Capacitive Buckle Switch Eliminates Mechanical Wear

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Solution Overview

Problem

Conventional seat belt buckle switches face high manufacturing costs and a high likelihood of mechanical failure, necessitating a more durable and cost-effective solution with reduced installation complexity.

Innovation Solution

The proposed solution involves a seat belt buckle switch with a housing, an insertion member, and a connector that moves within the housing to connect or disconnect from a switch, utilizing a conductive element formed on flexible polymer films separated by an air gap, providing different resistance states to indicate the buckle's fastened or unfastened status.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional mechanical switches are used in seat belt buckles, then the buckle can identify whether the seatbelt is worn, but the manufacturing cost is high and the likelihood of mechanical failure is high

Engineering Contradiction:
Improveswitch durabilityVSAvoidmanufacturing cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces conventional mechanical switches with a capacitive sensing system that uses electrical fields to detect buckle insertion. The sensor detects changes in capacitance caused by the insertion member, eliminating moving mechanical parts and significantly improving reliability while reducing manufacturing complexity

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary capacitive sensing mechanism between the insertion member and the detection system. Instead of direct mechanical contact, the sensor detects electrical field changes caused by the insertion member's presence, providing indirect but reliable detection that reduces mechanical wear and failure

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If conventional mechanical switches are used in seat belt buckles, then the buckle can identify whether the seatbelt is worn, but the installation complexity is high

Engineering Contradiction:
Improveswitch durabilityVSAvoidinstallation complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical switch assemblies with integrated capacitive sensors that can be embedded directly into the buckle housing. This integration simplifies the overall device structure and reduces installation complexity while maintaining high reliability through the absence of mechanical failure points

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If conventional mechanical switches are used in seat belt buckles, then the buckle can identify whether the seatbelt is worn, but the manufacturing cost is high

Engineering Contradiction:
Improveswitch durabilityVSAvoidinstallation simplicity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical switches with capacitive sensors that detect insertion through electrical field changes. This substitution eliminates the need for complex mechanical assemblies, making the device easier to manufacture and install while significantly improving reliability through the elimination of mechanical wear and failure modes

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 durability, reduces manufacturing costs, and simplifies installation while effectively signaling the buckle's status through distinct resistance readings, improving reliability and operational efficiency.

Implementation Method 1

the switch includes a first conductive element formed adjacent a first layer of flexible polymer film, and a second conductive element formed adjacent a second layer of flexible polymer film

Methodology Applied
Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentEP3042807B1Seat belt buckle
Publication Date: 2019.04.17 LITTELFUSE INC
  • EP3042807B1 patent drawingFigure 1
  • EP3042807B1 patent drawingFigure 2
  • EP3042807B1 patent drawingFigure 3

AI summary

A thick film polymer membrane switch (108) can be positioned within a seat belt buckle. The switch (108) can detect if the seat belt buckle is fastened or unfastened. In one approach, an apparatus includes a housing (102) having a cavity (105), an insertion member (118) moveable within the cavity (105), a connector (106) positioned within the cavity (105), and a switch (108) positioned within the cavity (105), wherein movement of the insertion member (118) causes the connector (106) to connect or disconnect from the switch (108). In some approaches, the switch (108) includes a first conductive element formed adjacent a first layer of flexible film, and a second conductive element formed adjacent a second layer of flexible film, wherein the first and second layers of flexible film are separated by a gap.