Piano-style keypad light guide key sheet segmentation
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Solution Overview
Problem
Piano-style keypads for handheld electronic devices face limitations in the number of keys that can be accommodated due to the size constraints of the light guide, which restricts the adherable surface area and radial length of key bodies, affecting reliability and tactile response.
Innovation Solution
A piano-style keypad design featuring a translucent light guide that mounts a key sheet with a resilient base and key caps, where the light guide does not limit the size of the key bodies, allowing for a larger number of keys by providing a sufficient adherable area and radial length, and includes a leg network and islands to resist deformation and support the key sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the light guide is made larger to accommodate more keys, then the number of keys increases, but the adherable surface area of key bodies and radial length of web decrease below reliable dimensions
Solution Approach 1:
The patent divides the keypad into separate modular components: a light guide, a key sheet with resilient web and key bodies, and a key cap layer. This segmentation allows the key sheet to be designed with sufficient adherable area and radial length for reliability, while the light guide can be optimized for light transmission without being constrained by key size requirements.
Solution Approach 2:
The key sheet acts as an intermediary layer between the light guide and the key caps. It receives light from the light guide through translucent key bodies while providing the necessary structural properties (adherable surface area and radial length) that the light guide alone cannot provide.
2Quantity of substance
If key bodies are made smaller to fit more keys in a given area, then key density increases, but adherable surface area decreases below fifteen square millimeters
Solution Approach 1:
By separating the key body structure from the light guide, the patent allows key bodies to maintain adequate size (at least fifteen square millimeters adherable area) even in high-density layouts, while the overall keypad footprint is reduced through efficient spacing and light guide optimization.
3Quantity of substance
If key bodies are made smaller to increase key count, then more keys fit in the area, but radial length of peripheral web decreases below 0.6 millimeters
Solution Approach 1:
The separation of the key sheet from the light guide allows the resilient web to extend sufficiently (at least 0.6 millimeters radial length) around each key body, providing adequate tactile feedback and ease of actuation, while the light guide is optimized independently for compactness and key density.
4Area of stationary object
If the keypad is made more compact to reduce device size, then device portability improves, but the number of usable keys decreases
Solution Approach 1:
The modular architecture allows independent optimization of each component: the light guide is minimized for compactness, while the key sheet provides sufficient structural dimensions for reliability and usability. This enables high key density without compromising the functional requirements of each key.
Solution Approach 2:
The use of a thin, flexible resilient web allows the key sheet to conform to compact dimensions while maintaining adequate radial length around key bodies, enabling high key density in a small area without sacrificing tactile response or reliability.
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
Enables a higher density of keys in a smaller area without compromising reliability or tactile feedback, allowing for full keyboard layouts on handheld devices without increasing their size, while preventing unintended circuit closure.
Implementation Method 1
The light guide is configured to transmit light from a light source, such as a number of LEDs 28 on the substrate 24, to the key sheet 20 to provide illumination of the keys 42
Implementation Method 2
At least a portion of the key sheet 20 is translucent, as is at least a portion of the light guide 16
Data Source
AI summary
An improved piano-style keypad comprises a light guide and a key sheet, with the light guide retaining the key sheet on a substrate, such as a printed circuit board of a handheld electronic device. The keypad is advantageously configured to enable key caps of the keypad to be adhered to key bodies of the keypad in a fashion that provides long-term reliability while still providing keys that can readily actuated and that provide tactile feedback that is desirable to the user.