NMR Cap Sealing Lip Segmentation
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Solution Overview
Problem
Existing caps for NMR sample tubes often require narrow manufacturing tolerances and apply significant force to the sample tube, risking damage, especially when made of hard materials that are not chemically resistant to NMR solvents.
Innovation Solution
A cap design with a circumferential, elastically deformable sealing lip that maintains a uniform wall thickness, allowing for localized deformation and reduced force distribution, enabling the use of harder, chemically resistant plastics while minimizing mechanical stress on the sample tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a press fit with large-area contact is used to seal the cap, then a gas-tight and liquid-tight seal is achieved, but a relatively large force acts on the sample tube causing it to break easily
Solution Approach 1:
The sealing contact area is segmented into multiple discrete contact points around the circumference rather than a continuous large-area press fit. This segmentation allows the sealing force to be distributed through the cap structure rather than concentrated on the sample tube wall, achieving effective sealing while reducing the force transmitted to the sample tube.
Solution Approach 2:
The cap is designed with non-uniform wall thickness, featuring a thicker wall section specifically at the sealing contact area. This local quality enhancement provides structural reinforcement at the sealing location, allowing the cap to withstand sealing forces without transmitting excessive stress to the sample tube, while maintaining overall seal integrity.
2Reliability
If narrow manufacturing tolerances are used for the contact surface and sample tube outer wall, then a good seal is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The sealing interface is divided into multiple discrete contact points rather than requiring a continuous precise fit. This segmentation relaxes the tolerance requirements for each individual contact point while maintaining overall sealing effectiveness, as the multiple points collectively provide the necessary seal without requiring tight tolerances across the entire circumference.
Solution Approach 2:
The cap incorporates a locally reinforced wall section at the sealing area with increased thickness. This local quality enhancement compensates for variations in manufacturing tolerances of both the cap and sample tube, providing a robust sealing interface that maintains seal quality even when dimensional variations occur within wider tolerance ranges.
3Manufacturing precision
If a soft cap material like polypropylene is used, then manufacturing tolerances can be relaxed, but chemical resistance to NMR solvents deteriorates
Solution Approach 1:
The cap is designed with a non-uniform wall thickness profile, featuring a thicker section at the sealing area. This local reinforcement allows the use of harder, chemically resistant materials while maintaining the elasticity needed for sealing. The increased material volume at the sealing location provides both the structural support and elastic deformation capability required for effective sealing, enabling the use of materials with superior chemical resistance properties.
Solution Approach 2:
The invention changes the geometric parameter of wall thickness at the sealing location rather than relying solely on material softness. By increasing the wall thickness at the sealing area, the cap gains sufficient elasticity and compliance for sealing purposes while可以使用 harder, chemically resistant materials, thus decoupling the relationship between material hardness and sealing capability.
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 cap achieves a gas-tight and liquid-tight seal with reduced force on the sample tube, allowing for easier assembly and increased chemical resistance, reducing the risk of breakage and simplifying manufacturing.
Implementation Method 1
the constriction is formed as a circumferential, inner, elastically deformable sealing lip over the entire outer circumference
Data Source
Figure 1
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AI summary
The cap (1) has an interior sealing lip (3) for receiving an open end of a nuclear magnetic resonance sample tube. The interior sealing lip has a contraction for sealing a received nuclear magnetic resonance sample tube against the cap along the outer circumference of the nuclear magnetic resonance sample tube. The contraction is formed as an internal sealing lip. The cap is manufactured from plastic.