Apparatus and method for controlling electric burner element input
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Solution Overview
Problem
Traditional electric cooking ranges lack effective safeguards to prevent top burner elements from overheating, which can lead to flashover and kitchen fires, especially when unattended, due to recent regulatory changes that require temperatures to be maintained below 605°F to prevent cooking oil vaporization and combustion.
Innovation Solution
The implementation of a mechanical or cam-based system that limits the rotation of the control knob to prevent excessive current input to the top burner elements, using detent stops or a specially configured cam to ensure the burner cycles on and off at a 50% duty cycle, thereby maintaining temperatures below the flashpoint of cooking oils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the control knob allows full rotation to maximum setting, then the burner element can reach high temperatures for satisfactory cooking, but the element may exceed 605°F and cause cooking oil to vaporize and combust
Solution Approach 1:
The patent applies preliminary action by pre-configuring the rotary switch with a detent stop mechanism that physically limits the control knob rotation to a maximum of 227 degrees. This preliminary structural constraint ensures that even if a user attempts to rotate the knob to maximum, the temperature will not exceed the safe threshold of 605°F, thereby preventing cooking oil vaporization and combustion before the harmful condition can occur.
2Object-affected harmful factors
If a mechanical detent stop is added to limit knob rotation, then the maximum temperature is limited to prevent flashover, but the device complexity increases
Solution Approach 1:
The patent merges the temperature limiting function with the existing rotary switch structure by integrating a detent stop mechanism directly into the switch assembly. The detent stop is positioned within the switch housing to engage with the control knob shaft, combining the limiting function with the existing rotational control mechanism. This merging approach adds safety functionality without requiring a completely separate control system, thereby minimizing the increase in device complexity.
3Object-affected harmful factors
If the rotary switch is modified to limit current input, then the temperature can be controlled below flashpoint, but the ease of operation is reduced due to restricted knob rotation
Solution Approach 1:
The patent applies local quality by providing different operational characteristics at different positions of the control knob. The detent stop mechanism allows free rotation and full current input for temperatures below the safety threshold (knob rotation up to 227 degrees), ensuring easy operation for normal cooking needs. At the local threshold position (227 degrees), the detent stop engages to physically prevent further rotation, thereby limiting current input and preventing overheating. This localized constraint at the critical threshold position maintains ease of operation for the majority of the usable range while preventing harmful conditions.
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 solution effectively prevents overheating of cooking oils, meeting the UL858 standard by ensuring the top burner elements do not exceed 605°F, reducing the risk of flashover and kitchen fires, while allowing for safe and satisfactory cooking.
Implementation Method 1
electric burner elements... controlling the input of electric currents to the top burner elements... limiting the amount of current that passes to the heating element
Data Source
AI summary
An apparatus and method for restricting the rotation of a dial control knob on the high setting of an electric cooking range using one of three methods. The first method adds a detent stop internally to the switch. The second method adds a detent stop externally attaching to the control panel behind the top burner knob. Both of the aforementioned methods are designed to prevent rotation of the control knob to a maximum of 227° rotation. A third limits the on/off cycling of the top element switch while in operation to reduce the overall output of the switch.