Toothbrush Neck Bending and Weld Gap Design
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Solution Overview
Problem
Toothbrushes made from hard materials like polypropylene are prone to brittle fractures, especially in the transition area between the head and neck parts, which can lead to sharp edges and potential user injuries, and inaccuracies in the connection between the carrier plate and the toothbrush body can further compromise the breaking behavior.
Innovation Solution
The method involves bending the neck part relative to the head part immediately after welding, while the materials are still warm, to stretch the molecules in the welding zone and improve fracture behavior, and using a defined gap between the carrier plate and the head part to prevent weld melt penetration, thereby enhancing the mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the carrier plate is tightly fitted into the receiving recess to improve connection strength, then the mechanical strength improves, but the risk of brittle fractures increases due to stress concentration
Solution Approach 1:
The patent applies different connection qualities to different regions: the peripheral region has a tight fit for strength, while the central region has a defined gap to reduce stress concentration. This local differentiation resolves the contradiction between connection strength and fracture resistance.
Solution Approach 2:
The defined gap is pre-designed into the carrier plate or receiving recess geometry before assembly. This preliminary structural arrangement prevents stress concentration and brittle fractures before they can occur during use.
2Area of moving object
If the carrier plate is made larger to improve cleaning surface area, then the cleaning effectiveness improves, but the risk of brittle fractures increases due to larger welding zone
Solution Approach 1:
The patent creates a non-uniform gap structure where the defined gap is strategically positioned in the central region of the carrier plate. This allows the carrier plate to be made larger for better cleaning coverage while the central gap prevents stress concentration in the expanded welding zone, thus maintaining fracture resistance.
3Productivity
If ultrasonic welding is used to quickly attach the carrier plate, then the manufacturing efficiency improves, but the risk of brittle fractures increases due to heat-affected zone
Solution Approach 1:
The patent extracts or removes the problematic heat-affected zone by creating a defined gap in the central region. This gap prevents the ultrasonic welding heat from creating a large heat-affected zone that would lead to brittle fractures, while still allowing efficient ultrasonic welding at the periphery.
Solution Approach 2:
The patent applies different welding characteristics to different regions: the peripheral region undergoes ultrasonic welding for efficient attachment, while the central region with the defined gap experiences reduced thermal influence, preventing brittle fractures in the heat-affected zone.
4Manufacturing precision
If the receiving recess is made smaller to improve precision fit, then the manufacturing precision improves, but the risk of brittle fractures increases due to higher stress concentration
Solution Approach 1:
The patent creates a differentiated geometry where the peripheral region maintains a tight fit for manufacturing precision, while the central region incorporates a defined gap to reduce stress concentration. This local quality differentiation resolves the contradiction between fit accuracy and fracture resistance.
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
This approach significantly reduces the risk of brittle fractures, ensuring the toothbrush remains durable and safe for use, even with transparent plastics, by aligning molecules and preventing plastic deformation in the critical welding area.
Implementation Method 1
a connection process between the carrier plate and the toothbrush body, so that at least part of the material of the carrier plate and/or toothbrush body is melted, and a weld zone is created by means of a material connection
Implementation Method 2
In the warm state, the neck part and the head part are bent relative to one another by a predetermined angle from their original shape in the welding zone between the toothbrush body and the carrier plate and the zone close to the welding. By bending the neck part relative to the head part, the material of the toothbrush body and in particular the welding zone between the toothbrush body and the carrier plate and partly also the zone near the weld in the mechanically highly stressed area, i.e. in the end section of the carrier plate, is stretched against the neck part, which leads to the alignment of the molecules
Implementation Method 3
The connection is made by means of ultrasonic welding
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
In the production of toothbrushes (10), the neck part (32) and the head part (14) are bent relative to each other from the original shape thereof by a predetermined angle (a) in the hot state of the toothbrush body (12). Thereafter, the force applied to the toothbrush body (12) by means of the stretching device (80) in order to bend the toothbrush body is removed so that the toothbrush body (12) can bend back into the original shape thereof. The risk of fractures, in particular brittle fractures, can be greatly reduced by means of said action. The method is advantageous, in particular if the toothbrush body (12) was heated during processing by ultrasonic welding.