Backlit Key Assembly Recessed Light Source Thickness Reduction
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Solution Overview
Problem
Conventional backlit key assemblies in handheld electronic devices increase the device thickness due to the mechanical and electronic components required for backlighting, which is problematic for devices designed to have thinner profiles.
Innovation Solution
A key assembly with a recessed light source and flexible printed circuit board within a backing plate, combined with a light diffuser, reduces the overall thickness while maintaining backlighting functionality by positioning the light source lower relative to the backing plate and utilizing a light diffuser to direct light efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional mechanical and electronic components are used for backlighting, then backlighting functionality is achieved, but device thickness increases
Solution Approach 1:
The patent repositions the light source from a conventional planar arrangement to a recessed configuration within the backing plate, utilizing the vertical dimension to reduce overall thickness. The light source is embedded in a recess that extends downward from the backing plate's rear surface, allowing the light path to be optimized without increasing the device's external thickness profile.
Solution Approach 2:
The light source is nested within a recess formed in the backing plate structure itself. This recess acts as a housing that contains the light source and positions it optimally relative to the key assembly, eliminating the need for separate mounting structures that would increase thickness. The flexible printed circuit board is also positioned within this recessed area, nesting multiple components in a space-efficient manner.
2Length of stationary object
If the light source is repositioned lower relative to the backing plate, then thickness is reduced, but light delivery efficiency may be compromised
Solution Approach 1:
The patent introduces a light guide as an intermediary component that transfers light from the recessed light source to the key assembly. The light guide is positioned between the light source and the key, coupling the light output from the recessed LED to the key surface, ensuring efficient light delivery despite the increased distance created by the recessed configuration.
Solution Approach 2:
The patent optimizes the recess dimensions, light source positioning, and light guide geometry to control light propagation parameters. By carefully designing the recess depth, width, and angle, along with the light guide's optical properties, the system maintains high light delivery efficiency while achieving reduced overall thickness. The flexible printed circuit board positioning within the recess also contributes to optimizing the light path geometry.
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 achieves a reduced thickness in backlit key assemblies compared to conventional designs while maintaining effective backlighting, enhancing the device's profile without compromising key functionality or brightness.
Implementation Method 1
a light diffuser positioned opposite the light source having a light incident surface, the light diffuser having at least one light emitting surface, wherein the light diffuser is configured to receive light from the light source when activated and direct the light towards the flexible member to illuminate the flexible member
Data Source
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AI summary
A backlit key assembly (102) having a reduced thickness for an electronic device, and an electronic device having such a backlit key assembly are provided. The key assembly utilizes a local recess (160) in a backing plate (152) of the key assembly to lower the light source (e.g. LED (142)) and flexible printed circuit board (140) relative to the backing plate. The key assembly described herein provides a suitable leading space for the light source while permitting the overall thickness of the key assembly to be reduced compared with conventional backlit key designs.