A cooking vessel and manufacturing method

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Solution Overview

Problem

Existing induction cooking vessels made with ferritic stainless steel suffer from temperature measurement inaccuracy due to hysteresis issues when heating and cooling, making it difficult to determine the correct temperature based on resonant frequency.

Innovation Solution

A cooking vessel with a bottom section made of unalloyed or low-alloyed steel, attached to a receptacle using a thin coating layer of chromium, nickel, aluminum, or copper, allowing for accurate temperature determination through frequency measurement with minimal hysteresis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferritic stainless steel is used in the bottom section of the cooking vessel, then the vessel can be heated by induction heater, but the temperature measurement accuracy deteriorates due to hysteresis between heating and cooling

Engineering Contradiction:
Improveinduction heating capabilityVSAvoidtemperature measurement accuracy
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the material parameter of the bottom section from ferritic stainless steel to unalloyed or low-alloyed steel. This material substitution fundamentally alters the magnetic properties and thermal behavior, eliminating the hysteresis effect that caused measurement inaccuracies while preserving induction heating capability. The new material enables the resonant frequency to accurately reflect temperature during both heating and cooling phases.

Inventive Principle:
Principle #35Parameter changes

2Ease of manufacture

If a coating layer is applied between the bottom section and receptacle, then manufacturing flexibility and corrosion resistance are improved, but the complexity of manufacturing increases

Engineering Contradiction:
Improvemanufacturing flexibilityVSAvoidmanufacturing process complexity
Core Design Contradiction:
Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent applies a coating layer selectively only at the interface between the bottom section and the receptacle, rather than coating the entire vessel. This localized coating approach provides corrosion resistance and manufacturing flexibility at the critical joint area while minimizing the added complexity and cost compared to full-surface coating.

Inventive Principle:
Principle #3Local quality

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

Enables precise temperature measurement of the cooking vessel during both heating and cooling with an error of less than 5 °C, eliminating the hysteresis issue present in prior art solutions.

Implementation Method 1

Induction heaters heat cooking vessels by magnetic induction which is obtained with an alternating electric current fed through a coil. The resulting field induces eddy currents in the cooking vessel, in particular in the bottom of the cooking vessel, which contribute in heating the cooking vessel.

Methodology Applied
Scientific EffectMagnetic induction: Electromagnetic Induction

Implementation Method 2

The resulting field induces eddy currents in the cooking vessel, in particular in the bottom of the cooking vessel, which contribute in heating the cooking vessel.

Methodology Applied
Scientific EffectEddy currents: Eddy Currents

Implementation Method 3

Previously it is known to provide under a cooking support of an induction heater a measuring instrument with an measuring coil. This measuring instrument produces an induction measuring resonant circuitry which interacts with the cooking vessel. The measuring resonant circuitry has a resonant frequency which is dependent on the permeability or inductivity of the cooking vessel.

Methodology Applied
Scientific EffectMagnetic coupling: Magnetic Field

Data Source

PatentEP3162258B1A cooking vessel and manufacturing method
Publication Date: 2021.03.24 FISKARS FINLAND OY AB
  • EP3162258B1 patent drawingFigure 1~3
  • EP3162258B1 patent drawingFigure 4

AI summary

The invention relates to a cooking vessel (1)comprising a receptacle (3) of a first material for receiving foodstuff, and a bottom section (6) of a second material, the bottom section being attached to the receptacle (3) for providing an induction heating capability for the cooking vessel (1). In order to provide a cooking vessel whose temperature can simply and reliably be determined during induction heating the second material is unalloyed or low-alloyed steel.