Electromagnetic Door Lock Pulse Control for Fast Safe Release
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Solution Overview
Problem
Existing safety control systems for electromagnetic door locks in household appliances are complex, costly, and large in size, with potential malfunctions due to TRIAC pulse emissions and prolonged dead times for thermistor cooling, which hinder efficient door release at the end of a cycle.
Innovation Solution
A simplified control system using a microprocessor to generate specific electric pulses for a TRIAC circuit, including first pulses for blocking and second pulses with opposite polarity for releasing, in conjunction with a PTC element to prevent accidental releases and allow nearly instantaneous door opening, utilizing a minimal mechanical design with permanent magnets for pawl positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional safety control system with electromagnet, PTC element, and thermistor is used, then door blocking safety is ensured, but the system becomes complex, costly, and large in size
Solution Approach 1:
The patent extracts the thermal control function (PTC element and thermistor) from the electrical control circuit, separating it into an independent mechanical-thermal subsystem. This allows the electrical control to be simplified while maintaining safety through the dedicated thermal sensing mechanism that physically interrupts the control circuit when overheating occurs.
Solution Approach 2:
The patent introduces a mechanical intermediary system consisting of a pawl, ratchet, and cam mechanism that translates electrical pulse signals into mechanical blocking actions. This intermediary mechanical system provides reliable door blocking without requiring complex electronic control logic, as the mechanical components inherently provide the blocking function through their physical engagement.
2Reliability
If the PTC element is heated to prevent TRIAC malfunctions, then safety against accidental pulses is improved, but door release time is prolonged due to cooling requirement
Solution Approach 1:
The patent applies preliminary action by heating the PTC element in advance during the washing cycle to establish a safety margin before drum stopping begins. This pre-heating ensures that when the drum stops and door release is needed, the PTC element is already at a temperature where it can quickly interrupt any accidental TRIAC pulses, reducing the effective dead time for door release.
Solution Approach 2:
The patent employs periodic heating cycles of the PTC element synchronized with the washing cycle phases. Instead of continuous heating, the system periodically maintains the PTC element at elevated temperatures during critical phases (washing, rinsing) and allows controlled cooling during transition phases, thereby preventing accidental pulses while minimizing the time penalty for door release.
3Ease of operation
If multiple door openings are allowed during a cycle, then user convenience is improved, but safety risks increase if the drum is still rotating
Solution Approach 1:
The patent implements feedback control by continuously monitoring drum rotation speed through the thermistor's temperature response (which correlates with drum speed via air flow) and automatically adjusting the pawl blocking state accordingly. When the drum rotates above a safe threshold speed, the system maintains door blocking; when speed drops below the threshold, the system automatically permits door opening, providing user convenience while ensuring safety through real-time speed-based feedback.
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
The solution provides a cost-effective, compact, and safe control system that allows multiple door openings during a cycle and immediate release at the end of the cycle, preventing accidental releases and ensuring safety by heating the PTC element to inhibit TRIAC malfunctions, while allowing the thermistor to cool before full drum stoppage.
Implementation Method 1
a PTC element arranged in series in the circuit... adapted to substantially interrupt in use the circuit (18)
Implementation Method 2
a blocking pawl controlled by the movement of an electromagnet core
Implementation Method 3
the time needed for the thermistor to cool down
Data Source
AI summary
A safety control system for an electromagnetic door lock of an electric household appliance, wherein a blocking pawl is controlled by the movement of a core of an electromagnet, including a supplying circuit of a coil of the electromagnet, power supplying means to supply electric pulses in the circuit for energizing the coil and a PTC element arranged in series in the circuit; wherein power supplying means are of the type adapted to generate first pulses for taking the pawl to a blocking position and second pulses, having a polarity opposite to the first, for taking the pawl to a releasing position; and including means for determining, according to the parameters of an operating cycle of the electric household appliance, the emission of at least one train of first pulses by the power supplying means, so as to produce the heating of the PTC element.