Electric Toothbrush Head Coupling With Spring Clip Retention
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Solution Overview
Problem
The interface between the drive shaft and the coupling member in electric toothbrushes faces challenges in reliably transferring torque and maintaining axial retention of the brush head, especially under load and during repeated cycles, while allowing for easy removal and installation.
Innovation Solution
A replacement toothbrush head design featuring a sleeve with a coupling element and a spring clip member that includes a flexible bridge portion and a keyed shape to prevent angular rotation, providing a taut fit and user feedback through metal-on-metal contact, ensuring secure attachment and easy removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple interface between drive shaft and coupling member is used, then ease of manufacture is improved, but reliability of torque transfer and axial retention deteriorates
Solution Approach 1:
The interface is divided into separate functional elements: a coupling member with a keyed shape for torque transfer and a spring clip member for axial retention. This segmentation allows each element to be optimized for its specific function while maintaining ease of manufacture through modular assembly.
Solution Approach 2:
The interface combines different material properties: a rigid coupling member with keyed geometry for reliable torque transfer, and a flexible spring clip member for axial retention. This composite approach ensures both reliability and ease of manufacture by leveraging the advantages of each material type.
2Reliability
If a secure attachment mechanism is used to maintain axial retention, then reliability is improved, but ease of operation for removal deteriorates
Solution Approach 1:
The spring clip member provides dynamic axial retention through elastic deformation. During normal operation, the spring maintains constant pressure on the drive shaft for secure attachment. During removal, the spring can be compressed to release the retention force, enabling easy removal while maintaining reliable retention during use.
Solution Approach 2:
The spring clip member changes its physical state between compressed and relaxed conditions. In the relaxed state, it provides strong axial retention. When compressed during removal, it allows easy detachment. This parameter change enables both reliable retention and ease of removal.
3Reliability
If a keyed shape is added to prevent angular rotation, then reliability of torque transfer is improved, but device complexity increases
Solution Approach 1:
The coupling member incorporates a keyed shape with asymmetric geometry that fits into a corresponding keyway in the drive shaft. This asymmetric design prevents angular rotation and ensures reliable torque transfer. The complexity is minimized by using a simple geometric key rather than a complex locking mechanism.
4Ease of operation
If the interface is designed for easy removal, then ease of operation is improved, but reliability of torque transfer under load deteriorates
Solution Approach 1:
The interface separates torque transfer functions (handled by the keyed coupling member) from removal functions (handled by the spring clip member). This segmentation allows the torque transfer mechanism to be robust and load-bearing, while the removal mechanism remains simple and easy to operate.
Solution Approach 2:
The spring clip member acts as an intermediary element between the coupling member and the drive shaft. It provides a reliable mechanical connection for torque transfer under load, while also enabling easy removal through compression. This intermediary component resolves the contradiction by mediating between the opposing requirements.
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 effectively transfers torque and maintains axial retention of the brush head, preventing angular rotation and providing a secure, yet removable, attachment that accommodates tolerances in molded plastic pieces, ensuring reliable operation and user feedback.
Implementation Method 1
the spring clip arms extending over and biased against said sidewall such that a portion of the sidewall is flexed inwardly for axial retention of the drive shaft
Implementation Method 2
the exterior of the coupling element may have a keyed shape that corresponds to a matching keyed shape of the sleeve to prevent angular rotation of the coupling element with respect to the sleeve
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
A replacement toothbrush head includes a tubular sleeve having a brush at one end and a drive shaft receptacle at the opposite end. The receptacle extends into the sleeve from a mouth at a tube end to a shoulder spaced from the mouth within the tube. A coupling member is inserted into the receptacle, and a spring clip is positioned between the receptacle and the coupling member, the spring clip having a base positioned between the shoulder and the distal end of the coupling member and a pair of spring arms overlying the sidewall of the coupling member. At least one of the spring arms engages a flexible region of the coupling member such that the flexible region flexes to engage a drive shaft inserted into the coupling member and retain the replacement head on the drive shaft.