O-ring Cross-section Design for Vacuum Joint Thermal Stress
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Solution Overview
Problem
Conventional clamp-type joints for vacuum apparatuses experience sealing failures due to O-ring cracking at high temperatures, primarily caused by stress concentration from thermal expansion differences between rubber and metal components.
Innovation Solution
The design incorporates an O-ring with a circular arc diameter on the side contacting the outer ring being smaller than on the axial side, reducing stress concentration and preventing cracking, while maintaining firm engagement with the outer ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an outer ring is provided around the O-ring to inhibit outward expansion due to internal pressure, then sealing performance is improved, but stress concentration occurs at high temperature causing O-ring cracking
Solution Approach 1:
The O-ring cross-section is designed with non-uniform circular arc diameters: a smaller diameter at the outer ring contact portion and a larger diameter at the axial joint portion. This local variation in geometry distributes the thermal expansion stress more evenly, preventing stress concentration and cracking at the contact points with the outer ring while maintaining sealing effectiveness.
2Ease of manufacture
If the O-ring has a uniform circular cross-section, then manufacturing is simple, but stress concentrates at contact points with the outer ring at high temperature
Solution Approach 1:
The O-ring cross-section features locally varied circular arc diameters rather than a uniform shape. The smaller circular arc diameter at the outer ring contact portion specifically addresses thermal stress concentration, while the larger circular arc diameter at the axial portion maintains structural integrity. This localized geometric modification balances manufacturing feasibility with thermal stress resistance.
3Reliability
If the O-ring expands outwardly due to thermal expansion at high temperature, then sealing contact is maintained, but the O-ring is pressed against the outer ring causing stress concentration
Solution Approach 1:
The non-uniform circular arc diameter design allows the O-ring to accommodate thermal expansion differently at different locations. The smaller circular arc at the contact portion provides more compliance to the outer ring constraint, reducing stress concentration while the larger circular arc at the axial portion maintains adequate sealing contact pressure.
Solution Approach 2:
The O-ring geometry parameters are specifically optimized with different circular arc diameters at different cross-sectional locations. This parameter variation enables the O-ring to manage thermal expansion stresses effectively, maintaining sealing contact stability while preventing excessive stress concentration against the outer ring.
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 configuration ensures stable sealing performance at high temperatures without O-ring cracking and prevents the outer ring from coming off, thereby ensuring reliable operation.
Implementation Method 1
due to the greater coefficient of thermal expansion of the rubber used for the O-ring than the coefficient of thermal expansion of metal used for the outer ring by several digits, the O-ring significantly expands outwardly, is pressed against the outer ring, and strongly pushes the brim of the outer ring at high temperatures
Data Source
AI summary
An O-ring used in a clamp-type joint for a vacuum apparatus, which engages with a concave groove in the outer circumference edge of the center ring and is sandwiched by an outer ring having a U-shaped outer circumference, wherein the radius of the circular arc in the cross-section on the side coming into contact with the outer ring is smaller than the radius of the circular arc in the cross-section on the axial side of the joint. A clamp-type joint for the vacuum apparatus which can exhibit stable sealing performance at a high temperature of 200° C. or more without cracking of the O-ring, as well as an outer ring and O-ring used with the clamp-type joint are also provided.