Retractable Marking Pen Ink Retention via Organic Solvent

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Solution Overview

Problem

Retractable marking pens without caps face issues of ink splattering and pen core protrusion due to low viscosity ink and existing opening/closing mechanisms increasing part count and click stroke length.

Innovation Solution

Incorporating a water-soluble organic solvent in the ink composition to enhance ink retention, adding urea for film formation, positioning the pen core rearward of the opening, and using an asymmetrical shaft cylinder with a clip to reduce impact-induced ink splattering and protrusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an opening/closing mechanism is provided to close the opening part when the pen core is retracted, then ink splattering is prevented, but the number of parts increases and the click stroke lengthens

Engineering Contradiction:

Improveink splattering preventionVSAvoidnumber of parts

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the chemical composition parameters of the ink by adding a water-soluble organic solvent (20-60 mass%) to create an ink composition with enhanced affinity for the inner cotton. This parameter change allows the ink to be retained effectively without requiring an opening/closing mechanism, thus preventing ink splattering while maintaining device simplicity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses the asymmetrical shaft cylinder design that creates an unstable landing orientation, effectively making the protective function temporary and orientation-dependent rather than requiring a permanent mechanical closing mechanism. This approach prevents ink splattering during normal use while avoiding additional parts

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If an opening/closing mechanism is provided to close the opening part when the pen core is retracted, then ink splattering is prevented, but the click stroke lengthens

Engineering Contradiction:

Improveink splattering preventionVSAvoidclick stroke

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent modifies the ink composition parameters by incorporating a water-soluble organic solvent to enhance ink retention properties. This allows the pen core to remain effectively closed without mechanical intervention, preventing ink splattering while maintaining the original click stroke length

Inventive Principle:

Principle #35Parameter changes

3Length of moving object

If the pen core is positioned closer to the opening part, then the click stroke is shortened, but the tip end may protrude from the opening part during impact

Engineering Contradiction:

Improveclick strokeVSAvoidpen core protrusion prevention

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The patent employs an asymmetrical shaft cylinder design where the center of gravity is positioned away from the geometric center. This creates an unstable landing orientation that prevents the pen from landing tip-first, thereby preventing pen core protrusion during impact while allowing the pen core to be positioned closer to the opening for a shorter click stroke

Inventive Principle:

Principle #4Asymmetry

4Reliability

If a water soluble organic solvent is added to increase ink affinity with inner cotton, then ink retention improves, but ink viscosity may increase

Engineering Contradiction:

Improveink retentionVSAvoidink viscosity

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent carefully controls the concentration parameters of the water-soluble organic solvent within the range of 20-60 mass% to optimize the balance between ink affinity and viscosity. This parameter optimization ensures sufficient ink retention while maintaining appropriate ink flow characteristics for normal pen operation

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

Prevents ink splattering and pen core protrusion without additional mechanisms, maintaining functionality and reducing part count.

Implementation Method 1

the affinity between the aqueous ink composition and the inner cotton is increased. Due to the increase of the affinity between the aqueous ink and the inner cotton, the force by which the inner cotton retains the aqueous ink composition increases

Methodology Applied

Scientific EffectAffinity: Absorption (physical)

Implementation Method 2

the aqueous ink composition contains urea in an amount from 1 mass % to 30 mass %. Due thereto, a film-like matter is formed at the tip end of the pen core and prevents dirtying due to the adhesion of ink

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Implementation Method 3

an inner cotton that is accommodated in a shaft cylinder and is filled with an aqueous ink to be fed to a porous pen core by means of capillarity

Methodology Applied

Scientific EffectCapillarity: Capillary Action

Data Source

PatentUS11987068B2Marking pen

Publication Date: 2024.05.21 MITSUBISHI PENCIL CO LTD

AI summary

A marking pen, comprising: a shaft cylinder; a porous pen core accommodated in the shaft cylinder, and configured to project from, and retract into, an opening part provided at a tip end of the shaft cylinder; an inner cotton accommodated in the shaft cylinder, and filled with an aqueous ink composition to be fed to the pen core, the aqueous ink composition including a water soluble organic solvent in an amount of from 20 mass % to 60 mass %; and a delivery mechanism configured to cause a tip end of the pen core to project from, and retract into, the opening part.