Core/Sheath Composite Filament for Toothbrushes
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Solution Overview
Problem
Existing toothbrush filaments made of single synthetic resin materials improve stain removal but lack appropriate hardness, durability, and user comfort due to spread-out bristle tips and reduced durability.
Innovation Solution
A core/sheath composite filament with a synthetic resin core and elastomer sheath, featuring a quadrangular cross-section and specific dimensions, enhances stain removal by increasing contact area and friction, while the elastomer reduces irritation and improves pullout strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filament made of single synthetic resin material is used, then the stain removal property is improved, but the hardness is insufficient and durability is reduced
Solution Approach 1:
The invention uses a composite filament structure with a synthetic resin core (providing hardness and structural integrity) and an elastomer sheath (providing stain removal through friction and flexibility). This composite structure resolves the contradiction by combining materials with complementary properties, where the core maintains shape and strength while the sheath enhances cleaning effectiveness.
2Reliability
If a filament made of single synthetic resin material is used, then the stain removal property is improved, but the brush tip surface spreads out and durability is reduced
Solution Approach 1:
The elastomer sheath provides flexibility and friction for effective stain removal, while the synthetic resin core maintains structural integrity and prevents brush tip spread. This composite structure enhances durability by combining the wear resistance of synthetic resin with the flexible cleaning action of elastomer.
3Reliability
If a filament with quadrangular cross section is used, then the contact area is increased for stain removal, but the irritation to gums may increase
Solution Approach 1:
The invention applies different material properties to different parts of the filament: the synthetic resin core provides the quadrangular shape for effective stain removal, while the elastomer sheath provides a softer, more compliant outer surface that reduces irritation to gums and oral tissues. This local differentiation of material properties resolves the contradiction between cleaning effectiveness and comfort.
4Reliability
If the cross section side length is increased to improve stain removal, then the contact area is increased, but the hardness and feeling of use deteriorate
Solution Approach 1:
The composite structure allows the filament to have a larger quadrangular cross-section for increased contact area and stain removal effectiveness, while the synthetic resin core maintains appropriate hardness. The elastomer sheath compensates for any hardness reduction by providing flexible friction-based cleaning action.
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 core/sheath composite filament effectively removes stains, maintains moderate hardness, and enhances user comfort by reducing bristle spread and improving durability through the elastomer's rubber elasticity and frictional resistance.
Implementation Method 1
a sheath integrally covering the core and made of an elastomer... the elastomer reduces irritation and improves pullout strength and durability
Implementation Method 2
the cross section has sides each of which has the length set in the range of 0.14 to 0.30 mm... increases contact area and friction... effectively removes stains
Data Source
Figure 1(a)~1(c)
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
Provided is a core/sheath composite filament for toothbrushes which exhibits excellent hardness, durability and feeling of use when used in toothbrushes, is less prone to falling out when tufted into the tufting plate, and makes it possible to improve stain-removal properties. Also provided is a toothbrush using said core/sheath composite filament. A toothbrush is configured using bundles of bristles configured from core/sheath composite filaments that have a quadrangular cross section in the plane perpendicular to the lengthwise direction and comprise a core (2), which is formed from a synthetic resin fiber, and a sheath (3), which integrally covers the core (2) and is formed from an elastomer that is compatible with the synthetic resin constituting the core (2). Tufts configured from a plurality of the core/sheath composite filaments (1) are tufted in the center portion of a tufting plate.