Laminated Plywood Drum Shell Density Gradient

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Solution Overview

Problem

Conventional drum shells with low-specific-gravity panels enclosed between high-specific-gravity panels suffer from significant vibrational energy loss, leading to rapid attenuation of sound and reduced volume due to internal abrasion and warping issues during manufacturing.

Innovation Solution

A laminated plywood-shell design where single-panels are jointed in decreasing order of density from the center to the outermost portion, with a high-specific-gravity panel at the center and low-specific-gravity panels at the outermost and innermost portions, minimizing vibration suppression and maintaining acoustic characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a single-panel having low specific gravity is enclosed between single-panels having high specific gravity, then the external appearance is maintained and strength is increased, but there is considerable loss of vibrational energy due to internal abrasion

Engineering Contradiction:

Improvestrength of outer surfaceVSAvoidvibrational energy loss

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent inverts the conventional layer arrangement by placing the low-specific-gravity panel on the outer surface instead of enclosing it between high-specific-gravity panels. This reversal eliminates the internal abrasion problem while maintaining structural integrity, as the softer low-density panel no longer contacts the vibrating drumhead from the inside.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies different material properties to different locations: the outer surface uses low-specific-gravity material for vibration freedom, while the inner structural layers use high-specific-gravity material for strength and stability. This localized optimization resolves the contradiction between strength and vibration energy loss.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If a single-panel having low specific gravity is enclosed between single-panels having high specific gravity, then the effects of changes in air temperature and climate are reduced, but the vibration of drum is rapidly attenuated and the volume becomes relatively small

Engineering Contradiction:

Improveresistance to temperature and climate changesVSAvoidacoustic performance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

By inverting the layer arrangement and placing low-specific-gravity panels on the outer surface, the patent eliminates the internal abrasion that causes rapid vibration attenuation, thereby improving acoustic performance while maintaining environmental stability through the layered structure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent uses a composite structure combining low-specific-gravity and high-specific-gravity panels in a specific arrangement. This composite design achieves both environmental stability (through the layered construction) and superior acoustic performance (by positioning low-density panels outward to reduce vibration damping).

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If long thin single-panels are joined in a cylindrical shape, then the shell can be manufactured, but noticeable warping and gaps appear due to drying and aging

Engineering Contradiction:

Improvemanufacturability of shellVSAvoidwarping and gaps

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent divides the shell into multiple laminated plywood panels with specific gravity gradients rather than using single long thin panels. This segmentation reduces the length of individual panels, minimizing warping and gaps during drying and aging while maintaining manufacturability through standardized panel sizes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite laminated construction with panels of varying specific gravity arranged in a gradient pattern. This composite approach improves dimensional stability and reduces warping compared to uniform single-panels, while the lamination process ensures tight joints without gaps.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS8022281B2Shell for drum and drum using the same

Publication Date: 2011.09.20 YAMAHA CORP

AI summary

A shell for drum according to the present invention includes a laminated plywood-panel including a plurality of single-panels having different densities, the plurality of single-panels being jointed in decreasing order of density from a center portion in a thick direction of the laminated plywood-panel toward an outermost portion and an innermost portion, such that a single-panel having a highest density is arranged at the center portion, and single-panels having lowest densities are arranged at the outermost portion and the innermost portion.