Elastic Weight Locking in Keyboard Instrument Keys

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Solution Overview

Problem

Conventional methods for attaching weights to keyboard instrument keys made of synthetic resin, such as bonding or insert molding, are time-consuming and labor-intensive, leading to increased manufacturing costs.

Innovation Solution

A pivotally movable synthetic resin key body with a recess that allows an elastically deformable weight, primarily made of rubber or elastic synthetic resin, to be easily attached and locked in place, reducing the need for multiple molds and adhesive application.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If weights are attached to key bodies by bonding or insert molding, then the weights are securely attached to the key bodies, but the manufacturing process becomes time-consuming and labor-intensive

Engineering Contradiction:

Improveweight attachment securityVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The key body is divided into multiple recesses, each capable of receiving and locking a weight independently. This segmentation allows weights to be attached separately to different key bodies simultaneously, improving manufacturing efficiency while maintaining secure attachment through the locking portion mechanism in each recess

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of attaching weights to the top surface of key bodies as in conventional methods, this invention inverts the approach by creating recesses that receive weights from below and lock them in place. The locking portion projects from the recess to prevent weight detachment, achieving secure attachment through a reverse attachment direction

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If multiple types of metal molds are used for insert molding different weight shapes and sizes, then precise weight attachment is achieved, but manufacturing costs increase

Engineering Contradiction:

Improveweight shape and size precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The recess structure with locking portion serves multiple functions: it receives weights of various shapes and sizes, provides elastic deformation space for weight insertion, and locks weights in place. This universal recess design eliminates the need for multiple specialized metal molds, reducing manufacturing costs while maintaining precision through the standardized locking mechanism

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention changes the attachment method from rigid mold-based insert molding to a flexible elastic deformation approach. The weight's elastic material allows it to be compressed during insertion and then expand to lock onto the recess, enabling precise attachment without requiring expensive custom molds for each weight variation

Inventive Principle:

Principle #35Parameter changes

3Strength

If adhesive is applied and cured to bond weights to key bodies, then strong bonding is achieved, but the process takes significant time to complete

Engineering Contradiction:

Improvebonding strengthVSAvoidweight attachment time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The invention replaces the chemical bonding system (adhesive application and curing) with a mechanical locking system. The locking portion of the recess mechanically engages with the elastically deformed weight, providing strong attachment without requiring time-consuming adhesive curing processes, thus eliminating the time loss while maintaining bonding strength

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method enables efficient and cost-effective attachment of weights, allowing for precise adjustment of touch weights across different pitch ranges, similar to those of an acoustic piano, while minimizing manufacturing time and labor.

Implementation Method 1

a weight (3) made of a material whose main component has an elasticity, and attached to the key body in a state received in the recess, wherein the recess has a locking portion formed at an opening edge portion thereof in a manner projecting therefrom such that the locking portion allows the weight to be received into the recess while being elastically deformed

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8921676B2Key for keyboard instrument

Publication Date: 2014.12.30 KAWAI MUSICAL INSTR MFG CO LTD

AI summary

A key for a keyboard instrument, which makes it possible to easily attach a weight to a synthetic resin-made key body while securing a desired touch weight to be given during key depression, and can be manufactured at low costs. The key includes a pivotally movable key body made of a synthetic resin, extending in a front-rear direction, and having a recess open downward, and a weight made of a material whose main component has an elasticity, and attached to the key body in a state received in the recess. The recess has a locking portion formed at an opening edge portion in a manner projecting therefrom such that the locking portion allows the weight to be received into the recess while being elastically deformed when the weight is attached to the key body, and locks the received weight in a state prevented from falling out.