Movable Contact Wire-Rod Assembly for Lower-Cost Variable Resistors

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Solution Overview

Problem

Existing variable resistors using lead-free inks and beryllium copper contacts face inadequate properties and increased costs due to the use of precious metal alloys and complex assembly processes.

Innovation Solution

A movable contact design comprising a first wire rod group made of precious metal and a second wire rod group made of a different metal, both arranged orthogonally, with a shaft-shaped member welded to both groups, allowing for a simpler assembly process that reduces component count and assembly time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a contact part made of precious metal alloy is welded and fixed to the support part via an attachment member, then adequate properties are obtained, but the number of components and assembly man-hours increase

Engineering Contradiction:
Improvecontact propertiesVSAvoidnumber of components
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the support part and contact part into a single integrated component made of copper alloy. The contact part is formed as an integral extension of the support part, eliminating the need for separate attachment members and reducing assembly steps while maintaining adequate electrical contact properties through the continuous metallic structure.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The copper alloy support part serves multiple functions simultaneously: it provides structural support, acts as an electrical conductor, and forms the contact part itself. This multi-functional design eliminates the need for separate precious metal contact components while achieving both mechanical and electrical requirements.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If a contact part made of precious metal alloy is welded and fixed to the support part via an attachment member, then adequate properties are obtained, but assembly man-hours increase

Engineering Contradiction:
Improvecontact propertiesVSAvoidassembly man-hours
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The support part and contact part are merged into a single integrally formed component, eliminating the welding and attachment operations that previously consumed assembly time. The continuous metallic structure is formed in one manufacturing process, reducing assembly man-hours while maintaining adequate contact properties.

Inventive Principle:
Principle #5Merging (Combining)

3Object-affected harmful factors

If lead-free ink is used for printing the resistor, then global environmental conservation is achieved, but adequate properties cannot be obtained

Engineering Contradiction:
Improveenvironmental impactVSAvoidvariable resistor properties
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent uses a copper alloy material that combines copper with other metals to achieve both environmental compatibility (lead-free) and adequate electrical and mechanical properties. The composite copper alloy structure provides the necessary conductivity, strength, and contact characteristics without relying on lead-based materials.

Inventive Principle:
Principle #40Composite materials

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 design suppresses cost increases by minimizing the number of components and assembly hours while maintaining adequate properties, achieving a cost-effective solution.

Implementation Method 1

a shaft-shaped member which is disposed so as to cross the first wire rod group and the second wire rod group and is welded to the first wire rod group and the second wire rod group

Methodology Applied
Scientific EffectWelding: Welding

Data Source

PatentEP4131293B1Movable contact, variable resistor, and method for manufacturing movable contact
Publication Date: 2025.08.13 TOKYO COSMOS ELECTRIC CO LTD
  • EP4131293B1 patent drawingFigure 1
  • EP4131293B1 patent drawingFigure 2~3
  • EP4131293B1 patent drawingFigure 4A~4C

AI summary

Provided are a movable contact, a variable resistor, and a method for manufacturing a movable contact that can suppress a cost increase. The movable contacts are spaced apart from each other. The variable resistor, having a resistor, an electrode and the movable contact, comprises: a first wire rod group which has a plurality of first wire rods made of a precious metal and in which the plurality of first wire rods are arranged along the resistor; a second wire rod group which has a plurality of second wire rods made of a metal other than the precious metal and in which the plurality of second wire rods are arranged along the electrode; and a shaft-shaped member which is disposed to cross the first wire rod group and the second wire rod group and is welded to the first wire rod group and the second wire rod group.