Plastic-Coated Board Tray Self-Sealing Method

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Solution Overview

Problem

Existing methods for manufacturing plastic-coated board trays struggle to achieve hermetic sealing with a thin plastic coating layer, often resulting in leaks and irregular surfaces due to corner pleats and protrusions.

Innovation Solution

A manufacturing technique where the board layer is thinned or removed in compressed parts, allowing the plastic coating to double-fold and seal itself, creating smooth surfaces for leak-proof sealing and maintaining tray shape.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the plastic coating layer is made thinner to reduce material usage and cost, then the tray's barrier properties and heat sealing capability are improved, but the coating becomes insufficient to level corner irregularities and may result in leaks

Engineering Contradiction:

Improveplastic coating thicknessVSAvoidsealing reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention applies local quality by creating compressed portions at specific locations (corners and sides) where the board layer is thinned or removed, allowing the plastic coating to double-fold and seal locally. This localized modification enables the coating to self-seal without requiring uniform thickness throughout, thus achieving reliable sealing with reduced material usage.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the physical state and configuration of the plastic coating by applying heat during molding to melt and seal the coating in compressed portions. This parameter change (temperature) allows the thin coating to become sufficiently pliable to self-seal and retain its shape, overcoming the limitation of reduced thickness.

Inventive Principle:

Principle #35Parameter changes

2Shape

If corner pleats are created to allow compression and shaping of the tray, then the tray can be formed into the desired shape, but protrusions and surface irregularities are created that compromise sealing

Engineering Contradiction:

Improvetray shapeVSAvoidsurface smoothness

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The invention extracts the board layer material from compressed portions by thinning or completely removing it in these areas. This extraction allows the plastic coating to double-fold and seal without the obstruction of protruding board material, eliminating surface irregularities while maintaining the desired tray shape.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of creating pleats that protrude outward as in conventional methods, the invention inverts the approach by removing material to allow the coating to fold inward and seal. This inversion transforms the problem of protrusions into a solution where the coating itself forms the sealing surface.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If the board layer is thinned or removed in compressed parts to enable self-sealing, then the plastic coating can double-fold and seal to itself, but the structural integrity of the tray may be compromised

Engineering Contradiction:

Improveself-sealing capabilityVSAvoidtray structural integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The invention relies on the composite structure of plastic-coated board, where the plastic coating serves dual functions: as a barrier layer and as a sealing element. In compressed portions, the coating's ability to melt and seal provides both structural reinforcement and hermetic sealing, compensating for the reduced board layer thickness.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention utilizes phase transition of the plastic coating from solid to melted state during molding, then back to solid upon cooling. This phase transition allows the thin coating to flow into compressed portions, self-seal, and retain the tray's shape, providing structural integrity despite reduced board material in these areas.

Inventive Principle:

Principle #36Phase transitions

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 method ensures a hermetically sealed tray with a thinner plastic coating, eliminating leaks and surface irregularities, and maintains the tray's shape by using heat to melt and seal the coating in transverse compressions.

Implementation Method 1

the blank is compressed in a direction transverse to the tray's side wall and rim flange such that some of the board's plastic coating is melted and flows into the compressions for stabilizing the tray so as to retain its shape

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS8011568B2Method for manufacturing a board tray, a blank for the tray, and a tray obtained by the method

Publication Date: 2011.09.06 STORA ENSO OYJ

AI summary

A board tray, a method for manufacturing a board tray and a tray blank from which the board tray is manufactured, said board tray containing side walls and a bottom wall made of a board layer provided on at least one surface thereof with a plastic coating, wherein areas of reduced thickness are formed in the board layer whereby portions of the plastic layer which have been melted and are disposed adjacent to areas of reduced thickness are compressed into such areas forming double-folded linear plastic compressions which seal on themselves.