Sandwich Injection-Molded Cosmetic Brush with Single Injection Point
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Solution Overview
Problem
Conventional two-component injection molding processes for cosmetics units, such as brushes, result in products with multiple injection points and mold separation impressions, affecting application function and visual aspects, and require complex mold designs with multiple cavities.
Innovation Solution
A sandwich injection-molding process where a first inner plastic component is injected through a single joint point into a second outer plastic component, ensuring a gap-free connection and precise contour matching, allowing for a single injection point and simplified mold design, while achieving a reliable axial fixation and improved design through the use of different material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional two-component injection molding processes are used with multiple injection points, then different material components can be molded, but multiple injection points and mold separation impressions are created which affect application function and visual aspects
Solution Approach 1:
The patent merges multiple injection points into a single injection point by using a common sprue that distributes material to both components. The first and second injection points are combined into one injection system, eliminating multiple injection points and their associated mold separation impressions on the product surface.
Solution Approach 2:
The patent implements nesting by having the first injection-molded component partially or completely enclosed by the second injection-molded component. The first component is nested within the second component, allowing both materials to be molded in a single cavity system with a single injection point, thereby simplifying mold design and improving surface quality.
2Productivity
If multiple mold cavities are used for different material components, then production capacity increases, but the number of injection points and mold separations increases
Solution Approach 1:
The patent combines multiple mold cavities into a single cavity system where both the first and second components are molded simultaneously in one cavity. This single-cavity approach maintains high production capacity while eliminating the need for multiple separate injection points and reducing mold separation impressions that would occur with multiple cavities.
Solution Approach 2:
The single mold cavity serves multiple functions by simultaneously molding both the first and second components with different material properties. The cavity is designed to accommodate both components and their respective injection paths, making the mold system universal for producing the complete two-component cosmetic applicator in one operation.
3Reliability
If fixing caps or undercuts are added to fix the bristle body axially, then axial fixation is achieved, but device complexity and constructional changes increase
Solution Approach 1:
The patent merges the fixation function into the injection molding process itself by designing the first component with an integrated fixation geometry that engages with the second component. The fixation structure is formed during injection molding rather than requiring separate fixing caps or additional undercut features, thereby achieving reliable axial fixation without increasing device complexity.
Solution Approach 2:
The injection-molded components are designed to self-fixate axially through their own geometries formed during the molding process. The first component's shape and the second component's enclosing structure create inherent mechanical interlocking that provides axial fixation without requiring external fixing elements, allowing the product to fix itself during manufacturing.
Data Source
AI summary
The part of a cosmetics unit is an applicator in the form of a brush (1). It is implemented as a sandwich injection-molded part consisting of two different plastic component s (9a, 11a). A first inner plastic component (11a) is injected by means of a single joint injection point (14) into a second outer plastic component (9a). The first inner plastic component (11a) and the second outer plastic component (9a) precisely rest against each other everywhere with regard to their contours. A connecting area is formed, so as to be free of gaps everywhere, between the first inner plastic component (11a) and the second outer plastic component (9a). The second outer plastic component (9a) completely encloses the first inner plastic component (11a), with the exception of the injection point (14). The sandwich injection-molded part (1) has a total weight of at most 10 g.