Density-Gradient Foam Earplug for Push-to-Fit Insertion
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Solution Overview
Problem
Push-to-fit type earplugs are costly and pose manufacturing challenges, despite their desirable characteristics.
Innovation Solution
An earplug made entirely of closed-cell, slow-recovery foam with a sound attenuating portion and a semi-rigid stem portion, where the stem portion has a greater density than the sound attenuating portion, and the two are chemically bonded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If push-to-fit type earplugs are manufactured using traditional multi-material construction, then the stem portion achieves sufficient stiffness for easy insertion, but the manufacturing cost increases and manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by varying the density of the foam material across different portions of the earplug. The stem portion uses higher density foam (greater than 1.5 times the density of the sound attenuating portion) to achieve the required stiffness for easy insertion, while the sound attenuating portion uses lower density foam for comfort. This density gradient is achieved through controlled foaming processes during molding, eliminating the need for multi-material construction and reducing manufacturing complexity.
Solution Approach 2:
The patent uses a composite foam structure where a single foam material exhibits different density characteristics in different regions. The foam body comprises a stem portion and a sound attenuating portion made from the same base material but with different cell densities, creating a functionally composite structure that provides both stiffness and comfort without requiring multiple materials or assembly steps.
2Ease of operation
If push-to-fit type earplugs are manufactured using traditional multi-material construction, then the stem portion achieves sufficient stiffness for easy insertion, but the device complexity increases
Solution Approach 1:
The patent merges the stem portion and sound attenuating portion into a single integrated foam body without separate components or interfaces. The transition between the stiff stem and soft sound attenuating portion is achieved through a gradual density gradient within the continuous foam matrix, eliminating the need for bonding interfaces, seals, or assembly operations between different materials.
Solution Approach 2:
The patent uses continuous parameter changes in foam density to create distinct functional zones within a homogeneous material structure. The density transitions smoothly from the stem portion to the sound attenuating portion, providing a gradient structure that maintains structural integrity while achieving the desired mechanical property differentiation without increasing device complexity.
3Ease of manufacture
If uniform density foam is used throughout the earplug, then manufacturing is simplified, but the stem portion lacks sufficient stiffness for push-to-fit insertion
Solution Approach 1:
The patent applies local quality by creating region-specific density characteristics within the foam body. The stem portion is formulated with higher density foam to provide localized stiffness and structural support for push-to-fit insertion, while the sound attenuating portion uses lower density foam for comfort and conformability. This localized differentiation is achieved through controlled foaming parameters during the molding process.
Solution Approach 2:
The patent implements parameter changes by varying the foam density parameter across different spatial regions of the earplug. The stem portion maintains a density greater than 1.5 times that of the sound attenuating portion, creating the necessary stiffness gradient. This is accomplished through controlled cell formation and gas distribution during the foaming and curing process.
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
The solution provides a cost-effective and easily manufactured push-to-fit earplug that is comfortable to wear and effective in providing hearing protection, with the stiff stem facilitating easy insertion and the soft sound attenuating portion ensuring comfort.
Implementation Method 1
slow-recovery foam
Implementation Method 2
The sound attenuating portion is chemically bonded to the stem portion.
Data Source
Figure 1~3D
Figure 4A~5
AI summary
A push-to-fit type earplug (100) including a sound attenuating portion (113) and a semi-rigid stem portion (114) having a relatively greater stiffness than the sound attenuating portion is disclosed. The sound attenuating portion and stem portion are made of a closed-cell, slow- recovery foam.