Illuminated Thumbwheel Switch Light Guide
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Solution Overview
Problem
Illuminated switches, particularly thumbwheel switches, face challenges in maintaining consistent illumination of graphics or symbols over their range of motion due to significant surface movement relative to the backlight, making it difficult to effectively illuminate symbols.
Innovation Solution
A switch assembly comprising a circuit board with a light source, a rotatable thumbwheel knob, a transparent surface for symbols, and a light guide that directs light from the source to the symbol, along with a rack and pinion assembly to maintain constant light source distance and a detent mechanism for tactile feedback, ensuring consistent illumination throughout the switch's motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thumbwheel switch is rotated to change positions, then the switch can control different functions or settings, but the symbol on the switch surface moves significantly relative to the backlight, causing inconsistent illumination
Solution Approach 1:
The light guide is nested inside the rotatable knob assembly, with the transparent surface containing the symbol positioned within the knob structure. This nesting allows the light guide to rotate with the knob while maintaining its internal light-directed geometry, ensuring consistent illumination path regardless of the knob's rotational position.
Solution Approach 2:
The light guide acts as an intermediary component between the backlight source and the symbol on the transparent surface. It redirects and channels light to consistently illuminate the symbol regardless of the knob's rotational position, mediating the relationship between the stationary light source and the moving symbol to maintain illumination consistency.
2Illumination intensity
If the transparent surface is positioned close to the light source for bright illumination, then the symbol is well-lit, but the distance varies during rotation causing inconsistent illumination across the range of motion
Solution Approach 1:
The light guide is designed with a rotational degree of freedom that allows it to dynamically adjust its orientation as the knob rotates. This dynamic design maintains a constant effective distance and angular relationship between the light source and the symbol throughout the range of motion, ensuring consistent illumination brightness regardless of rotational position.
Solution Approach 2:
The light guide's internal geometry and light redirection parameters are specifically designed to compensate for rotational movement. By changing the light path parameters within the light guide structure, the system maintains constant illumination characteristics despite the physical rotation of the assembly.
3Device complexity
If a traditional backlight arrangement is used with a rotating thumbwheel, then the structure is simple, but the symbol illumination becomes inconsistent or lost during rotation
Solution Approach 1:
The light guide function is merged with the rotatable knob assembly itself, rather than being a separate stationary component. The transparent surface with the symbol is integrated into the light guide structure that rotates with the knob, combining the illumination function with the mechanical rotation function in a single integrated assembly.
Solution Approach 2:
The light guide assembly serves multiple functions: it guides and redirects light from the backlight source, contains the transparent symbol surface, and rotates synchronously with the knob to maintain proper orientation. This multi-functionality reduces the need for separate components while ensuring reliable illumination throughout the range of motion.
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 effective and uniform illumination of symbols on thumbwheel switches over their entire range of motion, enhancing usability in low-light environments and providing tactile feedback.
Implementation Method 1
a light guide for directing light from the light source to the transparent surface to illuminate the symbol
Implementation Method 2
a rack and pinion assembly for moving the conductor relative to the contacts when the knob is rotated
Data Source
AI summary
An electric switch assembly comprises a circuit board; a light source mounted on the circuit board; a thumbwheel knob rotatably mounted on the circuit board; a transparent surface that moves with the thumbwheel knob and on which a symbol is applied or formed; and a light guide for directing light from the light source to the transparent surface to illuminate the symbol.