Vacuum Joint Outer Ring Convex Brim Design
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Solution Overview
Problem
Conventional clamp-type joints for vacuum apparatus experience O-ring cracking at high temperatures due to stress concentration caused by the difference in thermal expansion coefficients between the rubber O-ring and metal outer ring, leading to sealing failures.
Innovation Solution
The design incorporates an outer ring with brims that contact the O-ring in the form of a convex sector, reducing stress concentration by using a radius of 0.6-2.5 mm and thickness within specific limits to ensure stable engagement and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an outer ring with flat brims is used to prevent O-ring expansion at high temperature, then sealing stability is improved, but stress concentration causes O-ring cracking
Solution Approach 1:
The brim inner surface is designed with a convex sector shape having a specific radius of curvature (0.6-2.5 mm), transforming the flat contact surface into a curved one. This curvature distributes the contact stress from the thermally expanding O-ring across a broader area, preventing stress concentration and subsequent cracking while maintaining effective sealing at high temperatures.
2Strength
If the brim contact surface is made convex with specific radius, then stress concentration is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies an optimized range for the convex sector radius (0.6-2.5 mm) that balances stress distribution performance with manufacturability. This parameter optimization ensures that the curvature is sufficient to reduce stress concentration while remaining feasible for standard manufacturing processes, avoiding excessive precision requirements.
3Reliability
If the outer ring thickness is increased to prevent coming off, then engagement stability is improved, but stress concentration increases
Solution Approach 1:
The convex sector shape of the brim inner surface distributes the contact stress from the O-ring across a curved surface rather than a flat one. This curvature allows the outer ring to maintain sufficient thickness for engagement stability while reducing peak contact stress, as the force is distributed over a broader contact area following the convex geometry.
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 prevents O-ring cracking and ensures firm engagement without the outer ring coming off, maintaining stable sealing performance at high temperatures up to 200°C.
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 outer ring of a clamp-type joint for vacuum apparatus is disclosed. The joint includes a base forming an outer circumferential side and a pair of brims respectively extending from the top and bottom of the base toward the center axis of the joint, the inner side of the brims on which the brims come into contact with the O-ring being in the form of a convex sector, of which the arc faces the O-ring. The radius r of the circle forming the sector is 0.6-2.5 mm and the thickness (t0) satisfies the following formula: t1−0.2≦t0≦t1+0.4. In the formula, t1 is a thickness (mm) of the center ring at the point at which the center ring engages with the O-ring. The clamp-type joint can exhibit stable sealing performance at a high temperature of 250° C. or more without cracking of the O-ring.