Metal Cap Double-Layer Liner Sealability and Openability
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Solution Overview
Problem
Existing metal caps with synthetic resin liners face a trade-off between sealability and openability, where improving one property compromises the other, and their manufacturing processes are costly and complex due to the need for additional steps and materials.
Innovation Solution
A metal cap with a double-layer synthetic resin liner, comprising a barrier layer and a sealing layer, is molded using a press molding process where the barrier layer is temporarily locked to the cap body with a weak adhesive, allowing the liner to be integrated without bonding, thus simplifying the manufacturing process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a synthetic resin liner is used to seal the mouth-neck section, then sealability is improved, but openability is impaired making opening difficult and initial opening torque high
Solution Approach 1:
The liner is divided into two separate layers: a barrier layer that provides sealing force against the mouth-neck section, and a cap body contact layer that interfaces with the cap body. This segmentation allows each layer to perform its specific function independently, enabling the barrier layer to maintain high sealability while the cap body contact layer minimizes friction for easy opening.
Solution Approach 2:
Different portions of the liner structure are given different properties: the barrier layer is designed with high sealing characteristics to contact the mouth-neck section, while the cap body contact layer is designed with low friction characteristics to facilitate easy opening. This local differentiation of material properties resolves the contradiction between sealability and openability.
2Strength
If a metal reinforcing plate is used to support the liner, then structural strength is improved, but manufacturing cost increases and production complexity increases due to additional setting steps
Solution Approach 1:
The metal reinforcing plate is completely removed from the structure. Instead, the cap body itself is designed with an integrated rigid structure that provides the necessary support for the liner. This extraction eliminates the additional component and its associated manufacturing steps while maintaining structural strength through the cap body's inherent rigidity.
Solution Approach 2:
The supporting function previously performed by a separate metal reinforcing plate is merged into the cap body structure itself. The cap body is designed to provide both the structural framework and the support for the liner, eliminating the need for a separate reinforcing component and simplifying the manufacturing process.
3Reliability
If a multi-layer liner with hard sheet and soft layer is used, then sealability is improved, but manufacturing cost increases and production steps are extended due to separate insertion required
Solution Approach 1:
The barrier layer and cap body contact layer are combined into a single integrated liner component that is molded as one piece. This merged structure maintains the functional benefits of multi-layer design (sealing barrier plus low-friction contact surface) while eliminating the need for separate insertion steps, thereby improving production efficiency.
Solution Approach 2:
The liner is pre-formed with both the barrier layer and cap body contact layer integrated during the molding process itself, rather than requiring subsequent assembly steps. This preliminary formation of the complete liner structure streamlines production and maintains productivity.
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 enables a metal cap with improved sealability and reduced opening torque, while maintaining cost-effectiveness by integrating the liner within the cap body's manufacturing steps without additional assembly, thus addressing the compatibility and cost issues of previous designs.
Implementation Method 1
a weak adhesive for locking the barrier layer temporarily to the inner surface of the cap body is coated on the inner surface of the cap body
Implementation Method 2
a molten resin for forming a liner is supplied into the cap body to form a barrier layer and a sealing layer by press molding
Data Source
AI summary
A metal cap in which a linear to be held to a cap body and separable from the cap body can be formed by a series of operations for forming the cap body and press molding the liner. The liner of the metal cap has a double-layer structure including a barrier layer on a top panel wall side and a sealing layer on the inner side of the cap body, and the barrier layer is temporarily bonded to the top panel wall with a weak adhesive at the time of molding the barrier layer and separated from the top panel wall by the natural cooling of the barrier layer after molding.