Mains Plug Bimetal Switch Layout for Contact Pin Overheat Detection

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Solution Overview

Problem

Existing mains plugs for vehicle charging devices lack reliable temperature monitoring, as they are complex to manufacture and do not allow for accurate measurement of absolute temperature, relying on temperature gradients which can be misleading.

Innovation Solution

Incorporating thermal bimetallic switches, which are small, inexpensive, and have a specific switching temperature, allowing for reliable temperature monitoring by changing their switch position when exceeding a set threshold, and can be easily integrated into the plug's design without exposing them to mains current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If thermal bimetallic switches are used for temperature monitoring, then measurement precision and reliability are improved, but device complexity increases

Engineering Contradiction:

Improvetemperature monitoring accuracyVSAvoidplug internal structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs inexpensive thermal bimetallic switches that can be easily replaced if needed. These switches are simple mechanical devices with no electronic components, making them cheap and reliable for temperature monitoring without adding significant complexity to the plug structure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The thermal bimetallic switches are designed to change their physical state (bending or breaking) at specific temperature thresholds. This parameter-based switching mechanism provides precise temperature monitoring through a simple binary state change, avoiding complex measurement electronics while maintaining high reliability.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If thermal bimetallic switches are integrated into the plug body, then ease of manufacture is improved, but the switches may be exposed to harmful factors like mains current

Engineering Contradiction:

Improveintegration into plugVSAvoidmains current exposure

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The plug is divided into functionally separate zones: the current-carrying contact pins and the temperature-sensing bimetallic switches. The switches are positioned in the insulating body material away from the conductive paths, creating physical separation between high-voltage areas and sensitive components. This segmentation allows easy integration into the molded plug body while protecting the switches from electrical hazards.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The insulating body material serves as an intermediary barrier between the mains current paths and the thermal bimetallic switches. This intermediate layer provides both mechanical mounting for the switches and electrical isolation, protecting them from harmful current exposure while allowing thermal conduction for temperature sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If multiple thermal bimetallic switches are used for each contact pin, then reliability is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvetemperature monitoring securityVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Each contact pin area is equipped with its own dedicated thermal bimetallic switch positioned in close proximity. This localized arrangement ensures that temperature monitoring is specific to each contact point, providing reliable detection of overheating issues without requiring a complex centralized sensing system. The local quality approach simplifies the overall design by making each monitoring unit independent and self-contained.

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 reliable temperature monitoring of contact pins and overheating detection, preventing damage by limiting power consumption when the threshold is exceeded, and can be efficiently manufactured with minimal additional effort.

Implementation Method 1

thermal bimetallic switches, which are small, inexpensive, and have a specific switching temperature, allowing for reliable temperature monitoring by changing their switch position when exceeding a set threshold

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

thermal bimetallic switches

Methodology Applied

Scientific EffectBi-Metallic Strip: Bi-Metallic Strip

Data Source

PatentUS11984275B2Electrical mains plug

Publication Date: 2024.05.14 TMC SENSORTECHN

AI summary

An electrical mains plug having a body formed of an electrically insulating material is described. Two contact pins are arranged parallel to one another and which project out of the body at a first side thereof, and inside the body are connected or can be connected in each case to an electrical conductor which leads out or can be led out of the body at a second side thereof. The thermal bimetallic element is provided as a temperature sensor, said thermal bimetallic element being a constituent part of the thermal bimetallic switch which is associated with at least one of two contact pins. An electrical connection cable suitable therefor and an electrical device connected thereto are also described.