Two-Stage Roller Curling for Crack-Resistant Container Rims
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Solution Overview
Problem
Conventional curling methods and apparatuses are prone to material cracking and splitting, especially in containers with welded seams or those that have undergone compression during necking or forming operations, as they form curls with large radii that put excessive stress on the material.
Innovation Solution
The apparatus and method involve a two-stage process using first and second sets of rollers with different groove radii to form and modify the curl, where the first set forms a curl with a smaller radius and the second set expands the radius near the top while maintaining the smaller radius at the bottom, reducing material displacement and tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a curl with a large radius is formed using conventional curling methods, then the curl can support valve cup and gasket effectively, but the material is prone to cracking and splitting especially at welded seams
Solution Approach 1:
The curling process is divided into two distinct stages: first forming a preliminary curl with smaller radius, then expanding it to the final larger radius. This segmentation allows the material to undergo gradual deformation rather than sudden large-radius forming, reducing stress concentration and preventing cracking at welded seams while still achieving the required curl support strength.
Solution Approach 2:
The preliminary curl is formed first as a preparatory step before the final curl expansion. This preliminary action creates an intermediate form that distributes material stress more evenly, particularly at critical locations like welded seams, before the final large-radius curl is achieved in the second stage.
2Shape
If compression is applied to the material during prior necking or forming operations, then the container shape is achieved, but the material becomes more susceptible to splitting during subsequent curling
Solution Approach 1:
By dividing the curling operation into two stages, the patent accommodates pre-compressed material from necking operations. The first stage forms a preliminary curl that gradually releases compression stresses, while the second stage completes the curl formation, preventing sudden stress concentration that would cause splitting in previously compressed material.
3Productivity
If a single-stage curling process is used, then the process is simpler and faster, but the material stress is concentrated causing cracking and splitting
Solution Approach 1:
The two-stage curling process segments the forming operation into preliminary curl formation and final curl expansion. While this adds a step to the process, each stage uses optimized roller configurations that maintain high productivity while distributing material stress, preventing cracking and splitting that would require rework and actually reduce overall efficiency.
Data Source
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Figure 3A~3B
AI summary
An apparatus for forming a curl on an article includes a first forming tooling having a first set of rollers mounted on a common head. The first set of rollers has a respective groove having a first groove radius. The apparatus further includes a first rotating turret configured to load the article into the first forming tooling. The apparatus further includes a second forming tooling having a second set of rollers mounted on a common head. The second set of rollers has a respective groove having a second groove radius. The second groove radius is larger than the first groove radius. The apparatus further includes a second rotating turret configured to load the article into the second forming tooling. The apparatus further includes a first transfer star wheel configured to transfer the article from the first rotating turret to the second rotating turret.