Vacuum Valve Bellows Stress Equalization
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Solution Overview
Problem
Conventional vacuum valve bellows experience fatigue fractures at valley portions due to uneven stress distribution during expansion and contraction, leading to premature failure.
Innovation Solution
Adjusting the radii of curvature of valley and peak portions in the bellows to a specific ratio range (1.15 to 1.70) to equalize stresses, achieved through hydrostatic bulge forming and deep-drawing of stainless steel, ensuring balanced stress amplitudes during valve operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the radii of curvature of valley and peak portions are made equal, then the bellows structure is simple to manufacture, but stress concentration occurs at valley portions leading to fatigue fracture
Solution Approach 1:
The invention changes the geometric parameters of the bellows by setting the radius of curvature of valley portions (Rv) to be 1.05 to 1.3 times the radius of curvature of peak portions (Rp). This parameter adjustment equalizes the stress amplitudes at valley and peak portions during expansion and contraction, preventing stress concentration at valley portions and eliminating fatigue fractures while maintaining manufacturing feasibility through hydrostatic bulge forming
Solution Approach 2:
The invention applies different radius of curvature values to different locations of the bellows structure. Specifically, the valley portions are designed with larger radii of curvature compared to peak portions, creating local geometric differences that distribute stress more evenly throughout the structure during cyclic operation
2Length of moving object
If the bellows is extended to increase valve opening distance, then the valve performance improves, but the stress amplitude at valley portions increases causing earlier fatigue failure
Solution Approach 1:
By optimizing the radius of curvature ratio (Rv/Rp = 1.05 to 1.3) and the bellows geometry parameters, the invention enables the bellows to withstand larger extension distances without experiencing excessive stress amplitudes at valley portions, thus allowing greater valve opening distances while maintaining fatigue resistance
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 approach extends the life of the bellows by reducing metal fatigue and maintaining stress equality across valley and peak portions, regardless of the bellows' extension or compression ratio, thereby enhancing the durability of vacuum valve components.
Implementation Method 1
an expandable and contractible molded bellows is provided between the circumference of the disc-shaped valve member and the housing so as to surround the rod
Implementation Method 2
a high-pressure liquid is introduced into the untreated pipe, causing portions of the outer periphery of the untreated pipe that are not in contact with the ring-shaped molds to swell outward
Data Source
AI summary
A bellows is disposed to separate a main flow path that is opened or closed by a valve member coming into contact with or moving away from a valve seat from a driving part for driving the valve member via a rod so as to surround the rod. The bellows is formed by providing ring-shaped valley portions swelling inward of a metal pipe and ring-shaped peak portions swelling outward of the metal pipe alternately and continuously in a peripheral wall of the metal pipe in the axial direction of the metal pipe. Valley R/peak R, which is the ratio of valley R to peak R, is in the range of 1.15 to 1.70, where valley R is the radius of curvature of the valley portions in cross section, and peak R is the radius of curvature of the peak portions in cross section.