the stud, but low retraction forces are available because the bumps only engage the backside of the stud head
Solution Approach 1:
Instead of having the grommet bumps engage the backside of the stud head (pushing forward), the stud retention fingers engage the underside surface of the stud head (pulling backward). This inversion of the engagement direction provides extraction force in the same direction as the retention force, significantly increasing the available extraction force.
3Strength
If the grommet must flex radially inward to allow bumps to move past the panel flange, then the bumps can engage the panel, but high insertion forces are required
Solution Approach 1:
The grommet is divided into multiple discrete retention fingers that can flex independently as the grommet is inserted into the panel. This segmentation eliminates the need for the entire grommet body to flex radially inward, reducing installation effort while maintaining the retention function.
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
This design reduces installation effort and increases extraction force, providing a more efficient and reliable attachment and detachment mechanism for vehicle components, improving the overall performance and robustness of the assembly.
Implementation Method 1
The panel retention fingers are configured to flex radially inward toward the outer surface of the tubular body when the tubular body is inserted into the hole in the panel. The panel retention fingers are configured to flex radially outward away from the tubular body and engage a bottom surface of the panel
Implementation Method 2
The stud retention fingers are configured to flex radially outward toward the inner surface of the tubular body when a head of the stud is inserted into the hole in the grommet. The stud retention fingers are configured to flex radially inward away from the tubular body and engage an underside surface of the head of the stud
Implementation Method 3
The stud retention fingers have ramped surfaces at distal ends thereof
Data Source
AI summary
A grommet is configured to be fixed within a hole in a panel and to receive a stud to couple the stud to the panel. The grommet includes a hollow body having an inner surface and an outer surface, a flange disposed at one end of the hollow body, panel retention fingers protruding from the outer surface of the hollow body, and stud retention fingers protruding from the inner surface of the hollow body. The panel retention fingers are configured to engage a bottom surface of the panel when the grommet is fully inserted into the hole in the panel. The stud retention fingers are configured to engage an underside surface of the head of the stud when the stud is fully inserted into the hole in the grommet.