Piano Action Flange Bushing Structure for Shrinkage-Free Circularity
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Solution Overview
Problem
Existing piano action bushings, including felt, PTFE, and composite designs, fail to maintain precise alignment and durability due to moisture absorption, deformation, and manufacturing challenges, leading to premature wear and unwanted sounds.
Innovation Solution
A wippen or repetition flange bushing made of plastic or composite material with a sleeve member and integral support posts, injection molded to maintain a nearly perfect circular inner diameter and resist deformation during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional felt bushings are used, then they are moisture resistant and easy to manufacture, but they absorb moisture causing deformation and must be replaced every 5-10 years
Solution Approach 1:
The patent uses a composite material consisting of a thermoplastic matrix reinforced with glass fibers. This composite provides both dimensional stability (resisting moisture-induced deformation) and extended lifespan, eliminating the need for frequent replacements while maintaining shape integrity in humid conditions.
Solution Approach 2:
The invention changes the material parameters by selecting a thermoplastic material with specific properties: low moisture absorption, high dimensional stability, and appropriate flexibility. These parameter changes enable the bushing to resist deformation while maintaining operational reliability for extended periods.
2Reliability
If PTFE bushings are used, then they are hydrophobic and do not absorb moisture, but they shrink during injection molding causing the inner diameter to become non-circular
Solution Approach 1:
The glass fiber-reinforced thermoplastic composite minimizes shrinkage during injection molding compared to pure PTFE. The glass fibers act as a structural framework that maintains dimensional accuracy, ensuring the inner diameter remains circular after cooling and solidification.
Solution Approach 2:
The patent incorporates glass fibers specifically to address the shrinkage problem in critical areas. The reinforcement provides local structural support during molding, preventing distortion of the inner diameter while maintaining the hydrophobic properties of the thermoplastic matrix.
3Productivity
If injection molded bushings are used, then manufacturing efficiency is improved, but shrinkage causes deformation and oval-shaped holes
Solution Approach 1:
The glass fiber reinforcement dramatically reduces shrinkage during injection molding, maintaining hole circularity even with high-volume production. This allows the manufacturing efficiency benefits of injection molding to be realized without sacrificing dimensional accuracy.
Solution Approach 2:
The invention optimizes the molding parameters and material composition to minimize shrinkage. The specific thermoplastic formulation with glass fiber content and distribution is designed to maintain dimensional stability during the injection molding process, ensuring precise hole geometry.
4Ease of operation
If soft PTFE bushings are used, then parts align and rotate properly, but the bushings wear quickly and holes become oval
Solution Approach 1:
The glass fiber reinforcement significantly increases wear resistance and structural strength while maintaining the rotational smoothness provided by the thermoplastic matrix. The composite structure prevents the bushing from deforming under load, maintaining circular hole geometry even after extended use.
Solution Approach 2:
The glass fibers are distributed throughout the bushing material to provide localized reinforcement where wear and stress occur. This maintains the softness needed for smooth rotation at the bearing surface while providing overall structural integrity to prevent deformation.
Data Source
AI summary
An injection molded wippen or repetition flange bushing for a grand piano action where the bushing has four supports posts or elongated appendages projecting outward from the outer surface of the sleeve member of the injection molded wippen or repetition flange bushing. The four supports posts help reduce or eliminate shrinkage of the sleeve member during the cooling stage in the manufacturing of the injection molded wippen or repetition flange bushing. This occurs because shrinkage occurs in the four support posts and not in the sleeve member portion of the injection molded wippen or repetition flange bushing. The result is a perfectly straight bushing with an extremely precise and accurate bushing surface that produces perfect wippen or repetition rotation.