Toothbrush Relief Structure for Injection Molding Quality
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Solution Overview
Problem
Existing toothbrush designs with multiple plastic components face challenges in manufacturing quality due to difficulties in injecting soft plastic around hard components with steep extensions, leading to air pockets, increased manufacturing costs, and reduced strength, while also being prone to streaking and poor adhesive bonds between components.
Innovation Solution
A toothbrush design featuring a relief structure with intermediate high areas and a graded height profile that allows for easier injection of the second component with reduced pressure, preventing air pockets and streaking, and using a thermoplastic elastomer to improve adhesion between hard plastic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If steep extensions are used in the hard plastic component to create structure, then the structural definition is improved, but the injection flow of the soft plastic component is blocked causing air pockets and manufacturing defects
Solution Approach 1:
The patent replaces steep, vertically protruding extensions with a relief structure featuring rounded contours and gradual height transitions. The relief structure has no abrupt vertical walls but rather curved surfaces that guide the soft plastic component's injection flow smoothly, eliminating air pockets while maintaining structural definition through controlled height variations.
Solution Approach 2:
The patent modifies the geometric parameters of the first component's surface structure by transitioning from steep extensions to a relief structure with controlled height profiles. The relief structure maintains height differences for structural definition but uses gradual slopes and rounded transitions that change the flow parameters of the injected soft plastic, allowing complete filling without defects.
2Manufacturing precision
If high injection pressure is used to fill cavities in structured components, then the complete filling is improved, but the first component melts and washes out causing streaking
Solution Approach 1:
The rounded contours and gradual height transitions of the relief structure reduce flow resistance and guide the soft plastic component's injection flow smoothly through the mold cavity. This eliminates the need for high injection pressure, preventing the hot soft plastic from melting and washing out the first component's surface, thus avoiding streaking while ensuring complete cavity filling.
3Ease of operation
If soft plastic is used to improve grip and comfort, then the user comfort is improved, but the adhesive bond to hard plastic is poor and manufacturing costs increase
Solution Approach 1:
The patent applies a soft plastic component selectively only in the grip area of the handle, where user comfort is needed, while leaving other areas with the hard plastic component. This localized application maintains adhesive bond strength in critical areas and reduces overall material costs, while still providing enhanced grip and comfort where required.
Solution Approach 2:
The patent creates a composite structure combining hard plastic and soft plastic components in a two-layer construction. The hard plastic provides structural strength and cost-effectiveness, while the soft plastic layer in the grip area provides enhanced user comfort. The layered composite design optimizes both mechanical properties and user experience.
4Strength
If hard plastic is made very solid to compensate for weak soft plastic strength contribution, then the overall strength is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent concentrates the structural strength requirements in the hard plastic component while applying the soft plastic component only where comfort is needed (grip area). This local differentiation allows the hard plastic to be optimized for strength without requiring excessive solidification throughout the entire toothbrush, simplifying manufacturing while maintaining both strength and comfort.
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 design achieves high manufacturing quality by optimizing the injection process, reducing the risk of air pockets and streaking, and enhancing the bond between components, resulting in a stronger and more cost-effective toothbrush with improved grip and appearance.
Implementation Method 1
a second component made of a thermoplastic elastomer, which covers the first component and adheres to the first component
Data Source
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Figure 2~4
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AI summary
The invention relates to a toothbrush having a head area comprising cleaning elements, a grip area, and a neck area, which connects the head and the grip areas to each other, wherein the toothbrush is configured having a first component made of plastic, and at least one further second component made of plastic, wherein the first component has a relief structure that is covered by the second component. The relief structure comprises high regions having the shortest distance to the outer surface of the second component, and low regions having the greatest distance to the outer surface of the second component, and the relief structure has intermediate regions adjacent to the high and low regions, the distance to the outer surface of the second component of the intermediate regions being between that of the high and low regions.