Metal Closure Coating Layout for Cleaner Cut Edges
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Solution Overview
Problem
Existing metal closures for food and beverage containers face challenges in forming particles or hairs at the cut edge due to thick coating layers, which can lead to contamination and non-compliance with food-contact legislation, while also being costly to produce.
Innovation Solution
A reduced number or thickness of coating layers at the cut edge, with selective application of coatings to different regions to optimize properties for corrosion resistance, adhesion, and process durability, ensuring compliance with food-contact regulations and reducing particle formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple thick coating layers are applied to the entire sheet metal surface, then corrosion resistance and product protection are improved, but particle and hair formation during cutting and drawing increases
Solution Approach 1:
The patent applies different coating thicknesses to different regions of the closure. The panel region receives full multi-layer coating for maximum corrosion resistance, while the skirt region has reduced coating thickness. This local differentiation maintains protection where needed while minimizing particle formation during subsequent manufacturing processes.
Solution Approach 2:
The coating application is segmented into different regions (panel and skirt) with different coating thicknesses. The panel region gets complete multi-layer coating while the skirt region receives thinner coating, allowing the system to balance corrosion protection with manufacturing process compatibility.
2Reliability
If coating layers are applied close to the cut edge to maximize coverage, then corrosion protection is improved, but drawing operation stability deteriorates due to uneven coating at the edge
Solution Approach 1:
The patent creates a transition zone near the cut edge where coating thickness is gradually reduced. This local modification ensures that the coating does not interfere with the drawing operation while still providing corrosion protection to the panel region that will be in contact with the product.
Solution Approach 2:
Instead of applying full coating thickness uniformly across the entire blank including the cut edge, the patent applies partial coating action - full thickness to the panel region and reduced thickness to the skirt region near the cut edge. This prevents drawing instability while maintaining adequate protection.
3Manufacturing precision
If un-coated bare metal is left adjacent to the cut edge to facilitate drawing, then drawing operation stability is improved, but contamination risk increases from contact with drawing tooling
Solution Approach 1:
The patent applies coating selectively - the panel region adjacent to the cut edge receives full coating to prevent contamination, while the skirt region has reduced coating to facilitate drawing. This local differentiation resolves the contradiction between contamination prevention and drawing stability.
Data Source
AI summary
A metal closure (1) comprising a panel (10) and a depending side wall (14) terminating in a cut edge (15), the inner surface of the closure having a plurality of coating layers applied (21-27) such that at least one of the coating layers extends to the cut edge and the coating thickness at and in proximity to the cut edge is less than the thickness at one or more other regions of the inner surface.