Drop-Action Piano Keystop Rail For Stable Key Operation

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Solution Overview

Problem

Conventional drop action pianos experience instability and delayed key operation due to the first key lifting and prying against the balance pin, hindering smooth performance.

Innovation Solution

A keystop rail is introduced that contacts the pin rear portion of the first key to prevent lift and pry, ensuring stable and smooth operation by maintaining the first and second keys' rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If the first key is supported at the rear end by a balance pin, then the depth of the piano can be reduced, but the key may lift and pry against the balance pin during operation

Engineering Contradiction:

Improvedepth of the pianoVSAvoidstability of key operation

Core Design Contradiction:

Length of stationary objectVSReliability

Solution Approach 1:

The keystop rail is positioned to contact the pin rear portion before the key can lift and pry against the balance pin. This preliminary contact prevents the harmful motion from occurring in the first place, maintaining reliable key operation while preserving the compact depth achieved by rear-end support

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If the keystop rail contacts the pin rear portion to prevent lift, then key operation stability is improved, but resistance to key pressing may increase

Engineering Contradiction:

Improvestability of key operationVSAvoidease of key pressing

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The keystop rail contacts only the pin rear portion at a specific location, providing localized guidance and stability. This localized contact prevents excessive resistance across the entire key mechanism, allowing smooth key pressing while maintaining operational stability

Inventive Principle:

Principle #3Local quality

3Ease of operation

If the first key is allowed to rotate freely, then ease of operation is improved, but the key may pry against the balance pin causing delayed return

Engineering Contradiction:

Improvesmoothness of key operationVSAvoidtimeliness of key return

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The keystop rail acts as an intermediary element between the pin rear portion and the balance pin. It provides gentle guidance during key rotation and return, preventing direct prying contact with the balance pin while maintaining smooth operation through controlled interaction

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250285603A1Piano with drop action

Publication Date: 2025.09.11 KAWAI MUSICAL INSTR MFG CO LTD

AI summary

A piano includes a first key on an upper side rotatably supported at a rear end by a balance pin via a balance pin hole, and pressed by a player, a second key on a lower side rotatably supported at a central portion, the second key a front end of which the first key abuts, an action that is arranged below the second key and includes a whippen that is rotated upward to drive a hammer to perform string striking, a wire material that lifts the whippen in response to press of the first key, and a keystop rail that comes into contact with a pin rear portion of the first key from above and prevents lift of the first key in the vicinity of the balance pin hole to such an extent that the first key does not pry when the first key is pressed.