Electric toaster with electromagnetic latch
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Solution Overview
Problem
Existing electric toasters with timer-controlled heating elements risk intensifying fires when toasting items containing sugars and fats, as the heating elements continue to operate independently of the heat load, potentially leading to dangerous fires.
Innovation Solution
An electric toaster design featuring a pair of AC power terminals, a heating element, a toasting carriage movable between ejection and toasting positions, and an electromagnet latched by a timer control circuit, with a first rectifying circuit connected to the heating element and a second rectifying circuit isolated from the heating element, along with thermal overload switches and a microprocessor-controlled switching mechanism to manage power supply and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the heating elements are controlled by a timer independently of the heat load, then the toasting operation is automated and efficient, but the risk of fire intensifies when items containing sugars and fats are burning
Solution Approach 1:
The patent implements a feedback mechanism where a sensor detects the heat load on the heating element and provides this information to the control circuit. The control circuit then adjusts the timer control signal accordingly - extending the heating time when heat load is low (preventing under-toasting) and reducing heating time when heat load is high (preventing fire). This closed-loop feedback system resolves the contradiction by making the automated timer responsive to actual toasting conditions.
Solution Approach 2:
The system enables the toaster to automatically monitor and adjust its own operation through the sensor and control circuit. The sensor continuously monitors the heating element's heat load and the control circuit autonomously modifies the heating duration without user intervention. This self-regulating mechanism eliminates the need for manual fire monitoring while preventing fire hazards, resolving the automation-safety contradiction.
2Device complexity
If a single DC power supply circuit is used for both the control circuit and the electromagnet, then the device complexity is reduced, but the reliability of the electromagnet holding action deteriorates
Solution Approach 1:
The patent divides the power supply system into two independent DC power supply circuits. The first DC power supply circuit exclusively powers the control circuit, while the second DC power supply circuit exclusively powers the electromagnet. This segmentation ensures that the electromagnet's operation is not affected by the control circuit's power consumption or failures, thereby improving reliability while maintaining manageable complexity through modular design.
Solution Approach 2:
The patent introduces an optical coupler as an intermediary between the control circuit and the electromagnet control. The optical coupler isolates the two DC power supply circuits electrically while still allowing control signals to pass through optically. This intermediary protects the electromagnet's power supply from electrical interference and ground loops in the control circuit, enhancing reliability without significantly increasing complexity.
3Reliability
If the electromagnet is always powered to maintain latching, then the latching action is always reliable, but energy consumption increases and continuous operation risk rises
Solution Approach 1:
The patent implements periodic action by powering the electromagnet only during specific phases of the toasting cycle. The electromagnet is activated when the carriage is lowered to the toasting position to maintain the latched state during heating, and is deactivated when the toasting is complete and the carriage returns to the raised position. This periodic operation maintains reliability during critical phases while significantly reducing overall energy consumption compared to continuous operation.
Solution Approach 2:
The system dynamically adjusts the electromagnet's power state based on the carriage position and toasting phase. The control circuit monitors the carriage position and automatically activates or deactivates the electromagnet accordingly. This dynamic control ensures the electromagnet provides reliable latching only when needed (during toasting) rather than operating continuously, optimizing both reliability and energy 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
The design enhances safety and reliability by ensuring the electromagnetic latching is responsive and stable, reducing the risk of fires during toasting by isolating the control circuit from the heating elements and incorporating thermal overload protection.
Implementation Method 1
an electromagnet (17) energised for latching the toasting carriage (20) in the toasting position
Implementation Method 2
a toasting carriage (20) moveable from an ejection position against resilient means (23) to a toasting position
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
A toaster with electromagnetic latch is provided. In the toaster a toasting carriage is latched during toasting by an electromagnet (17) actuated by a timer control circuit (12) and is released when a toasting time has elapsed. A first rectifying circuit (16) is always live and supplies DC current to the timer control circuit (12), and a second rectifying circuit (10) supplies DC current to energize the electromagnet (17) when the toasting cycle is initiated. A first switching module (13) switches AC current to pass through heating elements (38,39,40), while a second switching module (15) isolates the first rectifying circuit (16) from the heating elements (38,39,40). Switches of the first switching module (13) and the second switching module (15) are disposed in an array and are closed by movement of the toasting carriage to the toasting position.