Split Spring Contact for Inertia Switch Retention
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Solution Overview
Problem
Current inertia switches face issues due to undue stress and deformation caused by interference fits and manual arbor tools, leading to dimensional changes and particulate formation, which affect the switch's functionality and reliability.
Innovation Solution
A split spring contact design with a conductive body portion and a break-off tab, where the split reduces stress during insertion and generates a radially outward force for uniform contact, and the break-off tab controls deflection to minimize deformation and particulate formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a flat spring contact is pressed into the mass with an interference fit for retention and electrical conductivity, then the spring contact is securely retained and electrically conductive, but the interference fit causes undue stress on the thin spring contact which results in various deformations, adversely affecting the function of the switch
Solution Approach 1:
The spring contact is segmented into a body portion and a contact finger portion, allowing the contact finger to be inserted into the mass through a hole while the body portion remains external. This segmentation enables the contact finger to be retained by the mass without requiring the entire spring contact to be deformed by interference fit, thereby reducing stress and deformation on the thin spring contact material while maintaining secure retention and electrical conductivity.
2Ease of manufacture
If a manually-operated arbor tool is used to press the flat spring contact into the mass, then the spring contact is installed, but the high forces required to overcome the interference between the spring contact and the mass cause deformation to the spring contact, resulting in dimensional changes to the interface between the spring and the spring contact, adversely affecting the function of the switch
Solution Approach 1:
By segmenting the spring contact into a body portion and a contact finger portion, the installation process only requires forcing the contact finger through a hole in the mass, which demands significantly lower force than pressing a flat spring contact with interference fit. This reduces deformation during installation while maintaining ease of manufacture through simple insertion.
Solution Approach 2:
The contact finger portion is extracted from the flat spring contact structure and inserted through a hole in the mass, separating the retention function from the electrical contact function. This allows the contact finger to be retained by the mass without requiring high installation forces that would deform the thin spring contact material, preserving interface dimensional stability.
3Ease of manufacture
If break-off tabs are used for separating individual spring contacts from the sheet, then spring contacts can be separated, but the break-off tab results in a protruding section of the spring contact which scrapes the inside of the mass during the insertion process, resulting in contact deformation
Solution Approach 1:
The break-off tab is positioned and designed to break away completely during the insertion process, leaving no protruding section. The tab is extracted from the final assembled structure, eliminating the source of scraping and contact deformation while maintaining ease of manufacture through simple tab-based separation from the sheet.
4Strength
If interference press fit is used to secure the spring contact, then retention is achieved, but the interference press fit creates particulate from the spring contact shaving material from the mass, which may cause additional deformation to the spring contact, increasing the friction of the mass movement, and changing the electrical characteristics of the switch
Solution Approach 1:
Segmenting the spring contact into a body portion and contact finger portion allows the contact finger to be inserted through a hole and retained by the mass without requiring interference fit of the entire spring contact. This eliminates the shaving and particulate formation associated with interference press fit while maintaining secure retention through the hole insertion and retention mechanism.
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 decreases stress and deformation, enhances reliability, and provides a chatter-proof contact, increasing the retention and performance of the inertia switch.
Implementation Method 1
the split in the conductive body portion of the spring contact decreases the stresses applied to the spring contact during insertion of the spring contact within the mass
Implementation Method 2
a spring contact positioned within the mass, the spring contact comprising a conductive body portion
Implementation Method 3
a biasing member positioned between the spring contact and the header; and a conductive member extending through the header. The biasing member provides a bias between the spring contact within the mass and the conductive member
Data Source
AI summary
A spring contact, an inertia switch, and a method of manufacturing an inertia switch are provided. The spring contact includes a conductive body portion having an outer edge and an inner edge partially surrounding an open area, a split in the conductive body portion, the split extending between the outer edge and the inner edge, and a conductive contact finger extending from the inner edge into the open area. The inertia switch includes a shell; a mass movably positioned within the shell; the spring contact positioned within the mass; a biasing member positioned between the spring contact and the header; and a conductive member extending through the header. The biasing member provides a bias between the spring contact within the mass and the conductive member. The method includes at least partially closing the split in the spring contact during insertion of the spring contact within the mass.