Valve Cap Assembly with Interference Protrusions
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Solution Overview
Problem
Existing valve caps for pneumatic tires often get lost or come off during use, due to inadequate retention mechanisms, and existing tethered solutions can be difficult to remove and reinstall.
Innovation Solution
A valve cap assembly featuring a cap with interference protrusions that form a reliable fit with the air valve, combined with a hoop and flexible tether that allows easy attachment and detachment, using thermoplastic elastomer materials for secure retention and easy handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protrusions extend into the valleys between adjacent threads to secure the cap, then the cap retention reliability is improved, but the ease of operation deteriorates because the cap becomes difficult to remove
Solution Approach 1:
The protrusions are designed with non-uniform geometry where they extend further in the axial direction at specific locations (into thread valleys) to create localized interference fits that prevent rotational movement, while maintaining smooth surfaces in other areas for easy axial removal. This local differentiation of geometric properties resolves the contradiction between secure retention and easy operation.
Solution Approach 2:
The cap's protrusions are segmented into multiple discrete elements distributed around the circumference, with each protrusion having varying lengths along the axial direction. This segmentation allows different portions of the protrusions to serve different functions: longer portions engage thread valleys for anti-rotation, while shorter portions allow easy axial insertion and removal.
2Reliability
If a tether is used to prevent cap loss, then the reliability of cap retention is improved, but the device complexity increases due to additional components
Solution Approach 1:
The tether function is merged with the cap structure itself by integrating the tether attachment directly into the cap body. The tether is not a separate component but is incorporated as part of the cap assembly, reducing overall device complexity while maintaining the reliability benefit of preventing cap loss.
Solution Approach 2:
The cap structure serves multiple functions: it protects the valve, provides interference fits for retention, prevents rotation through protrusions, and includes integrated tether attachment for loss prevention. This multi-functionality eliminates the need for separate tether components, resolving the contradiction between reliability and complexity.
3Reliability
If interference features are deformed to generate retention forces, then the cap retention reliability is improved, but the ease of operation worsens due to increased resistance during installation and removal
Solution Approach 1:
The interference features utilize controlled elastic deformation of the cap material (thermoplastic elastomer) to generate retention forces. The material's elastic properties allow temporary deformation during installation that automatically rebounds to create holding forces, while the deformation magnitude is controlled to remain within elastic limits, ensuring easy removal without permanent damage.
Solution Approach 2:
The cap is made from thermoplastic elastomer, a composite material that combines the elasticity of rubber with the processability of plastics. This material enables the interference features to deform elastically for retention while maintaining sufficient flexibility for easy installation and removal, resolving the contradiction between retention reliability and operational ease.
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 assembly effectively prevents cap loss and easy removal/installation, maintaining secure attachment during use while resisting axial and rotational movement, and allowing for easy placement and removal.
Implementation Method 1
The interference features are deformed by the valve stem to generate forces applied by the cap and the hoop to the stem that resist axial movement of the cap and hoop along the valve stem
Data Source
AI summary
A valve cap assembly for being attached to an air valve and removably covering an end of the air valve includes a hoop, a cap, and an arched tether connecting the hoop and the cap. The hoop attaches the valve cap assembly to the air valve. The cap removably covers the end of the air valve to protect the end of the air valve. Both the hoop and the cap form a dependable interference fit between the hoop or cap and the valve stem to retain the hoop on the valve stem and to retain the cap covering the end of the air valve on the air valve. The cap includes one or more longitudinal protrusions that form the interference fit.