Twisted Non-Circular Filaments for Oral-Care Implement Head
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Solution Overview
Problem
Existing oral-care implement tufts with circular cross-sectional filaments have low bending stiffness, leading to reduced plaque removal efficiency and difficulty in accessing interdental and gingival areas, while high stiffness filaments risk gum injury.
Innovation Solution
A head for an oral-care implement featuring tufts with filaments bent around an anchor, having a non-circular cross-sectional area and twisted by 80° to 100°, providing anisotropic bending stiffness for enhanced plaque removal and interdental access without gum injury.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If filaments with circular cross-section are used, then manufacturing is simple and isotropic bending stiffness is achieved, but bending stiffness is relatively low resulting in reduced plaque removal efficiency and poor interdental penetration
Solution Approach 1:
The patent applies asymmetry by changing the filament cross-section from circular to non-circular (polygonal, rectangular, or oval). This asymmetric geometry creates anisotropic bending stiffness where the filament is stiffer in certain directions and more flexible in others, enabling improved plaque removal efficiency and interdental penetration while maintaining manufacturability through standard extrusion processes.
Solution Approach 2:
The patent changes the geometric parameters of the filament cross-section, specifically transitioning from a circular cross-section to non-circular cross-sections with different side lengths or radii. This parameter change directly affects the moment of inertia and bending stiffness characteristics, allowing optimization of cleaning performance without compromising manufacturing simplicity.
2Strength
If filaments with high bending stiffness are used, then plaque removal efficiency is improved, but risk of gum injury increases
Solution Approach 1:
The non-circular cross-section creates direction-dependent mechanical properties. The filament exhibits higher bending stiffness when force is applied perpendicular to the longer dimension, enabling effective plaque removal, while showing greater flexibility when force is applied parallel to the longer dimension, reducing gum injury risk during normal brushing operations.
Solution Approach 2:
The patent implements local quality by creating different mechanical properties in different spatial directions of the same filament. The anisotropic bending stiffness provides locally optimized performance: stiffer response for plaque removal forces and more compliant response for gum contact forces, thereby resolving the contradiction between cleaning efficiency and safety.
3Strength
If filaments with non-circular cross-section are used, then cleaning properties during normal use are improved, but ability to provide adequate removal from gingival margin and interproximal areas is reduced
Solution Approach 1:
The patent applies dynamics by enabling the filament to dynamically adjust its bending characteristics based on the direction and magnitude of applied forces. During normal brushing, the anisotropic stiffness provides strong cleaning action, while during interdental penetration and gingival margin cleaning, the filament can flex more easily in specific directions, adapting to the geometric constraints of these hard-to-reach areas.
Solution Approach 2:
The specific geometric parameters of the non-circular cross-section (such as the ratio of side lengths or radii) are optimized to balance normal cleaning performance with adaptability for interdental and gingival areas. The parameter optimization ensures that the filament maintains sufficient stiffness for plaque removal while having appropriate flexibility for accessing confined spaces.
Data Source
AI summary
A head for an oral-care implement having a longitudinal axis and comprises a bristle carrier having at least one tuft hole and at least one tuft being fixed in said tuft hole by an anchor. The at least one tuft comprises at least one filament having a longitudinal axis and a non-circular cross-sectional area extending in a plane substantially perpendicular to the longitudinal axis. The at least one filament is bent around the anchor so that a first limb and a second limb extend from the bristle carrier. The first limb comprises a first free end, and the second limb comprises a second free end. Each free end is twisted around the longitudinal axis by a twisting angle .alpha. of about 80.degree. to about 100.degree., preferably about 90.degree..