Can Cap Skirt Locking Structure for Sealing Member Retention
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Solution Overview
Problem
Conventional caps for sealing can containers face issues where the sealing member may fall off during opening due to negative internal pressure, and forming a vent slit deeply inward can lead to slit damage or cap damage.
Innovation Solution
A cap design with locking portions in the skirt portion that support a sealing member, combined with small and large diameter portions in the skirt, prevents the sealing member from falling off without damaging the skirt, using a manufacturing process that forms these features through a specific tooling method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vent slit is formed deeply inward in the skirt portion to engage the sealing member, then the sealing member engagement is improved, but the risk of crack occurrence at the vent slit end portion increases
Solution Approach 1:
The invention divides the engagement structure into multiple locking portions (first locking portion and second locking portion) distributed around the circumferential direction, rather than relying on a single deep vent slit. This segmentation distributes the engagement load and avoids stress concentration at a single location, preventing crack occurrence while maintaining reliable sealing member engagement.
Solution Approach 2:
The invention creates different types of locking portions with different engagement characteristics - the first locking portion engages the sealing member at a deeper location while the second locking portion engages at a shallower location. This local differentiation allows optimal engagement without requiring any single location to be excessively deep, thereby preventing cracks.
2Reliability
If the sealing member is engaged with a deeply formed vent slit to prevent falling off, then the sealing reliability is improved, but the cap opening torque increases
Solution Approach 1:
By dividing the engagement structure into multiple distributed locking portions around the circumferential direction, the total engagement force is distributed across multiple contact points. This reduces the force concentration and moment arm effect that would otherwise require higher opening torque, while still maintaining reliable sealing member retention.
3Reliability
If the recessed portion is formed deeply in the skirt portion to engage the sealing member, then the sealing member engagement is improved, but the skirt portion may be damaged
Solution Approach 1:
The engagement function is segmented into multiple locking portions distributed circumferentially, so no single recessed portion needs to be excessively deep. Each locking portion provides partial engagement, and their combined effect ensures reliable sealing member retention without over-stressing any single location of the skirt portion.
Data Source
AI summary
A cap includes: a cap body including a top plate portion and a cylindrical skirt portion; a sealing member provided in the cap body separately from the cap body so as to face the top plate portion; a plurality of locking portions arranged in a circumferential direction in the skirt portion, the locking portions protruding inward in a radial direction of the skirt portion and supporting the sealing member; a plurality of small diameter portions arranged between the top plate portion and the locking portions of the skirt portion, the small diameter portions being respectively provided on a top plate portion side of the locking portions in the axial direction; and a plurality of large diameter portions provided adjacent to the small diameter portions in the circumferential direction and having an inscribed circle diameter larger than an inscribed circle diameter of the plurality of small diameter portions.