Magnetic Push Button Preload for Consistent Dome Switch Tactility
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Solution Overview
Problem
Conventional push button designs face issues with inconsistent tactile feedback due to manufacturing tolerances, leading to rattle and increased costs, complexity, and susceptibility to failure, particularly with dome switches which require precise dimensional accuracy and assembly.
Innovation Solution
A magnetically preloaded push button design that uses a ferromagnetic button cap and retainer with a preload magnet to consistently bias the button post against the dome switch, eliminating the need for pre-depression and allowing for a more forgiving tolerance in manufacturing variations, thus providing improved tactility and reduced rattle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional push button designs are used with dome switches, then compact size and positive tactile feedback are achieved, but manufacturing tolerances cause inconsistent tactile feedback and rattle
Solution Approach 1:
The patent changes the physical state of the button cap from non-magnetic to ferromagnetic, enabling magnetic interaction with the preload magnet. This parameter change allows the system to use magnetic force as a new degree of freedom for controlling button preload, thereby compensating for manufacturing tolerances and achieving consistent tactile feedback without requiring extremely tight dimensional tolerances.
Solution Approach 2:
The patent replaces traditional mechanical preload mechanisms (such as springs or pre-compressed elements) with a magnetic field-based preload system. The preload magnet generates a magnetic field that acts on the ferromagnetic button cap to provide consistent preload force on the dome switch, eliminating the need for complex mechanical preload adjustment mechanisms and reducing sensitivity to manufacturing variations.
2Reliability
If precise dimensional accuracy is required for dome switches, then consistent tactile feedback is achieved, but costs and complexity increase
Solution Approach 1:
The ferromagnetic button cap serves dual functions: it acts as both the structural button component and the magnetic interaction element. The magnetic field automatically adjusts the preload based on the position and properties of the ferromagnetic material, eliminating the need for separate preload adjustment mechanisms or complex assembly procedures. The system self-regulates to provide consistent tactile feedback.
3Force
If conventional preload techniques are used, then dome switch preloading is achieved, but cost and manufacturing difficulty increase
Solution Approach 1:
The patent replaces mechanical preload techniques (such as pre-compressed springs or mechanically pre-loaded structures) with a magnetic field-based system. The preload magnet generates a magnetic field that attracts the ferromagnetic button cap, creating a consistent preload force on the dome switch. This magnetic approach is easier to manufacture because it eliminates the need for precise mechanical pre-loading during assembly and allows for simpler manufacturing tolerances.
4Ease of manufacture
If manufacturing tolerances are relaxed, then production costs decrease, but tactile feedback consistency deteriorates
Solution Approach 1:
By changing the button cap material to ferromagnetic, the system introduces a new controllable parameter (magnetic field strength) that can compensate for variations in other dimensions. The magnetic preload automatically adjusts to maintain consistent tactile feedback even when other manufacturing dimensions vary within wider tolerances, thereby allowing relaxed tolerances without sacrificing 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
The solution achieves consistent tactile feedback across units, reduces key rattle, enhances impact survival, simplifies assembly and field repairs, and lowers costs while minimizing space utilization, by using a preload magnet to maintain a consistent force on the dome switches.
Implementation Method 1
a preload magnet that biases the button post against the dome switch by magnetic force with the ferromagnetic button cap
Implementation Method 2
a ferromagnetic button cap extending through the button aperture with a user interface surface on a top side of the button cap
Data Source
AI summary
Push buttons utilizing dome switches are often preloaded to take up any tolerances in the push button design causing a gap and provide consistent tactile feedback to a user. However, conventional push button preload techniques can be costly and difficult to consistently reproduce during push button manufacturing. A new pre-load design does not require pre-depression of the dome switch to close the gap, which permits a more forgiving tolerance to manufacturing variations.