Multi-Component Toothbrush Hollow Body Flap Vent Sealing
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Solution Overview
Problem
Existing injection molding processes for manufacturing multi-component hollow toothbrushes face challenges in preventing the overmolding material from penetrating into the hollow body, as they often require vents that need to be sealed to avoid material leakage.
Innovation Solution
A process involving a first mold bar to form a hollow body with a vent and a flap that can be folded to close the vent, using a living hinge to secure the flap in a position that prevents the second plastic material from entering the hollow body during overmolding, ensuring the vent remains sealed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vents are provided in the hollow body to allow gas or liquid to enter and exit, then the hollow body can be properly formed through injection molding, but the vents allow subsequent overmolding material to penetrate into the hollow body
Solution Approach 1:
A flap is pre-formed as part of the hollow body structure, positioned to cover the vent opening. The flap is molded in an open position during hollow body formation, allowing proper venting, but is designed to be movable to a closed position that seals the vent during subsequent overmolding operations.
Solution Approach 2:
The flap is designed as a movable component with a living hinge, transitioning from an open position during hollow body formation to a closed position during overmolding. This dynamic element allows the system to adapt its state based on the manufacturing stage, enabling both venting and sealing functions.
2Manufacturing precision
If a retractable pin is used to close the vent opening, then the second material can be prevented from penetrating into the hollow component, but the pin must be removed after solidification which leaves the opening exposed
Solution Approach 1:
The external retractable pin is replaced by an integrated flap structure that is molded as part of the hollow body itself. The flap is formed from the same material and remains attached through a living hinge, eliminating the need for separate removable components and ensuring permanent integration with the hollow body structure.
Solution Approach 2:
The living hinge acts as an intermediary element that connects the flap to the hollow body, providing a flexible yet secure attachment. This hinge allows the flap to move between open and closed positions while maintaining a reliable connection, eliminating the need for external pins or adhesives.
3Ease of manufacture
If the vent remains open to maintain the hollow structure, then the hollow body can be properly formed, but the overmolding material can leak into the hollow body
Solution Approach 1:
The flap transitions between two states: open during the hollow body formation stage to allow proper molding and gas escape, then closed during the overmolding stage to prevent material leakage. This periodic state change is achieved through the movable flap design that can be positioned appropriately for each manufacturing phase.
Solution Approach 2:
The flap is pre-formed as part of the hollow body structure during the first molding operation, positioned in the open state to facilitate proper hollow body formation. The flap's presence is established beforehand, and it is then manipulated to the closed position before overmolding begins, preventing material leakage in advance.
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 method effectively prevents the second material from leaking into the hollow body, resulting in a multi-component toothbrush with a securely sealed hollow structure, minimizing material penetration and ensuring the integrity of the hollow body.
Implementation Method 1
a living hinge to secure the flap in a position that prevents the second plastic material from entering the hollow body during overmolding
Data Source
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AI summary
An injection-molding process and an apparatus for making a multi-component hollow article, and the article made thereby. The process comprises molding, from a first plastic material, a hollow body having a wall with at least one vent therethrough and at least one flap molded in an area adjacent to the vent. The flap is molded in a first position in which the vent is open. The flap is hingedly movable from the first position to a second position in which the vent is closed by the flap. After the flap is folded into the second position, the hollow body, including the folded flap, is at least partially overmolded with a second plastic material, wherein the second material is essentially precluded from leaking into the hollow body through the vent. The apparatus comprises a first mold bar for molding a hollow body, a second mold bar for overmolding the hollow body with a second plastic material, and a closing tool for moving, and optionally retaining, the flap in the second position. The resulting article has no second material inside its hollow body.