Liquid Heating Vessel Control Using Electromagnetic Switching
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Solution Overview
Problem
Electronic controls in liquid heating vessels are expensive due to complex logic circuitry and solid-state components, limiting their market adoption compared to conventional thermo-mechanical controls.
Innovation Solution
A liquid heating vessel using an electromagnetic switch in combination with electronic control, employing a thermistor for temperature sensing, and a secondary heating element for keep-warm functionality, which simplifies the control circuitry and reduces costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electronic control means are used in liquid heating vessels, then functionality and temperature control precision are improved, but cost and device complexity increase significantly
Solution Approach 1:
The control system is segmented into distinct functional modules: electromagnetic switch for power control, thermistor for temperature sensing, and microprocessor for logic control. This modular segmentation allows each component to perform its specific function efficiently, reducing overall system complexity while maintaining precise temperature control capability
Solution Approach 2:
An electromagnetic switch is introduced as an intermediary component between the electronic control means and the heating element. This intermediary simplifies the control circuitry by providing reliable on/off switching without requiring complex solid-state switching circuitry, thereby reducing cost and complexity while preserving electronic control functionality
2Ease of manufacture
If electromagnetic switch is combined with electronic control, then cost is reduced, but control reliability may be affected
Solution Approach 1:
The patent combines electromagnetic switch with electronic control means in a hybrid arrangement. The electromagnetic switch provides robust, reliable switching action while the electronic control means provides precise temperature monitoring and control logic. This merging of mechanical/electromagnetic reliability with electronic precision achieves both cost-effectiveness and control reliability
Solution Approach 2:
The thermistor provides continuous temperature feedback to the microprocessor, which monitors the heating process and controls the electromagnetic switch accordingly. This feedback mechanism ensures reliable temperature control by continuously adjusting the heating element power based on actual temperature conditions, maintaining system reliability while using cost-effective components
3Ease of manufacture
If thermistor is used for temperature sensing, then cost is reduced, but temperature measurement range and accuracy may be limited
Solution Approach 1:
The patent selects a thermistor with specific parameters (negative temperature coefficient, appropriate resistance value and tolerance) suitable for the application's temperature range. By optimizing the thermistor parameters and positioning it in thermal contact with the heating element, the system achieves adequate measurement precision for beverage preparation while maintaining cost-effectiveness
4Measurement precision
If heating element is isolated from temperature sensing means, then temperature control accuracy is improved, but heat transfer efficiency may be reduced
Solution Approach 1:
The patent creates a local thermal environment where the thermistor is positioned in close thermal contact with the heating element through thermal conductive material. This local thermal coupling ensures accurate temperature measurement at the heating interface while the overall heating element remains efficiently coupled to the liquid. The localized thermal contact achieves measurement accuracy without significantly compromising heat transfer efficiency
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 hybrid arrangement provides cost-effective electronic control functionality while ensuring safe and efficient temperature management, including preset modes and overheat protection, enhancing user safety and appliance reliability.
Implementation Method 1
the temperature sensing means comprises a thermistor since they are relatively inexpensive, robust and can produce an easily measured signal in the required temperature range
Implementation Method 2
controlling the heater is achieved through operation of an electromagnetic switch rather than through operation of a solid-state device
Implementation Method 3
heating to a temperature of 80-85°C which is suitable for coffee; heating to boiling
Data Source
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Figure 5~6
AI summary
A liquid heating vessel comprises heating means (110) for heating liquid in the vessel, electronic control means (80), electromagnetic switching means (60) for interrupting or reducing power to the heating means (110), and temperature sensing means (26) for providing a signal dependent on the temperature of liquid in the vessel to the control means (80). The control means (80) is arranged to operate the electromagnetic switching means (60) to interrupt or reduce power to the heating means (11) in response to the control means (80) determining that a pre-determined temperature condition has been reached.