Electric Toothbrush Refill Coupling Mechanism
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Solution Overview
Problem
Existing electric toothbrush refill-handle coupling mechanisms face issues with secure attachment and easy detachment while minimizing play, and are prone to unintentional disengagement due to radial forces and external pressure, especially in environments with abrasive materials like toothpaste residue.
Innovation Solution
A coupling mechanism featuring a coupling pin on the handle and cantilevered arms with slide and clamp portions on the refill, which engage the pin for a secure and disengageable connection, utilizing resilient deformation to facilitate attachment and wear resistance through suitable material selection for the pin and arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a latching connection is used to secure the refill to the handle, then axial forces are absorbed and the refill is secured against pulling off, but the coupling becomes prone to unintentional disengagement due to external pressure and dirt accumulation
Solution Approach 1:
The coupling mechanism is divided into separate functional elements: the coupling stem with drive shaft, the tubular connecting piece, and the coupling element with latching arms. This segmentation allows each component to perform its specific function optimally while reducing interference between functions.
Solution Approach 2:
The coupling element is nested within the tubular connecting piece, and the drive shaft is inserted through the coupling element. This nested arrangement compactly integrates multiple coupling functions (axial securing, rotational securing, and drive transmission) into a single integrated assembly that attaches to the handle in one operation.
2Force
If the handle neck is made with a non-circular cross-section to absorb radial forces, then radial forces are better absorbed, but the coupling complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The coupling element acts as an intermediary between the simple circular handle neck and the refill, providing the non-circular latching structure needed for radial force absorption without requiring the handle neck itself to be complex. The latching arms with engagement surfaces create the necessary geometric constraint while the handle remains simple.
3Force
If the drive shaft is pushed onto the handle neck and secured by a latching connection, then axial forces are transmitted, but additional securing measures are necessary to prevent unintentional disengagement
Solution Approach 1:
The coupling element merges multiple securing functions into a single integrated component: the latching arms provide axial securing, the engagement surfaces provide rotational securing, and the overall structure works with the drive shaft for force transmission. This eliminates the need for separate additional securing measures.
4Ease of operation
If a bayonet coupling is used to secure the refill, then easy engagement and disengagement are achieved, but radial forces can cause unintentional disengagement
Solution Approach 1:
The latching arms are designed with asymmetric engagement surfaces that allow easy insertion (the arms can flex outward to accommodate the drive shaft) but prevent removal (the engagement surfaces create mechanical interference in the reverse direction). This asymmetric geometry provides easy engagement while preventing unintentional disengagement under radial loads.
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 mechanism provides a firm and secure attachment with minimal play, allowing easy engagement and disengagement, while withstanding wear and abrasive environments, ensuring reliable operation over the expected lifetime of the toothbrush components.
Implementation Method 1
The coupling device comprises a resilient arms, each having a free end and an engagement surface for engaging the coupling pin
Data Source
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Figure 6
AI summary
An electric toothbrush, including a refill connectable to a handle via a coupling device. The handle has a drive mechanism, and the refill has a brush head and a motion transmitter functionally connected to the brush head for driving it. The handle has a coupling stem terminating with a free end and including a coupling pin extending from the stem. The refill includes a generally tubular portion formed by refill walls defining an interior space for accepting the coupling stem of the handle. The coupling device comprises a pair of mutually opposite and resiliently deformable cantilevered arms disposed adjacent to the refill walls in the interior space of the refill. Each of the cantilevered arms terminates with a coupling surface for engaging the stem's coupling pin for secure and disengageable connection between the handle and the refill.