Ink Circulation Buffering for Stable White Ink Replenishment

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Solution Overview

Problem

Ink replenishment in printing apparatuses can cause fluctuations in ink temperature and density distribution, leading to unstable ink properties and reduced print quality, particularly with white ink.

Innovation Solution

Implementing a circulation system with dedicated circulation paths and controlled replenishment processes to maintain stable ink temperature and prevent pigment precipitation, using sub-tanks, pumps, and sensors to manage ink flow and replenishment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If ink is replenished from the main tank to the head unit, then the ink supply is maintained, but the ink temperature fluctuates and becomes unstable

Engineering Contradiction:
Improveink supplyVSAvoidink temperature stability
Core Design Contradiction:
Quantity of substanceVSTemperature

Solution Approach 1:

The ink storage system is divided into two separate tanks: a main tank for bulk storage and a sub-tank for active supply to the head unit. This segmentation allows the main tank to store ink at stable conditions while the sub-tank receives controlled replenishment, isolating temperature fluctuations to the sub-tank only and preventing them from affecting the entire system.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The sub-tank acts as an intermediary between the main tank and the head unit. It receives ink from the main tank through a controlled replenishment process and supplies it to the head unit, buffering temperature variations and ensuring stable ink delivery to the printing head.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Use of energy by moving object

If ink stands still in the drum tank and pipe during non-replenishment time, then energy consumption is reduced, but pigments precipitate and generate ink density distribution

Engineering Contradiction:
Improveenergy consumptionVSAvoidink density uniformity
Core Design Contradiction:
Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

Instead of continuous circulation, the system employs periodic circulation of ink in the sub-tank. The circulation is activated at specific intervals or under specific conditions to prevent pigment precipitation, then stopped to conserve energy. This periodic action maintains ink uniformity while minimizing energy consumption compared to continuous circulation.

Inventive Principle:
Principle #19Periodic action

3Stability of the object's composition

If continuous circulation of ink is maintained, then ink density uniformity is preserved, but energy consumption increases

Engineering Contradiction:
Improveink density uniformityVSAvoidenergy consumption
Core Design Contradiction:
Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The system uses periodic circulation instead of continuous circulation to maintain ink density uniformity. The circulation is activated only when needed to prevent pigment precipitation, then stopped to conserve energy, achieving a balance between maintaining composition stability and reducing energy consumption.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The circulation system is designed to activate automatically based on detected conditions (such as ink stagnation or temperature variations). The system monitors itself and initiates circulation only when necessary to maintain ink uniformity, eliminating the need for continuous energy-consuming operation while preserving ink quality.

Inventive Principle:
Principle #25Self-service

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

Stabilizes ink properties during replenishment, ensuring high-quality printing by maintaining consistent ink temperature and density, thereby preventing reductions in print quality.

Implementation Method 1

a circulation pump for circulating the ink from the collection sub-tank to the supply sub-tank

Methodology Applied
Scientific EffectPump: Pump

Implementation Method 2

A negative pressure in the collection tank is set to be larger than that in the supply tank, and the ink is circulated inside a head unit due to this pressure difference

Methodology Applied
Scientific EffectPressure difference: Pressure Gradient

Implementation Method 3

implementing a circulation system with dedicated circulation paths and controlled replenishment processes to maintain stable ink temperature

Methodology Applied
Scientific EffectThermal convection: Convection

Implementation Method 4

prevent pigment precipitation, using sub-tanks, pumps, and sensors to manage ink flow and replenishment

Methodology Applied
Scientific EffectSedimentation prevention: Suspension

Data Source

PatentEP4357144B1Printing apparatus and printing method
Publication Date: 2026.03.25 SCREEN HOLDINGS CO LTD
  • EP4357144B1 patent drawingFigure 1
  • EP4357144B1 patent drawingFigure 2A
  • EP4357144B1 patent drawingFigure 2B

AI summary

An ink is circulated in a circulation path including a supply sub-tank, a discharge head and a collection sub-tank in a head unit. If the amount of the ink in the head unit decreases, the ink stored in the buffer tank is replenished to the head unit. On the other hand, in a first non-replenishment time during which the ink is not replenished, the ink is circulated through the buffer tank, the collection sub-tank and the supply sub-tank in this order. Thus, a temperature fluctuation of the replenishment ink stored in the buffer tank is suppressed. As a result, even if the ink is replenished to the head unit from the buffer tank, physical properties, particularly a viscosity, of the ink do not largely vary.