Thermoformed Screw Cap With Elastic Sealing and Deformation Control
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Solution Overview
Problem
Existing screw caps formed through injection molding or compression molding have complex structures, making it difficult to achieve a thin, lightweight design with reliable liquid-tightness and gas barrier properties, and thermoforming methods often result in plastic deformation during mold removal.
Innovation Solution
A screw cap design featuring an inner side wall with an annular protruding portion and convex portions on the skirt, allowing elastic deformation and preventing plastic deformation during mold removal, while maintaining liquid-tightness through thermoforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If injection molding or compression molding is used to form screw caps with sealing portions and screw portions, then liquid-tightness and sealing performance are achieved, but the structure becomes complicated and weight reduction becomes difficult
Solution Approach 1:
The cap is divided into functionally distinct portions: a sealing portion with an elastically deformable annular protruding portion that presses against the container mouth, and a screw portion with threads for engagement. This segmentation allows each portion to be optimized independently while maintaining overall simplicity
Solution Approach 2:
The sealing portion utilizes the elastic deformability of a thin resin sheet to create an effective seal. The annular protruding portion is formed from the same thin material without requiring additional components, achieving both weight reduction and sealing functionality
2Reliability
If injection molding or compression molding is used to form screw caps, then reliable liquid-tightness is achieved, but it becomes difficult to form thin caps with reduced weight
Solution Approach 1:
The entire cap including the sealing portion is formed from a single thin resin sheet through thermoforming. The elastic deformability of the thin material enables the annular protruding portion to effectively seal the container mouth without requiring thick walls or additional components
Solution Approach 2:
The invention changes the forming method from injection molding or compression molding to thermoforming. This parameter change in the manufacturing process enables the use of thinner materials while maintaining sealing effectiveness through the elastic deformation capability of the thermoformed structure
3Weight of moving object
If thermoforming is used to form caps from thin synthetic resin sheets, then weight is reduced, but plastic deformation occurs during mold removal due to forced removal of the core mold
Solution Approach 1:
The cap is designed with predetermined elastic deformation characteristics that allow it to temporarily expand during mold removal and then recover to its original shape. This preliminary design of elastic recovery capability prevents permanent plastic deformation of the sealing and screw portions
Solution Approach 2:
The invention changes the material state and deformation characteristics by using thermoforming to create a cap with specific elastic properties. The thermoformed structure is designed to exhibit elastic deformation during mold removal rather than plastic deformation, enabling forced removal without damage to critical portions
4Weight of moving object
If the thickness of the top surface is reduced to decrease weight, then weight is reduced, but tightness is inevitably reduced
Solution Approach 1:
The sealing portion utilizes the elastic deformability of thin material to achieve effective sealing. The annular protruding portion is formed from the same thin resin sheet and relies on its elastic recovery to press against the container mouth, decoupling the relationship between thickness and sealing effectiveness
Solution Approach 2:
The invention changes the deformation mode from plastic to elastic, allowing thin-walled structures to maintain sealing pressure through reversible deformation. This parameter change in material behavior enables thin caps to achieve tightness without sacrificing weight reduction
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 cap achieves high sealing performance, reduced weight, and improved productivity by using thermoforming with elastic deformation, preventing deformation of the sealing and screw portions during mold removal.
Implementation Method 1
the inner side wall includes an annular protruding portion having an outer diameter greater than an inner diameter of a container mouth portion to which the screw cap is applied, and is elastically deformable in a cap radial direction
Implementation Method 2
a plurality of convex portions having an amount of protrusion in a radial direction smaller than a height of a screw thread are disposed in a circumferential direction on an inner surface of the skirt portion
Implementation Method 3
a screw cap which includes: a top surface (2); an inner side wall (3) extending upward from an outer peripheral edge of the top surface (2)
Data Source
Figure 1
Figure 2
Figure 3(A)~3(B)
AI summary
The present invention relates to a screw cap that can be formed through thermoforming from a resin sheet, has re-sealing performance through screwing engagement, and makes it possible to achieve liquid-tightness. The screw cap has a drop-lid shape and includes: a top surface; an inner side wall extending upward from an outer peripheral edge of the top surface; and a skirt portion including a screw portion and coupled to the inner side wall through an annular portion extending outward from an upper end of the inner side wall, in which the inner side wall includes an annular protruding portion having an outer diameter greater than an inner diameter of a container mouth portion to which the screw cap is applied, and is elastically deformable in a cap radial direction.