Two-Shot Molded Lid-Seal Structure for Air-Tight Vessel Closure
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Solution Overview
Problem
Glass bakeware vessels often lack an air-tight seal, which is a common issue with separate lid systems, particularly those made from rigid plastic materials.
Innovation Solution
A vessel-lid combination with an integrated seal structure and latches, where the lid is fabricated using a two-shot molding technique combining a structurally rigid polymer for the first shot and a thermoplastic elastomer for the second shot to create a unitary structure that provides an air-tight seal when attached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate seal member is used between the lid and container, then an air-tight seal can be achieved, but the device complexity increases
Solution Approach 1:
The patent combines the seal member and lid into a single integrated unitary structure fabricated from rigid plastic material. The seal is formed as an integral part of the lid body through molding processes, eliminating the need for separate seal components and their associated assembly steps, while maintaining the air-tight sealing function.
Solution Approach 2:
The lid structure is designed to perform multiple functions simultaneously: it provides structural support for the lid body, incorporates the sealing function through an integrated seal member, and enables attachment to the container. This multi-functionality reduces the number of separate components needed in the system.
2Strength
If rigid plastic material is used for the lid, then structural strength is improved, but the ability to provide an air-tight seal deteriorates
Solution Approach 1:
The patent employs composite material structures within the rigid plastic lid, incorporating flexible elements or compliant features into the molded structure. The unitary structure integrates rigid support sections with flexible sealing sections, allowing the lid to maintain structural integrity while achieving air-tight sealing through the integrated seal member designed with appropriate material properties and geometric features.
Solution Approach 2:
The lid structure incorporates different local properties within the integrated seal member: rigid portions for structural support and flexible portions for sealing contact. The seal member is designed with varying wall thicknesses, material densities, or geometric configurations in different regions to provide both structural strength and sealing compliance in the same component.
3Manufacturing precision
If a unitary structure is fabricated using two-shot molding, then manufacturing precision is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The manufacturing process is segmented into two sequential molding shots: first forming the rigid plastic lid body, then overlaying the flexible seal member material. This segmentation allows each material with different properties to be optimized independently in its own molding step, achieving precise integration while managing the complexity of the manufacturing process through standardized two-shot molding techniques.
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 solution ensures a reliable air-tight seal, maintains thermal properties suitable for oven use, and allows for easy stacking and secure latching, enhancing the functionality and durability of the container.
Implementation Method 1
A two-shot molding process is used to form a unitary lid structure with an integrated seal structure. A first polymer material is injected into a mold to form a first structure. The first structure is then overmolded with a second polymer material to form a second structure over the first structure.
Data Source
AI summary
A method for fabricating a lid for attachment to a vessel having an open top surrounded by a peripheral edge portion, includes injection molding from a molten plastic material a first shot structure defining a web portion, a peripheral portion surrounding the web portion; in a second shot procedure, over-molding an elastomeric material different from said plastic material onto the first short structure to form a seal structure portion integrated with the lid portion to form a unitary lid-seal structure, wherein the seal structure portion is permanently adhered to the peripheral portion of the first shot structure, and wherein the seal structure portion is configured to provide an air-tight seal between the lid and a sealing surface portion of the peripheral edge of the vessel when the lid is attached to the vessel.