Keypad Friction Device for Vibration Noise Reduction
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Solution Overview
Problem
Conventional film-in-plastic (FIP) or in-mould-decoration (IMD) keypads in portable electronic devices are difficult to affix in place, leading to movement and vibration, which can cause unwanted noise or interference during telephone conversations or voice recordings due to radiated audible frequencies entering the device's microphone.
Innovation Solution
A friction device is integrated into the holes of a light guide between the keypad and the circuit board, featuring a grommet or members that apply friction to the actuator posts, limiting their movement and preventing vibration by providing a physical barrier, thus securing the keypad in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FIP or IMD keypads are used without additional securing mechanisms, then the device structure remains simple and manufacturing cost is low, but the keypad becomes difficult to affix in place and may move or vibrate causing noise interference
Solution Approach 1:
The friction device is nested within the light guide structure, specifically utilizing the hole in the light guide to house the friction device. This allows the friction device to be integrated into the existing keypad assembly without adding external components, thereby reducing overall device complexity while still providing vibration reduction functionality.
Solution Approach 2:
The friction device acts as an intermediary element between the actuator post and the light guide hole. It provides a mechanical interface that applies friction to limit the movement of the actuator post, thereby stabilizing the keypad without requiring direct modification of the keypad structure itself.
2Object-affected harmful factors
If the keypad is allowed to move freely for easy assembly, then manufacturing is easier, but the keypad vibrates and radiates audible frequencies that enter the microphone causing unwanted noise
Solution Approach 1:
The friction device is positioned locally at specific points where actuator posts pass through the light guide. By applying friction only at these specific locations rather than across the entire keypad, the solution reduces noise interference at the source of vibration while maintaining ease of assembly through localized rather than global constraints.
3Object-affected harmful factors
If friction devices are added to limit actuator post movement, then keypad vibration is reduced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The friction device utilizes a flexible grommet that can be easily inserted into the light guide hole. This flexible component design simplifies manufacturing compared to rigid alternatives, as the grommet can be elastomeric or rubber-like material that naturally provides friction while being easy to install and accommodate in the assembly process.
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 friction device effectively reduces keypad vibration and noise interference, enhancing the stability and usability of the keypad assembly without compromising tactility, thereby improving the overall performance of portable electronic devices.
Implementation Method 1
The friction device applies friction to at least one side of the actuator post, thereby resisting movement of the actuator post in the direction of actuation
Data Source
AI summary
A friction device, keypad assembly and portable electronic device are disclosed. In one embodiment, there is provided a keypad assembly for a portable electronic device, comprising: a keypad having a number of keys each having an actuator post attached to a back side thereof; a circuit board; a light guide located between the keypad and the circuit board, the light guide defining a number of holes which provide paths for respective actuator posts to travel through to contact respective electrical switches on the circuit board; and at least one friction device located in one of the holes of the light guide, the friction device providing a physical barrier limiting movement of the actuator post in a direction normal to a direction of actuation, the friction device applying friction to at least one side of the actuator post and resisting movement of the actuator post in the direction of actuation.