Vacuum Interrupter Screen Centering via Plastic Deformation Tabs
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Solution Overview
Problem
The assembly of vacuum interrupters faces challenges in maintaining concentricity of internal elements with the envelope during temperature rise cycles due to differences in expansion coefficients and geometrical tolerances, leading to misalignment and increased manufacturing costs, with existing centering systems being either costly or ineffective for copper shields.
Innovation Solution
A centering device using stainless steel metal strips with elastic tabs, folded along a parallel axis, wound around the screen, and spot-welded at both ends, allowing for both cold and hot centering without damaging the ceramic envelope, ensuring reliable and durable alignment throughout the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elastic slats are used for centering, then stainless steel screens can be centered effectively, but copper shields cannot be centered due to insufficient elasticity
Solution Approach 1:
The patent changes the material parameter from elastic slats to plastic deformation tabs. The tabs are made from the same copper material as the shield, allowing them to undergo plastic deformation during hot centering to accommodate thermal expansion differences, thus enabling effective centering for copper shields that elastic slats cannot achieve.
2Manufacturing precision
If centering systems are equipped to maintain concentricity during temperature cycles, then alignment is improved, but manufacturing cost increases due to tight tolerances and additional components
Solution Approach 1:
The centering tabs are integrated directly into the copper shield component itself, making the shield self-centering. The tabs are formed from the shield material and perform the centering function automatically during assembly and thermal cycles, eliminating the need for separate external centering devices and reducing manufacturing complexity.
Solution Approach 2:
The patent uses composite structure where the centering tabs are formed from the same copper material as the shield, creating an integrated component. This composite approach allows the tabs to deform plastically under heat, absorbing thermal expansion differences between the copper shield and ceramic envelope, thereby maintaining concentricity without requiring tight tolerances on the ceramic parts.
3Reliability
If brazing is used to install centering slats, then centering is achieved, but the process becomes costly and complex
Solution Approach 1:
The centering tabs are merged with the copper shield as an integral part of the same component. The tabs are formed from the shield material itself through plastic deformation, eliminating the need for separate slat components and their associated brazing installation processes, thus simplifying the overall assembly process while maintaining centering stability.
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 solution provides a cost-effective and reliable method for maintaining concentricity of metal screens within vacuum interrupters, eliminating the need for external tools and allowing for less stringent tolerances, ensuring accurate alignment from assembly to cooling cycles.
Implementation Method 1
portions formed by cutting and then partial stamping of a part of the metal strip so as to form elastic tabs
Implementation Method 2
During temperature brazing, the copper screen expands more than the ceramic envelope. The bosses made on the screen then come into contact with the ceramic and recenter the screen by the effect of the heating without damaging the ceramic because the copper screen is softened by the heating.
Data Source
Figure 1
Figure 2
Figure 3~4a
AI summary
The present invention relates to a device for centering a metallic screen inside a vacuum ampoule, this centering device being intended to center the screen relative to the envelope prior to the screen being fixed to the envelope at high temperature. This device is characterized in that it comprises at least one metallic strip (12, 13) wrapped around the screen (6, 6a) and fixed thereto, said strip (12, 13) having several cutouts which, after plastic deformation, form tabs (15) inclined relative to the surface of the screen in the direction of the envelope, such that when the screen is introduced into the envelope of the ampoule, these tabs are subjected to a first elastic deflection towards the screen (6, 6a) when they come into contact with the inner wall (1b) of the envelope (1), then these same tabs (15) perform a first centering of said screen (6,6a) by elastic return of the tabs towards the casing, and that during the hot-fixing operation of said screen to the casing (1,1a), these same tabs (15) are subjected to a second bending towards the casing, under the effect of the differential expansion between the casing and the screen, so as to maintain the first centering achieved.