Thermoforming Device With Cooled Inter-Row Thin-Walled Sections
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Solution Overview
Problem
The thermoforming of crystallized PET sheets in multiple rows results in bending and flexing, leading to cracks and deviations in the trimming process, which affects the accuracy and conveyance of containers.
Innovation Solution
A thermoforming device with thin-walled forming means between container rows, incorporating cooling mechanisms to prevent crystallization and maintain flexibility, ensuring no cracks occur during deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the PET sheet is heated to crystallization temperature for heat-set thermoforming, then the containers gain heat resistance, but the PET sheet becomes stiff and cracks when bent or flexed during conveyance to the trimming device
Solution Approach 1:
The patent applies local quality by differentiating the thermal treatment of different regions of the PET sheet. The container portions are heated to crystallization temperature to gain heat resistance, while the scrap portions between container rows are actively cooled to remain below crystallization temperature, maintaining flexibility and preventing cracks during conveyance and trimming operations.
2Stability of the object's composition
If the PET sheet is cooled to prevent crystallization in scrap portions, then flexibility is maintained, but the cooling mechanism increases device complexity
Solution Approach 1:
The patent segments the thermal processing approach by dividing the PET sheet into container portions and scrap portions, applying different thermal treatments to each. The cooling mechanism is segmented into cooling means positioned specifically at the scrap portions between container rows, allowing selective cooling without affecting the crystallization process in container areas.
3Ease of operation
If the PET sheet bends or flexes between container rows during conveyance, then the sheet acts as a buffer for speed adjustment, but cracks occur at the bent sites
Solution Approach 1:
The patent applies preliminary anti-action by proactively cooling the scrap portions between container rows before they undergo bending or flexing during conveyance. This preventive cooling maintains the PET in an uncrytallized, flexible state in these critical regions, counteracting the tendency to crack that would otherwise occur when the sheet bends to serve as a speed buffer.
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
The device prevents cracks and maintains consistent spacing between container rows, allowing accurate trimming and conveyance without deformation-related issues.
Implementation Method 1
the thin-walled forming means includes a cooling means to prevent the thin-walled portion from rising to a crystallization temperature during heat-set thermoforming
Implementation Method 2
when the PET is heated above a crystallization temperature (130° C. for PET), the PET can be crystallized. The crystallized PET has a heat resistance of over 200° C.
Data Source
AI summary
This thermoforming device, which performs thermoforming of a continuously supplied resin sheet to simultaneously mold two or more rows of containers in the feed direction of the resin sheet, has: protruding linear portions of a leading clamp forming thin-walled portions in a direction perpendicular to the feed direction between the two rows of the containers; and protruding linear portions of an upper mold, wherein the protruding linear portions have a cooling means and do not raise the temperatures of the thin-walled portions to a crystallization temperature during heat set thermoforming.