High-Frequency Laminate Sealing with Variable Power Subregions
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Solution Overview
Problem
In heat-sealing processes for laminates used in packaging, especially for gable top packages, there is a challenge in achieving consistent heat input due to varying numbers of plies in different regions, leading to potential leaks or overheating, which affects the seal quality and shelf life of contents.
Innovation Solution
A method and device that generate a high-frequency alternating electric field at different power levels in distinct subregions of the sealing area, adjusting voltage and frequency based on the number and thickness of plies, with controlled pressure and temperature measurement to ensure targeted heat distribution, using a device with multiple electrodes and a high-frequency voltage supply to manage these parameters effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single power level is used for the entire sealing region, then the device complexity is reduced, but the sealing quality deteriorates due to inconsistent heat input across regions with varying numbers of plies
Solution Approach 1:
The sealing region is divided into multiple subregions (first subregion and second subregion) with different power levels. The high-frequency voltage supply is segmented to provide different power levels to different electrode pairs, allowing customized heat input for regions with varying numbers of plies.
Solution Approach 2:
Different subregions of the sealing region are assigned different power levels according to their specific needs. Regions with more plies receive higher power levels to ensure sufficient heat penetration, while regions with fewer plies receive lower power levels to prevent overheating.
2Productivity
If the sealing time is reduced to increase productivity, then the productivity is improved, but the heat-sealing reliability deteriorates because insufficient heat is generated
Solution Approach 1:
The conventional conductive heating method is replaced with high-frequency dielectric heating. This electromagnetic heating method generates heat directly within the laminate material through dielectric losses, providing rapid and efficient heating that achieves reliable sealing in shorter times.
Solution Approach 2:
The power level parameter of the high-frequency voltage supply is adjusted according to the number of plies in different subregions. By dynamically changing the power level parameter, sufficient heat is generated even during short sealing cycles, maintaining seal integrity while enabling high productivity.
3Temperature
If the power level is increased to ensure sufficient heat for regions with more plies, then the heat input is sufficient, but regions with fewer plies experience overheating
Solution Approach 1:
The sealing region is segmented into subregions with different power levels. The first subregion (with more plies) receives a higher power level to ensure sufficient heat penetration, while the second subregion (with fewer plies) receives a lower power level to prevent overheating and maintain consistent seal quality across all regions.
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 approach ensures consistent and efficient heat sealing across varying laminate thicknesses and numbers of plies, improving the quality and reliability of the sealing process by preventing leaks and maintaining the integrity of the package contents.
Implementation Method 1
the heat be generated by the dielectric losses which occur when the laminate is exposed to a high-frequency alternating electric field on the order of 300-600 MHz in the sealing region
Implementation Method 2
The lost heat is based in particular on an orientation polarization of molecules with dipole properties in the electrically nonconductive material of the carrier layer of the laminate
Implementation Method 3
the heat for heat-sealing can be generated by induction, in that coils are incorporated into the pressing bars which compress the plies of the laminate; these coils induce electrical currents in the metal ply of the laminate and thus heat it
Implementation Method 4
The heat is carried by conduction from the heated metal ply to the adjacent plies of thermoplastic material, which is melted by the heat and thus converted to a fluid state
Data Source
AI summary
A method and a device for heat sealing multiple plies of a laminate from which gable top packaging can be produced, wherein the laminate has a carrier layer made of electrically non-conductive material and a sealing layer made of thermoplastic material on at least one surface of the laminate. To heat seal multiple plies of a laminate in a high-frequency alternating electric field, the alternating electric field is generated by a first lead of an HF voltage supply in a first sub-region of the sealing region and is generated by a second lead of the HF voltage supply, differing from the first lead, in at least a second sub-region of the sealing region, so that a different heat distribution is obtained over the sub-regions of the sealing region.