Vibration Compensation in Power Toothbrush Actuators
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Solution Overview
Problem
Conventional power toothbrushes with resonant drive systems experience noticeable vibrations in the handle due to reaction torque, causing discomfort and inefficiency in energy transfer, as existing solutions like increasing mass moment of inertia or using nodal spring arrangements are ineffective or complex.
Innovation Solution
A power toothbrush design featuring a handle with a stator and rotor that move in opposing directions, connected by springs with a ratio of spring constants matching the moments of inertia, eliminating net torque on the housing and thus reducing handle vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stator portion of the actuator and/or the resonant spring are mechanically attached to the housing for mounting purposes, then the actuator can be securely mounted, but reaction torque acts on the toothbrush housing causing noticeable vibration and discomfort
Solution Approach 1:
The patent segments the spring connection into two separate spring elements: a first spring element connecting the stator to the housing, and a second spring element connecting the resonant mass to the housing. This segmentation allows independent optimization of each spring's properties to balance mounting stability with vibration reduction.
Solution Approach 2:
The patent changes the parameters of the spring elements by specifying different spring constants (k1 and k2) with a specific ratio relationship to the moments of inertia. By adjusting these spring constants and their ratio, the system achieves both secure mounting and minimized reaction torque transmission to the housing.
2Object-affected harmful factors
If the mass moment of inertia of the housing is increased to reduce vibration, then vibration resistance improves, but the handle diameter remains small preventing significant mass addition
Solution Approach 1:
Instead of changing the mass parameter of the housing, the patent changes the spring constant parameters (k1 and k2) of the connecting elements. By adjusting these stiffness parameters and their ratio, the system achieves vibration reduction without adding mass to the handle.
3Object-affected harmful factors
If a nodal spring arrangement is used to decrease vibration, then vibration is reduced, but the structural complexity increases and the stator remains connected to the handle causing continuing vibration
Solution Approach 1:
The patent uses segmentation by dividing the spring connection into two separate spring elements with different connection points and functions, achieving vibration reduction through a relatively simple segmented structure rather than a complex nodal spring arrangement.
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 significantly reduces handle vibration, enhancing user comfort and cleaning efficiency by ensuring all actuation energy is directed to the teeth, rather than being dissipated as vibration.
Implementation Method 1
a first spring element or assembly having a first spring constant connecting the stator to the first housing portion or element fixed to the housing; and a second spring element or assembly having a second spring constant between and connected to the brushhead rotor portion and the second housing portion
Data Source
Figure 1~3
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Figure 7~8
AI summary
A power toothbrush having a vibration compensation system, the toothbrush including a toothbrush housing(72), and an actuator which includes a stator(74)having a first moment of inertia and a rotor (76) having a second moment of inertia, at the end of said rotor is mounted a bristle member. A first spring element (86) having a first spring constant connects the stator to the housing, while a second spring element(88) having a second spring constant connects the rotor to the housing, wherein the ratio of the first and second spring constants is substantially the same as the ratio of the first and second moments of inertia.