Household Door Contact Monitoring for Sticking Switch Failures
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Solution Overview
Problem
Existing door monitoring systems in household appliances, such as micro pressure switches, suffer from contact sticking issues due to corrosion, uneven contact surfaces, and reduced spring force over time, compromising operational safety.
Innovation Solution
A door monitoring apparatus with separate contact pairs, one on the door and one on a non-movable part, mechanically connecting to form an electrical circuit that reliably detects the door's open or closed state, even with sticking contacts, by ensuring proper contact or separation when the door is closed or opened.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If micro pressure switches are used to monitor the door, then the door state can be detected, but the contacts may stick over time due to corrosion, arcs, and spring fatigue
Solution Approach 1:
The door monitoring system is divided into multiple independent contact pairs (first contact pair and second contact pair) instead of using a single switch. Each contact pair operates independently, so if one contact sticks or fails, the other can still detect the door state reliably. This segmentation eliminates the single point of failure inherent in traditional micro pressure switches.
Solution Approach 2:
A magnetic coupling mechanism is introduced as an intermediary between the door and the monitoring system. The magnetic coupling transfers the door's positional information (open/closed state) to the monitoring contacts without requiring direct mechanical contact between moving and stationary parts. This eliminates the mechanical wear, corrosion, and sticking problems that plague traditional contact-based switches.
2Measurement precision
If the current for detecting closed contact is high, then the detection is reliable, but arcs are formed causing corrosion and contact welding
Solution Approach 1:
A magnetic field is used as an intermediary to detect the door's closed state without requiring high current through the contacts. The magnetic coupling mechanism detects the door position through magnetic field interaction, allowing for reliable detection with minimal current, thereby preventing arc formation and contact corrosion.
Solution Approach 2:
The mechanical contact-based detection system is replaced with a magnetic field-based detection system. Instead of relying on electrical current flowing through mechanical contacts to detect the door state, the system uses magnetic field interaction to detect the door's position, eliminating the harmful arcs and contact wear associated with high-current mechanical switches.
3Reliability
If two micro pressure switches are connected in series, then operational safety is improved, but the system complexity increases and additional monitoring measures are required
Solution Approach 1:
The door monitoring system is segmented into multiple independent contact pairs that naturally provide redundancy. Each contact pair independently monitors the door state, and the system logic evaluates both contacts to determine the door position. This segmentation provides enhanced reliability without requiring complex series connections or additional monitoring circuitry, as each segment operates independently and contributes to the overall safety.
Data Source
AI summary
A household appliance includes a compartment, a door for closing the compartment, a non-movable part, and a door monitoring apparatus including a contact pair which has two contact parts. One of the two contact parts is arranged on the door and the other one of the two contact parts is arranged on the non-movable part of the household appliance.