Eccentric Curl Die for Metal Bottle Neck Precision
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Solution Overview
Problem
The formation of metal bottles requires multiple necking operations to create a smaller opening, leading to work hardening and challenges in achieving precise curl formation due to spring back and tolerances.
Innovation Solution
A process involving a symmetrical curl die eccentrically mounted on a spindle, with a pilot rotating concentrically, progressively forming a curl in the neck of the metal container through multiple steps, including pre-curl and final curl formation, to achieve precise control and minimize spring back.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If multiple necking operations are used to decrease the diameter of the opening in the can, then the opening diameter is reduced, but the metal material becomes work hardened and curl formation precision deteriorates
Solution Approach 1:
The curl formation process is segmented into multiple progressive steps (pre-curl, intermediate curl, final curl) with each step reducing the diameter incrementally. This segmentation allows the metal to be deformed in small increments rather than one large deformation, reducing work hardening effects and improving curl precision.
Solution Approach 2:
The invention uses a dynamic rolling mechanism where rollers move progressively along the neck to form the curl. The rolling action provides continuous, gradual deformation rather than static pressing, allowing the metal to flow more evenly and reducing localized work hardening.
2Length of stationary object
If multiple necking operations are used to create a smaller opening, then the opening size is reduced, but the number of process steps increases
Solution Approach 1:
The invention combines multiple curl formation operations into a single integrated rolling process. The multi-roller system performs pre-curl, intermediate curl, and final curl formation in one continuous operation, eliminating the need for separate process steps while achieving the same dimensional reduction.
Solution Approach 2:
The rolling mechanism serves multiple functions simultaneously: it reduces the opening diameter, forms the curl shape, and controls the metal flow. This multi-functionality consolidates what would traditionally require separate operations into a single universal process.
3Length of stationary object
If traditional multiple necking operations are used, then the opening diameter is reduced, but metal work hardening increases
Solution Approach 1:
The rolling mechanism provides dynamic, continuous deformation that allows metal grains to realign progressively. This dynamic process reduces localized stress concentrations and minimizes work hardening compared to static pressing operations.
Solution Approach 2:
The invention changes the deformation parameters by using gradual, incremental rolling pressure rather than high instantaneous pressure. The rolling speed, pressure distribution, and roller geometry are optimized to minimize work hardening while achieving the required dimensional 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
This method allows for closer tolerances and reduced spring back, enabling a reliable sealing edge with less metal work hardening and fewer steps compared to traditional multiple necking operations, resulting in a more stable and precise curl formation.
Implementation Method 1
providing a symmetrical curl die having a centerline and an opening in said curl die that is off-center from said centerline; placing a spindle through said opening in said curl die so that said curl die is eccentrically mounted on said spindle; rotating said spindle so that said curl die rotates eccentrically around said centerline
Implementation Method 2
progressively engaging said neck of said container with said curl die as said curl die rotates eccentrically around said spindle to progressively form said curl in said neck
Data Source
AI summary
Disclosed is a device and method for forming a curl in a closable container. A process of forming a pre-curl is used, which is followed by a second separate step of forming the completed curl. The two-step process provides for higher tolerances with respect to the shape of the curl that allows the curl to be used as a sealing surface for a recloseable metal bottle. A three-step process provides for even greater tolerances and reduces longitudinal forces by completing the curl using lateral forces. Also, a die curler is disclosed that has an eccentric motion that forms a curl in a single progressive curling process.