Liquid Ejecting Head Air Bubble Discharge via Segmented Flow Path

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Solution Overview

Problem

Existing ink-jet heads with multiple filters face challenges in effectively discharging air bubbles during purging operations, leading to increased ink wastage and potential printing performance issues due to pressure loss and the need for higher pump output.

Innovation Solution

The design incorporates a liquid ejecting head with a first flow-passage member, branch passages, discharge passages, a second flow-passage member with individual passages and pressure chambers, and multiple filters, where the discharge passages are connected to branch passages downstream of the first filter, allowing effective air bubble discharge without excessive ink wastage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If two different kinds of filters are disposed in the liquid ejecting head to improve filtration, then filtering performance is improved, but pressure loss increases and air bubbles cannot be sufficiently discharged

Engineering Contradiction:

Improvefiltration performanceVSAvoidpressure loss

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The flow passage is segmented into multiple regions with filters disposed at different locations (first filter in liquid supply passage, second filter at boundary between reservoir unit and head main body). This segmentation allows each filter to serve specific filtration needs while maintaining adequate pressure distribution throughout the system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different filter mesh sizes are used at different locations: a first filter with a first mesh size in the liquid supply passage and a second filter with a second mesh size at the boundary between reservoir unit and head main body. This local differentiation optimizes filtration performance at each stage while managing pressure loss.

Inventive Principle:

Principle #3Local quality

2Reliability

If pump output is increased to discharge air bubbles through two filters, then air bubble discharge is improved, but ink wastage increases

Engineering Contradiction:

Improveair bubble dischargeVSAvoidink wastage

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

Discharge passages are provided in the reservoir unit that connect to the liquid supply passage upstream of the filters. This preliminary discharge path allows air bubbles to be removed before they reach the filters and cause pressure loss, enabling effective purging at normal pump output levels without excessive ink wastage.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If discharge passage is connected upstream of filter to enable air bubble discharge, then air bubble removal is improved, but liquid supply control becomes complex

Engineering Contradiction:

Improveair bubble dischargeVSAvoidflow passage configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The liquid supply passage serves multiple functions: it supplies liquid to the filters for filtration and simultaneously provides a discharge path for air bubbles through the discharge passages connected to it. This multi-functionality simplifies the overall structure compared to having separate discharge passages throughout the system.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration enables efficient air bubble removal through the discharge passages while maintaining normal pump output levels, reducing ink wastage and preventing printing performance deterioration.

Implementation Method 1

air bubbles staying between the filter and a branch point at which the discharge passage is branched from the upper reservoir are forcibly discharged to an outside of the reservoir unit from the discharge port through the discharge passage, by conducting a pressure purging operation in which ink is supplied to the reservoir unit using a pump

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

a first filter disposed in the liquid-supply passage; a plurality of second filters disposed between the plurality of branch passages and the at least one common liquid passage

Methodology Applied

Scientific EffectFiltration: Filter (physical)

Data Source

PatentUS8205978B2Liquid ejecting head for effectively discharging air bubbles

Publication Date: 2012.06.26 BROTHER KOGYO KK

AI summary

A head for ejecting a liquid from ejection holes, including: a first flow-passage member in which are formed (a) a liquid-supply passage, (b) branch passages connected to the liquid-supply passage, and (c) discharge passages each being connected to any of the branch passages; a second flow-passage member in which are formed (a) at least one common passage each communicating with at least one of the branch passages and (b) individual passages having respective pressure chambers, each individual passage being connected to any one of the at least one common passage and introducing the liquid to a corresponding one of the ejection holes via a corresponding one of the pressure chambers; a first filter disposed in the liquid-supply passage; second filters disposed between the branch passages and the at least one common passage: and at least one energy giving member for giving ejection energy to the liquid in each pressure chamber.