Membrane Keyboard Shielding Plate Grounding for ESD Protection
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Solution Overview
Problem
Existing membrane keypads in electrical energy transmission and distribution devices face challenges with electrostatic discharge protection and capacitive discharge shifts, leading to unwanted electromagnetic interference and complex assembly processes.
Innovation Solution
A solid shielding plate is arranged directly behind the decorative film, connected to metallic conductor means that provide a low-resistance, mechanically stable path to ground potential, preventing electrostatic discharges and avoiding induction loops, with conductor connecting means like metallic contact bolts ensuring reliable grounding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shielding film with folded edge flaps is used to connect the conductive layer to the shielding plate, then electrostatic discharge protection is provided, but the assembly becomes complex and induction loops are formed causing electromagnetic interference
Solution Approach 1:
The patent extracts the problematic folded edge flap structure from the design and replaces it with a simplified conductor connecting means that directly connects the conductive layer to the shielding plate without requiring complex folding and assembly steps, thereby reducing assembly complexity while maintaining ESD protection functionality
Solution Approach 2:
The patent segments the shielding structure into distinct functional components: a shielding film with conductive layer, a separate shielding plate, and a dedicated conductor connecting means. This segmentation allows each component to be optimized independently and assembled in a simpler, more straightforward manner compared to the integrated folded flap design
2Reliability
If a folded edge flap structure is used to connect shielding layers, then electrical connection is achieved, but unwanted electromagnetic interference occurs due to induction loops
Solution Approach 1:
The patent removes the folded edge flap structure that creates induction loops and replaces it with a direct conductor connecting means that establishes electrical connection without forming closed loops, thereby eliminating the source of electromagnetic interference while preserving the essential electrical connectivity function
3Device complexity
If a solid shielding plate is used instead of folded edge flaps, then assembly is simplified and induction loops are avoided, but additional grounding connections are required
Solution Approach 1:
The patent merges the shielding plate with the housing of the protective device, integrating the grounding function directly into the housing structure. This combination eliminates the need for separate grounding connections and external grounding components, simplifying both assembly and manufacturing while maintaining effective grounding
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
This solution effectively protects the keyboard wiring from electrostatic discharges and capacitive shifts while simplifying the assembly process, reducing the risk of electromagnetic interference and ensuring safe discharge to earth.
Implementation Method 1
the conductor connecting means can be connected to the earth potential, so that a low-resistance, mechanically stable current path to the earth potential is provided by means of the conductor connecting means
Implementation Method 2
a solid shielding plate is arranged directly behind the decorative film, serving as protection against electrostatic discharges
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
To create a membrane keypad (1) for a protective device in the field of electrical power transmission and distribution, comprising a front decorative film (2), a shielding layer arranged behind the decorative film (2), and a printed circuit board (5) arranged behind the shielding layer, which has a central electrode (21, 22) and at least one outer electrode (19) that are at different electrical potentials, wherein a snap switch (24) can be moved from its initial position to its contact position by means of finger pressure, and the snap switch (24) in its contact position rests against the central electrode (21, 22), from which it automatically returns to its initial position when finger pressure is removed, in which it does not contact the central electrode (21, 22), which enables reliable protection against electrostatic discharges and capacitive discharge displacement and which is simultaneously simple in construction and therefore cost-effective, it is proposed thatthat the shielding layer is designed as a shielding sheet (11) which is electrically and mechanically connected to metallic conductor connecting means (14), wherein the conductor connecting means (14) are connectable to earth potential, so that a low-resistance, mechanically stable current path to earth potential is provided by means of the conductor connecting means (14).