Electric Toothbrush Drive Train Fatigue Resistance
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Solution Overview
Problem
Existing power toothbrushes face issues with joint failure and disconnection of moving components due to fatigue, leading to loss of primary function and rendering the device unusable.
Innovation Solution
A drive train assembly with a shaft and shaft interface connected by a connecting element that extends along the outer surface of the shaft, providing a secure and robust connection that prevents disconnection due to fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional connection methods are used for the shaft and drive train, then the device structure remains simple, but joint failure occurs due to fatigue under extreme conditions
Solution Approach 1:
The connecting element is divided into multiple segments extending along the outer surface of the shaft at different positions. This segmentation allows the connection to be distributed across multiple points, reducing stress concentration at any single point and preventing fatigue-induced joint failure while maintaining a relatively simple overall structure.
Solution Approach 2:
The connecting element extends not only axially along the shaft but also radially outward to contact the outer surface of the shaft. This multi-dimensional configuration creates a more robust connection that resists fatigue forces from multiple directions, improving reliability without significantly increasing structural complexity.
2Reliability
If a secure connection is implemented using a connecting element extending along the shaft surface, then joint failure due to fatigue is prevented, but the manufacturing process becomes more complex
Solution Approach 1:
The connecting element is designed to integrate the shaft and drive train components into a single assembled unit. By combining multiple connection functions into one element that extends along the shaft surface, the design achieves secure fatigue-resistant connection while streamlining the assembly process, as the connecting element can be installed in one piece rather than requiring multiple separate fasteners.
3Strength
If the connecting element extends along the outer surface of the shaft, then the connection withstands fatigue forces, but the amount of material and complexity increase
Solution Approach 1:
The connecting element provides enhanced connection strength only where needed - specifically where it contacts the outer surface of the shaft and where fatigue forces are most critical. Rather than uniformly strengthening the entire shaft, the connecting element applies reinforcement locally at the interface between the shaft and drive train, optimizing material usage while achieving the required connection strength.
Data Source
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AI summary
The invention concerns a drive train assembly for an electric toothbrush, comprising a shaft comprising a rear side and a front side, wherein the front side of the shaft is configured for receiving a brush head. The drive train assembly further comprises a drive train comprising a shaft interface configured to receive the shaft, wherein the shaft interface comprises a rear surface and a front surface, wherein the rear side of the shaft is connected with the shaft interface from the direction of the front surface of the shaft interface for connecting with the drive train, a connecting element configured for connecting the shaft with the shaft interface, wherein the connecting element extends at least partially along the outer surface at the rear side of the shaft for connecting the shaft interface and the shaft at the rear side of the shaft. The invention further concerns a toothbrush comprising the drive train assembly and a manufacturing method for manufacturing the shaft and shaft interface assembly.