Stepped Pin and Grommet Assembly for Seal Clearance
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Solution Overview
Problem
Existing pin and grommet fastener assemblies face issues with clearance between rigid components and integral seal portions, leading to potential damage and reduced sealing effectiveness during assembly and disassembly.
Innovation Solution
A pin and grommet fastener assembly with a stepped shaft design, where the diameter reduces from a larger first diameter to a smaller second diameter, incorporating a ratcheting feature and a flexible seal integrated with the grommet, fabricated using different materials, to minimize interference and enhance sealing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid fastener assembly with a seal is used, then structural integrity is improved, but clearance between rigid components and seal is reduced leading to potential damage
Solution Approach 1:
The fastener shaft is segmented into multiple portions with different diameters (first shaft portion with larger diameter, second shaft portion with smaller diameter). This segmentation allows the larger diameter portion to provide structural strength while the smaller diameter portion creates clearance space to prevent interference with the seal during assembly and disassembly operations.
2Reliability
If a flexible seal integrated with grommet is used, then sealing capability is improved, but interference from rigid components during assembly increases
Solution Approach 1:
Different portions of the fastener assembly have different local qualities - the shaft has varying diameters along its length, with the first shaft portion having a larger diameter for structural support and the second shaft portion having a smaller diameter to provide clearance. This local quality variation allows the rigid components to maintain strength where needed while creating clearance space to protect the flexible seal from interference during assembly operations.
Data Source
AI summary
Disclosed is a pin and grommet (P&G) fastener assembly for forming a connection between a first component and a second component. The P&G fastener assembly includes a grommet and a fastener that provide a step reduction in diameter toward the leading end of their respective parts. The grommet includes a collar and a body to couple with the second component via an opening therein. The body includes a first body portion and a second body portion having a diameter that is less than that of the first body portion. The first body portion includes one or more retention wings to engage the second component via the opening. The second body portion includes one or more pawls to engage the fastener via a ratcheting feature formed in or on the second shaft portion. The fastener includes a head portion and a shank portion extending therefrom. The fastener retains the first component relative to the second component via the grommet. The shank portion defines a shaft includes a first shaft portion having a first diameter and a second shaft portion having a second diameter that is less than the first diameter.