Self-Centering Insulating Washer for Filtered Feedthrough Alignment
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Solution Overview
Problem
Existing filtered feedthrough assemblies for active implantable medical devices face issues with the misalignment of insulating washers, which can lead to reduced high-voltage keep-out zones and potential high-voltage discharges due to the lubricious nature of polymeric materials, causing the washers to slide into misaligned positions and cover hermetic seals, thereby compromising the integrity of the electrical connections.
Innovation Solution
The implementation of self-centering insulating washers with shaped openings, such as baseball playing field-shaped or tooth-like structures, that prevent lateral movement by ensuring the cumulative arcuate distance of inner arcuate portions around terminal pins creates a gap less than the pin diameter, maintaining proper alignment and exposure of gold brazes for reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polymeric insulating washer with circular openings is used, then the washer is easy to manufacture and install, but the washer can laterally move and misalign due to the lubricious nature of polymeric materials
Solution Approach 1:
The patent applies asymmetry by changing the opening shape from circular to non-circular (e.g., D-shaped, rectangular, or oval) with flat sides or corners that contact the terminal pins. This asymmetric geometry prevents rotational movement and lateral shifting of the washer, ensuring precise alignment while maintaining ease of manufacture through standard cutting processes.
Solution Approach 2:
The patent utilizes curvature by designing openings with rounded corners or arcuate edges that match the curvature of the terminal pins. This curved geometry creates natural contact points that prevent lateral movement while allowing the washer to self-center on the pins, resolving the alignment issue without compromising manufacturability.
2Adaptability or versatility
If the washer openings are enlarged to accommodate terminal pin variations, then assembly tolerance is improved, but the washer can slide laterally and cover hermetic seals
Solution Approach 1:
The asymmetric opening shape with flat sides or corners provides lateral contact surfaces that constrain washer movement. This allows the opening to be slightly larger than the terminal pin for tolerance accommodation while preventing the washer from sliding and covering the hermetic seals, thus maintaining both adaptability and reliability.
Solution Approach 2:
The flat sides or corners of the opening act as intermediary contact surfaces between the washer and terminal pin. These intermediate features provide friction and mechanical constraint that prevent lateral movement, allowing tolerance variation without compromising hermetic seal integrity.
3Device complexity
If standard circular openings are used in the washer, then the design is simple and cost-effective, but misalignment occurs compromising electrical connection integrity
Solution Approach 1:
The patent modifies the simple circular opening to an asymmetric shape with minimal additional complexity. The D-shaped, rectangular, or oval opening with flat sides or corners provides the necessary anti-misalignment function while remaining simple to manufacture and integrate into the existing washer design, thus maintaining low device complexity while improving reliability.
Data Source
AI summary
A self-centering washer is positioned between the feedthrough and filter capacitor of a filtered feedthrough. The washer has openings through which first and second terminal pins extend. A first opening has an inner arcuate portion contacting the first terminal pin and an outer perimeter portion exposing the braze sealing the terminal pin to the insulator. A second opening has an inner arcuate portion contacting the second terminal pin and an outer perimeter portion exposing the braze sealing the terminal pin to the insulator. In an imaginary configuration with the first and second washer openings superimposed one on top of the other, the cumulative arcuate distance of the inner arcuate portions about one of the terminal pins, subtracting overlap, results in a gap between the superimposed washer openings that is less than a diameter of the first and second terminal pins so that the washer is prevented from lateral movement.