Thermoforming Thin Plastic Sheets Using Compression Pleating

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Solution Overview

Problem

Conventional thermoforming processes for packaging foodstuff products using thin plastic sheets (less than 140 μm thick) face challenges due to their flexibility and sensitivity to heat, leading to deformation and damage, and fail to maintain the shape effectively while balancing productivity and quality.

Innovation Solution

A forming process that involves creating pleats on the sheet's peripheral portion, pressing it against a mould surface, and welding the pleats to maintain the shape without stretching, using a forming device with a punch and heating elements to prevent elastic return and ensure a hermetic seal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional thermoforming processes are used on thin plastic sheets (less than 140 μm), then the sheets are stretched and deformed, but the sheets become damaged and lose their shape due to flexibility and heat sensitivity

Engineering Contradiction:

Improveshape retentionVSAvoidheat damage and deformation

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The invention changes the fundamental parameter of the forming process from stretching-based thermoforming to compression-based forming. By using a forming device that presses the sheet against a mould surface without stretching, the process accommodates thin sheets (less than 140 μm) that are sensitive to heat and mechanical stress, preventing damage while achieving the desired shape.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the conventional stretching mechanism with a compression mechanism. Instead of pulling and stretching the sheet over a mould, the forming device presses the sheet against the mould surface, eliminating the harmful stretching forces that cause thin sheets to deform and damage.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of substance

If thin plastic sheets are used to reduce material usage, then material consumption decreases, but the sheets become too flexible and sensitive to heat for conventional forming processes

Engineering Contradiction:

Improvematerial consumptionVSAvoidprocess reliability

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The invention enables the use of thin sheets (reducing material consumption) by changing the forming parameter from stretching to compression. This allows thin, flexible sheets to be formed reliably without the process failures that occur in conventional stretching-based thermoforming.

Inventive Principle:

Principle #35Parameter changes

3Shape

If stretching is applied to form the sheet shape, then the sheet conforms to the mould, but elastic return occurs causing the sheet to lose its formed shape

Engineering Contradiction:

Improveformed shapeVSAvoidshape stability

Core Design Contradiction:

ShapeVSStability of the object's composition

Solution Approach 1:

The invention inverts the conventional approach by using compression instead of stretching. By pressing the sheet against the mould surface, the forming device creates the desired shape without inducing elastic stresses that would cause the sheet to return to its original form, thereby ensuring shape stability.

Inventive Principle:

Principle #13The other way round (Inversion)

4Productivity

If conventional thermoforming is used to maintain productivity, then production speed is maintained, but quality standards deteriorate due to sheet damage and deformation

Engineering Contradiction:

Improveproduction speedVSAvoidproduct quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention replaces the stretching-based thermoforming system with a compression-based forming system. This substitution eliminates the quality issues of sheet damage and deformation while maintaining production speed, as the compression process is equally efficient and can be performed in a single step.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 process effectively forms thin plastic sheets into stable, hermetically sealed packages without damaging the material, ensuring the shape is maintained and the product is protected, while maintaining productivity and quality standards.

Implementation Method 1

The process here described, includes: providing a first sheet of wrapping, made of plastic material

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

pressing it against a mould surface

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 3

welding said second sheet on said first sheet along said second, perimetral, portion

Methodology Applied

Scientific EffectWelding: Welding

Data Source

PatentUS11787100B2Process for making a package for foodstuff products

Publication Date: 2023.10.17 SOREMARTEC SA(BE)

AI summary

A process for making a hermetically sealed package, which includes forming a sheet of wrapping made of plastic material, in particular having a thickness of less than or equal to 140 μm. The process envisages: forming on the sheet a first, hollow, portion and a second, perimetral, portion, which delimits at least partially the first portion; inserting the product into the hollow portion obtained in the sheet of wrapping; applying a second sheet of wrapping in contact with the perimetral portion so as to close the hollow portion with the product inside; and welding the second sheet on the first sheet along the perimetral portion. Forming the first sheet includes providing on the second, perimetral, portion a series of pleats of the sheet, which are then sealed.