Overmolding Elastomeric Seal with Rigid Cap for Moisture Resistance
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Solution Overview
Problem
Existing moisture-tight container assemblies face challenges in achieving consistent moisture resistance while maintaining manufacturing cost-effectiveness, particularly due to issues with incorporating elastomeric sealing members that require careful surface interaction to prevent scratching and ensure integrity, which is not feasible with conventional injection molding techniques.
Innovation Solution
A method of overmolding where a harder material is injected onto a softer material by exposing only one surface of the softer material in a mold, allowing the harder material to solidify and couple directly with it, forming a composite component with improved moisture tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an elastomeric sealing member is incorporated into the container design to improve moisture tightness, then moisture resistance is improved, but the manufacturing complexity and risk of surface scratching increase
Solution Approach 1:
The patent combines the elastomeric sealing member and the rigid cap into a single integrated component through overmolding. The elastomeric material is first molded into the cap, then the rigid polymeric material is overmolded directly onto it, creating a unified structure that eliminates assembly steps and reduces manufacturing complexity while maintaining improved moisture resistance.
Solution Approach 2:
The patent uses composite materials by combining elastomeric material with rigid polymeric material in a single component. This composite structure provides both the flexibility and sealing properties of elastomers and the structural integrity of rigid plastics, achieving superior moisture resistance without increasing device complexity.
2Ease of manufacture
If conventional injection molding is used to manufacture containers with hard seals, then manufacturing cost is reduced, but moisture tightness consistency deteriorates
Solution Approach 1:
The patent employs composite materials with an elastomeric sealing member integrated into the cap structure. This combination provides superior moisture tightness consistency while maintaining cost-effectiveness through the overmolding process, which creates a more reliable seal than hard seals alone.
3Ease of manufacture
If harder material is shot first in overmolding process, then manufacturing simplicity is maintained, but the softer material would be displaced and sealing integrity would deteriorate
Solution Approach 1:
The patent inverts the conventional overmolding sequence by shooting the softer elastomeric material first, then overmolding the harder rigid material onto it. This reversal prevents displacement of the softer material while maintaining sealing integrity, as the harder material is injected at controlled temperatures and pressures that allow it to bond to rather than displace the elastomeric layer.
4Reliability
If elastomeric sealing member is added to improve moisture tightness, then moisture vapor transmission is reduced, but standard deviation in moisture tightness increases due to surface scratches
Solution Approach 1:
The patent merges the elastomeric sealing member and rigid cap into a single overmolded component, eliminating the need for separate assembly operations that could cause surface scratches. This integrated manufacturing approach reduces standard deviation in moisture tightness by ensuring consistent seal quality across all containers.
Solution Approach 2:
The elastomeric material acts as an intermediary layer that protects the sealing surface from scratches and defects. Its softer nature allows it to conform to surface variations and provide a reliable seal, reducing the impact of manufacturing variations on overall moisture tightness consistency.
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 results in a container assembly with reduced moisture vapor transmission and tighter standard deviation in moisture tightness, enabling more predictable and cost-effective production with enhanced sealing capabilities.
Implementation Method 1
allowing the second material to solidify and become directly coupled to the first material thus forming a single component
Data Source
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AI summary
A method of over-molding materials includes: providing a first material in a groove in a first portion of a mold such that only a single surface of the first material is exposed to a vacant portion of the mold; providing, via an injection molding process, a second material in a liquid form in the vacant portion of the mold adjacent to, and in engagement with, the first material; and allowing the second material to solidify and become directly coupled to the first material, thus forming a single component. During the method, the entire single surface of the first material is flush with a plane defined by outer surface of the first portion of the mold. The second material has one or both of a greater hardness when solidified than the first material and/or a higher melting temperature than the first material.