Pulp Molded Cap Conical Seal and Partial Threads

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Solution Overview

Problem

There is a challenge in producing recyclable, biodegradable, and compostable screw caps with sufficient quality and strength for reliable sealing, and an efficient process for manufacturing pulp screw caps that are cost-effective and easy to use.

Innovation Solution

A closure system comprising a pulp molded container and cap with conical sealing surfaces and partial threads, where the cap and container have matching angles and thread configurations for a secure seal, and a method for producing pulp caps using a porous tool with a partially threaded surface to apply and dewater pulp slurry, eliminating the need for preform caps and enhancing manufacturing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If screw caps are produced from paper blank material or preform caps, then the caps can be manufactured, but the thread quality and strength are insufficient for reliable sealing

Engineering Contradiction:

Improvethread strengthVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The threading features are incorporated into the mold itself during the initial pulp molding process, rather than adding threads later to preform caps. This preliminary action creates stronger threads since they are formed with the cap structure rather than attached or impressed afterward.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The molding process combines multiple operations into one: forming the cap body, creating the threading features, and establishing the sealing surface all occur simultaneously in a single pulp molding cycle, eliminating separate threading operations and improving both strength and efficiency.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If traditional pulp molding processes are used, then caps can be produced, but the manufacturing efficiency and cost-effectiveness are insufficient

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The molding tool integrates multiple functional surfaces: the first mold surface forms the cap body while the second mold surface simultaneously creates threading features and sealing surfaces. This merging of operations into a single molding step dramatically improves productivity and reduces process complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The process uses controllable dewatering parameters during pulp molding to optimize cap formation and thread quality. By adjusting dewatering rate and pressure, the process achieves high manufacturing efficiency while maintaining cap strength and seal quality.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If caps are designed with full threading, then sealing capability is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvesealing capabilityVSAvoidthread configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention uses partial threading rather than full threading around the entire cap circumference. The threading features are provided only on specific portions of the cap where they are needed for sealing, reducing manufacturing complexity and material usage while maintaining adequate sealing capability through the conical sealing surface geometry.

Inventive Principle:

Principle #16Partial or excessive action

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 solution provides a high-quality, cost-effective, and easy-to-use closure system with a reliable, leakage-proof seal for pulp molded packaging products, improving the strength and manufacturing efficiency of pulp caps.

Implementation Method 1

a first dewatering step, dewatering the pulp slurry layer through the porous product face of the male tool

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

dewatering the pulp slurry layer through the porous product face of the male tool

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS20250091773A1A closure system comprising a pulp molded cap and a pulp molded container, a pulp molded container, a pulp molded cap, a method and a tool for producing a cap or cap part from a pulp slurry

Publication Date: 2025.03.20 CELWISE AB

AI summary

The present disclosure relates to a closure system (100), comprising: a pulp molded container (200) comprising a wall portion (201) which surrounds a product space (2000) presenting a cross-sectional area, wherein said wall portion extends along an axial direction perpendicular to the cross-sectional area, between a first open end (203) and a second end (204) being axially opposite said first open end, wherein a first end wall portion (205) extending from said first open end has a first substantially conical sealing surface (206) presenting a first angle relative to the axial direction; and a pulp molded cap (300) having a second substantially conical scaling surface (306) presenting a second angle relative to the axial direction; wherein the first and second angles substantially match, and wherein one of said first and second substantially conical sealing surfaces (206, 306) presents at least one male partial thread (210) and the other one of said first and second substantially conical sealing surfaces (206, 306) presents at least one corresponding female partial thread (310). The disclosure further relates to a method for producing a cap or cap part from a pulp slurry, and a tool for producing a cap or cap part from a pulp slurry.