Leaf Spring Drive Train Assembly to Resist Fretting Fatigue
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Solution Overview
Problem
Existing personal care device drive train arrangements, such as those used in electric toothbrushes, are prone to failure due to fretting fatigue and require numerous parts, increasing component and production costs.
Innovation Solution
A 3D-printed metal drive train assembly featuring a plurality of elongated leaf springs symmetrically disposed around the circumference, secured at both ends, with a fixed centrally-located ring and end mounts, reducing the number of components and enhancing resilience to stress and fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a spring is mounted at both ends in a traditional drive train arrangement, then the spring can provide the necessary mechanical support and flexibility, but it increases the number of parts and components required
Solution Approach 1:
The patent combines multiple separate components (mounts, springs, retainers) into an integrated leaf spring assembly where the leaf springs are directly secured at both ends to end mounts that are part of the housing, eliminating the need for separate retainers and reducing overall part count while maintaining mechanical support functionality
2Reliability
If traditional spring arrangements with multiple parts are used, then each part can be optimized for its specific function, but manufacturing costs and production time increase
Solution Approach 1:
The leaf spring assembly integrates multiple functions into unified components where end mounts serve both as structural supports and as attachment points for the leaf springs, reducing the total number of manufacturing operations and assembly steps while maintaining optimized functionality
3Duration of action of moving object
If repeated forces are applied at the interface of clamped ends of the spring, then the spring can perform its oscillating function, but fretting fatigue occurs leading to part failure
Solution Approach 1:
The leaf spring design incorporates a leaf spring retainer that prevents excessive movement and misalignment at the clamped ends, cushioning against the repeated shear forces that cause fretting fatigue before they can damage the spring or mount interfaces
Solution Approach 2:
The patent changes the interface design at the clamped ends by using enlarged areas and specific geometric configurations in the end mounts and leaf spring attachments, which distribute the repeated forces more evenly and reduce stress concentration that leads to fretting fatigue
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 provides a more efficient and stress-resistant drive train assembly with reduced parts, lowering manufacturing costs and increasing durability, while maintaining effective operation of the oral care device.
Implementation Method 1
each of the plurality of elongated leaf springs secured at both ends
Data Source
AI summary
A drive train assembly (22) for an oral care device (10) having a housing (12), comprising: a plurality of elongated leaf springs (50) symmetrically disposed around the circumference of the drive train assembly, each of the plurality of elongated leaf springs secured at both ends; and a ring (46) encircling the plurality of elongated leaf springs, wherein the ring is fixedly connected to each of the plurality of elongated leaf spring assemblies and fixedly connected to the housing of the oral care device.