Drop Generator With Low-Q Stimulation Chamber

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Solution Overview

Problem

Existing printing heads for continuous inkjet printers face challenges in generating individual drops without parasitic drops, achieving sharp cut-off frequency, and manufacturing cavities of larger sizes to supply multiple jets.

Innovation Solution

A drop generator with a stimulation chamber having a quality factor Q lower than 2, equipped with a piezoelectric actuator, and a nozzle for ejecting jets, along with a layer of Kapton or annealed stainless steel to dampen oscillations, allowing for the generation of individual drops with controlled cut-off frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the quality factor Q of the stimulation chamber is reduced to lower than 2, then parasitic drop formation is reduced and cut-off sharpness is improved, but the resonant frequency range is narrowed

Engineering Contradiction:

Improvecut-off sharpnessVSAvoidresonant frequency range

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies parameter changes by deliberately setting the quality factor Q to be lower than 2, which fundamentally alters the resonance characteristics of the stimulation chamber. This parameter modification enables sharper cut-off frequencies and reduces parasitic drops while accepting a narrower resonant frequency range as a trade-off.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the typically harmful effect of resonance into a beneficial feature by utilizing the resonant frequency of the stimulation chamber to enhance drop formation precision. By controlling the quality factor to be less than 2, the resonance is harnessed to create sharp cut-off frequencies that prevent parasitic drops, transforming what could be a source of instability into a precision control mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Adaptability or versatility

If the cavity size is increased to supply multiple jets, then jet supply capability is improved, but manufacturing difficulty increases

Engineering Contradiction:

Improvejet supply capabilityVSAvoidmanufacturing difficulty

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent applies segmentation by dividing the stimulation chamber into multiple independent cavities, each capable of supplying a separate jet. This modular approach allows the system to supply multiple jets while maintaining manageable manufacturing complexity for each individual cavity unit, which can be produced using standard fabrication processes.

Inventive Principle:

Principle #1Segmentation

3Productivity

If stimulation means are activated to generate jets, then drop formation is achieved, but parasitic signals and rebounds are generated causing noise in neighbouring cavities

Engineering Contradiction:

Improvedrop formation efficiencyVSAvoidparasitic signals

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful parasitic signals and rebounds into beneficial effects by utilizing the low quality factor (Q < 2) characteristic to dampen these unwanted oscillations. The same resonance control that enables sharp cut-off frequencies also suppresses parasitic signals, transforming the harmful rebounds into a damping mechanism that reduces noise in neighbouring cavities.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces the stimulation chamber's resonance characteristics as an intermediary mechanism that mediates between the stimulation signal and the final drop formation. This intermediary system filters out parasitic signals and rebounds through its controlled low quality factor, allowing clean drop formation while preventing noise propagation to neighbouring cavities.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively reduces parasitic drop formation, achieves a sharp cut-off frequency, and enables the manufacturing of larger cavities, improving the efficiency and precision of drop generation in continuous inkjet printers.

Implementation Method 1

stimulation means (or actuator, for example piezoelectric means or a piezoelectric crystal), for stimulating a wall of said stimulation chamber

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a layer, for example of Kapton, which dampens the oscillations of the stimulation means transmitted to the cavity

Methodology Applied

Scientific EffectDamping: Damping

Implementation Method 3

the transfer function of the stimulation system is preferably free of resonance peaks in the pass band of the jet

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentEP3880478B1Drop formation method and device using a cavity with a degraded quality factor

Publication Date: 2025.04.02 DOVER EUROPE SARL

Figure 1~2A
Figure 2B~3
Figure 4A~4C

AI summary

The invention relates to a drop generator for a printing head of a continuous inkjet printer, including: - at least one ink feed conduit (28) for feeding ink into a stimulation chamber (38), which has a quality factor Q lower than 2 and at least one resonant frequency fr; - stimulation means (34, 35, 35a) for stimulating a wall of said stimulation chamber (38); - at least one nozzle (4) for ejecting a jet (40).