Sonic Toothbrush Bristle Stiffness and Oscillation Geometry
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Solution Overview
Problem
Sonic toothbrushes lack a comprehensive understanding of their cleaning behavior, and existing designs often result in inhomogeneous bristle movement or require excessive drive energy, leading to suboptimal cleaning effects and potential gum damage.
Innovation Solution
A brush design featuring bristles with a specific stiffness range (σk from 0.1 MPa to 10 MPa) and a geometric configuration that enables a controlled, two-dimensional 'Figure 8' movement, achieved through a combination of Young's modulus, bristle geometry, and dynamic parameters like bend angle and deflection, optimized for effective cleaning with minimal gum trauma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the brush head rotates around an axis parallel to the bristle direction, then the moving part is small and requires little drive energy, but the bristle movement is inhomogeneously distributed across the bristle field
Solution Approach 1:
Instead of rotating the brush head around an axis parallel to the bristle direction (conventional approach), the patent inverts the approach by oscillating the longitudinal axis itself around a transverse axis. This inversion changes the motion transmission mechanism from peripheral rotation to axial oscillation, achieving homogeneous bristle movement while maintaining low drive energy requirements.
Solution Approach 2:
The patent transitions from one-dimensional rotational motion (brush head rotating around parallel axis) to two-dimensional oscillatory motion (longitudinal axis oscillating around transverse axis). This dimensional change allows all bristles to participate equally in the cleaning action, achieving homogeneous movement distribution across the entire bristle field.
2Stability of the object's composition
If the brush oscillates about a pendulum axis perpendicular to the hand apparatus, then the intensity of movement is homogeneously distributed over the entire bristle field, but relatively large forces occur because the mass of the brush head is relatively far away from the pendulum axis
Solution Approach 1:
Instead of using a pendulum axis perpendicular to the hand apparatus (conventional approach), the patent inverts the axis orientation by using a transverse axis that is perpendicular to the longitudinal axis of the brush. This inversion brings the axis of oscillation closer to the mass center of the brush head, reducing the moment arm and consequently the forces and moments required to achieve homogeneous bristle movement.
3Force
If the hand apparatus has a coupling pin that rotates back and forth around the longitudinal axis, then relatively low forces occur and movement is evenly distributed, but the bristles only carry out a one-dimensional movement
Solution Approach 1:
The patent enhances the one-dimensional oscillation of the coupling pin by adding a second dimension through the oscillation of the longitudinal axis around a transverse axis. This creates a two-dimensional运动 pattern for the bristles, combining the low-force advantage of the coupling pin mechanism with the versatility of multi-directional bristle movement for comprehensive cleaning.
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 design ensures a homogeneous and efficient cleaning effect across the bristle field with reduced gum trauma, suitable for various operating frequencies, enhancing the cleaning performance of sonic toothbrushes.
Implementation Method 1
at least a portion (e.g., the essential part) of the bristles has a value σk in a range from 0.1 MPa to 10 MPa, wherein σk=(π2·E·r4)/(10·L3) with π=number Pi, E=Young's modulus of the bristles, r=half the diameter of the bristle, and L=length of the bristle
Data Source
AI summary
A brush includes an elongated base body having a base portion that provides an adapter for rotationally fixed coupling to a sonic toothbrush drive in order to pivotally oscillate the brush about a base portion longitudinal axis. A bristle support is formed on a head portion of the elongate base body, and bristles extend from the head portion at least substantially perpendicularly. A neck portion connects the base portion and the head portion. The elongated base body bends at a bend angle γ formed by the base portion longitudinal axis and a head portion orientation axis in the range of 7° to 17°. The bristle support has a deflection A in the range of 5% to 15% with reference to a length L of the base body. At least a portion of the bristles has a value σx in the range from 0.1 to 10 MPa.