Flat Inductive Push-Button Switch for Wear-Free Actuation
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Solution Overview
Problem
Existing pushbutton switches, especially those used in keyboards, face mechanical and electrical wear issues due to snap-action disks on conductor tracks, limiting their reliability and longevity, and contactless inductive switches are not suitable for flat designs.
Innovation Solution
A flat pushbutton switch with a coil made of printed lines and an electrically conductive control element, using a snap disk spring to adjust between positions, generates a contactless switching signal by influencing the coil's inductance, providing a robust and flat structure with an evaluation circuit to ensure reliability and resistance to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a snap disc is used as an electrical contact means, then the switch can be manually actuated, but mechanical and electrical wear occurs on the conductor tracks
Solution Approach 1:
The patent replaces the mechanical contact system with an inductive sensing system. Instead of using a snap disc that physically contacts conductor tracks, the invention uses a coil to generate a magnetic field and detect changes in inductance caused by the snap disc's position. This substitution eliminates mechanical wear while maintaining manual actuation capability through the snap disc's magnetic influence on the coil.
Solution Approach 2:
The patent introduces a coil as an intermediary between the manually actuated snap disc and the switching signal generation. The coil mediates the interaction by converting the mechanical displacement of the snap disc into an electrical signal through inductance changes, thereby eliminating direct mechanical contact between moving and stationary components.
2Reliability
If a contactless inductive switch with a helical spring coil is used, then contact wear is eliminated, but the structure has considerable height
Solution Approach 1:
The patent transitions from a three-dimensional helical spring coil to a two-dimensional flat coil structure. This dimensional change allows the inductive sensing to occur within a planar configuration, dramatically reducing the height requirement while maintaining the contactless operation capability. The flat coil can be integrated into thin substrates or printed circuit boards.
Solution Approach 2:
The patent employs flat coil structures that can be implemented as thin conductive traces on flexible substrates or rigid printed circuit boards. This approach allows the inductive sensing element to be integrated into thin-film constructions, reducing overall switch height while maintaining electrical functionality.
3Reliability
If a keyboard with multilayer printed circuit board and induction coil is used, then contactless switching is achieved, but the design is complex and has considerable height
Solution Approach 1:
The patent combines the snap disc spring and the flat coil into a single integrated structure where the snap disc's outer edge serves as both the actuating element and the control element that influences the coil's inductance. This merging eliminates the need for separate actuating mechanisms and complex multilayer constructions, simplifying the overall design while maintaining contactless switching functionality.
Solution Approach 2:
The snap disc spring serves multiple functions simultaneously: it provides the mechanical snap-action for user input, acts as the control element that modulates the coil's inductance, and functions as part of the switching mechanism. This multi-functionality reduces the number of separate components needed, thereby simplifying the overall device structure.
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 results in a highly reliable, long-lasting, and vandal-resistant pushbutton switch that is insensitive to external interference and can be used in adverse environments, maintaining performance without mechanical wear and offering a flat, compact design.
Implementation Method 1
at least one coil (16), consisting of a printed conductor, to which an electrically conductive control element (23) is assigned, wherein the control element (23) can be moved by means of an actuating element (20) towards and away from the coil (16)
Implementation Method 2
a snap disc spring (19) is effective between the conductor carrier (15) and the actuating element (20)
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
The push-button switch according to the invention has a hermetically sealed sensor coil (16) to which a movable control element (21) is assigned. This control element can be moved closer to or away from the coil by an actuating element, the movement being parallel to the axial direction of the coil (16). The coil (16) is preferably a flat coil, and the control element is an electrically conductive and/or magnetically conductive soft or hard magnetic material, which can be part of the actuating element (20) and/or part of the snap spring (19). An evaluation circuit (26) detects changes in the electrical properties of the coil (16) when the actuating element (20) is moved and generates a switching signal from this.