Keyboard Device With Concave Surfaces For Stable Contact

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Solution Overview

Problem

Conventional keyboard devices for electronic keyboards experience destabilized electric touch sensing operations due to large contact resistance caused by oblique contact between movable and stationary contacts, resulting from the hammer's circular arc rotation pressing the key switch from an oblique direction, leading to a curved and inclined switch body.

Innovation Solution

A keyboard device with a swingable key and a hammer having a predetermined pressing surface shape, featuring a hollow switch body made of an elastic material with a to-be-pressed surface and multiple movable contacts positioned at different intervals, which come into contact with stationary contacts. The pressing surface and to-be-pressed surface have relatively-concaved shapes to cancel the inclination caused by the hammer's oblique pressing, allowing the movable contacts to face and contact the stationary contacts frontally.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the hammer rotates following a circular arc locus to press the key switch, then the key depression detection is enabled, but the movable contacts contact the stationary contacts obliquely causing large contact resistance

Engineering Contradiction:

Improveelectric touch sensing operation stabilityVSAvoidcontact resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the geometric parameters of the pressing surface and to-be-pressed surface by introducing concave shapes. This parameter modification allows the surfaces to maintain frontal alignment during hammer rotation, ensuring that movable contacts contact stationary contacts perpendicularly rather than obliquely, thereby reducing contact resistance and stabilizing electric touch sensing operations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies curved surfaces by making both the pressing surface and to-be-pressed surface concave in the longitudinal direction of the hammer. This curvature design compensates for the circular arc rotation of the hammer, maintaining parallel alignment between the pressing surface and to-be-pressed surface throughout the rotation, which ensures perpendicular contact between contacts and reduces contact resistance

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Stability of the object's composition

If the pressing surface and to-be-pressed surface have the same shape, then the hammer can press the key switch vertically after contact, but the hammer only maintains vertical pressing for a moment during circular arc rotation

Engineering Contradiction:

Improvepressing direction stabilityVSAvoidduration of vertical pressing

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of moving object

Solution Approach 1:

The patent introduces concave curvature to both the pressing surface and to-be-pressed surface. This curvature design ensures that as the hammer rotates along a circular arc, the pressing surface remains parallel to the to-be-pressed surface throughout the rotation, maintaining vertical pressing direction for an extended duration rather than only momentarily

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Measurement precision

If the switch body is pressed from an oblique direction, then the key depression can be detected, but the switch body curves and inclines causing misalignment of contacts

Engineering Contradiction:

Improvekey depression detection accuracyVSAvoidswitch body alignment

Core Design Contradiction:

Measurement precisionVSShape

Solution Approach 1:

The patent modifies the shape parameters of the to-be-pressed surface by making it concave in the longitudinal direction of the hammer. This parameter change compensates for the oblique pressing caused by hammer rotation, maintaining the switch body in a substantially non-inclined state and ensuring proper alignment between movable and stationary contacts during key depression detection

Inventive Principle:

Principle #35Parameter changes

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 configuration stabilizes the contact state and electric touch sensing operation by ensuring the movable contacts of the switch body contact the stationary contacts effectively, maintaining a constant depression stroke regardless of key depression speed, especially when there are three or more movable and stationary contacts.

Implementation Method 1

a hollow switch body 3a that has a to-be-pressed surface 3b, that is made of an elastic material, and that is attached to the substrate 6 so as to cover the plurality of stationary contacts 3g-1 to 3g-3

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11037542B2Keyboard device for electronic keyboard instrument

Publication Date: 2021.06.15 KAWAI MUSICAL INSTR MFG CO LTD

AI summary

A pressing surface of a hammer and a to-be-pressed surface of a key switch have relatively-concaved shapes in a longitudinal direction of the hammer. When a switch body is pressed by the hammer, an inclination caused by an overall curvature of the switch body that results from the fact that the switch body is pressed by the hammer from an oblique direction is canceled by an inclination of the switch body caused by partial compression and deformation that results from the relatively-concaved shapes, so that movable contacts in the switch body frontally face stationary contacts and come into contact with the stationary contacts, respectively.