Vacuum Interrupter Retainer and Bushing Design
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Solution Overview
Problem
Existing vacuum interrupters face challenges in designing a retainer and bushing system for movable electrodes that efficiently utilize limited space and maintain vacuum integrity, particularly due to the constraints imposed by mounting studs and the need for rigid retention of plastic bushings.
Innovation Solution
A retainer with a plurality of legs and an insulative bushing, where the bushing opening is smaller than the retainer opening, is molded over the retainer, providing a secure and space-efficient solution for the movable electrode, with features like flat surfaces to prevent twisting and a conduit portion for axial movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a plastic bushing with mating features is used to rigidly hold the movable electrode, then the movable electrode can be securely retained, but the space between the movable electrode and mounting studs is insufficient for accommodation
Solution Approach 1:
The retainer is nested within the bushing, with the retainer's outer surface fitting inside the bushing's inner surface. This nested configuration allows the retainer to be accommodated within the limited space between the movable electrode and mounting studs, while still providing rigid retention through the retainer's engagement with the movable electrode.
Solution Approach 2:
The retainer extends radially outward from the movable electrode in a direction perpendicular to the axial movement, utilizing the radial dimension rather than requiring additional axial space. This dimensional change allows the retainer to provide secure retention without increasing the space requirement in the constrained axial direction between the movable electrode and mounting studs.
2Reliability
If a metal retainer with spot welding is used to hold the plastic bushing, then the assembly is strong and reliable, but the manufacturing process becomes more complex
Solution Approach 1:
The retainer and bushing are combined into a single integrated component through the molding process, where the retainer is formed as an integral part of the bushing structure. This merging eliminates the need for separate assembly steps and complex welding operations, simplifying manufacturing while maintaining assembly reliability through the unified structure.
Solution Approach 2:
The retainer-bushing assembly utilizes composite construction with the retainer made from metal material providing strength and the bushing made from molded material providing insulation and structural integration. This composite approach maintains reliability through material-appropriate functions while simplifying manufacture through integral formation.
3Ease of operation
If the bushing opening is made large enough to accommodate the movable electrode, then the electrode can be easily installed, but the vacuum integrity is compromised
Solution Approach 1:
The retainer is nested within the bushing, creating a tiered structure where the retainer's opening provides the larger clearance for easy electrode installation, while the bushing's smaller opening maintains vacuum integrity. The nested configuration allows both opening sizes to coexist in a compact arrangement.
Solution Approach 2:
The opening structure is segmented into two distinct levels: the retainer opening with larger dimensions for easy electrode installation, and the bushing opening with smaller dimensions for maintaining vacuum integrity. This segmentation allows each opening to fulfill its specific function without compromising the other.
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 design enhances the structural integrity and assembly efficiency of vacuum interrupters by providing a stronger bushing/retainer combination that maintains vacuum integrity and facilitates easier assembly, while optimizing space usage.
Implementation Method 1
The insulative bushing is molded over a portion of the rigid retainer
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A vacuum interrupter (6) includes a number of insulative tubes (38) having a first open end (58) and a second open end (60); a first end member (42) secured to the first open end; a second end member (40) secured to the second open end; a fixed contact (46) mounted on a fixed electrode (48) extending through the second end member; a retainer (2); and a movable contact (59). The retainer includes a rigid retainer (8) having a plurality of legs (10) and an opening (12), and an insulative bushing (14) having a smaller opening (16). The insulative bushing is molded over a portion of the rigid retainer. The smaller opening is within the opening of the rigid retainer and is structured to receive a movable electrode. The movable contact is mounted on the movable electrode extending through the first end member and through the smaller opening. The movable contact is capable of axially reciprocating into and out of contact with the fixed contact.