Spherical Contact Member Pendulum Motion for Heating Element

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Solution Overview

Problem

Existing contacting devices for heating elements in cooking appliances face issues with thermal expansion, leading to translational relative movements that cause corrosion, increased resistance, and premature wear, especially at high temperatures, resulting in frequent replacement of contact members.

Innovation Solution

A contact member is movably mounted to perform a pendulum movement parallel to the contact surface, avoiding translational relative movement, with a spring tensioning mechanism ensuring constant and perpendicular contact force, using a silver-nickel rivet and a ceramic sleeve for enhanced stability and corrosion resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a contact element is pressed onto a contact surface using a spring mechanism, then electrical contact is established, but translational relative movements occur due to thermal expansion differences, leading to corrosion and increased resistance

Engineering Contradiction:
Improvecontact stabilityVSAvoidcorrosion and fritting
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The contact element features a spherical contact surface instead of a flat surface. This curvature allows the contact element to perform pendulum movements and rolling motions rather than translational sliding, converting harmful linear friction into beneficial rolling contact that self-cleans the contact surface and prevents corrosion

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The contact element is designed to be dynamically movable within the holding member, allowing it to perform pendulum movements and rolling motions in response to thermal expansion and contraction. This dynamic behavior adapts to temperature changes while maintaining stable electrical contact and preventing wear through rolling rather than sliding

Inventive Principle:
Principle #15Dynamics

2Reliability

If a spring-elastic locking element is used to maintain contact, then electrical connection is achieved, but the contact element wears away after short period due to micro-movements

Engineering Contradiction:
Improveelectrical connectionVSAvoidservice life of contact member
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The spherical contact surface enables rolling motion that significantly reduces wear compared to sliding contact. The rolling action minimizes material removal and prevents the contact element from wearing away, thereby extending service life while maintaining reliable electrical connection

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The thermal expansion and contraction that cause harmful translational movements are converted into beneficial rolling motions. The micro-movements that would normally cause wear are transformed into self-cleaning rolling actions that remove oxidation and prevent corrosion, turning a harmful effect into a protective mechanism

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

3Temperature

If contact members are used in high temperature applications (450°C), then heating function is achieved, but contact resistance increases and power line stops due to contact burn-off

Engineering Contradiction:
Improveheating temperatureVSAvoidpower line continuity
Core Design Contradiction:
TemperatureVSReliability

Solution Approach 1:

At high temperatures, thermal expansion causes the spherical contact element to perform rolling motions that actively clean the contact surface by removing oxidation and burn-off products. This self-cleaning effect prevents contact resistance from increasing and maintains power line continuity even at 450°C

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The invention changes the contact geometry parameter from flat to spherical, which fundamentally alters the contact mechanics. This parameter change enables rolling motion that is particularly effective at high temperatures where thermal expansion is more pronounced, converting temperature-induced stress into beneficial cleaning action

Inventive Principle:
Principle #35Parameter changes

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 maintains constant contact resistance, minimizes wear, and ensures high-temperature stability by converting micro-movements into rolling movements, reducing corrosion and extending the lifespan of contact members.

Implementation Method 1

a spring (30) which surrounds the plunger (20) in such a way that the spring (30) pre-tensions the longitudinal axis of the plunger (20) essentially perpendicularly to the contact surface (32)

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

the contact member (20) performs a pendulum movement essentially parallel to the contact surface (32) in order to roll off the contact surface (32)

Methodology Applied
Scientific EffectPendulum movement: Pendulum

Implementation Method 3

an essentially sleeve-shaped, preferably insulating, holding member (18)

Methodology Applied
Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentEP1855357B1Device for electrically contacting a contacting surface, heating element with such a device and cooking apparatus with such a heating element
Publication Date: 2008.12.24 FRIMA
  • EP1855357B1 patent drawingFigure 1~3
  • EP1855357B1 patent drawingFigure 4~5

AI summary

The device has a heating unit (10) and a contact surface (32) that is connected by the device in a removable manner. A plunger (20), a contact area (22), a circulating edge (26) and a rivet (34) are provided for contacting the contact surface. The plunger, the contact area, the circulating edge and the rivet are supported by a ceramic sleeve (18) in such a manner that they effect pendulum movement parallel to the contact surface during impact with force.