Molded Pulp Lid Undercut Formation via Suction Holes

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Solution Overview

Problem

Pulp molded lids struggle to maintain the shape of undercuts when detached from molds, leading to damage and requiring multiple processing steps, which complicates their production and flexibility.

Innovation Solution

Incorporating suction holes in the molds to form convex undercuts during the pulp molding process, allowing for air suction and loosening of the undercut parts before drying, enabling stable detachment without damaging the shape.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If pulp molded lids are formed with undercuts using conventional molding methods, then the lids can be fitted to containers, but the undercut shape is easily damaged during detachment from the mold

Engineering Contradiction:

Improvefitting capabilityVSAvoidundercut shape integrity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by forming the undercut shape in the mold cavity before the pulp dries and hardens. The mold includes a release agent application step prior to molding, and the undercut is formed while the pulp is still pliable, preventing damage during subsequent detachment

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses a release agent as an intermediary substance between the mold surface and the pulp molded lid. This release agent prevents adhesion between the pulp and mold during the molding process, allowing easy detachment without damaging the undercut shape

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If pulp molded lids are formed with undercuts in a single step, then production efficiency improves, but the undercut shape is easily damaged making multiple steps necessary

Engineering Contradiction:

Improveproduction efficiencyVSAvoidundercut shape stability

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The undercut shape is formed in advance during the initial molding step while the pulp is still pliable. The mold cavity is designed with the undercut geometry, and the pulp is molded into this shape before drying and hardening, eliminating the need for subsequent secondary processing steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A release agent is applied to the mold cavity before molding to prevent adhesion. This intermediary substance allows the molded lid with undercut features to be detached from the mold in a single step without damaging the shape, thereby improving productivity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If plastic lids are used instead of pulp molded lids, then flexibility and ease of forming undercuts improve, but environmental compatibility with paper cups deteriorates

Engineering Contradiction:

Improvematerial flexibilityVSAvoidenvironmental compatibility

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the physical parameters of the pulp material during processing - starting with pliable wet pulp that can be molded into complex undercut shapes, then drying and hardening it to achieve the desired final properties. This allows pulp to exhibit plastic-like formability during molding while maintaining environmental compatibility

Inventive Principle:

Principle #35Parameter changes

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 the stable production of pulp molded lids with undercuts, reducing processing complexity and cost, while maintaining the environmental benefits of pulp molding, and enabling easy fitting and detachment without damaging the undercut features.

Implementation Method 1

one or more suction holes at a level corresponding to a level of the undercut part to be formed on an inner surface of the side wall

Methodology Applied

Scientific EffectSuction: Suction

Implementation Method 2

blowing air outward from the suction holes after heating and drying the lid to loosen the undercut part

Methodology Applied

Scientific EffectPressure increase: Pressure Increase

Implementation Method 3

a state that is under heating and drying, and a state that is immediately before being released

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS11466410B2Lid, method of producing lid, and molds for forming molded pulp

Publication Date: 2022.10.11 TOPPAN INC

AI summary

A method of producing a lid including a top plate and a side wall extending downward from a periphery of the top plate, using molds, the molds including a papermaking mold and a drying mold. The top plate is provided with an abutting part abutting against an edge of an opening of a container, while an undercut part to be fitted to a lower part of the edge is formed on the side wall so as to be located below the abutting part. The papermaking mold is provided with suction holes at a level corresponding to a level of the undercut part formed on an inner surface of the side wall. The side wall is suctioned using the suction holes when a molded article is at least in one of several states to form the undercut part in a convex shape on the inner surface of the side wall.