Knob Assembly Joint Design for Cooktop Tolerance Absorption
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Solution Overview
Problem
Existing knob assemblies for cooking appliances face issues with misalignment due to assembly tolerance, leading to degraded appearance quality and operation failures, particularly in composite cooking appliances where multiple burners require precise alignment and operation.
Innovation Solution
A fire power controlling knob assembly with a joint that absorbs positional errors between the knob and valve shafts, allowing independent operation of the knob ring for timer settings and incorporating a Hall sensor for precise rotation sensing, ensuring accurate alignment and operation without direct transfer of assembly tolerance errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the knob is directly connected to the valve shaft, then the structure is simple, but assembly tolerance causes misalignment and operation failure
Solution Approach 1:
A joint component is introduced as an intermediary between the knob and valve shaft. This joint includes a first shaft coupling portion connected to the valve shaft and a second shaft coupling portion connected to the knob shaft, with a joint spring positioned between them. The joint acts as a mediator that absorbs assembly tolerance errors and prevents direct transmission of misalignment to the knob operation mechanism.
Solution Approach 2:
The joint spring is pre-positioned between the first and second shaft coupling portions to provide cushioning before misalignment occurs. This spring mechanism anticipates and compensates for assembly tolerance variations, ensuring smooth operation of the knob despite manufacturing variations in the valve shaft or knob shaft positions.
2Reliability
If the knob structure is made robust to prevent misalignment, then operation reliability improves, but the ability to absorb assembly tolerance is reduced
Solution Approach 1:
The joint mechanism transforms the static rigid connection between knob and valve shaft into a dynamic system with controlled flexibility. The joint spring provides elastic deformation capability, allowing the connection to adapt to assembly tolerance variations while maintaining operational reliability. This dynamic flexibility enables the system to accommodate positional errors without compromising structural integrity.
3Manufacturing precision
If a joint with spring is introduced to absorb tolerance errors, then alignment accuracy improves, but device complexity increases
Solution Approach 1:
The joint structure is segmented into distinct functional portions: a first shaft coupling portion for connecting to the valve shaft, a second shaft coupling portion for connecting to the knob shaft, and a joint spring positioned between them. This segmentation allows each component to be optimized for its specific function while maintaining overall simplicity. The modular design facilitates manufacturing and assembly despite the increased functional complexity.
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 stabilizes the knob operation, improves appearance quality, and enhances user convenience by allowing fine adjustments without separate tools, reducing the risk of gas leakage and improving safety through precise control and error prevention.
Implementation Method 1
a Hall sensor for sensing the amount of rotation of the valve shaft
Data Source
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AI summary
A knob assembly includes a front panel, a knob located at a front side of the front panel and configured to rotate based on operation by a user, a knob shaft that is coupled to the knob and that extends through the front panel, a supporting pipe that receives the knob shaft and that supports the knob shaft, the supporting pipe being configured to maintain a position relative to the front panel, a valve configured to control supply of gas to the appliance, a valve shaft connected to the valve and configured to control the valve to adjust a flow rate of gas based on rotation of the valve shaft, and a joint that couples the knob shaft to the valve shaft and that is configured to transfer at least one of a rotational motion or a linear motion of the knob shaft to the valve shaft.