Cooktop appliance and heating element having a thermally isolated thermostat

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Solution Overview

Problem

Existing electric coil heating elements in cooktop appliances face issues with imperfect temperature correlation due to poor contact between cookware and the heating coil, leading to early tripping of the bimetallic thermostat caused by radiative heat transfer, resulting in reduced performance and the need for conservative calibrations.

Innovation Solution

The design incorporates a spiral wound sheathed heating element with a shroud cover and a spring bracket that positions a thermostat between coil sections, enhancing conductive heat transfer while shielding it from radiative heat, and includes a shroud cover with a top wall to contact the utensil and a lower surface to attach the thermostat, facilitating robust and easy assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the thermostat is remotely positioned from the cookware, then the system structure is simpler, but the temperature correlation becomes less accurate

Engineering Contradiction:

Improvethermostat positioning structureVSAvoidtemperature correlation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces a shroud cover as an intermediary component that physically connects the thermostat to the cookware. The shroud cover's top wall contacts the cookware bottom while the thermostat is mounted on its lower surface, creating a reliable thermal conduction path. This intermediary structure resolves the contradiction by enabling accurate temperature measurement without requiring complex direct coupling mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the thermostat contacts the cookware directly, then the temperature correlation improves, but radiative heat transfer from the coil causes early tripping

Engineering Contradiction:

Improvetemperature correlation accuracyVSAvoidradiative heat transfer interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the thermostat from direct exposure to radiative heat by mounting it on the lower surface of the shroud cover, away from the heating coil. The shroud cover acts as a thermal barrier that blocks radiative heat while maintaining conductive heat transfer from the cookware to the thermostat. This separation resolves the contradiction by eliminating harmful radiative interference while preserving accurate temperature measurement.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If the coil and cookware have poor contact, then the system is easier to assemble, but the thermostat trips early due to radiative heat transfer

Engineering Contradiction:

Improveassembly easeVSAvoidthermostat tripping accuracy

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The shroud cover serves as a mediator that ensures reliable thermal contact between the cookware and thermostat regardless of coil-cookware contact quality. By mounting the thermostat on the shroud cover rather than requiring direct coil-thermostat contact, the system achieves reliable temperature sensing without complex alignment requirements, resolving the contradiction between assembly ease and tripping reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration improves the accuracy of temperature measurement by reducing the impact of radiative heat transfer, leading to enhanced performance and reliability of the cooktop appliance by ensuring better contact and conductive heat transfer between the utensil and the thermostat.

Implementation Method 1

electric resistance heating coil assembly

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

enhancing contact (e.g., with a utensil on a heating element) or conductive heat transfer from a utensil to a thermostat

Methodology Applied

Scientific EffectConductive heat transfer: Conduction (thermal)

Implementation Method 3

radiative heat transfer from the heating element

Methodology Applied

Scientific EffectRadiative heat transfer: Thermal Radiation

Data Source

PatentUS11516890B2Cooktop appliance and heating element having a thermally isolated thermostat

Publication Date: 2022.11.29 HAIER US APPLIANCE SOLUTIONS INC

AI summary

A cooktop appliance or heating coil assembly may include a heating element, a shroud cover, a thermostat, and a spring bracket. The shroud cover may be disposed within the heating element. The shroud cover may include a top wall defining an upper surface and a lower surface. The thermostat may extend vertically between a distal end and an interior end below the distal end. The distal end may be disposed against the shroud cover at the lower surface. The thermostat may be connected in series between the first and second coil sections of the spiral wound sheathed heating element. The spring bracket may be disposed against the shroud cover at the lower surface and bias the shroud cover upward.